Microlophus

Microlophus is a genus of tropidurid lizards native to South America. Around 20 species are recognized and 10 of these are endemic to the Galápagos Islands, where they are commonly known as lava lizards (they are sometimes placed in Tropidurus instead). The remaining, which often are called Pacific iguanas, are found in the Andes and along the Pacific coasts of Chile, Peru, and Ecuador.

The distribution of the lava lizards and their variations in shape, colour, and behaviour show the phenomenon of adaptive radiation so typical of the inhabitants of this archipelago. One species occurs on all the central and western islands, which were perhaps connected during periods of lower sea levels, while one species each occurs on six other more peripheral islands. All have most likely evolved from a single ancestral species. However, as usual for the Tropiduridae, they can change their colour individually to some extent, and members of the same species occurring in different habitats also show colour differences. Thus, animals living mainly on dark lava are darker than ones that live in lighter, sandy environments.

Evolution

Galápagos adaptive radiation

The genus Microlophus colonized the Galápagos archipelago on two separate occasions, both during the Pleistocene. Most of the Galápagos endemic species radiated from the first colonization event known as the Western radiation. Two species, M. bivittatus and M. habelii, radiated from the second colonization event, and are sister to the continental species M. occipitalis.

Historically, the species M. albemarlensis was considered to occur on Isabela, Fernandina, Santiago, Santa Cruz, and Santa Fe islands. The species was later realized to actually be a species complex, and more recently, the Santiago, Santa Cruz, and Santa Fe populations have been given species status as M. jacobii, M. indefatigabilis, and M. barringtonensis, respectively. This restricts the range of M. albemarlensis to the Isabela and Fernandina islands.

Species

Listed alphabetically by specific name.

Nota bene: A binomial authority in parentheses indicates that the species was originally described in a genus other than Microlophus.

Further reading

• Duméril AMC, Bibron G (1837). Erpétologie générale ou Histoire naturelle complète des Reptiles. Tome quatrième [Volume 4]. Paris: Roret. ii + 571 pp. (Microlophus, new genus, pp.334–335). (in French).