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

Wilson J.E.M Costa,José Leonardo O Mattos,Pedro F Amorim

doi:10.3897/zse.94.29718

Abstract

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 Carnaúba de Dentro River drainage and adjacent drainages of the middle section of the São Francisco River basin, northeastern Brazil. The present study is primarily directed to the taxonomy of theH.fulminantisspecies 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.fulminantisandH.splendissimusCosta,sp. n.The new species is distinguished from other congeners of theH.fulminantiscomplex 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 8thand 9thvertebrae in males. Most recent field inventories indicated possible local extinction of populations ofH.fulminantisandH.splendissimusin the studied area, but additional field studies should be made in other parts of the upper Carnaíba de Dentro River basin to evaluate the current conservation status of these species.

Highlights

In the last three decades, field studies of cynolebiine killifishes in temporary pools of the Caatinga, a semi-arid phytogeographical province of northeastern Brazil, have continuously revealed spectacular species diversity (e.g., Costa 2001, 2007, 2014; Costa et al 2012, 2018a)
Hypsolebias splendissimus is presently known from a single locality just 8 km west from the geographical area inhabited by H. fulminantis (Fig. 4)
Their distribution areas are situated in neighbouring sub-drainages of the upper section of the Carnaíba de Dentro River drainage, at slightly different altitudes, about 505 m asl at the type locality of H. splendissimus and between 525 and 555 m asl at the localities from where H. fulminantis has been recorded

Summary

Introduction

In the last three decades, field studies of cynolebiine killifishes in temporary pools of the Caatinga, a semi-arid phytogeographical province of northeastern Brazil, have continuously revealed spectacular species diversity (e.g., Costa 2001, 2007, 2014; Costa et al 2012, 2018a). Over 50 valid species of the two killifish genera occurring in the Caatinga, Cynolebias Steindachner, 1876 and Hypsolebias Costa, 2006, are endemic to the main river basins of the region, with a greater concentration of species in the São Francisco River basin (e.g., Costa et al 2018b). In spite of the great morphological diversity exhibited by different endemic lineages of seasonal killifishes, several cryptic species have been recently recognised in the Caatinga using molecular species delimitation analyses.

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Results

Conclusion