Dissertation Research: Linking Broad-Scale Genetic Variation and Local Selection on Sexual Signals: Loss of Calling in a Parasitized Population of Field Crickets

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This research will examine how signals used to attract mates are affected by, gradual genetic changes as a species colonizes new areas, and are punctuated by more drastic changes due to selection in new environments, using a field cricket as a model organism. The cricket, Teleogryllus oceanicus, is found in Australia and on many Pacific islands and was introduced to Hawaii where it encounters a deadly enemy, a parasitic fly. The fly is attracted to the mating signal (song) male crickets produce by rubbing their wings together. Recently, a striking change was noted in Hawaii. In one Hawaiian population, but not others, 90% of males shifted from normal wing morphology to a non-functional, mutated wing in just tens of generations. These males are protected from the fly because they cannot produce song. This research will identify the importance of gradual genetic divergence associated with range expansion, island colonization and movement between islands for the distribution of genetic variation among populations. Variation in the key genetic sequences among 12 cricket populations with known variation in song and signaling behavior among the same populations will be examined with respect to implications for long-term genetic change. Islands are usually only colonized by a few animals at a time and this is thought to favor females that are less picky in mate choice, so these historical events are likely to affect mating preferences as well. Second, this research will determine what behavioral changes accompany the recent and rapid loss of the crickets sexual signal, song. This will be accomplished by staging mating encounters between mainland Australian and island populations of the cricket, including those in which the ability to call has been lost. Intellectual merit: This research links the influences of long-term, historical processes with short-term local selection on sexual signals. It will contribute to our understanding of the way parasites influence mating systems and will add to our understanding of the mode and tempo of signal evolution. Broader impacts: The loss of cricket song is a striking and easily understood example of everyday evolution that can be comprehended by students of all levels (grade school to undergraduate) and non-scientists as well. This example, because of its relative simplicity and recent time frame, will advance the publics understanding of evolutionary processes and be used as an educational tool. Additionally, this project will add to undergraduate scholarship at UCR. The PIs mentor undergraduate students and will continue to include them in the behavioral aspects of this project.