Multilocus phylogeny, diagnosis and generic revision of the Guiana Shield endemic suckermouth armoured catfish tribe Lithoxini (Loricariidae: Hypostominae)

摘要

With & 450 species, Hypostominae is the most species-rich subfamily of suckermouth armoured catfishes (Loricariidae). Both morphological and molecular analyses of Hypostominae strongly support monophyly of ten distinctively small-bodied (& 9 cm standard length), highly depressed (maximal head depth & 7.2 times in standard length) species comprising two currently valid genera (Exastilithoxus and Lithoxus) that are restricted to fast-flowing, rocky-bottomed rivers and streams draining the Guiana Shield in northwestern South America. We describe the tribe Lithoxini for this clade and present a multilocus phylogeny for eight Lithoxini species, including type species of all nominal genera and subgenera. Based on morphological and molecular data, we resurrect and redescribe the previously synonymized subgenus Paralithoxus for a strongly supported clade of eight species that are restricted to rivers south and east of Venezuela and have seven to nine interdorsal plates and five rows of plates on the caudal peduncle. We also erect the new genus Avalithoxus for Lithoxus jantjae, a species that is narrowly endemic to the Ventuari River immediately upstream of Salto Tencua and is unique in Hypostominae for having only 12 branched caudal-fin rays. Lithoxus is restricted to Lithoxus lithoides from the Essequibo and Correntyne rivers in Guyana and Suriname. A redescription of Paralithoxus bovallii based on recently collected specimens and an identification key to all four genera are also provided. Geographical distributions of Lithoxini clades suggest that geological uplift and geodispersal via stream capture played important roles in promoting vicariance and allopatric speciation.