Search

Coastal (CTR) and inland temperate rainforests (ITR) in western North America share a rich oceanic lichen flora. The distinctive Methuselah's beard lichen (Usnea longissima Ach.) is an exception to this pattern of shared distributions, with very few ITR locations. Does this absence reflect dispersal limitations or climatic intolerance? To answer this question, we transplanted U. longissima thalli from the CTR to three ITR locations, assessing growth rates against reciprocal CTR transplants. Canopy microclimate measurements provided concurrent data on growth conditions. Growth rate responses (length, mass, and area) were evaluated after summer and full-year transplants. Notwithstanding extended drought conditions during the summer period, annual transplants at two of the three ITR locations supported growth rates comparable to those at the CTR source U. longissima population, with summer dewfall and autumn rains being major ITR hydration sources. Thalli transplanted to a third ITR site (summer measurements only) in a location transitional to the drier interior plateau lost both mass and length. Based on these findings, we suggest that the absence of U. longissima from much of the ITR reflects the combined influence of dispersal limitations and requirements for stands with long site continuity and topographically induced summer wetting of thalli by dewfall. Key words: temperate rainforest, lichen biogeography, old-growth forest, lichen growth, transplant, occult precipitation. Les forêts pluviales tempérées côtières (FPTC) et intérieures (FPTI) de l'ouest de l'Amérique du Nord partagent une riche flore de lichens océaniques. Le lichen particulier qu'est la barbe de Mathusalem (Usnea longissima Ach.) est une exception à ce modèle de distributions partagées, avec très peu de sites dans les FPTI. Cette absence reflète-t-elle des limitations de dispersion ou une intolérance climatique? Pour répondre à cette question, les auteurs ont transplanté des thalles d'U. longissima de FPTC sur trois sites dans une FPTI, évaluant les taux de croissance par rapport aux transplantations réciproques dans une FPTC. Les mesures du microclimat de la canopée ont fourni des données simultanées sur les conditions de croissance. Les réponses en matière de taux de croissance (longueur, masse et surface) ont été évaluées après les transplantations en été et toute l'année. En dépit des conditions de sécheresse prolongée pendant la période estivale, les transplantations annuelles à deux des trois emplacements de la FPTI soutenaient des taux de croissance comparables à ceux de la population source d'U. longissima de la FPTC, la rosée d'été et les pluies d'automne étant les principales sources d'hydratation des FPTI. Les thalles transplantés sur un troisième site dans la FPTI (mesures en été uniquement) dans un lieu de transition vers le plateau intérieur plus sec ont perdu à la fois de la masse et de la longueur. Sur la base de ces résultats, les auteurs suggèrent que l'absence d'U. longissima dans une grande partie de la FPTI reflète l'influence combinée des limitations de la dispersion et des exigences pour des peuplements ayant une longue continuité de sites, ainsi que l'humidification estivale des thalles par la rosée induite par la topographie. [Traduit par la Rédaction] Mots-clés : forêt pluviale tempérée, biogéographie des lichens, forêt ancienne, croissance des lichens, transplantation, précipitations occultes., Introduction Coastal temperate rainforest (CTR) ecosystems in western North America represent a globally significant repository for oceanic lichens (Goward and Spribille 2005; Spribille et al. 2010; DellaSala et al. 2011a), [...]

The conditions faced by edge populations of a tree species may affect the architecture of individual trees. The latitudinally broad range of Salix humboldtiana Willd. encompasses tropical to cold-temperate climatic regions, with its southernmost population in central Patagonia. We expected S. humboldtiana trees from the southern-edge population to develop smaller shoots and a lower level of axis differentiation than trees of this species from a more northern population, and we expected edge trees to outperform non-edge trees when growing in a common garden at an intermediate latitude. For juvenile individuals of S. humboldtiana from edge and non-edge natural populations, the trunk diameter, height, branching angle, as well as the length, number of nodes, diameter, leaf area, and specific leaf area of the main branch and the trunk annual shoots were measured. The size and extension rates of shoots developed by trees of both origins in a common garden were also evaluated. In natural populations, the shoot leaf area and the specific leaf area were higher for the edge population than for the non-edge population. In a common garden, the shoot extension period and the length were higher for non-edge plants than for edge plants. The growth-period differences between populations in a common garden may support the hypothesis of stress adaptation in the southernmost S. humboldtiana trees. Key words: annual shoots, range limit, stressful conditions, plant architecture, Salix. Les conditions auxquelles sont confrontées les populations d'uneespèced'arbre situées en bordure peuvent affecter l'architecture des arbres individuels. L'aire de répartition latitudinale de Salix humboldtiana Willd. englobe des régions climatiques tropicales à tempérées froides, avec sa population la plus méridionale en Patagonie centrale. Les auteurs s'attendaient à ce que les arbres de l'espèce S. humboldtiana provenant de la population en bordure sud développent des pousses plus petites et un niveau de différenciation des axes plus faible que les arbres de cette espèce provenant d'une population plus au nord, et ils s'attendaient à ce que les arbres en bordure soient plus performants que les arbres n'étant pas en bordure lorsqu'ils poussent dans un jardin commun à une latitude intermédiaire. Pour les individus juvéniles de S. humboldtiana provenant de populations naturelles en bordure ou non, le diamètre du tronc, la hauteur, l'anglederamification, et la longueur, le nombredenoeuds, le diamètre, la surface foliaire et la surface foliaire spécifiquedela branche principale et des pousses annuelles du tronc ont été mesurés. La taille et les taux d'extension des pousses développées par les arbres des deux origines dans un jardin commun ont également été évalués. Dans les populations naturelles, la surface foliaire des pousses et la surface foliaire spécifique étaient plus élevées pour la population en bordure que pour la population non située en bordure. Dans le jardin commun, la période d'extension des pousses et leur longueur étaient plus élevées pour les plantes non situées en bordure que pour les plantes de bordure. Les différences de période de croissance entre les populations dans le jardin commun peuvent soutenir l'hypothèse d'une adaptation au stress chez les arbres de l'espèce S. humboldtiana les plus au sud. [Traduit par la Rédaction] Mots-clés : pousses annuelles, limite d'aire de répartition, conditions stressantes, architecture végétale, Salix., Introduction The edges of a species' range may be determined by physical barriers to the dispersion of the species, or by unbearably stressful conditions, e.g., water availability, temperature, or soil [...]

Abstract: The flora of the Hawaiian Islands has one of the highest rates of endemism in the world, and over half of all taxa are at risk of endangerment or [...]

Abstract--A simulation model was developed to assess the long-term influence of seed removal and nest patch construction by red harvester ants (Pogonomyrmex barbatus F. Smith) on three grass species common [...]

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1365-2745.2010.01711.x Byline: Lander Baeten (1), Martin Hermy (2), Sander Van Daele (1), Kris Verheyen (1) Keywords: ancient forest; biodiversity balance; community drift; disturbance; forest herbs; land-use history; plant population and community dynamics; secondary forest succession; semi-permanent plots Abstract: Summary 1. Land-use change is considered one of the most radical and extensive disturbances that have influenced plant distributions and diversity patterns in forest understorey communities in much of Europe and eastern North America. In forests growing on former agricultural land, local species diversity and community differentiation among sites are generally reduced compared with ancient forests (i.e. forests with no historical record of agriculture). Yet, no study has determined how the compositional differences created by former land-use change over time as the forest sites recover from former agricultural use. 2. Here, we resurveyed 78 vegetation plots (half of the plots in ancient and half in post-agricultural forest) to demonstrate how three decades of forest development have changed the compositional differences between post-agricultural and ancient forest sites. The impact of land-use history and survey date was tested on two measures of species diversity and two measure of community divergence. 3. The data indicate that the imprint of former agricultural land use persisted over time, yet not through compositional stability. Parallel and strong vegetation shifts occurred in both ancient and post-agricultural forest: the species diversity decreased and local species cover strongly diverged, which indicates community drift. The observed understorey changes did thus not support the commonly accepted model of community development in post-agricultural forests, i.e. the diversity did not increase and the vegetation did not become more similar to the ancient forest vegetation over time. The changes in species composition were associated with an increase of common, competitive species at the expense of ancient forest indicator species. The source populations of ancient forest species have been gradually depleted, so the recovery of post-agricultural forests becomes even more precarious. 4. Synthesis. While land-use history is likely to persist as the primary predictor of local species diversity and community divergence, other environmental drivers may additionally structure forest understorey communities and lead to biotic impoverishment and pervasive species reordering on the time scale of only decades. Author Affiliation: (1)Laboratory of Forestry, Department of Forest and Water Management, Ghent University, Geraardsbergsesteenweg 267, BE-9090 Gontrode (Melle), Belgium (2)Division of Forest, Nature and Landscape, Department of Earth and Environmental Sciences, K.U.Leuven, Celestijnenlaan 200E, BE-3001 Leuven, Belgium Article History: Received 1 April 2010; accepted 7 July 2010 Handling Editor: Lorena Gomez-Aparicio Article note: *Correspondence author. E-mail: lander.baeten@ugent.be

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1600-0706.2010.18232.x Byline: Beatriz Pias, Silvia Matesanz, Amaya Herrero, Teresa E. Gimeno, Adrian Escudero, Fernando Valladares Abstract: Plant populations are subjected to changes in their natural environment as a result of the incidence of simultaneous global change drivers. Despite the fact that these changes can largely affect early fitness components, information on the effects of simultaneous drivers of global change on offspring traits and performance is particularly scant. We analyzed the combined effect of three global change drivers of critical importance in Mediterranean ecosystems (habitat fragmentation, reductions in habitat quality and water availability) on germination and seedling performance of the gypsophile shrub Centaurea hyssopifolia. Seedlings from 39 mother plants from eight different environments (resulting from the combination of the three global change drivers) were sown and grown in a common garden. First, germination percentage, seedling size and seedling survival were monitored. Secondly, seedling performance and ecophysiological traits were measured under well and low-watered conditions. Fragmentation showed the largest negative effect on germination and offspring performance. Seedlings of mothers from small fragments germinated more slowly, showed lower survival, died faster, and showed lower photosynthetic rates under well-watered conditions compared to seedlings of mother plants from large populations. Seedlings of different maternal origins did not differ in their response to water stress or in their ability to survive to drought. Ninety-five percent of the seedlings survived until soil water content was as low as 3%. Our study shows that global change can have not only immediate impacts on plant populations but also transgenerational effects, and highlights the importance of studies involving multiple drivers and a more integral understanding of global change. Author Affiliation: (1)Laboratorio Internacional de Cambio Global (LINC-Global), Inst. de Recursos Naturales, CCMA-CSIC, c/ Serrano 115. dpdo, ES-28006, Madrid, Spain (2)Biology Dept, Wesleyan Univ., Middletown, CT 06459, USA (3)Depto de Biologia y Geologia, Univ. Rey Juan Carlos, c/ Tulipan s/n, ES-28933 Mostoles, Spain Article History: Paper manuscript accepted 15 January 2010 Article note: B. Pias, Laboratorio Internacional de Cambio Global (LINC-Global), Inst. de Recursos Naturales, CCMA-CSIC, c/ Serrano 115. dpdo, ES-28006, Madrid, Spain. E-mail: beapias@ccma.csic.es

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1365-2745.2010.01697.x Byline: Hans Jacquemyn (1), Rein Brys (2), Eelke Jongejans (3) Keywords: cost of reproduction; flowering; integral projection model; plant population and community dynamics; orchids; Orchis purpurea Abstract: Summary 1. In woodland herbs, the probability of flowering and costs associated with reproduction may strongly depend on environmental context (shade vs. light habitats) and on plant size. This may be particularly true for tuberous orchids that inhabit woodlands, as the amount of incoming radiation and total leaf area strongly determine photosynthetic capacity and hence the amount of carbohydrates that can be relocated to below-ground storage organs that form next year's rosette and flowering stalk. 2. To fully comprehend the impact of size-dependent reproduction on population dynamics under varying light conditions, life cycle models should therefore include plant size in a continuous manner. In this study, annual changes in plant size and demographic behaviour of the tuberous perennial orchid Orchis purpurea were monitored during seven consecutive years (2003-2009) in open and shaded woodland. Integral projection models (IPMs) and life table response experiments (LTRE) were used to investigate the extent to which variation in plant size affected the overall population dynamics of this species and to decompose differences in population growth rates between populations of open and shaded woodland into contributions from growth, survival and reproduction. 3. Both plants in shaded and light environments needed to be a certain size to initiate flowering, but this threshold size was almost three times as large in shaded environments as in light environments. Plants in open woodlands flowered more frequently over the years, showed less size regression after flowering and produced significantly more fruits than plants in shaded environments, resulting in significantly larger population growth rates. 4. Our life cycle models revealed that costs of reproduction, measured at the population-level, were small in the light environment, and more than buffered by the increase in survival of flowering plants compared to non-flowering plants. In the shade environment, however, the costs of reproduction were significant and made the difference between a stable (current) and a growing (without reproduction costs) population. 5. Synthesis. Light penetration to the soil is a key variable determining population dynamics of woodland orchids. Our analyses show that differences in vital rates related to size-dependent reproduction (flowering) and growth are essential drivers of changes in orchid population dynamics in different light environments. The combination of IPMs and LTREs thus proves to be very useful when studying the fitness consequences of size- and context-dependent phenomena like flowering strategies and costs of reproduction. Author Affiliation: (1)Division of Plant Ecology and Systematics, University of Leuven, Arenbergpark 31, B-3001 Heverlee, Belgium (2)Research Institute for Nature and Forest, Kliniekstraat 25, B-1070 Brussels, Belgium (3)Department of Experimental Plant Ecology, Institute for Water and Wetlands Research, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands Article History: Received 25 March 2010; accepted 08 June 2010 Handling Editor: Mark Rees Article note: (*) Correspondence author. E-mail: hans.jacquemyn@bio.kuleuven.be

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1365-2745.2010.01639.x Byline: Knut Rydgren (1), Rune Halvorsen (2), Nils Cronberg (3) Keywords: bryophytes; clonality; cost of reproduction; Hylocomium splendens; linear two-sex model; matrix model; population growth rate; sex-ratio dynamics; sporophyte frequency Abstract: Summary 1. Sex ratios in unisexual bryophytes are most often female biased, whereas male-biased sex ratios predominate in unisexual seed plants. This 'bryophyte paradox', i.e. that sex ratios are biased in favour of the sex associated with the highest reproductive costs, has remained unexplained. 2. Analysis of sex-ratio patterns via the influence of sex distribution on population growth rates ([lambda]) has not previously been carried out for bryophytes. We used this method to model how variation in sex ratio and sporophyte frequency influences [lambda] in the clonal bryophyte Hylocomium splendens. We obtained [lambda] by matrix modelling of synthetic experimental populations derived from demographic field data, using a linear two-sex model. 3. In our set of experimental populations [lambda] varied between 1.13 and 1.27 in response to variation in sex ratio and sporophyte frequency, with the highest [lambda] obtained for the combination of a very low sporophyte frequency and a slightly female-biased sex ratio. 4. Our results explain the female-biased sex ratio of H. splendens by the slightly lower survival of and production of vegetative offspring by males than by non-sporophytic females. 5. Synthesis. According to our models, female dominance is the predicted outcome of low to moderate fertilization success and male performance intermediate between that of sporophytic and of non-sporophytic females. Our results therefore explain how a female-biased sex ratio can be maintained despite higher costs of reproduction in females than in males. In dioecious bryophytes, males and females must grow in close contact for fertilization to take place. Better performance of male ramets than of the female ramets they fertilize also explains how male clones can expand into female clones. A similar performance hierarchy of males and females may occur in unisexual clonal seed plants, but more efficient fertilization systems by pollination prevents the selective advantage of unfertilized females from being realized. This explains why vascular plant populations tend to be male biased. We hypothesise difference in fertilization distance range between sperm and pollen as a simple explanation why ramet level sex ratios are in general male dominated in clonal seed plants and female dominated in clonal bryophytes. Author Affiliation: (1)Sogn og Fjordane University College, Faculty of Science, PO Box. 133, N-6851 Sogndal, Norway (2)Section of Botany, Natural History Museum, University of Oslo, PO Box 1172 Blindern, N-0318 Oslo, Norway (3)Plant Ecology and Systematics, Lund University, Ecology Building, SE-223 62 Lund, Sweden Article History: Received 27 August 2009; accepted 7 January 2010 Handling Editor: David Gibson Article note: (*) Correspondence author. E-mail: knut.rydgren@hisf.no

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1365-2745.2009.01635.x Byline: Roberto Salguero-Gomez (1), Hans de Kroon (2) Keywords: demographic buffering; integral projection model; plant demography; population dynamics; projection matrix; stochastic elasticity; stochastic life table response experiment (SLTRE); transient dynamics Abstract: Summary 1. Projection matrices have become the dominant modelling approach in plant demography because they (i) are relatively easy to formulate, (ii) compile complex data in a structured and analytically tractable manner, (iii) provide numerous parameters with direct biological meaning, (iv) allow the investigator to address broad or specific, experimental and/or theoretical, ecological and evolutionary questions, and (v) produce uniform outputs, enabling direct comparisons between the results of different studies. 2. The last decade has witnessed major advancements in this field that have brought demographic models much closer to the real world, in particular in the analysis of effects of spatial and temporal environmental variation on populations. The present Special Feature contributes to that progress with novel methodologies and applications on Integral Projection Models, stochastic Life Table Response Experiment analyses, stochastic elasticities, transient dynamics and phylogenetic analyses. 3.Synthesis. Environmental stochasticity is an integral part of ecosystems, and plant populations exhibit a tremendous array of demographic strategies to deal with its effects. The analytical challenge of understanding how populations avoid, tolerate or depend on stochasticity is finally overcome with the new matrix approaches. The tools are now available to interpret the effects of changes in temporal and spatial variation on plant populations. Author Affiliation: (1)Department of Biology, University of Pennsylvania, 215 South University Avenue, 321 Leidy Laboratories, Philadelphia, PA 19104, USA (2)Department of Experimental Plant Ecology, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands Article History: Received 3 December 2009; accepted 9 December 2009 Handling Editor: Michael Hutchings Article note: (*) Correspondence author. E-mail: salguero@sas.upenn.edu

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1365-2745.2009.01617.x Byline: John L. Maron (1), Carol C. Horvitz (2), Jennifer L. Williams (3) Keywords: Calathea ovandensis; Cynoglossum officinale; interaction strength; matrix model; plant population growth; plant-herbivore interactions; transient dynamics Abstract: Summary 1. Despite a large literature documenting the effects of mutualists and/or antagonists on plant performance, we still have limited insight into the strength of these interactions, as this involves quantifying how one species influences the population dynamics of another. 2. Here, we use data from two example systems, Cynoglossum officinale and Calathea ovandensis, to illustrate how experiments, demographic data and stage-based population models can be combined to estimate interaction strength of insect herbivores on plants. Because many plant populations may not be at equilibrium, we conduct transient analyses and contrast these results to more traditional asymptotic results. 3. We calculate three metrics of interaction strength, [DELTA][lambda].sub.asymptotic, the change in asymptotic annual per capita plant population growth rate resulting from herbivore exclusion, [DELTA][lambda](t), the change in transient [lambda] caused by herbivores at t = M (where M = the time of their maximum effect during the transient phase) and [DELTA][lambda].sub.transient, a time-averaged effect of consumers on [lambda] across the entire transient phase. 4. Fairly strong impacts of insect consumers on plant fecundity do not translate similarly to [DELTA][lambda].sub.asymptotic. Results show that [DELTA][lambda](t) can be larger (or smaller) than [DELTA][lambda].sub.asymptotic but in our examples [DELTA][lambda].sub.transient was similar in magnitude to [DELTA][lambda].sub.asymptotic. 5. The transient effects of consumers on [lambda] were driven by changes in the elasticity of fecundity across the transient phase. These effects were dynamic even though consumer impacts on demography and vital rates were held constant. The importance of particular stages and transitions to annual population growth vary during the transient phase. 6.Synthesis. We describe three metrics of interaction strength, [DELTA][lambda].sub.asymptotic, [DELTA][lambda](t) and [DELTA][lambda].sub.transient. These metrics have several advantages over more commonly used trait or performance measures that quantify the outcome of interactions. We illustrate how the transient impacts of consumers on [lambda] are dynamic, with the changing stage distribution of a population and transient elasticities driving these effects. More generally, this study shows that the impacts of animals on plant performance do not translate equivalently to plant population growth, thereby underscoring the importance of using population models to extend the inference of individual-level experiments. Author Affiliation: (1)Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA (2)Department of Biology, University of Miami, PO Box 249118, Coral Gables, FL 33124, USA (3)National Center for Ecological Analysis and Synthesis, University of California - Santa Barbara, 735 State Street, Suite 300, Santa Barbara, CA 93101, USA Article History: Received 14 August 2009; accepted 6 November 2009 Handling Editor: Hans de Kroon Article note: (*) Correspondence author. E-mail: john.maron@mso.umt.eud

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1365-2745.2009.01587.x Byline: Christian Damgaard (1), Adeline Fayolle (2) Keywords: competition; ecological success; environmental gradient; fitness; importance; intensity; population dynamics Abstract: Summary 1. Currently, there is a debate among plant ecologists on the concepts of the intensity of competition and the importance of competition, which is central to many issues of modern plant population ecology and plant community ecology. 2. It is problematic that the current measures of intensity and importance of competition, typically, are reported as dimensionless indices because they hide the fact that both indices are functions of plant density and the level of the environmental gradient. 3. Here, a new formulation of the concepts is suggested, which explicitly highlights the functional dependencies on plant density and the level of the environmental gradient. The new measures are a generalization of the previous indices and correspond to the previous indices in the case of a simple experimental design. 4. The suggested measures of the intensity and importance of competition are exemplified using data from a response surface competition experiment between Agrostis capillaris and Festuca ovina along a herbicide gradient, where the expected clear effect of plant density was demonstrated. 5. Synthesis. As the suggested measures of the intensity and importance of competition explicitly highlight the functional dependencies on plant density and the level of the environmental gradient, we think that they will help to ensure a closer connection between experimental plant ecology and the attempts to model plant populations and communities. Author Affiliation: (1)Department of Terrestrial Ecology, NERI, University of Aarhus, Vejlsovej 25, 8600 Silkeborg, Denmark (2)Cirad, Environments and Societies Department, Natural Forest Dynamics Research Unit, Campus International de Baillarguet, TA 10C, BP 5035, 34035 Montpellier, France Article History: Received 12 May 2009; accepted 3 September 2009 Handling Editor: David Gibson Article note: (*) Correspondence author. E-mail: cfd@dmu.dk

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1365-2745.2009.01585.x Byline: Harmony J. Dalgleish (*), David N. Koons, Peter B. Adler Keywords: climate change; elasticity; life history; matrix models; mixed-grass prairie; short-lived perennial; stochastic demography Abstract: Summary 1. Climate change will cause changes in average temperature and precipitation as well as increased fluctuations around the mean, yet few studies have considered the impacts of altered climate variability on plant populations. We tested whether life-history traits (expected life span, generation time and seed size) can predict plant responses to increased environmental variability across similar plant species sharing the same habitat. 2. We combined long-term demographic data on 10 prairie forb species with stochastic demography techniques to estimate the effects of potential changes in matrix element means and variances on the long-term stochastic population growth rate. 3. For all 10 species, recruitment had higher contribution and elasticity values than survival, meaning that climate change is more likely to influence population growth through effects on recruitment than on survival for these relatively short-lived forbs. Species with longer generation times had lower elasticities to increases in matrix element variability. 4. Synthesis. Our analysis of a unique, long-term data set suggests that longer-lived plant species will be less vulnerable to the effects of future increases in climate variability. While this relationship was previously reported for diverse taxa from many locations, our results show that it also applies within a guild of short-lived species from a single community. The generality of the pattern demonstrates the potential for using life-history traits to make predictions about which species may be the most vulnerable to climate change. Article History: Received 6 April 2009; accepted 25 August 2009 Handling Editor: Hans de Kroon Article note: (*) Correspondence author. E-mail: h.dalgleish@usu.edu

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1365-2745.2009.01574.x Byline: Mariska te Beest (1), Nicola Stevens (2), Han Olff (1), Wim H. van der Putten (3,4) Keywords: accumulation of local pathogens; biological invasions; biomass allocation; Chromolaena odorata; enemy release; evolution of increased competitive ability; Panicum maximum; plant-soil interactions Abstract: Summary Soil communities and their interactions with plants may play a major role in determining the success of invasive species. However, rigorous investigations of this idea using cross-continental comparisons, including native and invasive plant populations, are still scarce. We investigated if interactions with the soil community affect the growth and biomass allocation of the (sub)tropical invasive shrub Chromolaena odorata. We performed a cross-continental comparison with both native and non-native-range soil and native and non-native-range plant populations in two glasshouse experiments. Results are interpreted in the light of three prominent hypotheses that explain the dominance of invasive plants in the non-native range: the enemy release hypothesis, the evolution of increased competitive ability hypothesis and the accumulation of local pathogens hypothesis. Our results show that C. odorata performed significantly better when grown in soil pre-cultured by a plant species other than C. odorata. Soil communities from the native and non-native ranges did not differ in their effect on C. odorata performance. However, soil origin had a significant effect on plant allocation responses. Non-native C. odorata plants increased relative allocation to stem biomass and height growth when confronted with soil communities from the non-native range. This is a plastic response that may allow species to be more successful when competing for light. This response differed between native and non-native-range populations, suggesting that selection may have taken place during the process of invasion. Whether this plastic response to soil organisms will indeed select for increased competitive ability needs further study. The native grass Panicum maximum did not perform worse when grown in soil pre-cultured by C. odorata. Therefore, our results did not support the accumulation of local pathogens hypothesis. Synthesis. Non-native C. odorata did not show release from soil-borne enemies compared to its native range. However, non-native plants responded to soil biota from the non-native range by enhanced allocation in stem biomass and height growth. This response can affect the competitive balance between native and invasive species. The evolutionary potential of this soil biota-induced change in plant biomass allocation needs further study. Author Affiliation: (1)Community and Conservation Ecology Group, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands (2)South African Environmental Observation Network, Ndlovu Node, Private Bag X1021, Phalaborwa 1390, South Africa (3)Netherlands Institute of Ecology, PO Box 40, 6666 ZG Heteren, The Netherlands (4)Laboratory of Nematology, Wageningen University and Research Centre, PO Box 8123, 6700 ES Wageningen, The Netherlands Article History: Received 6 October 2008; accepted 12 August 2009 Handling Editor: Rene van der Wal Article note: (*) Correspondence author. E-mail: mariskatebeest@hotmail.com

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1365-2745.2009.01562.x Keywords: alpine meadow; density-dependent mortality; Elymus nutans; facilitation; individual-based model; plant-plant interactions; size inequality Abstract: Summary Large variation in the size of individuals is a ubiquitous feature of natural plant populations. While the role of competition in generating this variation has been studied extensively, the potential effects of positive interactions among plants, which are common in high-stress environments, have not been investigated. Using an individual-based 'zone-of-influence' model, we investigate the effects of competition, abiotic stress and facilitation on size inequality in plant monocultures. In the model, stress reduces the growth rate of plants, and facilitation ameliorates the effects of stress. Both facilitation and competition occur in overlapping zones of influence. We tested some of the model's predictions with a field experiment using the clonal grass Elymus nutans in an alpine meadow. Facilitation increased the size inequality of model populations when there was no density-dependent mortality. This effect decreased with density as competition overwhelmed facilitation. The lowest size inequality was found at intermediate densities both with the model and in the field. When density-dependent mortality was included in the model, stress delayed its onset and reduced its rate by reducing growth rates, so the number of survivors at any point in time was higher under harsh than under more benign conditions. Facilitation increased size inequality during self-thinning. Synthesis. Our results demonstrate that facilitation interacts with abiotic stress and competition to influence the degree of size inequality in plant populations. Facilitation increased size inequality at low to intermediate densities and during self-thinning. Author Affiliation: (1)MOE Key Laboratory of Arid and Grassland Ecology at Lanzhou University, Lanzhou, 730000, China (2)Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, DK-1870 Frederiksberg, Denmark (3)Area de Biodiversidad y Conservacion, Departamento de Biologia y Geologia, Escuela Superior de Ciencias Experimentales y Tecnologia, Universidad Rey Juan Carlos, c/ Tulipan s/n, 28933 Mostoles, Spain (4)MOE Key Laboratory of Western China's Environmental System at Lanzhou University, Lanzhou, 730000, China Article History: Received 31 March 2009; accepted 29 July 2009 Handling Editor: James Cahill Article note: (*) Correspondence author. E-mail: wgmg36@lzu.edu.cn

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1600-0706.2009.17595.x Byline: Satu Ramula, Yvonne M. Buckley Abstract: Negative density dependence resulting from intraspecific competition can regulate plant populations by limiting demographic rates (survival, growth, fecundity). However, the strength of intraspecific competition can vary within and among populations due to spatial or temporal environmental heterogeneity, or genetic differences. Quantification of variation under a relatively constant environment is needed to assess the inherent potential for density dependence to vary. This knowledge will help adjust data collection effort required for parameterisation of density dependence. Our review of published plant demographic studies revealed that only half of the studies included the whole life-cycle in the analysis of density dependence. Approximately half of the studies manipulated density, while the rest examined density dependence from observed densities in the field. Regardless of the design used, density dependence was estimated from a small number of replicates. To investigate inherent variation in density dependence during the life-cycle, and the effect of low replication on density dependence estimates, we combined an experimental approach with simulations for an invasive herb Senecio madagascariensis. We found significant negative density dependence for five out of six examined demographic rates in a constant environment, with the strength of density dependence increasing during the life-cycle. An exception was plant growth, in which the direction of density dependence varied from positive to negative depending on the life stage. Simulations showed substantial deviation for density dependence parameterised from a small number of replicates even when environmental variation was minimal. This suggests that data collection procedures currently used to assess the effect of density on plant demographic rates may produce inaccurate estimates, increasing uncertainty in demographic models. Due to variation in the direction and strength of density dependence during the life-cycle, multiple life stages with multiple replicated density levels are required to parameterise density dependence for demographic rates. Article History: Manuscript Accepted 26 February 2009 Article note: S. Ramula (satu_ramula@hotmail.com) and Y. M. Buckley, Univ. of Queensland, School of Biological Sciences, Queensland 4072, Australia. YMB also at: CSIRO Sustainable Ecosystems, 306 Carmody Rd, St. Lucia, Queensland 4067, Australia.

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1365-2745.2009.01516.x Byline: David J. Ayre (1), Kym M. Ottewell (1), Siegfried L. Krauss (2), Robert J. Whelan (1) Keywords: fire ecology; genetic diversity; microsatellites; pollen dispersal; Proteaceae; seed banks; seed dispersal Abstract: Summary Increased fire frequency is seen as a key threat to plant populations in Mediterranean-type ecosystems across the globe. Short inter-fire periods may exhaust soil-stored and fire-stimulated seed banks of fire-sensitive species, reducing actual and effective population sizes and eroding genetic diversity. Here we used microsatellite genotyping to investigate the genetic impacts of repeated wildfires and, in particular, the contribution of above-ground genetic processes (seed and pollen dispersal) to the genetic structuring and composition of post-fire recruits in an isolated population of the fire-sensitive shrub Persoonia mollis ssp. nectens. We tested the hypothesis that limited pollen and seed dispersal, in combination with the potentially patchy effects of fire at a fine scale within populations, would generate a highly structured population, a decline in genetic diversity after each fire and genetic heterogeneity between successive cohorts. Wildfires killed all 25 adult plants in 1997 and, in 2001, killed all of the 476 seedlings remaining from the 1997 seedling cohort. Although there was no possibility of replenishment of the seed bank in the interval between fires, a second cohort of 381 seedlings emerged after the 2001 fire. We found no evidence that successive fires produced either a decline in genetic diversity, as measured by allelic richness or expected heterozygosity, or the genetic differentiation of adult and successive seedling cohorts (Pairwise F.sub.ST = -0.0125 to 0.0009). The seedling cohorts displayed less genetic structuring than anticipated. Spatial genetic structure was low, ranging from Sp = 0.02 in the 1997 seedlings to Sp = 0.06 in the 2001 seedlings, and using parentage analysis, we found that seedlings clustered under dead adults rarely reflected simple seed shadows. Synthesis. Overall, we found that a numerically large seed bank with a bet-hedging strategy of staged seed germination, in combination with genetic mixing achieved by both pollen and seed dispersal, provides a powerful buffer against the negative impacts of frequent fire in P. mollis ssp. nectens. Author Affiliation: (1)Institute for Conservation Biology, University of Wollongong, Wollongong, NSW 2522, Australia (2)Botanic Gardens and Parks Authority, Kings Park and Botanic Garden, Fraser Avenue, West Perth, WA 6005, Australia, and School of Plant Biology, University of Western Australia, Crawley, WA 6009, Australia Article History: Received 16 February 2009; accepted 14 April 2009Handling Editor: John Pannett Article note: ([dagger]) Correspondence author and present address. School of Earth and Environmental Sciences, University of Adelaide, North Terrace, Adelaide SA 5005, Australia. E-mail: kym.ottewell@adelaide.edu.au

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1365-2745.2009.01499.x Byline: Donald A. Levin, Christopher D. Kelley, Sahotra Sarkar (*) Keywords: Allee effects; cellular automata; founder effects; individual-based models; S-alleles; self-incompatibility; viability model Abstract: Summary Founder populations of plants are usually small and may become extinct due to many factors including inbreeding and low pollen transfer besides stochastic factors. This positive relationship between population size and individual fitness is taken as evidence of an Allee effect. Very few studies have quantitatively compared the influence of self-incompatibility systems and S-allele counts on the magnitude of observed Allee effects for different population sizes and seed and pollen dispersal distances. This paper uses a stochastic, spatially explicit, individual-based cellular automaton model to simulate the dynamics of newly established plant populations with sporophytic or gametophytic self-incompatibility (SI) alleles and compares these to a null (Mendelian) population. Parameters varied in model simulation are the S-allele count, the initial population size, and the pollen and seed dispersal distances. These parameters were studied over a wide range to assess their relative impact on population viability compared to the null case in order to model the effect of self-incompatibility on population fitness. The results indicate that Allee effects are enhanced and growth rates are slowed in newly established populations of species with S-alleles relative to Mendelian populations, leading to enhanced extinction risk. They also show the importance of the relationship between pollen and seed dispersal ranges on the fitness of the population. Populations with sporophytic self-incompatibility were more extinction-prone than those with gametophytic SI, and the latter more so than Mendelian populations when all other factors were held constant. Synthesis. Overall, the simulation results indicate that Allee effects in small populations are enhanced in plants with S-alleles. Even in relatively large populations, S-allele count controls the strength of observed Allee effects. A high S-allele count is able to compensate for lower initial population size. Pollen and seed dispersal ranges had a similarly strong effect on the viability of populations with S-alleles. These effects are stronger in populations with sporophytic self-incompatibility than in those with gametophytic SI. Simulation results also indicate that S-alleles were not lost to genetic drift over time, in contrast with some earlier studies of S-allele systems displaying Allee effects. Article History: Received 11 October2008; accepted 16 February 2009Handling Editor: Peter Klinkhamer Article note: (*) Correspondence author. E-mail: sarkar@mail.utexas.edu

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1365-2745.2009.01492.x Byline: Richard M. Gunton (*[dagger]), William E. Kunin Keywords: autocorrelation; competition; neighbourhood; pollination; reproduction; seed herbivory; Silene latifolia; spatial density-dependence; survival Abstract: Summary The survival and reproduction of individual plants may be related to the distribution of conspecific neighbours with which they interact. We used 2 years' data from a field experiment to relate the reproduction and survival of focal Silene latifolia plants to the numbers of conspecific plants and flowers within a range of distances (0.16-150 m) from the focal plants. Thus we consider spatial scale as a continuously-varying component of population density. Because the data come from a single continuous population, we fitted regression models in two stages in order to remove spatial autocorrelation induced by environmental factors before modelling density effects. As well as single-scale models, we fitted multiple-scale models to explore interaction kernels. We statistically standardized plant size in some analyses to isolate pollination effects. Reproductive output per plant generally decreased with greater densities of plants and flowers; for example there was a negative effect of female flowers within a 70-m radius in the second year. However, at low female densities there was a positive effect of male flowers at a scale of 13 m in the first year. Seed-set per flower decreased with greater densities of flowers in the second year (at radii < 10 m). Seed predation was greater when more female flowers were present within 5-7 m. Plants' survival probability increased with density within 0.28 m for all but the smallest plants. We also collected data on the pattern and reproductive success of S. latifolia plants in a natural population nearby and applied similar methodology. Here the negative effects of female flower densities occurred at finer scales and gave way to positive effects above 2 m, contrasting with some patterns from the experiment. Synthesis. In a sessile population interacting with mobile biota, the effects of density on individual fitness may vary with the way in which density is measured. This, together with the methodological challenges for analysing spatial data from continuous populations, should be considered when designing and interpreting studies of spatial density-dependence. Taking these issues into account, we may begin to explain the spatial patterns of natural populations. Article History: Received 21 June 2008; accepted 9 February 2009Handling Editor: Rob Brooker Article note: (*) Correspondence author. E-mail: rmg@cantab.net

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1365-2745.2008.01470.x Byline: Daniel Garcia (1), Mariano A. Rodriguez-Cabal (2), Guillermo C. Amico (2) Keywords: Dromiciops gliroides; fruit resource tracking; principal coordinates analysis of neighbour matrices; recruitment; spatial patchiness; southern Argentina; Tristerix corymbosus Abstract: Summary Seed dispersal is considered critical for shaping the spatial structure of plant populations, though little empirical effort has been made to interpret this effect in terms of the scale at which plant species are distributed and cope with environmental heterogeneity. We assessed the spatial role of seed dispersal in Tristerix corymbosus, a mistletoe dispersed exclusively in the temperate forests of Patagonia by the endemic marsupial Dromiciops gliroides. We examined how fruit resource tracking and seed dispersal by the marsupial affects mistletoe recruitment, employing a spatially explicit approach aimed at breaking down the spatial structure of the mistletoe and marsupial populations at different scales. In a single fruiting season, we evaluated the abundance of mistletoe fruits, adult plants, dispersed seeds and recruits (seedlings and saplings), as well as the abundance of marsupials, along a 1500-m linear transect. Both mistletoe and marsupial abundances were distributed hierarchically in space, with large patches containing smaller ones. Marsupial patchiness matched that of mistletoe fruits, at least at a broad scale within the transect. Marsupial abundance also varied at a large-scale, being conditioned by habitat features and decreasing progressively along the transect. Mistletoe seed rain accounted for the patchiness of adult plants and fruits, and for the large-scale pattern of marsupial activity. The spatial pattern of mistletoe recruitment closely matched seed rain. Synthesis. Seed dispersal by marsupials shaped the scale of mistletoe recruitment in two ways. First, marsupials created a spatial match between mistletoe adults and recruits as a result of fruit resource tracking. Second, they generated patchiness in mistletoe offspring at a larger scale than in adults. Dispersal process performed as a strong demographic filter capable of changing the mistletoe spatial structure from adults to recruits, despite a low frequency of far-from-adult dispersal events. Similar effects of scale shaping by seed dispersers may be generalized among plants in which there is a sharp spatial match between fruits and frugivores, and whose dispersed seeds have a higher probability of recruiting than undispersed ones. Author Affiliation: (1)Departamento de Biologia de Organismos y Sistemas, Universidad de Oviedo, Instituto Cantabrico de Biodiversidad (CSIC-Universidad de Oviedo-Principado de Asturias), C/ Rodrigo Uria s/n, Oviedo 33071, Asturias, Spain (2)Laboratorio Ecotono, CRUB, Universidad Nacional del Comahue, Bariloche, Rio Negro, Argentina Article History: Received 19 May 2008; accepted 24 November 2008 Handling Editor: Richard Bardgett Article note: (*) Correspondence author. E-mail: danielgarcia@uniovi.es

To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1523-1739.2008.01073.x Byline: SHARMILA PATHIKONDA (*), AZMY S. ACKLEH ([dagger]), KARL H. HASENSTEIN (*), SUSAN MOPPER (*[double dagger]) Keywords: clonal plants; exotic species; extinction; habitat disturbance; hurricanes; Iris hexagona; I. pseudacorus; matrix models; population dynamics; species competition Abstract: Abstract: Wetland habitats are besieged by biotic and abiotic disturbances such as invasive species, hurricanes, habitat fragmentation, and salinization. Predicting how these factors will alter local population dynamics and community structure is a monumental challenge. By examining ecologically similar congeners, such as Iris hexagona and I. pseudacorus (which reproduce clonally and sexually and tolerate a wide range of environmental conditions), one can identify life-history traits that are most influential to population growth and viability. We combined empirical data and stage-structured matrix models to investigate the demographic responses of native (I. hexagona) and invasive (I. pseudacorus) plant populations to hurricanes and salinity stress in freshwater and brackish wetlands. In our models I. hexagona and I. pseudacorus responded differently to salinity stress, and species coexistence was rare. In 82% of computer simulations of freshwater marsh, invasive iris populations excluded the native species within 50 years, whereas native populations excluded the invasive species in 99% of the simulations in brackish marsh. The occurrence of hurricanes allowed the species to coexist, and species persistence was determined by the length of time it took the ecosystem to recover. Rapid recovery (2 years) favored the invasive species, whereas gradual recovery (30 years) favored the native species. Little is known about the effects of hurricanes on competitive interactions between native and invasive plant species in marsh ecosystems. Our models contribute new insight into the relationship between environmental disturbance and invasion and demonstrate how influential abiotic factors such as climate change will be in determining interspecific interactions. Abstract (Spanish): Invasion, Perturbacion y Competencia: Modelando el Destino de Poblaciones de Plantas Costeras Resumen: Los habitats de humedales estan acosados por perturbaciones bioticas y abioticas como las especies invasoras, huracanes, fragmentacion de habitat y salinizacion. La prediccion de como estos factores alteraran la dinamica poblacional y la estructura de la comunidad es un reto monumental. Mediante el examen de congeneres similares ecologicamente, como Iris hexagona e I. pseudacorus (que se reproducen por clones y sexualmente y toleran un amplio rango de condiciones ambientales), se pueden identificar caracteristicas de la historia de vida que son mas influyentes en el crecimiento y la viabilidad poblacional. Combinamos datos empiricos y modelos matriciales estructurados por estadios para investigar las respuestas de las poblaciones de plantas nativas (I. hexagona) e invasoras (I. pseudacorus) a huracanes y estres por salinidad en humedales de agua dulce y salobre. En nuestros modelos, I. hexagona e I. pseudacorus, respondieron de manera diferente al estres por salinidad y la coexistencia de las especies fue rara. En 82% de las simulaciones en computadora del humedal dulceacuicola, las poblaciones invasoras excluyeron a las especies nativas en un plazo de 50 anos, mientras que las poblaciones nativas excluyeron a la especie invasora en 99% de las simulaciones de humedal salobre. La ocurrencia de huracanes permitio la coexistencia de las especies, y la persistencia de las especies estaba determinada por el tiempo que tomaba la recuperacion del ecosistema. La recuperacion rapida (2 anos) favorecio a la especie invasora, mientras que la recuperacion gradual (30 anos) favorecio a la especie nativa. Se sabe poco sobre los efectos de los huracanes sobre las interacciones competitivas entre especies de plantas nativas e invasoras en ecosistemas de marisma. Nuestros modelos aportan una nueva perspectiva de las relaciones entre la perturbacion ambiental y las invasiones y demuestran la influencia de factores abioticos, como el cambio climatico, en la determinacion de interacciones interespecificas. Author Affiliation: (*)Department of Biology, University of Louisiana at Lafayette, Lafayette, LA 70504, U.S.A. ([dagger])Department of Mathematics, University of Louisiana at Lafayette, Lafayette, LA 70504, U.S.A. Article History: Paper submitted December 31, 2007; revised manuscript accepted May 15, 2008. Article note: ([double dagger]) Address correspondence to S. Mopper, email mop@louisiana.edu

Summarizing complex temporal dynamics in communities is difficult to achieve in a way that yields an intuitive picture of change. Rank clocks and rank abundance statistics provide a graphical and analytical framework for displaying and quantifying community dynamics. We used rank clocks, in which the rank order abundance for each species is plotted over time in temporal clockwise direction, to display temporal changes in species abundances and richness. We used mean rank shift and proportional species persistence to quantify changes in community structure in long-term data sets from fertilized and control plots in a late successional old field, frequently and infrequently burned tallgrass prairie, and Chihuahuan desert grassland and shrubland communities. Rank clocks showed that relatively constant species richness masks considerable temporal dynamics in relative species abundances. In the old field, fertilized plots initially experienced high mean rank shifts that stabilized rapidly below that of unfertilized plots. Rank shifts were higher in infrequently burned vs. annually burned tallgrass prairie and in desert grassland compared to shrubland vegetation. Proportional persistence showed that arid grasslands were more dynamic than mesic grasslands. We conclude that rank clocks and rank abundance statistics provide important insights into community dynamics that are often hidden by traditional univariate approaches. Key words: community dynamics; proportional persistence; rank-abundance curves; rank clock; rank shifts; species diversity; temporal dynamics.

It is widely accepted that species are most abundant at the center of their geographic ranges and become progressively rarer toward range limits. Although the abundant center model (ACM) has rarely been tested with range-wide surveys, it influences much thinking about the ecology and evolution of species' distributions. We tested ACM predictions using two unrelated but ecologically similar plants, Camissonia cheiranthfolia and Abronia umbellata. We intensively sampled both throughout their one-dimensional distributions within the Pacific coastal dunes of North America, from northern Baja California, Mexico, to southern Oregon, USA. Data from >1100 herbarium specimens indicated that these limits have been stable for at least the last 100 years. Range-wide field surveys detected C. cheiranthifolia at 87% of 124 sites and A. umbellata at 54% of 113 sites, but site occupancy did not decline significantly toward range limits for either species. Permutation analysis did not detect a significant fit of geographical variation in local density to the ACM. Mean density did not correlate negatively with mean individual performance (plant size or number of seeds/plant), probably because both species occur at low densities. Although size and seeds per plant varied widely, central populations tended to have the highest values for size only. For C. cheiranthifolia, we observed asymmetry in the pattern of variation between the northern and southern halves of the range consistent with the long-standing prediction that range limits are imposed by different ecological factors in different parts of the geographical distribution. However, these asymmetries were difficult to interpret and likely reflect evolutionary differentiation as well as plastic responses to ecological variation. Both density and seeds per plant contributed to variation in seed production per unit area. In C. cheiranthifolia only, sites with highest seed production tended to occur at the range center, as predicted by the ACM and assumed by theory proposing that range limits evolve via antagonism between natural selection and gene flow. Key words: Abronia umbellata; abundant center model; Camissonia cheiranthifolia; coastal dunes; geographic ranges; habilat occupancy; plant size: plants; range limits; seed production.

Inference of population structure from neutral marker loci is a key issue for association genetics. However, the presence of highly related individuals, commonly observed in breeders' panels, may lead to deviation from model hypotheses and therefore unreliable group assignment. The present note proposes a tool to help interpret Structure software outputs on populations that include highly related individuals, such as plant breeding material. We ran Structure software on simple sequence repeat (SSR) data from two maize (Zea mays L. ssp. mays) inbred panels. We propose a criterion to evaluate Structure stability based on Euclidian distance between outputs. This approach shows a high stability across runs for the panel composed of first cycle inbred lines. On the contrary, the presence of highly related individuals in the second panel induces strong instability in Structure outputs.

Breeders face many complex choices in the design of efficient crossing and selection strategies aimed at combining desired alleles into a single target genotype. Both population genetic theory and a breeding simulation tool were used to study the effects of different strategies on population size and number of marker assays required to recover a target genotype in wheat (Triticum aestivum L). Enriching the frequency of desirable alleles in the [F.sub.2] of single-cross and in the [F.sub.1] of backcross and topcross populations greatly reduced the minimum required population size, but the gain from another enrichment selection is minor. General equations were developed to determine appropriate crossing strategies, and sequential culling was proposed to minimize total marker screening costs. For a topcross of three adapted lines from an existing breeding program, simulation of changes in allele frequencies at nine target genes (seven unlinked) showed that population size was minimized with a three-stage selection strategy in the [F.sub.1] generation of the topcross (TC[F.sub.1]), the [F.sub.2] generation of the topcross (TC[F.sub.2]), and doubled haploid lines (DHs). Enrichment of allelic frequencies in TC[F.sub.2] reduced the total number of lines screened from >3500 to 0.97 after selection, while the tin reduced-tillering allele was only at 0.77 in the final selected population due to its strong repulsion-phase linkage to the grain quality gene Glu-A3 in this cross and the incomplete linkage of the tin marker. Therefore, the presence of the tin gene needs to be further confirmed by other methods.

The combined effects of dominance and inbreeding on covariances between relatives are still poorly understood in maize (Zea mays L.) populations. Our objectives were to address the following questions: (i) What is the importance of dominance in a maize synthetic? (ii) How does inbreeding affect the genetic variance among individuals in a maize synthetic. (iii) How do the covariance parameters compare between populations? (iv) How does breeding design impact estimators? We estimated covariance components for inbred relatives in the maize synthetic BSCB1(R)C13. Previous estimates of covariance parameters have been used to explain the ineffectiveness of inbred progeny selection in the stiff-stalk population BS13. We found that the dominance variance was larger than the additive variance for grain yield, whereas the additive variance was larger than the dominance variance for all other traits. Negative estimates of the covariance between additive and homozygous dominance deviations were found for all traits with the exception of traits associated with reproductive maturity, suggesting a negative relationship between inbred and outbred performance. The correlation between genotypic values and breeding values was lower for grain yield than for any other trait. Our results were similar to previous results found in the stiff-stalk maize population BS13, suggesting similarity in structure among populations.

To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1523-1739.2006.00370.x Byline: YVONNE HERRERIAS-DIEGO (*), MAURICIO QUESADA (*[double dagger]), KATHRYN E. STONER (*), JORGE A. LOBO ([dagger]) Keywords: bat pollinators; Bombacaceae; flowering phenology; Mexico; plant reproduction Abstract: Abstract: Spatial isolation caused by forest fragmentation and temporal isolation caused by asynchronous flowering of plants have been proposed as important factors that affect the reproduction of plant populations. In a 4-year study, we determined the effects of forest fragmentation and spatial isolation on flowering phenology and reproductive success of the tropical tree Ceiba aesculifolia ([Kunth] Britton & Rose). We conducted our study in the dry forest of Mexico and compared populations in two habitat conditions based on density and environmental conditions: (1) disturbed habitat (four populations of [less than or equal to]3 reproductive individuals/ha surrounded by agricultural fields or pastures) and (2) undisturbed habitat (three populations of groups of [greater than or equal to]6 reproductive individuals/ha surrounded by undisturbed mature forest). We compared the following variables within these populations over 4 years: flowering overlap, proportion of individuals with flowers and fruit, total flower production, total fruit production, fruit set, seed production, and seed abortion. Little overlap in flowering occurred among the populations in the two habitat conditions. The flowering period of trees in the disturbed habitat initiated between 15 to 20 days before the flowering period of trees in the undisturbed habitat during 3 years. Flowering of trees in the undisturbed habitat peaked at the end of the flowering period of the trees in the disturbed habitat. The proportion of trees that flowered was greater in the undisturbed habitat. Nevertheless, total flower production was greater in the disturbed habitat and these differences were maintained across 3 years. The proportion of individuals that produced fruit did not differ across habitat conditions but did differ across years. Total fruit production was greater in the disturbed habitat, but fruit set and seed production were the same across years and between habitat conditions. Seed abortion varied over years between habitats. We concluded that forest fragmentation does not negatively affect the reproductive success of C. aesculifolia. It appears that the highly mobile bat pollinators maintain reproductive connectivity between trees in both habitats. Abstract (Spanish): Efectos de la Fragmentacion de Patrones Fenologicos y Exito Reproductivo del Arbol de Bosque Tropical Seco Ceiba aesculifolia Resumen: El aislamiento espacial causado por la fragmentacion de bosques y el aislamiento temporal causado por la floracion asincronica de plantas han sido propuestos como factores importantes que afectan a la reproduccion de poblaciones de plantas. En un estudio de 4 anos, determinamos los efectos de la fragmentacion de bosques y el asilamiento espacial sobre la fenologia de floracion y exito reproductivo del arbol tropical Ceiba aesculifolia ([Kunth]) Britton and Rose). Realizamos nuestro estudio en un bosque seco de Mexico y comparamos poblaciones en dos condiciones de habitat con base en la densidad y las condiciones ambientales: (1) habitat perturbado (cuatro poblaciones de [less than or equal to]3 individuos reproductivos/ha rodeadas por campos agricolas o pastizales) y (2) habitat no perturbado (tres poblaciones de grupos de [greater than or equal to]6 individuos reproductivos/ha rodeadas por bosque maduro no perturbado). Comparamos las siguientes variables en esas poblaciones durante 4 anos: traslape de floracion, proporcion de individuos con flores y frutos, produccion total de flores, produccion total de frutos, relacion fruto/flor, produccion de semillas y aborto de semillas. Entre las poblaciones en las dos condiciones de habitat ocurrio poco traslape en la floracion. El periodo de floracion de arboles en el habitat perturbado inicio entre 15 y 20 dias antes del periodo de floracion en el habitat no perturbado durante 3 anos. La floracion de arboles en el habitat no perturbado alcanzo su maximo al final del periodo de floracion de arboles en el habitat perturbado. La proporcion de arboles que florearon fue mayor en el habitat no perturbado. Sin embargo, la produccion total de flores fue mayor en el habitat perturbado y estas diferencias se mantuvieron durante 3 anos. La proporcion de individuos que produjeron frutos no difirio entre las condiciones de habitat pero no difirio en los anos. La produccion total de frutos fue mayor en el habitat perturbado, pero la relacion fruto/flor y la produccion de frutos fueron iguales todos los anos y entre condiciones de habitat. El aborto de semillas vario en los anos y entre habitats. Concluimos que la fragmentacion de bosques no afecta negativamente al exito reproductivo de C. aesculifolia. Parece que los murcielagos polinizadores altamente moviles mantienen conectividad reproductiva entre arboles en ambos habitats. Author Affiliation: (*)Centro de Investigaciones en Ecosistemas, Universidad Nacional Autonoma de Mexico, Campus Morelia, Apartado Postal 27-3 (Xangari), Morelia, Michoacan 58089, Mexico ([dagger])Universidad de Costa Rica, Escuela de Biologia, San Jose, Costa Rica Article History: Paper submitted April 27, 2005; revised manuscript accepted September 1, 2005. Article note: ([double dagger]) Address correspondence to M. Quesada, email mquesada@oikos.unam.mx

To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1523-1739.2006.00368.x Byline: KARI LEHTILA (*), KIMMO SYRJANEN ([dagger]), ROOSA LEIMU ([double dagger]), MARIA BEGONA GARCIA (s.), JOHAN EHRLEN (**) Keywords: elasticity; habitat closure; life table response experiment analysis; population growth rate; population viability; restoration Abstract: Abstract: Although the effects of deterministic factors on population viability often are more important than stochasticity, few researchers have dealt with the effect of deterministic habitat changes on plant population demography. We assessed population viability for the perennial herb Primula veris L. and identified targets for management based on demographic data from five different habitat types representing different degrees of canopy closure. We conducted replicate studies at the border of the distribution area and in more central parts. Demographic patterns were similar between the two regions. Most study populations had a positive population growth, and only populations in late phases of forest succession showed consistently negative trends. The populations of open habitats had high seedling recruitment, and the populations of early and middle forest succession had high seed production. The importance of survival for population growth rate increased with increasing habitat closure, whereas the importance of growth and reproduction decreased. Results of the elasticity analysis suggested that the best method to manage decreasing late-successional populations is to increase survival of the largest individuals. The life-table response experiment (LTRE) analysis, however, showed that survival of the largest individuals contributed little to differences in population growth rates of different habitats, whereas seed production and growth of small individuals were more important. Moreover, direct perturbation of the performance of the largest stages showed that late-successional populations would not attain positive population growth even if the largest stages had no mortality at all. We conclude that restoration of recruitment is the only possibility for positive population growth in late-successional populations of P. veris, although the elasticities of recruitment transitions are low. Our results also suggest that retrospective demographic methods such as LTRE constitute an important and necessary complement to prospective methods such as elasticities in identifying management targets. Abstract (Spanish): Cambio de Habitat y Demografia de Primula veris: Identificacion de Objetivos de Conservacion Resumen: Aunque los efectos de factores deterministicos sobre la viabilidad poblacional a menudo son mas importantes que la estocasticidad, pocos investigadores han abordado el efecto de los cambios deterministicos del habitat sobre la demografia de poblaciones de plantas. Evaluamos la viabilidad poblacional de la hierba perenne Primula veris L. e identificamos objetivos para su gestion con base en datos demograficos obtenidos en cinco tipos de habitat diferentes que representan diferentes grados de oclusion del dosel. Realizamos estudios replicados en el limite del area de distribucion y en areas mas centrales. Los patrones demograficos eran similares en las dos regiones. La mayoria de las poblaciones estudiadas tenian un crecimiento poblacional positivo, y solo mostraron tendencias consistentemente negativas las poblaciones en fases avanzadas de sucesion del bosque. Las poblaciones en habitats abiertos tenian alto reclutamiento de plantulas, y las poblaciones en bosques en sucesion temprana y media tenian alta produccion de semillas. La importancia de la supervivencia para la tasa de crecimiento poblacional aumento con el incremento de la oclusion del habitat, mientras que disminuyo la importancia del crecimiento y la reproduccion. Los resultados del analisis de elasticidad sugieren que el mejor metodo para manejar poblaciones decrecientes de etapas tardias de sucesion es el incremento de la supervivencia de los individuos mas grandes. Sin embargo, el analisis de experimento de respuesta de tabla de vida (ERTV) mostro que la supervivencia de los individuos mas grandes contribuyo poco a las diferencias en las tasas de crecimiento poblacional en habitats diferentes, mientras que la produccion de semillas y el crecimiento de individuos pequenos fueron mas importantes. Mas aun, la perturbacion directa del funcionamiento de las etapas mayores mostro que las poblaciones de sucesion tardia no llegarian a tener crecimiento poblacional positivo aun si no hubiera mortalidad en las etapas mayores. Concluimos que la restauracion del reclutamiento es la unica posibilidad de crecimiento poblacional en poblaciones de P. veris de sucesion tardia, aunque las elasticidades de las transiciones de reclutamiento sean bajas. Nuestros resultados tambien sugieren que los metodos demograficos retrospectivos, como ERTV, constituyen un complemento necesario e importante de los metodos prospectivos, como las elasticidades, en la identificacion de objetivos de conservacion. Author Affiliation: (*)Department of Natural Sciences, Sodertorn University College, SE-14189 Huddinge, Sweden, emailkari.lehtila@sh.se ([dagger])Finnish Environment Institute, Division of Nature and Land Use, Species Protection Unit, FIN-00251, Helsinki, Finland ([double dagger])Section of Ecology, Department of Biology, University of Turku, FIN-20014 Turku, Finland (s.)Instituto Pirenaico de Ecologia (CSIC), Apdo. 202, 50080 Zaragoza, Spain (**)Department of Botany, Stockholm University, SE-10691 Stockholm, Sweden Article History: Paper submitted March 16, 2005; revised manuscript accepted August 30, 2005.

Genetic analyses of 25 populations of Acacia acuminata Benth for 16 polymorphic allozyme loci reveal a high genetic variation than those encountered in other woody shrubs with similar geographic distribution. However, A. oldfieldii populations show lower levels of genetic diversity but higher than other woody shrubs.

The biotic interactions and community dynamics of plants were analyzed in a prairie grassland ecosystem in a four-year experiment involving 54 species. Recruitment of new species has detrimental effects on the species composition and diversity of native species-rich prairie grasslands. Four years of seed additions in the test sites indicated the successful integration of new species which have germinated, reproduced and competed with native species.

INTRODUCTION One reproductive pathway that seems to have occurred repeatedly within the angiosperms is the evolutionary breakdown of hermaphroditism (cosexuality) towards gender dimorphisms such as dioecy and gynodioecy (de Arroyo [...]

1 In a previous paper, we outlined the physiological prerequisites for population oscillations between a grass and a nitrogen-fixing legume, such as clover. Here, we examine the field-scale consequences of patch-scale oscillations in legume content, using a cellular automaton with variable hierarchy between the two species. 2 We define cell states in the automaton by species content and soil N status. Grass-legume oscillations at the patch scale are represented as an alternation between states of grass dominance (high N) and legume dominance (low N). To this physiologically based population oscillation, we add local extinctions of legume and state-dependent success in legume invasion. 3 Legume populations oscillate at the field scale, given arbitrary initial conditions. However, spatially random perturbations to the soil N status (e.g. urine) establishes a pasture structure that dampens the field scale oscillation. The stabilizing pasture structure comprises moving patches of legume dominance. This pattern was not predicted by our previous, purely physiological model. 4 The model highlights that a patchy species distribution does not in itself mean the species is dispersal limited. In this model, changing the dispersal ability of legumes plays only a limited role in determining their proportion in the mixture. Legume abundance depends as much on the rate at which favourable (low N) sites become available for invasion. 5 Seasonal disturbances that act uniformly across the field, such as winter (legume) mortality and/or springtime fertilizer application, can lead to sustained field scale variations in legume content that are only partly explained by the level of seasonal disturbance itself. Another large part is explained by previous years' legume contents. Pastures may therefore exhibit a 'memory' for legume performance which helps to explain the perceived 'unpredictability' of some grass-legume associations. 6 We argue that legume dynamics in mixed pastures cannot be fully understood without combining ecological and physiological concepts of species interactions at three different scales: competitive interactions at the patch-scale, dispersal at the between-patch scale, and seasonality at the field-scale. Keywords: cellular automaton, metapopulation dynamics, pattern formation, population oscillations

1 A metapopulation approach considers the ecology and genetics of populations as a product of local dynamics and the regional processes of migration, extinction and colonization. While conventional metapopulation theory involves species with frequent population turnover, limited migration and random extinction, it is likely that metapopulation dynamics, broadly defined as the product of local population dynamics and dispersal, is a feature of all species. 2 Theoretical metapopulation models of single species make three critical insights. First, metapopulations will consist of a shifting mosaic of local populations linked through migration with only a fraction of the available habitat patches occupied at one time. Secondly, there is a threshold number of habitats available, below which the species cannot persist because extinction exceeds colonization. Thirdly, the antagonism between selective forces acting during recolonization and population growth can influence the evolution of phenotypic traits. Unfortunately, little empirical data is available to evaluate these ideas for plants or to address the broader issue of whether processes at a regional scale add anything to our understanding of population dynamics. 3 Plants may seem particularly appropriate for metapopulation analyses as a result of their immobility, strong spatial structure and restricted dispersal. However, a review of the literature revealed a paucity of studies that explicitly adopted a metapopulation approach, particularly in terms of testing theoretical models. We argue that this is because of the difficulty of measuring parameters such as extinction, colonization and migration that are central to most metapopulation models. 4 Plants possess a number of special features that present both challenges and opportunities for the development of new insights into the biology of metapopulations. Three particular characteristics, seed dormancy, restricted dispersal and local adaptation, need to be incorporated into existing theoretical models so they more accurately reflect the dynamics of plant metapopulations. Finally, more effort is needed to incorporate the explicit spatial structure of individuals within metapopulations and to investigate the effect that dispersion has on their growth and reproduction. Keywords: colonization, demography, extinction, local adaptation, metapopulation, migration, plants, population genetics, seed dormancy

A study of sex ratio variation in 60 natural populations of the North American dioecious shrub Oemleria cerasiformis is reported. The study revealed that there was an excess of males in 56 of the 60 populations. genet ratio in young plants was 1:1, but was male-biased in mature plants due to differential mortality. Examination of dead genets confirmed that the greater mortality of females was the main cause of male-biased sex ratio in O. cerasiformis.