title: Mating systems, reproductive success, and sexual selection in secretive species: a case study of the western diamond-backed rattlesnake, Crotalus atrox.
abstract: Long-term studies of individual animals in nature contribute disproportionately to our understanding of the principles of ecology and evolution. Such field studies can benefit greatly from integrating the methods of molecular genetics with traditional approaches. Even though molecular genetic tools are particularly valuable for species that are difficult to observe directly, they have not been widely adopted. Here, we used molecular genetic techniques in a 10-year radio-telemetric investigation of the western diamond-backed rattlesnake (Crotalus atrox) for an analysis of its mating system and to measure sexual selection. Specifically, we used microsatellite markers to genotype 299 individuals, including neonates from litters of focal females to ascertain parentage using full-pedigree likelihood methods. We detected high levels of multiple paternity within litters, yet found little concordance between paternity and observations of courtship and mating behavior. Larger males did not father significantly more offspring, but we found evidence for size-specific male-mating strategies, with larger males guarding females for longer periods in the mating seasons. Moreover, the spatial proximity of males to mothers was significantly associated with reproductive success. Overall, our field observations alone would have been insufficient to quantitatively measure the mating system of this population of C. atrox, and we thus urge more widespread adoption of molecular tools by field researchers studying the mating systems and sexual selection of snakes and other secretive taxa.
authors.affiliation: Department of Biology, San Diego State University, San Diego, California, United States of America.
authors.forename: Rulon W
authors.initials: RW
authors.lastname: Clark
authors.affiliation: Department of Biology and Center for Behavioral Neuroscience, Georgia State University, Atlanta, Georgia, United States of America; The Copperhead Institute, Spartanburg, South Carolina, United States of America; Chiricahua Desert Museum, Rodeo, New Mexico, United States of America.
authors.forename: Gordon W
authors.initials: GW
authors.lastname: Schuett
authors.affiliation: National Optical Astronomy Observatory, Tucson, Arizona, United States of America.
authors.forename: Roger A
authors.initials: RA
authors.lastname: Repp
authors.affiliation: Social Snakes, Tucson, Arizona, United States of America.
authors.forename: Melissa
authors.initials: M
authors.lastname: Amarello
authors.affiliation: The Copperhead Institute, Spartanburg, South Carolina, United States of America; Chiricahua Desert Museum, Rodeo, New Mexico, United States of America; Department of Biology, Wofford College, Spartanburg, South Carolina, United States of America.
authors.forename: Charles F
authors.initials: CF
authors.lastname: Smith
authors.affiliation: School of Natural Resources and the Environment, University of Arizona, Tucson, Arizona, United States of America.
authors.forename: Hans-Werner
authors.initials: HW
authors.lastname: Herrmann
mesh_terms: D063147:Animal Distribution; D000818:Animals; D049628:Body Size; D017839:Crotalus / Q000033:anatomy & histology / Q000235:genetics* / Q000502:physiology; D005260:Female; D008297:Male; D018895:Microsatellite Repeats; D012098:Reproduction; D012727:Sex Characteristics; D012726:Sexual Behavior, Animal