Dr. Linda S. Rayor
What Changes with the Evolution of Sociality? A Comparative Study in Social & Solitary Huntsman Spiders.
February 13, 2012
AAG008 5:00 pm
Throughout Animalia are examples of closely related taxa in which the majority of species live essentially solitary lives while a few species have evolved to live in cooperative social groups. What factors make cooperation beneficial while closely related species succeed without those benefits? Spiders are excellent model organisms to examine the issues associated with costs and benefits of living in groups. Because spiders are readily cannibalistic, the potential costs associated with living in groups are greater. Less than 1% of all spiders live in groups.
My work has focused on the unusual endemic Australian huntsman spiders (Sparassidae: Deleninae) whose social interactions are at a juncture between prolonged subsocial (mother-offspring groups) and complex (almost) cooperative groups. All of the huntsman spider species are attentive mothers, aggressively guarding egg sacs and newly emerged young. Thus, all are pre-adapted for prolonged social interactions with their offspring. In most of the 10 genera, however, the young only associate with their mothers for two to three weeks. Yet three delenine species significantly prolong the period of maternal and sibling association to produce matrilineal groups with a single female (mother) and multiple clutches of offspring living together in retreats. In the best studied species, Delena cancerides, the young remain together in the retreat for ~1 year until they reach sexual maturity. The two Eodelena species remain in groups until they are subadults (many months). Patterns of group-living in these atypical, non-web building spiders are quite different from those in all of the other web-based social spider species. In 23 species from 9 of the 10 Delenine genera, I have compared developmental trajectories, patterns of prey sharing, early interactions, and metabolic rate to determine which traits are associated with sociality. There are many significant benefits and reduced costs, as well as physiological adaptations associated with group-living in the social huntsman species. In contrast, comparable benefits and cost reductions are not seen in solitary species, resulting to early natal dispersal.
Dr. Linda S. Rayor is a faculty member in the Department of Entomology at Cornell University. After getting an undergraduate degree in molecular biology at the University of Colorado and realizing the error of her ways, Linda Rayor switched to studying animal behavior which is what she was really interested in all along. She got her doctoral degree at the University of Kansas studying mother-offspring dynamics of prairie dogs and other ground squirrels. When her prairie dogs all died of the plague during her dissertation research, she decided to switch to social spiders. Dr. Rayor has studied social spiders in Mexico and Australia. Her current research focuses on how large, predatory huntsman spiders are able to live in big family groups peacefully and how they differ from other huntsman spider species that are cannibalistic. Dr. Rayor has won numerous teaching awards (Kaplan Family Distinguished Achievement in Service-Learning; CALS Innovative Teacher Award ; Entomology Society of America) for her courses on Spider Biology, Insect Behavior, and a course on how to do effective scientific outreach at Cornell University. Dr. Rayor directs a large K-12 science outreach program that emphasizes backyard biology and natural history in Central New York. She is currently appearing in the 2nd season of Monster Bug Wars series on Discovery Science channel. She is one of two on-camera scientists talking about the behavior and biology of predatory arthropods.