“The influence of climatic variability on morphological integration, evolutionary rates, and disparity in the Carnivora”
Andrew J. Conith, Molly A. Meagher, and Elizabeth R. Dumont (June 2018)
Current patterns of biodiversity are unevenly distributed spatially and temporally across the globe. Broadly speaking, biodiversity reaches its peak in tropical regions and decreases towards the poles. Dobzhansky, and later Fischer, first attempted to untangle the likely causes of latitudinal gradients in organismal biodiversity, and suggested seasonal and annual differences in climate could be important. Indeed, regions with the most variable climatic conditions typically contain habitats with the fewest niches, largest fluctuations in food availability, lowest primary productivity, and lowest species diversity. However, the extent to which climatic variability has influenced morphological evolution has yet to be tested. Understanding how climate affects the course of morphological evolution is vital to understanding current geographical variation in species distribution and modeling the potential for phenotypic responses to climatic change.
Here, Andrew J. Conith, Molly A. Meagher, and Elizabeth R. Dumont investigate whether climatic variability is associated with three different components of morphological evolution: phenotypic integration, the rate of morphological evolution, and disparity (morphological diversity). They extract climatic variability data from within species range maps, and gather landmark data from the jaws of three large families of carnivorans, Canidae, Felidae, and Mustelidae.
They find a negative relationship between climatic variability and phenotypic integration for canids and felids. For both clades, relatively variable climates were associated with low phenotypic integration. They also find a negative association between climatic variability and both disparity and rates of morphological evolution in canids and mustelids. Taken together, this suggests that those taxa in more variable regions (e.g., temperate, montane) may be more evolvable and thus more able to respond to fluctuating environmental conditions over time.
Biodiversity is unevenly distributed in space and time. One possible explanation is the influence of climate on the ecology, evolution, and morphology of taxa. Here we investigated the link between climatic variability and phenotypic integration, rates of morphological evolution, and disparity (morphological diversity) in three carnivoran clades (Canidae, Felidae, Mustelidae). We gathered landmark data from the lower jaw and extracted current temperature and precipitation data from range maps. We found a significant negative relationship between climatic variability and integration for canids and felids. Among canids variability in temperature was the key climatic variable, while in felids it was a combination of variability in temperature and precipitation. In both cases, relatively variable climates were associated with low phenotypic integration. We also found evidence for a negative association between climatic variability and both disparity and rates of morphological evolution in canids and mustelids. Selection can drive the evolution of jaw shape along lines of least resistance defined by patterns of integration, and this study suggests that climate may be a predictor of phenotypic integration. As a result, taxa in more variable regions (e.g., temperate, montane) may be more evolvable and more able to respond to fluctuating environmental conditions over a period of generations.