My research explores how ecology drives organismal evolution by integraging theoretical modeling, lab experiments, and field data.

Heliconius melpomene rosina  (red and yellow) and  H. cydno chioneus  (black and white) feeding from the same plant.

Heliconius melpomene rosina (red and yellow) and H. cydno chioneus (black and white) feeding from the same plant.

Evolutionary Behavioral Ecology

My current project at the Merrill lab adds some evolutionary flavor to my existing research on behavioral ecology and performance. The focal systems are two species of Heliconius butterflies (H. cydno and H. melpomene). Wing patterns in Heliconius butterflies often involve Müllerian mimicry, in which multiple chemically defended species evolve similar warning color patterns (i.e. they belong to the same "mimic ring"). Moreover, the wing patterns in these butterflies also serve as cues for mate recognition and thus play a crucial role in facilitating speciation. H. cydno and H. melpomene, though closely related, possess distinct warning patterns, which limits the occurrence of hybridization when the two species come into contact. Previous work from the lab suggested that the preference for wing patterns has a strong genetic basis and that the genes for the preference and those for the wing patterns may lie in close proximity to one another in the genome. Using computer vision and machine learning, we are obtaining high-throughput data on male visual preference and use these data to help identify the gene(s) responsible for divergent male visual preference and, more broadly, examine the divergent evolution of mate preference in Heliconius butterflies. I am also using Heliconius butterflies as a system to examine the role of predator psychology in maintaining local Müllerian mimetic diversity.

Mark-recapturing lizards to estimate predation pressure in the deserts of western U.S.

Mark-recapturing lizards to estimate predation pressure in the deserts of western U.S.

Ecology of adaptive trait variation

One of my main research interests is understanding adaptive trait variation from an ecological, cost-benefit perspective. Traits that enhance fitness while simultaneously impose high costs are especially pertinent to this inquiry, as they are often under strong selection. I use autotomy (the voluntary shedding of body parts), one of the most extreme antipredator behavior within animals, as the study system to unravel how ecology drives the variation in autotomy through both natural and sexual selection. Autotomy, or the voluntary shedding of body parts, is an effective yet expensive antipredator strategy used in a diverse array of animals. From a proximal perspective, the occurrence of autotomy involves both relfex and central control, while the propensity with which organisms autotomize their body parts is ultimately regulated by the ecological environment. The complexity of autotomy therefore presents an excellent opportunity to study the evolution of extreme biological adaptations with a multi-disciplinary approach. 

Relevant publications:

Kuo C-Y and Irschick DJ. 2015. Ecology drives natural variation in an extreme antipredator trait: a cost-benefit analysis integrating modeling and field data. Functional Ecology 30: 953-963. pdf

Kuo C-Y, Irschick DJ, Lailvaux SP. 2014. Trait compensation between boldness and the propensity for tail autotomy under different food availabilities in similarly-aged brown anole lizards. Functional Ecology 29: 385-392. pdf

Gillis GB, Kuo C-Y, Irschick DJ. 2013. The impact of tail loss on stability during jumping in green anoles (Anolis carolinensis). Physiological and Biochemical Zoology 86: 680-689. pdf

A tokay gecko ( Gekko gecko ) clinging to a glass surface by engaging its adhesive toepads. Photo courtesy of Duncan Irschick.

A tokay gecko (Gekko gecko) clinging to a glass surface by engaging its adhesive toepads. Photo courtesy of Duncan Irschick.

Evo- & eco-morphology

The ecomorphoIogical paradigm, in its original form and its later expansions, has a deep influence on how I think about biological adaptations. I am interested in how the dynamics between morphology, performance and fitness might differ as a result of ecological contexts. I am also interested in situations where conflicts might arise within the morphology-performance-fitness pathway due to life-history events. A good example where ecology and performance may clash is the often substantial weight gain from a regular meal or from carrying developing offspring, as such weight gain can severely compromise the locomotor capacity of an individual. To alleviate such conflict, animal have evolved numerous behavioral and physiological mechanisms, some of which act to reduce the degree of performance impairment following weight gain, while others minimize the fitness impact under suboptimal performance. From a different perspective, I am also interested in the biomechanical underpinnings of whole-organism performance. Projects along this line included biomechanical analyses explaining how trap-jaw ants can close their mandibles with accelerations exceeding that of a bullet fired from a gun and evolutionary biomechanics of adhesion in animals. 

Relevant publications:

Imburgia MJ, Kuo C-Y, Briggs DR, Irschick DJ, Crosby AJ. In press. Effects of digit orientation on gecko adhesive force capacity: synthetic and behavioral studies. Integrative and Comparative Biology.

Ilton M, Bhamla S, Ma X, Cox S, Fitchett LL, Kim Y, Koh J-S, Krishnamurthy D, Kuo C-Y, Temel FZ, Crosby A, Prakash M, Sutton G, Wood R, Azizi E, Bergbreiter S, Patek S. 2018. The principles of cascading power limits in small, fast biological and engineered systems. Science 360: eaao1082. pdf

Labonte D, Clemente CJ, Dittrich A, Kuo C-Y, Crosby AJ, Irschick DJ, Federle W. 2016. Extreme allometry of animal adhesive pads and the size limits of adhesion-based climbing. PNAS 113: 1297-1302. pdf