Background/Question/Methods
The fields of ecological immunology and plant-microbe-insect interactions are both relatively new areas of research, yet they hold great potential to inform our knowledge of coevolution, integrated pest management, and the relationship between the microbiome and human health. We still know relatively little about how the immune system is regulated in natural systems, and even less about the interplay between immune response, the microbiome, and nutritional limitations in non-model organisms. In this project, I examined different components of ecological variation and their effects on the immune response of a tropical specialist moth, Utethesia ornatrix, also known as the Bella moth or Ornate moth. This specialist insect consumes plants in the genus Crotalaria, and utilizes both native and exotic plant species in its native range. I collected U. ornatrix moths in its native range of Brazil and reared larvae on two Crotalaria species: C. pallida (exotic) and C. incana (native). For each host plant, larvae were reared either on leaves alone, or leaves plus seed pods. In the wild, larvae consume both parts of the plant, however, seed pods contain much higher levels of alkaloids, an important compound class which is sequestered by larvae for defense. These treatments effectively represented two categorical groups for each host plant (high alkaloids vs. low alkaloids). After larvae reached 4th instar, I measured their constitutive and induced immune response. Finally, I extracted larvae for their DNA and used metagenomics sequencing to describe the microbial communities for larvae in each treatment group.
Results/Conclusions
Preliminary results suggest that larvae had higher levels of constitutive immunity (as measured by phenoloxidase) on the native host plant (C. incana) compared to the exotic host plant (C. pallida). This result is consistent with previous work on other lepidopteran species in temperate climates, suggesting that native host plants are typically higher quality resources when it comes to immunity. In addition, larvae fed leaves plus seeds (high alkaloids) versus only leaves (low alkaloids) did not differ significantly in immune strength, suggesting chemical sequestration does not tradeoff with immunity in this species.