By Kip Will (Associate Professor, UCB) and Joo Hee Park (Undergraduate working on CalBug)
Although the focus of most images is on the labels so that volunteers can transcribe them, in some cases we take a good, standard image of the insect to be used in studies of body shape. Together with location information transcribed by NfN volunteers, we can do geometric morphometric studies. These studies use methods that analyze shapes and provide mathematical descriptions of body form.
You can look at images of male and female insects and between individuals of the same or different species, and see variation in overall size or relative proportions, such as the size of the head as compared to the abdomen. You already know from looking at people and other familiar non-human animals like dogs, there is a lot of variation out there. We think that understanding variation is a very powerful way to answer questions about how organisms interact and species evolve.
For one group of insects you can see on NfN, ground beetles (Carabidae), entomologists have long-noted that there were distinct differences in shape and size within, and between, species. In our research project, we apply this idea and use powerful geometric morphometric statistics to examine patterns of variation across geographic regions for several species of Pterostichus. Transcriptions of localities by volunteers help us place those specimens in their distributions. Specifically we are examining whether there is a statistical difference in pronotal* shape across various Pterostichus species, and whether there is a statistical difference in overall body size and pronotal shape with respect to sex.
JOO HEE PARK’S UNDERGRADUATE STUDENT EXPERIENCE: Working on a hands-on research project like CalBug’s study of shape in Pterostichus has been an invaluable experience for me as an undergraduate.
Coming to work with Professor Will seemed very daunting, but he patiently introduced concepts that were very new to me and I was soon excited to discover that I was able to contribute to the research. Tasks related to the project were not easy at first, and one of the hardest things was to admit when I didn’t understand something, and to ask for help. In science, as long as you are motivated, honest, and hardworking, everything works out in the end. Discoveries may be large or small, but it is always very satisfying. One of the things I liked most was being out in the fields collecting specimens and being able to follow that through to the very end: writing a paper presenting our results (coming soon!). It is a great opportunity to have a full experience of doing research, and I feel very privileged to have been given this opportunity.
Doing science is enjoyable and exciting every step from first to last: collecting specimens, preparing and pinning specimens, taking images, working with morphometrics programs, and analyzing the data. I am learning a lot about the overall process of science, but the best part is forming relationships with scientists and fellow students along the way.
SOME PRELIMINARY RESULTS: Although our study in still preliminary we have noticed that one species, Pterostichus lama, has significantly larger males than females, which is opposite of the most common case in insects where females are the larger sex, and that specimens of Pterostichus lama found in the Sierra Range of California are larger than those in the coastal range. We suspect that the size difference between the two mountain ranges is due to interaction between this species and other beetles they live with [see KW’s earlier post on this] .
We have more work to do before the questions raised by the patterns can be answered with certainty. The specimen data transcribed by volunteers at NfN will be a big help as the project continues. Thanks!
*The pronotum is the first section of the thorax, just behind the head on dorsal side of the beetle.