RESEARCH

My research addresses two broad and interrelated questions: 1) What makes species and populations vulnerable to anthropogenic global change? and 2) How do organisms evolve in response to climatic variation? I investigate these questions across a range of spatial and temporal scales while applying a variety of approaches, including organismal and molecular physiology, behavior, field ecology, and experimental biology. Details about some specific projects are below. 


THERMAL ECOLOGY AND THE EVOLUTION OF ANIMAL COLORATION

Two southwestern fence lizards (Sceloporus cowlesi) photographed on dark substrate. The top animal is from the white sands desert. The bottom animal is from adjacent dark substrate. 

Two southwestern fence lizards (Sceloporus cowlesi) photographed on dark substrate. The top animal is from the white sands desert. The bottom animal is from adjacent dark substrate. 

Animal coloration is usually investigated with respect to communication and predator avoidance. However, coloration can also influence animal temperature, with subsequent effects on temperature-dependent physiology, behavior, and ecology.  In my current postdoc, I am studying the thermal effects of color evolution for three species of lizard in the White Sands Desert of New Mexico. All three species have independently evolved pale coloration on white sand relative to nearby conspecifics on dark substrate. I am addressing two main questions. First, because pale coloration and pale substrate should decrease temperatures, have pale animals on white soils also diverged in temperature-dependent physiology and behavior? Second, does pale coloration lead to ecological benefits in terms of activity and energetics under desert conditions? I am addressing these questions with a combination of field ecology, laboratory experiments, and mathematical modeling of thermal environments and energetics. I am also contributing to a collaborative project on the genomics of speciation in these lizards. 


Investigating the consequences of global change at the scale of the organism

The intertidal porcelain crab Petrolisthes cinctipes, native to the California coast.

Although anthropogenic warming is a global phenomenon, organisms experience it at a local level. Therefore, investigations of climate change vulnerability are likely to benefit from measurements of environmental conditions taken at the scale at which organisms experience them. I integrated temperature-dependent physiology with biophysical estimates of thermal microhabitats to demonstrate geographic variation in vulnerability to warming in the tropical lizard Anolis cristatellus (Gunderson & Leal 2012). For my first postdoc, I used conceptually similar approaches to understand climate change consequences in intertidal Porcelain crabs on the California coast while integrating interactions between congeneric competitors, with stress assessed and both whole-organism and molecular levels (e.g., Gunderson et al. 2017). 


physiological plasticity as a buffer from global warming

Acclimation in the heat tolerance of ectotherms does not fully compensate for rising temperatures. From Gunderson & Stillman 2015 Proc. Roy. Soc. B. 

Phenotypic plasticity (non-genetic change in traits) could be an important means by which organisms buffer themselves from climate change, but this depends greatly on how plastic organisms are and how variation in plasticity is distributed among taxa. During my postdoc, I conducted a meta-analysis to determine magnitudes of, and global patterns of variation in, cold and heat tolerance plasticity among ectotherms. One of the primary results was that ectotherms have relatively low plasticity in heat tolerance, and therefore plasticity may have limited potential to buffer ectotherms from global change (Gunderson & Stillman 2015). In a follow-up analysis, we have calculated the degree to which tolerance plasticity reduces overheating probabilities for terrestrial ectotherm taxa based on measurements of natural thermal variability in their environments (Gunderson, Dillon & Stillman 2017).     


Functional Analyses of Climatic Niche evolution During adaptive radiation

The Puerto Rican yellow-chinned anole (Anolis gundlachi) has low heat tolerance relative to most other Puerto Rican species. 

Adaptive radiation is a process that leads to the coexistence of multiple closely related but ecologically distinct species. Most textbook examples of animal adaptive radiations focus on the evolution of morphological traits, although physiological evolution can potentially be just as important. I am investigating how physiological evolution under different climatic regimes has contributed to the radiations of Caribbean Anolis lizards (Gunderson et al. 2011; Leal and Gunderson 2012). A key result so far is that, across Puerto Rico and Jamaica, divergence in thermal physiology has happened repeatedly and facilitates species coexistence (Gunderson, Mahler & Leal, under review; get preprint here). 


How temperature shapes The Behavior of ectotherms

A summary of thermal physiology and behavior in a lizard. Behavior is generally more temperature sensitive than physiology (Gunderson and Leal 2015 Am Nat & 2016 Ecology Letters).

Behavior plays a major role in the responses of animals to climatic conditions generally and global change specifically. I have conducted a number of studies on behavioral responses to temperature, including the potential for behavioral thermoregulation to buffer populations from warming (Gunderson and Leal 2012), field tests of models of temperature-dependent activity (Gunderson and Leal 2015), and the development of a framework for investigating the effects of temperature on behavior (Gunderson and Leal 2016). During my postdoc, I am investigating the ecological consequences of within-population variation in behavioral responses to temperature in intertidal porcelain crabs. 


Feather-degrading bacteria and avian coloration

Swabbing the feathers of an Eastern Bluebird (Sialia sialis) for bacteria.

Swabbing the feathers of an Eastern Bluebird (Sialia sialis) for bacteria.

For my Master’s degree I studied feather-degrading bacteria, microbes that live in the plumage of wild birds and can break down the keratin molecules that make up feathers (Gunderson 2008). One project focused on how feather-degrading bacteria influence the appearance of structural (non-pigmentary) plumage coloration in Eastern Bluebirds (Sialia sialis, Gunderson et al. 2009). Another project investigated whether or not feathers colored with melanin pigments are more resistant to bacterial damage than unpigmented (white) feathers (Gunderson et al. 2008).


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