Salamander diversity tied to elevation, age of colonization in the tropics
Salamander diversity tied to elevation in the tropics
mongabay.com
February 13, 2007
Scientists have long documented high levels of biodiversity at mid-elevation ecosystems in the tropics, but no one has ever conclusively determined the underlying causes of this species richness. A new study, which examined 13 genera and 137 species of tropical salamanders (“olitoglossine plethodontids”), suggests that this pattern may result from the time when the habitats were first colonized.
Writing in the current issue of the , a team of scientists lead by John J. Wiens of Stony Brook University in New York, report “a strong relationship between the number of species in each elevational zone and the estimated time when each elevational band was first colonized.”
“Mid-elevation habitats were colonized early in the phylogenetic history of bolitoglossines [salamanders], and given similar rates of diversification across elevations, more species have accumulated in the elevational zones that were inhabited the longest,” they write. “Thus, given that rates of species origination and extinction are similar at different elevations, it appears that there are more species at intermediate elevations simply because bolitoglossines have been present, speciating and accumulating in those habitats for longer periods of time than in lower-or higher-elevation habitats.”
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The scientists say their findings have important conservation implications.
“In MesoAmerica, mid-elevation habitats not only harbour more species of bolitoglossines than lowlands, but also seem likely to harbour more phylogenetic diversity among species, given the same number of species,” they write. “If the pattern found in bolitoglossines characterizes other groups as well, it would suggest even greater urgency for protecting montane habitats in MesoAmerica (and possibly other regions) than indicated by the number of species alone.”
Tropical salamanders are not only threatened by habitat loss. Global amphibian populations are rapidly declining due to the widespread outbreak of an infectious skin disease—a type of chytrid fungus (Batrachochytrium dendrobatidis). In 2005 the Global Amphibian Assessment, a survey of the planet’s amphibian species, found that nearly a third (32%) of the world’s 5743 known amphibian species are threatened and 129 species have gone extinct since 1980. Some researchers have linked the emergence of the disease to climate change.
Citation: John J. Wiens, Gabriela Parra-Olea, Mario Garcia-Paris and David B. Wake (2007). Phylogenetic history underlies elevational biodiversity patterns in tropical salamanders. Proceedings of the Royal Society B. doi:10.1098/rspb.2006.0301
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