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discovered a new Galap iguana species
An overlooked pink species of land iguana in the Galápagos
Gabriele Gentilea,1, Anna Fabiania, Cruz Marquezb, Howard L. Snellc, Heidi M. Snellc, Washington Tapiad,
and Valerio Sbordonia
aDipartimento di Biologia, Universita` Tor Vergata, 00133 Rome, Italy; bCharles Darwin Foundation, Puerto Ayora, Gala´pagos Islands, Ecuador; cDepartment
of Biology and Museum of Southwestern Biology, University of New Mexico, Albuquerque, NM 87131; and dGalápagos National Park Service, Puerto Ayora,
Gala´pagos Islands, Ecuador
Edited by Francisco J. Ayala, University of California, Irvine, CA, and approved November 11, 2008 (received for review July 2, 2008)
Despite the attention given to them, the Galápagos have not yet finished offering evolutionary novelties. When Darwin visited the Galápagos, he observed both marine (Amblyrhynchus) and land (Conolophus) iguanas but did not encounter a rare pink blackstriped land iguana (herein referred to as ‘‘rosada,’’ meaning ‘‘pink’’ in Spanish), which, surprisingly, remained unseen until 1986. Here, we show that substantial genetic isolation exists between the rosada and syntopic yellow forms and that the rosada is basal to extant taxonomically recognized Galápagos land iguanas. The rosada, whose present distribution is a conundrum, is a relict lineage whose origin dates back to a period when at least some of the present-day islands had not yet formed. So far, this species is the only evidence of ancient diversification along the Galápagos land iguana lineage and documents one of the oldest events of divergence ever recorded in the Galápagos. Conservation efforts are needed to prevent this form, identified by us as a good species, from extinction.
The most surprising result was the deep divergence of the rosada lineage at the basis of the Conolophus clade. This species alters the current thinking about the timing of diversification of land iguanas, which was previously supposed to have occurred in the Pleistocene Epoch (6). Although with a large SD, our estimate sets the origin of this relict lineage back to a period when at least some of the present-day islands had not yet formed. In fact, the oldest extant islands in the archipelago, San Cristo´bal and Espan˜ola, are at least 2.35 and 3.3 million years old, respectively, if not older (7). Thus, given its present distribution, the rosada form clearly represents a conundrum because it occurs only on Volcan Wolf, which is considered younger than Volcan Sierra Negra (0.53 million years, the oldest volcano of Isabela) ( and almost as old as Volcan Cerro Azul (0.35 million years) (9). The ML average genetic distance between C. subcristatus and C. pallidus is much lower than between the rosada form and each of the 2 named species, supporting the distinctiveness of the taxon. Our preliminary data on the morphology of the rosada and yellow forms also indicate differentiation: in addition to their color pattern and independent of their gender, all rosada
individuals investigated are distinguished from the other 2 species by flat dorsal head scales and the prominent adipose nuchal crest with small conic scales. The rosada also shows strong differences in the pattern of the ‘‘head-bob’’ (nodding), a behavior important in territoriality (10) and courtship (11). The microsatellite data also indicated strong differentiation between the rosada and yellow forms, with mutation and genetic drift (in particular for the rosada form) being important determinants.
The mtDNA haplotype of the rosada is highly differentiated from those of marine iguanas and the rest of land iguanas. The results of theRDP3 analyses allow us to reject the hypothesis that such differentiation might have occurred by mtDNA recombination after hybridization between land and marine forms. The hypothesis of the origin of the rosada by recent hybridization alone between the 2 forms is not supported either. In fact, a rosada-like haplotype is not found in our sample of yellow iguanas, or in marine iguanas. This is indicated by a phylogenetic analysis that we performed by combining original haplotypes from the present study with those found by Rassmann et al. (6) in their sample of 150 marine iguanas from 21 locations on 14 islands [see supporting information (SI)].
These findings call for a conservation program aimed at evaluating the risk of extinction of this newly recognized species, which, based on currently available data, would be assignable to the ‘‘critically endangered’’ category by meeting criteria B and C of the International Union for Conservation of Nature (IUCN) Red List (14).
|discovered, galap, iguana, species|
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