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ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Imported Fire Ant and Household Insects Research » Research » Publications at this Location » Publication #196370
Title: MITOCHONDRIAL DNA DIVERSITY AS A USEFUL POPULATION METRIC

Author
item ROSS, KENNETH - UNIVERSITY OF GEORGIA
item SHOEMAKER, DAVID

Submitted to: Biological Journal of the Linnean Society, London
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2007
Publication Date: N/A
Citation: N/A

Interpretive Summary: The utility of mitochondrial DNA (mtDNA) as population genetic marker within animal species is a largely unresolved, empirical issue highly relevant to its use in many evolutionary, conservation, and applied studies. A scientist at the Center for Medical, Agricultural, and Veterinary Entomology, USDA, ARS, Gainesville, Florida and the Department of Entomology, University of Georgia, Athens, Georgia describe here the results of a population genetic study of fire ants from South America addressing this important issue. We found that within-population genetic diversity in fire ants is significantly correlated between two different classes of nuclear markers and, more importantly, diversity is highly significantly correlated between the nuclear markers and the mtDNA using a variety of measures. The most reasonable explanation for this concordance is that differences in historical or current effective sizes of the study fire ant populations have influenced diversity at the two genomes in similar fashion. These findings are important because they suggest that patterns of mtDNA variation in this pest insect species record information useful for inferring its evolution and demography. Thus, despite the intriguing recent evidence from another study suggesting that mtDNA do not evolve neutrally when diversity is surveyed across higher-level taxa, our data suggest that it would be imprudent to indiscriminately dismiss markers of this genome as useful adjuncts to nuclear data in reconstructing major demographic and biogeographic features of species of unique economic, evolutionary, or conservation interest.

Technical Abstract: The recent study suggests that mitochondrial DNA (mtDNA) diversity does not reflect nuclear DNA diversity or presumed species demographic features across higher-level animal taxa or major ecological environments. This conclusion, explained by such events as recurrent positive selection in the history of a species’ non-recombining mtDNA genome, contributes to a growing consensus that mtDNA can be a unreliable population genetic marker for evolutionary, ecological, and conservation studies. We have generated an extensive data set for native South American populations of the fire ant Solenopsis invicta featuring 558 samples from 12 geographic populations analyzed for polymorphisms at two different classes of nuclear markers (allozymes, microsatellites) as well as the mtDNA genome. Seven polymorphic loci of each nuclear class were genotyped, and sequence variation over a 920-bp fragment of the mtDNA was surveyed. Within-population genetic diversity in fire ants is significantly correlated between the two classes of nuclear markers using either allele richness (Spearman rank correlation, r=0.864, P<0.001) or gene diversity (r=0.571, P=0.041) as diversity measures. More importantly, diversity is highly significantly correlated between the nuclear markers and the mtDNA using a variety of measures. The most reasonable explanation for this concordance is that differences in historical or current effective sizes of the study populations have influenced diversity at the two genomes in similar fashion. These results suggest that patterns of mtDNA variation in this insect species record information useful for inferring its evolution and demography. Because of the strictly maternal inheritance of mtDNA in most animal species, markers of this genome can provide a unique and complementary perspective on such features as patterns of migration and population expansion. Thus, despite the intriguing recent evidence showing that mtDNA does not evolve neutrally when diversity is surveyed across higher-level taxa, it seems imprudent to indiscriminately dismiss markers of this genome as useful adjuncts to nuclear data in reconstructing major demographic and biogeographic features of species of unique evolutionary or conservation interest.