Exophthalmus scalaris. Credit: symbiota4.acis.ufl.edu/scan
In their 2008 review “Are islands the end of the colonisation road?” Bellemain and Ricklefs (2008) concluded that oceanic islands could be important sources of colonisation of mainland continental areas and cited anoles of the Norops clade as a notable success. There are more than 5 times as many Norops clade species in Central and northern South America as in the West Indies; the 23 extant Caribbean species in the clade are distributed in Cuba and Jamaica with one species in Grand Cayman (Nicholson et al, 2005). Data in Nicholson et al (2005) gave support to the reverse colonisation hypothesis, but did not offer specific dating for the colonisation.
New analyses of 65 species in the Exophthalmus weevil genus complex (Zhang et al 2017) have turned up results that are of significance in understanding the biogeographic history of Caribbean anole dispersal and diversification. Like anoles of the Norops clade, the weevils show reverse colonization (island-to-continent), with diversification on the mainland and diversification within the islands. The data also give some support for overwater dispersal as the factor best explaining ancient between-island distribution.
Zhang et al’s best fit biogeographic model gives an estimate of 19Ma for a jump dispersal of Exophthalmus, most likely from Hispaniola, which went on to diversify into more than 40 species in Central America. So – did the anoles and the weevils make their journeys to the mainland around the same time and under similar conditions? Can this weevil study and the techniques it uses to arrive at its conclusions inform anole evolution and dispersal?
References
Bellemain, E and RE Ricklefs (2008) Are islands the end of the colonisation road? Trends Ecol Evol. 2008 Aug; 23(8):461-8. doi: 0.1016/j.tree.2008.05.001. Epub 2008 Jun 26. (Correction to citation numbering: Trends Ecol Evol. 2008 Oct; 23(10):536-7).
Nicholson, KE, RE Glor, JJ Kolbe, A Larson, S Blair Hedges, JB Losos (2005) Mainland colonization by island lizards. Journal of Biogeography 32 (6), 929-938.
Zhang, G, U Basharat, N Matzke, NM Franz (2017) Model selection in statistical historical biogeography of Neotropical insects—The Exophthalmus genus complex (Curculionidae: Entiminae). Molecular Phylogenetics and Evolution, 109, 226-239. DOI: 10.1016/j.ympev.2016.12.039.
Website:https://www.verdantisleorchids.org/
Skip Lazell
I bet the weevils beat the anoles by a few million years! Great story! Skip