Asymmetric Migration Shapes Genetic Structure of the Invasive Avian Vampire Fly (Philornis downsi) Across the Galápagos Islands
8 affiliations
- 1School of Natural Sciences Macquarie University Sydney New South Wales Australia
- 2Konrad Lorenz Research Center for Behavior and Cognition, Core Facility of the University of Vienna Vienna Austria
- 3Department of Behavioral and Cognitive Biology University of Vienna Vienna Austria
- 4Department of Biological Sciences Northern Illinois University De Kalb Illinois USA
- 5Department of Entomology University of Minnesota St. Paul Minnesota USA
- 6National Institute of Biodiversity (INABIO) Quito Ecuador
- 7Department of Ecology and Evolutionary Biology University of Connecticut Storrs Connecticut USA
- 8Charles Darwin Research Station Charles Darwin Foundation Santa Cruz Galápagos Islands Ecuador
Abstract
Biological invasions on islands provide a natural framework to study how dispersal and connectivity influence evolutionary and ecological processes. The avian nest parasitic fly, Philornis downsi—first recorded in Darwin's finch nests in 1997—causes high mortality in endemic land birds, yet its inter‐island and sex‐specific patterns of dispersal and genetic structure remain poorly understood. We use low‐coverage whole genome sequencing to investigate genome‐wide patterns of genetic diversity, directional migration and effective population size in P. downsi across five major Galápagos Islands and its native range in mainland Ecuador. We find evidence for a genetic bottleneck in the Galápagos, isolation by distance, and evidence that the island closest to the Ecuadorian mainland, San Cristóbal, is genetically divergent from the other four islands sampled, despite retaining the highest genetic diversity. No evidence was found for sex‐biased dispersal; however, sex‐biased genetic structure was detected using only markers from inferred autosomal scaffolds. We found asymmetric gene flow with higher migration rates from San Cristóbal westward to the other islands, matching the direction of both southeast trade winds and major cargo shipping routes. Our results suggest both natural and human‐mediated colonisation of P. downsi from the mainland through San Cristóbal to the other islands, followed by high inter‐island dispersal among closely situated sink islands. Our findings are critical for prioritising islands for control strategies that will reduce P. downsi impacts on vulnerable endemic birds and underscore the value of understanding directional migration patterns for managing invasive species in metapopulations.
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BibTeX
@article{hay2026asymmetric,
title = {{Asymmetric Migration Shapes Genetic Structure of the Invasive Avian Vampire Fly (Philornis downsi) Across the Galápagos Islands}},
author = {Abbie C. Hay and Sonia Kleindorfer and Lauren K. Common and Sally Potter and Jennifer A. H. Koop and George E. Heimpel and Sarah A. Knutie and Birgit Fessl and Lorraine Pérez‐Beauchamp and Rachael Y. Dudaniec},
journal = {Molecular ecology},
year = {2026},
month = oct,
doi = {10.1111/mec.70606},
url = {https://europepmc.org/article/PMC/PMC13722943},
note = {CC BY-NC},
}
RIS
TY - JOUR
TI - Asymmetric Migration Shapes Genetic Structure of the Invasive Avian Vampire Fly (Philornis downsi) Across the Galápagos Islands
AU - Abbie C. Hay
AU - Sonia Kleindorfer
AU - Lauren K. Common
AU - Sally Potter
AU - Jennifer A. H. Koop
AU - George E. Heimpel
AU - Sarah A. Knutie
AU - Birgit Fessl
AU - Lorraine Pérez‐Beauchamp
AU - Rachael Y. Dudaniec
PY - 2026
DA - 2026/10/30
JO - Molecular ecology
DO - 10.1111/mec.70606
UR - https://europepmc.org/article/PMC/PMC13722943
AB - Biological invasions on islands provide a natural framework to study how dispersal and connectivity influence evolutionary and ecological processes. The avian nest parasitic fly, Philornis downsi—first recorded in Darwin's finch nests in 1997—causes high mortality in endemic land birds, yet its inter‐island and sex‐specific patterns of dispersal and genetic structure remain poorly understood. We use low‐coverage whole genome sequencing to investigate genome‐wide patterns of genetic diversity, directional migration and effective population size in P. downsi across five major Galápagos Islands and its native range in mainland Ecuador. We find evidence for a genetic bottleneck in the Galápagos, isolation by distance, and evidence that the island closest to the Ecuadorian mainland, San Cristóbal, is genetically divergent from the other four islands sampled, despite retaining the highest genetic diversity. No evidence was found for sex‐biased dispersal; however, sex‐biased genetic structure was detected using only markers from inferred autosomal scaffolds. We found asymmetric gene flow with higher migration rates from San Cristóbal westward to the other islands, matching the direction of both southeast trade winds and major cargo shipping routes. Our results suggest both natural and human‐mediated colonisation of P. downsi from the mainland through San Cristóbal to the other islands, followed by high inter‐island dispersal among closely situated sink islands. Our findings are critical for prioritising islands for control strategies that will reduce P. downsi impacts on vulnerable endemic birds and underscore the value of understanding directional migration patterns for managing invasive species in metapopulations.
SN - 0962-1083
SN - 1365-294X
ER -