Investigation Of The Genetic Basis Of Temporal Variation Of Behaviors In The Hawaiian Swordtail Cricket Genus Laupala
In this dissertation I investigate the genetic basis of temporal variation among species of the cricket genus Laupala. Laupala species display interspecific variation in temporal characters on ultradian and circadian scales, allowing for comparative analyses of temporal variation. The species are primarily delineated by male song pulse rates and female pulse rate preferences. Interspecific variation has also been identified in the daily timing of singing and mating in wild-caught animals. Here I examine the interspecific differences in the daily timing of mating-related behaviors using lab reared L. cerasina and L. paranigra. Raising the species under environmentally homogeneous conditions demonstrated that differences in daily timing of mating-related activities and locomotion are genetically regulated. I examined the hypothesis that circadian variation underlies the daily timing differences and found a significant difference in the circadian free-running periods of singing between L. cerasina and L. paranigra. However, the difference was in the opposite direction than was expected, suggesting that either circadian variation is not sufficient to explain daily timing differences or that the association between circadian rhythms and daily timing is different in Laupala than in other taxa. Examining the circadian clock gene period, I found eight differences in the deduced amino acid sequence but no significant difference in the timing of transcript accumulation. Finally, to identify candidate genes for temporal song variation, I used suppressive subtractive hybridization to isolate differentially expressed gene transcripts between L. cerasina and L. eukolea. These sister species express substantially different song pulse rates (~2.4 pps and ~4.0 pps, respectively). I identified ten candidate genes and further characterized these genes by using qPCR to look for interspecific differential expression in the thoracic ganglia and head, regions involved in song regulation in crickets. All the genes showed differential transcript abundance in these regions, making them strong candidates for variation in song pulse rates. Having demonstrated a genetic basis to variation in timing and identified candidate genes for temporal variation provides a critical foundation for further efforts toward understand the genes and mechanisms underlying temporal variation in Laupala.
dissertation or thesis