DNA barcoding has been used in the past to identify new organisms, including jellyfish, bats and fungi. And scientists around the world are actively building a database of DNA bar codes for hundreds of thousands of species - an initiative that began in 2007. But barcoding DNA from a spider web had never been attempted before this study, Xu said.
Xu and his team had a leg up when it came to identifying the DNA they extracted from the black widows' webs; they already knew what DNA they were looking for (that of black widows and house crickets). This allowed them to create primers that amplified the right kind of genes - the mitochondrial genes that form the species' DNA bar codes. But a slightly modified technique could also be used to identify DNA from any web, even if a researcher isn't sure what kind of spider made it or what kind of prey the spider captured. [Amazing Photos of Spiders from Around the World]
Using this technique, known as "next generation meta-barcoding sequencing," researchers could simply walk into a forest or field, collect any spider webs they might stumble upon and then sequence the webs' DNA in a lab without knowing beforehand what kind of DNA is on the web. The more advanced technique could give researchers detailed insight into the kinds of spiders and insects that reside in a particular area, Xu said. DNA can remain on a web for long periods of time (at least 88 days, in the case of one of the webs used in the study), he added.
"These genetic technologies can be a lot more sensitive than traditional sampling methods and enable us to detect DNA of any spider or insect without having to specify which species we're looking for in the first place," Xu said. "They could allow earlier detection of [endangered or invasive] species. For endangered organisms, it could be important for marking off new conservation areas, or for invasive species, redrawing the invasive range."
But ecologists aren't the only ones who might find it useful to extract DNA from a spider's web. Pest management researchers could use meta-barcoding sequencing to find out what kinds of spiders are hitching rides inside crates of imported goods, or to discover which species of spiders have invaded a person's home. And those who study biogeography (the study of the distribution and evolution of species over time and geographic location) could extract DNA from spider webs to understand population differentiation within a single species.
"If you can collect the DNA without having to capture the organisms themselves and kill them, it makes the process a whole lot easier," Xu said. And this method of "collecting" spiders could make it easier for citizen scientists to assist in research projects or to find out more about their local ecosystems, he added.
Going forward, Xu said he'd like to spend some time in the woods, collecting webs and then trying to figure out which members of the local spider and insect community left their DNA behind on the sticky silk.
The new study was published today (Nov. 25) in the journal PLOS ONE.
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