Abstract
We assessed population structure and the spatio‐temporal pattern of diversification in the Glossy Antshrike Sakesphorus luctuosus (Aves, Thamnophilidae) to understand the processes shaping the evolutionary history of Amazonian floodplains and address unresolved taxonomic controversies surrounding its species limits. By targeting ultraconserved elements (UCEs) from 32 specimens of S. luctuosus, we identified independent lineages and estimated their differentiation, divergence times, and migration rates. We also estimated current and past demographic histories for each recovered lineage. We found evidence confirming that S. luctuosus consists of a single species, comprising at least four populations, with some highly admixed individuals and overall similar levels of migration between populations. We confirmed the differentiation of the Araguaia River basin population (S. l. araguayae) and gathered circumstantial evidence indicating that the taxon S. hagmanni may represent a highly introgressed population between three distinct phylogroups of S. luctuosus. Divergences between populations occurred during the last 1.2 mya. Signs of population expansions were detected for populations attributed to subspecies S. l. luctuosus, but not for the S. l. araguayae population. Our results support that S. luctuosus has had a complex population history, resulting from a high dependence on southeastern “clear water” seasonally flooded habitats and their availability through time. Spatial and demographic expansions toward the western “white water” flooded forests might be related to recent changes in connectivity and availability of these habitats. Our study reinforces the view that isolation due to absence of suitable habitat has been an important driver of population differentiation within Amazonian flooded forests, but also that differences between várzeas (“white water” floodplains, mostly in southwestern Amazonia) and igapós (“clear water” floodplains, especially located in the east) should be further explored as drivers of micro‐evolution for terrestrial species.
Highlights
Most swampy and flooded forests are found in the tropics, in the Congo River Basin and northern/northeastern South America, with the most widespread area of inundated forests occurring along rivers within the Amazon River Basin (Lehner & Döll, 2004)
Our ultimate goal is to contribute to a better understanding of the processes shaping diversity within Amazonian várzeas and igapós and to a more reliable assessment of current biotic diversity associated to Amazonian seasonally flooded habitats, which are under imminent threat due to the construction of hydropower dams along the main Amazonian tributaries
Genomic DNA was extracted from tissues of 32 specimens of S. luctuosus from across its known range, including 5 araguayae representatives, and a single specimen collected on a river island located ca. 18 km from the type locality of hagmanni on the south bank of the Amazon River (Figure 1a, locality 25; Table S1.1)
Summary
Most swampy and flooded forests are found in the tropics, in the Congo River Basin and northern/northeastern South America, with the most widespread area of inundated forests occurring along rivers within the Amazon River Basin (Lehner & Döll, 2004). Periods of fluvial aggradation resulting in sediment accumulation would have alternated with incisional stages, allowing the cyclic expansion and retraction of inundated habitats, respectively, and the opposite pattern for upland forests (Pupim et al, 2019) Given this instability, species-specific responses to such changes, often mediated by ecological traits, are expected, which do seem to have occurred during the diversification of Amazonian birds (Bicudo et al, 2019; Choueri et al, 2017; Silva et al, 2019; Thom et al, 2018, 2020). Our ultimate goal is to contribute to a better understanding of the processes shaping diversity within Amazonian várzeas and igapós and to a more reliable assessment of current biotic diversity associated to Amazonian seasonally flooded habitats, which are under imminent threat due to the construction of hydropower dams along the main Amazonian tributaries
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