The mechanisms by which reproductive isolation evolves and is maintained in adaptive radiations are central to understanding the fundamental processes of evolution. Particularly important are situations where ecologically distinct incipient sister species co-occur geographically, necessitating finely tuned recognition mechanisms for species to maintain reproductive isolation. Chemical cues are one of the most ancient and widespread modalities of communication, yet their importance in species recognition and reproductive isolation remains largely unknown. This project will focus on the role of chemical cues in reproductive isolation and speciation within an adaptive radiation of Hawaiian Tetragnatha spiders in which ecologically distinct sister species co-occur, and visual and auditory cues appear to play little or no role in species recognition during mating. By synthesizing techniques in chemical analysis and behavioral evaluations, this project will explore the role of chemical signaling as a mode of species recognition in an adaptive radiation.
Our work so far has shown that both Hawaiian and local California Tetragnatha spiders do indeed use chemical cues found on the silk of female and juvenile spiders to distinguish between species. This semester we will continue our work analyzing the chemical extracts we make from the silk of these spiders and map it onto the phylogeny of Tetragnatha spiders to better understand the evolution of chemical cues. This can be done completely online and only continuing students with prior experience working in the lab will work on the extractions in-person. All other students will do the chemical analysis online. We will also conduct 2-choice behavioral trials in-person using the olfactometer to better understand the difference between olfactory and gustatory chemical cues (again, this is only for continuing students who have prior experience working with spiders). The in-person lab work will involve closely working with and handling the spiders for feeding and running the experimental trials, handling their prey items, working with chemicals, and using other equipment in the lab. The online lab work will involve working with chemical analysis software such as OpenChrom, AMDIS, and Chemdraw.
Lastly, in the past students who have worked on this project and have showed great interest in conducting research have continued to form and conduct independent research projects of their own. New students who will be joining this lab will have the opportunity to not only take part in these other projects but also create and conduct research of their own if they choose to do so. In the past we have had students travel to Hawaii to conduct research in the field looking at the effects of invasive ginger plants on the native Hawaiian arthropod community, the evolution of leg spines in the Hawaiian spiny-legged Tetragnatha spiders, the role of venom in mating behavior, and the evolution of web-loss in Tetragnatha spiders. We always encourage and welcome students to work on independent projects and would be happy to brainstorm research ideas with you!
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Undergraduates that take part in this project will be exposed to working on a variety of methods in chemical ecology, behavioral biology, evolutionary ecology, and genomics. If they are continuing students who wish to work in-person, they will conduct behavioral assays using differing setups of a 2-choice preference test, extract spider pheromones using various chemical techniques, analyze chemical extracts using a gas chromatography – mass spectrometry (GCMS), extract, amplify, and quantify DNA, and sort specimens for genomic work using a dissecting microscope. If the student is working online, students will conduct chemical and video analysis work completely online. Students who will be working in-person will also partake in the husbandry of spiders, which include tasks such as feeding, tracking of development, and maintenance of food supply colonies (including drosophila, Plodia moths, and Culex mosquitos).
Undergraduates must first be interested in topics such as evolution, speciation, animal behavior, chemical ecology, and island biology. Undergraduates should also be thoroughly comfortable handling and working with live animals (specifically the arthropods listed above). The work deals with very small and delicate organisms so the student must be extra careful, attentive, and meticulous with their work and ready to learn at all times. Furthermore, due to the limited activity schedule of the spiders, undergraduates will need to be available for work sometime between 12pm to 7pm if working in-person (this is when the spiders become active and when the behavioral research is conducted), but it working online, they can work whenever works best for their schedule.