The impact of body size on organismal biology continues to fascinate biologists, particularly when considering miniaturized animals at the smallest extremes. Geckos of the genus Sphaerodactylus are characterized by their diminutive size, species richness, and the diverse habitats they occupy across the Caribbean. First, I contextualized Sphaerodactylus within the squamate phylogeny, demonstrating the repeated evolution of miniaturization across 11 families, corroborating brain size as a limiting factor for body size (along with a relative increase in telencephalic volume), and revealing an ecological shift to terrestrial microhabitats [Chapter 1]. These findings were used as a springboard to evaluate the potential consequences of miniaturization in Sphaerodactylus with respect to activity patterns, thermal physiology, and social behavior. 

Under natural conditions, I implemented a vibrational monitoring system to characterize activity patterns across leaf litter strata in S. grandisquamis and S. townsendi. Vibrational data revealed that Sphaerodactylus exploit their niche in a three-dimensional manner, a pattern thus far underappreciated, and that behavior is used as a mechanism to buffer climatic changes in xeric habitats [Chapter 2]. Physiological traits are expected to evolve to favor homeostasis under a species’ preferred habitat conditions, regardless of body size. Nevertheless, few studies have evaluated whether miniaturization constrains physiological adaptations to climatic conditions. I measured standard metabolic rate (SMR) and evaporative water loss (EWL) via open-flow respirometry in five Sphaerodactylus species from three distinct habitat types. Physiological traits exhibited divergence mediated by habitat type and sympatry. Submontane S. klauberi showed the highest mass-corrected SMR and EWL, indicating susceptibility to thermal stress and desiccation, whereas xeric species exhibited the lowest SMR and shared low EWL with mesic S. grandisquamis. In sympatry, S. roosevelti had lower SMR and EWL than S. nicholsi, indicating physiology may underlie differences in thermal niche as an axis of niche partitioning. Overall, interspecific differences show that the evolutionary potential of physiological traits was not limited by miniaturization in Sphaerodactylus [Chapter 3].

Lastly, I used S. grandisquamis to study social dynamics, further elucidating the behavioral ecology of a miniaturized leaf litter species. Specifically, I evaluated the possibility of social recognition and the effect of the social environment on individual behavior. Through behavioral assays, I introduced familiar individuals to their own groups and unfamiliar individuals to existing groups. Increased rates of exploratory and agonistic behaviors were performed by group members toward unfamiliar individuals, supporting recognition of familiarity. Furthermore, geckos from multi-male groups showed reduced rates of agonistic behaviors toward unfamiliar individuals in concert with increased intrasexual conflict within their groups. The degree of complexity in recognition and social dynamics in a putatively solitary, miniaturized species may be related to their ecology, prompting further examination of the conditions under which sociality can evolve [Chapter 4].

Select Publications

Lagorio AD, Fields M, Fortner J, Mackareth E, Perez-Martinez CA, McGechie F, Wilken A, Leal M, Ward CV, Middleton KM, Holliday CM. Computational Approaches and Observer Variation in the 3D Musculoskeletal Modeling of the Heads of Anolis. (2024). Integr Org Biol 6(1): obae009.

Storks L, Garcia J, Perez-Martinez CA, Leal M. Habitat complexity influences neuron number in six species of Puerto Rican Anolis. (2024). Biology Letters 20(2): 20230419.

Perez-Martinez CA, Goyes Vallejos J. Squeaks in the dark: vocalisations in the Claw-snouted blind snake, Anilios unguirostris (Peters, 1867). (2023). Herpetol Notes 16: 885-887.

Fleishman LJ, Leal M, Perez-Martinez CA. Can sensory drive explain the evolution of visual signal diversity in terrestrial species? A test with Anolis lizards. (2022). Am Nat 200(2): 236-249.

Perez-Martinez CA, Leal M. (2021). Lizards as models to study the ecological and neuroanatomical correlates of miniaturization. Behaviour 158(12-13): 1121-1168.

Doctoral Program Committee

• Dr. Manuel Leal, Chair
• Dr. Rex Cocroft
• Dr. Kevin Middleton
• Dr. Lauren Sullivan