Use of molecular genetic tools in field studies of snakes and other ectotherms can be both an alternative and adjunct to direct observation, ,. Studies of individual behaviors and intraspecific interactions are less common than in other vertebrate groups, probably because acquiring such data through direct observation can be prohibitively time consuming. Most ecological studies on viperids, boids and pythonids have focused on population-level measures of movements, habitat use, survival, and demography. However, they are ideal for long-term, individual-based studies employing radio-telemetry, and their relatively high population densities permit the study of large numbers of individuals in relatively small areas. Yet, despite sedentary lifestyles, their generally secretive habits make most species difficult to observe directly in nature. They are important predators in many ecosystems and can occur in much higher densities than their endothermic counterparts. Large species of snakes, such as many viperids, boids and pythonids, are ecologically and economically important, but most are unstudied in nature. In sharp contrast, although Gibbs and Weatherhead highlighted the utility of molecular genetics to revolutionize our understanding of snake mating systems over a decade ago, only a handful of subsequent studies have used genetic tools in combination with field studies to provide detailed characterizations of sexual behavior and mating systems in wild snakes (see - ). For example, the mating systems of hundreds of avian species have been quantified and characterized using molecular genetic approaches. Despite the obvious benefits of this approach in addressing questions in behavioral ecology and evolution, molecular genetic tools have not been widely adopted for some taxa. Molecular genetics can be used to genotype individuals, measure relatedness, determine parentage, and unravel patterns of social structure and mating systems that would otherwise be extremely difficult to document. Hence, in our view, long-term studies on these taxa may disproportionately benefit from techniques that allow researchers to infer patterns of intraspecific interactions that are difficult or not possible to document by way of direct observation. These species often exhibit some combination of being small, cryptic, secretive, nocturnal, and sedentary. Consequently, a large number of terrestrial vertebrates remain severely understudied. This bias toward endotherms is most likely related to the fact that these species can be observed in nature more easily. For example, all of the studies cited in Clutton-Brock and Sheldon concern mammals and birds. However, such studies are few and there is a strong taxonomic bias. Despite logistical difficulties, long-term investigations are necessary to interpret the processes affecting survival and reproduction played out over the course of multiple years, or even decades. The long-term study of individual organisms in nature plays a central role in our understanding of ecology and evolution. 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. Overall, our field observations alone would have been insufficient to quantitatively measure the mating system of this population of C. Moreover, the spatial proximity of males to mothers was significantly associated with reproductive success. 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. We detected high levels of multiple paternity within litters, yet found little concordance between paternity and observations of courtship and mating behavior.
Specifically, we used microsatellite markers to genotype 299 individuals, including neonates from litters of focal females to ascertain parentage using full-pedigree likelihood methods. 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. Even though molecular genetic tools are particularly valuable for species that are difficult to observe directly, they have not been widely adopted. Such field studies can benefit greatly from integrating the methods of molecular genetics with traditional approaches. Long-term studies of individual animals in nature contribute disproportionately to our understanding of the principles of ecology and evolution.
0 kommentar(er)
