Data set for the publication 'Invasive fly species displaces natives in Galapagos with implications for biological control risk assessment'

Abstract

The composition and interactions of carrion flies in the Galapagos Islands is poorly understood, especially when focusing on competition between introduced and endemic fly species. We aimed to assess such composition and interactions by deploying carrion bait traps during the cool and hot seasons, and an experimental approach in a controlled setting was used to investigate interspecific competition among them. Of the eight fly species found in our baited traps, all were introduced except for the endemic sarcophagid, Sarothromyiops dasycnemis (Thomson), and a number of endemic species expected to be encountered were not found. The introduced sarcophagid, Peckia chrysostoma (Wiedemann) was the most abundant fly species found overall, comprising over half of the collected specimens. Most fly species exhibited some level of habitat preference. We conducted a laboratory experiment on resource competition between P. chrysostoma and a subset of the fly species encountered in the baiting study. The results demonstrated that P. chrysostoma is a strong competitor against other carrion fly species in the Galapagos necrobiome, including the endemic S. dasycnemis. A comparison of our data to historical records of fly abundance in Galapagos, combined with the results of our laboratory study, leads to the conclusion that introduced carrion fly species such as P. chrysostoma represent a threat to endemic carrion fly species, such as S. dasycnemis. Three parasitoid species were reared from the puparia collected, two that attacked fly larvae (Brachymeria podagrica and Aphaereta sp.) and one that attacked puparia (Exoristobia sp.). We discuss our results in light of the possibility of the purposeful introduction of a hymenopteran parasitoid as a biological control agent against the avian vampire fly (Philornis downsi Dodge & Aitken) in Galapagos.