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Phylogeographic analyses and taxonomic inconsistencies of the Neotropical annual fish Austrolebias minuano, Austrolebias charrua and Austrolebias pongondo (Cyprinodontiformes: Rivulidae) Murilo de Oliveira Fernandes Antonio Sergio Varela Junior

& &

Crislaine Barbosa & Daiana Kaster Garcez & Matheus Vieira Volcan & Lizandra Jaqueline Robe

Received: 28 October 2019 / Accepted: 3 November 2020 # Springer Nature B.V. 2020

Abstract A significant portion of the threatened ichthyofauna is composed by annual fish, whose gene flow is commonly affected by large water bodies. Austrolebias minuano is an endangered species that lives in temporary wetlands of the Patos-Mirim Lagoon System, in Brazil, inhabiting both margins of the Patos Lagoon. This species has previously been target of taxonomic split, leading to the description of A. pongondo, and there are doubts about its distinction in relation to A. charrua. The objective of this study is to understand the evolutionary patterns and processes associated with the geographic distribution of A. minuano, A. charrua and A. pongondo, while assessing their taxonomic status. For this, specimens were collected along the distribution range of the three species, and sequences of the mitochondrial cyt b and CO1 and of the

nuclear ENC1 gene were characterized. Phylogenetic and phylogeographic approaches showed subdivision of the dataset in four lineages: one clustering the type population of A. minuano with A. charrua, two presenting populations previously assigned to A. minuano that inhabit the Eastern margin of the Patos Lagoon and one corresponding to A. pongondo. Patterns of migration and genetic divergences support the assignment of each of these lineages as independent evolutionary units. In the chronophylogenetic reconstructions, the two lineages inhabiting the Western margin of the Patos Lagoon constituted the first to branch out whereas the eastern lineages diverged more recently. These divergences seem to have occurred before the Pleistocene LagoonBarrier Depositional System related to the paleogeographic evolution of the South American Coastal Plain.

Murilo de Oliveira Fernandes and Crislaine Barbosa contributed equally to this work.

Keywords Allopatric speciation . Genetics of conservation . Killifish . Patos Lagoon

M. de Oliveira Fernandes : C. Barbosa : D. K. Garcez : A. S. Varela Junior : L. J. Robe (*) Programa de Pós-Graduação em Biologia de Ambientes Aquáticos Continentais (PPGBAC), Universidade Federal do Rio Grande FURG, Rio Grande, Rio Grande do Sul, Brazil e-mail: [email protected] M. V. Volcan Laboratório de Ictiologia, Instituto Pró-Pampa, Rua Uruguai, Pelotas, Rio Grande do Sul 1242, Brazil L. J. Robe Departamento de Ecologia e Evolução (DEE), Centro de Ciências Naturais e Exatas (CCNE), Universidade Federal de Santa Maria – UFSM, Santa Maria, Rio Grande do Sul, Brazil

Introduction The barrier effect of rivers and large water bodies has long been hypothesized as a major driver of differentiation among populations, especially in the Neotropics that har