New species, Nematolebias catimbau
Species limits and DNA barcodes in Nematolebias, a genus of seasonal killifishes threatened with extinction from the Atlantic Forest of south-eastern Brazil, with description of a new species (Teleostei: Rivulidae)
Wilson J. E. M. Costa, Pedro F. Amorim and Giulia N. Aranha
Ichthyol. Explor. Freshwaters, Vol. 24, No. 3, pp. 225-236, 3 figs., 2 tabs., March 2014
Nematolebias, a genus of killifishes uniquely living in temporary pools of south-eastern Brazil, contains two nominal species, N. whitei, a popular aquarium fish, and N. papilliferus, both threatened with extinction and presently distinguishable by male colour patterns. Species limits previously established on the basis of morphological characters were tested using mt-DNA sequences comprising fragments of the mitochondrial genes cytochrome b and cytochrome c oxidase I, taken from 23 specimens representing six populations along the whole geographical distribution of the genus. The analysis supports the recognition of a third species, N. catimbau, new species, from the Saquarema lagoon basin, as an exclusive lineage sister to N. papilliferus, from the Maricá lagoon basin, and N. whitei, from the area encompassing the Araruama lagoon and lower São João river basins, as a basal lineage. The new species is distinguished from congeners by the colour pattern and the relative position of pelvic-fin base, besides 11 unique nucleotide substitutions. The distribution pattern derived from sister taxa inhabiting the Saquarema and Maricá basins is corroborated by a clade of the seasonal genus Notho lebias, suggesting a common biogeographical history for the two genera.
Possibly the greatest present challenge for taxonomists is to catalogue the poorly known species diversity of tropical areas under intense process of environmental degradation (Brook et al., 2006; Costa et al., 2012). For example, the Atlantic Forest of eastern Brazil, the second largest forest of South America and one of the richest biodiversity centres in the world (Myers et al., 2000), * concentrates a high number of species threatened with extinction (Tabarelli et al., 2005), many of them still poorly known. Aplocheiloid killifishes of the Neotropical family Rivulidae are particularly diversified in the Atlantic Forest, where they are represented by eight endemic genera and more than 40 endemic species (Costa, 2008, 2009, 2010). Most killifishes endemic to this biome are seasonal organisms, uniquely living in shallow temporary pools formed during the rainy seasons (Myers, 1942; Costa, 2002a, 2009), besides being restricted to small geographical areas and standing among the most endangered vertebrates of South America (Costa, 2002b, 2012).
Nematolebias Costa, 1998 is a genus of seasonal killifishes endemic to the Atlantic Forest of the coastal plains of Rio de Janeiro state, southeastern Brazil (Costa, 2002a). This region formerly comprised dense rain forests and broad swampy areas (Wied-Neuwied, 1820), but since the beginning of the 20th century it has been mainly occupied by open vegetation formations used as pasture for cattle, and more recently by a quick expansion of coastal urban centres. As a consequence of habitat loss, endemic killifish species are severely threatened with extinction (Costa, 2009, 2012).
Nematolebias has been considered the sister group to a speciose clade containing all other taxa of the tribe Cynolebiasini, easily diagnosed by the presence of hypertrophied papillae on the pectoral fin in males and the presence of a broad sub-distal orange stripe with overlapped golden lines on the anal fin in males (Costa, 2002a, 2006, 2010). Costa (2002a) revised Nematolebias, recognising two cryptic species (sensu Bickford et al., 2007), N. whitei (Myers, 1942), a popular aquarium fish and known from some populations in a long geographical area between the São João river basin and the Araruama lagoon basin, and N. papilliferus Costa, 2002, from two populations from the Maricá lagoon basin, and a single population from the Saquarema lagoon basin (Fig. 1). Both species were distinguished by characters of male colour patterns, including the presence of golden lines on the dorsal fin which is present in N. papilliferus but absent in N. whitei. More recent field work has revealed that the populations of N. papilliferus from the Maricá basin, including the type locality of the species, exhibit colour pattern slightly distinct from populations inhabiting the Saquarema basin, making clear the necessity of adding more data to test species limits. Thus, the objective of the present study is to combine revised data of morphology at the population level with mitochondrial DNA sequences obtained from six populations representing the whole geographic range of the genus.