Department of Integrative Biology, UC Berkeley

How do variable environments drive the evolution of metabolic physiology in ectotherms?

This question drives much of our research, and we approach the problem at four overlapping levels:

  • How do genotype and phenotype interact to modulate nutrient flow through metabolic pathways?
  • How does variation in metabolic flux form the basis for life history traits that are then acted on by selection?
  • To what extent are organisms locally adapted in their metabolic physiology, and what drives that local adaptation?
  • Can we use this bio-energetic framework to predict the impacts of environmental change on ectotherm populations?

We use an integrative “genes to fitness” approach through the lens of intermediary metabolism and metabolic physiology to find the genes that influence overwintering energetics, from the level of naturally segregating variation within populations, through inter-population local adaptation, to interspecific divergence. This provides a novel framework for predicting ecological and evolutionary responses to winter climate change based on a mechanistic understanding of metabolic physiology. Addressing genotype – phenotype interactions through the lens of intermediary metabolism is advancing our understanding of the genetic control of complex, fitness-relevant traits.

Current active research areas

Physiological and genetic responses to winter environments

Winter climate change is altering energy balance, phenology, and cold stress in overwintering organisms leading to cascading biological impacts that carry over into the growing season and affect survival and fitness (Williams et al. 2014_Biol Rev). The ability to adapt or acclimate metabolic systems to compensate for changing winter conditions will strongly determine organismal responses to winter climate change. However, we know little about the mechanisms underlying metabolic plasticity in ectotherms, nor the evolutionary potential of metabolic systems on macro or micro scales. As climate change leads to the emergence of novel climates, we can no longer rely on bioclimatic envelope models to predict organismal responses to climate change; we need a mechanistic and predictive understanding that explicitly includes winter processes.

Metabolic basis of life history strategies

Nutrient allocation to physiological functions forms the basis of life history traits such as growth, reproduction and lifespan. We can understand trade-offs among these life history traits by studying differential allocations at the biochemical level (Zera and Harshman 2011), which can help us to link genotypic variation to whole organism phenotypes. This kind of functional approach is particularly powerful for traits that are controlled by many genes of small effect, such as processes intimately involved with central metabolism. We are addressing the role of these physiologically based life history trade-offs in mediating responses to variable environments.