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The patterns and drivers of pollen transport on insect bodies can have important consequences for plant reproductive success and floral evolution; however, they remain little studied. Recently, pollinator bodies have been further described as pollen competitive arenas, where pollen grains can compete for space, with implications for the evolution of pollen dispersal strategies and plant community assembly. However, the identity, strength, and diversity of pollen competitive interactions and how they vary across pollinator functional groups is not known. Evaluating patterns and drivers of the pollen co‐transport landscape and how these vary across different pollinator groups is central to further our understanding of floral evolution and co‐flowering community assembly.Here, we integrate information on the number and identity of pollen grains on individual insect pollen loads with network analyses to uncover novel pollen co‐transport networks and how these vary across pollinator functional groups (bees and bee flies). We further evaluate differences in pollen load size, species composition, diversity and phylogenetic diversity among insect groups and how these relate to body size and gender.Pollen co‐transport networks were diverse and highly modular in bees, with groups of pollen species interacting more often with each other on insect bodies. However, the number, identity and frequency of competitors that pollen grains encounter on insect bodies vary between some pollinator functional groups. Other aspects of pollen loads such as their size, richness and phylogenetical diversity were shaped by bee size or gender, with females carrying larger but less phylogenetically diverse pollen loads than males.Synthesis. Our results show that the number, identity and phylogenetic relatedness of pollen competitors changes as pollen grains travel on the body of different pollinators. As a result, pollinator groups impose vastly different interaction landscapes during pollen transport, with so far unknown consequences for plant reproductive success, floral evolution and community assembly. [ABSTRACT FROM AUTHOR]

Increased plant size is generally expected to have negative consequences for mating by increasing pollen transfer between flowers of the same plant. Such geitonogamous self‐pollination would then reduce sexual fitness through both female and male function. However, recent theoretical work has indicated that when plants grow clonally, the outward expansion of plants caused by clonal growth might have positive effects on siring without substantially increasing rates of self‐pollination.We investigated patterns of pollen dispersal, selfing and siring in a monoecious population of the clonal plant Sagittaria latifolia, in which clones varied in size and the extent of intermingling with other clones. A spatially explicit statistical model based on the inferred pollen dispersal kernel was constructed to examine the mechanisms underlying observed mating patterns.Pollen dispersal typically occurred over distances that exceeded the spatial extent of clones. There was a positive association between clone size (measured as the number of ramets per genet) and the likelihood that clones were intermingled with the shoots of other clones. Together, these patterns of pollen dispersal and clonal intermingling resulted in a weak positive association between clone size and selfing rates and a strong positive association between clone size and outcross siring success. These patterns were replicated in the spatially explicit model, indicating that the intermingling of clones is an important determinant of mating patterns in this population.Synthesis. Our study provides the first examination of the pollen dispersal kernel for a clonal plant. It is the first study providing empirical support for model predictions that potentially negative effects of increased selfing in large clones might be offset by increased siring success. This implies that the negative consequences of becoming large do not necessarily apply to clonal plants. [ABSTRACT FROM AUTHOR]

Dispersal is essential for species to survive the threats of habitat destruction and climate change. Combining descriptions of dispersal ability with those of landscape structure, the concept of functional connectivity has been popular for understanding and predicting species' spatial responses to environmental change., Following recent advances, the functional connectivity concept is now able to move beyond landscape structure to consider more explicitly how other external factors such as climate and resources affect species movement. We argue that these factors, in addition to a consideration of the complete dispersal process, are critical for an accurate understanding of functional connectivity for plant species in response to environmental change., We use recent advances in dispersal, landscape and molecular ecology to describe how a range of external factors can influence effective dispersal in plant species, and how the resulting functional connectivity can be assessed., Synthesis. We define plant functional connectivity as the effective dispersal of propagules or pollen among habitat patches in a landscape. Plant functional connectivity is determined by a combination of landscape structure, interactions between plant, environment and dispersal vectors, and the successful establishment of individuals. We hope that this consolidation of recent research will help focus future connectivity research and conservation. [ABSTRACT FROM AUTHOR]

Hybridization is a key evolutionary process with major consequences for conservation and speciation. However, sexual barriers interact with the local context to determine hybridization rates in a way that is still poorly explored. For instance, in the context of an expanding or introduced plant population, where a few individuals are isolated in populations dominated by heterospecific individuals, what is the hybridization potential?, To obtain baseline predictions on hybridization rate between two species differing in abundance and to evaluate the effect of pollen limitation, we first used a mean-field model. We then explored a spatially explicit individual-based mating model relying on pollen dispersal kernels to predict hybridization rates in a mixed-species stand, under different scenarios for (i) the strength of sexual barriers; (ii) the spatial distribution of individuals within the site; (iii) the variation in individual fecundity; and (iv) the magnitude, shape and asymmetry of pollen dispersal kernels., Pollen limitation was shown to have the potential to greatly increase hybridization rates. Similarly, fine-scale variation in species composition can result in elevated hybridization rates compared to mean-field predictions, especially with strong sexual barriers. However, species clustering in combination with reduced pollen dispersal has the opposite effect, protecting from hybridization., Synthesis. Our simulation results show that variation of the pollen pool composition at the scale of individuals or stigmas due to spatial configurations or pollen limitation can substantially modify hybridization rates. We explain this by the disproportionate effect of some pollen environments on average hybridization rates. This suggests thoroughly evaluating individual behaviour in terms of hybridization, especially for rare or patchy species. [ABSTRACT FROM AUTHOR]

Microsatellite-based genetic assignment is used broadly to monitor contemporary effective dispersal among populations. The need to investigate the robustness of this method to common genotyping errors was emphasized more than a decade ago, but it remains unaddressed., We evaluate here for the first time the effect of mistaken and null alleles on estimates of contemporary seed and pollen migration rates obtained with genetic assignment methods. We also introduce a novel Bayesian approach to jointly estimate seed and pollen migration rates, genotyping error rates and null allele frequencies, not requiring independent reference or duplicate genotypic data., Unaccounted-for mistaken alleles caused positive bias and increased the root mean square error ( RMSE) of pollen migration rate estimates, whereas seed migration rate estimates were weakly sensitive to mistyping. Jointly estimating mistyping rates minimized the bias and RMSE they introduce on pollen migration estimates, while yielding seed migration rate estimates with similar or slightly larger bias and RMSE than those obtained when ignoring mistyping., Ignoring genotyping errors can be especially problematic when there is no actual migration, because it can lead to the wrong conclusion that there is statistically significant exchange of pollen and/or seeds among populations that are actually isolated., Unaccounted-for null alleles are problematic when among-population pollen dispersal is present, leading to underestimation of pollen migration rates and overestimation of seed migration rates. Jointly estimating null allele frequencies minimized these two biases, reduced the RMSE of seed migration rate estimates and produced relatively small changes in the RMSE of pollen dispersal estimates., Synthesis. Disregarding genotyping errors and null alleles can produce biased and less accurate estimates of the rates at which present-day plant populations are exchanging seed and pollen. An approach is proposed here to minimize the effect of genotyping problems on contemporary migration rate estimates, which should help avoiding erroneous migration inference, monitoring and management, especially when dealing with low migration rates and their associated uncertainty. [ABSTRACT FROM AUTHOR]

Summary 1. To understand pollinator-plant symbioses and to conserve forest resources effectively, we need an understanding of pollen dispersal patterns and the heterogeneity (spatial and temporal) of male fecundity. 2. We investigated pollen dispersal patterns of the hill dipterocarp species Shorea curtisii using a modified Neighbourhood model. Seeds were collected following a sporadic general flowering (GF) event in 2002 and two mass GF events in 1998 and 2005. Seed paternity was then determined to investigate pollen dispersal patterns and the heterogeneity of male fecundity. 3. Pollen dispersal distances were longer, and the effective number of males lower, in the sporadic GF of 2002, than in the mass GF events of 1998 and 2005. 4. There was high between-individual variation in male fecundity, and small trees contributed less than large trees to the analysed seed pool. The results indicate that selective logging may adversely affect the reproduction of such species due to the removal of large trees from the reproductive population. 5. Synthesis. The large number of effective male individuals during the mass GF events provides evidence of Allee effects, suggesting that the mass GF events are of evolutionary significance and may contribute to the maintenance of genetic diversity. Future forestry practice needs to take into account variation in male fecundity, pollen dispersal and the mating system to ensure sustainable regeneration. [ABSTRACT FROM AUTHOR]

Summary 1. Obtaining accurate estimates of the pollen dispersal kernel is central to a wide range of ecological studies. Assessing their statistical uncertainty is as important, but rarely considered. 2. We developed a new method of marked point processes for nonparametric estimation of dispersal kernels based on data of genetic paternity analysis that does not require assumptions about the shape of the dispersal distribution. This allows for construction of Monte Carlo simulation envelopes of a given null model, such as random mating, and for uncertainty assessment of the observed dispersal kernel. 3. We applied our method to characterize spatial patterns of pollen flow in an isolated population of Populus nigra in Central Germany and to assess the associated statistical uncertainty in estimates of within-population dispersal kernels. We compared our nonparametric within-population kernel estimate with that of established methods of parametric kernel fitting including: (i) a general mating model, (ii) a simplified mating model using categorical paternity data and (iii) least-squares regression of the nonparametric kernel estimate. 4. Our analysis showed a significant departure from the random mating null model. We found a highly significant excess of mating events at short distances (<400 m) and a weakly significant shortage of mating events at larger distances (1500-2000 m). Simulation envelopes of the null model were very wide at larger distances (>2000 m), indicating large uncertainty on the detailed shape of the kernel's tail. 5. Results of the point pattern analysis were consistent with kernel fits using published maximum-likelihood mating models. Model selection revealed that two-component pollen dispersal kernels were the most parsimonious functions. 6. Synthesis. Our approach of nonparametric kernel estimation could be widely applied for dispersal data from genetic paternity analysis and complements traditional kernel estimation by providing a nonparametric kernel estimate and effective methods for an uncertainty assessment in kernel estimation. Our results indicate that statistical model fitting may substantially underestimate the uncertainty in kernel estimation, especially at larger distances. [ABSTRACT FROM AUTHOR]

1. The spatial genetic structure (SGS) of a plant population is mainly determined by gene flow via seed and pollen, various natural selection pressures and spatial patterns of existing plants. However, the role of those factors in shaping SGS requires further investigation. 2. We studied the relative importance of those factors in shaping the SGS of an understorey dioecious fig species ( Ficus cyrtophylla). Spatial patterns of existing individuals and microhabitat were surveyed, patterns of seed rain were investigated, seed dispersers were observed in the field, and the gene flow and SGS of a focal population were determined. 3. Three mid-sized bulbul ( Pycnonotus spp.) species were the primary dispersers of Ficus cyrtophylla fruits. All the age cohorts exhibited clumped patterns with a decreasing trend from seeds to seedlings, saplings and adults. Seed rain occurred in a non-random pattern with high clumping in moderately lit microhabitats. The observed pattern suggests disperser preferences for those microhabitats resulting in higher seed deposition. 4. Seeds and pollen of F. cyrtophylla were widely dispersed (ranging from 9 m to 2.75 km and 10 m to 3 km, respectively). About two-thirds of seeds and half of the pollen grains were locally dispersed (≤ 250 m) within the focal population. 5. Significant positive autocorrelations occurred at a local scale (≤10 m) in seeds and seedlings but not in saplings and adults. The SGS pattern disappeared when we reduced the sample size of seedlings to that for the saplings, which suggests that demographic thinning effects (e.g. density-dependent predation and competition) on spatial distribution may lead to the loss of SGS through transitions from seedlings to saplings and adults. 6. Synthesis. Although F. cyrtophylla seeds and pollen were widely dispersed, the significant SGS present in seedlings probably resulted from clumped seed dispersal due to dispersers’ behaviour and high seedfall beneath parent trees. The loss of SGS in sapling and adult life stages is probably caused by demographic selection effects during recruitment. Our study emphasizes the different roles of dispersal and local selection in shaping SGS of plant populations. [ABSTRACT FROM AUTHOR]

1. Increased fire frequency is seen as a key threat to plant populations in Mediterranean-type ecosystems across the globe. Short inter-fire periods may exhaust soil-stored and fire-stimulated seed banks of fire-sensitive species, reducing actual and effective population sizes and eroding genetic diversity. 2. Here we used microsatellite genotyping to investigate the genetic impacts of repeated wildfires and, in particular, the contribution of above-ground genetic processes (seed and pollen dispersal) to the genetic structuring and composition of post-fire recruits in an isolated population of the fire-sensitive shrub Persoonia mollis ssp. nectens. 3. We tested the hypothesis that limited pollen and seed dispersal, in combination with the potentially patchy effects of fire at a fine scale within populations, would generate a highly structured population, a decline in genetic diversity after each fire and genetic heterogeneity between successive cohorts. 4. Wildfires killed all 25 adult plants in 1997 and, in 2001, killed all of the 476 seedlings remaining from the 1997 seedling cohort. Although there was no possibility of replenishment of the seed bank in the interval between fires, a second cohort of 381 seedlings emerged after the 2001 fire. 5. We found no evidence that successive fires produced either a decline in genetic diversity, as measured by allelic richness or expected heterozygosity, or the genetic differentiation of adult and successive seedling cohorts (Pairwise FST = −0.0125 to 0.0009). The seedling cohorts displayed less genetic structuring than anticipated. Spatial genetic structure was low, ranging from Sp = 0.02 in the 1997 seedlings to Sp = 0.06 in the 2001 seedlings, and using parentage analysis, we found that seedlings clustered under dead adults rarely reflected simple seed shadows. 6. Synthesis. Overall, we found that a numerically large seed bank with a bet-hedging strategy of staged seed germination, in combination with genetic mixing achieved by both pollen and seed dispersal, provides a powerful buffer against the negative impacts of frequent fire in P. mollis ssp. nectens. [ABSTRACT FROM AUTHOR]

1. Founder populations of plants are usually small and may become extinct due to many factors including inbreeding and low pollen transfer besides stochastic factors. This positive relationship between population size and individual fitness is taken as evidence of an Allee effect. Very few studies have quantitatively compared the influence of self-incompatibility systems and S-allele counts on the magnitude of observed Allee effects for different population sizes and seed and pollen dispersal distances. 2. This paper uses a stochastic, spatially explicit, individual-based cellular automaton model to simulate the dynamics of newly established plant populations with sporophytic or gametophytic self-incompatibility (SI) alleles and compares these to a null (Mendelian) population. Parameters varied in model simulation are the S-allele count, the initial population size, and the pollen and seed dispersal distances. These parameters were studied over a wide range to assess their relative impact on population viability compared to the null case in order to model the effect of self-incompatibility on population fitness. 3. The results indicate that Allee effects are enhanced and growth rates are slowed in newly established populations of species with S-alleles relative to Mendelian populations, leading to enhanced extinction risk. They also show the importance of the relationship between pollen and seed dispersal ranges on the fitness of the population. Populations with sporophytic self-incompatibility were more extinction-prone than those with gametophytic SI, and the latter more so than Mendelian populations when all other factors were held constant. 4. Synthesis. Overall, the simulation results indicate that Allee effects in small populations are enhanced in plants with S-alleles. Even in relatively large populations, S-allele count controls the strength of observed Allee effects. A high S-allele count is able to compensate for lower initial population size. Pollen and seed dispersal ranges had a similarly strong effect on the viability of populations with S-alleles. These effects are stronger in populations with sporophytic self-incompatibility than in those with gametophytic SI. Simulation results also indicate that S-alleles were not lost to genetic drift over time, in contrast with some earlier studies of S-allele systems displaying Allee effects. [ABSTRACT FROM AUTHOR]

1. In long-lived, terrestrial orchids, strong aggregation of adults and recruits within populations and pronounced spatial association between recruits and adults can be expected when seed dispersal is limited, probabilities of seed germination decrease with increasing distance from mother plants and/or not all mother plants contribute to future generations. When individuals are distributed evenly across life-history stages, these processes can also be expected to result in a significant fine-scale spatial genetic structure in recruits that will persist into the adult-stage class. 2. We combined detailed spatial genetic and point pattern analyses across different generations with parentage analyses to elucidate the role of the diverse processes that might determine spatial structure in Orchis mascula. 3. Analyses of spatial point patterns showed a significant association between adults and recruits and similar clustering patterns for both. Weak, but highly significant spatial genetic structure was observed in adults and recruits, but no significant differences were observed across life stages, indicating that the spatial genetic structure present in recruits persists into the adult stage. 4. Parentage analyses highlighted relatively short seed dispersal distances (median offspring-recruitment distance: 1.55 and 1.70 m) and differential contribution of mother plants to future generations. 5. Persistence of fine-scale spatial genetic structure from seedlings into the adult stage class is consistent with the life history of O. mascula, whereas relatively large dispersal distances of both pollen and seeds compared to the fine-scale clustering of adults and seedlings suggest overlapping seed shadows and mixing of genotypes within populations as the major factors explaining the observed weak spatial genetic structure. 6. Nonetheless, comparison of the spatial association between recruits and adults with the genetic analysis of offspring-parent distances suggests that the tight clustering of recruits around adults was probably caused by decreasing probabilities of seed germination with increasing distance from mother plants. 7. Synthesis. This study shows that the approach presented here, which combines spatial genetic and spatial pattern analyses with parentage analyses, may be broadly applied to other plant species to elucidate the processes that determine spatial structure within their populations. [ABSTRACT FROM AUTHOR]

1. Studies using highly informative genetic markers (e.g. microsatellites) have revealed effective movement of genes through pollen grains from more distant sources into offspring than those inferred on the basis of physical pollen movement alone. In order to identify the factors that cause such effective pollen movement in tree populations, analyses of the genetic structure of reproductive trees and parentage analyses for seedlings and saplings were conducted in a 110-ha population of Aesculus turbinata, a tall deciduous tree species that is pollinated by insects and has large seeds that are dispersed by gravity and small mammals. 2. By analysing genotypes of seed coats, which are identical to those of the seed parents, and of leaves from seedlings, pollen donors and seed parents were identified for seedlings. Differences in size and dispersal mode between pollen and seeds caused a significant difference in dispersal distances. Reflecting the restricted seed dispersal (25.3 m on average), there was significant positive relatedness between reproductive trees standing within 150 m of each other. 3. The percentage of self-pollinated offspring decreased from 8.3% at the seedling stage to 0.56% at the sapling stage. The disappearance of out-crossed individuals during the stage between seedling and sapling seemed to be associated with the spatial distance separating their parents: the proportion of juvenile trees that died was higher for those that originated from out-crosses between adults standing within 100 m of each other, where positive relatedness was found between adult trees. Consequently, the deaths of individuals arising from self-pollination events and from crosses between reproductive trees that were spatially adjacent caused longer effective pollen movement for the offspring that survived. The distance between the two parents of a tree, which indicates the distance of effective pollen movement, increased from 179.9 m for seedlings to 288.9 m for saplings. 4. The genetic structure of the adult population of A. turbinata affected the survival of offspring through biparental inbreeding depression, and, then, removal of individuals resulting from crosses between related adults in turn promoted effective pollination over longer distances. [ABSTRACT FROM AUTHOR]

1 We assessed the effects of population density and the spatial arrangement of genetically compatible mates on the seed set and pollen flow of a heterostylous, bumblebee-pollinated perennial, Primula sieboldii E. Morren (Primulaceae), by using an experimental population under natural pollination conditions. 2 We also examined the intermorph differences in the pollen dispersal distance and the frequency of self- and intramorph fertilization. 3 Seed set was significantly correlated with the number of opposite-morph flowers within 2 m in short-styled genets, and within 3 m in long-styled genets. 4 Mean pollen dispersal distance within the experimental population was 5.4 m, which was slightly shorter than that in a low-density population measured in a previous study (7.2 m). 5 The proportions of seedlings sired by the same morph or selfed were 10.2% and 3.0%, respectively, in long-styled mothers, compared with 1.9% and 0.0% among short-styled mothers. However, these differences were not statistically significant and no marked differences in pollen dispersal distances were observed between the two morphs. 6 Our results suggest that the presence of opposite-morph genets within several metres is essential for success of seed reproduction in P. sieboldii, irrespective of population density, and that stochastic deviation of the morph ratio in small populations is therefore likely to cause considerable reduction in seed set. [ABSTRACT FROM AUTHOR]

Tests the hypothesis that most of the pollen collected by forest-floor moss polsters originates from local sources. Comparison of pollen and forest inventory data from 30 plots in three forested regions; Moss polsters' annual and seasonal variations in pollen production and dispersal.

Summary1 Levels of nectar and pollen were manipulated in individual flowers of oil-seed rape, Brassica napus, which were then offered to foraging bumblebees (Bombus lapidarius) for a single visit. 2 The durations of flower visits by bumblebees increased with the amount of nectar, but were unaffected by the level of available pollen. The bees’ flower-handling routine may have become behaviourally fixed by the expectation of low pollen rewards, which prevailed in the experimental garden. 3 The effects of nectar provision on both pollen import (deposition on stigma) and export (removal from anthers) were studied. The amount of pollen transferred during a bumblebee’s visit was affected only by the amount of pollen that the flower presented. 4 Manipulated flowers that presented a large amount of available pollen received approximately three times more pollen on their stigmas during a bee’s visit than flowers with little available pollen, which suggests that autogamous pollen transfer contributes substantially to pollen deposition when pollen availability is high. The gradual dehiscence of the anthers in this species means that available pollen accumulates only if pollinator visits are infrequent, when the increased autogamy may act to ensure adequate pollination. 5 There was no relation between the quantity of nectar residue that a bee left after visiting a manipulated flower and the mean duration of its visits to unmanipulated flowers. Therefore, variation among individuals in the duration of visits to unmanipulated flowers apparently resulted from differences in foraging speed rather than from variation in the thoroughness of nectar removal. [ABSTRACT FROM AUTHOR]