This summer, I had the pleasure of working with NSF-REU/PIPES intern Nadiatou Ouedraogo. Nadia is an undergraduate student majoring in Biology. For her internship, Nadia investigated body size variation of Spotted Wing Drosophila (SWD) in Hawai'i Island. SWD are invasive to many parts of the world, and Hawai'i is one of the first places they invaded outside of Asia. Given the amount of time that has elapsed since SWD colonized Hawai'i, we are in a prime position to study how this species has evolved to its new, tropical environment.
Body size variation has been identified to be a trait that can be measured in a rapidly invasive insect like SWD (Huey et al. 2000). Thus, Nadia wanted to determine if there were any body size differences in SWD populations across an elevation gradient. For her project, Nadia operated under the conceptual framework of the Temperature Size Rule in ectotherms (Walters & Hassall 2006), whereby insect body size can be predicted by temperature variability. She measured thorax length, wing length, and wing loading in both males and females from different elevation sites.
Elevation gradients are fantastic analogs of temperature variability, as there is a generalizable negative relationship between elevation and temperature (i.e., increasing elevation = decreasing temperature). Over the course of her ten week PIPES internship, we surveyed SWD on Mauna Loa and Kilauea Volcano, and were able to hike to some pretty cool places in search of flies. At the conclusion of her internship she gave a wonderful presentation of her project, which you watch on YouTube! One of her primary findings is that in Hawai'i, SWD individuals are significantly larger in body size at higher elevations relative to low elevation individuals.
Given our results, we aim to to continue our survey, and are collaborating with a student here at the University of Hawai'i at Hilo to investigate body size variation across seasons.
Our research is supported in part by a National Science Postdoctoral Fellowship to J. Koch (#1523661) and the National Science Foundation Research Experience for Undergraduates Site Program at the University of Hawai'i at Hilo. We also would like to thank Dr. Jesse Eiben and Marlena at the University of Hawai'i at Hilo College of Agriculture, Forestry, and Natural Resource Management for kindly providing us with a dissecting scope!
**This material is based upon work supported by the National Science Foundation under Grant Number #1523661. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.