![]() ![]() ![]() The balance of evidence overwhelmingly indicates that each lineage is highly distinct based on thousands of genome-wide markers 11, 12, 13, demonstrating that they are separately evolving as lineages within a larger metapopulation, which is the core concept within all species concepts 9.ĭiversification of Galapagos tortoises has followed the island progression rule, with the oldest islands being home to the earliest diverging lineages 6. Therefore, we follow the taxonomy of Rhodin, et al. However, a criterion of minimum clade age does not correspond to any of the commonly recognized species concepts 9. Due to the recent nature of the radiation, there is debate as to whether the taxa should be considered species or subspecies, since their diversification is younger than almost any other congeneric pair of tortoise species 7, 8. 1), all of which evolved from a single ancestor that colonized the volcanic archipelago within the last 3 million years 3, 4, 5, 6. The radiation of giant tortoises endemic to the Galapagos consists of 14 named taxa (Fig. Despite being known previously from only one specimen, the Fernandina tortoise has been considered to represent a distinct taxon: a previous analysis of 1682 base pairs of mitochondrial DNA obtained from this specimen showed 1.8% sequence divergence from the other Galapagos tortoise species, and produced a phylogeny in which the Fernandina Island tortoise is sister to one of the Santa Cruz Island species, C. The fantastic nature of the Fernandina giant tortoise is due to the extraordinary morphology of the male specimen, with extreme flaring of its marginal scutes and unusually prominent “saddlebacking” of the front section of the carapace, unlike any other tortoise yet observed in Galapagos, or elsewhere on the planet as saddlebacking is unique to Galapagos tortoises 2. A single specimen of Chelonoidis phantasticus-“The Fantastic Giant Tortoise”-was collected by the explorer Rollo Beck during an expedition by the California Academy of Sciences in 1906 1. Caption by Laura Rocchio.Since 1906, evidence has accrued that a mysterious species of giant tortoise might exist on Fernandina Island, an active volcano that stands alone on western periphery of the Galapagos Archipelago and is reputed to be the largest pristine island on Earth. NASA image by Jesse Allen, Robert Simmon, and Michael Taylor, using data from the USGS Global Visualization Viewer. In June 2012, George died, making the Pinta subspecies extinct and leaving the islands with just 10 subspecies of tortoise. In 1972, the last survivor of the Pinta subspecies of giant tortoise-named Lonesome George-was moved to the Charles Darwin Research Station on Santa Cruz Island. In 1914, herpetologist John Van Denburgh catalogued 15 subspecies of giant tortoises in the Galapagos. Pirates, sailors, whalers, and settlers decimated the tortoise population by successively hunting them from the 17th century until 1959, when the Ecuadorian government made the Galápagos a national park. Once in the Galápagos, the turtles evolved into different subspecies as different traits were advantageous for life on the different islands. They likely reached the Galápalos from South America-some 1,000 kilometers to the east-by rafting on currents. Galápagos tortoises are the world’s largest living turtles. The feral goat population soared to 40,000, causing much destruction to the vegetation and the native species that feed on it. In the 1950s, however, fishermen introduced goats to the island. The island’s extraordinarily diverse plant population can be attributed to Pinta’s relative isolation in the archipelago its varied climatic zones along its 2,000 foot (650 meter) peak and the influence of the plant-eating giant tortoises that once thrived on the island.įor ages, Pinta’s isolation helped to protect it from the introduction of invasive, non-native species that can destroy plants and habitats. Of these, 59 are only found in the Galapagos 19 are found only on a small number of the islands and two are endemic to Pinta. The darker greens, closer to the peak and crater, depict the island’s densest region of vegetation, which is fueled by moister and cooler conditions at higher elevations.ĭespite some tough conditions, Pinta hosts 180 taxonomic groups of plants. The light green ring circling the central volcanic peak shows the location of sparse deciduous forest and grassland that is suited to the harsh, dry conditions at sea level in the eastern Pacific. The dark pattern of old lava flows can be seen along the northern and eastern flanks of the 60-square kilometer island. The Enhanced Thematic Mapper Plus (ETM+) on Landsat 7 captured this natural-color image of Pinta Island on April 7, 2009. In the northern reaches of the Galápagos Islands lies Pinta, a volcanic island that accounts for less than one percent of the archipelago’s land area, yet hosts nearly one third of the native terrestrial plants.
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