Dominance of Anolis under Imminent Threat — from Geckos!

Cyrtodactylus peguensis from Wikimedia.

Anolis has long enjoyed being the most speciose genus of reptiles with currently 435 described species (unless you subscribe to the generic split crowd supporting Dactyloa and such, of course). There was not even a close contender. That is changing rapidly with the unabated description of new species of Cyrtodactylus — more than 300 new species since 2000 and more than 100 since 2020! The genus just crossed the magic threshold of 400 species (now 402, according to a forthcoming update of Reptile Database, Fig. 1). By comparison, only 90 new species of Anolis have been described since 2000 and a meager 9 since 2020. If the trend continues, there will be more Cyrtodactylus than anoles in a year or two.

Fig. 1. The number of Anolis and Cyrtodactylus described over time. See text for details.

Even the naive observer recognizes that anoles can be strikingly different, both in terms of size and color (dewlaps!), but also in terms of body shapes and even appendages . By contrast, Cyrtodactylus are rather uniform in overall body shape (even though quite variable in terms of color patterns). And while there has been an effort to establish something akin to ecomorphology in Anolis, the topic appears to remain in its infancy, despite various attempts to map phylogenies to habitat preferences, e.g. by Lee Grismer’s group (Fig. 2).

Fig. 2. Phylogeny 243 Cyrtodactylus species mapped to nine habitat preferences. From Grismer et al. (2020).

Admittedly, there are now a number of studies linking, for instance, toe pad morphology to these habitats, especially with Jenrian Riedel’s contributions (e.g. Riedel et al. 2024), but the molecular basis of all these adaptations remains woefully understudied.

What’s going on in both anoles and Cyrtodactylus in terms of evolution? Why have both managed to undergo such rapid radiations? The anolis community has at least started to address these questions by sequencing several genomes (to my knowledge, 10 Anolis genomes have been sequenced, at least at draft quality, namely Anolis apletophallus, Anolis auratus, Anolis carolinensis, Anolis frenatus, Anolis lemurinus, Anolis planiceps, Anolis rodriguezii, Anolis sagrei, Anolis sericeus, and Anolis tropidonotus, at least 5 of them by Colston et al. 2025). By contrast, I am not aware of a single Cyrtodactylus genome, but I may have missed those, of course (let me know in the comments if I did and where to find them).

The million-dollar question is: which mutations have led to all these adaptations and thus these rapid radiations? Or even to reproductive isolation, which is a separate but equally important issue, given that many species often occur sympatrically. We are only at the beginning of understanding these questions and the next generation of anologists (and geckologists!) have a lot of work to do to figure these things out.

References

Colston, T. J., S. Pirro, and R. A. Pyron. 2025 The Complete Genome Sequences of 101 Species of Reptiles. Biodiversity Genomes, https://doi.org/10.56179/001c.129597

Grismer, L. L., Wood Jr, P. L., Le, M. D., Quah, E. S., & Grismer, J. L. 2020 Evolution of habitat preference in 243 species of Bent‐toed geckos (Genus Cyrtodactylus Gray, 1827) with a discussion of karst habitat conservation. Ecology and Evolution, http://dx.doi.org/10.1002/ece3.6961

Riedel, J., Eisele, K., Gabelaia, M., Higham, T. E., Wu, J., Do, Q. H., Nguyen, T. Q., Meneses, C. G., Brown, R. M., Ziegler, T., Grismer, L. L., Russell, A. P., & Rödder, D. 2024 Ecologically-related variation of digit morphology in Cyrtodactylus (Gekkota, Squamata) reveals repeated origins of incipient adhesive toepads. Functional Ecology, 00, 1–19, https://doi.org/10.1111/1365-2435.14597