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Offspring genetic structure reveals mating and nest infestation behaviour of an invasive parasitic fly (Philornis downsi) of Galápagos birds


The natural reproductive behaviour of invasive insects is pivotal knowledge for managing species of ecological or economic concern. We use microsatellites to examine female multiple mating and multiple nest infestations in the introduced parasitic fly, Philornis downsi, which causes high mortality in endemic birds on the Galápagos Islands. We analyse larvae and pupae within 57 nests from Santa Cruz and Floreana Islands in both the highland and lowland habitats. Sib-ship reconstructions of offspring revealed that up to five females may infest a single nest, while multiple mating in females was frequent (65% of reconstructed maternal genotypes), with an average of 1.91 (±0.06 SE) males per female. Genetic relatedness (R) of offspring within nests was generally low, though lowland nests on Floreana had higher R than highland nests. Knowledge of the reproductive behaviour of P. downsi is necessary for modelling appropriate management strategies, in particular, the sterile insect technique, for which success is greatly influenced by female multiple mating.

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We thank the Galápagos National Park Service and the Charles Darwin Research Station for the opportunity to work on the Galápagos Archipelago. We thank: Birgit Fessl, David Wiedenfeld, Carlos Vinueza, Gustavo Jiménez, Carlos Santos, Rebekah Christensen, Jody O’Connor, Katherine Goss and Jeremy Robertson for their dedicated field assistance and Kathy Saint for molecular technical advice. We thank the community of Floreana Island for their invaluable support throughout the project. TAME airlines provided reduced airfares to the Galápagos. This study was funded by a Flinders University Establishment Grant to SK, the Max Planck Institute for Ornithology, Galápagos Conservation Trust, American Bird Conservancy and Conservation International. We thank anonymous reviewers for helpful comments on previous versions of this manuscript.

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Correspondence to Sonia Kleindorfer.

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Dudaniec, R.Y., Gardner, M.G. & Kleindorfer, S. Offspring genetic structure reveals mating and nest infestation behaviour of an invasive parasitic fly (Philornis downsi) of Galápagos birds. Biol Invasions 12, 581–592 (2010).

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  • Philornis downsi
  • Darwin’s finches
  • Female multiple mating
  • Sterile insect technique
  • Ectoparasitism