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2006 The Society for the Study of Evolution. All rights reserved. Evolution, 60(2), 2006, pp. 292302
 

Summary: 292
2006 The Society for the Study of Evolution. All rights reserved.
Evolution, 60(2), 2006, pp. 292­302
EXTENSIVE INTROGRESSION OF MITOCHONDRIAL DNA RELATIVE TO NUCLEAR
GENES IN THE DROSOPHILA YAKUBA SPECIES GROUP
DORIS BACHTROG,1,2 KEVIN THORNTON,2 ANDREW CLARK,2 AND PETER ANDOLFATTO1,3
1Section of Ecology, Behavior and Evolution, University of California­San Diego, La Jolla, California 92093
2Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
Abstract. Studies of gene flow between recently diverged species can illuminate the role of natural selection in the
formation of new species. Drosophila santomea and D. yakuba are recently diverged, partially reproductively isolated
species that continue to hybridize in the wild, and appear to be reproductively isolated from the more distantly related
species D. teissieri. We examine patterns of nucleotide polymorphism and divergence in these three species at multiple
X-linked, Y-linked, and mitochondrial markers. All three species harbor drastically reduced variability on the Y
chromosome relative to the X, as expected for a nonrecombining chromosome subject to variation-reducing selection.
The three species are generally well differentiated at the nuclear markers, with little evidence for recent introgression
for either the X- or Y-linked genes. Based on the nuclear genes, we estimate that D. santomea and D. yakuba diverged
about one-half million years ago and split from D. teissieri about one million years ago. In contrast to the pattern at
nuclear loci, all three species share a very similar mtDNA haplotype. We show that the mtDNA must have recently
introgressed across species boundaries in the D. yakuba subgroup and that its fixation was driven by either selection
on the mitochondria itself or other cytoplasmic factors. These results demonstrate that different regions of the genome

  

Source: Andolfatto, Peter - Department of Ecology and Evolutionary Biology, Princeton University

 

Collections: Biology and Medicine