A test of the riverine barrier hypothesis in the largest subtropical river basin in the Neotropics

Abstract

The riverine barrier hypothesis proposes that large rivers represent geographical barriers to gene flow for terrestrial organisms, leading to population differentiation and ultimately allopatric speciation. Here we assess for the first time if the subtropical Paraná–Paraguay River system in the Del Plata basin, second in size among South American drainages, acts as a barrier to gene flow for birds. We analysed the degree of mitochondrial and nuclear genomic differentiation in seven species with known subspecies divided by the Paraná–Paraguay River axis. Only one species showed genetic differentiation concordant with the current river channel, but another five species have an east/west genetic split broadly coincident with the Paraná River's dynamic palaeochannel, suggesting this fluvial axis has had a past role in shaping present‐day genetic structure. Moreover, dating analyses show that these splits have been asynchronous, with species responding differently to the riverine barrier. Comparisons informed by the geological history of the Paraná River and its influence on the ecological and climatic differences among ecoregions in the study area further bolster the finding that responses to this geographical barrier have been species‐specific.

Pleistocene climatic oscillations associated with landscape heterogeneity of the South American dry diagonal explains the phylogeographic structure of the narrow‐billed woodcreeper (Lepidocolaptes angustirostris, Dendrocolaptidae)

“…2), suggesting that this region may harbor a differentiated genetic group within this lineage. A recent local study showed that L. angustirostris from the Province of Buenos Aires represent a different genetic population compared to other individuals from the Chaco (Kopuchian et al ). In this study, the authors attribute the Paraná‐Paraguay River palaeochannel and the limit between the Espinal–Chaco ecoregions as a potential barriers to gene flow between these two populations.…”

Genetic variation in neotropical butterflies is associated with sampling scale, species distributions, and historical forest dynamics

“…Butterflies in the NWA database were collected almost exclusively in montane forests located on the east slope of the Southern Central Andes in western Argentina. On the other hand, sampling covered a more heterogeneous landscape for the NEA library (Figure 1), with collection taking place across different ecoregions and physical barriers from eastern Argentina such as the Paraná-Paraguay River axis, the largest subtropical fluvial system in South America (Kopuchian et al, 2020). This, together with the fact that intraspecific variation was only weakly associated with geographic distances in NEA (Lavinia et al, 2017a), suggests that not only larger geographic distances but also the sampling of ecologically and climatically distinct habitats, alone or in combination with other evolutionary drivers, could explain the higher intraspecific variation found in the NEA data set (Gaytán et al, 2020;Kopuchian et al, 2020;Lavinia et al, 2017a).…”

Editorial 2021

“…A From the Cover manuscript by Kopuchian et al. (2020) took aim at testing whether the riverine barrier hypothesis could explain population differentiation of seven bird species in the subtropical Parana–Paraguay River basin. Using mitochondrial and nuclear data, the authors showed that, in this case, the river does not serve as a geographic barrier to gene flow for the majority of species.…”