Updated: December 2012
Note: I will be on leave in Spring 2013 and will not be taking any new research students for Summer 2013.
I am interested in behavioral ecology, evolution and physiology. Most of my work addresses questions concerning the current function of reproductive behavior and animal communication signals, though I am also interested in asking questions about the underlying regulation of these things. I ask whether a given behavior or signal provides honest information about the “sender” to potential “receivers” (e.g., conspecifics, predators, etc.), how its production affects the behavior of receivers, and how it benefits the sender. This work is placed in the context of natural and sexual selection theory. In studies of underlying regulatory mechanisms, I am interested in examining how hormones act early in development and during adulthood to result in the expression of a behavioral or ornamental trait, which pigments are required for ornament expression, and interactions among these various mechanisms.
Below, I outline some active areas of research that would benefit from student assistance. My work combines field and laboratory study, and I enjoy working with students in both of these contexts. Please come talk to me if any of my research areas interest you. I also am happy to talk to you about your own project ideas! Although I currently work with lizards, I have experience with and interest in other taxa.
A major question in evolutionary biology concerns the manner with which sexual selection pressures, such as female choice and male-male competition, result in the origination and maintenance of elaborate male traits (or “ornaments”). The selective forces influencing the evolution of female ornaments have been relatively ignored even though the occurrence of such traits is not as uncommon as traditionally assumed. Among lizards, for example, females of over 30 species express bright coloration that is absent in conspecific males.
1) I examine the function and regulation of female ornaments, focusing on a species with conventional sex roles, the striped plateau lizard (Sceloporus virgatus). Female striped plateau lizards develop orange color on their throats during the reproductive season. My working hypothesis is that males prefer to court females that express more orange color because these females are of higher quality and thus produce higher quality offspring. Females are expected to benefit from “indirect mate choice” – attracting males to them, inciting competition, and mating with higher quality winners, all while remaining sedentary during the energetically expensive period of egg development. To address this hypothesis, my primary research questions are:
- How does female ornamentation influence male behavior?
- Does female ornamentation serve as an honest advertisement of female phenotypic quality?
- Can female ornamentation be used to predict characteristics of her offspring?
- What mechanisms (genetic or nongenetic) underlie the positive relationship between maternal ornamentation and offspring quality?
- How is female ornament expression regulated?
2) My students and I have recently expanded our work on female signals to include chemical signals. We have found that male response to female chemical cues is affected by the size of the female that provided the cue. This is exciting because it suggests that females may signal their size without being present! What other phenotypic information might be contained within these chemical cues?! To examine this, we are currently making progress in determining the chemical make-up of these signals (via GC/MS with assistance from colleagues in the Chemistry Department) and hope to relate variation in chemical composition to female phenotype. In the long run, we want to address many of the same 5 questions bulleted above in regards to these chemical signals. In addition, we want to assess whether the visual and chemical signals are redundant (i.e., provide the same information) or are instead providing distinct information to receivers.
3) I am also collaborating with Mark Martin to examine the cloacal microbial communities of my lizards. We have discovered that male and female lizards house significantly different microbiota and we are very interested in determining how such sex differences are produced and maintained. Most of this work is conducted in Mark’s lab on samples collected from my field site. Eventually, I would love to determine whether the microbes influence the production of female chemical cues!
Some other areas that my students and I have dabbled in include…
1) Population response to fire. In 2011, a fire burned through my study site. Since then, we have been comparing lizard and prey populations on the burned site to those on a nearby unburned site. This work includes basic population ecology as well as stable isotope analyses conducted in collaboration with Kena Fox-Dobbs (Geology Department).
2) Factors that influence sprint speed in lizards. Some variables that have been examined include: acute vs chronic elevations of corticosterone, incline of the race track, tail loss, and heritability.
3) Role of corticosterone in stimulating hatching of late-term lizard embryos.
4) Effect of developmental stress on larval development of tobacco hornworms.
Fritzsche*, A.K. and S.L. Weiss. 2012. Effect of signaler body size on the response of male striped plateau lizards (Sceloporus virgatus) to conspecific chemical cues. Journal of Herpetology 46:79-84. (*UPS student coauthor)
Weiss S. L., K. Foerster, and J. Hudon. 2012. Pteridine, not carotenoid, pigments underlie the female-specific orange ornament of striped plateau lizards (Sceloporus virgatus). Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Physiology 161:117-123.
Weiss, S. L., E. A. Kennedy*, R. J. Safran and K. J. McGraw. 2011. Female ornamentation predicts yolk antioxidant levels in striped plateau lizards (Sceloporus virgatus). Journal of Animal Ecology 80:519-527. (*UPS student coauthor)
Martin, M.O., F.R. Gilman*, and S.L. Weiss. 2010. Sex specific asymmetry within the cloacal microbiota of the striped plateau lizard, Sceloporus virgatus. Symbiosis 51:97-105. (*UPS student coauthor)
Weiss, S.L., E.A. Kennedy*, and J.A. Bernhard. 2009. Female-specific ornamentation predicts offspring quality in striped plateau lizards, Sceloporus virgatus. Behavioral Ecology. (*UPS student coauthor) http://beheco.oxfordjournals.org/cgi/reprint/arp098?ijkey=oAwz3TmPYJkr89z&keytype=ref
Kabelik D., S.L. Weiss, and M.C. Moore. 2008. Arginine vasotocin (AVT) immunoreactivity relates to testosterone but not territorial aggression in the tree lizard, Urosaurus ornatus. Brain, Behavior and Evolution 72:283-294.
Kabelik D., S.L. Weiss, and M.C. Moore. 2008. Steroid hormones alter neuroanatomy and aggression independently in the tree lizard. Physiology and Behavior 93(2008):492-501.
Strand, C., M.S. Ross, S.L. Weiss, and D. Deviche. 2008. Testosterone and social context affect singing behavior but not song control region volumes in adult male songbirds in the fall. Behavioural Processes 78(2008):29-37.
Weiss, S.L., G. Johnston, and M.C. Moore. 2007. Corticosterone stimulates hatching of late-term tree lizard embryos. Comparative Biochemistry and Physiology A 146(3):360-365.
Kabelik D., S.L. Weiss, and M.C. Moore. 2006. Steroid hormone mediation of limbic brain plasticity and aggression in free-living tree lizards, Urosaurus ornatus. Hormones and Behavior 49(5):587-597. (Invited commentary by editorial board member Juli Wade accompanied publication: Hormones and Behavior 49(5): 577-579.)
Weiss, S.L. 2006. Female-specific color is a signal of quality in the striped plateau lizard (Sceloporus virgatus). Behavioral Ecology 17(5):726-732.
Weiss, S.L. 2005. Response of conspecifics to reproductive color of female striped plateau lizards, Sceloporus virgatus. Journal of Negative Results 2:10-19.
Weiss, S.L. and M.C. Moore. 2004. Activation of aggressive behavior by progesterone and testosterone in male tree lizards, Urosaurus ornatus. General and Comparative Endocrinology 136(2):282-288.
Weiss, S.L. 2002. Reproductive signals of female lizards: pattern of trait expression and male response. Ethology 108(9):793-813.
Weiss, S.L., D.H. Jennings, and M.C. Moore. 2002. Effect of captivity in semi-natural enclosures on the reproductive endocrinology of female lizards. General and Comparative Endocrinology 128(3):238-246.
Weiss S.L. 2001. The effect of reproduction on food intake of a sit-and-wait foraging lizard, Sceloporus virgatus. Herpetologica 57(2):138-146.
Lee E.A., S.L. Weiss, M. Lam, R. Torres, and J. Diamond. 1998. A method for assaying intestinal brush border sucrase in an intact intestinal preparation. Proceedings of the National Academy of Science 95(5):2111-2116.
Weiss S.L., E.A. Lee, and J. Diamond. 1998. Evolutionary matches of enzyme and transporter capacities to dietary substrate loads in the intestinal brush border. Proceedings of the National Academy of Science 95(5):2117-2121.
Note: Much of my field work is conducted May – July at the American Museum of Natural History’s Southwestern Research Station (SWRS) in Portal, AZ. There is a vibrant population of senior scientists and young biologists (i.e., students like you) from around the world working at this station every summer, which makes it an exciting and fun place to work. It is also a beautiful and ecologically diverse location. I highly recommend the station to students interested in field research, whether or not you go there to work with me. If you are itching for some general field experience, check out the station and their volunteer program at http://research.amnh.org/swrs/, and come talk to me about opportunities there.