Variation in performance is ubiquitous among individuals in nature and can be focused on particular life histories stages of different taxa. I have found that variability among individuals affects the size structure of populations, their extinction risk, and the quantitative tools we use to describe populations. I use both models and data to show how variation that is not distributed independently among individuals (autocorrelation exists) is important to quantitative descriptors of populations. Mei Wang and I (as part of the Center for Integrating Statistics and Environmental Sciences (CISES)) have developed a simple matrix projection model to describe this phenomenon in kelp and other species.

I am generally interested in how organisms, through the structure of their life cycle, ameliorate variability in population growth rate.  This is a theme in my own research and in a working group on this topic through the National Center for Ecological Analysis and Synthesis (NCEAS) at Santa Barbara.

In collaboration with Tim Wootton, Dick Hudson, and our postdoc Handojo Kusumo, we are exploring how genetic and demographic factors affect the persistence of the sea palm, Postelsia palmaeformis. We are using microsatellite markers to understand dispersal distances and parentage in the sea palm and looking at the fate of populations with differing genetic backgrounds.

This research is funded by the National Science Foundation, OCE #01-17801.

Although it is recognized that the upwelling of nitrogen-rich water is a source of productivity in the northeast Pacific, my experiments and observations are also revealing that animal excretion is a significant source of ammonium in coastal waters and tidepools. Algal productivity within tidepools is boosted several-fold by the presence of mussels and seawater in close proximity to Tatoosh Island has elevated ammonium levels compared with seawater away from the Island. An active area of research for me is the implications of animal nutrient supply for microbe and algal populations.

My research program is centered on Tatoosh Island, Washington and surrounding sites where I have long-term data on the dynamics of nearshore fish recruitment and adult abundance. Sixteen years of annual censusing of an assemblage of tidepool sculpins reveals relative constancy in the numbers of recruits and adults.  However, the dominant species as a recruit (Clinocottus globiceps) was always replaced numerically as an adult by Oligocottus maculosus.  Based on previous experimental work demonstrating the competitive dominance of O. maculosus andthe presence of density-dependence, post-recruitment processes appear to play a very important role.  A competition-colonization trade-off among the two dominant species is suggested and may contribute to the coexistence of these species.

I am grateful to the Makah Tribal Nation for continued access to these sites. 

Funding has been provided by the National Science Foundation, the Andrew Mellon Foundation, the University of Chicago and the EPA (via the Center for Integrating Statistics and Environmental Science).