Convergent evolution in the Euarchontoglires

Abstract

Convergence—the independent evolution of similar phenotypes in distantly related clades—is a widespread and much-studied phenomenon. An often-cited, but hitherto untested, case of morphological convergence is that between the aye-aye and squirrels. The aye-aye (Daubentonia madagascariensis) is a highly unusual lemuriform primate that has evolved a dentition similar to that of rodents: it possesses large, ever-growing incisors which it uses to strip the bark from trees in order to feed on wood-boring beetle larvae. Indeed, such is the similarity that some of the earliest classifications of the aye-aye placed it in the squirrel genus Sciurus. Here, we aimed to test the degree of convergence between the skulls and lower jaws of squirrels and the aye-aye. Three-dimensional landmarks were recorded from the crania and mandibles of 46 taxa representing the majority of families in the Euarchontoglires. Results were plotted as phylomorphospaces and convergence measures were calculated. The convergence between squirrels and the aye-aye was shown to be statistically significant for both the cranium and mandible, although the mandibles seem to converge more closely in shape. The convergence may indicate strong functional drivers of morphology in these taxa, i.e. the use of the incisors to produce high bite forces during feeding. Overall, we have shown that this classic case of convergence stands up to quantitative analysis.

A phylogenomic rodent tree reveals the repeated evolution of masseter architectures

“…Diprotodonty, the spatial and functional separation of the incisors and cheek teeth, is another rostral morphotype that has evolved independently in multiple mammal clades (e.g. some marsupials, multituberculates, aye-ayes and rodents) [5]. In rodents, this arrangement allows engagement of either the incisors or the cheek teeth, but never both simultaneously.…”

Anatomical sciuromorphy in "protrogomorph" rodents

“…The cranial landmarks used here show that there is a great amount of shared shape variation among these rodents, despite their different masseter structures. Morris et al (2018) investigated convergences in cranial variation across Euarchontoglires, and their results reflect this finding in rodents. They found that the cranial variation within the squirrel-related clade of rodents, most of which are anatomically sciuromorphous (except for Aplodontia and glirids; see Figure 11 and Maier et al, 2002), overlapped with that of both mouse-related and ctenohystrican clades.…”

“…We made virtual reconstructions with Drishti v.2.6.4 (Limaye, 2012; Figure 4A) and identified 21 digital landmarks in 3D based on Morris et al (2018) from the right side of each cranium (Table 2; Figure 4B). Of the five Ischyromys typus specimens, only USNM 16828 preserved the structures required for the landmarking.…”

3D Geometric Morphometrics Reveals Convergent Character Displacement in the Central European Contact Zone between Two Species of Hedgehogs (Genus Erinaceus)

“…This explanation is also consistent with convergence in the mandible shape. As the function of the lower jaw connects mainly with feeding [ 47 , 52 ], in contrast to the cranium reflecting additional functions related to sensory organs and the brain [ 53 , 54 ], it is reasonable to ascribe respective patterns to evolutionary forces within the trophic niche. We hypothesize that decrease in size and convergence in shape is a result of local adaptations to overlapping dietary resources in the two species, and hence an example of convergent character displacement.…”