Genes Record a Prehistoric Volcano Eruption in the Galápagos.

VOLCANOES; ISLANDS; LANDFORMS; POPULATION; GEOPHYSICS; RESEARCH

This article focuses on a study related to a prehistoric volcano eruption. Volcanic islands provide notable examples of the parallel between a changing geographic area and its changing biota. This is particularly true for young islands where volcanic activity is known to dictate the rate of population extinction and recolonization and to influence evolutionary diversification. Alcedo is located on Isabela, an island with five giant tortoise taxa occupying each of its five major volcanoes. The Alcedo taxon is a genetically differentiated population found in vegetated areas of the volcano. The time since population contraction can be estimated from distinctive mtDNA network, which is composed of abundant and ancestral haplotype 61 and the four recently descended haplotypes. Reduced variability is likely due to reinvasion of Alcedo by tortoises with haplotype 61 that survived the eruption. Hence, the geologically estimated time of volcano eruption should predate the coalescence of haplotypes 62 to 65. Researchers confirmed this prediction using methods that suggest a coalescence of the existing variation of about 88,000 years. Given that G. n. vandenburghi is genetically and morphologically divergent from southern Isabela populations, the study supports a generalized theory that population contractions influence evolutionary diversification.