Enemy at the gates: Rapid defensive trait diversification in an adaptive radiation of lizards

Abstract

Adaptive radiation (AR), the product of rapid diversification of an ancestral species into novel adaptive zones, has become pivotal in our understanding of biodiversity. Although it has widely been accepted that predators may drive the process of AR by creating ecological opportunity (e.g., enemy-free space), the role of predators as selective agents in defensive trait diversification remains controversial. Using phylogenetic comparative methods, we provide evidence for an "early burst" in the diversification of antipredator phenotypes in Cordylinae, a relatively small AR of morphologically diverse southern African lizards. The evolution of body armor appears to have been initially rapid, but slowed down over time, consistent with the ecological niche-filling model. We suggest that the observed "early burst" pattern could be attributed to shifts in vulnerability to different types of predators (i.e., aerial versus terrestrial) associated with thermal habitat partitioning. These results provide empirical evidence supporting the hypothesis that predators or the interaction therewith might be key components of ecological opportunity, although the way in which predators influence morphological diversification requires further study.

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“…Recent studies illustrate the potential of lCT technology for investigating skeletal and extraskeletal bone (e.g. Greenbaum et al 2012;Broeckhoven et al 2016a). The advantages of lCT, in addition to linear or other dimensional measurements that can be made to high degree of accuracy, include the following: (i) the entire structure can be analysed in virtual sections in any orientation, in contrast to traditional sectioning which cannot be adjusted; (ii) volumetric information can be determined such as the object volume or void space; and (iii) the 3D location of structures can be investigated.…”

“…Losos, Schoener & Spiller ; Broeckhoven et al . ). We illustrate the application of the proposed in vivo imaging protocol in a case study of skeletal and extraskeletal (i.e.…”

“…Reptiles and amphibians, especially lizards, have a long history of serving as model study organisms for an array of ecological and evolutionary studies (e.g. Losos, Schoener & Spiller 2004;Broeckhoven et al 2016a). We illustrate the application of the proposed in vivo imaging protocol in a case study of skeletal and extraskeletal (i.e.…”

Laboratory x-ray micro-computed tomography: a user guideline for biological samples

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Proximate causes of variation in dermal armour: insights from armadillo lizards

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