Meeting Abstract
Trait variation among populations often reflects differing selective optima, especially those that are expensive to express or maintain. Autotomy, the voluntary shedding of appendages, is a costly antipredator strategy with high degrees of variation among populations. Unlike classical inducible morphological defenses, the ability to autotomize doesn’t require energy to develop. Instead, the animal incurs the costs after the fact. In addition, an animal can only autotomize a limited number of times due to anatomical constraints. The cost-benefit dynamics behind the variation in autotomy therefore can be different from that of inducible defenses. Using tail autotomy in the side-blotched lizard Uta stansburiana, we first developed a model to understand how predation intensity, food availability and the frequency of male-male fighting jointly determined the variation in tail autotomy. Our model suggested that high predation intensity and moderate male-male fighting selected for higher propensity for autotomy. When fightings between males became more frequent, however, low propensity would be favored instead. Food availability, despite significantly affecting survival, did not change the joint effect of predation intensity and male-male fighting on the propensity for autotomy. Data from the field corroborated our model. Propensity for tail autotomy peaked at intermediate frequency of male-male fighting and exhibited a negative correlation with predation intensity in females. Our study provided a useful framework with which to study variation in autotomy from a cost-benefit perspective in other taxa, as well as to answer further questions such as the conditions favoring the evolution/maintenance of autotomy in nature.
