From micro to macroevolution: drivers of shape variation in an island radiation ofPodarcislizards*

Abstract

Phenotypictraits have been shown to evolve in response to variation in the environment. However, the evolutionary processes underlying the emergence of phenotypic diversity can typically only be understood at the population level. Consequently, how subtle phenotypic differences at the intraspecific level can give rise to larger-scale changes in performance and ecology remains poorly understood. We here tested for the covariation between ecology, bite force, jaw muscle architecture, and the three-dimensional shape of the cranium and mandible in 16 insular populations of the lizards Podarcis melisellensis and P. sicula. We then compared the patterns observed at the among-population level with those observed at the interspecific level. We found that three-dimensional head shape as well as jaw musculature evolve similarly under similar ecological circumstances. Depending on the type of food consumed or on the level of sexual competition, different muscle groups were more developed and appeared to underlie changes in cranium and mandible shape. Our findings show that the local selective regimes are primary drivers of phenotypic variation resulting in predictable patterns of form and function. Moreover, intraspecific patterns of variation were generally consistent with those at the interspecific level, suggesting that microevolutionary variation may translate into macroevolutionary patterns of ecomorphological diversity.

Digest: Macroevolutionary pattern from microevolutionary processes *

“…Their analyses of 16 populations of lizards from island and mainland sites revealed similar patterns of intraspecific and interspecific variations in head shape and jaw musculature in response to similar ecological conditions. This finding implicates the microevolutionary processes that influence intraspecific populations of Podarcis lizards (ecological pressures associated with diet) in dictating macroevolutionary patterns across the genus, and, by doing so, Taverne et al (2021) provide an empirical example of how adaptive landscapes transcend the gap between microevolution and macroevolution (Arnold et al 2001).…”

“…This finding implicates the microevolutionary processes that influence intraspecific populations of Podarcis lizards (ecological pressures associated with diet) in dictating macroevolutionary patterns across the genus, and, by doing so, Taverne et al. (2021) provide an empirical example of how adaptive landscapes transcend the gap between microevolution and macroevolution (Arnold et al. 2001).…”

“…Although they do not employ the language of adaptive landscapes explicitly, Taverne et al. (2021) reveal that two species of Podarcis lizards inhabit similar adaptive landscapes. Their analyses of 16 populations of lizards from island and mainland sites revealed similar patterns of intraspecific and interspecific variations in head shape and jaw musculature in response to similar ecological conditions.…”

“…Despite this, the theoretical underpinnings of the concept have been mostly neglected entirely or applied separately to intraspecific or interspecific data, with little effort to apply them to both simultaneously. Although they do not employ the language of adaptive landscapes explicitly, Taverne et al (2021) reveal that two species of Podarcis lizards inhabit similar adaptive landscapes. Their analyses of 16 populations of lizards from island and mainland sites revealed similar patterns of intraspecific and interspecific variations in head shape and jaw musculature in response to similar ecological conditions.…”

“…In addition, it is crucial to note that they do so by examining anatomical features with an incredible level of abstraction. By focusing on craniomandibular skeletal shape and muscular size, Taverne et al (2021) have made their study replicable for any researchers studying taxa within the subphylum Vertebrata and have created for themselves and others an opportunity to study evolutionary patterns and adaptive landscapes at multiple levels of hierarchical biological integration simultaneously.…”