Estudo taxonômico do gênero Hypostomus Lacépède, 1803 (Siluriformes: Loricariidae) na Região Hidrográfica Atlântico Nordeste Ocidental, Brasil

Abstract

This study investigates the diversity of the genus Hypostomus in the Região Hidrográfica Atlântico Nordeste Ocidental (RHANO), encompassing 11 hydrographic systems in Maranhão and northeastern Pará, Brazil. In Chapter 1, morphometric analyses of specimens from RHANO identified five morphotypes: Hypostomus krikati, from the Mearim and Turiaçu basins; Hypostomus cf. krikati, from the Munim and Itapecuru river basins; Hypostomus sp. “São Luís”, from São Luís Island; Hypostomus sp. “Turiaçu”, from the Imbaúba River (sympatric with H. krikati); and Hypostomus longiradiatus, described from specimens of the Guamá basin. Principal Component Analysis (PCA) and hierarchical clustering revealed distinct patterns of morphological variability, with Hypostomus sp. “São Luís” showing the greatest dispersion and H. longiradiatus standing out due to its distinct morphometric characteristics. Hypostomus krikati and H. cf. krikati exhibited close morphometric similarity, while H. sp. “Turiaçu” occupied an intermediate position. Ratios of body measurements, such as head length to standard length (HL/SL), demonstrated high reliability in species differentiation, with 95% support. Linear Discriminant Analysis (LDA) confirmed these patterns, clearly distinguishing H. longiradiatus and H. sp. “São Luís” as separate entities. Meanwhile, Hypostomus krikati, Hypostomus cf. krikati, and Hypostomus sp. “Turiaçu” exhibited greater overlap, though with some minor differences. In Chapter 2, Hypostomus krikati was formally described. In Chapter 3, Hypostomus longiradiatus was redescribed, with a neotype proposed due to the loss of the type series.