Food Availability's Role in the reduction in body size associated with sandy substrate in Pelobates cultripes

Abstract

Body size is the most relevant trait with the greatest number of implications in an organism's life. Studying its variation is essential for understanding the evolution of many others morphological and physiological characteristics. Pelobates cultripes exhibit variation in body size, related to a geological transition from hercinic substrates to sandy ones in southwestern Spain. Here, we analyze if this variation can be explained by differences in the diversity and abundance of potential preys between the two environments. We found 443 potential prey species in the hercinic environment, identified in 11 orders and 3 classes, and 792 in the sandy environment identified in 7 orders and 2 classes. The diversity was significantly higher in the hercinic environment, while the dominance index was significantly higher in the sandy one. In both environments, Hymenoptera and Diptera were dominant, but Coleoptera exhibited greater dominance in the hercinic environment compared to the sandy one. In addition, the preys were on average significantly heavier in the hercinic environment than in the sandy one. This might suggest that the differences in observed body size in P. cultripes could be explained by differences in diversity of food available and energy consumption. However, we think it is necessary to increase the sample size in future studies of food availability between the two environments studied, as well as diversify the methods used in describing the diet of P. cultripes, to arrive at more robust conclusions.