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...
One hypothesis proposed to explain how the endocrine
system controls reproductive cycles in seasonally breeding
animals is that the hypothalamus undergoes seasonal
changes in sensitivity to negative feedback by gonadal
steroids. The result is seasonal changes in the secretion
of luteinizing hormone-releasing hormone (LHRH) and
gonadotropin secretion. The present experiments...
The high productivity of Eastern Boundary Upwelling Ecosystems (EBUE), some of the most productive ecosystems in the globe, is attributed to the nutrient rich waters brought up through upwelling. Climate change scenarios for coastal upwelling systems, predict an intensification of coastal upwelling winds. Associated with intensification in upwelling are biogeochemical...
During 1969-1971 I studied patterns of resource allocation and
behavioral interaction among Brandt's Cormorants, Pelagic Cormorants,
Common Murres and Pigeon Guillemots in the area of a breeding
colony on Yaquina Head on the central Oregon coast. Extensive studies
of the breeding colony were combined with detailed observations of the
distribution,...
Vegetation at the aquatic–terrestrial interface can alter landscape features through its growth and interactions with sediment and fluids. Even similar species may impart different effects due to variation in their interactions and feedbacks with the environment. Consequently, replacement of one engineering species by another can cause significant change in the...
Succession and organization of rocky intertidal zone surfgrass beds
(Phyllospadix scouleri Hook) were examined experimentally at two sites
on the Oregon coast. The interaction of three attributes of the plant
-- high persistence, high preemption, and slow recovery -- strongly
influences the organization of surfgrass beds. Permanent plots indicate
that...
I studied the feeding behavior of marked individuals of the
carnivorous marine snail Thais melones in a rocky shore habitat of
Pacific Panama. The population of snails consume a variety of
invertebrate species such as bivalves, limpets, and polychaetes.
Individuals exhibited a range of diet breadth, with some
specialized, but...
Recruitment of larvae from the plankton is an important determinant of
community structure in marine systems. In populations of many marine species,
recruitment determines the basic demographic parameters of immigration, emigration,
and reproduction. Moreover, the effect of recruitment as an "ecological subsidy" can
determine the strength of interactions among species...
Many marine fish populations are severely declining due to over-fishing, loss of both juvenile and adult habitats, and accelerating environmental degradation. Fisheries management and the implementation of marine protected areas (MPAs) and other conservation tools are currently hindered by large gaps in knowledge about larval dispersal and its subsequent effects...
Winters in north-temperate climates impose high
thermogenic demands upon small birds which are met by
seasonal acclimatization. This thesis investigates the
extent and mechanisms of seasonal acclimatization in darkeyed
juncos (Junco hyemalis) inhabiting western Oregon.
Although insulation is significantly increased in
winter, acclimatization is primarily metabolic. Increased
metabolism is required...