TAXONOMY, PHYLOGENY AND BIOGEOGRAPHY OF THE PUFFERFISHES OF THE GENUS COLOMESUS GILL, 1885 (TETRAODONTIFORMES: TETRAODONTIDAE)

Abstract

Colomesus is a Neotropical tetraodontid, which currently comprises two species only: the marine pufferfish C. psittacus and the Amazon pufferfish C. asellus. Both are endemic to the north-central South America, with the former occurring along the coast and the latter in several Amazonian drainages, Río Orinoco, Essequibo River, among others. Although the two purportedly valid species can be separated phenetically, their population variations were never investigated. Preliminary data obtained by the applicant and his advisor indicate that there are many undescribed species which are misidentified under these names, especially regarding C. asellus. The association between small size, low vagility, and the existence of distinct morphotypes distributed along different hydrographic basins are strong indicators that C. asellus is actually a species complex. The separation of the ancestral population of Colomesus in C. psittacus, which remained in marine waters, and C. asellus, which invaded the freshwaters of the South American, is related to the Miocene marine transgressions. However, the presence of different morphotypes indicates that the biogeographic history of the genus is by far more complex. Thus, the definition of the valid species of Colomesus species provides the foundations for the phylogenetic analysis, by which it will be possible to elucidate the biogeographical relationships within the genus. Based on morphological comparisons (external appearance, skeleton, and muscles), this study aims: 1) elucidate the taxonomy of Colomesus, carrying out re-descriptions of its valid species and descriptions of new one herein recognized, 2) undertake a phylogenetic analysis of Colomesus, providing cladistic diagnoses for the genus and its species, and 3) propose biogeographical hypotheses to explain the origin and diversification of Colomesus.