SICB+ - Intraspecific cranial integration in Anolis carolinensis and Natrix helvetica mirrors squamate-wide macroevolutionary pattern Tharakan, S*; Shepherd, N; Felice, RN; Goswami, A; Gower, DJ; Stanley, EL; Watanabe, A; New York Institute of Technology, College of Osteopathic Medicine, Old Westbury, NY; University College London, London, UK; University College London, London, UK; Natural History Museum, London, UK; Natural History Museum, London, UK; Florida Museum of Natural History, Gainesville, FL; New York Institute of Technology, College of Osteopathic Medicine, Old Westbury, NY email@example.com
How do phenotypic associations intrinsic to an organism, such as developmental and mechanical processes, dictate phenotypic evolution through deep time? Modern analyses of modularity and integration provides a quantitative framework to study the covariation within and among anatomical structures. Comparisons of intraspecific and clade-wide patterns of phenotypic covariation could inform how population-level or microevolutionary trends ultimately direct macroevolutionary changes. However, most studies have focused on analyzing integration and modularity either at macroevolutionary or intraspecific levels, without a shared framework unifying these levels. Here, we investigate the intraspecific patterns of cranial integration in two squamate species: Anolis carolinensis (n=41) and Natrix helvetica (n=30). We analyze their cranial integration patterns using the same high-density 3-D geometric morphometric approach used in our prior squamate-wide evolutionary study. Our results indicate very similar intraspecific and interspecific cranial integration patterns, with slight differences between Anolis and Natrix. Anolis mirrors the integration pattern found across the paraphyletic ‘lizard’ taxa in the rostrum, dentary, and occiput. Natrix shows greater correlations among the occipital condyle, basioccipital, supra-exoccipital, and quadrate, with a modular rostrum. Despite these minor differences, both species largely follow their respective interspecific patterns in ‘lizards’ and snakes. Together, these results suggest that intraspecific patterns within ‘lizards’ and snakes correspond to the macroevolutionary trends in cranial integration. Hence, our study implies that the phenotypic associations that direct morphological variation within species extend into the micro- and macroevolutionary levels.