Seed and pollen dispersal distances in two African legume timber trees and their reproductive potential under selective logging

The natural regeneration of tree species depends on seed and pollen dispersal. To assess whether limited dispersal could be critical for the sustainability of selective logging practices, we performed parentage analyses in two Central African legume canopy species displaying contrasted floral and fruit traits: Distemonanthus benthamianus and Erythrophleum suaveolens. We also developed new tools linking forward dispersal kernels with backward migration rates to better characterize long‐distance dispersal. Much longer pollen dispersal in D. benthamianus (mean distance d_p = 700 m, m_p = 52% immigration rate in 6 km² plot, s = 7% selfing rate) than in E. suaveolens (d_p = 294 m, m_p = 22% in 2 km² plot, s = 20%) might reflect different insect pollinators. At a local scale, secondary seed dispersal by vertebrates led to larger seed dispersal distances in the barochorous E. suaveolens (d_s = 175 m) than in the wind‐dispersed D. benthamianus (d_s = 71 m). Yet, seed dispersal appeared much more fat‐tailed in the latter species (15%–25% seeds dispersing >500 m), putatively due to storm winds (papery pods). The reproductive success was correlated to trunk diameter in E. suaveolens and crown dominance in D. benthamianus. Contrary to D. benthamianus, E. suaveolens underwent significant assortative mating, increasing further the already high inbreeding of its juveniles due to selfing, which seems offset by strong inbreeding depression. To achieve sustainable exploitation, seed and pollen dispersal distances did not appear limiting, but the natural regeneration of E. suaveolens might become insufficient if all trees above the minimum legal cutting diameter were exploited. This highlights the importance of assessing the diameter structure of reproductive trees for logged species.     

Effects of tree architecture on pollen dispersal and mating patterns in Abies pinsapo Boiss. (Pinaceae)

Plant architecture is crucial to pollination and mating in wind‐pollinated species. We investigated the effect of crown architecture on pollen dispersal, mating system and offspring quality, combining phenotypic and genotypic analyses in a low‐density population of the endangered species Abies pinsapo. A total of 598 embryos from three relative crown height levels (bottom, middle and top) in five mother plants were genotyped using eleven nuclear microsatellite markers (nSSRs). Paternity analysis and mating system models were used to infer mating and pollen dispersal parameters. In addition, seeds were weighed (N = 16 110) and germinated (N = 736), and seedling vigour was measured to assess inbreeding depression. Overall, A. pinsapo shows a fat‐tailed dispersal kernel, with an average pollen dispersal distance of 113–227 m, an immigration rate of 0.84–26.92%, and a number of effective pollen donors (N_ep) ranging between 3.5 and 11.9. We found an effect of tree height and relative crown height levels on mating parameters. A higher proportion of seeds with embryo (about 50%) and a higher rate of self‐fertilization (about 60%) were found at the bottom level in comparison with the top level. Seed weight and seedling vigour are positively related. Nevertheless, no differences were found in seed weight or in seedling‐related variables such as weight and length of aerial and subterranean parts among the different relative crown height levels, suggesting that seeds from the more strongly inbred bottom level are not affected by inbreeding depression. Our results point to vertical isotropy for outcross‐pollen and they suggest that self‐pollen may ensure fertilization when outcross‐pollen is not available in low‐density population.     

Long‐distance pollen and seed dispersal and inbreeding depression in Hymenaea stigonocarpa (Fabaceae: Caesalpinioideae) in the Brazilian savannah

Hymenaea stigonocarpa is a neotropical tree that is economically important due to its high‐quality wood; however, because it has been exploited extensively, it is currently considered threatened. Microsatellite loci were used to investigate the pollen and seed dispersal, mating patterns, spatial genetic structure (SGS), genetic diversity, and inbreeding depression in H. stigonocarpa adults, juveniles, and open‐pollinated seeds, which were sampled from isolated trees in a pasture and trees within a forest fragment in the Brazilian savannah. We found that the species presented a mixed mating system, with population and individual variations in the outcrossing rate (0.53–1.0). The studied populations were not genetically isolated due to pollen and seed flow between the studied populations and between the populations and individuals located outside of the study area. Pollen and seed dispersal occurred over long distances (>8 km); however, the dispersal patterns were isolated by distance, with a high frequency of mating occurring between near‐neighbor trees and seeds dispersed near the parent trees. The correlated mating for individual seed trees was higher within than among fruits, indicating that fruits present a high proportion of full‐sibs. Genetic diversity and SGS were similar among the populations, but offspring showed evidence of inbreeding, mainly originating from mating among related trees, which suggests inbreeding depression between the seed and adult stages. Selfing resulted in a higher inbreeding depression than mating among relatives, as assessed through survival and height. As the populations are not genetically isolated, both are important targets for in situ conservation to maintain their genetic diversity; for ex situ conservation, seeds can be collected from at least 78 trees in both populations separated by at least 250 m.     

Pollen Dispersal Between Isolated Trees in the Brazilian Savannah: A Case Study of the Neotropical Tree Hymenaea stigonocarpa

This case study examines the pollen dispersal distance, pollen dispersal patterns and intra‐family genetic structure for isolated trees in pastures of the bat‐pollinated Neotropical tree species Hymenaea stigonocarpa using six microsatellite loci and parentage analysis. The sampling included 28 grouped trees (referred to as the population) and six isolated trees in pastureland along a highway in Mato Grosso do Sul State, Brazil. From the population, we sampled 137 seeds from 12 seed‐trees, and from the isolated trees, we sampled 34 seeds from two seed‐trees. The results showed that pollen was dispersed over long distances (reaching 7353 m) and therefore the spatially isolated trees were not reproductively isolated. The pollen immigration rate in the population was also high (31%). Isolated trees presented a higher selfing rate (s=26%) than trees in the population (s=12%), suggesting that the spatial isolation of the trees increased selfing. However, selfing was responsible for only 30 percent of the inbreeding in offspring and mating among relatives was 70 percent. In the population, excluding selfing, ca 72 percent of the pollen was dispersed over distances <1000 m (average: 860 m). For the two isolated seed‐trees, excluding selfing, the average pollen dispersal distance was 5229 m. The results demonstrate that although pollen can be dispersed over long distances for H. stigonocarpa isolated trees, a high percentage of pollen comes from the same tree (selfing) and mating was correlated. Consequently, seeds must be collected from a large number of seed‐trees for conservation purposes.     

Spatial genetic structure and restricted gene flow in a functionally dioecious fig, <Emphasis Type="Italic">Ficus pumila</Emphasis> L. var. <Emphasis Type="Italic">pumila</Emphasis> (Moraceae)

The mutualism between fig plants and fig wasps has been recognized as one of the most specialized systems of symbiosis. Figs are pollinated by their highly specific pollinating fig wasps, and the pollinating fig wasps are raised within the syconia of figs. Recent studies indicated a difference between monoecious and dioecious figs in the dispersal range of pollinating wasps, which has potential consequences for gene flow. In this study, we detected the gene-flow pattern of the dioecious climbing fig, Ficus pumila L. var. pumila, at both local and regional scales. At the local scale, spatial autocorrelation analysis indicated strong genetic structure at short distances, a pattern of limited gene flow. This result was also supported by a high inbreeding coefficient (F _IS = 0.287) and significant substructuring (F _ST = 0.060; P < 0.001). Further analysis indicated that the effective gene dispersal range was 1,211 m, and the relative contribution of seed dispersal was smaller than that of pollen dispersal. The inferred effective range of pollen dispersal ranged from 989 to 1,712 m, while the effective seed dispersal range was less than 989 m. Lack of long-distance dispersal agents may explain the limited seed dispersal. The high density of receptive fig trees was the most likely explanation for limited pollen dispersal, and the position of syconia and relatively low wind speed beneath the canopy may contribute to this phenomenon. At the regional scale, significant negative correlations (kinship coefficient F _ij ranging from −0.038 to −0.071) existed in all comparisons between the studied population and other populations, and the assignment test grouped almost all individuals of the studied population into a distinct cluster. Asynchronous flowering on the regional scale, which provides a barrier for the pollinating wasps to fly from the studied population to the other populations, is probably responsible for the limited gene flow on the regional scale.     

Pollination by sexual deception promotes outcrossing and mate diversity in self‐compatible clonal orchids

The majority of flowering plants rely on animals as pollen vectors. Thus, plant mating systems and pollen dispersal are strongly influenced by pollinator behaviour. In Australian sexually deceptive orchids pollinated by male thynnine wasps, outcrossing and extensive pollen flow is predicted due to floral deception, which minimizes multiple flower visitations within patches, and the movement of pollinators under mate‐search rather than foraging behaviours. This hypothesis was tested using microsatellite markers to reconstruct and infer paternity in two clonal, self‐compatible orchids. Offspring from naturally pollinated Chiloglottis valida and C. aff. jeanesii were acquired through symbiotic culture of seeds collected over three seasons. In both species, outcrossing was extensive (t_m = 0.924–1.00) despite clone sizes up to 11 m wide. The median pollen flow distance based on paternity for both taxa combined was 14.5 m (n = 18, range 0–69 m), being larger than typically found by paternity analyses in other herbaceous plants. Unexpectedly for orchids, some capsules were sired by more than one father, with an average of 1.35 pollen donors per fruit. This is the first genetic confirmation of polyandry in orchid capsules. Further, we report a possible link between multiple paternity and increased seed fitness. Together, these results demonstrate that deceptive pollination by mate‐searching wasps enhances offspring fitness by promoting both outcrossing and within‐fruit paternal diversity.     

Long‐distance dispersal in a fire‐ and livestock‐protected savanna

Savannas are highly diverse and dynamic environments that can shift to forest formations due to protection policies. Long‐distance dispersal may shape the genetic structure of these new closed forest formations. We analyzed eight microsatellite loci using a single‐time approach to understand contemporary pollen and effective seed dispersal of the tropical tree, Copaifera langsdorffii Desf. (Fabaceae), occurring in a Brazilian fire‐ and livestock‐protected savanna. We sampled all adult trees found within a 10.24 ha permanent plot, young trees within a subplot of 1.44 ha and open‐pollinated seeds. We detected a very high level of genetic diversity among the three generations in the studied plot. Parentage analysis revealed high pollen immigration rate (0.64) and a mean contemporary pollen dispersal distance of 74 m. In addition, half‐sib production was 1.8 times higher than full‐sibs in significant higher distances, indicating foraging activity preference for different trees at long distances. There was a significant and negative correlation between diameter at breast height (DBH) of the pollen donor with the number of seeds (r = ?0.640, P‐value = 0.032), suggesting that pollen donor trees with a higher DBH produce less seeds. The mean distance of realized seed dispersal (recruitment kernel) was 135 m due to the large home range dispersers (birds and mammals) in the area. The small magnitude of spatial genetic structure found in young trees may be a consequence of overlapping seed shadows and increased tree density. Our results show the positive side of closed canopy expansion, where animal activities regarding pollination and seed dispersal are extremely high.     

Short-distance pollen dispersal and high self-pollination in a bat-pollinated neotropical tree

We investigated pollen dispersal and breeding structure in the tropical tree species Caryocar brasiliense Camb. (Caryocaraceae), using genetic data from ten microsatellite loci. All adult trees (101) within a patch of 8.3 ha were sampled, and from these adults 18 open-pollinated maternal progeny arrays were analyzed (280 seeds from 265 fruits). Most fruits presented only one seed (median equal to 1.000) and mean number of ripened seeds per fruit was 1.053 (SD = 0.828). Our results showed that C. brasiliense presents a mixed-mating system, with 11.4% of self-pollination, multilocus outcrossing rate of t _m = 0.891 ± 0.025, and high probability of full-sibship within progeny arrays (r _p = 0.135 ± 0.032). Outcrossing rate and self-pollination varied significantly among mother trees. We could detect a maximum pollen dispersal distance of ∼500 m and a mean pollen dispersal distance of ∼132 m. However, most pollination events (80%) occurred at distances less than 200 m. Our results also indicated that pollen dispersal is restricted to a neighborhood of 5.4 ha with rare events of immigration (∼1% N _e m = 0.35). C. brasiliense also presents a significant but weak spatial genetic structure (Sp = 0.0116), and extension of pollen dispersal distance was greater than seed dispersal (N _b = 86.20 m). These results are most likely due to the foraging behavior of pollinators that may have limited flight range. The highly within-population synchronous flowering, high population density, and clumped distribution reinforce pollinator behavior and affect residence time leading to a short-distance pollen dispersal.     

Habitat fragmentation influences genetic diversity and differentiation: Fine‐scale population structure of Cercis canadensis (eastern redbud)

Forest fragmentation may negatively affect plants through reduced genetic diversity and increased population structure due to habitat isolation, decreased population size, and disturbance of pollen‐seed dispersal mechanisms. However, in the case of tree species, effective pollen‐seed dispersal, mating system, and ecological dynamics may help the species overcome the negative effect of forest fragmentation. A fine‐scale population genetics study can shed light on the postfragmentation genetic diversity and structure of a species. Here, we present the genetic diversity and population structure of Cercis canadensis L. (eastern redbud) wild populations on a fine scale within fragmented areas centered around the borders of Georgia–Tennessee, USA. We hypothesized high genetic diversity among the collections of C. canadensis distributed across smaller geographical ranges. Fifteen microsatellite loci were used to genotype 172 individuals from 18 unmanaged and naturally occurring collection sites. Our results indicated presence of population structure, overall high genetic diversity (H_E = 0.63, H_O = 0.34), and moderate genetic differentiation (F_ST = 0.14) among the collection sites. Two major genetic clusters within the smaller geographical distribution were revealed by STRUCTURE. Our data suggest that native C. canadensis populations in the fragmented area around the Georgia–Tennessee border were able to maintain high levels of genetic diversity, despite the presence of considerable spatial genetic structure. As habitat isolation may negatively affect gene flow of outcrossing species across time, consequences of habitat fragmentation should be regularly monitored for this and other forest species. This study also has important implications for habitat management efforts and future breeding programs.     

Evaluating contemporary pollen dispersal in two common grassland species Ranunculus bulbosus L. (Ranunculaceae) and Trifolium montanum L. (Fabaceae) using an experimental approach

Pollen flow is a key biological process that connects plant populations, preventing genetic impoverishment and inbreeding. Pollen‐mediated long‐distance dispersal (LDD) events are especially important for plant species in increasingly fragmented landscapes. Patterns of pollen dispersal were directly estimated and dispersal kernels modelled in an experimental population of Ranunculus bulbosus and Trifolium montanum to determine the potential for LDD. Eight and 11 microsatellite markers were used for R. bulbosus and T. montanum, respectively, to run a likelihood‐based paternity analysis on randomly chosen offspring (N_total = 180 per species) from five maternal plants. High rates of selfing were found in R. bulbosus (average 45.7%), while no selfing was observed in T. montanum. The majority (60%) of mating events occurred at very short distances: the median of the observed dispersal distances was 0.8 m in both species, and the average distances were 15.9 and 10.3 m in R. bulbosus and T. montanum, respectively. Modelling the pollen dispersal kernel with four different distribution functions (exponential‐power, geometric, 2Dt and Weibull) indicated that the best fit for both species was given by a Weibull function. Yet, the tail of the T. montanum pollen dispersal kernel was thinner than in R. bulbosus, suggesting that the probability for LDD is higher in the latter species. Even though the majority of pollen dispersal occurred across short distances, the detection of several mating events up to 362 m (R. bulbosus) and 324 m (T. montanum) suggests that pollen flow may be sufficient to ensure population connectivity in these herb species across fragmented grasslands in Swiss agricultural landscapes.     

Relative importance of pollen and seed dispersal across a Neotropical mountain landscape for an epiphytic orchid

Populations of many species are isolated within narrow elevation bands of Neotropical mountain habitat, and how well dispersal maintains genetic connectivity is unknown. We asked whether genetic structure of an epiphytic orchid, Epidendrum firmum, corresponds to gaps between Costa Rican mountain ranges, and how these gaps influence pollen and seed flow. We predicted that significant genetic structure exists among mountain ranges due to different colonization histories and limited gene flow. Furthermore, we predicted that pollen movement contributes more to gene flow than seeds because seeds are released into strong winds perpendicular to the narrow northwest–southeast species distribution, while the likely pollinators are strong fliers. Individuals from 12 populations and three mountain ranges were genotyped with nuclear microsatellites (nDNA) and chloroplast sequences (cpDNA). Genetic diversity was high for both markers, while nDNA genetic structure was low (F_STn = 0.020) and cpDNA structure was moderate (F_STc = 0.443). Significant cpDNA barriers occurred within and among mountain ranges, but nDNA barriers were not significant after accounting for geographic distance. Consistent with these contrasting patterns of genetic structure, pollen contributes substantially more to gene flow among populations than seed (m_p/m_s = 46). Pollinators mediated extensive gene flow, eroding nDNA colonization footprints, while seed flow was comparatively limited, possibly due to directional prevailing winds across linearly distributed populations. Dispersal traits alone may not accurately inform predictions about gene flow or genetic structure, supporting the need for research into the potentially crucial role of pollinators and landscape context in gene flow among isolated populations.     

Contemporary pollen flow,mating patterns and effective population size inferred from paternity analysis in a small fragmented population of the Neotropical tree <Emphasis Type="Italic">Copaifera langsdorffii</Emphasis> Desf. (Leguminosae-Caesalpinioideae)

Pollen flow and dispersal patterns were investigated in a small, isolated forest fragment of the Neotropical insect pollinated tree Copaifera langsdorffii, using paternity analysis and eight microsatellite loci. We also investigated the coancestry and effective population size of progeny arrays for conservation and environmental restoration purposes. Open-pollinated seeds were collected from 15 seed trees within the forest fragment, in which all adult trees were mapped, measured and genotyped. Twenty seeds were also collected from the nearest neighbor tree located 1.2 km from the forest fragment. Our results show that levels of genetic diversity were significantly higher in adults than offspring and significant levels of inbreeding were detected in offspring (F = 0.226). From paternity analysis, we observed low levels of selfing (s = 8%) and pollen immigration (m = 8%) in the fragment, but very high levels were detected for the isolated tree (s = 20%; m = 75%), indicating that the population and the tree are not reproductively isolated and are connected by patterns of long distance pollen dispersal (maximum detected 1,420 m). Within the forest fragment, the pattern of pollen dispersal was a near neighbor pattern with 49% of the pollen being dispersed within 50 m. The effective population size of the progeny array was low, indicating the need to collect seeds from a large number of seed trees (at least 76) for conservation purposes. The results show that the spatial isolation of the population and isolated tree due to forest fragmentation has not disrupted genetic connectivity; however, spatial isolation does seem to increase selfing and correlated mating.     

Airborne‐pollen pool and mating pattern in a hybrid zone between Pinus pumila and P. parviflora var. pentaphylla

The reproductive isolation barriers and the mating patterns among Pinus pumila, P. parviflora var. pentaphylla and their hybrids were examined by flowering phenology and genetic assays of three life stages: airborne‐pollen grains, adults and seeds, in a hybrid zone on Mount Apoi, Hokkaido, Japan. Chloroplast DNA composition of the airborne‐pollen was determined by single‐pollen polymerase chain reaction. Mating patterns were analysed by estimating the molecular hybrid index of the seed parent, their seed embryos and pollen parents. The observation of flowering phenology showed that the flowering of P. pumila precedes that of P. parviflora var. pentaphylla by about 6 to 10 days within the same altitudinal ranges. Although this prezygotic isolation barrier is effective, the genetic assay of airborne‐pollen showed that the two pine species, particularly P. pumila, still have chances to form F₁ hybrid seeds. Both parental species showed a strong assortative mating pattern; F₁ seeds were found in only 1.4% of seeds from P. pumila mother trees and not at all in P. parviflora var. pentaphylla. The assortative mating was concluded as the combined result of flowering time differentiation and cross‐incompatibility. In contrast to the parental species, hybrids were fertilized evenly by the two parental species and themselves. The breakdown of prezygotic barriers (intermediate flowering phenology) and cross‐incompatibility may account for the unselective mating. It is suggested that introgression is ongoing on Mount Apoi through backcrossing between hybrids and parental species, despite strong isolation barriers between the parental species.     

When genes move farther than offspring: gene flow by male gamete dispersal in the highly philopatric bat species Thyroptera tricolor

For species characterized by philopatry of both sexes, mate selection represents an important behaviour for inbreeding avoidance, yet the implications for gene flow are rarely quantified. Here, we present evidence of male gamete‐mediated gene flow resulting from extra‐group mating in Spix's disc‐winged bat, Thyroptera tricolor, a species which demonstrates all‐offspring philopatry. We used microsatellite and capture–recapture data to characterize social group structure and the distribution of mated pairs at two sites in southwestern Costa Rica over four breeding seasons. Relatedness and genetic spatial autocorrelation analyses indicated strong kinship within groups and over short distances (<50 m), resulting from matrilineal group structure and small roosting home ranges (~0.2 ha). Despite high relatedness among‐group members, observed inbreeding coefficients were low (F_IS = 0.010 and 0.037). Parentage analysis indicated mothers and offspring belonged to the same social group, while fathers belonged to different groups, separated by large distances (~500 m) when compared to roosting home ranges. Simulated random mating indicated mate choice was not based on intermediate levels of relatedness, and mated pairs were less related than adults within social groups on average. Isolation‐by‐distance (IBD) models of genetic neighbourhood area based on father–offspring distances provided direct estimates of mean gamete dispersal distances () > 10 roosting home range equivalents. Indirect estimates based on genetic distance provided even larger estimates of , indicating direct estimates were biased low. These results suggest extra‐group mating reduces the incidence of inbreeding in T. tricolor, and male gamete dispersal facilitates gene flow in lieu of natal dispersal of young.     

Spatiotemporal mating pattern variation in a wind‐pollinated Mediterranean shrub

Spatiotemporal variation in mating patterns is poorly known in wind‐pollinated plant species. Here, we analysed mating patterns of the wind‐pollinated dioecious shrub Pistacia lentiscus by genotyping 904 seeds from 30 mother plants with eight microsatellite markers in a high‐density population in two consecutive flowering seasons. We found significant differences in some mating system estimates between years, particularly in the levels of correlated paternity. Overall, within‐mothers correlated paternity was higher in 2007 than in 2006 (r_pWM = 0.085 and 0.030), which translated into an effective number of fathers (N_ep) of 11.8 and 33.6 respectively. Using a smoothing interpolation technique, we show that the effective pollen cloud was spatially structured in patches of high‐ and low‐genetic diversity, which do not remain constant from year to year. In 2006, the among‐mothers correlated paternity (r_pAM) showed no trend with distance, suggesting no restriction of pollen dispersal. However, in 2007, r_pAM was greater than zero at short distances, revealing the existence of small‐scale patterns of pollen dispersal. The fact that the studied seasons were climatically homogeneous during the flowering time suggested that the observed differences might be ascribed to between‐year phenological variation of individuals in the studied population or other (unknown) factors. Numerical simulations, based on the real data set, indicated that the clumping of males and decreasing plant density, which is related to different types of pollen limitation, greatly increase correlated mating in this wind‐pollinated species, which is of relevance under the frame of the continuous anthropogenic habitat disturbance suffered by Mediterranean ecosystems.     

Outcrossing rates in two self‐compatible,hybridising Rhinanthus species: implications for hybrid formation

The congeners Rhinanthus angustifolius and Rhinanthus minor, two annual hemiparasites pollinated by bumblebees, are known to hybridise in the wild. Both species are self‐compatible, but the capacity for autonomous selfing is higher in R. minor. This suggests a difference in realized outcrossing rates, which have not been determined before in these species. Using microsatellites, both species turned out to have mixed mating systems, but with a much lower multilocus outcrossing rate (0.13) for R. minor compared to R. angustifolius (0.76). We hypothesised that a higher outcrossing rate should lead to a higher chance of heterospecific pollination, and we therefore determined the rate of hybrid formation on each species in an artificial mixed population. Hybrid seeds were produced at low frequency (4.5%), and no significant difference was found between the species. It is therefore likely that post‐pollination processes influence hybrid seed formation to counteract the expected difference in heterospecific pollen deposition. We checked fruit set, seed set and the rate of autonomous selfing in controlled crosses in the greenhouse in 2 years, and found that fruit set (2003) or seed set (2010) were lower in R. angustifolius × R. minor crosses relative to the reciprocal cross. Hybrid seeds produced on R. angustifolius also had a much lower germination rate, so most of the established F₁ hybrid plants have the R. minor cytoplasm. The formation of advanced hybrids depends on pollinator preference, which is biased towards R. angustifolius if present in sufficient numbers, because it offers more rewards.     

Individual and Temporal Variation in Outcrossing Rates and Pollen Flow Patterns in Ceiba pentandra (Malvaceae: Bombacoidea)

Ceiba pentandra is a tropical tree with high rates of selfing in some populations. In mixed‐mating species, variation in selfing is due to changes in adult density or variability of incompatibility systems. The effect of spatial isolation and phenology on selfing rates and pollen flow distances was analyzed using microsatellites in a fragmented population of Ceiba pentandra, in southern Costa Rica. Adult trees within a heterogeneous landscape were classified as grouped or isolated. We compared selfing rates at the individual level, between isolation conditions and 2 yr (2007, 2009), which differed in the number of flowering individuals. Mixed mating was estimated in both years (t_m = 0.624–0.759). Trees mated predominantly by outcrossing, while only a few trees reproduced through selfing. Spatial isolation did not significantly affect outcrossing rates. The progeny of grouped trees was mostly sired by near‐neighbors (<1 km) and by long‐distance pollen flow events in isolated trees. A reduction in the number of flowering individuals in 2009 reduced near‐neighbor matings, increased selfing in grouped trees, and decreased the number of unsampled sires in the progeny. Comparing selfing rates on individuals that flowered in both reproductive periods suggests a flexible mating system. Variation in self‐fertilization rates in this population appears to depend on variation of individual traits, such as genetic variability in self‐incompatibility genes, but it is independent of landscape heterogeneity. In contrast, pollen flow distances depend on local tree density as bats concentrate their foraging between near individuals to maximize energy efficiency.     

Sperm dispersal distances estimated by parentage analysis in a brooding scleractinian coral

Within populations of brooding sessile corals, sperm dispersal constitutes the mechanism by which gametes interact and mating occurs, and forms the first link in the network of processes that determine specieswide connectivity patterns. However, almost nothing is known about sperm dispersal for any internally fertilizing coral. In this study, we conducted a parentage analysis on coral larvae collected from an area of mapped colonies, to measure the distance sperm disperses for the first time in a reef‐building coral and estimated the mating system characteristics of a recently identified putative cryptic species within the Seriatopora hystrix complex (ShA; Warner et al. 2015). We defined consensus criteria among several replicated methods (colony 2.0, cervus 3.0, mltr v3.2) to maximize accuracy in paternity assignments. Thirteen progeny arrays indicated that this putative species produces exclusively sexually derived, primarily outcrossed larvae (mean t_m = 0.999) in multiple paternity broods (mean r_p = 0.119). Self‐fertilization was directly detected at low frequency for all broods combined (2.8%), but comprised 23% of matings in one brood. Although over 82% of mating occurred between colonies within 10 m of each other (mean sperm dispersal = 5.5 m ± 4.37 SD), we found no evidence of inbreeding in the established population. Restricted dispersal of sperm compared to slightly greater larval dispersal appears to limit inbreeding among close relatives in this cryptic species. Our findings establish a good basis for further work on sperm dispersal in brooding corals and provide the first information about the mating system of a newly identified and abundant cryptic species.     

Understanding the genetic diversity, spatial genetic structure and mating system at the hierarchical levels of fruits and individuals of a continuous Theobroma cacao population from the Brazilian Amazon

Understanding the mating patterns of populations of tree species is a key component of ex situ genetic conservation. In this study, we analysed the genetic diversity, spatial genetic structure (SGS) and mating system at the hierarchical levels of fruits and individuals as well as pollen dispersal patterns in a continuous population of Theobroma cacao in Pará State, Brazil. A total of 156 individuals in a 0.56 ha plot were mapped and genotyped for nine microsatellite loci. For the mating system analyses, 50 seeds were collected from nine seed trees by sampling five fruits per tree (10 seeds per fruit). Among the 156 individuals, 127 had unique multilocus genotypes, and the remaining were clones. The population was spatially aggregated; it demonstrated a significant SGS up to 15 m that could be attributed primarily to the presence of clones. However, the short seed dispersal distance also contributed to this pattern. Population matings occurred mainly via outcrossing, but selfing was observed in some seed trees, which indicated the presence of individual variation for self-incompatibility. The matings were also correlated, especially within ($\widehat{r}$_p(m)=0.607) rather than among the fruits ($\widehat{r}$_p(m)=0.099), which suggested that a small number of pollen donors fertilised each fruit. The paternity analysis suggested a high proportion of pollen migration (61.3%), although within the plot, most of the pollen dispersal encompassed short distances (28 m). The determination of these novel parameters provides the fundamental information required to establish long-term ex situ conservation strategies for this important tropical species.     

The relative contributions of seed and pollen dispersal to gene flow and genetic diversity in seedlings of a tropical palm

Seed and pollen dispersal shape patterns of gene flow and genetic diversity in plants. Pollen is generally thought to travel longer distances than seeds, but seeds determine the ultimate location of gametes. Resolving how interactions between these two dispersal processes shape microevolutionary processes is a long‐standing research priority. We unambiguously isolated the separate and combined contributions of these two dispersal processes in seedlings of the animal‐dispersed palm Oenocarpus bataua to address two questions. First, what is the spatial extent of pollen versus seed movement in a system characterized by long‐distance seed dispersal? Second, how does seed dispersal mediate seedling genetic diversity? Despite evidence of frequent long‐distance seed dispersal, we found that pollen moves much further than seeds. Nonetheless, seed dispersal ultimately mediates genetic diversity and fine‐scale spatial genetic structure. Compared to undispersed seedlings, seedlings dispersed by vertebrates were characterized by higher female gametic and diploid seedling diversity and weaker fine‐scale spatial genetic structure for female gametes, male gametes and diploid seedlings. Interestingly, the diversity of maternal seed sources at seed deposition sites (N _em) was associated with higher effective number of pollen sources (N _ep), higher effective number of parents (N _e) and weaker spatial genetic structure, whereas seed dispersal distance had little impact on these or other parameters we measured. These findings highlight the importance maternal seed source diversity (N _em) at frugivore seed deposition sites in driving emergent patterns of fine‐scale genetic diversity and structure.