Climate change and the effect of increasing spring temperatures on emergence dates of the butterfly Apatura iris (Lepidoptera: Nymphalidae)

Dennis Dell,Tim H Sparks,Roger L.H Dennis

doi:10.14411/eje.2005.026

Abstract

Data on pupation and emergence dates for the nymphalid Purple Emperor butterfly Apatura iris have been collected at Basel, Switzerland, between 1982 and 2002. The butterfly has been shown to emerge on average 9 (males) to 12 (females) days ear- lier per decade, 19 and 24 days earlier respectively over the study period. Emergence dates relate strongly to spring temperatures, particularly with daily maximum temperatures for the months March to May. Temperatures for these months have increased signifi- cantly during this period (0.7°C to 1.8°C per decade). Three factors suggest that the strongest influence of the rise in spring tempera- tures has been on late larval instar growth and development: (i) May temperatures dominate emergence date models and larvae are feeding faster and for longer periods during this month, (ii) Salix caprea flowering date, a surrogate for bud burst, is excluded in stepwise regression models with temperatures and years suggesting that tree phenology may be less important than temperature effects on later development, and (iii) convergence of female and male emergence dates over time points to limits on earlier feeding in protandrous males. A negative consequence observed with earlier emergence dates is lethal extra broods.

Highlights

Within recent years, long-term data sets have acquired an increasing importance owing to their potential value for tracking human-enhanced climatic changes (Houghton et al, 1996)
The data on adult emergence date for A. iris from Basel, Switzerland from 1982 to 2002 reveal a systematic advance in emergence dates for the butterfly coinciding with an increase in temperatures over this period
No influence of population numbers, or of numbers of A. iris being bred, was found; that is, there is no evidence of artefacts of increasing population size or sam

Summary

Introduction

Long-term data sets have acquired an increasing importance owing to their potential value for tracking human-enhanced climatic changes (Houghton et al, 1996). A wide range of effects to natural systems has been attributed to current climatic warming, including: advancement of bud burst, flowering, fruiting and nesting (Fitter et al, 1995; Lechowicz, 1995; Crick et al, 1997; Colombo, 1998) and changes to development rates, physiology, morphology and migration (Jenni & Kery, 2003; Dullinger et al, 2004). The impacts are far reaching, including latitudinal and altitudinal shifts in species ranges (Archaux, 2003; Cotton, 2003; Johnstone & Chapin, 2003) and with consequences for whole communities and ecosystems (Skre et al, 2002; Georges & Le Maho, 2003; Lemoine & Bohning-Gaese, 2003; Travis, 2003). Where long or medium term data exist they fulfil an important role in testing predictions and for building a composite picture of the impact of climatic changes on ecosystems (Harrington et al, 1999)

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