Pollen Dispersal Patterns Research Articles

Implications of mating system and pollen dispersal indices for management and conservation of the semi-arid species Prosopis flexuosa (Leguminosae)

Recruitment by fencing of semi-arid trees is a common woodland conservation strategy that may have both positive and negative implications. Domestic herbivores can act as efficient dispersal seed agents but they can also affect the survival and growth of the trees first stages. Prosopis flexuosa (algarrobo) woodlands represent the most important plant community in the Monte region in Argentina and as this resource is affected by deforestation, grazing, natural fires and replacement of natural ecosystems by croplands, in order to protect the “algarrobo” a reserve had been established. As efficient management and conservation program depends on the information on population structure and mating system, the objectives of this work were to estimate mating and pollen dispersal patterns in a wild P. flexuosa population from the Ñacuñan fenced to exclude domestic cattle for 40years. This population is mainly outcrosser (tm=0.996), sensitive to inbreeding depression at seed stage, having relative reduced pollen mediated gene dispersal distance (4.56–20.35m), which favors inbreeding as a consequence of mating between related individuals. Our results suggest that for ex situ conservation the distance that would be enough to avoid full sib sampling among harvested seed-trees is about 20m. Collecting seeds from different pods reduce the proportion of full sibs within progeny arrays. For in situ conservation it is important to take into account that forest patches separated by more than 250m are expected to be isolated, increasing the risk of genetic variability loss, inbreeding increase and population extinction. The results are discussed in reference to the “algarrobo” management program; while in some case excluding big mammals from the stands should be advisable, the interaction with long dispersal big herbivores might be considered as a strategy to promote increased outbreeding reducing the rate of mating between related individuals.

POLYMORPHISM OF SIMPLE SEQUENCE REPEAT REGIONS OF SULAWESI EBONY (DIOSPHYROS CELEBICA BAKH.) IN EXPERIMENTAL FOREST OF HASANUDDIN UNIVERSITY PROVENANCE

Polymerase Chain Reaction (PCR)-based molecular techniques have been used to detect the polymorphism in plants. The utilization of molecular markers plays essential role in germplasm characterization and plant breeding since the information of DNA marker technology can be exchanged between laboratories and should have standard method to be reproducible. The molecular aspect has been commonly linked to DNA isolation protocol and polymorphic molecular marker, thus can be used for molecular research recommendation purposes. The objectives of this study were to evaluate the capability of microsatellite marker of Ebenaceae Family for amplifying Ebony DNA, and to determine the appropriate PCR annealing temperatures. The DNA isolation of Ebony leaves from Experimental Forest of Hasanuddin University Provenance was carried out using Genomic DNA Mini Kit (Plant) Geneaid protocol. Nine of seventeen selected primers from the Genus Diospyros were able to amplify Ebony DNA. Amplification products produced polymorphic bands with different annealing temperatures (ranged from 53 to 56°C). These nine polymorphic primers will be recommended to use for future studies in genetic diversity as well as pollen dispersal pattern analyses.

Pollen contamination and nonrandom mating in a Eucalyptus camaldulensis Dehnh seedling seed orchard

Abstract Eucalyptus camaldulensis has potential for timber, energy, pulp and cellulose production in Brazil due to its ability to adapt to a variety of environmental conditions. The use of improved seeds, selected for economic growth traits, is necessary to increase productivity of commercial stands. Seed seedlings orchards (SSO) are one option for improved seed production. However, pollen contamination from unimproved populations, as well as non-random mating in the SSO, can decrease the predicted genetic gains in selected populations. Thus, we investigate the mating system, pollen flow and dispersal patterns in an E. camaldulensis SSO and progeny test (PT), established with seedlings collected in the SSO, using seven microsatellite loci. All trees in the SSO were mapped, sampled, and genotyped. For the PT, we sampled, genotyped, and measured the total height of seedlings from 25 families. We detected 10 % inbreeding in the PT, resulting mainly from selfing. Furthermore, we found a correlated mating rate of 18.5 % in the SSO, indicating that within the PT there are some full-sibs. Using paternity analysis, we found 14.7 % pollen contamination and a pattern of pollen dispersal between near neighbor trees in the SSO. We found 9.5 % of inbreeding depression for seedlings height. Due to pollen contamination and nonrandom mating in the SSO, the actual genetic gains for growth traits in the PT are probably lower than the predicted genetic gains. We discuss some management strategies in the SSO that can be used to increase genetic gains in commercial reforestation established using seeds collected from the SSO

Pollen dispersal patterns and population persistence in a small isolated population of Fagus crenata

The potential of long-distance pollen dispersal and the effects of small population size and population isolation on persistence of Fagus crenata populations were investigated in a small, severely isolated population (the Gofuku-ji population) and two other populations located within 7 km of this population (including 87 adult trees in total). Parentage analysis using 13 microsatellite loci showed that 94 of 100 seedlings derived from seeds collected from the Gofuku-ji population had parent pairs within this population, six had one parent within the population, and four of the six seedlings had alleles that were not detected in any of the three populations, indicating that some pollen is dispersed over distances exceeding 7 km. The estimated expected heterozygosity and effective population size were lower in the Gofuku-ji population than in previously examined large continuous populations. Therefore, levels of genetic diversity within the population may have been reduced by strong genetic drift and limitations of pollen- and seed-mediated gene flow associated with the small size and severe isolation. The contemporary mating pattern estimated at the seedling stage was biased toward outbreeding, which may be explained by possible processes: the level of inbreeding in the adult trees is increased; then, inbreeding frequently occurs but is rarely successful, while outbreeding successfully produces offspring. Additionally, high levels of significant linkage disequilibrium and higher numbers of alleles than expected under mutation–drift equilibrium from analyses of the populations’ evolutionary history suggest that the Gofuku-ji population may have experienced admixture before its severe isolation. Therefore, the persistence of the Gofuku-ji population is being adversely affected by the decrease in population size and severe isolation. Further studies of gene flow via pollen in other populations with various degrees of isolation could enhance our understanding of the effects of population isolation and long-distance pollen dispersal in F. crenata and similar species.

How do field margins contribute to the functional connectivity of insect-pollinated plants?

Habitat fragmentation generates a loss of functional connectivity detrimental to the persistence of biodiversity. The French agricultural intensification initiated in the 1950s has caused a decline in field margins. As field margins may facilitate species dispersal while providing socio-economic benefits, it is of interest to assess their contribution to the functional connectivity of insect-pollinated plants in agro-ecosystems. This will help develop appropriate management strategies mitigating fragmentation. We addressed this issue by studying the links between landscape structure and the patterns of abundance and pollen dispersal (using fluorescent dye particles) for two contrasted insect-pollinated plants occurring in field margins (Crepis sancta and Euphorbia serrata). We investigated the influence of field margins quality and of the surrounding matrix on pollen dispersal and compared the relevance of the least-cost algorithm with a straight-line approach to depict pollinators’ movements. The influence of landscape structure on plant abundance is species and scale-specific. Pollen dispersal decreases with distance from the source. For E. serrata, it was preferentially dispersed via field margins, confirming the relevance of the least-cost algorithm, while C. sancta dispersal followed a straight-line. Euphorbia serrata, which grows strictly on field margins with a greater dispersal ability and a more diversified pollinator guild than C. sancta, is less affected by land-use changes. Our study demonstrates the contrasting contributions of field margins to pollen dispersal as they may act as functional corridors favouring pollinators’ movement depending on the species of interest.

Modeling olive pollen intensity in the Mediterranean region through analysis of emission sources

Aerobiological monitoring of Olea europaea L. is of great interest in the Mediterranean basin because olive pollen is one of the most represented pollen types of the airborne spectrum for the Mediterranean region, and olive pollen is considered one of the major cause of pollinosis in this region. The main aim of this study was to develop an airborne-pollen map based on the Pollen Index across a 4-year period (2008–2011), to provide a continuous geographic map for pollen intensity that will have practical applications from the agronomical and allergological points of view. For this purpose, the main predictor variable was an index based on the distribution and abundance of potential sources of pollen emission, including intrinsic information about the general atmospheric patterns of pollen dispersal. In addition, meteorological variables were included in the modeling, together with spatial interpolation, to allow the definition of a spatial model of the Pollen Index from the main olive cultivation areas in the Mediterranean region. The results show marked differences with respect to the dispersal patterns associated to the altitudinal gradient. The findings indicate that areas located at an altitude above 300ma.s.l. receive greater amounts of olive pollen from shorter-distance pollen sources (maximum influence, 27km) with respect to areas lower than 300ma.s.l. (maximum influence, 59km).

What influences pollen dispersal in the clonal distylous Menyanthes trifoliata (Menyanthaceae)?

Background and aims – Habitat fragmentation may compromise population survival and decrease the ability to face environmental changes. Small and isolated populations in particular may suffer from disrupted pollination processes. However, a species’ response to fragmentation may vary according to life history traits. Understanding how pollen dispersal is shaped by population and life history traits such as mating system and clonal growth is therefore essential for assessing species’ response to fragmentation. Methods – We investigated pollen dispersal using fluorescent dyes in nine Belgian populations in two regions of the distylous insect-pollinated clonal herb Menyanthes trifoliata. We examined whether overall and legitimate (i.e. between-morph) dye dispersal patterns differed between morphs and regions, and whether they were influenced by population traits (size, area, plant density, morph ratio, co-flowering species) and individual plant traits (number of flowers). Key Results – No evidence of dye transfer between adjacent populations (distant from 1.3 to 11.8 km) was found, suggesting no or very restricted between-population pollen flow. Within-population dye dispersal followed a decaying, usually leptokurtic, distribution, with most dye deposition at short distances (80% at less than 1.9–49.1 m), and a maximum distance of 336.6 m. Pins and thrums as recipients or donors did not differ in dye dispersal. Legitimate dye dispersal was not less successful than overall dispersal despite spatial clumping of the morphs. The distribution was similar or simply shifted to longer distances. The proportion of dyed stigmas was positively related to flowering population size and within-population heterospecific floristic richness, and to the number of flowers when considering legitimate dye deposition at distances < 32 m. Conclusions – Our study highlights the effects of the spatial distance to dye source, population size and coflowering floral resources, i.e. population traits related to attractiveness to pollinators, on pollen dispersal patterns.

Modern pollen and its ecological relationships with the tropical deciduous forests of central Uttar Pradesh, India

The paucity of modern pollen-rain data from the central part of Uttar Pradesh is a significant barrier to understanding the Late Quaternary vegetation history from the northern region of India. The interplay between extant vegetation and the modern pollen assemblage from both natural and human-induced vegetation types is examined from Lucknow, as an aid for palaeoenvironmental reconstructions. A dataset of 25 surface pollen samples has been documented from the conservation forests of Kukrail, Lucknow (part of Central Ganga Plain). The palynodata reflect the mixed deciduous forest comprising Acacia, Butea, Salmalia, and Syzygium under a warm and humid climate in response to rainfall variations in the region. High monsoonal activity in and around the region is inferred from the presence of the Euphorbiaceae–Moraceae–Syzygium assemblage in the sediments. The marshy and aquatic taxa such as Cyperaceae, Nymphoides and Polygonaceae are strongly suggestive of the perennial waterlogged condition in the area. A striking signal of winter dryness is easily visible in the palynoassemblage, especially observed through Artemisia and Chenopodiaceae. The regular presence of pollen grains of conifers and other broad-leafed taxa including Alnus, Betula, Pinus and Quercus are suggestive of high wind activity from the higher altitudes. Anthropogenic activity is in continuous pace as reflected by the higher frequencies of cereal pollen (14–29%) and Brassicaceae (2–5%). The contrasting frequencies of extant floral taxa recovered in the form of pollen in varied surface samples are indicative of differential pollen production, dispersal and deposition patterns. Therefore, an attempt has been made to precisely observe the behavioural pattern of modern pollen deposition which could in turn help in assessing the expanse of pastoral practices and the depth of deterioration of pristine forests as well as in the reconstruction of past climate and vegetation shifts in Central Ganga Plain, India. A correlation of regional palynodata with other tropical regions of the Indian subcontinent as well as in a global context is required for better interpretation.

Variable Gene Dispersal Conditions and Spatial Deforestation Patterns Can Interact to Affect Tropical Tree Conservation Outcomes

Tropical lowland rain forest (TLRF) biodiversity is under threat from anthropogenic factors including deforestation which creates forest fragments of different sizes that can further undergo various internal patterns of logging. Such interventions can modify previous equilibrium abundance and spatial distribution patterns of offspring recruitment and/or pollen dispersal. Little is known about how these aspects of deforestation and fragmentation might synergistically affect TLRF tree recovery demographics and population genetics in newly formed forest fragments. To investigate these TLRF anthropogenic disturbance processes we used the computer program NEWGARDEN (NG), which models spatially-explicit, individual-based plant populations, to simulate 10% deforestation in six different spatial logging patterns for the plant functional type of a long-lived TLRF canopy tree species. Further, each logging pattern was analyzed under nine varying patterns of offspring versus pollen dispersal distances that could have arisen post-fragmentation. Results indicated that gene dispersal condition (especially via offspring) had a greater effect on population growth and genetic diversity retention (explaining 98.5% and 88.8% of the variance respectively) than spatial logging pattern (0.2% and 4.7% respectively), with ‘Near’ distance dispersal maximizing population growth and genetic diversity relative to distant dispersal. Within logged regions of the fragment, deforestation patterns closer to fragment borders more often exhibited lower population recovery rates and founding genetic diversity retention relative to more centrally located logging. These results suggest newly isolated fragments have populations that are more sensitive to the way in which their offspring and pollen dispersers are affected than the spatial pattern in which subsequent logging occurs, and that large variation in the recovery rates of different TLRF tree species attributable to altered gene dispersal regimens will be a likely outcome of fragmentation. Conservation implications include possible manual interventions (manual manipulations of offspring dispersers and/or pollinators) in forest fragments to increase population recovery and genetic diversity retention.

Pollen dispersal in fragmented populations of the dioecious wind-pollinated tree, Allocasuarina verticillata (drooping sheoak, drooping she-oak; Allocasuarinaceae).

Vegetation clearing, land modification and agricultural intensification have impacted on many ecological communities around the world. Understanding how species respond to fragmentation and the scales over which functionality is retained, can be critical for managing biodiversity in agricultural landscapes. Allocasuarina verticillata (drooping sheoak, drooping she-oak) is a dioecious, wind-pollinated and -dispersed species with key conservation values across southeastern Australia. But vegetation clearing associated with agricultural expansion has reduced the abundance and spatial distribution of this species in many regions. Spatial genetic structure, relatedness among trees, pollen dispersal and mating patterns were examined in fragmented A. verticillata populations selected to represent the types of remnants that now characterise this species. Short scale spatial genetic structure (5–25 m) and relatedness among trees were observed in most populations. Unexpectedly, the two male trees closest to each female did not have a reproductive advantage accounting for only 4–15% of the seed produced in larger populations. Biparental inbreeding was also generally low (<4%) with limited evidence of seed crop domination by some male trees. More male trees contributed to seed crops in linear remnants (mean 17) compared to those from patch remnants (mean 11.3) which may reflect differences in pollen dispersal within the two remnant types. On average, pollen travels ~100 m irrespective of remnant type but was also detected to have dispersed as far as 1 km in open landscapes. Low biparental inbreeding, limited reproductive assurance for near-neighbour and probably related males and variability in the distances over which females sample pollen pools suggest that some mechanism to prevent matings between relatives exists in this species.

Pollen flow of wheat under natural conditions in the Huanghuai River Wheat Region, China

abstractThe transgenic pollen spread is the main pathway of transgenic plant gene flow. The maximum distance of pollen dispersal (horizontal), the spatial dynamics of pollen movement (vertical), and the patterns of pollen dispersal are important considerations in biosafety assessments of genetically modified crops. To evaluate wheat (Triticum aestivum) pollen dispersal, we measured the pollen suspension velocity and analyzed pollen dispersal patterns under natural conditions in the Huanghuai River wheat-growing region in 2009. The pollen suspension velocity was 0.3–0.4 m/s. The highest pollen densities were detected in the north, northwest, and south of the pollen source. Pollen was dispersed over distances greater than 245 m in the northwest and northeast directions. At the pollen source center, pollen density decreased with increasing vertical height. In the north of the pollen source, the pollen density from 65 m to 225 m showed a wave-mode decrease with increasing height. The horizontal transport of pollen over longer distances fitted polynomial equations. In the north, the pollen density was highest at 45 m from the pollen source, and decreased with increasing distance. In the northwest, the pollen density showed a double-peak trend. In the northeast, pollen density was highest from 45 m to 125 m from the source. Wind speeds greater than the pollen suspension velocity and the duration of continuous gusts were the main factors affecting pollen dispersal. This information will be useful for determining the spatial isolation distances for hybrid seed production and for the commercial production of transgenic wheat.

Mating system and genetic diversity of progenies before and after logging: a case study of Bagassa guianensis (Moraceae), a low-density dioecious tree of the Amazonian forest

The logging of large trees in tropical forests causes a decrease in the density of reproductive individ- uals, which likely affects the pattern of pollen dispersal and the mating system of the remaining trees in the pop- ulation. Here, we investigate the impact of logging on mating system and genetic diversity of the low-density, thrip-pollinated, dioecious tree Bagassa guianensis with- in a 500-ha plot at Tapajos National Forest, Para State, Brazil. Mating system parameters of the logged popula- tion were estimated using mixed-mating model. Six mi- crosatellite loci were used to genotype 232 seeds from ten remnant female trees over three seasons (2006, 2007, and 2008). The data were compared with the mating system of the unlogged population of B. guianensis (18 female trees, 488 seeds) in the same plot. The overall number of alleles found in the open-pollinated progenies decreased after logging (K=71 before logging and K=57 after logging, considering the three after logging seasons pooled), as well as the average number of alleles per locus (A = 11.8 and 9.5, respectively). Similarly, the number of private alleles, which is defined in the context of this study as the number of alleles observed in the population exclusively before or after logging, also de- creased after logging (15 and 1, respectively). However, the average number of alleles per locus and the observed and expected heterozygosities were not significantly higher before logging than after logging. Logging also did not affect the inbreeding of progenies in the popula- tion. Somewhat unexpectedly, the effective number of pollen donors was consistently higher after (Nep =1 4.5 in 2006, 8.1 in 2007, and 6.3 in 2008) than before log- ging (Nep = 3.4), suggesting that the loss of alleles in the population was compensated by the higher heterogeneity in the pollen pool after the removal of the largest trees by logging. Potential causes explaining the patterns found here include the maintenance of large patches of forest around the logged plot and the species' ability to perform long-distance pollination by airborne thrips. Maintenance of landscape integrity as logged and unlogged forests around the exploited areas is recom- mended to enhance pollen migration and to avoid long- term losses in genetic diversity.

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 (Nep ) 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.

Flower biology and breeding system of Salvia sclareoides Brot. (Lamiaceae)

A remarkable diversity of floral adaptations and reproductive strategies has evolved in flowering plants as a result of natural selection mediated by pollinators. The form and functioning of sexual units determine the patterns of pollen dispersal and receipt and, together with post-pollination mechanisms including incompatibility systems, determine the plant reproductive fitness. Reproductive biology assumes a special importance in rare and endemic species due to restricted population/distribution sizes. Salvia sclareoides Brot. (Lamiaceae) is an endemic species of Iberian Peninsula with conservation interest for which little information is available. The aim of this work was to study the flower biology and breeding system of S. sclareoides and assess how reproductive traits, pollination services and herbivory affected the reproductive success of this species. One natural population was selected to study flower lifespan, floral rewards and sexual functioning and to determine the reproductive system; additionally, in three natural populations, pollen limitation and herbivory of sexual structures were quantified. Salvia sclareoides presents short-lived, nectar rewarding flowers arranged in inflorescences with several flowers simultaneously open. The flowers are protandrous, although the peak of pollen germinability and stigmatic receptivity coincided. Pollination experiments revealed that S. sclareoides is self-compatible, having some ability of spontaneous selfing. Still, the presence of pollinators significantly increased the reproductive success. Also, both quantitative and qualitative pollen limitation was observed. Finally, it was revealed that the reproductive success was also affected by herbivores that damaged significantly the sexual structures. The consequences of the obtained results for the dynamics of S. sclareoides populations are discussed.

Distance-dependent but genetically random mating in a Japanese beech (Fagus crenata) population

In plant populations, limited seed dispersal may generate the aggregation of related individuals, which is referred to as spatial genetic structure (SGS). If short-distance pollination frequently occurs in populations with SGS, it may lead to frequent mating between related individuals (biparental inbreeding). In this study, we examined patterns of pollen dispersal and inbreeding under such conditions in a population of the wind-pollinated tree species Fagus crenata Blume using microsatellite analyses of adult trees and dispersed seeds. The population showed weak but significant SGS and the pollen dispersal in the population involved a combination of distance-dependent (largely short-range) dispersion at the local scale and long-distance transport. Although SGS and distance-dependent pollination co-occurred, individual inbreeding coefficients for both adults and seeds were almost zero, suggesting that mating generating sound seeds was genetically random with little or no inbreeding, probably because of the weak SGS, long-distance pollen dispersal, and postpollination mechanisms including self-incompatibility and inbreeding depression. The production of sound seeds through genetically random mating may be important for maintaining F. crenata populations because the resulting seedlings may be less affected by inbreeding depression than those resulting from the mating of related individuals.

Extensive long-distance pollen dispersal and highly outcrossed mating in historically small and disjunct populations of Acacia woodmaniorum (Fabaceae), a rare banded iron formation endemic.

Background and AimsUnderstanding patterns of pollen dispersal and variation in mating systems provides insights into the evolutionary potential of plant species and how historically rare species with small disjunct populations persist over long time frames. This study aims to quantify the role of pollen dispersal and the mating system in maintaining contemporary levels of connectivity and facilitating persistence of small populations of the historically rare Acacia woodmaniorum.MethodsProgeny arrays of A. woodmaniorum were genotyped with nine polymorphic microsatellite markers. A low number of fathers contributed to seed within single pods; therefore, sampling to remove bias of correlated paternity was implemented for further analysis. Pollen immigration and mating system parameters were then assessed in eight populations of varying size and degree of isolation.Key ResultsPollen immigration into small disjunct populations was extensive (mean minimum estimate 40 % and mean maximum estimate 57 % of progeny) and dispersal occurred over large distances (≤1870m). Pollen immigration resulted in large effective population sizes and was sufficient to ensure adaptive and inbreeding connectivity in small disjunct populations. High outcrossing (mean tm = 0·975) and a lack of apparent inbreeding suggested that a self-incompatibility mechanism is operating. Population parameters, including size and degree of geographic disjunction, were not useful predictors of pollen dispersal or components of the mating system.ConclusionsExtensive long-distance pollen dispersal and a highly outcrossed mating system are likely to play a key role in maintaining genetic diversity and limiting negative genetic effects of inbreeding and drift in small disjunct populations of A. woodmaniorum. It is proposed that maintenance of genetic connectivity through habitat and pollinator conservation will be a key factor in the persistence of this and other historically rare species with similar extensive long-distance pollen dispersal and highly outcrossed mating systems.

Extensive pollen flow in a natural fragmented population of Patagonian cypress Austrocedrus chilensis

Habitat fragmentation might significantly affect mating and pollen dispersal patterns in plant populations, contributing to the decline of remnant populations. However, wind-pollinated species are able to disperse pollen at longer distances after opening of the canopy. Our objectives were to characterize the mating system parameters and to estimate the average distance of effective pollen dispersal in the wind- pollinated conifer Austrocedrus chilensis. We sampled 19 "mother trees," 200 progeny, and 81 additional adults (both male and female), in a fragmented population at the Argentinean Patagonian steppe. We registered the spatial po- sitions of individuals and genotyped all samples with five microsatellite markers. We found a high genetic diversity, a moderated rate of biparental inbreeding (tmts=0.105), and a complete absence of correlated paternity (rp=−0.015). The effective number of pollen donors contributing to a single mother (Nep) was 13.9. Applying TWOGENER,weestimated a low but significant differentiation among the inferred pollen pools (ΦFT=0.036,p=0.001) and a very large average pollen dispersal distance (d=1,032.3 m). The leptokurtic distribution (b=0.18) presumes a potential for even larger dispersal dis- tances. The high genetic diversity, the mating patterns, and the extensive pollen dispersal presume that habitat fragmentation did not have a negative impact on pollen movement in this population of A. chilensis. Genetic connectivity among fragmented populations scattered in the Patagonian region is possible, and we stress the need of management policies at the landscape level.

Stabilizing selection on nectar concentration in wild Petunia axillaris, as revealed by genetic analysis of pollen dispersal

Most animal-pollinated plants produce nectar as a pollinator reward. Despite the main role that nectar plays in plant-pollinator interactions, the impact of natural variation in nectar traits on realized male fitness is poorly known. Here, we assessed this relation for a wild Petunia axillaris population using paternity-based direct selection gradient analysis, which allowed us also to infer pollen dispersal patterns. Because male fecundity may depend on other traits which could be associated with nectar characteristics (i.e. volume and concentration), we also considered selection on other key reproductive traits. The analysis revealed that P. axillaris was a strict outcrosser, but that successful pollination occurred mainly among neighbours. Individual plants varied greatly in their male fecundity. Nectar concentration, a key feature of nectar that determines its profitability, was subjected to stabilizing selection. Selection through male function also affected corolla area (positive directional selection), corolla tube length (negative directional selection), and floral display size (stabilizing selection), but none of these traits were phenotypically correlated with nectar characteristics. Because nectar concentration affects the ability and foraging efficiency of different flower visitors to feed on nectar, stabilizing selection may reflect either the preference of the most effective pollinators, or antagonistic selection driven by pollinators and non-pollinating nectar consumers.

Long-distance pollen dispersal ensures genetic connectivity of the low-density tree species, Eurycorymbus cavaleriei, in a fragmented karst forest landscape

Karst forest in southwest China represents one of the world’s most spectacular examples of tropical-subtropical karst landscapes and harbours high floristic richness and endemism. Many plant species tend to occur in naturally isolated patches due to the edaphic and topographic heterogeneity and are suffering an increasing stress of habitat deterioration due to both extensive human activities and global climate change in the area. Here Eurycorymbus cavaleriei was selected as a representative insect-pollinated plant species with low density to assess the pollen dispersal and mating patterns of such limestone associated trees. Paternity analysis revealed substantial long-distance pollination events, with a high level of pollen immigration (27.9–41.9 %) from outside the study sites over distance of at least 4,000 m. Pollen dispersal best fits an exponential power model with a fat-tailed (b < 1) feature and the average pollen dispersal distance was over 2,000 m inferred by the twogener analysis. Despite the dioecious nature, a small amount of biparental inbreeding and moderate correlated paternity were detected based on the multilocus mating system analysis. Relatively few pollen donors (Nep = 3.5–7.0) and substantial variance in male reproductive success (21–24 % of males were responsible for 52–58 % of pollinations) were detected. These results have important implications for the genetic conservation and management of E. cavaleriei. Extensive pollen dispersal provides evidence for substantial intra- and/or inter-patch pollinator movement, which seems promising for E. cavaleriei and other trees with generalized pollination system in karst forest landscape.

Patterns of pollen dispersal in a small population of the Canarian endemic palm (Phoenix canariensis)

The genetic diversity of small populations is greatly influenced by local dispersal patterns and genetic connectivity among populations, with pollen dispersal being the major component of gene flow in many plants species. Patterns of pollen dispersal, mating system parameters and spatial genetic structure were investigated in a small isolated population of the emblematic palm Phoenix canariensis in Gran Canaria island (Canary Islands). All adult palms present in the study population (n=182), as well as 616 seeds collected from 22 female palms, were mapped and genotyped at 8 microsatellite loci. Mating system analysis revealed an average of 5.8 effective pollen donors (Nep) per female. There was strong variation in correlated paternity rates across maternal progenies (ranging from null to 0.9) that could not be explained by the location and density of local males around focal females. Paternity analysis revealed a mean effective pollen dispersal distance of ∼71 m, with ∼70% of effective pollen originating from a distance of <75 m, and 90% from <200 m. A spatially explicit mating model indicated a leptokurtic pollen dispersal kernel, significant pollen immigration (12%) from external palm groves and a directional pollen dispersal pattern that seems consistent with local altitudinal air movement. No evidence of inbreeding or genetic diversity erosion was found, but spatial genetic structure was detected in the small palm population. Overall, the results suggest substantial pollen dispersal over the studied population, genetic connectivity among different palm groves and some resilience to neutral genetic erosion and subsequently to fragmentation.