1. Temperature, body size, and fitness
Why do individuals that inhabit cold environments attain enormous body sizes? For example, in central Canada's Algonquin Park, we catch snapping turtles that weigh over 18kg (more than 40 lbs); this is much larger than this species becomes in southern environments. Also, think of animals like the Chinese giant salamander, which inhabit relatively cool streams; individuals of this species can measure over 1.5m long and weigh up to 30kg (66lbs). Using meta-data, long-term data monitoring data, and experimental manipulation, my group integrate principles of life-history theory and
physiological ecology to understand how body size and life-histories are optimized with respect to temperature and growing season length. Some general questions include: how have life-history traits in northern reptiles evolved since post-glacial range expansion? What are the benefits of indeterminate growth in environments that are strongly seasonal compared to environments that are less seasonal? Are Bergmann clines more closely associated with temperature or growing season length, and why do these clines vary in direction in different clades? How have decadal warming patterns affected growth and reproduction in northern reptiles and amphibians?
2. Maternal effects in contemporary populations
4. The micro- and macro-evolution of body size
Classic life-history theory predicts that parents trade off the fitness accrued from an increase
in resource investment per offspring (i.e., juvenile size) against the fitness
losses resulting from a reduction in parental fecundity. This trade-off
generates parent-offspring conflict over body size: given that size is positively
related to fitness, the level of investment per offspring that maximizes
parental fitness is lower than the level that maximizes offspring fitness. As a
result, parents produce juveniles of a size that is optimal from the parents’
perspective, but suboptimal from the juveniles’ perspective. The predicted
effect of this trade-off is recurrent upward selection on juvenile size in every
generation of offspring production. This argument extends to selection on adult size as well, provided genetic variation in adult size is attributable to variation in investment per offspring (i.e., maternal-genetic variation for body size). I am currently extending these principles to help explain macro-evolutionary trajectories of life-histories.
I am also interested in the macro-evolution of body size and life-histories in ectotherms, particularly from the perspective of temperature-induced oxygen limitation (the "temperature-size rule"). Using a large database on amphibian biology (see below), we are currently exploring how temperature and oxygen limitation affect the evolution of both body size and the maternal effect on body size in amphibians of the world.
5. The amphibian megabase project
6. The ecology, evolution, and conservation of coldwater fishesIn the near future, we will have a coldwater aqulab here at the University of Toronto. Research will focus on the evolutionary ecology and conservation of cold-water fishes.