Biomedical subjects

Kevin E Omland

Publications and source records attributed to Kevin E Omland.

4 recordsLinked to original sources

PubMed2006

Genetic signatures of intermediate divergence: population history of Old and New World Holarctic ravens (Corvus corax).

Many studies of phylogeography, speciation, and species limits restrict their focus to a narrow issue: gene tree monophyly. However, reciprocal monophyly does not provide an ideal touchstone criterion of any aspect of evolutionary divergence. There is a continuum of divergence stages as isolated populations go from initial allele frequency differences to well-differentiated species. Studying intermediate stages of divergence will increase our understanding of geographical speciation, species limits, and conservation priorities. We develop a conceptual framework and terminology for thinking about the stages of 'intermediate polyphyly'. The Holarctic clade of common ravens (Corvus corax), found throughout much of Eurasia and North America, provides a case study of these stages of intermediate divergence. We used coalescent, phylogenetic, and population genetic methods to investigate the history and current status of this Old World-New World distribution using 107 mitochondrial control region sequences. Phylogenetically, New World and Old World samples are intermixed. However, most samples are grouped into small subclades that are restricted to either the New World or the Old World, and only one haplotype is shared between the hemispheres. Analysis of moleculalr variance (amova) results reflect this low haplotype sharing between hemispheres (Phi(ST) = 0.13, P < 0.01). Isolation with Migration (im) coalescent results suggest a sustained period of divergence between the hemispheres and low levels of maternal gene flow. Although there has not been sufficient time to evolve reciprocal monophyly and some gene flow may occur, New World and Old World ravens are genetically quite distinct. We use this example to demonstrate these early stages of divergence as populations go from sharing only internal haplotypes, to sharing no haplotypes, to having population specific subclades. Studies of phylogeography, speciation and systematics will benefit from increased attention to these stages of intermediate polyphyly.

Animals↗

PubMed2006

Using spectral data to reconstruct evolutionary changes in coloration: carotenoid color evolution in New World orioles.

Carotenoid-based colors are thought to play an important signaling role in many animal taxa. However, little is known about evolutionary changes in carotenoid coloration, especially among closely related species. We used a phylogenetic perspective to examine carotenoid color changes within New World orioles (genus Icterus). Oriole color was quantitatively measured using reflectance spectrometry. We found continuous variation from short- to long-wavelength carotenoid colors in extant orioles--perceived by humans as ranging from yellow to scarlet--suggesting that these carotenoid-based colors have evolved as a continuous character. Ancestral state reconstruction suggests that short- and long-wavelength carotenoid colors have evolved independently multiple times, likely from a middle-wavelength ancestor. Although color showed considerable lability, we found a significant amount of phylogenetic signal across the entire genus. This implies that while labile, the colors of closely related taxa tended to resemble each other more than would be expected due to chance. To our knowledge, this is the first study to use quantitative character states derived from reflectance spectra in ancestral state reconstruction. Reflectance spectra provide an unbiased quantitative description of color that allowed us to detect subtle changes among closely related taxa. Using these quantitative methods to score and reconstruct color changes among closely related taxa provides a better understanding of how elaborate animal colors evolve.

Animals↗

PubMed2005

Phylogenetics of wigeons and allies (Anatidae: Anas): the importance of sampling multiple loci and multiple individuals.

Species-level DNA phylogenies frequently suffer from two shortcomings--gene trees usually are constructed from a single locus, and often species are represented by only one individual. To evaluate the effect of these two shortcomings, we tested phylogenetic hypotheses within the wigeons and allies, a clade of Anas ducks (Anatidae) composed of five species. We sequenced two nuclear introns from the Z-chromosome-linked chromo-helicase binding protein gene (CHD1Zb and CHD1Za) and the mitochondrial DNA (mtDNA) control region for multiple individuals sampled from widespread geographic locations. We compared these phylogenies to previously published phylogenies constructed from morphology and protein coding regions of mtDNA. Relative to other nuclear introns, CHD showed remarkable phylogenetic utility. Of the 26 CHD1Zb alleles identified, only one was shared between two species, and the combined CHD datasets revealed that four of the five species were consistent with monophyly. Several species shared mtDNA haplotypes, which probably was a result of interspecific hybridization. Overall, the nuclear CHD tree and the mtDNA tree were more congruent with coding regions of mtDNA than they were with morphology.

Animals↗

PubMed2005

Late Pleistocene divergence between eastern and western populations of wood ducks (Aix sponsa) inferred by the 'isolation with migration' coalescent method.

During the Late Pleistocene, glaciers sundered many species into multiple glacial refugia where populations diverged in allopatry. Although deeply divergent mitochondrial DNA (mtDNA) lineages often reflect the number of refugia occupied, it is unlikely that populations that split during the recent Wisconsin glaciations will have reached reciprocal monophyly. We examined mtDNA control region sequences from eastern and western populations of wood ducks (Aix sponsa) to determine whether their current, disjunct distribution is consistent with the occupancy of two glacial refugia. We used the 'isolation with migration' coalescent method (im) to simultaneously estimate effective population sizes, maternal gene flow, and time since divergence. We found 24 unique haplotypes, none of which were shared between the eastern and western populations, but we did not find diagnostic monophyletic lineages suggestive of long-term isolation in multiple glacial refugia. However, a high Phi ST (0.31) indicates that eastern and western populations are well differentiated in mtDNA, and results from im suggest that these populations have been diverging, without extensive gene flow, for 10,000 to 124,000 years. Results from im further suggest that these populations most likely split about 34,000 years ago, and this time of divergence is consistent with the occupancy of multiple glacial refugia during the Late Wisconsin glaciation. Eastern wood ducks are characterized by high genetic diversity, a large effective population size, and a recent population expansion, while western wood ducks have much less genetic diversity, a smaller population size, and have not undergone a recent population expansion.

Analysis of Variance↗