How does intraspecific variation shape populations, communities, and ecosystems?

Ecologists have historically assumed that individuals within a population behave similarly, but there is now growing recognition of the important role that intraspecific variation plays in the viability of populations and in the functioning of communities and ecosystems. For example, individual diet variation influences how energy is transferred between habitats and intraspecific variation can have a stronger effect on functional diversity than interspecific variation.

I study how individual variation in demography and foraging ecology scales up to influence higher levels of biological organization. I've shown that the fishes of Lake Turkana, Kenya differ in intraspecific diet diversity and, consequently, their ability to adapt to ecosystem change. In Magellanic penguins, males show a greater flexibility in diet than females, and I found that this flexibility makes them more likely to survive when foraging conditions are unfavorable. Sex-specific survival in this species has led to increasingly male-biased sex ratios and population decline. I am currently studying variation in how growing chicks of this species allocate energy and how resulting differences in allometry relate to survival. I would like to expand on this work to study how variation in foraging behavior and demography influence the conservation of long-lived marine foragers.

What scales of environmental variation drive ecosystem function?

The issue of scale has challenged ecologists and oceanographers for decades. In the 1960’s, the physical oceanographer Henry Stommel published a diagram summarizing the various scales of oceanographic variability and their influence on plankton dynamics. The Stommel diagram has since become a widely used tool of ecologists, but the relative importance of different scales of variability on population, community, and ecosystem function are still poorly understood.

 

I am interested in conducting research that examines how environmental variability, rather than mean conditions, influences the foraging ecology and demography of marine organisms. In the past, I've examined these questions in the context of fish communities in African Lakes. I've shown that the food web structure of African Lakes, and characteristics such as ecosystem productivity and biodiversity, are linked to fluctuations in water level. This research is a deviation from how we generally consider lakes, as systems characterized by static conditions like depth. In Lake Turkana, Kenya, an understudied amplifier lake undergoing extreme hydrological change, I found that fisheries productivity is determined by water level fluctuations, not by mean water level or fishing effort. Questions relating to variability and scale are particularly important in a time of climate shifts and extremes. I plan to examine these questions in the context of long-lived marine organisms, using coupled demographic and environmental models to examine the spatial and temporal scales that drive their population dynamics.

How do we reach the full potential of MPAs as marine conservation tools?

The United Nations has declared 2021-2030 as the "Decade of Ocean Science for Sustainable Development". Ocean conservation was also explicitly included in the Sustainable Development Goals outlined by the United Nations in 2015. At the global scale, we are on track to reach a key target of the oceans goal, to protect 10% of the ocean by 2020. But reaching numerical targets has little conservation benefit unless marine protected areas are properly sited and managed.

I am currently conducting research that focuses on effective siting of MPAs. Specifically, I have collated spatial data from non-governmental and governmental organizations to identify regions that have consensus as a priority but that remain unprotected. In this research, I consider factors that will influence the effectiveness of the global MPA network, such as the size and biogeographic representativeness of potential new MPAs. I am also collaborating with a team of international marine conservationists to consider the role marine protected areas play in the global biodiversity agenda post-2020.