Convergent evolution of similar phenotypic features in similar environmental contexts has long been taken as evidence of adaptation. Nonetheless, recent conceptual and empirical developments in many fields have led to a proliferation of ideas about the relationship between convergence and adaptation. Despite criticism from some systematically minded biologists, I reaffirm that convergence in taxa occupying similar selective environments often is the result of natural selection. However, convergent evolution of a trait in a particular environment can occur for reasons other than selection on that trait in that environment, and species can respond to similar selective pressures by evolving nonconvergent adaptations. For these reasons, studies of convergence should be coupled with other methods—such as direct measurements of selection or investigations of the functional correlates of trait evolution—to test hypotheses of adaptation. The independent acquisition of similar phenotypes by the same genetic or developmental pathway has been suggested as evidence of constraints on adaptation, a view widely repeated as genomic studies have documented phenotypic convergence resulting from change in the same genes, sometimes even by the same mutation. Contrary to some claims, convergence by changes in the same genes is not necessarily evidence of constraint, but rather suggests hypotheses that can test the relative roles of constraint and selection in directing phenotypic evolution.

https://dash.harvard.edu/bitstream/handle/1/9938750/Losos_ConvergenceAdaptation.pdf?sequence=2

Convergence, adaptation, and constraint

Phylogeny of muroid rodents: relationships within and among major lineages as determined by IRBP gene sequences.

Living rodents show great diversity in their locomotor habits, including semiaquatic, arboreal, fossorial, ricochetal, and gliding species from multiple families. To assess the association between limb morphology and locomotor habits, the appendicular skeletons of 65 rodent genera from 16 families were measured. Ecomorphological analyses of various locomotor types revealed consistent differences in postcranial skeletal morphology that relate to functionally important traits. Behaviorally similar taxa showed convergent morphological characters, despite distinct evolutionary histories. Semiaquatic rodents displayed relatively robust bones, enlarged muscular attachments, short femora, and elongate hind feet. Arboreal rodents had relatively elongate humeri and digits, short olecranon processes of the ulnae, and equally proportioned fore and hind limbs. Fossorial rodents showed relatively robust bones, enlarged muscular attachments, short antebrachii and digits, elongate manual claws, and reduced hind limb elements. Ricochetal rodents displayed relatively proximal insertion of muscles, disproportionate limbs, elongate tibiae, and elongate hind feet. Gliding rodents had relatively elongate and gracile bones, short olecranon processes of the ulnae, and equally proportioned fore and hind limbs. The morphological differences observed here can readily be used to discriminate extant rodents with different locomotor strategies. This suggests that the method could be applied to extinct rodents, regardless of ancestry, to accurately infer their locomotor ecologies. When applied to an extinct group of rodents, we found two distinct ecomorphs represented in the beaver family (Castoridae), semiaquatic and semifossorial. There was also a progressive trend toward increased body size and increased aquatic specialization in the giant beaver lineage (Castoroidinae). J. Morphol., 2008. © 2008 Wiley-Liss, Inc.

Skeletal indicators of locomotor adaptations in living and extinct rodents

SIRT6 is Responsible for More Efficient DNA Double-Strand Break Repair in Long-Lived Species

Antioxidants do not explain the disparate longevity between mice and the longest-living rodent, the naked mole-rat.

SUBTERRANEAN rodents are intriguing subjects for research. On the one hand they display extreme variability in social organisation and life history, and exhibit a range of unique adaptations in morphology and physiology that allow exploitation of different habitats. On the other hand, field studies of subterranean rodents are exceptionally challenging as the animals are seldom observed. Subterranean rodents are also widely distributed, occurring on all continents except Australia and Antarctica. Life underground: The biology of subterranean rodents provides an excellent summary of what we know (and what we do not know) about this cryptic group of mammals, and also succeeds in conveying the joys and frustrations of studying them.

Guy N. Cameron

Papers

Life Underground: The Biology Of Subterranean Rodents