Análise taxonômica e história natural de Phalloceros Eigenmann 1907 (Actinopterygii: Atherinomorpha: Cyprinodontiformes: Poeciliidae) com distribuição no Quadrilátero Ferrífero, drenagens do alto rio Doce e São Francisco, MG

Abstract

The genus Phalloceros Eigenmann, 1907 is one of the 27 valid and described of the Poecillidae family, being represented by 22 small size species distributed in South America. For the of the totality of the species, only morphological data were used. However, with the advancement of molecular techniques, the validity of some has been questioned. Among the species, Phalloceros uai, Lucinda, 2008 is diagnosed autapomorphically by a large lateral square spot in larger specimens and was described for a single locality in the Velhas river. Later works extended its record in the basin, while others extended it to other adjacent sub-basins, Piracicaba and Santo Antônio rivers, bot belonging to the Doce river basin. In view of the divergences in current knowledge about the geographic distribution, adequate morphological and genetic recognition of the species, the main objective of this paper is to evaluate, through integrative taxonomy, the real status of specimens identified as P. uai from the upper Doce river and São Francisco river basins. The specimens were obtained between 2020-2021 from four points distributed in the upper Doce river and São Francisco river basins. The morphological analyzes comprised the measurement of total and standard length, height and length of the gonopodium and visual analysis of bone structures by the diaphanization method. Molecular analyzes were performed using the DNA barcoding technique using the COI mitochondrial gene. A total of 1622 specimens were collected, 997 females, 479 males and 186 juveniles. Of these fish, six morphotypes were recorded in relation to the pattern of spots. The total length of fish ranged from 8,21 – 48,60 mm, standard from 6,67 – 42,17 mm, while the height varied from 0,87 – 11,47 mm. The length of the gonopodium is positively related to the total length, and for an increase of one millimeter in the total length of the specimen, is expected an increase of 0,36 milimeters in the length of the gonopodium. Significant differences were observed in the mean values of gonopodium lengths, however no structural differences in the gonopodium were observed between specimens of different morphotypes and populations. The genetic sequences of Phalloceros showed approximation of less than 2% among sequences of P. uai and more than 2% among their congeners. The phylogenetic tree resulted in a monophyletic group with bootstrap support of 0,9993 containing all sequences of the species. The distribuition of P. uai covers the basins of the São Francisco river (das Velhas and Paraopeba rivers) and the Doce river (Santo Antônio and Piracicaba rivers). The surveys showed specimens with different morphotypes comparing to the original diagnosis by the number and disposition of lateral spots, although the most frequent one is in accordance with the original description. Morphologically, the populations showed no discrepancies from the original diagnosis. Molecular data indicated that the populations had a genetic distance of less than 2%, that is, they belong to the same species. The phylogenetic tree showed P. uai as monophyletic and well supported. In conclusion, the populations did not show enough morphological and molecular differences to be considered different species, fitting the diagnosis of P. uai, despite partially differing from the autapomorphy represented by a large and square lateral spot.