“Natural history constrains the macroevolution of foot morphology in European plethodontid salamanders”

Posted on

Dean C. Adams, Dana Korneisel, Morgan Young, and Annamaria Nistri

Biomechanical constraints from climbing behavior limit morphological evolution

At ecological timescales, it is well understood that alterations in environmental selection pressures can cause changes in phenotypic traits that enable organisms to survive in those habitats. However, how such changes affect the rate of evolution at larger scales across the tree of life is less well known. In a recent study, Adams and colleagues examined this question by quantifying rates of morphological evolution in a genus of European salamanders that display a unique natural history and behavior. Unlike most other plethodontid salamanders, European species of Hydromantes spend considerable time in caves, where they cling to the walls and ceilings. These animals also have considerable webbing on their hands and feet, which is thought to generate the suction required during climbing. Based on this unique natural history, the authors hypothesized that foot morphology is under strong selection due to the biomechanical constraints associated with climbing. If correct, this would result in a lower rate of evolution of foot traits when compared to other morphological traits not related to their climbing behavior. In addition, they posited that rates of evolution in foot morphology should be lower in Hydromantes than in other salamander lineages that do not climb extensively.

To test these predictions, the authors measured several morphological traits on the feet of salamanders in two genera, Hydromantes and Plethodon, and measured several other morphological body traits in Hydromantes that were not related to climbing behavior. In accord with their predictions, they found that foot morphological traits evolved at significantly lower rates than did other phenotypic traits in Hydromantes. Additionally, Hydromantes displayed a lower rate of foot morphology evolution when compared to a non-climbing genus, Plethodon. Together, these findings suggest that macroevolutionary trends of phenotypic diversification can be mediated by the unique behavioral responses in taxa related to particular attributes of their natural history at ecological timescales. Read the Article

Top left and top right, Hydromantes strinatii found in its native habitat. Bottom, Dean C. Adams in a Tuscan cave, having recently retrieved an adult Hydromantes italicus from the cave wall. (Photos courtesy of Federico Crovetto and © 2017 University of Chicago Press)