Seed dispersal and FST
Our results did not support the hypothesis that gravity-mediated seed
dispersal increases population differentiation compared to wind or
animal dispersal (Givnish, 2010) (Fig. 1d). This is in line with
previous findings suggesting that the genetic structure of nuclear
markers is largely driven by pollen flow (Petit et al., 2005; Sork,
Nason, Campbell, & Fernandez, 1999; Skogen et al., 2019), and that the
effect of seed dispersal is only detectable in the population genetic
structure of chloroplast genes (Duminil et al., 2007). However, we note
that gravity dispersal resulted in highly variable FSTvalues, potentially due to unrecorded secondary seed vectors.
FST values for animal dispersal were also highly
variable, which suggests that different animals could have different
effects on population differentiation. Thus overall, as with vertebrate
pollination, we suspect that more fine-scaled classifications of
dispersers may improve our understanding of their effects on plant
population genetic structure. Testing this idea, however, requires more
detailed data on animal dispersal modes, which can be difficult to
characterize. For example, in our study many species have a mix of seed
dispersers, including small to large mammals and birds (like most
Arecaceae, Fabaceae, Fagaceae, Myrtaceae, Sapotaceae, among others),
making it difficult to assign plants to a disperser-specific taxonomic
affiliation or foraging behavioral trait.