New species, Nematolebias catimbau
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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
Abstract
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.
Introduction
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....
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