Explore the vast range of titles available.

1. Understanding the drivers and spatial scale of gene flow is essential for the management of species living in fragmented landscapes. In plants, contemporary pollen flow is typically modelled as a single spatial process, with pollen flow declining exponentially within a short distance of mother plants. However, growing evidence suggests that many species do not conform to these patterns, often showing an excess of long-distance dispersal events or sometimes even multimodality in dispersal kernels. This suggests that a single function might be insufficient to capture the true complexity of pollination, which in reality is often achieved by multiple pollinators that vary in their foraging ranges and interactions with the landscape. 2. We reconstructed realized pollen flow and assessed pollen immigration for seven populations of the insect-pollinated herb Pulsatilla vulgaris. We quantified the effects of distance, floral resources and landscape composition over multiple spatial scales and tested the hypotheses that within-population pollen flow is related to resources and landscape context measured locally, and that among-population pollen flow is related to features measured at larger spatial scales. 3. We found that pollen flow within populations was more likely to occur amongst near neighbours, but that among-population pollen flow was random with respect to source populations. We further found that local floral density could explain patterns of within-population pollination distances and population-level selfing rates, whereas pollen immigration rates were best explained by the proportion of forest within a radius of 500 m around focal populations. 4. Synthesis. Together, our results suggest that within- and among-population contemporary pollen flow may be governed by different underlying processes, possibly related to differences in the foraging range and habitat use of bee species that contribute to pollination at different scales. This highlights the critical need for researchers to take a more pollinator-eyed view of contemporary pollen flow in plants by (1) recognizing that within- and among-population gene flow by pollen may depend on different sets of pollinators that respond to features at different spatial scales (2) considering additional factors that may alter attractiveness, detectability and accessibility of plants to pollinators beyond the effects of distance.

Precise empirical data on current gene flow by pollen, both with respect to distance and abundance, is crucial to understand whether habitat fragments are functionally connected. Based on a large-scale inventory (approximately = 100 km2) in which all individuals of a naturally scattered forest tree (Sorbus domestica) were mapped, we inferred current gene flow by pollen using genetic paternity analysis. We detected an extensive network of effective pollen transfer. Although short pollen flow distances were most abundant, 10% of the assigned pollen donors were more than 2 km away from their female mating partners, and 1.8% were even at a distance of 12–16 km. This latter pollen flow shows that current long-distance gene flow over a fragmented landscape clearly occurs. Pollen dispersal was well described by a fat-tailed inverse curve. Using parentage analysis of established trees, maternally inherited chloroplast markers and diameter at breast height measurements as an indicator of individual tree age, we were able to infer regular seed dispersal distances over several hundred metres up to more than 10 km. We conclude that in temperate, insect-pollinated and animal-dispersed tree species such as S. domestica, fragmented subpopulations are functionally connected by gene flow through both pollen and seed.

Gene flow from an experimental plot of genetically modified eucalypt was studied by measuring pollen dispersal at various distances from the pollen donor up to a maximum distance of 1592 m. Spontaneous seedling establishment around mother trees, the potential receptors of GM pollen, was also verified. All trees analyzed in this study were identified as compatible for crossing with the pollen donor and their flowering time frame showed at least two weeks synchronism with GM pollen donors. As reported in previous studies, pollination occurred at short distances then declined rapidly within 200 m. The results obtained are consistent with data from other reports in different conditions. In the current study, only two GM seedlings out of 574 were detected at distances greater than 300 m from source (one at 400 and the other at 857 m), in rates varying from zero to 1.5% until 857 m, and null above this. Although effective GM crossings were found in compatible trees around the pollen donors, no spontaneous seedling establishment was observed.

Animal pollination is critical for maintaining the reproduction and genetic diversity of many plant species, especially those in tropical ecosystems. Despite the threat to pollination posed by tropical deforestation, it remains an understudied process. In particular, little is known about these dynamics in multi-paternal, successional plant species whose fruits can contain substantial genetic diversity. Given the importance of successional plants in reforestation, quantifying the factors that impact their reproduction is essential for understanding plant gene flow in the context of global change. In this study, we investigated pollen-mediated gene flow at the multi-paternal fruit level to quantify how tropical pollinators navigate and mediate gene flow in altered forests. Utilizing microsatellite genotyping and paternity analyses, we revealed that distinct plant neighborhood and individual factors drive pollen dispersal at the intra-fruit scale. Variance in pollen dispersal distances was greater for neighborhoods with higher conspecific density, indicating that density dependent reproductive patterns play a role at this scale. Additionally, both the diversity and evenness of sires mediated by a single pollinator were affected by the size of the mother tree, that is, larger mothers received pollen from a less diverse, less even pool of sires per fruit. Pollinator body size was not found to be a significant driver of pollen dispersal, indicating that both small-and large-bodied pollinators were equally important pollen dispersers at this scale. By exploring patterns of variation at the intra-fruit level, we show that conspecific density and tree size significantly impact multi-paternal pollen-mediated gene flow, reinforcing the importance of investigating intraspecific, intra-individual variance in plant reproduction.

In this study, the mating system, contemporary pollen flow, and landscape pollen connectivity of the wild olive tree (Olea europaea subsp. cuspidata) were analyzed in a fragmented landscape of less than 4-km diameter located in north-western Ethiopia. Four remnant populations of different sizes were investigated. Eight highly polymorphic microsatellite markers were used to genotype 534 adults and 704 embryos. We used contrasting sampling schemes and different methodological approaches to analyze the pollen flow. We observed a lower rate of inbreeding and correlated mating in the fragmented vs. the non-fragmented subpopulation. Using parentage analysis, we detected a bidirectional pollen movement across subpopulations. Pollen flow was found to be directed towards small subpopulations based on parentage and anisotropic analysis. Pollen immigration amounted to more than 50%. Although most pollination occurred within a distance of less than 200 m, longer distance pollen movements of more than 3 km were also detected. Pollen dispersal in the large and dense subpopulation was reduced, and a smaller number of effective pollen sources were detected compared to a smaller fragmented subpopulation. We obtained consistent estimates for the number of effective pollen donors (approximately 6 per mother tree) using three different methods. The average pollen dispersal distance at the landscape level amounted to 276 m while at the local level, 174 m was estimated. Bigger trees were better pollen contributors than smaller trees. We showed here for the first time that pollen dispersal in wild olive follows a leptokurtic distribution.

Pollinators influence patterns of plant speciation, and one intuitive hypothesis is that pollinators affect rates of plant diversification through their effects on pollen dispersal. By specifying mating events and pollen flow across the landscape, distinct types of pollinators may cause different opportunities for allopatric speciation. This pollen dispersal-dependent speciation hypothesis predicts that pollination mode has effects on the spatial context of mating events that scale up to impact population structure and rates of species formation. Here I consider recent comparative studies, including genetic analyses of plant mating events, population structure and comparative phylogenetic analyses, to examine evidence for this model. These studies suggest that highly mobile pollinators conduct greater gene flow within and among populations, compared to less mobile pollinators. These differences influence patterns of population structure across the landscape. However, the effects of pollination mode on speciation rates is less predictable. In some contexts, the predicted effects of pollen dispersal are outweighed by other factors that govern speciation rates. A multiscale approach to examine effects of pollination mode on plant mating system, population structure and rates of diversification is key to determining the role of pollen dispersal on plant speciation for model clades.

• Here, we studied the floral morphology and pollination of the distylous plant Linum suffruticosum (Linaceae) in southern Spain. • We observed a previously unreported form of distyly that involved twisting and bending of styles and stamens during floral development to achieve three-dimensional reciprocity of anthers and stigmas in the long-styled (pin) and short-styled (thrum) morphs. This developmental pattern causes pin pollen to be placed on the underside of pollinating Usia flies (Bombyliidae), and thrum pollen to be placed on the top of the thorax and abdomen. The pin stigmas contact the flies on the dorsum, apparently picking up predominantly thrum pollen, and the thrum stigmas contact the flies on the ventral surface, apparently picking up predominantly pin pollen. • This form of heterostyly would appear on morphological grounds to be far more efficient in dispersing pollen between compatible morphs than the typical pin-thrum system. If so, this plant fits Darwin's prediction of efficient pollen flow between heterostylous morphs more closely than anything Darwin himself reported. • Molecular phylogenetic analyses indicate that this form of heterostyly evolved in a lineage that already had typical heterostyly. The analyses also indicate that there have been several independent origins of heterostyly in Linum and at least one reversal to stylar monomorphism.

Our investigation aims to understand the genetic structure and evolutionary history of Petagnaea gussonei, an ancient and endangered species belonging to the Saniculoideae subfamily (Apiaceae). It is paleoendemic to Sicily, with a small number of populations in the Nebrodi Mountains. A total of seven chloroplast microsatellite repeat loci and 12 AFLP primer combinations were used to screen 115 individuals corresponding to 17 populations. The ratio of seed to pollen flow was also calculated using the modified Ennos equation. A relatively high level of genetic diversity was detected with AFLPs (e.g., 0.045 < H < 0.278), and a moderate variation was also found using cpSSRs (0 < Hk < 0.667). Two different haplotypes (B and W) were identified, with five populations being monomorphic for haplotype B. There was no genetic differentiation on the basis of haplotypic frequency (G ST) and similarity (R ST), and no phylogeographic structure was detected among the populations. AFLP values also confirmed that the populations are not very genetically differentiated. The principal component analysis based on pairwise genetic differences showed three groupings without a geographical correlation. The AMOVA analysis indicates that the amount of variation is higher within populations (82 %) than among populations (18 %). Results of the pollen flow/seed flow ratio indicated positive values for each population, indicating that gene flow by seed is not more efficient than by pollen. Instead, the total pollen/seed flow for all population presents a negative value, suggesting that pollen dispersal does not appear to be more effective over the long range for gene flow than seed dispersal. This differentiation level supports the hypothesis that the fragmentation and isolation of the residual populations is in progress. This phenomenon is due not only to post-ice age climate changes, but also to direct and indirect anthropic actions.

It remains unclear how related co-flowering species with shared pollinators minimize reproductive interference, given that the degree of interspecific pollen flow and its consequences are little known in natural communities. Differences in pollen size in six Pedicularis species with different style lengths permit us to measure heterospecific pollen transfer (HPT) between species pairs in sympatry. The role of pollen–pistil interactions in mitigating the effects of HPT was examined. Field observations over 2 yr showed that bumblebee pollinators visiting one species rarely moved to another. Heterospecific pollen (HP) comprised < 10% of total stigmatic pollen loads for each species over 2 yr, and was not related to conspecific pollen deposition. Species with longer styles generally received more HP per stigma. The pollen tube study showed that pollen from short-styled species could not grow the full length of the style of long-styled species. Pollen from long-styled species could grow through the short style of P. densispica, but P. densispica rarely received HP in nature. Flower constancy is a key pre-pollination barrier to HPT between co-flowering Pedicularis species. Post-pollination pollen–pistil interactions may further mitigate the effects of HPT because HP transferred to long styles could generally be effectively filtered.

The Brazil nut is a highly valuable non‐timber forest product from a wild, hyperdominant, emergent tree species that is increasingly vulnerable and exposed to habitat degradation. We provide evidence for how Brazil nut genetic resources are negatively affected by forest degradation and discuss the consequences of this for reproductive success. To avoid negative effects of genetic erosion and inbreeding, we discuss the need to cease large‐scale forest conversion and to promote landscape connectivity. This could support gene flow, maintain genetic diversity across individuals reproducing in clustered patterns, and contribute to securing the long‐termed reproductive viability and resilience of this high socio‐economically and ecologically valuable species. Societal Impact Statement The Brazil nut is a highly valuable non‐timber forest product from a wild, hyperdominant, emergent tree species that is increasingly vulnerable and exposed to habitat degradation. We provide evidence for how Brazil nut genetic resources are negatively affected by forest degradation and discuss the consequences of this for reproductive success. To avoid negative effects of genetic erosion and inbreeding, we discuss the need to cease large‐scale forest conversion and to promote landscape connectivity. This could support gene flow, maintain genetic diversity across individuals reproducing in clustered patterns and contribute to securing the long‐termed reproductive viability and resilience of this high socio‐economically and ecologically valuable species. Summary Ecosystem degradation in the Amazon drives this biodiverse rainforest toward an ecological tipping point. Sustainable management and restoration of degraded rainforest therein are central to counteract this crisis. One hyperdominant, keystone species of high ecological and socio‐economic value, the Brazil nut tree, offers additional benefits as a major carbon sink and a nutritional source of the most prominent globally traded non‐timber forest product. Despite Brazil nut trees being protected by conservation regulation, forest degradation threatens sufficient gene‐flow among Brazil nut tree populations. This has impacts on the reproductive success, genetic diversity, and consequently on the resilience of this species to environmental change. We used 13 microsatellite loci to explore the consequences of forest degradation on the reduction in genetic diversity of Brazil nut populations. We examined the clustering of genetically related individuals as fine‐scale genetic structure (FSGS) and the variation in genetic diversity and inbreeding across adult trees and seedlings along a categorized forest‐degradation gradient ranging from conserved to degraded areas. In addition, we applied direct and indirect approaches to estimate contemporary pollen‐mediated gene flow. We found significant levels of FSGS, comparable to other similar tropical tree species. Brazil nut seedlings had consistently lower genetic diversity and higher inbreeding than adults, significantly associated with the degree of forest degradation of their origin. We observed limited pollen dispersal, differential patterns in pollen heterogeneity, and disproportionate paternal‐assignment rates from few individuals shaping the effective population size in our dataset. We discuss how this evidence for reproduction vulnerability may affect the genetic resources and undermine the resilience of this ecological and socio‐economic system in Peru.