Effects of habitat fragmentation on parental correlations in the seed rain of a bird-dispersed species

Seed dispersal plays a crucial role in natural forest regeneration. Changes in the seed rain due to anthropogenic habitat alteration can influence seedling recruitment patterns and affect the evolutionary dynamics of populations. Using a combined endocarp-embryo microsatellite assay of naturally dispersed seeds, we concomitantly quantify the contribution of contemporary pollen and seed dispersal to the genetic structure of the seed rain of the shrub species Pistacia lentiscus L. The study was conducted in two consecutive seasons at four forest fragments embedded in contrasting (connected vs. isolated) landscapes. Interseasonal variation in the parental genetic structure of the seed rain was assessed through analysis of molecular variance, and paternal and maternal correlations and effective parental numbers were computed for different fragments and microhabitats (within fragments) using genetic kinship analysis. Temporal variation in the genetic structure of the dispersed seeds was higher for maternal gametes, reflecting a more temporally variable contribution of individual mother plants to the seed rain, as a potential consequence of masting and/or natural heterogeneity. Higher effective numbers of fathers than mothers were consistently observed in all studied forest fragments and microhabitats, the difference being more pronounced for connected than for isolated fragments. The effective number of mothers, directly influenced by disperser birds’ behavior, was apparently insensitive to fragmentation. Despite potentially high mobility of pollen by wind and seeds by birds, habitat fragmentation could influence the parental structure of dispersed seeds, with potential consequences for the genetic structure of the adult generation.