Enigma dos riachos mineiros: Psalidodon rivularis (Acestrorhamphidae: Acestrorhamphinae), um modelo no estudo de espécies crípticas

Abstract

When compared to other river basins, the number of species of the genus Psalidodon in the Upper São Francisco River basin is considerably low, with only three species formally described: Psalidodon fasciatus, Psalidodon rivularis, and Psalidodon pessalii. Two problems justify this low number. The first is due to the genus Psalidodon being reconsidered valid only in 2020 after years of disuse, with several species, mainly from Astyanax and Hyphessobrycon, being transferred to Psalidodon. The second is because P. fasciatus and P. rivularis correspond to species complexes. In the case of P. rivularis, its formalization as a species complex is recent and is supported by cytogenetic, molecular, and morphological data. In this work, we present two chapters. The first uses an integrated approach of morphological, cytogenetic, and genomic data to clarify how many species exist in the P. rivularis complex in the Upper São Francisco River. In the second, we present a new protocol for assembly and comparison in silico and in vitro of satellitomes, called “SatFisher protocol”, and we use this protocol in the quantification of different satDNAs, demonstrating their application as molecular markers in cryptic species of Astyanax and Psalidodon, and in particular, P. rivularis. Our results indicate that P. rivularis represents a species complex with at least five distinct species distributed along the Upper São Francisco River, with several cases of sympatry, and that one of these species corresponds to “Hyphessobrycon” santae, which we propose to relocate to the genus Psalidodon as Psalidodon santae comb. nov. Furthermore, our satellitome assembly and validation protocol successfully obtained quantitative markers to differentiate P. rivularis and P. fasciatus complexes species from the São Francisco and Paranaíba basins and between the genera Astyanax and Psalidodon. Our results indicate that the evolution and speciation of the P. rivularis complex are the result of several evolutionary processes together, such as chromosomal evolution, morphological adaptation, complex biogeographic processes such as vicariance, dispersion and headwaters captures, hybridism with other species, and, possibly, genomic processes not yet fully understood. We conclude by highlighting the need to conserve the small tributaries of the Upper São Francisco since they represent complex environments with rich taxonomic and genomic biodiversity and correspond to the preferred habitats of the P. rivularis group.