Mitochondrial DNA evolution and population history of the Tenerife skink Chalcides viridanus
ABSTRACT Recent studies of island lizards have suggested that historical vicariance as a result of volcanism may have played an important role in shaping patterns of within-island genetic diversity. The skink, Chalcides viridanus, shows variation in morphology within the volcanic island of Tenerife. Two mitochondrial DNA (mtDNA) fragments (from the 12S and 16S rRNA regions) were sequenced in individuals from 17 sites to evaluate the relationship between current phylogeography and the geological history of the island. Three main clades were detected. The two most basal clades were restricted to areas representing the ancient precursor islands of Teno and Anaga in the northwest and northeast of Tenerife, respectively. The third clade showed a widespread geographical distribution and provided evidence of a recent rapid expansion after a bottleneck. Within-island cladogenesis appears to have taken place during a recent period of volcanic activity and long after the ancient islands had been united by the eruptions that led to the formation of the Canadas edifice. Evidence of similar biogeographical histories are found in other species in the Canary archipelago, supporting the volcanism scenario as a potentially widespread cause of within-island differentiation in reptiles.
Full-textDOI: · Available from: Jose Pestano, May 28, 2014
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ABSTRACT: AimThe seminal theory of island biogeography, based on changing rates of immigration and extinction, should be seen in a geological context, as an island's maturity influences the richness of its biota. Here, we develop an island biogeography of biotic interactions, recognizing that, besides species richness, biodiversity also encompasses the multitude of interactions among species. By sampling interactions between plants and pollinators across the Canarian archipelago, we illustrate how the local richness, specialization and endemism of biotic interactions vary with island age and area. LocationCanary Islands (27.62° N–29.42° N and 13.33° W–18.17° W). Methods On five islands, covering the full age range of the archipelago, plant–pollinator interactions were catalogued and their strength estimated. Network parameters (e.g. interaction richness and specialization) and the number of single‐island interactions (equivalent to single‐island endemics) were estimated from interaction matrices and related to island area and age. ResultsPlant species richness, interaction richness and average degree of specialization of pollinator species showed hump‐shaped relationships with island age. Pollinator richness varied with island area and plant richness. Plant specialization increased with island age, and the proportion of single‐island interactions (pSII) exhibited a U‐shaped relationship with age. Main conclusionsThe previously reported hump‐shaped relationship between species richness and island age, both on the scale of islands and of habitats, was confirmed for plant species in local networks. Both plants and pollinators were more generalized on the youngest island, which may be due to a predominance of generalist colonists. Pollinator specialization peaked on mid‐aged islands, whereas plants showed the highest specialization on old islands, potentially reflecting their different life histories. The U‐shaped relationship between the proportion of single‐island interactions and island age might be explained by (1) young islands having a high proportion of unique interactions, due to interactions between generalists, and (2) old islands having unique interactions due to an accumulation of unique pairwise interactions that have evolved through time. Thus, island age – which not only captures time per se, but also the geomorphological changes of islands – may act as a regional driver of local network structure, and so the contemporary networks we observed across the Canarian archipelago illustrate the development of a network through geological time.Journal of Biogeography 10/2013; 40:2020-2031. DOI:10.1111/jbi.12165 · 4.97 Impact Factor
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ABSTRACT: Population divergence and speciation are often explained by geographical isolation, but may also be possible under high gene flow due to strong ecology-related differences in selection pressures. This study combines coalescent analyses of genetic data (11 microsatellite loci and 1 Kbp of mtDNA) and ecological modelling to examine the relative contributions of isolation and ecology to incipient speciation in the scincid lizard Chalcides sexlineatus within the volcanic island of Gran Canaria. Bayesian multispecies coalescent dating of within-island genetic divergence of northern and southern populations showed correspondence with the timing of volcanic activity in the north of the island 1.5-3.0 Ma ago. Coalescent estimates of demographic changes reveal historical size increases in northern populations, consistent with expansions from a volcanic refuge. Nevertheless, ecological divergence is also supported. First, species distribution modelling shows that the northern morph is associated with mesic habitat types and the southern morph with xeric habitat types. It seems likely that the colour morphs are associated with different anti-predator strategies in the different habitats. Second, coalescent estimation of gene copy migration (based on microsatellites and mtDNA) suggest high rates from northern to southern morphs demonstrating the strength of ecology-mediated selection pressures that maintain the divergent southern morph. Together, these findings underline the complexity of the speciation process by providing evidence for the combined effects of ecological divergence and ancient divergence in allopatry.This article is protected by copyright. All rights reserved.Molecular Ecology 08/2014; 23(19). DOI:10.1111/mec.12897 · 5.84 Impact Factor