High rates of pollen and seed flow in Hymenaea stigonocarpa on a highly fragmented savanna landscape in Brazil

Abstract

Genetic diversity of tree populations is mainly determined by pollen and seed flow. In turn, dispersal agents are affected by landscape composition and configuration. Understanding the effects of anthropization on pollen and seed dispersal in natural environments is crucial to developing long-term strategies for in situ and ex situ conservation of Neotropical savanna tree species. Here, we evaluated the genotypic and genetic diversity, spatial genetic structure (SGS), and pollen and seed dispersal of the endangered tree species Hymenaea stigonocarpa in a 2200-ha plot established in a strongly fragmented savanna landscape in Brazil. A total of 157 individuals were identified, 66 juveniles and 91 adults. Height, root-collar diameter for juveniles and diameter at breast height for adults were determined for each individual, and leaves were sampled to be used in genotyping by microsatellites. Genotypic diversity ( $$R$$ ) was similarly high in adults (0.87) and juveniles (0.80), indicating more sexual reproduction than clonal. Heterozygosities were also similar between both generations, and no inbreeding was detected. Adults and juveniles present SGS, but the extent measured by the $$Sp$$ -statistic was not significant. Both pollen and seed flow were elevated (24.2%) and reached long distances (3778 m and 3914 m, respectively) within the sampled area, but the pattern was not fat-tailed, indicating that most dispersal was over shorter distances. We conclude that fragmentation does not reproductively isolate the sampled population because individuals located outside the area may serve as sources of gene flow between remnant forest patches; however, the probability of dispersal over long distances is reduced.