Biogeography, Systematics, and Ecomorphology of Pacific Island Anoles

Abstract

: Anoles are regarded as important models for understanding dynamic processes in ecology and evolution. Most work on this group has focused on species in the Caribbean Sea, and recently in mainland South and Central America. However, the Eastern Tropical Pacific (ETP) is home to seven species of anoles from three unique islands (Islas Cocos, Gorgona, and Malpelo) that have been largely overlooked. Four of these species are endemic to single islands (Norops townsendi on Isla Cocos, Dactyloa agassizi on Isla Malpelo, D. gorgonae and N. medemi on Isla Gorgona). Herein, we present a phylogenetic analysis of anoles from these islands in light of the greater anole phylogeny to estimate the timing of divergence from mainland lineages for each species. We find that two species of solitary anoles (D. agassizi and N. townsendi) diverged from mainland ancestors prior to the emergence of their respective islands. We also present population-wide morphological data suggesting that both display sexual size dimorphism, similar to single-island endemics in the Caribbean. All lineages on Isla Gorgona likely arose during past connections with South America, and ecologically partition their habitat. Finally, we highlight the importance of conservation of these species and island fauna in general.

Effect of topographic complexity on species richness in the Galápagos Islands

“…Island isolation was significant in models for five taxonomic groups: single‐island endemic plants (SIE_P), both vertebrate groups, reptiles and birds. While birds are the most obvious taxa to disperse between islands, lizards are often hypothesized and occasionally observed to disperse to oceanic islands through rafting (Censky et al, 1998; Phillips et al, 2019; Raia et al, 2017), and while Galápagos tortoises are poor swimmers, they can float and survive without food for an extended period of time (Caccone et al, 2002), allowing dispersal to proximate islands. Therefore, the degree of isolation for these groups makes sense as a predictor of species richness while native mammals (mostly from endemic radiation of muroid rats [Schenk & Steppan, 2018]) and low‐dispersing invertebrates (including snails, discussed below) may be more impacted by intra‐island factors (e.g.…”

A new species of Leucostethus (Anura, Dendrobatidae) from Gorgona Island, Colombia

“…Among vertebrates, the putative endemics include the catfish Trichomycterus gorgona Fernández & Schaefer, 2005, the anoles Anolis gorgonae Barbour, 1909 and A. medemi Ayala & Williams, 1988 ( Phillips et al 2019 ), the snake Atractus medusa Passos et al, 2009 , and an undescribed species of dendrobatid frog reported as “ Colostethus sp. Gorgona” by Grant et al (2017) .…”

What makes an island a suitable refuge for an endemic lizard?

“…I also expected that distance from the continent would be correlated with a greater presence of endemic species (Kougioumoutzis & Tiniakou, 2015). Marine channels, even if they are relatively shallow, can constitute an almost impassable barrier for some small lizards (Hurston et al., 2009), although there are also opposite examples (Phillips et al., 2019; Raia et al., 2017). Consequently, I hypothesized that isolation relative to other islands in an archipelago would be negatively associated with both groups of lizards.…”