Behavioral Responses of the Invasive Fly Philornis downsi to Stimuli from Bacteria and Yeast in the Laboratory and the Field in the Galapagos Islands.

Boaz Yuval,Polpass Arul Jose,Michael Ben-Yosef,Paola Lahuatte,Edouard Jurkevitch,Nikos Kouloussis,Charlotte E Causton

doi:10.3390/insects10120431

Abstract

Philornis downsi Dodge and Aitken (Diptera: Muscidae) is an avian parasitic fly that has invaded the Galapagos archipelago and exerts an onerous burden on populations of endemic land birds. As part of an ongoing effort to develop tools for the integrated management of this fly, our objective was to determine its long- and short-range responses to bacterial and fungal cues associated with adult P. downsi. We hypothesized that the bacterial and fungal communities would elicit attraction at distance through volatiles, and appetitive responses upon contact. Accordingly, we amplified bacteria from guts of adult field-caught flies and from bird feces, and yeasts from fermenting papaya juice (a known attractant of P. downsi), on selective growth media, and assayed the response of flies to these microbes or their exudates. In the field, we baited traps with bacteria or yeast and monitored adult fly attraction. In the laboratory, we used the proboscis extension response (PER) to determine the sensitivity of males and females to tarsal contact with bacteria or yeast. Long range trapping efforts yielded two female flies over 112 trap-nights (attracted by bacteria from bird feces and from the gut of adult flies). In the laboratory, tarsal contact with stimuli from gut bacteria elicited significantly more responses than did yeast stimuli. We discuss the significance of these findings in context with other studies in the field and identify targets for future work.

Highlights

Philornis downsi Dodge and Aitken, 1968 (Diptera: Muscidae) is an avian nest parasitic fly that invaded the Galapagos archipelago in the latter half of the twentieth century [1,2,3,4]
This community structure differed from the bacteria acquired on agar plates inoculated with finch feces (MRPP test, A = 0.228, p = 0.001 after Bonferroni correction)
The response to sucrose at the end of the test unequivocally shows that all flies were motivated to ingest food, and the exclusion of flies responding to phosphate buffered saline (PBS) assures us that the responses we considered were specific to the test stimuli

Summary

Introduction

Philornis downsi Dodge and Aitken, 1968 (Diptera: Muscidae) is an avian nest parasitic fly that invaded the Galapagos archipelago in the latter half of the twentieth century [1,2,3,4]. The broad host range of these flies, lack of competitors and natural enemies, and their high dispersal ability and adaptability to harsh environments have all contributed to their successful invasion [2]. This success is manifest in the impact on the local passerines. Since P. downsi was first observed in 1997 [6], most the passerines on the islands have been recorded as hosts [2]

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