Filogeografia da espécie de peixe miniatura Fluviphylax simplex (Cyprinodontiformes: Fluviphylacidae) ao longo da Região Hidrogeográfica Amazônica.

Abstract

Introduction. The genus Fluviphylax comprises species of oviparous fish that are among the smallest individuals in the Amazon region, with a standard length of less than 22 mm. A miniaturized phenotype, as identified in Fluviphylax, corresponds to an extreme reduction in the body size of the adult individual. This reduction is influenced by the combination of plesiomorphic and apomorphic characteristics important in the evolutionary history of the group, such as increased morphological variability, the emergence of morphological novelties or structural reduction and simplification. Biotic pressures on the exploitation of food resources and escape from predation is a valid hypothesis for the miniaturization of freshwater ichthyofauna in the Amazon. Objective. The objective of this study is to determine the distribution area of Fluviphylax simplex, through the identification of specimens in ichthyological collections and the sequencing of a rapidly evolving marker, the mitochondrial Cytochrome Oxidase I (COI) gene. Methodology. through the sequencing of a fragment (600 bp) of the mitochondrial Cytochrome Oxidase I (COI) gene from 21 individuals of the species throughout its distribution. Two datasets (600 bp and 502 bp) were analyzed, resulting in two haplotype networks. In addition, a phylogenetic relationship between the haplotypes was inferred through Bayesian Inference. Results. The high haplotype diversity (Hd = 0.9381) observed globally in Fluviphylax simplex indicates high genetic variability demonstrating a higher proportion of haplotypes within populations. On the other hand, the low nucleotide diversity (π = 0.0150) is consistent with the relatively recent origin of the species in the late Miocene, approximately 6.5 million years ago. For the first time, the presence of the species was identified in the middle Rio Negro near Santa Isabel do Rio Negro, indicating the probable existence of a connection between the headwaters of the tributaries of the Solimões and Rio Negro rivers. The connection observed between the populations of F. simplex reveals that much of this communication may be associated with the floodplains, one of the main forces that direct the diversity of the ichthyofauna in the environment associated with seasonal factors, in addition to the headwaters of small streams within the forests. A description of the species' coloration in life was made based on the life of different individuals of the species distributed throughout its wide distribution.