Divergence of Mitochondrial Dna Is Not Corroborated by Nuclear Dna, Morphology, or Behavior in Drosophila Simulans

Abstract

Abstract. We ask whether the observed mitochondrial DNA (mtDNA) population subdivision of Drosophila simulans is indicative of organismal structure or of specific processes acting on the mitochondrial genome. Factors either intrinsic or extrinsic to the host genome may influence the evolutionary dynamics of mtDNA. Potential intrinsic factors include adaptation of the mitochondrial genome and of nucleomitochondrial gene complexes specific to the local environment. An extrinsic force that has been shown to influence mtDNA evolution in invertebrates is the bacterial endosymbiont Wolbachia. Evidence presented in this study suggests that mtDNA is not a good indicator of organismal subdivision in D. simulans. Furthermore, there is no evidence to suggest that Wolbachia causes any reduction in nuclear gene flow in this species. The observed differentiation in mtDNA is not corroborated by data from NADH: ubiquinone reductase 75kD subunit precursor or the Alcohol dehydrogenase-related loci, from the shape or size of the male genital arch, or from assortative premating behavior. We discuss these results in relation to a mitochondrial genetic species concept and the potential for Wolbachia-induced incompatibility to be a mechanism of speciation in insects. We conclude with an iterated appeal to include phylogenetic and statistical tests of neutrality as a supplement to phylogenetic and population genetic analyses when using mtDNA as an evolutionary marker.

Differential fitness of mitochondrial DNA in perturbation cage studies correlates with global abundance and population history inDrosophila simulans

“…Ballard (2004) The differential fitness of flies in perturbation cages, the geographical structure observed in the mtDNA (Ballard 2004) and the lack of detectable subdivision in three nuclear loci tested (Ballard 2000;Ballard et al 2002;Dean et al 2003), suggest that strong selection has acted on the mitochondrial genome. A mtDNA mutation may be positively selected if it causes a net increase in the fitness of the molecule in a specific local environment.…”

“…Before the commencement of the study it was determined that the lines mated at random (Ballard et al 2002) and no X-linked drivers were present. There was no departure from a 1 : 1 sex ratio in the F 1 or F 2 backcrosses of these lines ( p = 0.51).…”

“…Ballard then compared the mitochondrial variation with intron 1 of the alcohol dehydrogenase-repeated (Adhr) locus and showed that distinct forces were influencing the evolution of mtDNA and autosomal DNA. Subsequent studies showed that the mtDNA substructure is not observed at two additional nuclear loci (Ballard et al 2002;Dean et al 2003).…”

Towards a phylogenetic framework for the evolution of shakes, rattles, and rolls in Myiarchus tyrant-flycatchers (Aves: Passeriformes: Tyrannidae)

“…To illustrate concordances and discordances between mtDNA and morphology, we review cases of paraphyly and their systematic implications. Also, because renewed concern has been expressed lately (e.g., Ballard et al, 2002;Weckstein et al, 2001) about making taxonomic changes based solely on mtDNA, we offer our findings as a focus for further questions that should be addressed with characters from nuclear DNA, morphology and voice.…”

“…We plan separate, more detailed discussions of intraspecific phylogeography for later publications but have already examined the phylogeography and evolution of migration in the M. swainsoni complex (Joseph et al, 2003). Renewed concern has been expressed lately (e.g., Ballard et al, 2002;Weckstein et al, 2001) about making taxonomic changes based solely on mtDNA and so we offer our findings with this in mind.…”