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.

No abstract

The genus Austrolebias (Cyprinodontiformes: Rivulidae) represents a specious group of taxa following annual life cycles in the neotropical ichthyofauna. They live in temporary ponds and each generation must be completed in a few months, depending on environmental stochasticity. Annual fish survive the dry season through diapausing eggs buried in the substrate of these ponds. A hypothesized bimodal hybrid zone between two taxa of the genus, A. charrua and A. reicherti from Dos Patos Merin lagoon system, was recently proposed based on genetics and morphological analyses. However, hundreds of additional nuclear molecular markers should be used to strongly support this hypothesized bimodal pattern. In the present paper, we conducted RNA-seq-based sequencing of the transcriptomes from pools of individuals of A. charrua, A. reicherti and their putative natural hybrids from the previously characterized hybrid zone. As a result, we identified a set of 111,725 SNP (single nucleotide polymorphism) markers, representing presumably fixed allelic differences among the two species. The present study provided the first panel of 106 SNP markers as a single diagnostic multiplex assay and validated their capacity to reconstruct the patterns of the hybrid zone between both taxa. These nuclear markers combined with Cytb gene and morphological analyses detected a population structure in which some groups among the hybrid swarms showed different level of introgression towards one or the other parental species according to their geographic distribution. High-quality transcriptomes and a large set of gene-linked SNPs should greatly facilitate functional and population genomics studies in the hybrid zone of these endangered species.

Based on National Collections records, this article presents the first report of eight freshwater fish species for Uruguay in the middle and lower Uruguay River basin, extending their current distribution: Cyanocharax alegretensis Malabarba and Weitzman, 2003; Leporinus lacustris Amaral Campos, 1945; Microglanis aff. eurystoma Malabarba and Mahler, 1998; Tatia boemia Koch and Reis, 1996; Lepthoplosternum pectorale (Boulenger, 1895); Crenicichla missioneira Lucena and Kullander, 1992; C. minuano Lucena and Kullander, 1992; Apistogramma borellii Regan, 1906. These species were previously recorded either for upper Uruguay River or Paraná River.

The objective of the present paper was to characterize the morphological and genetic patterns of variability in four taxa of the Austrolebias robustus species group distributed in two of the major southernmost river basins in South America. We compared results from the two approaches followed in this study to access hypotheses of species limits using an integrative taxonomic framework and patterns of population differentiation. Mitochondrial Cytb gene genealogy and networks analyses detected four major clades which do not fully correspond to currently known species of the A. robustus species group. Although the clade including A. robustus and A. nonoiuliensis received well support, the clade of A. cinereus also contains individuals of A. vazferreirai. BEAST analysis suggested that these taxa may have emerged from independent vicariant allopatric events. While high level of overlap was detected in all morphological analyses, in which species were distinguished only by small changes in body and head shape, the patterns of morphological variation detected among taxa were generally congruent with the different hypotheses of differentiation emerging from genetic population analyses. Based on all present results and following the principle of priority, we propose that A. vazferreirai is a junior synonym of A. cinereus. The subtle morphological discrimination among these taxa, representing local adaptations, reinforces the need to implement urgent actions in order to preserve the A. cinereus population, only reported since its description for the type locality in the PLPUB region. Our results are relevant and informative, supporting the implementation of biodiversity conservation programmes in these endangered endemic allopatric killifish populations, from the major southernmost unsampled areas of the Neotropical basins.

No abstract

No abstract