The avian vampire fly, Philornis downsi: A parasite’s perspective of co-evolutionary dynamics

Author: Lauren Common

Common, Lauren, 2023 The avian vampire fly, Philornis downsi: A parasite’s perspective of co-evolutionary dynamics, Flinders University, College of Science and Engineering

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Invasive species, particularly parasites and pathogens, are an increasing threat to human, animal, and ecosystem health. Although the impacts of invasive parasites on their novel hosts and environment are often known, less is understood about how invasive parasites are affected by invasion. This study explores changes in the accidentally introduced avian vampire fly, Philornis downsi, since its 1997 discovery in the nests of Darwin’s finches on the Galápagos Islands.

Utilising a long-term dataset across multiple host species, this study explores changes in reproductive behaviour (Chapter 2 & 6), morphology (Chapter 3), mortality (Chapter 4), adult behaviour (Chapter 5) and genetic structure (Chapter 6). Coincident with decreasing body size across decades, P. downsi reproductive behaviour has changed. Females are now mating with fewer males, ovipositing earlier in the nesting cycle, and ovipositing fewer eggs per nest. Across time, patterns of intensity and mortality in P. downsi differ between host species, a potential precursor to host-specificity. Low genetic differentiation across time suggests that P. downsi populations on Floreana Island are not genetically isolated from other island populations. Despite this, island-specific patterns of adult P. downsi spatial and temporal abundance highlight the need to understand each island as a separate system, to ensure the success of targeted control techniques.

The use of long-term datasets and a combination of techniques has given unparalleled insight into change in a wild, dynamic host-parasite system. Under extreme selection pressures, P. downsi behaviour, genetics and patterns of host association have shifted across time. The results of this study present recommendations for the management of P. downsi populations and the conservation of avifauna of the Galápagos Islands.

Keywords: parasitology, host-parasite dynamics, Galapagos, darwin's finches, evolution

Subject: Biological Sciences thesis

Thesis type: Doctor of Philosophy
Completed: 2023
School: College of Science and Engineering
Supervisor: Sonia Kleindorfer