Amazonian birds in more dynamic habitats have less population genetic structure and higher gene flow

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 habitatspecific diversification dynamics over evolutionary time scales.

Habitat specialization predicts demographic response and vulnerability of floodplain birds in Amazonia

“…Therefore, our results support the hypothesis that the avifauna associated with seasonally flooded environments in Amazonia has a history marked by constant changes in habitat availability and connectivity, tightly linked to climatic changes during the quaternary (Barbosa et al., 2021; Johnson et al., 2023; Luna et al., 2022; Sawakuchi et al., 2022; Thom et al., 2020). However, the way species occupy distinct floodplain environments deeply affected their responses to landscape changes.…”

“…Also, island specialists have comparatively lower genetic diversity, and thus increased risk of extinction due to range fragmentation (Figure 4). The dynamic formation of islands across multiple rivers during the recent history of Amazonia has promoted continuous gene flow and supported the persistence of these taxa with little population structure and low genetic diversity, across great extents of the Amazon Basin (Johnson et al., 2023). However, most of the distribution of several island specialists, particularly Dynamic Specialists, coincides with the Amazonian sub‐basins most threatened by dams, like the Ucayali, Marañon and Madeira (Figures S1–S5; Latrubesse et al., 2017, 2021).…”

“…Also, island specialists have comparatively lower genetic diversity, and thus increased risk of extinction due to range fragmentation (Figure 4). The dynamic formation of islands across multiple rivers during the recent history of Amazonia has promoted continuous gene flow and supported the persistence of these taxa with little population structure and low genetic diversity, across great extents of the Amazon Basin (Johnson et al, 2023).…”

“…Moreover, these fluctuations have likely affected the distribution of specific habitats in different ways, with a stronger impact on the more ephemeral and dynamic environments like river islands (Passos et al, 2020;Sawakuchi et al, 2022). Evidence from different studies seem to corroborate this hypothesis showing a more tumultuous evolutionary history in bird taxa associated with more dynamic floodplain environments (Barbosa et al, 2021;Choueri et al, 2017;Johnson et al, 2023;Luna et al, 2022;Sawakuchi et al, 2022;Thom et al, 2020Thom et al, , 2022. Nonetheless, a comprehensive classification of habitat specialization across the basin is still needed for a thorough understanding of the effect of distinct habitat associations in the responses of the endemic floodplain bird community to past landscape changes.…”

A shallow-scale phylogenomics approach reveals parallel patterns of diversification among sympatric populations of cryptic Neotropical aquatic beetles (Coleoptera: Noteridae)

“…The relationship between geography and patterns of organismal diversity has long been considered in the study of Neotropical biota (Rull, 2020), with investigations varying in focal spatial and temporal scales (e.g. Harvey et al, 2016; 2017; Toussaint and Gillet, 2018; Maestri and Duarte, 2020; Rull, 2020; Sánchez-Herrera et al, 2020; Johnson; et al, 2023). However, biogeographic hypotheses explaining the high levels of Neotropical biodiversity often focus on recent timescales (e.g.…”