Pollen and seed dispersal of Brazil nut trees in the southwestern Brazilian Amazon

ABSTRACT Pollen and seed dispersal patterns greatly influence the spatial distribution of plant genetic diversity. Microsatellite-based parentage analysis provides accurate estimates of contemporary gene dispersal. Although most tropical trees have been shown to exhibit widespread pollen dispersal, few studies have estimated contemporary gene dispersal after seedling establishment. Bertholletia excelsa (Lecythidaceae) is pollinated by large-bodied bees, while previous seed-tracking experiments suggest their seeds are mainly dispersed across very short distances by scatter-hoarding rodents, who primarily act as seed predators. Here we used parentage analysis to provide contemporary estimates of pollen and seed dispersal in B. excelsa recruits. We examined six 25-ha plots located in two natural stands in the Acre River valley, in the southwestern Brazilian Amazon. We used 11 microsatellite markers to estimate genetic diversity and fixation index parameters in adults, seedlings and saplings. Genetic diversity was moderate and did not differ across size classes or sampling locations. We assigned pollen and seed parents for < 20% of the recruits, indicating that most events of realized gene flow occurred beyond our 25-ha plots. Only 10 parentage assignments were confirmed with 80% confidence. Pollen distance ranged from 33 to 372 m and seed dispersal from 58 to 655 m. Actual seed-dispersal distances were far greater than the estimates obtained in previous seed-tracking experiments. Thus, studies encompassing larger sampling areas are necessary to determine a more representative spatial scale of B. excelsa’s pollen and seed dispersal capacity in natural stands.

Parent-parent and parent-offspring distances inSpondias radlkoferiseeds suggest long-distance pollen and seed dispersal: evidence from latrines of the spider monkey

Pollen and seed dispersal are key ecological processes, directly impacting the spatial distribution, abundance and genetic structure of plant populations; yet, pollen- and seed-dispersal distances are poorly known. We used molecular markers to identify the parental origin (n = 152 adult trees) of 177Spondias radlkoferi(Anacardiaceae) seeds deposited by the spider monkey (Ateles geoffroyi) in latrines located beneath 17 sleeping-trees in two continuous forest sites (CF) and two forest fragments (FF) in the Lacandona rain forest, Mexico. We estimated mean parent-offspring (PO) distances per latrine and, for those seeds (54% of seeds) with more than one candidate parent (i.e. the potential maternal and parental parents), we also estimated parent-parent (PP) distances per latrine, and tested if PO and PP distances differed between forest types. Global PO and PP distances per latrine averaged 682 m (range = 83–1741 m) and 610 m (range = 74–2339 m), respectively, and did not differ significantly between CF and FF. This suggests that pollen dispersal is extensive in both forest types and that long seed dispersal distances (>100 m) are common, thus supporting the hypothesis that the spider monkey is an effective seed disperser ofS. radlkoferiin continuous and fragmented forests.