A test of Darwin's ‘lop‐eared’ rabbit hypothesis

Abstract

Integration of evolutionary and developmental biology has stimulated novel insights on the origins and maintenance of phenotypic variation. For instance, phenotypic accommodation predicts that trait covariance originates via a novel developmental input caused by genetic change in one trait, but not the other. Darwin provided a striking example of this process in the 'lop-eared' rabbit by demonstrating that artificial selection for long external ears induced variation in the external auditory meatus. Although this intriguing pattern has been interpreted as evidence of phenotypic accommodation, it is unclear whether it exists and, if it does, whether it is selectively maintained in nature. To address this concern, we examined trait covariance in natural woodrat populations that have likely undergone selection for long ears. We demonstrated a remarkably similar covariance pattern as in the 'lop-eared' rabbit, which was associated with climatic variables along a steep arid-to-moist longitudinal gradient. Thus, our results suggest that trait covariance is likely a correlated response to selection. We relate these findings to potential origins of trait covariance owing to altered developmental interactions, such as in phenotypic accommodation. Additional evidence is needed to clarify how phenotypic accommodation and correlated selection promote and maintain trait covariance in natural populations. Nonetheless, our study is the first to support a classic Darwinian example concerning domestication and natural selection.

Delayed trait development and the convergent evolution of shell kinesis in turtles

“…This key developmental process promotes novel phenotypic variants that may otherwise not arise in embryogenesis owing to developmental constraints related to size and bone ossification. Although these plastic properties of developing skeletal tissue were first described in the nineteenth century [101], how they facilitate macroevolutionary change has only been emphasized in recent decades [102][103][104][105][106]. Likewise, our study highlights that the genotypeto-phenotype translation is not always a one-to-one relationship, as it may often involve tinkering of intricately interrelated traits over the course of multiple life stages.…”

Lop-eared rabbits have more aural and dental problems than erect-eared rabbits: a rescue population study

“…Charles Darwin first noted how artificial selection for pendulous pinnae in rabbits was associated with altered skull morphology 12 . Cordero and Berns (2016) found supportive evidence of this in natural woodrat populations that have likely undergone selection for long ears, finding substantial covariance of ear length and shape of the neighbouring auditory meatus 13 . This means that the lop-eared phenotype could not just affect aural function directly, but also other aspects of cranial health, such as dental function.…”

The postembryonic transformation of the shell in emydine box turtles

“…Theory predicts that shifts in shape‐size trajectories often contribute to adaptive phenotypic variation (Alberch et al, ), which is often ascribed to correlated structural constraints of the vertebrate skeleton (Atchley & Hall, ; Cordero & Berns, ; Cornette, Tresset, & Herrel, ; Young & Badyaev, ). That differences in such trait–trait or tissue–tissue interactions underlie quantitative macroevolutionary change has been long recognized (de Beer, ; Gould, ; Huxley, ; Olson & Miller, ; Thompson, ).…”