Environmentally-induced shifts in behavior intensify indirect competition by an invasive gecko in Mauritius |
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Authors: | Nik C Cole Stephen Harris |
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Institution: | 1.School of Biological Sciences,University of Bristol,Bristol,UK;2.Durrell Wildlife Conservation Trust, Les Augrés Manor,Trinity, Jersey,Channel Islands |
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Abstract: | Most recorded extinctions have occurred on oceanic islands, mainly as a result of introduced mammalian predators. The impact
of introduced non-mammalian competitors, however, is poorly understood. The house gecko, Hemidactylus frenatus, is one of the most successful invasive reptiles and has been implicated in the decline of endemic geckos and other taxa
on a number of tropical and subtropical islands. We investigated the patterns of niche utilization between the house gecko
and endemic ornate day gecko, Phelsuma ornata, in Mauritius, two species which were not believed to compete because they had different diel activity periods. The dietary
and temporal niche partitioning of the two species were examined in relation to seasonal invertebrate prey abundance for three
seasons. Dietary overlap between the two species was least when prey abundance was lowest and temporal overlap in activity
greatest. Exploitative competition was therefore inferred, whereby changes in dietary overlap were attributed to shifts in
prey selection by the day, but not the house, gecko, which was hypothesized to deplete prey. The compensatory response of
the day gecko may have been to increase its tendency for cannibalism, such that the smaller house gecko was indirectly responsible
for population reduction of its larger competitor. This is the first study to show how an invasive nocturnal gecko may be
affecting a predominantly diurnal species. |
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