Searching For the Tree of Life

Academy scientist Charles Griswold is helping to build the branches of a massive "tree of life" for spiders.

After spending the last 25 years studying the classification and evolution of spiders, Academy scientist Charles Griswold may be slightly biased when he says that spiders are one of the most important organisms on Earth. On the other hand, only five other groups of animals on the planet contain more species than the spider order, Araneae. Present on every major land mass (except, perhaps, Antarctica), spiders are a crucial component of most terrestrial ecosystems, and they often have a direct impact on human affairs. Because of their importance, the National Science Foundation has sponsored a program to determine the evolutionary relationships between every group of spiders on Earth - a project called the "tree of life" for spiders. To build this tree, Griswold is working with sixteen other scientists from six different countries to collect DNA samples, morphological data, and behavioral observations from all 110 recognized families of spiders.

Griswold's most recent contributions to the project have come from Myanmar, where he and fellow Academy arachnologist Darrell Ubick spent the past four weeks studying spiders that live only in Southeast Asia. While in the field, he found several fascinating species, including the Invisible ground spider, Cryptothele, which stays out of sight by covering itself with dirt, and the Oriental Ornamented Orb Weaving Spider, Herennia ornatissima, which displays an unusual mating behavior - the male's genitalia often break off within the female to prevent subsequent males from mating with her.

The "Oriental Ornamented Orb Weaving Spider", Herennia ornatissima, lives in webs built on tree trunks and walls.
Photo: Dong Lin
Griswold searched for spiders in this evergreen forest at Popa Mountain, Myanmar. Photo: Dong Lin
Beating the vegetation is one technique that Griswold used to collect spiders in Myanmar. As he and his colleagues assemble their tree of life, it will have applications beyond the doors of natural history museums. When scientists discover a spider silk that can be used to make glue or a venom with medicinal value, they will be able to predict the related spiders that might produce the same products.
Photo: Dong Lin
The "Invisible ground spider", Cryptothele, encrusted with dirt. Photo: Dong Lin