Out-competed by an invader? Interference and exploitative competition between Tropical House Gecko (Hemidactylus mabouia Moreau de Jonnès, 1818) and Barbados Leaf-Toed Gecko (Phyllodactylus pulcher Gray, 1828) for diurnal refuges in anthropogenic coastal habitats

House Geckos in the genusHemidactylusare highly successful colonizers of regions beyond their native range, often resulting in displacement of native gecko species through competitive interactions for daytime refuge (crevices) and prey resources. We report on data collected from night time surveys undertaken in April-May 2014 on Barbados, West Indies, that focused on the distribution and abundance of the endemic Barbados Leaf-Toed Gecko (Phyllodactylus pulcher) and the introduced Tropical House Gecko (Hemidactylus mabouia) along unlit coastal walls and among boulders in the grounds of a hotel resort. In contrast to patterns of displacement of native species byH. mabouiaseen elsewhere,P. pulcherwas more abundant thanH. mabouiaon coastal walls, whereas the latter was found in greater numbers using boulders at this site. Walls and boulders differed with regard to availability of diurnal refugia suitable for geckos; with the walls having high frequency of small crevices with openings < 20 mm, and boulders offering very little cover other than the underside of the boulder itself. To investigate if this niche separation was a result of differences in diurnal refuge use between the species, we conducted experimental trials in which geckos were allowed to select between refugia with different characteristics. Both species selected for narrower and warmer refugia, and refugia that had been previously occupied by the other species. These shared preferences for refugia type suggest that other factors underlie the niche separation observed in the field. In supporting high densities ofP. pulcher, coastal walls could offer important secondary habitat by augmenting the natural cliff side habitat of this endemic gecko, a finding that could be exploited for the conservation of this candidate species for Critically Endangered classification.