Pattern of differentiation in the annual killifish genus Austrolebias (Cyprinodontiformes: Rivulidae) from a biosphere reserve site in South America: a multidisciplinary approach

Abstract

The annual killifish genus Austrolebias includes approximately 38 species distributed throughout the Paraná-Plata basin and Patos-Merín system. Within the Austrolebias adloffi species complex, the Uruguayan populations of Austrolebias charrua were considered as an intergradation between A. adloffi and Austrolebias viarius populations. Austrolebias charrua presents an intermediate phenotype between both taxa and high levels of morphological and chromatic variability. In the present study, we incorporate different methodological approaches (molecular, morphology, and gamete ultrastructure) to elucidate the pattern of differentiation among the parapatric taxa (A. charrua, Austrolebias reicherti, A. viarius) distributed in a Biosphere Reserve Site. Analyses of cytochrome b sequences show high values of DNA polymorphism, in particular for A. charrua. This is in accordance with both morphological and gametic variation. Using a statistical parsimony network based on these sequences and analysis of morphological data, past fragmentation and range expansion involving perhaps secondary contact between A. charrua and A. reicherti could be proposed. Coloration pattern and morphometric analyses showed an unexpected higher similarity between the most distantly-related taxa, A. viarius and A. charrua. This could be the result of retention of ancestral polymorphisms, especially in A. charrua populations from ponds of higher elevation, or to directional selection acting in similar ecological environments. Because these annual killifish species are considered endangered, our work reinforces the high priority need to include them in a conservation programme.

A new species of Austrolebias Costa (Cyprinodontiformes: Rivulidae) from northeastern Uruguay, with comments on distribution patterns

“…Distribution patterns are strongly associated with river basins or drainage areas and, in general, sister species occupy allopatric adjacent areas. One exception is the parapatric sister species A. charrua Costa & Cheffe and A. reicherti (Loureiro & García) García et al, 2009). Another such case was reported by for A. arachan Loureiro, Azpelicueta & García and A. vazferreirai (Berkekamp, Etzel, Reichert & Salvia), which occupy upstream regions of the río Negro drainage (río Uruguay basin) and an upstream region of the río Tacuarí drainage (Patos-Merín system).…”

Patterns of morphological variation among populations of the widespread annual killifish Nothobranchius orthonotus are independent of genetic divergence and biogeography

“…, ), is comparable to 3 Mya in the A. adloffi (Ahl, 1922) complex (García et al. ) or 7–13 Mya in the A. bellottii (Steindacher, 1881) complex (García et al. ).…”

“…Even the diagnostic traits being used in Austrolebias , as relative pre‐dorsal and preanal lengths, were shown to profoundly overlap among designed species (García et al. , ). The age of N. orthonotus as the time of its separation from the N. furzeri/N.…”

“…), South American Austrolebias (García et al. ) or Caribbean Rivulus Poey, 1860 (Ponce de León et al. ).…”

Contrasting morphology with population genetics approach: An insight to revision of the Neotropical annual fish “Austrolebias robustus” species group based on a taxonomic integrative framework

“…Lindenmayer, ). Population genetics and morphological analyses have demonstrated their usefulness to define managements units (MU) and evolutionary significant units, ESU (sensu Moritz, ), in multitude of taxa, and in particular in annual killifish genus Austrolebias (García G. & Ríos N., ; García et al., , ). The delineation of species boundaries based on multiple and complementary lines of evidence such as phylogeography, population genetics, morphology, ecology and biogeography among other possible data in an “integrative taxonomy” framework (Dayrat, ) context has gained relevance in the evaluation of biodiversity and in conservation strategies purposes.…”