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Recruitment limitation is known to influence species abundances and distributions. Recognition of how and why it occurs both in natural and in designed environments could improve restoration. Aquatic insects, for instance, rarely reestablish in restored streams to levels comparable to reference streams even years after restoration. We experimentally increased oviposition habitat in five out of 10 restored streams in western North Carolina to test whether insect egg-laying habitat was limiting insect populations in restored streams. A main goal was to test whether adding oviposition habitat in the form of rocks that partially protrude above the water surface could be used to increase the abundance and richness of stream insect eggs and larval insects in restored streams. Adding egg-laying habitat enhanced several response variables (e.g., protruding rocks, number of eggs, egg masses, egg morphotype richness, and oviposition habitat stability) to levels similar to those found in reference streams. Following the addition of protruding rocks, egg mass abundance increased by 186% and richness by 77% in restored-treated streams. Densities of larval insects that attached their eggs to protruding rocks showed an overall pattern consistent with treatment effects due to the combination of nonsignificant and significant increases of several taxa and not just one taxon. Our results indicate that these stream insect populations are limited by oviposition habitat and that adding egg-laying habitat alleviated this component of recruitment limitation. However, the weaker larval response indicates that additional post-recruitment factors, such as egg or larval mortality, may still be limiting a full recovery of larval insect abundances in these restored streams. This study shows the importance of integrating information from animal life histories, ecology, and geomorphology into restoration practices to improve the recovery of aquatic insects, which are commonly used to assess water quality and the biological efficacy of stream restoration. [ABSTRACT FROM AUTHOR]

One important goal in prairie restorations is to have forb species that flower throughout the growing season (i.e. a range of flowering phenology). We conducted an experiment to test whether three early‐ and three late‐flowering forb species are seed or recruitment limited, if mowing can influence this limitation, and if forb additions will impact overall plant diversity in ongoing restorations.The experiment was conducted at two restorations in northern Iowa and one in southern Minnesota, USA, using a split‐plot design. Whole plots tested the effect of mowing, and subplots tested the effect of target forbs being added as seeds or small transplants at varied richness levels (0, 1, 3 or 6 species added). Control plots received no forb additions. To compare establishment success, we estimated target species biomass, survivorship and per cent cover of target species across 3 years (2019–2021). Plant diversity measures (richness, inverse Simpson's diversity) were estimated within subplots to determine whether forb additions impacted diversity.Biomass and relative abundance of early‐ and late‐flowering forbs was much higher when they were added as transplants than when added as seeds. Survivorship across life stages indicated that the transition from seed to adult had lower survivorship probabilities (0.6%) than the transition from transplant (juvenile) to adult (75%).Plant diversity of these ongoing restorations was higher when target forbs were added compared to controls. Diversity was higher when target forbs were transplanted (8.4 species/plot and inverse Simpson's diversity of 4.0) than when they were seeded (7.6 species/plot and inverse Simpson's diversity of 3.8). Early‐flowering treatments increased diversity more than late‐flowering treatments, and diversity increased linearly with the number of forb species added.Mowed and unmowed plots had similar levels of target species establishment and plant diversity.Synthesis and applications: Our results indicate that early‐ and late‐flowering species are more recruitment limited than seed limited and that diversity is lower when these species are missing in restorations. We recommend transplanting a rich mix of early‐ and late‐flowering forbs to increase their biomass and ensure that flowering occurs throughout the growing season. [ABSTRACT FROM AUTHOR]

Context: Silver banksia (Banksia marginata) savannas of south-eastern Australia were formerly widespread but are now largely cleared and fragmented, with small populations often showing recruitment limitation. Which may, in part, be due to seed predation by yellow-tailed black cockatoos (Zanda funerea), which have been observed foraging for seed. Aims: The study aimed to investigate the impact of pre-dispersal seed predation by yellow-tailed black cockatoos on fruit crop between early development and seed release. Additionally, we wanted to assess seed fitness from partially damaged and discarded cones. Methods: The study quantified silver banksia infructescence removal at four populations between early December and seed release in March. We also quantified seed mass and germinability of seeds from cones removed in December, February and March. Key results: All populations experienced significant seed predation (>50%), with almost complete removal of cones from some populations. Early removal limits seed release from cones (only 18% of early removed follicles released seed). Further, early removal also significantly reduced seed mass and germination. Conclusions: Pre-dispersal seed predation by cockatoos is likely to act as a strong filter for recruitment limitation in silver banksia, by negatively affecting annual seed crop size, seed fitness and germinability. Implications: Our study showed the potential impact fragmentation can have on antagonistic plant–animal interactions. Small, isolated B. marginata populations are likely to continue to decline without active strategies to remedy seed predation such as large-scale restoration. Photograph showing development stages of the infructescence and follicles. Fragmentation can interrupt many plant–animal interactions with lasting effects on plant populations. Silver banksia is a highly fragmented but functionally important tree species and important food plant for yellow-tailed black cockatoos. In this study, we document exceptionally high rates of seed predation, development-dependent failure of follicle release from discarded cones, and reduced seed fitness of discarded seeds in fragmented populations of silver banksia. [ABSTRACT FROM AUTHOR]

IntroductionThe Mediterranean is the European region with the lowest woody cover and the highest level of habitat degradation, being highly susceptible to climate change effects and desertification risk. In such worrying conditions, increasing woody cover and restoring forests is a major goal established in several international commitments. However, recruitment limitation of woody species is rather frequent both within natural regeneration processes and active restoration programs, particularly due to drought, overgrazing, and a lack of post-planting tending operations. Therefore, finding suitable tools to improve the recruitment success of native woody species is of crucial importance.MethodsWe assessed woody natural regeneration under abandoned prickly pear orchards, olive trees, and nearby open areas in three sites under high desertification risk in central Sicily (Italy). Then, we tested for differences in density, richness, diversity, height, and basal diameter of the woody recruiting species between these three habitats.Results and discussionNatural regeneration was widespread under prickly pear, with 94.6% of the sampled plots showing at least one recruit, in comparison to 61.6% of plots under olive and 22.3% in open areas. Natural regeneration density under prickly pears (114 ± 99 individuals m−2) was significantly higher (p

Copyright of Forest Research is the property of Forest Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Planktonic larvae are thought to be very susceptible to offshore advection in upwelling regimes, increasing dispersal and decreasing recruitment. However, larvae of 42 species of nearshore benthic crustaceans primarily developed on the inner shelf at locations both in (98.5%) and away (99.8%) from a perennial upwelling center in the upwelling season of a recruitment-limited region characterized by persistent, strong, upwelling. During three cross-shelf cruises conducted at each location, larvae of 21 species remained on the inner shelf at both sites by occurring beneath seaward-flowing surface currents while larvae of other species migrated to midshelf (four species) or offshore (14 species) by initially developing near the surface. Postlarvae apparently returned to shore either deep in landward-flowing upwelled water or near the surface where behavior allows them to be transported shoreward by internal waves, diel wind cycles or wind relaxation events. Thus, recruitment limitation in upwelling regimes does not appear to be caused by larval mortality from offshore transport, requiring new research directions to advance our understanding of population dynamics, structure and connectivity.

Predicting how forest species composition may change in response to global change is essential for meaningful management. Which species are most likely to successfully recruit depends on a multitude of factors, but processes operating at the seed-toseedling transition being especially important. Here, we explore how insufficient seed dispersal (dispersal limitation) and ecological filtering of seedlings (establishment limitation) influence species recruitment in an Afromontane Forest. We combined census data from seeds in seed traps and seed-seedling transition plots in a Nigerian montane forest to measure dispersal and establishment limitation across species, life history strategies, and seed sizes. From 106 seed traps and 318 seedling plots, we recorded 11,278 seeds from 38 species and 2688 seedlings of 61 species. All species except for one liana showed strong dispersal limitation while 23 out of the 30 species showed establishment limitation. The two lianas sampled had significantly lower dispersal limitation compared to the trees investigated in the study. Our results suggest that both dispersal and establishment limitation are markedly high in this Afromontane forest than would be expected in a lowland counterpart. [ABSTRACT FROM AUTHOR]

In organisms with complex life cycles, the various stages occupy different habitats creating demographically open populations. The dynamics of these populations will depend on the occurrence and timing of stochastic influences relative to demographic density dependence, but understanding of these fundamentals, especially in the face of climate warming, has been hampered by the difficulty of empirical studies.Using a logically feasible organism, we conducted a replicated density‐perturbation experiment to manipulate late‐instar larvae of nine populations of a stream caddisfly, Zelandopsyche ingens, and measured the resulting abundance over 2 years covering the complete life cycle of one cohort to evaluate influences on dynamics.Negative density feedback occurred in the larval stage, and was sufficiently strong to counteract variation in abundance due to manipulation of larval density, adult caddis dispersal in the terrestrial environment as well as downstream drift of newly hatched and older larvae in the current. This supports theory indicating regulation of open populations must involve density dependence in local populations sufficient to offset variability associated with dispersal, especially during recruitment, and pinpoints the occurrence to late in the larval life cycle and driven by food resource abundance.There were large variations in adult, egg mass and early instar abundance that were not related to abundance in the previous stage, or the manipulation, pointing to large stochastic influences. Thus, the results also highlight the complementary nature of stochastic and deterministic influences on open populations. Such density dependence will enhance population persistence in situations where variable dispersal and transitioning between life stages frequently creates mismatches between abundance and the local availability of resources, such as might become more common with climate warming. [ABSTRACT FROM AUTHOR]

Copyright of Biotropica is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Understanding what regulates population sizes of organisms with complex life cycles is challenging because limits on population sizes can occur at any stage or transition. We extend a conceptual framework to explore whether numbers of successfully laid eggs determine densities of later stages in insects, fish, amphibians, and snails inhabiting marine, freshwater, or terrestrial habitats. Our review suggests novel hypotheses, which propose characteristics of species or environments that create spatial variation in egg densities and predict when such patterns are maintained throughout subsequent life-cycle stages. Existing data, although limited, suggest that persistent, strong associations between egg and subsequent juvenile densities are likely for species where suitable egg-laying habitat is in short supply. Those associations are weakened in some environments and for some species by density-dependent losses of eggs or hatchlings. Such cross-ecosystem comparisons are fundamental to generality in ecology but demand place-based understandings of species' biology and natural history. [ABSTRACT FROM AUTHOR]

Question: Limited funds and compressed timelines frequently translate into a reliance on seed banks for native plant recovery following invasive plant management. This approach assumes: (a) baseline seed bank communities are sufficient for native plant recovery regardless of site environmental conditions; (b) different management actions variably impact native and invader seed banks; (c) management actions reduce invader seed banks; while (d) native seed banks do not decline following management; and (e) returning above‐ground vegetation reflects the seed bank. Do these assumptions hold true in the context of invasive Phragmites australis management? Location: Great Salt Lake wetlands, Utah, USA. Methods: Across six sites, we applied six Phragmites management treatments (solarization, or glyphosate or imazapyr herbicide in the summer or fall with mowing) for three years, and monitored two more. Each year, we assessed the above‐ground vegetation and seed bank using the seedling emergence method. Results: Site environmental conditions drove baseline seed bank communities: seed banks differed substantially across sites with varying anthropogenic degradation as less disturbed sites had greater seed bank richness. Different management actions had similar impacts on native and invader seed banks. Phragmites seed density was reduced after herbicide treatments while native seed bank communities were unaffected. Above‐ground vegetation generally reflected seed bank communities. However, native graminoids were present in seed banks but surprisingly rare above‐ground. Conclusion: Commonly held assumptions about invasive plant management and native recovery from the seed bank did not all hold true. Native seed banks were particularly insufficient for recovery at sites with greater degradation, suggesting managers should prioritize management at less degraded sites or consider revegetation in highly degraded sites. Despite reductions in Phragmites seed bank density, Phragmites propagule pressure remained high, requiring a long‐term management commitment. Often seed banks are insufficient and revegetation of desired above‐ground species is necessary to meet restoration goals. [ABSTRACT FROM AUTHOR]

Larval supply determines year-class strength of fisheries and complex ecological interactions among adults of benthic marine species. In upwelling regions, a latitudinal cline in the intensity and persistence of upwelling is thought to affect larval advection and recruitment, thereby regulating the intensity of interactions in adult populations and communities. We tested this hypothesis by determining the monthly cross-shelf abundances of nearshore benthic crustacean larvae throughout development during the peak upwelling season for 7 years in a region of intermittent upwelling and high recruitment (45°N). We tested whether larvae were found farther offshore during upwelling conditions, and we compared their interspecific cross-shelf distributions to previous results from a region of strong, persistent upwelling (38°N). We also compared larval abundances across the 2 upwelling regions for 1 year. Most species were retained nearshore, regardless of intra- and inter-annual variations in the intensity of upwelling. In both upwelling regions, larvae of each species consistently occurred at different distances from the shore. Further, there were no differences in nearshore larval abundance across upwelling regions for all but 1 larval stage of 1 species. Thus, latitudinal variations in the intensity and persistence of upwelling do not appear to affect larval survival, providing further evidence that nearshore processes may be a primary determinant of larval delivery to the rocky intertidal across these regions. © Inter-Research 2014.

Land‐use change threatens biodiversity in tropical landscapes, but its impact on rainforest regeneration remains poorly known. In fact, the landscape‐scale patterns driving the diversity of regenerating plants within forest fragments have been rarely explored, and we are uncertain whether such drivers vary across regions with different land‐use change patterns.We assessed the effect of landscape composition (forest cover and matrix openness) and configuration (forest patch density) on species diversity of sapling assemblages (trees ≥30 cm height and <1 cm diameter) in old‐growth forest fragments from three Mexican rainforest regions with different disturbance levels (n = 20 landscapes per region). We separately assessed old‐growth forest specialists (OGS) and forest generalist (FG) species to test the hypotheses that: (a) OGS species show recruitment limitation ('loser' species), and can therefore be negatively impacted by landscape changes, especially by forest loss and matrix openness in more deforested regions; and (b) FG species can regenerate and even proliferate in more disturbed landscapes ('winner' species).We recorded ~24,000 plants from 415 species. Landscape composition showed stronger effects than landscape configuration. The diversity of OGS species generally decreased in more deforested landscapes dominated by open matrices, and FG species followed the opposite response, especially in the regions with high‐to‐intermediate degree of disturbance. Overall, forest fragmentation (patch density) showed weak or no effects on species diversity, especially after controlling for forest cover effects (i.e. fragmentation per se). In contrast to the fragmentation threshold hypothesis, the effect of fragmentation was independent of the regional context. Moreover, FG species were affected by landscape attributes operating at larger scales than OGS species.Synthesis. Our findings support our hypotheses, and suggest that forest loss and matrix openness, not fragmentation per se, can cause the recruitment failure of tree assemblages in highly deforested rainforests. This can be related to source and dispersal limitation in more deforested landscapes with treeless matrices. Therefore, to promote the regenerative potential (resilience) of forest patches in human‐modified tropical landscapes, conservation programs should focus on preventing forest loss (even the smallest forest patches) and improving matrix quality with treed elements, particularly in highly deforested tropical regions. [ABSTRACT FROM AUTHOR]

Larvae are considered to be highly susceptible to offshore transport, thereby limiting recruitment in productive upwelling regions, except in the recirculation features that form in the lee of headlands. We show that 19 of 20 taxa of nearshore crustaceans were at least as common on the open coast as they were in the lee of a headland in a recruitment-limited region characterized by strong upwelling. Nine of these taxa occurred in high concentrations throughout development, indicating that larvae completed development nearshore in a coastal boundary layer of reduced Ekman transport. Larvae of 9 more taxa were prevalent as early stage larvae, and later stages were uncommon, indicating that larvae migrated offshore. The relative abundance of larval stages largely matched the vertical distributions of larvae in this study and a previous cross-shelf survey at this site, indicating that larval behavior plays a substantial role in determining whether larvae complete development nearshore or migrate offshore later in development. Larvae of taxa that occurred nearshore in high concentrations throughout development resided below a shallow Ekman layer of seaward-flowing surface waters, whereas most larvae of the other taxa occurred closer to the surface. Whether larvae undertook ontogenetic and diel vertical migrations also appeared to determine whether they were retained nearshore. Thus larval retention may be more widespread in upwelling regions than is widely believed, and the cause of recruitment limitation along upwelling coasts needs to be determined to further advance our understanding of the connectivity, dynamics and structure of coastal populations. © Inter-Research 2010.

Seed predation and seed dispersal can have strong effects on early life history stages of plants. These processes have often been studied as individual effects, but the degree to which their relative importance co-varies with seed predator abundance and how this influences seed germination rates is poorly understood. Therefore, we used a combination of observations and field experiments to determine the degree to which germination rates of the palm Astrocaryum mexicanum varied with abundance of a small mammal seed predator/disperser, Heteromys desmarestianus, in a lowland tropical forest. Patterns of abundance of the two species were strongly related; density of H. desmarestianus was low in sites with low density of A. mexicanum and vice versa. Rates of predation and dispersal of A. mexicanum seeds depended on abundance of H. desmarestianus; sites with high densities of H. desmarestianus had the highest rates of seed predation and lowest rates of seed germination, but a greater total number of seeds were dispersed and there was greater density of seedlings, saplings, and adults of A. mexicanum in these sites. When abundance of H. desmarestianus was experimentally reduced, rates of seed predation decreased, but so did dispersal of A. mexicanum seeds. Critically, rates of germination of dispersed seeds were 5 times greater than undispersed seeds. The results suggest that the relationship between A. mexicanum and H. desmarestianus is a conditional mutualism that results in a strong local effect on the abundance of each species. However, the magnitude and direction of these effects are determined by the relative strength of opposing, but related, mechanisms. A. mexicanum nuts provide H. desmarestianus with a critical food resource, and while seed predation on A. mexicanum nuts by H. desmarestianus is very intense, A. mexicanum ultimately benefits because of the relatively high germination rates of its seeds that are dispersed by H. desmarestianus.

Questions: Community assembly in regenerating forests is a key topic in ecology. Most studies examine the assembly process, assessing adult individuals along the forest succession. Although the adult stage is the final outcome of the assembly process, both abiotic and biotic filters can affect community assembly during early ontogenetic stages. Here, we investigate whether the functional composition and trait assembly patterns (trait convergence or divergence) change across ontogenetic stages along regenerating forest stands exposed to precipitation and chronic anthropogenic disturbance (CAD) gradients. Location: Caatinga dry forest, Catimbau National Park, Pernambuco, Brazil. Methods: Seeds (rain and bank), seedlings and adults of woody plant species were recorded across 15 forest regenerating stands (4–70 years since land abandonment) exposed to precipitation and CAD gradients. Seven functional traits related to species dispersal, establishment and resource use were measured for adult individuals and used to calculate the trait values for seeds and seedlings. Twenty old‐growth forest stands were used as a regional flora. Results: Functional composition (community weighted mean, CWM) varied across ontogenetic stages as wood density increased from seeds to seedlings, while seed mass increased from seeds to both seedlings and adults. The CWM also varied along precipitation/disturbance gradients but not along forest regeneration regardless the ontogenetic stage. Among seeds, dispersal distance increased towards wetter forest stands and decreased towards disturbed sites, while adult wood density increased from drier to wetter regenerating forest stands. Traits converged along the precipitation gradient but not in response to time since land abandonment. Conclusions: Caatinga dry forest regeneration is functionally structured across ontogenetic stages mediated mostly by water availability, but not over time since land abandonment. The effect of water availability on forest regeneration across ontogenetic stages highlights the complexity of species assembly in human modified landscapes, imposing important consequences considering the expected increasing aridity in the Caatinga. [ABSTRACT FROM AUTHOR]

Seed dispersal service is the proportion of plant species dispersed by a given disperser. It is important since seed dispersal enables colonisation of new habitats, and because movement of seeds even short distances away from trees can reduce vulnerability of seeds and seedlings to disease, predation and density-dependent effects that occur in the immediate vicinity of parent trees. In New Zealand, indigenous large-fruited canopy tree species are susceptible to recruitment failure because Hemiphaga novaeseelandiae (kererū; Columbidae) is the only widespread avian frugivore capable of swallowing large fruit and dispersing their seeds, and its survival relies on ongoing predator control. In view of the critical nature of this mutualism, seed dispersal service was assessed by measuring the difference in composition of seeds of indigenous large-fruited canopy tree species that were dispersed by H. novaeseelandiaeto under the canopies of co-fruiting large-fruited canopy tree species across the Auckland region in New Zealand. If seed dispersal were effective, seeds of all species should be found under the canopies of all tree species, i.e. low beta diversity of seed rain. Beta diversity was higher than expected at two locations, suggesting incomplete seed dispersal service; this pattern was attributed to interactions between frugivore behaviour and the local distribution of fruit. The third location had lower than expected beta diversity, reflecting dispersal of a complete array of tree species' seeds to sampling sites, plus long-distance dispersal of nonlocal indigenous species of large seeds. Hemiphaga novaeseelandiae appears to be dispersing an array of species of large seeds between co-fruiting tree species at some Auckland locations. However, incomplete seed dispersal service at two of the locations, together with evidence of low recruitment of some species of seeds, could eventually reduce tree species diversity. [ABSTRACT FROM AUTHOR]

Growing interest in functional silviculture is promoting new approaches to the study of seed dispersal and regeneration, two of the key processes that determine the structure and dynamics of plant populations. Nothofagus glauca is an obligate-seeding tree species typical of Mediterranean forests in central Chile. We studied stand structure, regeneration, seed release (quantity and quality) and seed dispersal in stands of N. glauca. Seed release started in mid- to late summer or in early autumn, and continued for a period of four to five months. Seed release reached a number of up to 2 million seeds per hectare. Seed shadow was characterised by a peak of density beneath the plant canopy and a very short tail of much lower densities, indicating that seeds are concentrated beneath mother plants when dispersed. The number of individuals who produced seeds during the season was estimated at 100 trees per hectare, and the highest frequency of seeding trees was observed in the diameter class of 28 cm to 48 cm, with the highest production of seeds in the 43 cm individuals (70 years old). Ninety percent of the regeneration was concentrated within the seed tree crown radius. Only a marginal presence of seedlings was observed outside the crown projection area and decreased as the distance to the base of the tree increased, until reaching a maximum distance of 12 m. It can be concluded that adult N. glauca forests rarely disturbed, tend to form multi-age stand structures. [ABSTRACT FROM AUTHOR]

Larvae are thought to be highly vulnerable to offshore transport of upwelling regions, limiting recruitment to infrequent wind relaxation and downwelling events. However, larvae could also be transported onshore by upwelled bottom waters, onshore wind-forcing or internal tides throughout the water column. We determined the relative importance of these hypothetical mechanisms for the timing of recruitment of 8 invertebrate taxa during the peak upwelling season in a region of strong, persistent upwelling. Recruitment was determined for 5 yr at an open embayment near the surface and bottom of the water column to examine the interaction of behavioral and physical processes regulating larval recruitment. Postlarvae consistently recruited near the surface or near the bottom depending on the species. Onshore delivery of larvae during wind relaxations and reversals did not best explain recruitment patterns in our area for most taxa. Only mussels consistently recruited more during these events, and they recruited in bottom rather than surface waters. Six crab taxa recruited primarily during upwelling. Recruitment of 7 taxa was intermittently correlated with the maximum tidal range, suggesting that internal waves also may deliver larvae onshore. Thus larvae may recruit by multiple processes in upwelling regions rather than being limited to infrequent relaxation events, leaving the mechanisms responsible for observed spatial patterns in larval recruitment and adult densities unexplained. Comprehensive studies of the behavioral and physical processes underlying larval recruitment and post-settlement mortality are needed to explain observed temporal and spatial variation in population dynamics and community structure in upwelling regions. © Inter-Research 2009.

The ability of miniscule larvae to control their fate and replenish populations in dynamic marine environments has been a long-running topic of debate of central importance for managing resources and understanding the ecology and evolution of life in the sea. Larvae are considered to be highly susceptible to offshore transport in productive upwelling regions, thereby increasing dispersal, limiting onshore recruitment, and reducing the intensity of community interactions. We show that 45 species of nearshore crustaceans were not transported far offshore in a recruitment-limited region characterized by strong upwelling. To the contrary, 92% of these larvae remained within 6 km from shore in high densities throughout development along two transects sampled four times during the peak upwelling season. Larvae of most species remained nearshore by remaining below a shallow Ekman layer of seaward-flowing surface waters throughout development. Larvae of other species migrated farther offshore by occurring closer to the surface early in development. Postlarvae evidently returned to nearshore adult habitats either by descending to shoreward-flowing upwelled waters or rising to the sea surface where they can be transported shoreward by wind relaxation events or internal waves. Thus wind-driven offshore transport should not limit recruitment, even in strong upwelling regions, and larvae are more likely to recruit closer to natal populations than is widely believed. This study poses a new challenge to determine the true cause and extent of recruitment limitation for a more diverse array of species along upwelling coasts, and thus to further advance our understanding of the connectivity, dynamics, and structure of coastal populations.

Larvae are thought to be highly vulnerable to offshore transport in productive upwelling regions, which increases cross-shelf and alongshore dispersal, limits recruitment, and reduces the strength of community interactions. We investigated whether the last planktonic stages of shallowwater crabs (1) occur far offshore during the peak upwelling season in a region of strong upwelling that is recruitment limited, (2) occur farther offshore during upwelling than relaxation conditions, (3) occur farthest from shore at a major headland where currents are deflected offshore, and (4) recruit less during years of stronger upwelling. Crab postlarvae were collected from between 1 and 70 km from shore at 3 locations across an upwelling cell during upwelling and relaxation conditions in northern California, USA, for 3 yr, and recruitment was measured at 2 sites during 2 of these years. Postlarvae of all species collected were most abundant on the inner continental shelf (84%) and were scarce in the open ocean. Postlarvae of 3 taxa only occurred on the inner shelf, whereas postlarvae of the other 3 taxa collected occurred in low abundances on the outer shelf even during prolonged upwelling. They were abundant close to shore at the Point Reyes headland where flow is deflected offshore. Postlarvae did not occur farther from shore during a year of very strong upwelling, and 4 of 7 taxa recruited more then. Thus, crab postlarvae do not appear to be advected far offshore or recruit less during strong upwelling conditions, and the cause and extent of recruitment limitation warrants further investigation. © Inter-Research 2009.

Dispersal is a process critical for the dynamics and persistence of metapopulations, but it is difficult to quantify. It has been suggested that the old-forest lichen Lobaria pulmonaria is limited by insufficient dispersal ability. We analyzed 240 DNA extracts derived from snow samples by a L. pulmonaria-specific real-time PCR (polymerase chain reaction) assay of the ITS (internal transcribed spacer) region allowing for the discrimination among propagules originating from a single, isolated source tree or propagules originating from other locations. Samples that were detected as positives by real-time PCR were additionally genotyped for five L. pulmonaria microsatellite loci. Both molecular approaches demonstrated substantial dispersal from other than local sources. In a landscape approach, we additionally analyzed 240 snow samples with real-time PCR of ITS and detected propagules not only in forests where L. pulmonaria was present, but also in large unforested pasture areas and in forest patches where L. pulmonaria was not found. Monitoring of soredia of L. pulmonaria transplanted to maple bark after two vegetation periods showed high variance in growth among forest stands, but no significant differences among different transplantation treatments. Hence, it is probably not dispersal limitation that hinders colonization in the old-forest lichen L. pulmonaria, but ecological constraints at the stand level that can result in establishment limitation. Our study exemplifies that care has to be taken to adequately separate the effects of dispersal limitation from a limitation of establishment.

The availability of habitat at one stage of a species' life history may limit the ultimate population size of that species. In particular, species that use distinct juvenile habitats may experience bottlenecks at an early life stage that have important and potentially unexpected consequences for adult population sizes. I used intertidal hermit crabs Pagurus samuelis and P. hirsuitisculus as a model system to test experimentally the effect of increasing juvenile and adult habitat (snail shells, Littorina sp. and Tegula funebralis) availability on adult population size. Despite strong evidence from these experiments that juvenile hermit crab population size was limited by juvenile habitat availability, adult population size was not. Instead, results indicated that adult populations were probably limited by recruitment and adult habitat availability. Consequently, these results (1) demonstrate that identifying true habitat bottlenecks can be challenging, (2) show that identifying true bottlenecks requires one to evaluate the effect of bottlenecks on adult population size, and (3) offer a rigorous empirical test of the assumption that hermit crab populations are limited by the availability of large shells. These results also highlight how conservation and management strategies designed to protect species with stage-structured life histories must consider the actual role different habitats play in controlling adult population size if they are to be most effective.

In this study, we aimed to provide a comprehensive insight into seedling and ramet recruitment at the community level on recent landslide scars (i.e., the sliding surfaces regarded as the most difficult zones of landslides to restore), which may cast new light on landslide ecology and enhance theoretical support for interventions on landslide restoration. Through seedling and ramet monitoring and adult surveying on 12 three‐year‐old landslide scars on the hilly and gullied Loess Plateau, China, we characterized seedling and ramet recruitment in terms of their trade‐offs, processes and amounts, and we also assessed compositional correspondence between the adult and young (all seedlings and ramets combined) layers. We found that when seedling recruitment was employed in tandem with ramet recruitment, which might maximize colonists' fitness. Moreover, seedlings and ramets emerged constantly and were followed by low mortality rates. However, there were problems of emergence limitation and constant death, and, as a result, seedlings and ramets remained at low densities. Therefore, there appeared to be a slow and limited recruitment process of plant colonists on the scars. In addition, there was a high degree of compositional uncoupling between the adult and young layers, implying future potential changes of plant communities driven by Poa sphondylodes Trin., Stipa bungeana Trin., Ixeridium sonchifolium (Maxim.) Shih, Astragalus discolor Bunge ex Maxim. and Artemisia scoparia Waldst. et Kit. on shady scars and I. sonchifolium (Maxim.) Shih on sunny scars. We also proposed that the first three species can be used to restore landslide scars in the study area. [ABSTRACT FROM AUTHOR]

Questions: Dispersal is important for the formation of biodiversity patterns. However, studying dispersal is difficult, particularly in established communities. We examined local dispersal processes in the forest herbaceous layer by looking at the abundance of plants in the neighbourhood of the surveyed plots and using dispersal traits and fecundity‐related attributes. Location: Thermophilous oakwood in south Moravia, Czech Republic. Methods: We collected plant community and environmental data from 2 m × 2 m plots nested in a 5 m × 5 m square grid, covering 0.36 hectares of temperate forest. We created binomial generalised linear models of species occurrence in the 2 m × 2 m plots, using species frequencies in four adjacent 5 m × 5 m plots (plot neighbourhood) and environmental data, to account for dependence caused by habitat factors. We analysed the relationships between neighbourhood effects and species attributes using linear regression. Results: Approximately one third of species had a stronger association to neighbourhood alone than to local environment factors. For the remaining species, there was a large joint effect of neighbourhood and environment. However, the link between dispersal traits and the neighbourhood effect was weak. The trait analyses showed that plumed appendages were negatively correlated to neighbourhood effects, whereas possession of elongated appendages, high terminal velocity, clonal spread and absence of seed appendages exhibited insignificant positive relationships to the neighbourhood. Conclusions: At the scale of metres, the distributional patterns of forest herbs cannot be solely associated with dispersal. The reasons could be methodological: our data contain a limited set of species with mostly database‐derived attributes. However, there may also be ecological mechanisms involved. The spatial distribution of plants could be modified by limited seed production and further reshaped by extinctions during earlier ontogenetic stages. [ABSTRACT FROM AUTHOR]

Savanna tree cover is dynamic due to disturbances such as fire and herbivory. Frequent fires can limit a key demographic transition from sapling to adult height classes in savanna trees. Saplings may be caught in a 'fire trap', wherein individuals repeatedly resprout following fire top‐kill events. Saplings only rarely escape the cycle by attaining a fire‐resistant height (e.g. taller than the minimum scorch height) during fire‐free intervals.Large mammalian herbivores also may trap trees in shorter size classes. Browsing herbivores directly limit sapling height, while grazing herbivores such as cattle facilitate sapling growth indirectly via grass removal. Experimental studies investigating how meso‐wildlife, megaherbivores and domestic livestock affect height of resprouts following fire are rare, but necessary for fully understanding how herbivory may reinforce (or counteract) the fire trap. In our study system, interactive fire–herbivore effects on transitions from sapling (<1 m) to adult tree (>1 m) height classes may be further influenced by plant defences, such as symbiotic ants.We used the Kenya Long‐term Exclosure Experiment (KLEE) to investigate how post‐fire resprout size of a widespread monodominant East African tree, Acacia drepanolobium was influenced by (a) herbivory by different combinations of cattle, meso‐wildlife (15–1,000 kg) and megaherbivores (>1,000 kg) and (b) the presence of acacia–ant mutualists that confer tree defences. We sampled height, stem length and ant occupancy of resprouts exposed to different herbivore combinations before and after controlled burns.Resprout height of saplings that were short prior to fire (<1 m) was reduced primarily by meso‐wildlife. Negative effects of elephants on post‐fire resprout height increased with pre‐fire tree size, suggesting that resprouts of the tallest trees (with the greatest potential to escape the fire trap cycle) were preferentially browsed and reduced in height by elephants. There were no significant cattle effects.Synthesis. We provide experimental evidence for two potential pathways through which large herbivores exert control over sapling escape from the fire trap: (a) post‐fire meso‐wildlife browsing of short (<1 m) resprouts and (b) elephant browsing of the largest size class of resprouts, which would otherwise be most likely to escape the fire trap. [ABSTRACT FROM AUTHOR]

Frugivores shape plant communities via seed dispersal of fleshy‐fruited plant species. However, the structural characteristics that frugivores impart to plant communities are little understood. Evaluating how frugivores structure plant communities via the nonproportional use of available fruit resources is critical to understand the functioning of ecosystems where fleshy‐fruited plant species are dominant, such as tropical forests.We performed a seed‐addition field experiment to investigate how frugivorous birds shape the composition and richness of forests during early stages of secondary succession in cleared areas in Puerto Rico. The experiment tested whether the bird‐generated seed rain and the subsequent early successional plant communities were proportional representations of the fleshy‐fruited species that dominated the surrounding community. Experimental treatments consisted of patches with (a) seed‐additions by wild birds attracted to experimental patches with pole perches, (b) manual seed‐additions proportional to fruit abundance at the local scale (≤50 m from experimental plots) and (c) manual seed‐additions proportional to fruit abundance at the landscape scale (entire study site).Birds' seed‐additions differed in composition and abundance to expectations based on fruit availability at local and landscape scales. Treatments with seeds added by birds had the highest species richness in both the seed rain and the emergence stages despite how, on average, the monthly richness in the landscape‐scale treatment was double that of birds and the local‐scale treatment. This phenomenon was explained by the highest heterogeneity from the bird seed‐addition treatment across months, and the lowest seed per capita emergence rates in landscape treatments. Rather than reflecting relative fruit abundance, birds biased seed rain and per capita emergence towards a non‐random mixture of both small‐ and large‐seeded species, resulting in richer and distinct plant communities.Because frugivory and seed dispersal patterns depart from random encounters between frugivores and plants in communities, successional forests are characterized by an overrepresentation of proportionally rare plant species, and decreases in the dominance of many common species. Thus, for regenerating tropical forests, frugivory can function as mechanism that promotes persistence of rare plant species and their coexistence with more abundant plants. A plain language summary is available for this article. Plain Language Summary [ABSTRACT FROM AUTHOR]

• The invasive Rhododendron ponticum is considered an emergent threat in W France. • It thrives in woodlands on acidic soils and appears promoted by climate change. • It locally spreads on moister soils via active layering. • Its ability to establish new populations is low due to recruitment limitations. • Management should minimize soil disturbance near established populations. Understanding the population dynamics of invasive species is essential for identifying the key parameters of their success and guiding management actions. European temperate forests of the Atlantic domain are prone to be invaded by the Pontic Rhododendron (Rhododendron ponticum L. subsp. baeticum (Boiss. & Reut.) Hand.-Mazz.), a shade-tolerate evergreen shrub native to the Iberian peninsula. While the invasion has a long history in Ireland and the British Isles, it is an emerging threat in mainland Europe. It is therefore a timely challenge to better understanding the invasive dynamics of this species in this context. We studied the population dynamics of R. ponticum in 27 invaded forests of north-western France, examining population structure, and individuals' growth, fertility and fecundity among contrasted light conditions. All invasive populations were found on acidic soils. Irrespective of light conditions, R. ponticum exhibited a regular radial growth, with a clear increase since the 1990s. The majority of stems were younger than 38 years on average, indicating a recent increase in population density. Light availability strongly impacted R. ponticum 's canopy structure, with higher canopy cover and stem numbers under sun conditions. Despite the production of a huge number of viable seeds, the observed number of seedlings was always very low irrespective of light conditions, indicating recruitment limitation and thus a limited ability to establish new, distant populations. In contrast, vegetative propagation via intense layering at the invasion front wave ensured local population spread from initially planted individuals, especially on moist soils. We conclude that where it has been planted, R. ponticum is able to actively layer, thereby forming dense bushes in the forest understories as long as the soil is acidic and relatively moist. The establishment of new, distant populations appears a rare event since recruitment is limited to particular microhabitats related to forest management-associated disturbances. Such disturbance should thus be avoided in sites where the species has already established, unless a post-disturbance eradication of R. ponticum 's seedling can be implemented the following years. The plantation of R. ponticum in forest must be avoided when the soil is acidic and moist. Because R. ponticum 's growth performances are increasing since the 1990s, as a likely consequence of climate change, monitoring established populations is recommended to detect a possible increasing invasiveness. [ABSTRACT FROM AUTHOR]

Planktonic larvae are thought to be very susceptible to offshore advection in upwelling regimes, increasing dispersal and decreasing recruitment. However, larvae of 42 species of nearshore benthic crustaceans primarily developed on the inner shelf at locations both in (98.5%) and away (99.8%) from a perennial upwelling center in the upwelling season of a recruitment-limited region characterized by persistent, strong, upwelling. During three cross-shelf cruises conducted at each location, larvae of 21 species remained on the inner shelf at both sites by occurring beneath seaward-flowing surface currents while larvae of other species migrated to midshelf (four species) or offshore (14 species) by initially developing near the surface. Postlarvae apparently returned to shore either deep in landward-flowing upwelled water or near the surface where behavior allows them to be transported shoreward by internal waves, diel wind cycles or wind relaxation events. Thus, recruitment limitation in upwelling regimes does not appear to be caused by larval mortality from offshore transport, requiring new research directions to advance our understanding of population dynamics, structure and connectivity.

Savanna ecosystems span a diverse range of climates, edaphic conditions, and disturbance regimes, the complexity of which has stimulated long‐standing interest in the mechanisms that maintain tree–grass coexistence. One hypothesis suggests that tree establishment is strongly limited by one or several demographic bottlenecks at early stages of the tree life cycle. A major impediment to testing this hypothesis is the lack of data on the relative strengths of different bottlenecks across key environmental gradients.To identify demographic bottlenecks that limit early tree establishment (0–18 months), we conducted a series of transplant experiments with two savanna trees species (Acacia robusta and Acacia tortilis) across a natural rainfall and soil fertility gradient in the Serengeti ecosystem, Tanzania. We tested the interactive effects of precipitation, herbivory, seed scarification, grass competition, water limitation, and tree species identity on two key life stages: germination and early seedling survival (0–2 months), and juvenile seedling survival (2–18 months).Germination and early seedling survival increased as a function of rainfall, in the absence of herbivores and when seeds were scarified. Juvenile seedling survival, in contrast, decreased with rainfall but increased in the absence of herbivores. Grass removal had the single strongest (positive) effect on juvenile seedling survival of any treatment. Soil moisture monitoring and grass‐addition treatments revealed that grasses negatively affected seedlings in ways that were not necessarily linked to soil moisture.A demographic model combining all effects across early life stages showed that the strength of grass competition on juvenile seedling survival was the key factor limiting early tree establishment. While rainfall had an unexpected opposing effect on the two life stages, the net effect of mean annual precipitation on early tree establishment was positive.Synthesis. Successful tree establishment in Serengeti is maximized by a seemingly unlikely sequence of events: (a) scarification of seeds by browsers, (b) heavy rainfall to promote germination, (c) intensive grazing (but absence of browsers), and (d) dry conditions during juvenile seedling growth (>2 months) to reduce competition with grasses. By considering a wide suite of conditions and their interactions, our experimental results are relevant to ongoing debates about savanna vegetation dynamics and structural shifts in tree:grass ratios. Successful tree establishment in Serengeti is maximized by a seemingly unlikely sequence of events: (a) scarification of seeds by browsers, (b) heavy rainfall to promote germination, (c) intensive grazing (but absence of browsers), and (d) dry conditions during juvenile seedling growth (>2 months) to reduce competition with grasses. By considering a wide suite of conditions and their interactions, results from our transplant experiments are relevant to ongoing debates about savanna vegetation dynamics and structural shifts in tree:grass ratios. [ABSTRACT FROM AUTHOR]

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The relative importance of sexual vs. asexual propagules in wetland plant invasions is poorly understood, particularly for their importance in increasingly disturbed, resource-rich environments. Using the invasive wetland grass Phragmites australis as a model, we evaluated the resource needs of its seeds and rhizome fragments. In a greenhouse experiment where we manipulated nitrogen and propagule type, we found that Phragmites seedlings, but not rhizome fragments, responded positively to nutrient enrichment. In a second experiment, where we focused on seedling resource needs and manipulated light, nitrogen, and seed source, we found that seedlings were inhibited by heavy shade with no additional benefit of nutrient additions. Different seed sources (wetlands surrounded by different dominant land-use types, a proxy for disturbance) had variable leaf production and stem height (biomass did not vary). Understanding the mechanisms of Phragmites recruitment via seeds and rhizomes is critical for informing how a clonal species—now understood to disperse largely by seeds—can invade increasingly disturbed, resource-rich habitats. Our study suggests that Phragmites invasion by seed is being fueled, in part, by the positive effects of increased nutrients and light on Phragmites seedling performance and potentially by varying performance of seedlings derived from different watersheds. [ABSTRACT FROM AUTHOR]

Recruitment is a strong determinant of year class strength and adult population density especially for sessile benthic invertebrates where post-settlement mortality and competition are low or relatively stable over time. A series of surveys were undertaken to characterize recruitment and post-settlement processes for two species of burrowing shrimps, Neotrypaea californiensis and Upogebia pugettensis in order to determine how they influenced broader adult populations in US west coast estuaries. On average, U. pugettensis decapodids settled earlier (April-July), recruited almost exclusively to areas with conspecific adults, and grew more rapidly during their first summer than N. californiensis. Neotrypaea californiensis decapodids settled and recruited over a longer period (June-November) and were distributed across the tidal flat. While initially more abundant in areas with conspecific adults, they also either survived better or redistributed as small juvenile shrimp to areas where adults were absent. Linear relationships were found between abundance of newly recruited (0+ age class) shrimp and that of older 1+ shrimp a year later. Positive slopes were close to one for N. californiensis but less than one for U. pugettensis, suggesting lower survival. Annual recruitment varied dramatically but was more consistent for both species in Yaquina Bay. Patterns in strong recruitment years amongst estuaries, particularly for U. pugettensis, suggest the presence of multi-estuary metapopulations linked via larval dispersal. These results have important implications for shrimp population management including control for shellfish aquaculture, but also conservation of estuarine habitats due to the strong influence of these ecosystem engineers on the benthic community. [ABSTRACT FROM AUTHOR]

Abstract: Considerable areas dominated by bracken Pteridium aquilinum (L.) Kuhn occur worldwide and are associated with arrested forest recovery. How forest recovery is impeded in these areas remains poorly understood, especially in the African highlands. The component processes that can lead to recruitment limitation—including low seed arrival, availability and persistence—are important determinants of plant communities and offer a potential explanation for bracken persistence. We investigated key processes that can contribute to recruitment limitation in bracken‐dominated clearings in the Bwindi Impenetrable National Park, Uganda. We examined if differences in seed rain (dispersal limitation), soil seed bank, or seed removal (seed viability and persistence) can, individually or in combination, explain the differences in tree regeneration found between bracken‐dominated areas and the neighboring forest. These processes were assessed along ten 50‐m transects crossing the forest–bracken boundary. When compared to the neighboring forest, bracken clearings had fewer seedlings (bracken 11,557 ± 5482 vs. forest 34,515 ± 6066 seedlings/ha), lower seed rain (949 ± 582 vs. 1605 ± 335 tree seeds m−2 year−1), comparable but sparse soil seed bank (304 ± 236 vs. 264 ± 99 viable tree seeds/m2), higher seed removal (70.1% ± 2.4% vs. 40.6% ± 2.4% over a 3‐day interval), and markedly higher rodent densities (25.7 ± 5.4 vs. 5.0 ± 1.6 rodents per 100 trapping sessions). Camera traps revealed that rodents were the dominant animals visiting the seeds in our seed removal study. Synthesis: Recruitment limitation contributes to both the slow recovery of forest in bracken‐dominated areas, and to the composition of the tree species that occur. Low seed arrival and low persistence of unburied seeds can both explain the reduced density of seedlings found in bracken versus neighboring forest. Seed removal, likely due to rodents, in particular appears sufficient to constrain forest recovery and impacts some species more severely than others. [ABSTRACT FROM AUTHOR]

Aims: Plant-soil feedbacks (PSFs) have been shown to be relevant drivers of forest community dynamics. However, few studies have explored variation of PSFs along environmental gradients. In a framework of climate change, there is a great need to understand how interactions between plants and soil microbes respond along climatic gradients. Therefore, we compared PSFs along a precipitation gradient in Mediterranean oak forests and included trait responses. Following the Stress Gradient Hypothesis (SGH), we expected less negative or even positive PSFs in the physically harsh dry end of our gradient and more negative PSFs in the wettest end.Methods: We grew Quercus ilex and Quercus suber acorns on soil inoculated with microbes sampled under adults of both species in six sites ranging in annual precipitation. After 4 months, we measured shoot biomass and allocation and morphological traits above and belowground.Results: We found negative PSFs for Q. ilex independent of precipitation, whereas for Q. suber PSFs ranged from positive in dry sites to negative in wet sites, in agreement with the SGH. The leaf allocation showed patterns similar to shoot biomass, but belowground allocation and morphological traits revealed responses which could not be detected aboveground.Conclusions: We provide first evidence for context-dependent PSFs along a precipitation gradient. Moreover, we show that measuring root traits can help improve our understanding of climate-dependent PSFs. Such understanding helps to predict plant soil microbe interactions, and their role as drivers of plant community dynamics under ongoing climate change. [ABSTRACT FROM AUTHOR]

Previous analyses of the regional distribution of forest plants have revealed that some species have a biased distribution towards either ancient or recent forest patches. It has been therefore proposed to classify forest plant species according to their affinity for ancient or recent patches. In this contribution, we aimed at providing a dynamical perspective on this static concept of ancient/recent forest species. We developed an inference method to estimate the metapopulation dynamics of forest plants based on landscape history and static (and incomplete) biodiversity data accounting for false absence records. We assessed the power of this novel inference method using simulated metapopulation and landscape dynamics. We finally applied this method to occupancy data of 174 and 121 forest species in two networks of 9208 and 9201 forest patches respectively. These patch networks are located in two French regions, with corresponding landscape historical data based on two forest maps conceived in 1840 and 2000. Our analyses revealed that i) the inference method enables to satisfactorily infer three parameters of the metapopulation model: the rates of colonization, extinction and decay of colonization with distance; ii) this three parameter metapopulation model is sufficient to reproduce the occurrence spatial structure of 72% and 61% of the investigated species in the two regions; iii) forest plant species are distributed along a spectrum of turn-over speed, in which small (large) colonization capacity are associated with small (large) propensity to extinction; iv) species position along this spectrum can be partially predicted from plant functional traits; and v) species metapopulation dynamics are driven by the interaction between landscape and species intrinsic properties, suggesting that ancient/recent forest species lists are unlikely to be easily extrapolated to novel landscapes. [ABSTRACT FROM AUTHOR]

The interplay between dispersal and adaptation to local environments ultimately determines the distribution of plant species, but their relative contribution remains little understood. Tropical mistletoes provide the opportunity to dissect these contributions of dispersal and adaptation, because as hemiparasitic plants, they are typically adapted to grow on a handful of species within diverse tropical communities and are non-randomly dispersed by mutualistic frugivorous birds., Here we hypothesized that the primary determinant of the abundance of a tropical mistletoe ( Dendropemon caribaeus, Loranthaceae) in Puerto Rico will be the compatibility between the mistletoe and plant species in a community. Alternatively, the mistletoe's abundance could be primarily shaped by other factors such as the availability of potential host plants, or factors that determine how mistletoe seeds are dispersed by avian frugivores. We conducted surveys and experiments to assess the capacity of this mistletoe to grow on trees available in the local community, and measured the monthly phenology and seed dispersal patterns of the mistletoe and other bird-dispersed plants in the community over a period of 4 years. A path model was used to evaluate how the abundance of the mistletoe was shaped by host abundance, fruiting phenology, bird dispersal and compatibilities with host plants., Our analyses show that the compatibility between mistletoe and host tree species, measured by mistletoe survival and growth rate, was the most important factor for mistletoe abundance. The next most important factor was the phenological characteristics of the hosts; this outcome likely arose because frugivory and seed dispersal services for mistletoes and hosts are performed by the same birds., Synthesis. Mistletoes often parasitize only a subset of the suitable plant species that are available in a given community. Our results indicate that such patterns are not only determined by host quality and abundance but also by the phenological patterns of trees that influence the probabilities of mistletoe seeds being deposited on them by shared avian seed dispersers. [ABSTRACT FROM AUTHOR]

The constant supply of larvae to coastal habitats is important for the persistence of populations and can vary depending on oceanic conditions that may affect physical transport processes. We evaluated the survivorship ofChthamalusrecruits in Playa San Miguel, Baja California, for over a year to evaluate if the supply of new recruits was of greater importance than the post-recruitment factors of competition and predation in determining adult population size. We hypothesized that the number ofChthamalusrecruits would predict the number of adults present and that predation and competition would not play a significant role in determining adult densities. Recruit density was a robust predictor of adult density despite the presence of weak density-dependent mortality. Neither predation nor competition significantly affected the survivorship of recruits and did not decouple the relationship between recruit and adult densities, suggesting that these post-recruitment controls did not play an important role in determining the population size ofChthamalusbarnacles at this site. The data support the hypothesis that supply-side control is the primary factor structuring the population ofChthamalusin the intertidal community at Playa San Miguel. [ABSTRACT FROM AUTHOR]

Coral reefs in Moorea, French Polynesia, suffered catastrophic coral mortality through predation by Acanthaster planci from 2006 to 2010, and Cyclone Oli in 2010, yet by 2015 some coral populations were approaching pre-disturbance sizes. Using long-term study plots, we quantified population dynamics of spawning Pocillopora spp. along the north shore of Moorea between 2010 and 2014, and considered evidence that population recovery could be supported by self-seeding. Results scaled up from study plots and settlement tiles suggest that the number of Pocillopora spp. colonies on the outer reef increased 1,890-fold between 2010 and 2014/2015, and in the back reef, 8-fold between 2010 and 2014/2015. Assuming that spawning Pocillopora spp. in Moorea release similar numbers of eggs as con-generics in Hawaii, and fertilization success is similar to other spawning corals, the capacity of Pocillopora spp. to produce larvae was estimated. These estimates suggest that Pocillopora spp. in Moorea produced a large excess of larvae in 2010 and 2014 relative to the number required to produce the recruits found in the back reef and outer reef in 2010 and 2014, even assuming that ∼99.9% of the larvae do not recruit in Moorea. Less than a third of the recruits in one year would have to survive to produce the juvenile Pocillopora spp. found in the back and outer reefs in 2010 and 2014/2015. Our first order approximations reveal the potential for Pocillopora spp. on the north shore of Moorea to produce enough larvae to support local recruitment and population recovery following a catastrophic disturbance.

Background Seed production, seed dispersal and seedling establishment are relevant life phases of plants. Understanding these processes and their patterns is essential to recognize vegetation dynamics and to apply it to forest restoration. Methods For Olea europaea and Schefflera abyssinica, fecundity was estimated using randomized branch sampling. Seed dispersal and seedling establishment were monitored using spatially explicit seed traps and plots. Dispersal functions were calibrated applying inverse modeling. Results O. europaea produced more seeds and had longer dispersal distances compared to S. abyssinica. Correlations between observed and predicted number of recruits were statistically significant. Seedlings of the two species showed different niche requirements. Conclusions The studied species were recruitment-limited due to low dispersal activity or lack of suitable microsites. Restoration relying on natural regeneration should overcome these limitations by increasing disperser visitation and reducing biotic and abiotic stresses.

Background: Seed production, seed dispersal and seedling establishment are relevant life phases of plants. Understanding these processes and their patterns is essential to recognize vegetation dynamics and to apply it to forest restoration. Methods: For Olea europaea and Schefflera abyssinica, fecundity was estimated using randomized branch sampling. Seed dispersal and seedling establishment were monitored using spatially explicit seed traps and plots. Dispersal functions were calibrated applying inverse modeling. Results: O. europaea produced more seeds and had longer dispersal distances compared to S. abyssinica. Correlations between observed and predicted number of recruits were statistically significant. Seedlings of the two species showed different niche requirements. Conclusions: The studied species were recruitment-limited due to low dispersal activity or lack of suitable microsites. Restoration relying on natural regeneration should overcome these limitations by increasing disperser visitation and reducing biotic and abiotic stresses. [ABSTRACT FROM AUTHOR]

Parasites can impart heavy fitness costs on their hosts. Thus, understanding the spatial and temporal consistency in parasite pressure can elucidate the likeliness of parasites' role as agents of directional selection, as well as revealing variable environmental factors associated with infection risk. We examined spatiotemporal variation in digenetic trematode infection in 18 populations of an intertidal host snail ( Littorina littorea) over a 300 km range at an 11-yr interval, more than double the generation time of the snail. Despite a complete turnover in the snail host population, the average change in infection prevalence among populations was <1% over the 11-yr span, and all but three populations remained within 5 percentage points. This consistency of prevalence in each population over time suggests remarkable spatiotemporal constancy in parasite delivery vectors in this system, notably gulls that serve as definitive hosts for the parasites. Thus, despite gulls' high mobility, their habitat usage patterns are ostensibly relatively fixed in space. Importantly, this spatiotemporal consistency also implies that sites where parasites are recruitment limited remain so over time, and likewise, that parasite hotspots stay hot. [ABSTRACT FROM AUTHOR]

Urban forests are more vulnerable to exotic species invasions than natural forests and are often a pathway for exotic invasions into natural areas. Investigating the mechanisms responsible for species coexistence in urban ecosystems is important to prevent forest invasions and conserve native biodiversity. In this experiment, we studied seedling recruitment for two exotic invasive ( Acer platanoides and Rhamnus cathartica) and two native tree species ( Acer saccharum and Betula papyrifera) in two urban forests. We measured the effects of distance from a mature tree on the growth of conspecific seedlings and their belowground interactions (mutualisms and pathogens). We expected that native seedlings growing in close proximity to a mature conspecific tree would more likely be damaged by co-specific pathogens than those growing further away. In contrast, considering that exotic invaders have not coevolved with the local soil pathogens, distance from the adult conspecific tree would not affect their seedlings. We collected undisturbed soil cores at five incremental distances from each adult tree and grew conspecific seeds in these cores. After three months of growth, we measured plant biomass, mycorrhizal root colonization and root lesions. We found that biomass increased with distance from the mature conspecific tree only for A. platanoides and no distance dependent signal was detected for other response variables. Our results show that distance from a conspecific mature tree may not determine exotic species invasibility in an urban forest and that, instead, this may contribute to promote native and invasive species coexistence in urban forest systems. [ABSTRACT FROM AUTHOR]