By animal, water, or wind: can dispersal mode predict genetic connectivity in riverine plant species?

Seed dispersal is crucial to gene flow among plant populations. Although the effects of geographic distance and barriers to gene flow are well studied in many systems, it is unclear how seed dispersal mediates gene flow in conjunction with interacting effects of geographic distance and barriers. To test whether distinct seed dispersal modes (i.e. hydrochory, anemochory, and zoochory) have a consistent effect on the level of genetic connectivity (i.e., gene flow) among populations of riverine plant species, we used unlinked single-nucleotide polymorphisms (SNPs) for eight co-distributed plant species sampled across the Rio Branco, a putative biogeographic barrier in the Amazon Basin. We found that animal-dispersed plant species exhibited higher levels of genetic diversity and lack of inbreeding as a result of the stronger genetic connectivity than plant species whose seeds are dispersed by water or wind. Interestingly, our results also indicated that the Rio Branco facilitates gene dispersal for all plant species analyzed, irrespective of their mode of dispersal. Our findings indicate that seed dispersal mode and riverscape features can greatly impact genetic structure, representing reliable predictors of genetic connectivity in riverine plant species. These results may help improve conservation and management policies in Amazonian riparian forests, where degradation and deforestation rates are high.

Methods
The dataset was generated by using a ddRADseq methodology.