Jerry F. Husak Postdoctoral Researcher Virginia Tech

EDUCATION: B. S. Angelo State University; Ph.D. Oklahoma State University; Postdoc University of Massachusetts - Amherst

GENERAL RESEARCH INTERESTS: Evolutionary ecology, behavioral ecology, ecomorphology, sexual selection, herpetology

CURRENT RESEARCH: I am a postdoctoral researcher at Virginia Tech, working with Ignacio Moore, investigating the role of hormones in mediating how sexual signals advertise male performance. The functional capacities of structures used as weapons during male contests for access to females have been shown to be important determinants of male fitness. However, male territorial interactions do not always involve physical aggression involving the weapon. Instead, sexual signals may advertise weapon quality and capacity. Despite the empirical evidence to support the link between signal size and weapon quality, we know surprisingly little about the mechanisms that underlie this link. We study weapon performance (bite-force performance), signal size (dewlap size), and steroid hormone levels in a population of the green anole lizard (Anolis carolinensis), a species that exhibits strong sexual dimorphism and intense male competition for access to females. We are investigating whether testosterone mediates the connection between bite-force capacity and dewlap size in different size-classes of sexually mature males. So far we have discovered that the effects of testosterone work on performance and signals through body size, though the direction of causation is still being explored. However, among "heavyweight" green anoles, testosterone seems to be a good predictor of bite force. We are also investigating the influence of the stress hormone corticosterone on bite-force performance and dewlap size in males. Similar to morphs in tree lizards, we have found an inverse relationship between testosterone and corticosterone in smaller, subordinate males, but not in larger, dominant males. Hence, we are investigating whether there is an ontogenetic switch in testosterone responsiveness to elevated stress or whether there is selection on the response at some critical life stage (i.e., when males attain a competitive size). The ultimate goal is to determine how these sexually dimorphic traits increase reproductive success and whether there is a survival tradeoff for being a male with a big dewlap and high bite-force performance.

 

 

RESEARCH FOCUS: My on-going research program involves three main objectives to better understand the mechanisms and consequences of natural and sexual selection in nature.

(1) The role of "behavior" in the evolution of form and function: Recent work suggests that selection operates on whole-organism performance traits directly, with changes in underlying morphology occurring secondarily. While several studies have shown that better performers enjoy a survival advantage, few have considered how being a better performer gives such an advantage. Hence, I became interested in whether individuals use maximal performance in nature, and in what contexts. Essentially, I want to know whether morphology evolves via selection on the morphology per se, the functional capacity of the morphological traits, the realized behavior of the organisms, or some combination of these that is very species-, age-, or sex-specific? The latter possibility complicates things, but it makes the research exciting! Most of my work on this topic to date has been conducted on collared lizards. They represent a good system with which to address these issues, because their natural history makes morphology, performance, and behavior seem likely candidates as targets of natural and sexual selection. My work to date suggests that maximal performance is subject to natural selection, but only in some age classes, whereas the realized use of performance (= ecological performance or "behavior") is more important for others. Along with the ultimate implications involved with this general question, I am also interested in the proximate determinants of whole-animal performance and behavior that is constrained by performance capacity.

(2) Sexual selection on functional traits: How has male weapon morphology evolved? In addition to work centered at U Mass and VT, Kris Lappin (Cal Poly Pomona) and I are investigating population-level variation in bite-force performance, head morphology, and variance in male reproductive success in collared lizards. Interestingly, we have found that geographically-separated populations display very marked differences in their degree of sexual dimorphism in morphology and bite-force performance, with some populations displaying little dimorphism and aggression and others displaying strong dimorphism and high levels of aggression. The importance of biting ability in determining male mating success leads us to predict differing strengths of sexual selection on performance across the species' distribution. We are currently investigating this possibility, as well as how other selective forces are involved.

(3) Honest signals: Have conspicuous color signals evolved to advertise performance abilities? This is an interesting area of emerging research, because such signals could evolve through sexual selection or natural selection processes. From a natural selection standpoint, I am interested in whether signals displayed to predators actually reflect performance capacity and an increased probability of predator failure. This begs the question of whether predators assess such signals relative to their own performance capacities and respond accordingly. Sexual selection may favor signals that advertise performance to rivals during combat or to females during assessment of mates.

 

Supervising Stan Fox and Kris Lappin while photographing a Crotaphytus reticulatus in south Texas

OTHER ONGOING RESEARCH:

Behavioral ecology of the reticulate collared lizard (Crotaphytus reticulatus) in south Texas and the venerable collared lizard (Crotaphytus antiquus) in northern Mexico with Stan Fox (OSU).

Evolution of color patterns in crotaphytid lizards.

Sexual dimorphism in head size, the main weapon of fighting male lizards: male (upper) and female (lower) Crotaphytus collaris in Oklahoma

 

And when you get into a fight...

 

PUBLICATIONS:

(25) Husak, J. F., and S. F. Fox. 2008. Sexual selection on locomotor performance. Evolutionary Ecology Research 10:213-228. (e-mail me for a pdf, or go to EER website)

(24) Irschick, D. J., J. J. Meyers, J. F. Husak, and J. F. Le Galliard. 2008. How does selection operate on whole-organism functional performance capacities? A review and synthesis. Evolutionary Ecology Research 10:177-196. (e-mail me for a pdf, or go to EER website)

(23) Husak, J. F., S. F. Fox, and R. A. Van Den Bussche. 2008. Faster male lizards are better defenders not sneakers. Animal Behaviour 75:1725-1730. pdf

(22) Husak, J. F., D. J. Irschick, J. J. Meyers, S. P. Lailvaux, and I. T. Moore. 2007. Hormones, sexual signals, and performance of green anole lizards (Anolis carolinensis). Hormones and Behavior 52:360-367. pdf

(21) Irschick, D. J., J. K. Bailey, J. A. Schweitzer, J. F. Husak, and J. J. Meyers. 2007. New directions for studying selection in nature: studies of performance and communities. Physiological and Biochemical Zoology 80:557-567 pdf (Cover)

(20) Bergeron, C. M., J. F. Husak, J. M. Unrine, C. S. Romanek, and W. A. Hopkins. 2007. Influence of feeding ecology on blood mercury concentrations in four species of turtles. Environmental Toxicology and Chemistry 26:1733-1741. pdf

(19) Husak, J. F. 2006. Does survival depend on how fast you can run or how fast you do run? Functional Ecology 20:1080-1086. pdf (Erratum)

(18) Husak, J. F., M. B. Lovern, S. F. Fox, and R. A. Van Den Bussche. 2006. Faster lizards sire more offspring: sexual selection on whole-animal performance. Evolution 60:2122-2130. pdf (Highlighted in Outside JEB)

(17) Husak, J. F. 2006. Do female collared lizards change field use of maximal sprint speed capacity when gravid? Oecologia 150:339-343. pdf

(16) Husak, J. F., and S. F. Fox. 2006. Field use of sprint speed by collared lizards (Crotaphytus collaris): compensation and sexual selection. Evolution 60:1888-1895. pdf

(15) Lappin, A. K., Y. Brandt, J. F. Husak, J. M. Macedonia, and D. J. Kemp. 2006. Gaping displays reveal and amplify a mechanically-based index of weapon performance. American Naturalist 168: 100-113. pdf (Highlighted in Nature, Outside JEB, and ScienceShots)

(14) Husak, J. F., J. M. Macedonia, S. F. Fox, and R. C. Sauceda. 2006. Predation cost of conspicuous male coloration in collared lizards (Crotaphytus collaris): an experimental test using clay-covered model lizards. Ethology 112:572-580. pdf

(13) Husak, J. F. and M. N. Rouse. 2006. Population variation in escape behavior and limb morphology of collared lizards (Crotaphytus collaris) in Oklahoma. Herpetologica 62:156-163. pdf

(12) Husak, J. F. 2006. Does speed help you survive? A test with collared lizards of different ages. Functional Ecology 20:174-179. pdf

(11) Husak, J. F., A. K. Lappin, S. F. Fox, and J. A. Lemos-Espinal. 2006. Bite-force performance predicts dominance in male Venerable Collared Lizards (Crotaphytus antiquus). Copeia 2006:301-306. pdf

(10) Peterson, C. C., and J. F. Husak. 2006. Locomotor performance and sexual selection: individual variation in sprint speed of collared lizards (Crotaphytus collaris). Copeia 2006:216-224. pdf

(9) Lappin, A. K., and J. F. Husak. 2005. Weapon performance, not size, determines mating success and potential reproductive output in the collared lizard (Crotaphytus collaris). American Naturalist 166:426-436. pdf

(8) Macedonia, J. M., J. F. Husak, Y. M. Brandt, A. K. Lappin, and T. A. Baird. 2004. Sexual dichromatism and color conspicuousness in three populations of collared lizards (Crotaphytus collaris) from Oklahoma. Journal of Herpetology 38:340-354. pdf

(7) Husak, J. F. 2004. Signal use by collared lizards, Crotaphytus collaris: the effects of familiarity and threat. Behavioral Ecology and Sociobiology 55:602-607. pdf

(6) Husak, J. F., J. K. McCoy, S. F. Fox, and T. A. Baird. 2004. Is coloration of juvenile male collared lizards (Crotaphytus collaris) female mimicry?: an experimental test. Journal of Herpetology 38:156-160. pdf

(5) Husak, J.F. and S.F. Fox. 2003. Adult male collared lizards (Crotaphytus collaris) increase aggression towards displaced neighbours. Animal Behaviour 65:391-396. pdf

(4) Husak, J. F., and S. F. Fox. 2003. Spatial organization and the dear enemy phenomenon in adult female collared lizards, Crotaphytus collaris. Journal of Herpetology 37:211-215. pdf

(3) Husak, J. F., and E. N. Ackland. 2003. Foraging mode of the reticulate collared lizard, Crotaphytus reticulatus. Southwestern Naturalist 48:282-286. pdf

(2) Husak, M. S. and J. F. Husak. 2002. Low frequency of site fidelity by golden-fronted woodpeckers. Southwestern Naturalist 47:110-114.

(1) Husak, J. F. and J. K. McCoy. 2000. Diet composition of the collared lizard (Crotaphytus collaris) in west-central Texas. Texas Journal of Science 52:93-100.

 

Great Field Sites!

Glass Mountains, Oklahoma

North Bimini on the horizon

New Orleans swamp

 

E-mail: husak@vt.edu

VT Biology