As well exemplified by a significant fraction of anole research, islands can act as natural laboratories of evolution. With limited space, fewer predators, simplified communities, and isolation from the mainland, islands often impose strong and distinctive selective pressures relative to continental habitats. However, although anoles provide some of the most famous examples of evolution on islands, insularity can exert its effects on different types of organisms.
In our recent paper in Reptiles & Amphibians (Zamalloa-Bustinza et al. 2025), we focused on the Peruvian Lava Lizard (Microlophus peruvianus), a conspicuous and widespread s
pecies found along the South America’s western coast that was deliberately introduced to several offshore islands in the 1940s. These introductions were intended as a potential biological control for guano-bird ectoparasites. Despite the abundance and broad distribution of Microlophus, this island–mainland system has received surprisingly little attention. Taking advantage of this relatively recent introduction, we explored whether island populations show evidence of rapid morphological divergence from their continental counterparts.
To explore this, we compared adult lizards from a mainland population in northern Peru (San Pedro de Vice) with individuals from an insular population on Lobos de Tierra Island. Rather than focusing on a single trait, we examined a suite of ecologically relevant morphological characters, including body size, head dimensions, and limb proportions, traits known to be tightly linked to feeding and locomotion in lizards.
After less than a century of isolation, island and mainland populations showed clear and consistent morphological differences. Island lizards were larger overall and had relatively longer limb elements and interlimb distances. In contrast, mainland individuals tended to have proportionally larger and taller heads, as well as longer fingers, toes, and femora.
These differences might be pointing to subtle but meaningful shifts in ecomorphology. The evolution of relatively larger heads and longer digits in mainland lizards may reflect the demands of exploiting a more diverse prey base and moving through open habitats where predators and competitors are present. On islands, larger body size may be favored under conditions of reduced predation, while longer forelimbs may be associated with the use of different microhabitats when compared to mainland populations.
Together, our results suggest that morphological differences between island and mainland populations can emerge rapidly following introduction. However, further research is needed to link morphological divergence to ecological causes, if any. Ongoing work is expanding this approach to additional islands along the Peruvian coast and to other aspects of the phenotype, including behavior. These efforts will help determine whether the morphological patterns observed here are consistent across the species’ broad geographic range and how closely they align with ecological differences among localities.
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