Unraveling the systematics and evolution of the 'Geophagus' brasiliensis (Cichliformes: Cichlidae) species complex.

The 'Geophagus' brasiliensis complex is one of the most abundant groups of cichlids from eastern coastal basins in South America. Traditionally, this fish group has been recognized as incertae sedis because of phylogenetic uncertainties and unclear taxonomy. In addition, the remarkable morphological, chromosomal, and DNA variation reported over recent years in several populations of these cichlids has increased the debate about their species richness and their distributional range. Here, we tested the presence of independent evolutionary lineages within the 'G.' brasiliensis complex, addressing their taxonomic status and evolutionary relationships, including a comparative analysis of genetic and morphological patterns, based on an extensive dataset, comprising 172 sampling sites along most of their known range using a mitochondrial marker, RADseq data and geometric morphometrics. The number of putative species in the present study varied from 9 to 11 depending on the molecular species delimitation methods used. Our results revealed at least two putative new taxa ('Geophagus' sp. Doce and 'Geophagus' sp. Upper Contas). Morphometric analyses, particularly those based on Canonical Variate Analysis (CVA), revealed significant morphological differentiation between species within the main clades. On the other hand, analyses of morphological phylogenetic signal and phylomorphospace provided no evidence of adaptive differentiation among these species. Thus, diversification in the 'G.' brasiliensis complex seems to have been influenced by hydrogeological events that promoted allopatry, such as the presence of paleodrainages and distributional reconfiguration through river captures. We propose major changes in the known distribution of some species within the complex and conservatively suggest the recognition of 10 species within the 'Geophagus' brasiliensis complex, with the potential for further dividing 'G.' rufomarginatus after additional taxonomic evaluation.

Integrative systematics unveils the controversial identity of Engraulidae fishing stocks in a Neotropical estuary, northeast Brazil

In Brazil, the use and diversity of the common names of fish species, coupled with taxonomic uncertainties, hinder the reliability of fishing statistical data. In this scenario, there are the so-called pilombetas of the São Francisco River, an important fishing resource in region. Despite its importance, the real diversity of species identified in the area remains obscure. In order to properly identify and delimit the species popularly known as pilombetas, an integrative approach involving traditional taxonomy, geometric morphometrics and molecular systematics was applied. Results from geometric morphometrics and molecular analyses were consistent with the results of the traditional morphological analysis, also indicating the delimitation of six taxa belonging to Engraulidae in the lower São Francisco River. In addition, species delimitation methods revealed an intrapopulation genetic divergence of 1.7% for Lycengraulis grossidens. The results revealed that the currently known richness species of Engraulidae in the studied area has been underestimated. Thus, an updated taxonomic key is herein proposed for the Engraulidae species from the lower São Francisco River and estuary. The integrative analysis approach revealed to be effective to address taxonomic questions and help the management of stocks, ensuring the maintenance of local diversity of fishes in the Neotropical region.(AU)

No Brasil, o uso e a diversidade dos nomes comuns para espécies de peixes, associado a incertezas taxonômicas, dificultam a confiabilidade dos dados estatísticos da pesca. Nesse cenário, existem as chamadas pilombetas do rio São Francisco, um importante recurso pesqueiro da região. Apesar de sua importância, a real diversidade de espécies identificadas na área permanece obscura. Para identificar adequadamente as espécies conhecidas como pilombetas, uma abordagem integrativa envolvendo taxonomia tradicional, morfometria geométrica e sistemática molecular foi aplicada. Os resultados das análises moleculares e de morfometria geométrica foram consistentes com os resultados da análise morfológica tradicional, indicando também a delimitação de seis táxons pertencentes a Engraulidae no baixo São Francisco. Além disso, os métodos de delimitação de espécies revelaram divergência genética intrapopulacional de 1,7% em Lycengraulis grossidens. Nossos dados revelaram que a riqueza de espécies atualmente conhecida de Engraulidae na área estudada é subestimada. Assim, uma chave taxonômica atualizada é aqui proposta para as espécies de Engraulidae do baixo rio São Francisco e seu estuário. A abordagem de análise integrativa revelou ser efetiva para tratar de questões taxonômicas e ajudar no gerenciamento de estoques, garantindo a manutenção da diversidade local de peixes na região Neotropical.(AU)

Cryptic Chromosomal Diversity in the Complex "Geophagus" brasiliensis (Perciformes, Cichlidae).

Among American cichlids, Geophagus stands out as a species-rich genus widespread over neotropical region. Despite their diversity and confusing taxonomy, only few and basic chromosomal reports are available in populations/species along Atlantic coast, hindering our understanding about evolutionary trends in this genus. Therefore, detailed chromosomal studies were performed in "Geophagus" brasiliensis complex from coastal rivers in northeastern Brazil, totalizing seven populations of Geophagus brasiliensis and one of Geophagus itapicuruensis. All samples shared a diploid number (2n) of 48 divided into 2 submetacentric and 46 subtelocentric/acrocentric chromosomes with (peri)centromeric heterochromatin, hypothesized as a symplesiomorphy for Geophagini. Although G. itapicuruensis and two populations of G. brasiliensis presented single NORs on short arms, multiple GC-rich rDNA sites were observed in the remaining G. brasiliensis samples, ranging from three to six NOR-bearing chromosomes. Inversely, 5S rDNA sites were invariably located at interstitial region on a st/a pair, nonsyntenic to NORs. A compilation of the data set in Geophagus shows that their chromosomal evolution has been driven by pericentric inversions and microstructural changes. Besides, the divergence found in northeastern Brazil places this region as a biodiversity hotspot. A taxonomic revision in the complex "Geophagus" brasiliensis is recommended with the support of cytogenetic analyses.