Two new seasonal killifishes of the Austrolebias adloffi group from the Lagoa dos Patos basin, southern Brazil (Cyprinodontiformes: Aplocheilidae)

Abstract

Morphological characters and phylogenetic trees generated by analyses of a segment of the mitochondrial gene cytochrome b support two new species from the Lagoa dos Patos basin, in southern Brazil. The phylogenetic analyses indicate that the two new species are each other’s respective closest relatives among species of A. adloffi group. The clade comprising the two new species is supported as being more closely related to A. adloffi than to A. nigrofasciatus that is endemic to the same area. Austrolebias pelotapes Costa & Cheffe n. sp. is distinguished from all other species of the A. adloffi group by having the urogenital papilla base attached by a thin membrane to the anterior margin of the anal fin in males; it is endemic to an area containing temporary pools and swamps associated to small streams tributaries to the northern margin of the São Gonçalo channel, just about 10 km from the area inhabited by A. nigrofasciatus. Austrolebias pongondo Costa & Cheffe n. sp., from temporary pools and swamps in the floodplains south of the São Gonçalo channel, and A. pelotapes are distinguished from all other species of the A. adloffi group by a combination of character states, including the presence of a transverse row of small spots on the middle portion of the dorsal fin in males, unpaired fins with a single row of light blue spots on their basal portion in males, a distinctive dark grey zone on the posterior portion of the dorsal and anal fins, and caudal peduncle in males predominantly dark brownish grey or dark grey to black, with narrow vertical light blue zones.