Diversity and conservation of seasonal killifishes of the Hypsolebias fulminantis complex from a Caatinga semiarid upland plateau, Sao Francisco River basin, northeastern Brazil (Cyprinodontiformes, Aplocheilidae)

A high concentration of endemic species of seasonal killifishes has been recorded for a small area encompassing the highland plateaus associated with the upper section of the Carnauba de Dentro River drainage and adjacent drainages of the middle section of the Sao Francisco River basin, northeastern Brazil. The present study is primarily directed to the taxonomy of the H. fulminantis species complex in this region, and describes habitat decline and extirpation of natural killifish populations recorded in field studies between 1993 and 2017. Both morphological characters and molecular species delimitation methods using single-locus models (GMYC and bPTP) support recognition of two closely related endemic species, H. fulminantis and H. splendissimus Costa, sp. n. The new species is distinguished from other congeners of the H. fulminantis complex by having a red pectoral fin in males, well-developed filamentous rays on the tips of the dorsal and anal fins in adult males, and the second proximal radial of the dorsal fin between the neural spines of the 8th and 9th vertebrae in males. Most recent field inventories indicated possible local extinction of populations of H. fulminantis and H. splendissimus in the studied area, but additional field studies should be made in other parts of the upper Carnaiba de Dentro River basin to evaluate the current conservation status of these species.