Phylogenetic relationships among Acestrorhynchus species (Ostariophysi: Characiformes: Acestrorhynchidae)

A total of 104 osteological and external morphological features were examined in 13 species of Acestrorhynchus and 15 outgroup taxa to advance a hypothesis of relationships within the genus. Two most parsimonious hypotheses corroborate the monophyly of Acestrorhynchus but differ in the hypothesized relationships of Acestrorhynchus heterolepis. Three proposed supraspecific assemblages are at least partially correlated with groups of species previously diagnosed on the basis of colour pattern: (1) Acestrorhynchus britskii, Acestrorhynchus grandoculis, Acestrorhynchus microlepis, and Acestrorhynchus minimus; (2) Acestrorhynchus falcirostris, Acestrorhynchus isalineae, and A. Acestrorhynchus nasutus; and (3) Acestrorhynchus abbreviatus, Acestrorhynchus altus, Acestrorhynchus falcatus, Acestrorhynchus lacustris, and Acestrorhynchus pantaneiro. In one hypothesis A. heterolepis is proposed as the closest relative of the clade formed by A. falcirostris, A. isalineae, and A. nasutus, and in the alternative hypothesis it is proposed as a sister species of the clade formed by A. abbreviatus, A. altus, A. falcatus, A. lacustris, and A. pantaneiro. Relationships among species of the latter clade remain unresolved. Two independent episodes of reduction of body size are hypothesized to have occurred within the genus: one associated with the clade formed by A. grandoculis and A. minimus, and the other with the clade formed by A. isalineae and A. nasutus. (c) 2007 The Linnean Society of London.