Overview

My recent research combines molecular biology techniques with physiological and metabolic studies to shed light on the environmental and evolutionary physiology of shrews and talpid moles (this latter assemblage includes terrestrial high-alpine, semi-aquatic and subterranean forms). I have sustained a long-term interest in these groups because of the divergent thermal, but convergent respiratory (most mole species spend their entire lives in environments with low oxygen and, in most cases, high carbon dioxide tensions) conditions they encounter on a daily and seasonal basis. This research presently is focusing on several (interrelated) areas:

I. Molecular Phylogeny of the Family Talpidae

Without robust hypotheses of evolutionary relationships among individual species within a lineage (a "family tree"), there is currently no meaningful basis upon which to separate the differential effects of inheritance versus selection-driven evolution. Earlier studies I conducted in collaboration with A. Shinohara (University of Miyazaki, Japan) and H. Suzuki (Hokkaido University, Japan), primarily employed mitochondrial DNA sequences and suggested that specializations for both semi-aquatic and fossorial habits arose independently twice during the evolution of this group. However, deep familial relationships remain unresolved. We are presently augmenting these data sets with slower evolving nuclear genes (RAG-1, ApoB, and α-, β- and ε-globin). Once in place, a detailed consensus talpid phylogeny should provide a necessary foundation for testing hypotheses pertaining to the evolution and conservation of adaptive mechanistic and molecular level specializations within this family from a historical, comparative standpoint.

II. Evolution of Metabolic and Respiratory Patterns in Talpid Moles

The biological specializations of burrowing mammals for subterranean habitation involve strategies for coping with the unfavorable gas tensions and high metabolic costs (both in terms of oxygen consumption and carbon dioxide production) of burrowing in compact soils, an activity considered to be the most energetically expensive and heat-liberating within the mammalian lineage. However, it is currently unknown what (if any) adaptive ventilatory, thermal and metabolic adjustments any species of mole adopts in response to the hypoxic hypercapnic conditions typical of closed-burrow systems. To address this issue, studies focused at understanding the evolution and extent of metabolic and respiratory specializations adopted by members of this group to mitigate the deletorius effects of hypoxia and hypercapnia are underway. One study, in collaboration with Stephen G. Reid (University of Toronto at Scarborough), examined the breathing patterns, metabolic rate and body temperature adjustments of coast moles (Scapanus orarius) to acute (1 hr) hypoxic (8-21% O₂), hypercapnic (0-10% CO₂), hypoxic/hypercapnic, and thermal (5-30°C) challenges. An additional comparative study on a closely related fossorial species (eastern mole, Scalopus aquaticus), whose hemoglobin and whole-blood exhibits dramatically different oxygen-binding characteristics, has recently been completed.

III. Evolution of Hemoglobin Oxygen-Affinity in Talpid Moles

In addition, I have been examining, in collaboration with Roy E. Weber (Aarhus University, Denmark), the functional and "mole"cular evolution of hemoglobin oxygen-affinity within members of this diverse group. This study should not only elucidate how subtle variations in the amino-acid sequence of this tetrameric molecule alter oxygen binding in response to changes in temperature and the red cell ligands H⁺, 2,3-DPG and Cl^-, but shed light on the evolutionary path that led to the exceptional hypoxia tolerance abilities we recently discovered in several members of this group. Such information is also critical to understanding how modifications in the structural and functional properties of this respiratory pigment have been influenced (evolved) by the life history traits adopted by various members of this poorly characterized lineage of mammals.

IV. Molecular Evolution of the Eutherian Beta-globin Family

Our understanding of β-globin gene cluster evolution within placental mammals is based solely upon data collected from species in the two most derived superorders, Laurasiatheria (ruminants) and Euarchontoglires (primates, rodents, rabbits). Hence, nothing is known regarding the gene composition and evolution of this cluster within the superorders Afrotheria (elephants, sea cows, hyraxes, aardvarks) and Xenarthra (sloths and armadillos). To address this shortcoming, M.Sc. student A. Sloan sequenced and classified 24 β-like globin loci from 11 afrotherian and 2 xenarthran species, and conducted a comprehensive analysis on the molecular evolution of these genes within these two basal eutherian clades. Results of this research challenge broadly accepted views pertaining to the evolution of the mammalian β-globin cluster. Additional studies on this topic have recently been completed in collaboration with Jay Storz, University of Nebraska.

V. Other Projects (with names of collaborating partners in brackets):

Seasonal energetics, torpor, and thermal biology of bats, star-nosed moles and shrews (Craig Willis, University of Winnipeg).

Functional and molecular adaptations of fetal llama blood gas-binding proteins to altitudinal hypoxia (Roy E. Weber, Aarhus, Denmark and Anibal Llanos, Santiago, Chile).

Resurrection, mechanism and adaptive physiochemical evolution of hemoglobins from extinct mammalian species (Alan Cooper, Adelaide, Australia, Michael Hofreiter, York, UK, Joerg Stetefeld, University of Manitoba, Chien Ho, Pittsburgh, USA and Roy E. Weber, Aarhus, Denmark).

Reconstructing hemoglobin and myoglobin evolution in birds and mammals (Michael Berenbrink, Liverpool, UK).

I'm also interested in most aspects of the natural history and evolution of moles. For more information on the biology, distribution and researchers of this unusual group of insectivores, please check out: