Abstract
Understanding the factors that govern variation in genetic structure
across species is key to the study of speciation and population genetics.
Genetic structure has been linked to several aspects of life history, such
as foraging strategy, habitat association, migration distance, and
dispersal ability, all of which might influence dispersal and gene flow.
Comparative studies of population genetic data from species with differing
life histories provide opportunities to tease apart the role of dispersal
in shaping gene flow and population genetic structure. Here, we examine
population genetic data from sets of bird species specialized on a series
of Amazonian habitat types hypothesized to filter for species with
dramatically different dispersal abilities: stable upland forest, dynamic
floodplain forest, and highly dynamic riverine islands. Using genome-wide
markers, we show that habitat type has a significant effect on population
genetic structure, with species in upland forest, floodplain forest, and
riverine islands exhibiting progressively lower levels of structure.
Although morphological traits used as proxies for individual-level
dispersal ability did not explain this pattern, population genetic
measures of gene flow are elevated in species from more dynamic riverine
habitats. Our results suggest that the habitat in which a species occurs
drives the degree of population genetic structuring via its impact on
long-term fluctuations in levels of gene flow, with species in highly
dynamic habitats having particularly elevated gene flow. These differences
in genetic variation across taxa specialized in distinct habitats may lead
to disparate responses to environmental change or habitat-specific
diversification dynamics over evolutionary time scales.