Ronald L. Rutowski
Vision, visual signals and reproductive behavior in insects
The integration of proximate and evolutionary explanations for visual signals and visually guided behavior in animal reproduction has been a theme of my research for many years. This effort has focused on butterfly behavior and coloration, which have been good subjects for fruitful investigation of how visual signals are produced and evolve, and how insects use vision in their lives. There are two major projects active at this time.
Mechanisms of color production and visual signaling in insects
A variety of mechanisms produce visual signals in animals, including pigments and physical structures that reflect colors by scattering and thin-film interference. For example, in sulphur butterflies, males have dorsal scales that produce orange-yellow coloration through interactions between pigments and scattering, but then also reflect ultraviolet (UV) light via thin-film interference.
The mechanism by which a color signal is produced may have consequences for how and why it is used in animal communication. First, because the UV reflection of male sulphurs is produced by a thin-film interference phenomenon, it is iridescent, which means that its aooearance changes dramatically as the position of the viewer changes. This suggests that in interactions in which the males UV reflectance is a signal, males should position themselves so they make their signal maximally apparent to an intended receiver. We are testing these ideas by studying the UV signal and its characteristics in detail and performing thorough behavioral studies of how males and females position themselves in communicatory interactions.
Second, if the mechanism by which a male's color is produced is costly, then it may provide females with information about a male's quality. In sulphur butterflies the complex structures on the wings responsible for the UV signal might be more costly to produce than the pigments that are responsible for the yellow-orange and black components of the male's coloration. We are testing this idea in behavioral experiments in which we determine which aspects of male coloration are most important to females in mate choice, and in experiments in which we manipulate the larval environment in which males develop to see how it affects the quality of the signals they ultimately produce. Such experiments are or soon will be underway.
Compound eyes, visual acuity and behavior in insects
We are also studying the acuity of insect vision and using that information to understand the interactions between vision and behavior in proximate and evolutionary time scales. How do compound eyes in insects constrain spatial resolution and object detection, and what affect does this have on their visually guided behavior? This work includes studies of the optics, morphology, and physiology of butterfly eyes done in collaboration with Dr. Eric Warrant at the University of Lund in Sweden. We are making inferences about the performance of the visual system based on optical and morphological measurements of the eyes. Then, in the field and lab, we try to test the accuracy of these inferences and examine the effects of additional variables such as temperature, female behavior, and background features on mate detection. Also, Dr. Warrant and I are testing hypotheses about the effects of body size and sex on visual field size and regional variation in acuity in butterflies. In the long run we hope that this research will reveal principles that inform the integration of proximate and evolutionary explanations of behavior and morphology.
In closing I would add that all components of my research require a thorough proximate and evolutionary understanding of the behavior of males and females in their search for mates and in sexual interactions. Understanding the sexual behavior of butterflies poses special questions and challenges because of the material benefits a female get from her mate contained in the spermatophore the male deposits in her reproductive tract during mating. For this reason sorting out the genetic and material benefits females and males accrue as a result of mating is an abiding issue in my lab.
Selected Publications
Kemp, D. J., P. Vukusic, and R. L. Rutowski. In press. Stress-mediated covariance between nano-structural architecture and ultraviolet butterfly coloration. Func. Ecol.
Merry, J., N. Morehouse, K. Yturralde, and R. L. Rutowski. 2006. Eyes of a patrolling butterfly: visual field and eye structure in the Orange Sulphur, Colias eurytheme (Lepidoptera, Pieridae). Journal of Insect Physiology 52(3): 240-248.
Kemp, D. J. R. L. Rutowski, and *M. Mendoza. 2005. Colour pattern evolution in butterflies: a phylogenetic analysis of structural ultraviolet and melanic markings in North American sulphurs. Evolutionary Ecology Research 7: 133-141.
Rutowski, R. L., J. M. Macedonia, N. Morehouse, L. Taylor-Taft. 2005. Pterin pigments amplify iridescent ultraviolet signal in males of the orange sulphur butterfly, Colias eurytheme. Proc. Royal Soc. B 272: 2329-2335.
Kemp, D. J., and R. L.Rutowski. 2004. A survival cost to mating in a polyandrous butterfly, Colias eurytheme. Oikos 105:65-70.
Orsetti, D., and R. L. Rutowski. 2003. No material benefits, and a fertilization cost, for multiple mating by female Colorado potato beetles (Leptinotarsa decemlineata). Animal Behavior 66: 477-484.
Rauser, C. L., and R. L. Rutowski. 2003. Male-specific scales on the wings of the Gulf Fritillary Butterfly, Agraulis vanillae (Lepidoptera: Nymphalidae): pheromone-disseminating structures? Journal of the Lepidopterists Society 57: 279-283.
Rutowski, R. L. 2003. Visual ecology of adult butterflies. In: C. L. Boggs, W. B. Watt, and P. R. Ehrlich (eds), Butterflies: Ecology and Evolution Taking Flight. University of Chicago Press, Chicago. Pgs. 9-25
Rutowski, R. L., and E. J. Warrant. 2002. Visual field structure in the Empress Leilia butterfly Asterocampa leilia (Lepidoptera, Nymphalidae): dimensions and regional variation in acuity. Journal of Comparative Physiology A 188: 1-12.
Rutowski, R. L., L. McCoy, and M. Demlong. 2001. Visual mate detection in a territorial male butterfly (Asterocampa leilia): Effects of distance and perch location. Behaviour 138: 31-43.
Drnevich, J., E. F. Hayes, and R. L. Rutowski. 2000. Sperm precedence, mating interval, and a novel mechanism of paternity bias in a beetle (Tenebrio molitor L.). Behav. Ecol. Sociobiol. 48: 447-451.
Ziemba, K., and R. L. Rutowski. 2000. Sexual dimorphism in eye morphology in a butterfly (Asterocampa leilia; Lepidoptera, Nymphalidae). Psyche 103: 25-36.
Rutowski, R. L. 2000. Postural changes accompany perch location changes in male butterflies, Asterocampa leilia, engaged in visual mate searching. Ethology 106: 453-466.
Rutowski, R. L. 2000. Eye size variation in butterflies: Intra- and interspecific patterns. J. Zoology 252: 187-195.
Wickman, P.-O., and R. L. Rutowski. 1999. The evolution of mating dispersion in insects. Oikos 84: 463-472.
Rutowski, R. L. 1998. Mating strategies in butterflies. Scientific American 279:64-69.
Rutowski, R. L. 1997. Sexual dimorphism, mating systems and ecology in butterflies. In: J.C. Choe and B.J. Crespi, eds. The Evolution of Mating Systems in Insects and Arachnids. Cambridge University Press, Cambridge.