Evolution 2017: The Evolution of Anolis Adenovirus

We all wish anoles were invincible, but, sadly, they aren’t. Sofia Prado-Irwin’s poster at the Evolution 2017 meeting discussed one of anoles’ putative foes–the adenovirus. Adenoviruses infect a wide diversity of hosts, from amphibians to mammals, and though they are well characterized in captive and domesticated populations, we know very little about their evolution in the wild.

Sampling opportunistically from deceased animals in a breeding colony of Anolis sagrei as well as from one fecal sample, Prado-Irwin (Harvard University) was able to examine the prevalence of adenovirus in lizards caught on six different Bahamian islands. In particular, she was curious about three questions:

Was the mortality of animals in the breeding colony associated with adenovirus?
Is adenovirus present in anoles in the wild?
Does adenovirus coevolve with its hosts? In other words, does the phylogeny of A. sagrei from these 6 islands match the phylogeny of those animals’ viruses? Or perhaps, instead, the geographic distance between hosts’ islands explain how strains of adenovirus are related to one another?

Extracting genomic DNA and then amplifying virus-specific genomic regions, Prado-Irwin was able to show that adenovirus was certainly found in wild as well as lab-housed animals. However, mortality was unlikely to be due solely to the virus–only 23% of the deceased animals were infected. Finally, there was no evidence for for the adenovirus phylogeny matching either the lizard hosts’ phylogeny or tracking their geographic distribution. Instead, adenoviruses seem to shift hosts readily, with some A. sagrei adenovirus protein sequences being more closely related to mammalian adenovirus strains than to other anole strains! In a nutshell, virus evolution is complicated, and much remains to be learned about these submicroscopic maybe-destroyers of our favourite lizards.