Most studies that describe anole locomotion are based on the analysis of kinematic and dynamic data. One of the challenges in biomechanics is to deduce from these data the interarticular forces and moments produced during locomotion. Indeed, evaluation of these dynamic data can inform us about the force production and absorption mechanisms that are crucial in movements for which the musculoskeletal system is in high demand, e.g. running, jumping or landing. These movements are essential in the fitness of individuals in arboreal environment during predator avoidance or prey attack and need to develop very high force levels by the musculoskeletal system, and especially by the hindlimbs during takeoff and forelimbs during landing.

To evaluate these dynamic constraints, the most usual procedure is to use a mathematical method called “inverse dynamics.” It consists in deducing the interarticular forces and moments for the knowledge of the ground reaction force, the linear and angular accelerations of the different segments, and their morphometric characteristics. However, there was no morphometric database to date in anoles.

That’s why we conducted a study to characterize the centers of gravity, moments of inertia, masses and lengths of major segments in Anolis carolinensis and Anolis sagrei (Legreneur et al., 2012). To do this, we had to develop and design specific instruments to measure the characteristics of segments of masses less than 0.1 g.

Results of this study and comparison between the two ecomorphs demonstrated a clear relationship between morphology and performance, particularly in the context of predator avoidance behavior, such as running or jumping in A. sagrei and crypsis in A. carolinensis. Our results provide new perspectives on the mechanism of adaptive radiation as the limbs of the two species appear to scale via linear factors and, therefore, may also provide explanations for the mechanism of evolutionary changes of structures within an ecological context.

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