A novel parasitoid and a declining butterfly: cause or coincidence?
Article first published online: 25 MAR 2011
© 2011 The Authors. Ecological Entomology © 2011 The Royal Entomological Society
Volume 36, Issue 3, pages 271–281, June 2011
How to Cite
GRIPENBERG, S., HAMER, N., BRERETON, T., ROY, D. B. and LEWIS, O. T. (2011), A novel parasitoid and a declining butterfly: cause or coincidence?. Ecological Entomology, 36: 271–281. doi: 10.1111/j.1365-2311.2011.01269.x
- Issue published online: 6 MAY 2011
- Article first published online: 25 MAR 2011
- Accepted 14 January 2011, First published online 25 March 2011
- non-native species;
- U.K. Butterfly monitoring scheme
1. The small tortoiseshell butterfly (Aglais urticae L.) is considered to be a widespread and abundant generalist species in Northern Europe. However, it declined sharply in the U.K. between 2003 and 2008, coinciding with the arrival and spread of a parasitoid, Sturmia bella Meig. (Diptera: Tachinidae), which specialises on nymphalid butterflies.
2. Whether the decline in A. urticae is associated with the arrival of S. bella was investigated using data from a large-scale butterfly monitoring scheme, and by collecting larvae to assess parasitoid incidence and parasitism frequency. Similar data were compiled for a related butterfly (Inachis io) which is also parasitised by S. bella but which is not declining.
3. Sturmia bella was recorded as far north as north Lincolnshire (53.53°N). Aglais urticae has declined significantly to the south of this latitude, but not to the north.
4. Sturmia bella was present in 26% and 15% of the larval groups of A. urticae and I. io, respectively, and now kills more individuals of A. urticae (but not I. io) than any native parasitoid.
5. Survival was 25–48% lower in batches of A. urticae larvae where S. bella was present, indicating that S. bella causes host mortality in addition to that caused by native parasitoids.
6. Our results suggest that S. bella may be playing a role in the recent decline of A. urticae. However, further research is needed to establish its effects relative to other potential drivers of trends in the abundance of this butterfly.