Life Sciences Seminar Series

Name:Kevin McCracken
Associate Professor
Affiliation:Institute of Arctic Biology, Department of Biology and Wildlife, UAF
Title:Genetic adaptation and phenotypic plasticity in South American ducks
Date:Friday, 8 March 2013
Location:Elvey Auditorium, 214 Elvey Building

About the Speaker:

My research interests are in evolutionary biology and the genetics of adaptation. Field studies and analytical methods from a variety of different disciplines including genetics, physiology, protein chemistry, and wildlife population biology are being used to address questions about the process of adaptation and natural selection, at both the molecular level and in whole organisms. Waterfowl and other waterbird species inhabiting high-altitude regions such as the Andes are of particular interest.

High-altitude regions are characterized by extreme differences in ambient pressure and temperature that vary across elevational gradients. Hypoxia in particular is one of the most important factors influencing survival at high elevations, and biochemical changes in the blood protein hemoglobin (Hb) have been shown to mitigate the effects of chronic hypoxia in high-altitude adapted populations. Surveys of hemoglobin amino acid polymorphism in Andean waterfowl suggest that genotypic variants that are over-represented in high-altitude populations have different fitness rankings in different elevational zones and influence Hb-O2 affinity. Our studies have further revealed that parallel substitutions evolved in distantly related lineages and are concentrated in the same few regions of the protein. Experimental studies of Hb function and blood properties are being combined with genome-wide population genetics analyses to study the mechanistic basis of these apparent adaptations. One question we aim to answer is whether the same or different molecular mechanisms underlie parallel changes in replicate lineages that independently colonized the Andes and other high-altitude regions. Other questions focus on the role of phenotypic plasticity and how it may alternatively promote the process of genetic adaptation or shield genotypes from natural selection. Specifically, we are examining how individuals modulate their Hb-O2 carrying capacity and vary their ventilation rate and cardiovascular response when they disperse across elevational gradients or are challenged with acute hypoxia.

Our sampling/experimental protocols utilize comparative analyses of codistributed species that are at different stages in the speciation process, for which variable amounts of time have elapsed since these populations first colonized high-altitude habitats and for which gene flow is also highly variable (ranging from divergent species pairs for which gene flow has virtually ceased, to incipient pairs of populations that are still strongly glued together and characterized by high rates of dispersal). In the latter case, this approach is well-suited for studies of migration-selection balance, which can also be informed by actual dispersal data using mark-recapture. Additional projects in our lab are examining the influence of selection on non-coding DNA sequences, as well as a variety of population-level studies of waterfowl species, including their role as intercontinental vectors of avian influenza, paramyxoviruses, and blood parasites.

Collaborators include Jay Storz at the University of Nebraska, Roy Weber at the University of Aarhus, Jeff Peters at Wright State University, Mary Kuhner at the University of Washington, and Daniel Cadena and his students at Universidad de los Andes in Colombia. We also maintain close working ties with investigators at the Alaska Science Center and several South American museums including the Centro de Ornitologia y Biodiversidad (CORBIDI) and the Museo Argentino de Ciencias Naturales (MACN).

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