Fine scale spatial genetic structure in Pouteria reticulata (Engl.) Eyma (Sapotaceae), a dioecious, vertebrate dispersed tropical rain forest tree species

Abstract

Dioecious tropical tree species often have small flowers and fleshy fruits indicative of small-insect pollination and vertebrate seed dispersal. We hypothesize that seed mediated gene flow should be exceed pollen-mediated gene flow in such species, leading to weak patterns of fine scale spatial genetic structure (SGS). In the present study, we characterize novel microsatellite DNA markers and test for SGS in sapling (N=100) and adult trees (N=99) of the dioecious canopy tree Pouteria reticulata (Sapotaceae) in a 50 ha forest dynamics plot on Barro Colorado Island (BCI), Panama. The five genetic markers contained between five and 15 alleles per locus, totaling 51 alleles in the sample population. Significant SGS at local spatial scales (<100m) was detected in the sapling (dbh≈1cm) and adult (dbh≥20cm) size classes, but was stronger in the former (sapling Sp=0.010±0.004, adult Sp=0.006±0.002), suggesting demographic thinning. The degree of SGS was lower than the value expected for non-vertebrate dispersed tropical trees (Sp=0.029), but similar to the average value for vertebrate dispersed tropical trees (Sp=0.009) affirming the dispersal potential of vertebrate dispersed tropical trees in faunally intact forests.