The Role of Geography and Ecological Opportunity in the Diversification of Day Geckos (Phelsuma)

Abstract

We examine the effects of ecological opportunity and geographic area on rates of species accumulation and morphological evolution following archipelago colonization in day geckos (genus Phelsuma) in the Indian Ocean. Using a newly generated molecular phylogeny for the genus, we present evidence that these geckos likely originated on Madagascar, whereas colonization of three archipelagos in the Indian Ocean, the Seychelles, Mascarene, and Comoros Islands has produced three independent monophyletic radiations. We find that rates of species accumulation are not elevated following colonization but are roughly equivalent on all three isolated archipelagos and on the larger island of Madagascar. However, rates of species accumulation have slowed through time on Madagascar. Rates of morphological evolution are higher in both the Mascarene and Seychelles archipelagos compared to rates on Madagascar. This negative relationship between rate of morphological evolution and island area suggests that ecological opportunity is an important factor in diversification of day gecko species.

Adaptive Radiation, Ecological Opportunity, and Evolutionary Determinism

“…In recent years, the results of phylogenetic analyses of clade diversification have also been taken as evidence: the commonly detected pattern of a burst of cladogenesis early in a clade's history is often interpreted as resulting from ecological opportunity, with lower rates later in history resulting from filling of niches (e.g., Weir 2006;McPeek 2008;Phillimore and Price 2008;Rabosky and Lovette 2008); high rates of morphological diversification early in a clade's history (Harmon et al 2003(Harmon et al , 2008Agrawal et al 2009;Burbrink and Pyron 2009) or when the number of lineages inferred to have been coexisting is low (Mahler et al, forthcoming) have received the same interpretation. But is ecological opportunity always a prerequisite for adaptive radiation?…”

“…4). Despite their nocturnal, gekkonid heritage, day geckos are similar in many ways to anoles (reviewed in Harmon et al 2007Harmon et al , 2008. Being diurnal, as their name implies, they are relatively small, insectivorous, sit-and-wait-foraging, arboreal green lizards with large toepads.…”

“…Also like anoles, they communicate through head movements and are highly territorial. Phelsuma has radiated independently in the Mascarene, Seychelles, and Comoros islands (Austin et al 2004;Rocha et al 2007;Harmon et al 2008). Within each radiation, species have diverged ecologically and morphologically; relationships between ecology and morphology similar to those exhibited by anoles have been detected (Harmon 2005;Harmon et al 2008).…”

“…One possibility is that the island environments in which they occur may differ in important ways. One example is that Madagascar, the ancestral cradle of Phelsuma (Harmon et al 2008), has nurtured another large radiation of diurnal, arboreal, and insectivorous lizards. The evolutionary radiation of chameleons-which are specialized to use narrow surfacesmay have constrained the ecological diversification of day geckos and may explain the lack of a day gecko equivalent to anoles specialized to using twigs.…”

Diversification of Dombeyoideae (Malvaceae) in the Mascarenes: Old Taxa on Young Islands?

“…Despite showing interesting features for the study of evolutionary processes, the biogeography and patterns of diversification of Mascarene taxa remain largely unknown in comparison to other insular systems such as Hawaii or the Galapagos (Parent et al 2008;Baldwin and Wagner 2010). Although the number of available phylogenetic studies of Mascarene taxa has increased over the last few years (e.g., Maurin et al 2007;Micheneau et al 2008), only a handful of these studies (e.g., Harmon et al 2008a;Strijk et al 2012Strijk et al , 2014 have analyzed diversification in light of the new framework of tests and methodological tools now available (Rabosky 2006b;Harmon et al 2008b;Glor 2010;Stadler 2011).…”