Water constraints drive allometric patterns in the body shape of tree frogs

Abstract

The origin of morphological diversity is a critical question in evolutionary biology. Interactions between the environment and developmental processes have determining roles in morphological diversity, creating patterns through space and over time. Also, the shape of organisms tends to vary with increasing size as a result of those developmental processes, known as allometry. Several studies have demonstrated that the body sizes of anurans are associated with hydric conditions in their environments and that localities with high water stress tend to select for larger individuals. However, how environmental conditions alter those patterns of covariance between size and shape is still elusive. We used 3D geometric morphometric analyses, associated with phylogenetic comparative methods, to determine if the morphological variations and allometric patterns found in Arboranae (Anura) is linked to water conservation mechanisms. We found effects of the hydric stress on the shape of Arboranae species, favouring globular shapes. Also, the allometric patterns varied in intensity according to the water stress gradient, being particularly relevant for smaller frogs, and more intense in environments with higher water deficits. Our study provides empirical evidence that more spherical body shapes, especially among smaller species, reflect an important adaptation of anurans to water conservation in water-constrained environments.

Climate and Morphology Drive Breeding Periods in Frogs

“…Body size played an important role in determining how climate affects breeding periods. This is likely due to its effect on physiological processes such as regulating body temperature and water loss, where larger frogs are better at maintaining body temperatures and are slower to dessicate (Castro et al . 2021; Klein et al .…”

“…Body size played an important role in determining how climate affects breeding periods. This is likely due to its effect on physiological processes such as regulating body temperature and water loss, where larger frogs are better at maintaining body temperatures and are slower to dessicate (Castro et al 2021;Klein et al 2016;Santini et al 2018;Tracy et al 2010). The size-dependent effect of climate on anuran reproduction is most notable when comparing 1) temperate versus tropical environments, and 2) regions with high rainfall and limited propensity to hold water versus regions with low rainfall and high topographic water retention.…”

“…To test our hypotheses, we used phylogenetic multiple regression to examine the relationship of breeding period, all 7 principal components (PCs), and body size. To account for allometry of body size and since the natural logarithm of surface area-to-volume ratio is expected to scale linearly with the natural logarithm of body size (Castro et al . 2021; Klein et al .…”

“…To test our hypotheses, we used phylogenetic multiple regression to examine the relationship of breeding period, all 7 principal components (PCs), and body size. To account for allometry of body size and since the natural logarithm of surface area-to-volume ratio is expected to scale linearly with the natural logarithm of body size (Castro et al 2021;Klein et al 2016;Santini et al 2018), we used the natural logarithm of body size in our models. Additionally, we fit a phylogenetic ANCOVA model which included interactions between each PC and body size.…”

Assessment of Amphibians Vulnerability to Climate Change in China

“…Arboreal type species can better adapt to drier conditions through the variation of body shape (Castro et al, 2021). However, increasing temperature may easily impact body condition and decrease the survival of terrestrial/water type species, such as Bufo bufo (Reading, 2007), Xenopus laevis (Ruthsatz et al, 2018), and Rana cascadae (Kissel et al, 2019).…”