When it comes to adaptive radiations, the diversification of Anolis is one of the most striking examples. While Anolis is therefore a well-known rock stars in the league of adaptive radiations, in this blog post I would like to introduce you to one of the mere mortal examples; skinks from the genus Cryptoblepharus.
Cryptoblepharus skinks (“Cryptos”) are small diurnal lizards that have rapidly diversified and are known for their widespread distribution with species present in the Malagasy region, on the Australian continent and on many island archipelagoes in the Indo- and wider Pacific. Furthermore, species that occur on similar substrates are notoriously difficult to identify based on morphological characteristics and a more accurate estimate of species diversity has only recently been accomplished using a widespread genetic screen with allozyme markers (Horner & Adams, 2007).
Distribution of Australian Cryptoblepharus and the three habitat specialists. (a) Topographic map of Australia with the mean point of each species’
distribution plotted and coloured according to habitat type (for complete distribution maps, see Horner & Adams (2007)). In situ photographs of (b) arboreal, (c) littoral, and
(d) rock specialists (green, blue, and red dots on the topographic map, respectively).
Whereas species within the same habitat are highly cryptic, species that occur on different substrates (‘rock’, ‘trees’ or ‘beaches’) are relatively easy to distinguish. Rock Cryptos for example, traverse the red sandstone escarpments that are iconic for the Australian outback (think ‘Uluru like’ in terms of color and rock type) and they look very different from Cryptos that occur in a more mesic or coastal habitat. In a recent paper (Blom et al., 2016) we focused on the Australian radiation and explored whether habitat specialization explains current patterns of phenotypic variation in ecologically relevant traits. Using a comparative approach, we quantified the presence of distinct adaptive peaks, the frequency of shifts between such peaks and ultimately discuss the role of ecology in promoting continental radiation.