BOBACK, S.M.*; GUYER, C.; Auburn University; Auburn University: A test of reproductive power in snakes

Reproductive power is a contentious concept among ecologists and the model has been heavily criticized on theoretical and empirical grounds. Despite these criticisms, this model has successfully predicted the modal (optimal) size in three large taxonomic groups and shape of the body size distribution in two of these three groups. Here, we test the reproductive power model on a group that differs from the endothermic groups (upon which the model was derived) in both physiology and shape of the body size distribution. We derived snake-specific constants for the model using allometric relationships of energy in clutches or litters and relative population productivity. The relationships used to derive these constants were surprisingly similar between snakes and endotherms. Using snake-specific constants, the model accurately predicted the modal size in the snake size distribution; maximum reproductive power is achieved for a snake that is 408 g. However the model predicted a right-skew rather the log-normal shape of the empirical size distribution for snakes. If the model is correct, then snake diversity is limited especially in the largest size classes. Possible explanations for this limitation include biomechanics of locomotion and energetic constraints on foraging for the large prey. We briefly discuss how the relationships used to derive constants could limit the predictive power of the model.