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In rural Mozambique, as in other African countries, large-scale land acquisitions are on the rise. This process is usually portrayed by host governments and investors as comprising win–win deals th...

In Sweden, the twenty-first century came with a new generation of biosphere reserves (BRs). Between 2005 and 2011 , five nomination forms for BRs were submitted to the Man and Biosphere (MAB) Progr ...

The local implications of large-scale land acquisitions (LSLAs), commonly referred to as land grabs, are at the center of an exponential production of scientific literature that only seldom focuses on gender. Our case study aims to contribute to filling this analytical gap. Based on structured interviews and focus groups, we investigate local experiences in the lower Limpopo valley in Mozambique, where a Chinese investor was granted 20,000 hectares in 2012. Our findings show that land access in the affected area varied prior to land seizure due to historical land use differences and after land seizure mainly due to non-universal compensation. Furthermore, we show that as farming conditions deteriorate, a trend toward both the feminization of smallholder farming and the feminization of poverty is consolidated. Succinctly, as available land becomes increasingly constricted, labor is allocated differently to alternative activities. This process is by no means random or uniform among households, particularly in a context in which women prevail in farm activities and men prevail in off-farm work. As men disengage further from smallholder farming, women remain directly dependent on fields that are smaller and of worse quality or reliant on precarious day labor in the remaining farms. We contend that the categories female-headed and male-headed households, although not inviolable, are useful in explaining the different implications of LSLAs in areas in which gender strongly substantiates individuals’ livelihood alternatives. © 2018 The Author(s) Fieldwork for the study entitled “Large-scale land acquisitions aggravate the feminization of poverty: Findings from a case study in Mozambique” was funded by the Swedish Society for Anthropology and Geography, and the foundation Forskraftstiftelsen Theodor Adelswärds Minne.

To assess the effects of landscape configuration on local plant species richness, we tested whether local species richness of forest understory plants is affected by the total forest area and forest edge length in the adjacent landscape. We also tested whether the landscape effect on species richness is different for forest and edge species. We estimated species richness from 113 forest sites in four regions in Northern Europe. At each site, we studied two plots, one at the edge and one in the core of the forest. Total forested area and forest edge length in circles with a 1-km radius, together with plot-specific variables of environmental conditions and temporal continuity of forests, were recorded at each plot. The amount of forest and the length of the forest edge in the adjacent landscape had a significant positive effect on local species richness of all understory plant species. As expected, edge species were positively affected by increasing length of the forest edge in the landscape, but surprisingly there was no effect of forest area on species richness of forest species. Temporal forest continuity had a negative effect on species richness of edge species but no effect on species richness of forest species. Our results suggest that forest edge length had a stronger landscape effect on understory plant species richness than forest area. Implications of these findings for the management of forest landscapes depend on priorities given to different species groups in biodiversity conservation, i.e. if emphasis is in total species richness or species richness of forest or edge species.

Time lags in responses of organisms to deteriorating environmental conditions delay population declines and extinctions. We examined how local processes at the population level contribute to extinction debt, and how cycles of habitat deterioration and recovery may delay extinction. We carried out a demographic analysis of the fate of the grassland perennial Primula veris after the cessation of grassland management, where we used either a unidirectional succession model for forest habitat or a rotation model with a period of forest growth followed by a clear-cut and a new successional cycle. The simulations indicated that P. veris populations may have an extinction time of decades to centuries after a detrimental management change. A survey of the current incidence and abundance of P. veris in sites with different histories of afforestation confirmed the simulation results of low extinction rates. P. veris had reduced incidence and abundance only at sites with at least 100 years of forest cover. Time to extinction in simulations was dependent on the duration of the periods with favourable and unfavourable conditions after management cessation, and the population sizes and growth rates in these periods. Our results thus suggest that the ability of a species to survive is a complex function of disturbance regimes, rates of successional change, and the demographic response to environmental changes. Detailed demographic studies over entire successional cycles are therefore essential to identify the environmental conditions that enable long-term persistence and to design management for species experiencing extinction debts.

Tolerance to herbivory is an adaptation that promotes regrowth and maintains fitness in plants after herbivore damage. Here, we hypothesized that the effect of competition on tolerance can be different for different genotypes within a species and we tested how tolerance is affected by competitive regime and damage type. We inflicted apical or leaf damage in siblings of 29 families of an annual plant Raphanus raphanistrum (Brassicaceae) grown at high or low competition. There was a negative correlation of family tolerance levels between competition treatments: plant families with high tolerance to apical damage in the low competition treatment had low tolerance to apical damage in the high competition treatment and vice versa. We found no costs of tolerance, in terms of a trade‐off between tolerance to apical and leaf damage or between tolerance and competitive ability, or an allocation cost in terms of reduced fitness of highly tolerant families in the undamaged state. High tolerance bound to a specific competitive regime may entail a cost in terms of low tolerance if competitive regime changes. This could act as a factor maintaining genetic variation for tolerance.

Landscape change is one of the most important anthropogenic processes affecting ecosystems. Historically, there have been several far-reaching transformations of Eastern and Northern European ecosystems due to agricultural transitions. The most recent one, due to the collapse of the Soviet Union, resulted in large-scale changes in rural landscapes of Eastern Europe. In many countries, over 20% of agricultural land was abandoned. The trend is especially strong in Estonia, where 54% of arable land was abandoned between 1992 and 2005. Land abandonment can affect a variety of ecosystem traits such as biodiversity, water supply, nutrient cycling and carbon sequestration. The outcome depends on the type of land abandoned and the management following abandonment. This chapter looks at its varied implications for environmental governance.

We tested whether differences in ploidy level and previous exposure to herbivory can affect plant tolerance to herbivory. We conducted a common garden experiment with 12 populations of two ploidy levels of the perennial herb Cardamine pratensis (five populations of tetraploid ssp. pratensis and seven populations of octoploid ssp. paludosa). Earlier studies have shown that attack rates by the main herbivore, the orange tip butterfly Anthocharis cardamines, are lower in populations of octoploids than in populations of tetraploids, and vary among populations. In the common garden experiment, a combination of natural and artificial damage significantly reduced seed and flower production. We measured tolerance based on four plant-performance metrics: survival, growth, seed production and clonal reproduction. For three of these measurements, tolerance of damage did not differ between ploidy levels. For clonal reproduction, the octoploids had a higher tolerance than the tetraploids, although they experience lower herbivore attack rates in natural populations. Populations from sites with high levels of herbivory had higher tolerance, measured by seed production, than populations with low levels of herbivory. We did not detect any significant costs of tolerance. We conclude that high intensity of herbivory has selected for high tolerance measured by seed production in C. pratensis.

In conservation management, there is an urgent need for estimates of population viability and for knowledge of the contributions of different life-history stages to population growth rates. Collection of long-term demographic data from a study population is time-consuming and may considerably delay the start of proper management actions. We examined the possibility of replacing a long-term temporal data set (demographic data from several years within a population) with a short-term spatial data set (demographic data from different populations for the same subset of two continuous years) for stochastic estimates of population viability. Using matrix population models for ten perennial plant species, we found that the matrix elements of spatial data sets often deviated from those of temporal data sets and that matrix elements generally varied more spatially than temporally. The appropriateness of replacing temporal data with spatial data depended on the subset of years and populations used to estimate stochastic population growth rates (log λs). Still, the precision of log λs estimates measured as variation in the yearly change of logarithmic population size rarely differed significantly between the spatial and temporal data sets. Since a spatiotemporal comparison of matrix elements and their variation cannot be used to assess whether spatial and temporal data sets are interchangeable, we recommend further research on the topic.

To study mechanisms underlying plant tolerance to herbivore damage, we used apical and foliar damage as experimental treatments to study whether there are similar tolerance mechanisms to different types of damage. We also studied whether tolerance to different types of damage are associated, and whether there is a cost involved in plant tolerance to different types of herbivore damage. Our greenhouse experiment involved 480 plants from 30 full-sib families of an annual weed Raphanus raphanistrum, wild radish, which were subjected to control and two different simulated herbivore damage treatments, apex removal and foliar damage of 30% of leaf area. Apical damage significantly decreased seed production, whereas foliar damage had no effect. There was a significant genetic variation for tolerance to foliar, but not apical damage. No costs were observed in terms of negative correlation between tolerance to either damage type and fitness of undamaged plants. Tolerances to apical and foliar damage were not significantly correlated with each other. We observed a larger number of significant associations between tolerance and reproductive traits than between tolerance and vegetative traits. Plant height and leaf size of damaged plants interacted in their association to tolerance to foliar damage. Inflorescence number and pollen quantity per flower of damaged plants were positively associated with tolerance to apical damage. In late-flowering genotypes, petal size of undamaged plants and pollen quantity of damaged plants were positively associated with tolerance to foliar damage. In summary, traits involved in floral display and male fitness were associated with plant tolerance to herbivore damage.

Maternal plant responses to different levels of pollination vary and are of importance for the total fitness of the plant. We studied how varying pollen load affects late flowering, reproduction, a ...

The evolution of flower size may be constrained by trade-offs between flower size and other plant traits. The aim of this study was to determine how selection on flower size affects both reproductive and vegetative traits. Raphanus raphanistrum L. was used as the study species. Artificial selection for small and large petal size was carried out for two generations. We measured the realized heritability of flower size and recorded flower production, time to flowering, plant size, and seed production in the two selection lines. The realized heritability was h2 = 0.49. Our study, therefore, showed that R. raphanistrum has potential for rapid evolutionary change of floral size. The lines with large flowers produced smaller seeds and started to flower later than the lines with small flowers. There was no trade-off between flower size and flower number, but the lines selected for large flower size had more flowers and a larger plant size than lines selected for small flowers. Estimates of restricted maximum likelihood (REML) analysis of pedigrees also showed that flower size had a positive genetic correlation with start of flowering and plant height.

Brominated aromatic compounds (BACs) are widely distributed in the marine environment. Some of these compounds are highly toxic, such as certain hydroxylated polybrominated diphenyl ethers (OH-PBDEs). In addition to anthropogenic emissions through use of BACs as e.g. flame retardants, BACs are natural products formed by marine organisms such as algae, sponges, and cyanobacteria. Little is known of the transfer of BACs from natural producers and further up in the trophic food chain. In this study it was observed that total sum of methoxylated polybrominated diphenyl ethers (MeO-PBDEs) and OH-PBDEs increased in concentration from the filamentous red alga Ceramium tenuicorne, via Gammarus sp. and three-spined stickleback (Gasterosteus aculeatus) to perch (Perca fluviatilis). The MeO-PBDEs, which were expected to bioaccumulate, increased in concentration accordingly up to perch, where the levels suddenly dropped dramatically. The opposite pattern was observed for OH-PBDEs, where the concentration exhibited a general trend of decline up the food web, but increased in perch, indicating metabolic demethylation of MeO-PBDEs. Debromination was also indicated to occur when progressing through the food chain resulting in high levels of tetra-brominated MeO-PBDE and OH-PBDE congeners in fish, while some penta- and hexa-brominated congeners were observed to be the dominant products in the alga. As it has been shown that OH-PBDEs are potent disruptors of oxidative phosphorylation and that mixtures of different congener may act synergistically in terms of this toxic mode of action, the high levels of OH-PBDEs detected in perch in this study warrants further investigation into potential effects of these compounds on Baltic wildlife, and monitoring of their levels.

The joint effects of multiple herbivores on their shared host plant have received increasing interest recently. The influence of herbivores on population dynamics of their host plants, especially the relative roles of different types of damage, is, however, still poorly understood. Here, we present a modelling approach, including both deterministic and stochastic matrix modelling, to be used in estimating fitness effects of multiple herbivores on perennial plants. We examined the effects and relative roles of two specialist herbivores, a pre-dispersal seed predator, Euphranta connexa, and a leaf-feeding moth, Abrostola asclepiadis, on the population dynamics and long-term fitness of their shared host plant, a long-lived perennial herb Vincetoxicum hirundinaria (Asclepiadaceae). We collected demographic data during 3 years and combined these data with the effects of natural levels of herbivory measured from the same individuals. We found that both seed predation and leaf herbivory reduced population growth of V. hirundinaria, but only very high damage levels changed the growth trend of the vigorously growing study populations from positive to negative. Demographic modelling indicated that seed predation had a greater impact on plant population growth than leaf herbivory. The effect of leaf herbivory was weaker and diminished with increasing level of seed predation. Evaluation of individual fitness components, however, suggested that leaf herbivory contributed more strongly to host plant fitness than seed predation. Our results emphasize that understanding the effects of a particular herbivore on plant population dynamics requires also knowledge on other herbivores present in the system, because the effect of a particular type of herbivory on plant population dynamics is likely to vary according to the intensity of other types of herbivory. Furthermore, evaluating herbivore impact from using individual fitness components does not necessarily reflect the long-term effects on total plant fitness. © 2005 Gesellschaft für Ökologie.

Large data requirements may restrict the use of matrix population models for analysis of population dynamics. Less data are required for a small population matrix than for a large matrix because th ...

1. Changes in land use are the primary cause of decline for many plant species. Efficient management actions for such species must be based on knowledge of the key phases of the plant life cycles t ...

An increasing number of studies have recently detected within-organism genetic heterogeneity suggesting that genetically homogeneous organisms may be rare. In this review, we examine the potential costs and benefits of such intraorganismal genetic heterogeneity (IGH) on the fitness of the individual. The costs of IGH include cancerous growth, parasitism, competitive interactions and developmental instability, all of which threaten the integrity of the individual while the potential benefits are increased genetic variability, size-specific processes, and synergistic interactions between genetic variants. The particular cost or benefit of IGH in a specific case depends on the organism type and the origin of the IGH. While mosaicism easily arise by genetic changes in an individual, and will be the more common type of IGH, chimerism originates by the fusion of genetically distinct entities, and is expected to be substantially rare in most organisms. Potential conflicts and synergistic effects between different genetic lineages within an individual provide an interesting example for theoretical and empirical studies of multilevel selection.

Trade-offs involving life span are important in the molding of plant life histories. However, the empirical examination of such patterns has so far been limited by the fact that information on life ...

Many plants show compensatory regrowth after herbivory and dormant buds often have an important role in compensatory responses. Theoretical models have shown that herbivore damage may select for a bud bank, i.e., a pool of dormant buds that are protected from herbivory and that are activated after herbivore damage. Earlier models assumed that undamaged plants cannot activate their dormant buds without damage, although they apparently have sufficient resources for successful seed production through the additional shoots dormant buds could produce. However, many plants are able to gradually activate buds over an extended period of time without any cue from damage. The aim of this study was to analyze how herbivory imposes selection for gradual mobilization of the bud bank. I assume that selection pressures that affect the fraction of buds active at each time point include damage by herbivores, time left to the end of season, and the opportunity costs of dormant buds. I modelled bud dynamics with gradual activation when there is a single damage event and (i) when the seed set of a shoot is not dependent on the time it is active, or (ii) when the seed set of a shoot diminishes with later activation. In addition, I analyzed how (iii) risk of repeated herbivory affects selection for gradual activation. Under these models, gradual activation is optimal over a wide range of herbivory pressures. Selection appears to favour activation of all buds at the beginning of the season only when herbivore pressure is weak and when early shoots have a higher seed set than late shoots. Alternatively, strong herbivore pressure and late damage may select for a large bud bank throughout the growing season, without gradual activation; the bud bank is only mobilized after damage. In this case, damaged plants can overcompensate, i.e. they have a higher seed set than undamaged plants with the same bud activation pattern. Selection for overcompensation demands a stronger herbivore pressure in this current model than in earlier bud bank models. The model never predicts selection for overcompensation when there is a risk of repeated herbivory.

We conducted three experiments in which we applied additional hand pol- lination, flower removal, and leaf removal treatments in various combinations to Primula veris, a perennial spring-flowering rosette species. The purpose of the study was to determine whether the seed set of Primula veris was limited by pollen availability or by other resources, and whether there were measurable costs of reproduction. Hand pollination in the beginning of experiments significantly increased current seed set in only one of the three experiments. It also increased the next-year fruiting probability in that first experiment. In the second experiment, hand pollination did not significantly affect current seed set, but we nevertheless observed enhanced leaf growth in the treatment year and the two following years, and increased flowering frequency, fruiting frequency, and survival in the two following years. In the third experiment, after hand pollination we observed a higher net photosynthetic capacity of the leaves and, again, increased leaf growth in the treatment year and a higher flowering probability in the following year. The positive effect of hand pollination was even clearer when the leaves of the plants were removed at the beginning of the experiment. However, the treatment in which all the flowers were removed had effects on subsequent performance similar to those of the hand-pollination treatment, suggesting trade-offs. Thus, we did not observe any costs associated with reproduction after supplemental hand pollination; on the contrary, hand pollination resulted in increased survival, size, and reproduction of the plants in the subsequent years.

The aim of this study was (1) to evaluate the importance of dormant buds for the bud demography of the mountain birch Betula pubescens ssp. tortuosa near the tree line and (2) to study whether sexual reproduction leads to costs for bud production rates. A bud population census was taken in two consecutive years for six branches of each of 90 mountain birch trees. The trees were growing in a common garden and belonged to 10 different progenies originating from different parts of Finnish Lapland. The data were analyzed with matrix population models. The most important transformations of the bud populations were between vegetative short and long shoots. However, if most apparently dead buds are actually latent dormants, they make an even more important contribution to the bud population growth rate than vegetative long and short shoots. Dormant buds may have considerable importance especially after events such as herbivore outbreaks, in which short and long shoots are damaged. Generative long shoots (with male catkins) and short shoots (with female catkins) had approximately the same bud production rate as the corresponding vegetative shoots, i.e., bud populations did not show any major costs due to sexual reproduction. Meristem costs, i.e., a decrease in the number of buds due to sexual reproduction, may be relatively low in mountain birch, because new axillary buds develop and compensate for lost shoot apices. This compensation capacity may be especially well developed under suboptimal conditions, where canopy expansion is limited by the harsh environment rather than by the availability of meristems. The resource cost of reproduction (e.g., in terms of carbon or mineral nutrients) may also be partly compensated especially when flowering intensity is sufficiently low.

We studied the consequences of human disturbance and gull predation on brood survival of velvet scoter Melanitta fusca in the Archipelago of South-West Finland in 1990 and 1991. Each brood was exposed to disturbance by boats on average 8·5 times a day in 1990 and 3·5 times a day in 1991. Disturbance lengthened the swimming distances of ducklings and reduced the time used for feeding. Broods disturbed more frequently than average were smaller than those disturbed less frequently. At least 60% of ducklings died before the age of three weeks. The common predators of ducklings in the study area are the herring gull Larus argentatus and the great black-backed gull Larus marinus . The daily predation rate by gulls on velvet scoter ducklings was 4·7%, which means that 56% of ducklings are caught by gulls during the first three weeks. The frequency of gull attacks was 3·5 times higher in disturbed than in undisturbed situations.

Ten years ago, the question of forage use by moose largely focused on whether nutritive factors or secondary compounds determined their use of individual tree species. Today, it is clear that both are important. Research during the last few years has tried to explain the hierarchical decisions in the foraging patterns of moose.

Artificial damage is a popular method in plant-herbivore studies, because the use of real herbivores is often laborious and because it may be virtually impossible to use herbivores in many experimental setups. We made a literature search of studies that tested whether natural and artificial damage have similar effects on plants. Of 46 studies found, 33 (72%) reported a significant difference between responses to artificial and natural herbivore damage in at least one of the statistical tests included. The studies contained 280 statistical tests, of which 99 (35%) showed a significant difference between artificial and natural damage. Phytochemical responses to artificial and natural damage were different in 41% of the statistical tests and 75% of the studies found at least one significant difference. Plant resistance, measured as secondary damage, herbivore performance, fungal growth in damaged tissue or plant attractivity to parasitoids of herbivores, differed in 60% of the statistical tests and 85% of the studies had significant differences. Growth, reproduction and physiological responses to artificial and natural damage differed in 20–30% of statistical tests and 50–83% of studies had significant differences. Thus, studies on plant tolerance (growth and reproduction after damage) more often showed similar effects for artificial and natural damage than studies on plant resistance to herbivory, but even in tolerance studies artificial and natural damage often have different effects. Some studies indicated that application of herbivore saliva and careful imitation of timing and spatial pattern of damage helped in reaching the same effect with simulations and natural damage.

11 páginas, 3 figuras, 3 tablas, 1 dibujo.-- et al., [EN]: 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., [ES]: Aunque los efectos de factores determinísticos sobre la viabilidad poblacional a menudo son más importantes que la estocasticidad, pocos investigadores han abordado el efecto de los cambios determinísticos del hábitat sobre la demografía de poblaciones de plantas. Evaluamos la viabilidad poblacional de la hierba perenne Primula veris L. e identificamos objetivos para su gestión con base en datos demográficos obtenidos en cinco tipos de hábitat diferentes que representan diferentes grados de oclusión del dosel. Realizamos estudios replicados en el límite del área de distribución y en áreas más centrales. Los patrones demográficos eran similares en las dos regiones. La mayoría de las poblaciones estudiadas tenían un crecimiento poblacional positivo, y solo mostraron tendencias consistentemente negativas las poblaciones en fases avanzadas de sucesión del bosque. Las poblaciones en hábitats abiertos tenían alto reclutamiento de plántulas, y las poblaciones en bosques en sucesión temprana y media tenían alta producción de semillas. La importancia de la supervivencia para la tasa de crecimiento poblacional aumentó con el incremento de la oclusión del hábitat, mientras que disminuyó la importancia del crecimiento y la reproducción. Los resultados del análisis de elasticidad sugieren que el mejor método para manejar poblaciones decrecientes de etapas tardías de sucesión es el incremento de la supervivencia de los individuos más grandes. Sin embargo, el análisis de experimento de respuesta de tabla de vida (ERTV) mostró que la supervivencia de los individuos más grandes contribuyó poco a las diferencias en las tasas de crecimiento poblacional en hábitats diferentes, mientras que la producción de semillas y el crecimiento de individuos pequeños fueron más importantes. Más aun, la perturbación directa del funcionamiento de las etapas mayores mostró que las poblaciones de sucesión tardía no llegarían a tener crecimiento poblacional positivo aun si no hubiera mortalidad en las etapas mayores. Concluimos que la restauración del reclutamiento es la única posibilidad de crecimiento poblacional en poblaciones de P. veris de sucesión tardía, aunque las elasticidades de las transiciones de reclutamiento sean bajas. Nuestros resultados también sugieren que los métodos demográficos retrospectivos, como ERTV, constituyen un complemento necesario e importante de los métodos prospectivos, como las elasticidades, en la identificación de objetivos de conservación., The study was financed by World Wide Fund of Sweden, the Swedish Research Council (to K.L. and J.E), the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS) (to J.E.), Östersjöstiftelsen (to K.L.), and a postdoctoral grant from the Spanish Ministerio de Educación y Ciencia MEC (to M.B.G; ref. EX94 17713636).

Publisher Summary The principle of resource allocation states that resources are not sufficient to fully supply the demands of all plant functions. If resources are limited, allocation to reproduction must decrease the allocation to some other plant functions. Allocation of resources to reproduction (reproductive allocation) has implications for several study fields in biology. Early studies discussed allocation patterns in light of the evolution of life-history traits and interaction between life-history traits and population dynamics. Initial studies considered animals, but the idea was soon applied to plant ecology to explain how allocation affects plant life-history strategies and plant community dynamics. To test the principle of allocation, biologists have tried to measure the resource use of different plant functions. This task has turned out to be difficult. It is not clear which currency should be used to measure reproductive allocation. Meristems have been proposed as a currency to measure reproductive allocation. Meristems come as distinct reproductive or vegetative entities. This chapter aims to discuss whether meristem allocation can be used as a supplement or a substitute when studying reproductive allocation. It first describes the structural, developmental, and physiological background of the meristem system. It then uses a modeling approach to show theoretically how meristem allocation may affect fitness. It discusses model assumptions and reviews empirical studies that have tested allocation models and their assumptions.

We devise a stochastic and spatially explicit model for the dynamics of the initials cells in a stratified shoot apical meristem (SAM). The meristem is composed of three layers with seven initials per layer. We investigate the probability and number of divisions for a mutant lineage to either reach fixation or becoming purged through selection or drift. In contrast to previous studies our results show that the functional organization of the initials in stratified SAMs acts as an efficient purging mechanism particularly of deleterious mutations. All mutants are rapidly purged when deleterious. The probability of fixation for mutants with a higher fitness than the wild type increases linearly up to 70%. The median number of divisions to fixation of both genotypes is insensitive to the mutant's fitness. The median number of divisions to wild-type fixation is less than 100, with the upper quartile below 200. The largest number of divisions to wild-type fixation are in the order of 100 000 divisions. Our results indicate that the spatial organization of SAM enables the efficient purging of mutant lineages, particularly if they are deleterious. On the other hand, long-lived chimeric stages are common when mutant lineages succeed to overcome the initial numerical disadvantage.

Introduction: Destruction of vegetation resources emanating from deposition of mine wastes is a serious environmental problem. Conventional plant species restoration methodologies are costly and fe ...

The geographic mosaic theory of co-evolution states that evolution of interactions is driven by geographical variation in interactions between species. We investigated whether the intensity of pre-dispersal seed predation differed among nine Primula veris populations over 5 years, and whether such differences lead to geographical variation in selection on flower number. Seed predation intensity differed significantly among years and populations, and it increased with canopy closure and decreased with the density of the field layer vegetation. Individuals in open habitats also produced the highest number of flowers. Moreover, the phenotypic selection on flower number differed among years and populations. In populations of closed habitats, with high seed predation pressure, the increased number of flowers was often correlated with an increased number of damaged capsules. However, an increased flower number did not result in fewer intact fruits due to seed predation in any population.

Tiffin and Inouye (2000) discussed the use of natural and imposed (controlled) damage in experiments of herbivore tolerance. They constructed a statistical model of the effect of herbivory on plant fitness, including damage level and an environmental factor as the independent factors, in which tolerance is defined as a slope of the regression line when damage level is regressed with plant fitness. They claim that while experiments with imposed damage are more accurate (i.e., they give a more correct estimate of tolerance), experiments with natural damage are more precise under a wide range of parameter values (i.e., tolerance estimates explain a larger part of variation in fitness). I show, however, that experiments with imposed damage are less precise only when an experimenter uses an experimental design that has weaker statistical power than in experiments with natural herbivory. The experimenter can nevertheless control the damage levels to optimize the experimental designs. For instance, when half of the experimental plants are left undamaged and the other half treated with maximal relevant damage level, experiments with imposed damage are almost always much more precise than experiments with natural damage.

Most damage caused by invertebrate herbivores is local and limited in extent and may therefore seem inconsequential. However, in addition to providing photosynthates to the whole plant, individual leaves may preferentially feed local sinks, including pri- mordial meristems that develop later. For leaf damage, this may have local consequences and, in the case of preformed meristems, may result in time lags. To investigate such consequences and to determine the degree of independence among shoot modules, we studied shoot traits after damage to individual leaves in long shoots and vegetative and generative short shoots of field-growing mountain birch, Betula pubescens subsp. czere- panovii (Orlova) Hamet-Ahti. For short shoots, the results suggest that, due to the catkin, generative shoots have a higher priority in resource use than vegetative shoots. The overwinter survival of vegetative short shoots was decreased after their young leaves had been damaged early in the previous season. Otherwise, there were no significant effects of leaf damage on vegetative shoots. In generative shoots, leaf damage affected size and reproduction instead of survival. Because leaf damage significantly decreased leaf size-in the generative shoots in the posttreatment year, leaves presumably competed with the catkin for resources within the shoot. Damage also reduced the catkin mass and the mean seed mass in the treatment year. In the post- treatment year, catkin mass and total seed mass were reduced by the treatments, but dif- ferences in the number of seeds and mean seed mass did not quite reach significance. The treatments had no effects on leaf mass of neighbors of vegetative or generative shoots in the treatment year or in the posttreatment year. In the treatment year, removal of long shoot leaves from a growing long shoot did not affect growth of the long shoot, indicating that such growth was supported by resources external to the shoot. However, local effects were evident in the posttreatment year: leaf mass decreased in shoots that developed from axillary buds in long shoots whose supporting leaves had been clipped in the previous year. Consequently, removal of individual leaves may have local effects on shoot survivorship, reproduction, and growth. Timing of damage and shoot type modified the consequences of local leaf damage, and there were no consistent responses for all situations. Due to the limited extent of damage, the effects were not likely to result from nutrient loss due to damage. Instead, consequences of local leaf damage could be explained largely by effects on local sinks and meristem primordia.

The effect of flower and leaf removal on Primula veris was studied in two populations close to each other. Removal of both flowers and leaves resulted in decreased growth, flowering and reproduction in the next two years in both populations; there was no change in survival. In one population, removal of all flowers increased the flower number, the flower stalk length and the leaf area, and doubled the seed set in the year following the treatment. In the other population flower removal slightly decreased the seed set in the next year, while plant size did not differ from the control group. There were no significant differences in seed germinability between any of the experimental groups

Because the impact of induced resistance on herbivores is often too small to have a considerable impact on herbivore populations, it has been suggested that the function of defenses is not necessarily to affect herbivore densities per se, but to spread the damage evenly throughout a plant. Some observations suggest that evenly-distributed herbivory results in a smaller decrease in growht and reproduction than the same level of herbivory concentrated on only one part of the canopy. One possible reason for this is that plant parts are able to compensate for small amounts of local damage spread all over the plant but not for larger concentrated damage of the same extent because of the of resource distribution patterns in a plant. Models were constructed to analyze how to optimally distribute damage among modules so that the total performance (growth, subsequent reproduction) of a plant, measured as the sum of the module performances, is maximized. According to the models, spreading damage is profitable when the performance of all or most modules decreases slowly with small damage levels and then faster as damage increases. In addition, the pattern of resource movement between modules must be tolerant to damage. It is proposed a hypothesis that the resource distribution system is often tolerant to at least small or moderate total damage levels, since there are several alternative pathways of movement for assimilates and water through the plant's structure. It has been suggested that defense and compensatory growth are alternative strategies for a plant in the struggle against herbivores. The present models suggest that they can also work together to increase fitness under herbivore pressure.

As a response to browsing, birches are known to produce fewer but larger, more nutritious leaves, with enhanced palatability for herbivores. We simulated winter browsing in ramets of mountain birch (Betula pubescens ssp. czerepanovii) to find out whether it decreases subsequent foliage biomass and alters the number and type of shoots. After removal of a considerable proportion of buds (up to 35%) in late winter, the birches were able to compensate for the lost leaf biomass in the following summer; there were no differences in total leaf biomass between winter-clipped and control ramets. This indicates that foliage growth was limited by the total amount of stored resources, not by the number of buds. Depending on the position of the buds removed, different mechanisms were responsible for the compensation. After removal of apical buds, the number of leaves decreased significantly but leaves were larger than in control ramets. Removal of the same mass of basal buds – containing similar amount of carbohydrates and proteins as in the treatment removing apical buds – activated dormant buds, especially in apical locations, so that leaf number was similar as in the controls; consequently, size of individual leaves increased only slightly. Thus, while the total leaf biomass in a tree seems to be limited by resources from source organs, the distribution of resources among different canopy sections is controlled by their relative sink strengths. In terms of leaf biomass, apical parts are able to compensate for bud loss by increasing shoot number, basal parts only by increasing leaf size.