The Pieris napi/bryoniae hybrid zone at Pont de Nant, Switzerland: broad overlap in the range of suitable host plants
1997
Porter, A.H.
The butterflies Pieris napi and Pieris bryoniae hybridize in a narrow zone at approximately 1200 m in the Alps and Carpathians of Europe. They feed as larvae on a variety of hosts in the Brassicaceae, and few host species occur on both sides of the hybrid zone. Females were captured on either side of the hybrid zone at Pont de Nant, Switzerland, eggs obtained, and larvae were offered plants from nineteen species of Brassicaceae and Reseda lutea (Resedaceae). Nine of the hosts were found to have eggs or larvae already on them. Only Capsella bursa-pastoris and R. lutea were unsuitable. Significant survivorship differences among suitable hosts were found. There was no interaction between butterfly species and host plant, which would indicate adaptation by these taxa to their respective suites of hosts. Among suitable hosts, larvae of both taxa had higher mortality on plants with hairy leaves and on older plants beginning to senesce. Differential selection on host use, if it occurs at all, is likely to be a very minor factor in the dynamics of the Pieris napi/bryoniae hybrid zone.
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