title: Signatures of natural selection in the mitochondrial genomes of Tachycineta swallows and their implications for latitudinal patterns of the 'pace of life'.
abstract: Latitudinal variation in avian life histories can be summarized as a slow-fast continuum, termed the 'pace of life', that encompasses patterns in life span, reproduction, and rates of development among tropical and temperate species. Much of the variation in avian pace of life is tied to differences in rates of long-term metabolic energy expenditure. Given the vital role of the mitochondrion in metabolic processes, studies of variation in the mitochondrial genome may offer opportunities to establish mechanistic links between genetic variation and latitudinal 'pace of life' patterns. Using comparative genomic analyses, we examined complete mitochondrial genome sequences obtained from nine, broadly distributed Tachycineta swallow species to test for signatures of natural selection across the mitogenome within a phylogenetic framework. Our results show that although purifying selection is the dominant selective force acting on the mitochondrial genome in Tachycineta, three mitochondrial genes (ND2, ND5, and CYTB) contain regions that exhibit signatures of diversifying selection. Two of these genes (ND2 and ND5) encode interacting subunits of NADH dehydrogenase, and amino residues that were inferred to be targets of positive selection were disproportionately concentrated in these genes. Moreover, the positively selected sites exhibited a phylogenetic pattern that could be indicative of adaptive divergence between "fast" and "slow" lineages. These results suggest that functional variation in cytochrome b and NADH dehydrogenase could mechanistically contribute to latitudinal 'pace of life' patterns in Tachycineta.
authors.affiliation: Department of Animal Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. Electronic address: stager2@illinois.edu.
authors.forename: Maria
authors.initials: M
authors.lastname: Stager
authors.affiliation: WestLand Resources, Inc. 4001 E. Paradise Falls Drive, Tucson, AZ 85712, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Cerasale
authors.affiliation: Department of Zoology, Tel Aviv University, Tel Aviv 6997801, Israel.
authors.forename: Roi
authors.initials: R
authors.lastname: Dor
authors.affiliation: Cornell University Museum of Vertebrates, Department of Ecology & Evolutionary Biology and Laboratory of Ornithology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: David W
authors.initials: DW
authors.lastname: Winkler
authors.affiliation: Department of Animal Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Zachary A
authors.initials: ZA
authors.lastname: Cheviron
mesh_terms: D000818:Animals; D045303:Cytochromes b / Q000235:genetics; D019143:Evolution, Molecular; D014644:Genetic Variation; D054629:Genome, Mitochondrial; D009245:NADH Dehydrogenase / Q000235:genetics; D010802:Phylogeny; D012641:Selection, Genetic; D046388:Swallows / Q000235:genetics*
chemical_list: D045303:Cytochromes b; D009245:NADH Dehydrogenase
keywords: Cytochrome b; Diversifying selection; NADH dehydrogenase; Purifying selection