Deer Mouse Botfly Co-evolution
With Nathan Senner, Zac Cheviron, and Art Woods, we are studying how elevation changes the response of animals to parasitic infection. In the Fall, deer mice can become infected with the larvae of a botfly (genus Cuterebra), which feeds on its living tissue as it develops. We are finding that physiological performance and overwinter survival are reduced by botfly infections, but that this reduction depends on whether mice live at low- or high-elevation.
High-Altitude Adaptation
Extreme environments are fertile grounds for investigating the mechanisms of adaptation, since the selection pressures experienced there are few in number and severe in degree. High-altitude is one such environment, where O2 deprivation (hypoxia) and cold are pervasive. High-altitude, winter-active mammals for example must extract O2 for thermoregulation from an O2 poor environment. Our work explores the physiology, genetics, and functional genomics of adaptation to high-altitude, which are characterized by extremes in hypoxia and cold. High-altitude deer mice (Peromyscus maniculatus) are a tractable model since they have a broad elevational distribution, occurring from sea level to the Rocky Mountains.
The Role of Phenotypic Plasticity in Adaptive Evolution
A controversial question in evolutionary biology is whether phenotypic plasticity (when one genotype produces multiple phenotypes) acts to promote or inhibit adaptive evolution. Early theory dismissed the importance of plasticity in evolution because environmentally induced phenotypes can shield genetic variation from natural selection when they perfectly match local adaptive optima [Schlichting and Pigliucci 1998]. Decades of work has demonstrated however that plasticity can indeed facilitate adaptation, most notably when that it brings individuals in the vicinity of the novel adaptive optimum. Very recent work now suggests that a great deal of phenotypic plasticity in novel environments is maladaptive (in that it lowers fitness), but that maladaptive responses themselves facilitate adaptation evolution through increasing the strength of natural selection.
In low-altitude mammals, physiological responses to high-altitude hypoxia are very often maladaptive. Common responses include an overproduction of red blood cells and a global constriction of the lung vasculature, which can lead to heart hypertrophy, limit aerobic capacity and can eventually cause chronic disease or death. As such, these maladaptive responses are often not present in high-altitude taxa, which is presumably the result of adaptation. Our studies suggest that selection to suppress ancestral maladaptive plasticity plays a role in adaptation.
Click here to view a presentation from the Evolution conference in France on how maladaptive phenotypic plasticity contributes to high-altitude adaptation!
Evolution of Osmoregulation in the Alewife
Invasions into new and challenging environments are fundamental to the creation of biodiversity. One of the most important invasions in history is the invasion of freshwater by marine vertebrates, which is rooted in the diversification of fishes and the origin of tetrapods. My research fills a gap in our understanding of freshwater invasions: the adaptations that allow organisms to overcome the physiological barrier between freshwater and the sea. To do so, we use alewife (Alosa pseudoharengus) as a model. Dams built during European settlement of coastal New England blocked the anadromous migrations of alewives, which historically breed in freshwater, but live at sea. This damming has resulted in independently formed landlocked populations that live entirely in freshwater.
Velotta Lab 