What makes a great invader? Anatomical traits as predictors of locomotor performance and metabolic rate in an invasive frog

Abstract

ABSTRACT Invasive species are characterized by their ability to establish and spread in a new environment. In alien populations of anurans, dispersal and fitness-related traits such as endurance, burst performance and metabolism are key to their success. However, few studies have investigated inter-individual variation in these traits and more specifically have attempted to understand the drivers of variation in these traits. Associations of anatomical features may be excellent predictors of variation in performance and could be targets for selection or subject to trade-offs during invasions. In this study, we used marsh frogs (Pelophylax ridibundus), a species that has been introduced in many places outside its native range and which is now colonizing large areas of Western Europe. We first measured the inter-individual variation in resting metabolism, the time and distance they were able to jump until exhaustion, and their peak jump force, and then measured the mass of specific organs and lengths of body parts suspected to play a role in locomotion and metabolism. Among the 5000 bootstrap replicates on body size-corrected variables, our statistical models most often selected the stomach (75.42%), gonads (71.46%) and the kidneys (67.26%) as predictors of inter-individual variation in metabolism, and the gluteus maximus muscle (97.24%) mass was the most frequently selected predictor of jump force. However, endurance was poorly associated with the anatomical traits (R2distance=0.42, R2time=0.37). These findings suggest that selection on these predictors may lead to physiological changes that may affect the colonization, establishment and dispersal of these frogs.