DISSERTATION RESEARCH: Selection and Signal Evolution: Diversification of Peacock Spiders (genus: Maratus)

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

This project examines color vision in peacock spiders, which are some of the most conspicuously colored animals described. Males of this group exhibit complex color patterns on abdominal fans and data suggest that these colored patches are used by females to make mating decisions. Peacock spiders, and jumping spiders in general, have some of the most unique visual systems described. However, a long-standing question that has yet to be answered for these spiders, as well as many other animals, is how do females evaluate color. The overall goal of the project will be to test the hypotheses that differences in visual system features between species are related to the diversity of colors and courtship displays seen across this group. An in-depth look at the visual properties of these animals will enhance our interpretation of behavioral and ecological data already collected in this system, inform our understanding about sensory system limitations as well as provide the necessary groundwork for future research on the sensory ecology of this charismatic spider group as well as other animals. All of the results and findings will be widely available to a variety of audiences through publication in peer-reviewed journals, participation in professional conferences, and online databases. In addition, the researchers have a strong commitment to outreach and education among students of all ages. Salticids have one of the most unique visual systems in the animal kingdom, and are easily distinguished from their relatives by their distinctive eye arrangement. In particular, their anterior median eyes (AME) are enlarged, and contain tiered retinae. The leading hypothesis about the function of tiered retinae is that each layer expresses a different photoreceptor with distinct absorption spectra, however, this has only been tested for a single species. This means that previous research on salticid visual displays has only been able to make assumptions about what females are able to perceive when evaluating potential mates. Salticids of the Maratus genus are exceptionally sexually dimorphic, not only in their appearance, but also, male behavior wildly deviates from that of females in a signaling context. Thus, the proposed research is designed test if color vision exists for Maratus, based on the presence of different opsin genes, and/or optical and retinal characteristics. Furthermore, we will investigate whether variation in these properties has driven signal evolution and/or species diversity. Specifically, we will identify Maratus opsin genes and any pre-retinal filtering in the eye, as well as measure peak sensitivities and relative abundance of photoreceptors in the retina. These objectives will be accomplished through the use of bioinformatics and microspectrophotometry (MSP) methods. We expect that a successful evaluation of visual system evolution will present a major breakthrough for enabling future work on sensory evolution in jumping spiders, an exceptional yet understudied micro-fauna, as well as other animal groups.