CURRENT PROJECTS
Physiological development of painted turtles
The painted turtle (Chrysemys picta) is the most common and widespread turtle in North America; there are four subspecies (eastern, midland, southern, and western). From late May through early July, female nesting turtles lay subterranean clutches near water. The embryos develop inside of the egg until early September, when they hatch. Upon hatching, the hatchlings generally do not emerge from the ground but rather overwinter until late April at which time they journey from the nest and into the safety of the water. We study a small population (about 50 reproductively active females) at Round Lake State Park, near Sandpoint, Idaho. Our research focuses on the biotic and abiotic effects on egg and hatchling survival, as well as locomotor abilities of the hatchlings. The biotic effects we examine are those of the mom: the influence of size and age on the composition of the egg and offspring fitness. The abiotic effects are those of temperature, moisture, and soil.
Collaborator: Dan Warner
Insulin-like Growth Factors (IGFs) as mediators of life-history trade-offs
Life history theory, and specifically the pace of life hypothesis, postulates the existence of trade-offs with organisms falling at the “slow” end of the continuum exhibiting low annual reproduction, slow growth and long lifespan while organisms at the “fast” end have higher reproduction, faster growth and shorter lifespans. While the existence of the pace of life continuum has been documented in a myriad of species, from nematodes to mammals, little is know about the physiological mechanisms underlying these demographic and physiological trade-offs. The insulin-like signaling (IIS) pathway is an evolutionarily conserved molecular network that has been is involved in the pace of life trade-offs in model organisms. Key components of the IIS pathway include insulin-like growth factor 1 and 2 (IGF-1, IGF-2) and associated receptors (IGF-1R, IGF-2R). We explore the role of these components of the IIS pathway in growth and maternal investment of two genetically divergent ecotypes of the western terrestrial garter snake, Thamnophis elegans, which exhibit these slow and fast paces of life as well as female painted turtles, Chrysemys picta, across a spectrum of age.
Collaborators: Anne Bronikowski, Tonia Schwartz, Dawn Reding
The painted turtle (Chrysemys picta) is the most common and widespread turtle in North America; there are four subspecies (eastern, midland, southern, and western). From late May through early July, female nesting turtles lay subterranean clutches near water. The embryos develop inside of the egg until early September, when they hatch. Upon hatching, the hatchlings generally do not emerge from the ground but rather overwinter until late April at which time they journey from the nest and into the safety of the water. We study a small population (about 50 reproductively active females) at Round Lake State Park, near Sandpoint, Idaho. Our research focuses on the biotic and abiotic effects on egg and hatchling survival, as well as locomotor abilities of the hatchlings. The biotic effects we examine are those of the mom: the influence of size and age on the composition of the egg and offspring fitness. The abiotic effects are those of temperature, moisture, and soil.
Collaborator: Dan Warner
Insulin-like Growth Factors (IGFs) as mediators of life-history trade-offs
Life history theory, and specifically the pace of life hypothesis, postulates the existence of trade-offs with organisms falling at the “slow” end of the continuum exhibiting low annual reproduction, slow growth and long lifespan while organisms at the “fast” end have higher reproduction, faster growth and shorter lifespans. While the existence of the pace of life continuum has been documented in a myriad of species, from nematodes to mammals, little is know about the physiological mechanisms underlying these demographic and physiological trade-offs. The insulin-like signaling (IIS) pathway is an evolutionarily conserved molecular network that has been is involved in the pace of life trade-offs in model organisms. Key components of the IIS pathway include insulin-like growth factor 1 and 2 (IGF-1, IGF-2) and associated receptors (IGF-1R, IGF-2R). We explore the role of these components of the IIS pathway in growth and maternal investment of two genetically divergent ecotypes of the western terrestrial garter snake, Thamnophis elegans, which exhibit these slow and fast paces of life as well as female painted turtles, Chrysemys picta, across a spectrum of age.
Collaborators: Anne Bronikowski, Tonia Schwartz, Dawn Reding
PAST PROJECTS
Urbanization of yellow-bellied marmots
The loss of habitat to urbanization is detrimental to many species. However, there are some species that are able to survive, and in many cases thrive, in urban environments. Most work exploring patterns of species survival has focused on birds and been ecological in nature; little is known about the physiological mechanisms that allow animals to survive in urban environments. We are investigating a unique system around Spokane, Washington: that of urban yellow-bellied marmots. We are using glucocorticoid metabolites found in fur and feces to determine if yellow-bellied marmots (Marmota flaviventris) interpret rural or urban environments as more stressful. Additionally, we are examining behavioral variation and dietary differences among marmots along an urban-rural continuum.
The loss of habitat to urbanization is detrimental to many species. However, there are some species that are able to survive, and in many cases thrive, in urban environments. Most work exploring patterns of species survival has focused on birds and been ecological in nature; little is known about the physiological mechanisms that allow animals to survive in urban environments. We are investigating a unique system around Spokane, Washington: that of urban yellow-bellied marmots. We are using glucocorticoid metabolites found in fur and feces to determine if yellow-bellied marmots (Marmota flaviventris) interpret rural or urban environments as more stressful. Additionally, we are examining behavioral variation and dietary differences among marmots along an urban-rural continuum.
Altitudinal Range Expansion
Glucocorticoids are hormones that mediate physiological and behavioral responses to environmental conditions, and are directly involved in the allocation of energetic resources; they are constitutively secreted, but can also be released facultatively. With white-crowned sparrows, I have shown that individuals that have recently initiated breeding at high elevation exhibit greater variation in a stress-induced glucocorticoid response and more broadly that populations breeding at high altitude exhibit higher baseline and stress-induced levels of glucocorticoids. These results suggest an importance of modulation of hormonal mechanisms in facilitating breeding in high altitude environments by adjusting life history strategies, and that variation in these mechanisms is associated with facilitating altitudinal range expansion. In the current variable conditions of climate change, these findings are especially intriguing because they suggest that organisms with highly plastic glucocorticoid responses may be able to more easily shift breeding ranges.
Collaborators: Jason Davis, John Wingfield
Synchronicity of Breeding
Testosterone is highly relevant to the study of life history trade-offs because its effects on physiology and behavior can cause increased reproduction success, such sperm production and aggression, but that can also cause decreased reproductive success by means such as suppression of the immune system and inhibition of parental care. To mitigate these contradictory effects in regards to fitness, testosterone levels can fluctuate prior to and during breeding in response to environmental conditions, known as seasonal modulation, or social cues, known as social modulation. Together, these two types of modulation compose a significant pillar of John Wingfield's challenge hypothesis. I have proposed that there is an interaction between synchrony of a breeding population (related to length of the breeding season) and the degree of social modulation of testosterone. For example, in an extensive comparative study of Zonotrichia songbirds in North and South America, populations exhibiting an intermediate degree of breeding synchrony also exhibited the greatest degree of social modulation of testosterone.
Collaborators: Rodrigo Vasquez , John Wingfield
Glucocorticoids are hormones that mediate physiological and behavioral responses to environmental conditions, and are directly involved in the allocation of energetic resources; they are constitutively secreted, but can also be released facultatively. With white-crowned sparrows, I have shown that individuals that have recently initiated breeding at high elevation exhibit greater variation in a stress-induced glucocorticoid response and more broadly that populations breeding at high altitude exhibit higher baseline and stress-induced levels of glucocorticoids. These results suggest an importance of modulation of hormonal mechanisms in facilitating breeding in high altitude environments by adjusting life history strategies, and that variation in these mechanisms is associated with facilitating altitudinal range expansion. In the current variable conditions of climate change, these findings are especially intriguing because they suggest that organisms with highly plastic glucocorticoid responses may be able to more easily shift breeding ranges.
Collaborators: Jason Davis, John Wingfield
Synchronicity of Breeding
Testosterone is highly relevant to the study of life history trade-offs because its effects on physiology and behavior can cause increased reproduction success, such sperm production and aggression, but that can also cause decreased reproductive success by means such as suppression of the immune system and inhibition of parental care. To mitigate these contradictory effects in regards to fitness, testosterone levels can fluctuate prior to and during breeding in response to environmental conditions, known as seasonal modulation, or social cues, known as social modulation. Together, these two types of modulation compose a significant pillar of John Wingfield's challenge hypothesis. I have proposed that there is an interaction between synchrony of a breeding population (related to length of the breeding season) and the degree of social modulation of testosterone. For example, in an extensive comparative study of Zonotrichia songbirds in North and South America, populations exhibiting an intermediate degree of breeding synchrony also exhibited the greatest degree of social modulation of testosterone.
Collaborators: Rodrigo Vasquez , John Wingfield