Phylogeography of the critically endangered neotropical annual fish, Austrolebias wolterstorffi (Cyprinodontiformes: Aplocheilidae): genetic and morphometric evidence of a new species complex

Phylogenetic structure of Neotropical annual fish of the genusCynopoecilus(Cyprinodontiformes: Rivulidae), with an assessment of taxonomic implications

“…In this sense, populations previously assigned to C. fulgens that inhabit areas in which these recent geomorphological events have occurred confirmed especially prone to present cryptic diversity. Nevertheless, in contrast to what was recently shown for A. wolterstorffi , a species that inhabits the same drainage system (Garcez et al., 2018), the phylogenetic tree recovered here for Cynopoecilus does not suggests a north‐to‐south colonization route. In fact, the early offshoot of the genus, that is, C. notabilis , does not occur in one of the Northern most distribution areas of the genus.…”

“…This major phylogenetic structure encountered in Cynopoecilus supports the hypothesis that large water bodies can act as effective barriers to gene flow among populations/species of annual fish, leading to allopatric fragmentation (Bartáková et al., 2013, 2015; García et al., 2012, 2015). This pattern is also consistent with that recently demonstrated for A. wolterstorffi , at least in regard to the Patos‐Mirim Lagoon System (Garcez et al., 2018). In a finer scale, it was also possible to evidence vicariance as a result of drainage changes related to geomorphological events that affected the Southern Brazil coastal plain during Quaternary (Loureiro & García, 2006; Villwock & Tomazelli, 2007).…”

“…For SJN4, there seems to have occurred an admixture or secondary contact, as that encountered between A. charrua Costa & Cheffe, 2001 and A. reicherti Loureiro & García, 2004 (García et al., 2009) and between two clusters of A. wolterstorffi (Garcez et al., 2018). In both cases, the lowlands of the Patos‐Mirim drainage system near the Atlantic coast were considered as potential contact areas (Garcez et al., 2018; García et al., 2009, 2015), in accordance with the scenario depicted here. Nevertheless, the fact that there are populations of C. melanotaenia inhabiting both margins of the Patos Lagoon suggests the occurrence of dispersal events across the Lagoon, which sounds quite surprising.…”

“…Although vicariance seems to have accomplished the main diversification mechanism of Rivulidae (Bartáková et al., 2015; Garcez et al., 2018; García et al., 2009, 2012, 2015; Jowers, Cohen, & Downie, 2008; Loureiro & de Sá, 2015; Ponce de León et al., 2014), the distribution of the provisional species of Cynopoecilus also suggests the occurrence of isolated and recent dispersal events. This can be evidenced by the signals of population admixture detected in the locality 4 of São José do Norte (SJN4), which encompasses individuals clustered with C. melanotaenia and with Cynopoecilus sp., and by the single genetically homogeneous population of C. melanotaenia (initially assigned to C. fulgens ) sampled at the East margin of the Lagoon (locality 3 of São José do Norte—SJN3).…”

“…Allopatric speciation in annual fish may have been further enhanced by large water bodies and even terrestrial areas acting as effective barriers to gene flow (Bartáková, Reichard, Blažek, Polačik, & Bryja, 2015; Bartáková et al., 2013) and interrupting gene flow even between recently diverged and geographically close populations (Barbosa, Garcez, Volcan, & Robe, 2020). In this way, it is not rare to find high levels of cryptic diversity within different species of annual fish, which may actually comprise species complexes (Garcez et al., 2018; García, Gutiérrez, Ríos, & de Sá, 2015; García et al., 2019). Unfortunately, the fact that annual fish usually encompass small and isolated populations also turns these species one of the most endangered taxa.…”