Review of the family Rivulidae (Cyprinodontiformes, Aplocheiloidei) and a molecular and morphological phylogeny of the annual fish genus Austrolebias Costa 1998

ABSTRACT The family Rivulidae is the fourth most diverse clade of Neotropical fishes. Together with some genera of the related African family Nothobranchiidae, many rivulids exhibit a characteristic annual life cycle, with diapausing eggs and delayed embryonic development, which allows them to survive in the challenging seasonal ponds that they inhabit. Rivulidae also includes two species known as the only the self-fertilizing vertebrates and some species with internal fertilization. The first goal of this article is to review the systematics of the family considering phylogenetic relationships and synapomorphies of subfamilial clades, thus unifying information that is dispersed throughout the literature. From this revision, it is clear that phylogenetic relationships within Rivulidae are poorly resolved, especially in one of the large clades that compose it, the subfamily Rivulinae, where conflicting hypotheses of relationships of non-annual and annual genera are evident. The second goal of this work is to present an updated phylogenetic hypothesis (based on mitochondrial, nuclear, and morphological information) for one of the most speciose genus of Rivulidae, Austrolebias. Our results confirm the monophyly of the genus and of some subgeneric clades already diagnosed, but propose new relationships among them and their species composition, particularly in the subgenus Acrolebias.

Molecular phylogeny and timing of diversification in South American Cynolebiini seasonal killifishes

The rich biological diversity of South America has motivated a series of studies associating evolution of endemic taxa with the dramatic geologic and climatic changes that occurred during the Cainozoic. The organism here studied is the killifish tribe Cynolebiini, a group of seasonal fishes uniquely inhabiting temporary pools formed during the rainy seasons. The Cynolebiini are found in open vegetation areas inserted in the main tropical and subtropical South American phytogeographical regions east of the Andes. Here, we present the first molecular phylogeny sampling all the eight genera of the Cynolebiini, using fragments of two mitochondrial and four nuclear genes for 35 species of Cynolebiini plus 19 species as outgroups. The dataset, 4448bp, was analysed under Bayesian and maximum likelihood approaches, providing a relatively well solved tree, which retrieves high support values for the Cynolebiini and most included clades. The resulting tree was used to estimate the time of divergence in included lineages using two cyprinodontiform fossils to calibrate the tree. We further investigated historical biogeography through the likelihood-based DEC model. Our estimates indicate that divergence between the clades comprising New World and Old World aplocheiloids occurred during the Eocene, about 50Mya, much more recent than the Gondwanan fragmentation scenario assumed in previous studies. This estimation is nearly synchronous to estimated splits involving other South American and African vertebrate clades, which have been explained by transoceanic dispersal through an ancient Atlantic island chain during the Palaeogene. We estimate that Cynolebiini split from its sister group Cynopoecilini in the Oligocene, about 25Mya and that Cynolebiini started to diversify giving origin to the present genera during the Miocene, about 20-14Mya. The Cynolebiini had an ancestral origin in the Atlantic Forest and probably were not present in the open vegetation formations of central and northeastern South America until the Middle Miocene, when expansion of dry open vegetation was favoured by cool temperatures and strike seasonality. Initial splitting between the genera Cynolebias and Simpsonichthys during the Miocene (about 14Mya) is attributed to the uplift of the Central Brazilian Plateau.