Multiple simultaneous speciation in killifishes of the Cynolebias adloffi species complex (Cyprinodontiformes, Rivulidae) from phylogeography and chromosome data

Abstract

The annual killifishes of the genus Cynolebias Steindachner, 1876, include one of the well-supported clades composed of the Cynolebias adloffi species complex of the Ban˜ados del Este Biosphere Reserve Site, from the Atlantic coastal wetlands in Uruguay. One member of this clade, Cynolebias charrua, has been considered as an intergradation complex of populations between C. adloffi and C. viarius by showing high levels of morphological variability. Systematic affinities between both taxa have been historically discussed. In the present study, a phylogeographic approach based on mitochondrial cytochrome b haplotype analysis and chromosome data are presented. According to the present data a scenario of a multiple simultaneous speciation process and perhaps reticulation events is possible in the C. adloffi species complex, followed by divergence associated with Quaternary marine transgressions in this region. This hypothetic scenario could explain the remarkable genetic diversity and the lack of phylogenetic resolution among clades in C. charrua, as well as the disconcordance in the phylogenetic relationships among Cynolebias from different data sets. Several parameters of DNA polymorphism and chromosome data have also suggested that populations of C. charrua from southern Laguna Merin, in eastern Uruguay and southern Brazil, could represent a relictual group from a widespread ancestral population. Chromosome rearrangements like pericentric inversions in isolated populations could have triggered cladogenetic events from this highly polymorphic population. Present analysis suggests that the metapopulation could represent the management units in these endangered killifishes and that the populations of C. charrua from the Laguna Merin basin could be included in a high-priority conservation programme.

Next-generation sequencing detects repetitive elements expansion in giant genomes of annual killifish genus Austrolebias (Cyprinodontiformes, Rivulidae)

“…Austrolebias species appear to be conventional diploids in all other respects and there is no reason to believe they arise from polyploid ancestors. The aforementioned drastic nuclear DNA increasing events would be associated with the great genome instability previously found in Austrolebias (García 2006) and could be explaining the high morphological diversity described in species of the genus (Loureiro and de Sá 1998). Previous phylogenetic analyses based on three mitochondrial genes (García et al 2002) proposed that the genus suffered sudden cladogenetic events since the Quaternary.…”

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

“…Monophyly of the genus is supported by molecular (García et al, 2000;García, 2006) and morphological analysis (Costa, 2006). According to Costa (2006), synapomorphies that support Austrolebias monophyly comprise head scale patterns, pigmentation around the eyes, bony structures of the lower jaw and the gill arches, morphology of the unpaired fins, and genital morphology.…”

“…According to the most recent revision (Costa, 2006), the genus includes three basal species and five species groups. Despite the fact that these groups were roughly supported by molecular analyses (García et al, 2000;García, 2006), phylogenetic relationships among and within clades are still the subject of debate.…”

“…According to Costa (2006), synapomorphies that support Austrolebias monophyly comprise head scale patterns, pigmentation around the eyes, bony structures of the lower jaw and the gill arches, morphology of the unpaired fins, and genital morphology. Phylogenetic relationships within the genus are considered controversial because morphological and molecular analyses are contradictory (Costa, 1998(Costa, , 2002(Costa, , 2006García et al, 2000;García, 2006;Loureiro, 2004). According to the most recent revision (Costa, 2006), the genus includes three basal species and five species groups.…”

Discovery of endangered annual killifish Austrolebias cheradophilus (Aplocheiloidei: Rivulidae) in Brazil, with comments on habitat, population structure and conservation status

“…Morphological (Costa, 2006) and molecular analysis (García, 2006) support the monophyly of the genus and its highest diversity occurs in southern Brazil and Uruguay, especially in drainages of Patos-Mirim hydrographic system (Costa, 2010;Loureiro et al, 2008). The genus was recently phylogenetically redefined, including the species previously referred to Megalebias (Costa, 2006), and divided into sub-genera (Costa, 2008).…”