LOVEJOY, N; University of Manitoba: Phylogeny and Ontogeny of Needlefishes

Heterochrony, defined as evolutionary change in ontogenetic timing, can play an important role in morphological innovation. However, the relative importance of paedomorphosis and peramorphosis remains unclear. The beloniform fishes, including needlefishes, halfbeaks, flyingfishes, ricefishes, and sauries, have long been considered examplars of paedomorphosis. As needlefishes grow, their jaws pass through a “halfbeak” stage that resembles the adult jaw condition of the closely related family of halfbeaks. Based on this pattern, several authors have suggested that halfbeaks are “developmentally arrested” or paedomorphic needlefish derivatives. To test these ideas, and to better understand evolutionary changes in jaw ontogeny, the phylogenetic relationships among beloniform genera were assessed using mitochondrial, nuclear, and morphological characters. The structure of the phylogenetic tree falsifies the idea that halfbeaks are paedomorphic needlefishes. Instead, halfbeaks are basal relative to needlefishes, fitting the pattern predicted by a hypothesis of peramorphosis or recapitulation.