I am deeply interested in the factors that promote the evolution and maintenance of novel locomotor behaviors at both a micro- and macroevolutionary scale. My research program integrates techniques and perspectives from evolutionary biology, functional morphology, biomechanics, behavior, and ecology to understand the causes and consequences of the evolution of functional novelty. I often use phylogenetic comparative methods, which, coupled with advances in collecting and analyzing morphological data, provide a powerful tool to understand adaptation and functional diversity. I also recognize a strong need to rigorously quantify behavior and to study organisms in natural settings, an approach that I apply in both single-species and comparative contexts.
Below, I provide further detail of some previous and ongoing projects.
Muscles spanning multiple joints play important functional roles in a huge diversity of systems across tetrapod vertebrates, including human fingers, bird necks, and chameleon and primate tails. Despite the ubiquity and importance of multiarticular muscle systems, we still lack data on fundamental aspects of their function. Snakes can serve as excellent study organisms for advancing this topic. Their trunk muscles span from one or a few vertebrae to upwards of 30; moreover, muscle architecture varies among muscles and among species. Snakes rely on their axial musculoskeletal system for a huge range of activities, including striking, constriction, defensive displays, and locomotion.
My postdoctoral work is currently concerned with understanding the function of multiarticular snake muscles, funded by PI Henry Astley’s NSF CAREER grant (award #2045581). As part of this grant, we are using diceCT scans to characterize muscle anatomy and then calculating the contributions of each muscle to bending in different planes. We are also beginning a project that will involve using fluoromicrometry to measure muscle length changes during locomotion in living snakes. Stay tuned!
Biomechanics of locomotion
Biomechanical quantification coupled with rigorous statistical analysis provides an avenue for better understanding both the proximate and ultimate causes of a given behavior (i.e., its relationship with lower-level traits such as morphology and physiology, as well as ecology and evolution). So far, much of my work in this area has focused on an unusual type of movement called sidewinding, best known in a handful of sand-dwelling viper species. During sidewinding, a snake alternately holds some sections of its body stationary on the ground while lifting other sections up and forward in loops, eventually anchoring them to new stationary points farther along. Sidewinding is closely associated with shifting or smooth surfaces, especially sand. It is not an ancestral locomotor mode, and many snakes cannot perform sidewinding even under duress; yet, several species are highly specialized in sidewinding, and many other species sidewind facultatively with varying degrees of proficiency. I wrote a review on sidewinding locomotion for a 2020 SICB symposium; check it out if you’re interested in learning more [Tingle 2020].
Much of my work in this area has involved kinematics, a way of describing motion in terms of the changes in spatial relationships among parts, as well as quantifying various aspects of morphology so that I can link morphological and kinematic variation. For example, in one previous study I measured morphological traits of sidewinder rattlesnakes and extracted several kinematics variables from high-speed videos of the snakes, then used ANCOVA and RMA to examine sources of individual variation and scaling, and path analysis to test hypothesized causal relationships and correlations among morphological, kinematic, and performance variables [Tingle et al. 2022].
In the future, I plan to continue using these techniques, plus techniques such as computer vision and accelerometry learned during my postdoc. I have also established collaborations with scientists who have expertise in physics and robotics, which complement my own biological expertise and will allow new ways to approach locomotor studies.
Evolution of behavior and morphology
I often use phylogenetic comparative methods to test ecomorphological hypotheses. Some of my previous work has uncovered evidence for morphological adaptation in snake species specialized for particular habitats or locomotor modes (Tingle et al. 2017; Tingle and Garland 2021; Rieser et al. 2021). My work will remain concerned with understanding patterns of biological diversity across the tree of life. In addition to macroevolutionary studies, I have numerous ideas for projects focused on evolution within species or populations.
I started my career as a field biologist (Tingle 2012; Tingle et al. 2016), and my love of field work has led me to continue finding ways to study organisms in their natural environments. Biomechanics is historically a lab-based discipline, focusing primarily on organisms’ behavior under highly controlled conditions. However, technological advances are making it increasingly feasible to bring biomechanics techniques in the field. For some my future work, I plan to link biomechanics firmly with ecology by studying locomotor behavior in free-living animals. Combined with data collected under controlled conditions, data from free-living animals can help us understand how locomotor performance—mediated by underlying morphological and physiological traits—affects aspects of ecology, such as habitat use and activity patterns.