Competitive exclusion is a key concept in ecology describing the exclusion of one species by another from access to a limited resource. Competitive interactions between chipmunk species in the Great Basin, documented by James Brown in 1970, are often used as a textbook example of competitive exclusion. Whether competitive interactions...
During 1966, 1967, and 1968 extensive field investigations were
carried out in Mount Rainier National Park. These included continuous
research during the summer months, and weekend activities
during the winter months. Small mammals were trapped and
observed, and the larger mammals were observed exclusively. The
summer trapping consisted of two...
In the rat thymus, four stages of development have been distinguished:
(1) a newborn stage (Stage I), (2) an accelerated growth
stage (Stage II), (3) an involuting stage (Stage III), and (4) an involuted
stage (Stage IV) . There were three major types of thymic
lymphoid cells: small (STL), medium...
Although endothermy is one of the most significant evolutionary developments in the vertebrates, its origins among extinct taxa have traditionally been difficult to determine. Endothermy is primarily an attribute of the "soft anatomy," and its key features, such as complex lungs, elevated blood oxygen carrying capacity and mitochondrial density, do...
Population genetic structure is widespread in many organisms and can be found at small spatial scales. Fine-scale differentiation is the result of ecological and evolutionary processes working together to produce an overall pattern, but the relative importance of these factors in population differentiation is poorly understood. The goals of my...
A primary goal of population genetics is to identify the role of
microevolutionary forces in producing observed patterns of molecular and phenotypic
variation. I conducted four studies in the northern leopard frog, Rana pipiens, to
determine just how mutation, migration, genetic drift, and selection influenced,
genetic structure of mitochondrial DNA...
There is little, if any, direct fossil evidence of the cardiovascular, respiratory, reproductive or digestive biology of dinosaurs. However, a variety of data can be used to draw reasonable inferences about the physiology of the carnivorous theropod dinosaurs (Archosauria: Theropoda). Extant archosaurs, birds and crocodilians, possess regionally differentiated, vascularized and...
How complex traits evolve continues to be a major focus of evolutionary
investigation. A current topic of debate is the hypothesis that the phenotypic
integration of complex traits gives rise to evolutionary constraints. I studied two color
traits in the common garter snake, Thamnophis sirtalis, that show a high level...