Phylogenetic relationships among the mollies (Poeciliidae: Poecilia: Mollienesia group) based on mitochondrial DNA sequences

Abstract

A 505-bp sequence from the control region (D-loop) and the complete 1047 bp of the NADH dehydrogenase subunit 2 (ND2) gene were examined for individuals from 11 species of mollies included in the group Mollienesia. All three species of sailfin mollies of the Poecilia latipinna species complex were included (P. latipinna, P. petenensis and P. velifera); this group is named after the strikingly large dorsal fin in males. Six members of the shortfin P. mexicana complex (P. gilli, P. mexicana, P. orri, P. catemaconis, P. latipunctata and P. sulphuraria) and two members of the shortfin P. sphenops complex (P. butleri and P. sphenops) were examined. To test the monophyly of the Molliensia group, two species of mollies outside of this group were included: P. caucana and P. vivipara. The guppy P. reticulata was used as the outgroup taxon. Similar topologies were recovered using three phylogenetic methods (maximum parsimony, neighbour joining and maximum likelihood) and revealed several interesting relationships. First, all members of Mollienesia form a monophyletic group, which supports the more traditional taxonomy and classification of these species as comprising the subgenus Mollienesia as proposed previously. Second, the species of mollies outside of the Mollienesia group are only loosely allied with the Mollienesia clade; P. caucana is the sister taxon to Mollienesia, but P. vivipara lies outside of this Mollienesia-P. caucana clade. Third, the three sailfin molly species form a monophyletic group within the Mollienesia clade, but interestingly, shortfin species are paraphyletic due to the inclusion of a single shortfin species, P. latipunctata, within this sailfin clade. The exact placement of P. latipunctata within the sailfin clade is unclear. Fourth, the remaining shortfin species form a monophyletic sister clade to the sailfins and are separated into two groups, one containing P. sphenops and P. catemaconis and a second lineage leading to the remaining shortfin species. This arrangement does not support the morphological separation of shortfins into a P. sphenops and a P. mexicana species complex. Bootstrap analyses support the monophyly of Mollienesia (78–85%), the sailfin clade (100%) and the shortfin clade (79–95%).