Short-distance pollen dispersal in a protogynous Annonaceae tree species from the Brazilian Cerrado

Abstract

Annona crassiflora (Annonaceae) is a protogynous beetle-pollinated savannah tree species, widely distributed in the savannahs of the Cerrado biome. Studies on the mating system and pollen dispersal of protogynous species are very scarce. Here, we used six microsatellite loci to assess the mating system and pollen dispersal of A. crassiflora in a savannah remnant in Central Brazil. We mapped and sampled leaves of 112 adult trees and collected 74 fruits from 20 mother trees (1–4 fruits per plant) to obtain the seeds used (460) for mating system and parentage analyses. Annona crassiflora has predominantly allogamous mating systems, with a high multilocus outcrossing rate (tm = 0.974, SE = 0.011) that did not differ among mother trees (F = 1.32, p = 0.165). However, tm–ts was variable among seed trees, indicating that some seeds were produced by mating among relatives. Our results also showed multiple paternity within fruits. Multilocus correlation of outcrossed paternity was high (rp = 0.302, SE = 0.045), indicating that for each mother tree, the probability that the same pollen donor sired two random sibs was 30.2%, and the mean number of pollen donors per mother tree was high (6.3). We detected a maximum pollen dispersal distance of 360.7 m and an average of 124.3 m (SD = 80 m), but most pollination events (73%) occurred at shorter distances (< 160 m), indicating short-distance pollen dispersal, most likely due to the pollinator behaviour.