Phylogenetic relationships of sticklebacks (gasterosteidae), with emphasis on ninespine sticklebacks (Pungitius spp.)

Sticklebacks are widely used in comparative biology, but despite past systematic studies, questions of intrarelationships remain. We examined seven nominal species of Pungitius (P. pungitius, P. occidentalis, P. sinensis, P. tymensis, P. platygaster, P. laevis and P. hellenicus) and four other species of sticklebacks, Culaea inconstans, Gasterosteus aculeatus, Apeltes quadracus, and Spinachia spinachia, to hypothesize their systematic relationships. Thirty-three informative morphological (osteological and meristic) characters were analyzed. The outgroup comparison method was used for polarizing characters and cladistic methods for reconstructing the systematic relationships of the species. A 50% majority rule consensus tree was calculated for the 32 most parsimonious trees analyzed in the PAUP computer program. The results indicate that S. spinachia is the most primitive member of the family, followed by A. quadracus, and G. aculeatus. It appears that C. inconstans lies within the Pungitius lineage, possibly sister to P. hellenicus, suggesting that C. inconstans should be placed in the genus Pungitius. However, we defer recommending that Culaea be considered a synonym of Pungitius pending further studies to better resolve the Culaea/Pungitius clade.