Submitted by Rosemary Gillespie on
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 species recognition 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.
In Fall of 2015, we gathered data to support the existence of female pheromones and male attraction to these pheromones. In Spring of 2016, we discovered that Tetragnatha extensa males could distinguish between con- and hetero-specific females just by using the chemicals found on the silk of the female spiders’ web. In Fall 2016, we continued to expand on these discoveries and found that many species from both the Hawaiian and Californian Tetragnatha spiders could distinguish between con- and hetero-specific females by using dragline silk (a different kind of silk). In Spring of 2017, we combined the two studies and explored the use of both dragline and web silk in species recognition using both Hawaiian and Californian spiders.
This summer we hope to chemically extract the attractive compounds found on both the dragline and web silk of the different Tetragnatha species (students will be working with over 10 different species of Tetragantha spiders from Hawaii, California, and Japan) to run bioassay tests to confirm the behavioral response of these chemicals, as well as further analyze and identify the compounds responsible for the attractive behavioral response.
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Undergraduates that take part in this project will be exposed to working on a variety of methods in chemical ecology and behavioral biology. They will conduct behavioral assays using differing setups of a 2-choice preference test, score video recordings of these trials, extract spider pheromones using various chemical techniques, and analyze chemical extracts using a gas chromatography – mass spectrometry (GCMS). Students 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). Furthermore, if applicable, students will have an opportunity to gain field experience conducting behavioral observations and collecting specimens at local UC Reserves and on campus.
In the past, students who have worked on this project showing interest in research have continued to form and conduct independent research projects of their own to work both in Hawaii and California. Students who work on this project and find that they are interested in conducting their own research are encouraged and welcomed to work closely with the lead graduate advisor (Seira Ashley Adams) to brainstorm research ideas and apply for funding for their own projects.
Undergraduates must 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 (this is when the spiders become active and when the behavioral research is conducted).