High levels of mitochondrial cytochrome b divergence in annual killifishesof the genus Cynolebias (Cyprinodontiformes, Rivulidae)

Phylogenetic relationships based on 324 base pairs of the mitochondrial cyt ochrome b gene were examined in 14 species of the genus Cynolebias. The mon opoly of the genus relative to three outgroup taxa belonging to tho family Rivulidac was supported by the sequence data. Bootstrap, values corroborate d the existence of intrageneric monophyletic units in both parsimony and Ne ighbour-joining analyses. These include a Cynolebias bellottii-C. woltersto rffi clade, a C. adloffi-2, C. duraznensis, C.viarius and C. adloffi-1 grou p, and a C. gymnoventris, C. luteoflammulatus pair and the strongly support ed assemblage that includes C. prognathus and C. cheradophilus clade. Phylo genetic relationships remain poorly supported for C. nigripinnis, C. affini s and C. alexandri, and unresolved among the precious ingroup clades. Cytoc hrome b sequences reveal an unexpectedly high level of divergence among spe cies of the genus Cynolebias. Consequently, cytochrome b shows good resolut ion of recent cladogenetic events but limited phylogenetic information at d eeper nodes. High levels of sequence divergence span a broad range within C ynolebias. The highest sequence divergence (c. 28%) occurred among C. anten ori and the remaining species of the genus. The minimum divergence value (4 .5%) is exhibited by sympatric species C. cheradophilus and C. prognathus. (C) 2000 The Linnean Society of London.