Eileen A. Hebets
Complex Behaviors of Arachnids
My research focuses on the evolution and function of complex signaling, with an emphasis on inter- and intra-specific communication among arachnids. The primary goal of my research is to understand the selection pressures that drive the evolution of secondary sexual traits and associated signals. The methods I use to achieve this goal incorporate multiple levels of analysis including broad comparative approaches concentrating on behavior as well as more mechanistic neuroanatomical and neurophysiological approaches.
There are three main research programs on which I am currently working: (1) complex signal evolution in the wolf spider genus Schizocosa, (2) Sexual selection as a potential driving force in the rapid diversification of jumping spiders on the sky islands of Southeastern Arizona, and (3) sensory ecology, neurobiology and behavior of amblypygids (Arachnida, Amblypygids).
- Complex signal evolution in the wolf spider genus Schizocosa - While there exists a substantial conceptual and empirical framework for studying and understanding signal evolution, this framework is based almost entirely on studies of signals in isolation or on sensory specialists. However, most animal displays are complex, consisting of multiple components sent serially and often overlapping. My research on Schizocosa wolf spiders brings a comparative approach to the analysis of complex courtship signaling, specifically multimodal signaling. Male courtship displays within this genus are either unimodal (only vibratory signals) or multimodal (visual and vibratory signals). Within multimodal species, there is further variation in the degree to which different species are ornamented. Unimodal signaling is ancestral in this group, raising the question of why a second modality has been added. My research then focuses on such questions as: What are the costs and benefits associated with multiple signaling for both signalers and receivers? What is the information content of the multiple signals and how does this influence complex signal evolution? How do both content-driven and efficacy-driven selection pressures influence the evolution of complex signals?
Variation in the degree of ornamentation in male Schizocosa forelegs
In a recent study, I found that subadult female experience in one species of Schizocosa influences adult female mating behavior, suggesting a role of learning and memory in mate choice. Future studies examining the evolutionary consequences of social influences on mate choice as well as studies examining the cognitive abilities of spiders are currently being planned.
- Jumping spider diversification - Populations of the jumping spider Habronattus pugillis isolated atop mountain ranges in southeastern Arizona display tremendous secondary sexual trait diversification. As recently as 10,000 or as long as 400,000 years ago, these populations were likely contiguous. Among the currently allopatric populations, males vary greatly in both their courtship behavior and the related ornamentation while females from the populations are not easily distinguished. Due to the restriction of population differences to male secondary sexual traits in conjunction with population genetic data, it is thought that sexual selection is responsible for the population differences. In collaboration with colleagues such as Wayne Maddison, we use a comparative approach to conduct reciprocal crosses between populations in an attempt to distinguish among different processes of sexual selection that could potentially be driving such a rapid and recent diversification.
- Sensory ecology, neuroanatomy, and behavior of amblypygids - Amblypygids are bizarre arachnids characterized by a dorso-ventrally flattened body, heavily spinded pedipalps, and modified first legs. Due to their nocturnal lifestyle and bizarre appearance, very little is known about this arachnid order. My initial studies of amblypygids are aimed at gaining basic insights into the natural history and field behavior of these animals and involve field studies in Costa Rica, the Florida Keys, as well as Puerto Rico. Amblypygids stand out among arachnids in that they possess extremely large mushroom bodies as well as giant interneurons located in their antenniform legs. Ultimately, a goal of my research program on amblypygids is to shed light onto the function of both the giant interneurons and the enlarged mushroom bodies of this group as well as to gain more general information about their natural history.