Taxonomia e padrões de distribuição de cascudinhos do gênero Hypoptopoma do grupo gulare (Siluriformes, Loricariidae) na Bacia Amazônica

Abstract

The genus Hypoptopoma comprises eight valid species, being a group of the subfamily Hypoptopomatinae (Loricariidae), which is widely distributed in South America, from Venezuela to Argentina. Within the genus, the Hypoptopoma gulare group is composed by species with long pectoral spine and only two rows of complete abdominal plates, which are: H. gulare, H. joberti and H. steindachneri from Amazon, and H. inexspectatum from Paraná-Paraguay. Nevertheless, the specifics and geographical boundaries of these species remain unclear. Thus, this work aimed to revise the taxonomic composition of this group in the Amazon basin. Morphometric analyses (using measurements and counts) of the preserved specimens from ichthyological collections identified five morphotypes. One was associated to the nominal species, H. gulare, and the others were considered undescribed: Hypoptopoma sp. n. “Urucu”, Hypoptopoma sp. n. “Trombetas”, Hypoptopoma sp. n. “anão” e H. sp. n. “Marajó. In this revision it is suggested that H. steindachneri and H. joberti are junior synonymies of H. gulare. The geographic distribution of this species is expanded from Marañon/Ucayali to the Madeira Basin. The pattern of morphological variation found in H. gulare suggests the existence of a morphological (or phenotypical) cline, with a gradient of variation from upstream to downstream.