MOLECULAR PHYLOGENETIC STUDY OF DROSOPHILA

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On the basis of internal marphology and biogeography, Throckmorton (1966,1975) proposed a hypothesis for phylogenetic relationships between the species group of the family Droso-philidae, which has been widely accepted by many evolutionary biologists. On the other hand, using a caldistic analysis of many external morphological traits, Grimaldi (1990) recently put forward another hypothesis that was very different from Throckmorton's. We therefore re- examined phlogenetic relationships between the species of the family Drosophilidae by nucleotide sequences of the alcohol dehydrogenase (ADH) and the mitochondrial ND2 genes. The molecular phylogenetic trees obtained from these sequences were significantly different from Grimaldi's hypothesis. On the whole, our results supported the Throckmorton's hypothesis. However, our trees offered some new knowledege for understanding Drosophila phylogeny which have not been pointed out neither in Throckmorton's or Grimaldi's hypotheses. Among those, a information for the origin of Hawaiian drosophilids is very interesting. The hypothesis that Hawaiian drosophilids originated in the immigrans- Hirtodrosohila radiation (Throckmorton, 1975) has been widely accepted by many drosophilists. In this study, however, this group is found to be more closely related to the species of the virilis- repleta lineage that diverged from the immigrans- Hirtodrosohila lineage.