Phyogenetic interrelationships, evolution and miniaturization in Crenuchinae Günther, 1864 (Crenuchidae, Characiformes)

• Grant number: 24/23109-2
• Support Opportunities: Scholarships in Brazil - Master
• Start date: June 01, 2025
• End date: July 31, 2026
• Field of knowledge: Biological Sciences - Zoology - Morphology of Recent Groups
• Principal Investigator: Murilo Nogueira de Lima Pastana
• Grantee: Michael Martins Romangnoli
• Host Institution: Museu de Zoologia (MZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Crenuchinae is a subfamily of South American darters (Crenuchidae: Characiformes) that encompasses five valid species, including miniaturized taxa (i.e., not exceeding 26 mm in standard length) and species of high value in the ornamental fish trade, such as the sailfin tetra and the black morpho tetras (genera Crenuchus and Poecilocharax, respectively). Of the four valid Poecilocharax species, two are critically endangered and known only for Apuí, one of the most deforested municipalities in Brazil. Although the phylogenetic relationships among the subfamily's species are poorly understood, the monophyly of Crenuchinae is strongly supported by the presence of the frontal organ, a highly complex and exclusive synapomorphy. Additionally, the knowledge about the evolution of miniaturization in this clade remains incipient: despite this phenomenon being widely documented in Neotropical fishes, with at least 213 identified species, osteological-descriptive studies on miniaturized phenotypes in Characiformes are limited to Acestrorhamphidae, just one of the 28 families within the order. This knowledge gap regarding miniaturized phenotypes, combined with the absence of phylogenetic studies for Crenuchinae, motivated the development of this project. Due to its small number of known species, Crenuchinae represents a model group for studies on miniaturization, as morphological analyses of miniaturized phenotypes can be conducted within a comprehensive phylogenetic context, encompassing all species of the subfamily. This study will enable the mapping of miniaturization evolution events along the phylogeny of Crenuchinae, contributing to a deeper understanding of this phenomenon in Characiformes.