Dimorphism and divergence in island and mainland Anoles

Abstract

Relative to the West Indies, the ecology and evolution of anoles inhabiting islands off Central and South America have received little attention. The paucity of studies on continental islands has limited our ability to generalize and extend results based on the West Indian paradigm, as well as our understanding of the profound differences between the adaptive radiations of continental vs. Greater Antillean anoles. Here we compare the morphological, ecological, behavioural and genetic divergence between Anolis nebulosus populations inhabiting a small island in the Bay of Chamela, Mexico, and a nearby mainland forest. Notably, the two populations exhibit intra-sexual dimorphism with respect to head and limb sizes, the first such polymorphism documented for an Anolis species. We also compare the shape of island and mainland A. nebulosus with each other, the six West Indian ecomorphs and a hypothetical generalist species. Finally, we address the generalist convergence hypothesis for anoles on single species islands. We conclude that convergence on a generalist morphology is widespread among solitary anoles in the West Indies. We present data on a limited sample of solitary anoles with mainland ancestors that suggest a parallel convergence on a similar generalist morphology, probably due to similar adaptive landscapes shaped by selective forces common to small island environments.

Insularity effects on the morphological space and sexual dimorphism of a tropical tree lizard in western Mexico

“…Previous ecological studies on lizard species (i.e. Anolis nebulosus ) inhabiting SAI have shown lower predation and interspecific competition, as well as higher intraspecific competition compared with their mainland counterparts (Siliceo‐Cantero & García, 2014, Siliceo‐Cantero & García, 2015, Siliceo‐Cantero & García, 2016; Siliceo‐Cantero et al , 2016; Siliceo‐Cantero et al , 2017). Consequently, an increased activity, life expectancy and morphological changes characterized lizards inhabiting the island.…”

“…The Mosimann's geometric mean has been used to study morphological differences among lizard species and populations as it allows for a geometrical interpretation of body shape (Butler & Losos, 2002; Butler, Sawyer & Losos, 2007; Siliceo‐Cantero et al , 2016). We preliminarily tested whether or not there was a residual size effect or non‐normal data distribution for any of the considered variables.…”

Phylogeny, biogeography and island effect drive differential evolutionary signals in mainland and island lizard assemblages

“…These results may indicate greater competition (congeneric, intergeneric, or both) regarding these traits on the mainland, that variability of these traits is greater among source pools available to mainland assemblages than those available to island assemblages (i.e. greater variation within discrete mainland regions than within islands), that a greater abundance of predators in mainland systems (Siliceo-Cantero et al, 2016) has promoted the evolution of multiple predator avoidance tactics that are manifest in these traits, or perhaps some other factor. Traditionally, these kinds of patterns are attributed to greater perceived diversity and complexity in mainland environments (Schluter, 1988(Schluter, , 2000.…”

Morphological evidence of sexual dimorphism in a Continental anole species of southeastern of Mexico

“…SD in the genus Anolis has been explained with reference to gular dewlap and other morphologic traits associated with body shape (ecomorphs) in West Island Anolis lizards (Butler et al 2007;Losos 2009;Johnson and Wade 2010), while SD in mainland Anolis species has mostly been related to SVL, perch use, and diet (Perry 1996;Ramírez-Bautista and Vitt 1997;Ramírez-Bautista and Benabib 2001). Despite this, there is little information about SD in most of the mainland Anolis species; therefore, it is necessary to determine whether SD occurs in other morphological structures beyond previously reported (Márquez et al 2005;Siliceo-Cantero et al 2016;Hernández-Salinas et al 2019). Therefore, the goal of this study is to analyze the SD of a tiny mainland anole species Anolis unilobatus Köhler and Vesely 2010; east pacific and central depression Chiapas clade see Gray et al 2019 (We will refer as Anolis unilobatus to the populations of the east pacific lineage, but we are aware of these populations belong to an evolutionarily independent lineage to the populations of the west pacific and of central America Gray et al 2019).…”