Seed dispersal by animals: exact identification of source trees with endocarp DNA microsatellites

A long-standing challenge in studies of seed dispersal by animal frugivores has been the characterization of the spatial relationships between dispers ed seeds and the maternal plants, i.e. the seed shadow. The difficulties to track unambiguously the origin of frugivore-dispersed seeds in natural com munities has been considered an unavoidable limitation of the research fiel d and precluded a robust analysis of the direct consequences of zoochory. H ere we report that the multilocus genotype at simple sequence repeat (SSR; microsatellite) loci of the woody endocarp, a tissue of maternal origin, pr ovides an unequivocal genetic fingerprint of the source tree. By comparing the endocarp genotype against the complete set of genotypes of reproductive trees in the population, we could unambiguously identify the source tree f or 82.1% of the seeds collected in seed traps and hypothesize that the rema ining 17.9% of sampled seeds come from other populations. Identification of the source tree for Prunus mahaleb seeds dispersed by frugivores revealed a marked heterogeneity in the genetic composition of the seed rain in diffe rent microhabitats, with a range of 1-5 distinct maternal trees contributin g seeds to a particular landscape patch. Within-population dispersal distan ces ranged between 0 and 316 m, with up to 62% of the seeds delivered withi n 15 m of the source trees. Long distance dispersal events, detected by the exclusion of all reproductive trees in the population, accounted for up to 17.9% of the seeds sampled. Our results indicate strong distance limitatio n of seed delivery combined with infrequent long-distance dispersal events, extreme heterogeneity in the landscape pattern of genetic makeup, and a ma rked mosaic of multiple parentage for the seeds delivered to a particular p atch.