Spiders of the Family Uloboridae include the most primitive orb-weaving groups, as well as species that spin reduced triangular aerial webs and irregular webs. The silk that constitute these prey-capture webs are composites of threads produced by an oval plate of spigots (the cribellum) on the spider's abdomen. Variations in the morphology of the cribellum produces changes in the strength and stickiness of the silk. Dr. Brent Opell proposes to study the associations between various kinds of cribellar morphology, silk characteristics, web architecture, and predatory behavior in eight species of uloborid spiders. These species represent both reduced- and normal-web spinners from different evolutionary branches of the family. The proposed research will establish the degree to which form constrains function and behavior in a complex mechanical system. Further, the study may uncover underlying generalities concerning the historical development of the form-function associations (for instance, can a single cribellar change give rise to only certain web and behavior types, or can a single web type accommodate changes in behavior but not silk?). The proposed research addresses questions that are fundamental to all of evolutionary biology. This study will give new insight into the relative importance of current adaptive needs and historical constraint in the evolution of new features. The results of this study will be of interest to a wide range of functional, systematic, and evolutionary biologists.
