New paper published
Authors Charles Smith, Gordon W. Schuett, and Melissa Amarello are pleased to report that their latest paper "Male mating success in a North American pitviper: influence of body size, testosterone, and spatial metrics" has been published in the scientific journal Biological Society of the Linnean Society. Below is the abstract from that paper. The authors would like to thank Steve Berube, Hank Gruner, Roger Gibson, and David Hardy, Sr., and Alex Bentley for their help, as well as Julie Victoria and Laurie Fortin from the Connecticut Department of Environmental Protection Wildlife Division for permits, telemetry equipment, and funds to purchase radio-transmitters, PIT tags, and other supplies. Funding for the research was provided by the American Wildlife Research Foundation, The Copperhead Institute, Georgia State University, The University of Connecticut Department of Ecology and Evolutionary Biology Wetzel Fund, the Connecticut Department of Environmental Protection Non-game Fund, Sigma Xi, Zoo Atlanta, and a NSF Predoctoral Fellowship to Dr. Smith. You can access a pdf of the paper here.
Males with enhanced traits relative to conspecifics often show increased mating and reproductive success and thus have a fitness advantage. The opportunity or potential for sexual selection is predicted to occur under these conditions. Here, we investigated proximate determinants of mating success in male copperhead snakes (Agkistrodon contortrix), a medium-sized pitviper of North America. Specifically, we investigated the relationships of body size (snout-vent length, body mass), body condition index, spatial metrics (total distance moved, home range size), and plasma testosterone concentration on mating success in males. The single mating season lasts from August through September. We compared a set of candidate linear mixed models and selected the best-fitting one using the adjusted Akaike information criterion (AICc). The AICc-selected model (model 2), with testosterone, body condition index, and home range size as predictor variables, showed that male mating success was positively correlated with testosterone. To our knowledge, this is the first report to show the relationship of testosterone and individual mating success in any snake species. A parallel study conducted on male fitness in A. contortrix of the same population used microsatellite markers to assign parentage of fathers (known mothers). Unlike our study, they found that snout-vent length was positively correlated with reproductive success and that males were experiencing greater sexual selection. This relationship has been detected under natural conditions in other species of snakes. Although behavioral data are important in any mating system analysis, they should not stand alone to infer parentage, relationships or selection metrics (e.g., Bateman gradients). Long-term sperm storage by females, female cryptic choice, and other factors contribute to the complexity of mating success of males. Accordingly, we thus conclude that estimates of reproductive success and fitness in cryptic species, such as copperheads and other snakes, require robust molecular methods to draw accurate conclusions regarding proximate and evolutionary responses.
Coauthor Melissa Amarello (right)