Difference within Common Species May Predict the Presence of Rare Animals
When deciding whether or not to clear a patch of rainforest land for development, scientists are often called in to quantify how many different species exist there. But determining the number of rare and threatened species living in a section of jungle isn't easy. If they are very rare, the individual members of the species will be hard to find; if the area being surveyed is along a steep slope it may be difficult to access the area; if there are lots of species to identify, you might need to hire a dream team of biologists—each specialized within a different area of biodiversity—and that can get expensive. However a new study in the Proceedings of the Royal Society Journalby an international group of scientists suggests a more cost-effective and efficient way to rapidly assess local biodiversity: instead of spending time and money looking ateverything—searching for rare and threatened individuals in a forest patch or on a hillside—focus instead on the biological difference which can easily be determined within a few, easy-to-find,commonspecies.
"We show how regions where common species exhibit high genetic and morphological divergence among populations can be used to predict the occurrence of species of conservation concern," Trevon Fuller, postdoctoral researcher at the Center for Tropical Research at UCLA, told mongabay.com.
Scientists from UCLA, Boston University, Stony Brook, and the Universities of Florida Gainseville, North Carolina, Arizona, Texas, as well as from institutions in Ecuador, Spain, and the UK, hypothesized that there would be more threatened species at selected sites based onintraspecific(in a single species) variation within common species.
While past studies have found correlations between diversity within a single species and the total number of species in an area, they have not focused on conservation.
"The new contribution of our work is to show that genetic and phenotypic diversity within species is a good predictor of species that face a high risk of extinction because they have small ranges or are experiencing rapid habitat loss," Fuller explains.
The scientists chose western Ecuadorian rainforest for their research. They focused on quantifyinggeneticvariation andmorphologicalorphenotypicalvariation (observable variation in the form, appearance, or structure of organisms, i.e. their specific structural features) among easy to find, common species. Threatened by human impacts, this biodiversity hotspot represents a transition zone between humid and dry tropical forests.
"We analyzed Ecuador west of the Andes, which is a global hotspot of plant endemism [uniqueness] with 6,300 species, 20% of which are endemic, and has 650 bird species”¦The diversity of this area is due to the fact that it is a transition zone between dry forest and rainforest. However, the area is also under threat due to high rates of deforestation for timber extraction and the expansion of cattle pastures," Manuel Peralvo, Geographer at The Consortium for the Sustainable Development of the Andean Ecoregion (CONDESAN, Consorcio para el Desarrollo Sostenible de la EcorregiÃ³n Andina, told mongabay.com.
The study site was chosen for its steep slopes and hillsides ("elevational gradients"), areas that Peralvo explains are especially worthy of conservation focus as they support a high number of threatened specialist and niche species.
"Elevational gradients also have some of the last forest remnants in western Ecuador since lowlands have already been cleared. As a result, they are subject to accelerating deforestation and hence have a high number of threatened species," Pervalo adds.
The scientists chose three birds, three bats, and one frog species (to serve as proxies for threatened species) along the gradient because they were abundant and easily sampled, in addition to representing a range of different niches, locations, diet types, altitudes, and life histories. The scientists also surveyed select plants of conservation concern, representative of vegetation communities at high risk of deforestation. They focused on the intraspecific differences (variations observed within a single species) of the seven common populations to predict the presence of dozens of threatened Ecuadorean species.
"We analyzed a diverse set of 29 threatened species that are hard to sample including mammals such as jaguars and ocelots, birds including the Guayaquil woodpecker, and plants. We also analyzed a set of seven common species that are easy to sample including bats, birds, and a frog," Fuller explains. "We had genetic for five of the common species and phenotypic data (such as wing length) for all seven. We found that genetic and morphological diversity within common species was a better predictor of threatened species than the number of species at a site, or environmental variables such as precipitation, temperature, or elevation."
In fact, sites selected based on genetic and morphological divergence of common species contained a higher proportion of threatened species than any other method, including sites selected at random or regions selected using environmental variables or bird and amphibian occurrences as a proxy.
"Our results show that the genetic and morphological variation exhibited by common species effectively predicts the occurrence of threatened species in western Ecuador," the authors summarize in their article,Intraspecific morphological and genetic variation of common species predicts ranges of threatened ones.
Sites selected based on genetic and morphological traits contained 2.1 times as many threatened species as sites selected based on environmental variables, and 1.7 times as many as sites based on bird and amphibian occurrences.
"Intraspecific variation of common species of birds, bats and frogs from Ecuador were found to be a significantly better predictor for the occurrence of threatened species than suites of environmental variables or the occurrence of amphibians and birds. Fully 93 % of the threatened species analyzed had their range adequately represented by the geographical distribution of the morphological and genetic variation found in seven common species," Fuller explains.
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