LB 10-132 - CANCELLED - Rearing substrates of Galapagos Diptera: a natural history study

Thursday, August 18, 2022

5:00 PM – 6:30 PM EDT

Located in: ESA Exhibit Hall

Presenting Author(s)

CL

Charles Lehnen

PhD Student
University of Southern California, United States

Coauthor(s)

GH

George Heimpel, PhD

Distinguished McKnight University Professor
University of Minnesota, United States
CC

Charlotte Causton, PhD

Project Coordinator of Invasive Invertebrates
Charles Darwin Foundation, Ecuador
BS

Bradley Sinclair, PhD

Canadian National Collection of Insects, Arachnids & Nematodes, Canada

Background/Question/Methods:

The invasive vampire fly Philornis downsi is threatening the survival of multiple endemic species of the Galapagos Archipelago, including critically endangered species of Darwin’s finches. Understanding the ecology of Galapagos Diptera is a mandatory step in estimating impacts of P. downsi control prospects and acquiring endemic pupae for biocontrol agent non-target testing. However, prior to this research study, the community ecology and rearing substrates of Galapagos Diptera had been virtually unknown. Rearing traps (n=137) containing various substrates (71 in total) were placed in the field at substrate collection points across the six primary vegetation zones of five islands across three field seasons (Summer 2016, 2018, 2019). Substrates were targeted based on their likelihood as sources of endemic/native cylorraphan Diptera based on historical data and natural history of closely related species. Following substrate colonization periods, traps were isolated from further colonization. Rearing traps were specially designed to minimize the opportunity for reared adults within traps to utilize the substrate for reproduction while preventing contamination into the isolated traps by external Diptera. Isolated traps were stored, with emergent adults collected and preserved in ethylene glycol. Each specimen was collected, stored in 70-75% ethanol, and identified.

Results/Conclusions:

This comprehensive natural history study illuminated dozens of novel interspecies associations. Of note, rearing sources of six endemic or likely endemic along with two native or likely native dipteran species were identified. Of these, four endemic and two likely native Diptera are cyclorrhaphan, a particularly important group for non-target testing due to developmental similarities to P. downsi. 17 species within 13 genera not previously recorded in the Galapagos Islands were confirmed. Five of these species are within genera not previously recorded on the Archipelago. One of these 17 species from the family Sarcophagidae, represented by a single damaged male specimen, was unidentifiable to genus and is currently under review by specialists. Two species suspected to be new to science were discovered. Both are in the genus Sciophila (Sciaridae). Lastly, a novel parasitic interaction between the tachinid fly Drino inca and the native sphingid lepidopteran Agrius cingulata was recorded. The pending publication of these results in summer 2022 will directly inform the ongoing, time-sensitive ecological safety studies of potential biocontrol agents for P. downsi. Beyond the contribution of this knowledge to the general understanding of Galapagos ecosystems, these results improve our understanding of plant-insect interactions as well as community composition.