Research

Natural Colonization

Small mammals may not seem to move very fast or very far, but they have colonized continents in just a few thousand years! Populations were contracted into refugia only 11,000 years ago because of glacial conditions, and have expanded out since then.

Genetic markers are being used in the lab to infer localizations of refugia and subsequent colonizations of Europe by shrews, voles and field mice. A diverse evolutionary history is evident. For example, field voles colonized Europe from many small refugia. Pygmy shrews, despite being incredibly tiny, lived in a cold part of central Europe during glacial conditions, then colonized much of Eurasia from there.

Adaptation and Speciation

Organisms can be constrained in extraordinary ways. The plethodontid salamanders, for example, are lungless and therefore their skin needs to be perpetually moist for gaseous exchange, yet they live in terrestrial environments where desiccation is always a risk. We are interested in the range of morphologies (size, shape and skin thicknesses) that plethodontids have, their respiratory physiology and how selective processes operating at the genome and transcriptome level can be shown to influence these features.

Another extraordinary life history that we examine in the lab is brood parasitism in bees, which is a trait that is shown by more bee species than eusociality. Using UCEs, we have been able to elucidate the phylogenetic relationship of the brood parasites and are now using the phylogeny to examine factors involved in the evolution of this life history characteristic, together with whole genome analysis.

Speciation is another focus in the lab with studies on moths, mice and shrews where a different set of chromosomes may lead to new species. In the European Corn Borer (ECB) moths, there is a region of suppressed recombination on one of the sex chromosomes, likely the result of one or more inversions. We are examining how that chromosomal region contributes to reproductive isolation in consideration of local populations that differ in number of generations per year and sex pheromone type. The ECB is a superb model for studying the impact of multiple factors that may contribute to reproductive isolation.

Our studies on house mice involve genomic analysis at different scales (local to global) and one aim is to tease out the importance of the extraordinary chromosomal variation in the species to reduce gene flow. This includes studies of hybrid zones between chromosomal forms, which are excellent testbeds for studying the role of the chromosomal rearrangements in processes that contribute to reproductive isolation.

Human-Animal Relationships

Small mammals have sometimes been able to travel incredible distances as unwanted guests on boats. House mice have been spread globally by humans and molecular markers can be used to track their movement. Once it is known where house mice came from and went to, it can be assumed that the people who unintentionally took them made the same journey. Thus, we are using house mice to tell us about human history, including prehistoric movements around the Indian Ocean, and Viking colonization history. We are also using house shrews; and particularly house/sewer rats for their role in pathogen transfer.

In addition, DNA and morphological studies of both modern and archaeological specimens have helped us study a Neolithic colonization of voles, and has even been applied to learning more about the domestication history of geese.

In the meadow vole, we have been studying the impact of humans in subdividing populations, using genomics to compare populations on either side of major road. We are interested in comparing gene transmission and viral transmission across the human-made environmental barrier.

Conservation Genetics

Evidence of small mammals is easily obtainable, directly through live-trapping or indirectly via feces and hair collections, and DNA can be extracted from these various sources. Through genomic methods, we have studied endemic small mammals in Mexico and Iberia, and voles and shrews in Alaska, to understand the impacts of habitat disturbance on genetics. The work in Alaska is part of a broader study examining how conifer die-off is influencing wildlife communities and human health.

Small mammals may be models of species at conservation risk, but also models of conservation threats. Applying genomic methods to study invasive species – the bank vole and the greater white-toothed shrew in Ireland – have informed us about the invasion process through comparison of the genetic makeup of populations at the invasion front with those in more established populations near the invasion point.