| Summary: | Masafuera Rayadito (Aphrastura masafuerae; Furnariidae) is a Critically Endangered species endemic to Alejandro Selkirk Island (Juan Fernandez Archipelago, Chile). Categorized as probably extinct in 1980, later estimates, ranging from 140 (in 2002) to 500 individuals (in 2006-2007), showed a fluctuating population size of the species. The grazing of goats and cattle has increased habitat loss for the species. Other threats are lack of nesting sites, introduced species such as feral cats and rats (Rattus rattus and R. norvegicus), and increased populations of natural predators like the Masafuera Hawk. In order to increase the availability of nesting sites, 81 nest boxes were installed in different habitats in 2006, with evidence of use during subsequent breeding seasons. Despite conservation concerns, however, no genetic studies are yet available for this furnariid. This study reports for the first time the levels of genetic divergence of the species, based on nucleotide sequences of the mitochondrial DNA (cytochrome oxidase subunit 1 gene; COI). Aphrastura masafuerae is closely related to a widespread species of furnariid distributed mainly in Chile on the mainland, the Thorn-tailed Rayadito (A. spinicauda). The Masafuera Rayadito diverged from its mainland sister species probably during the Pleistocene 0.57 +/- 0.19 Myr ago. Consistent with mitochondrial and nuclear molecular clocks, the estimated time of the split between A. masafuerae and A. spinicauda is in perfect agreement with the geological origin of the Juan Fernandez Archipelago, which is of volcanic origin. In order to assess genetic variability within the population of this fragile bird, further studies using a multi-locus genetic approach at the population level are necessary.
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