Habitat choice precedes host plant choice - niche separation in a species pair of a generalist and a specialist butterfly

• Published in: Oikos 2008-09, Vol.117 (9), p.1337-1344
• Main Authors: Friberg, Magne, Olofsson, Martin, Berger, David, Karlsson, Bengt, Wiklund, Christer
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; Autoecology; Biogeography; Biological and medical sciences; Botany; Butterflies & moths; Ecology; Fundamental and applied biological sciences. Psychology; Habitats; Insecta; Invertebrates; Lathyrus pratensis; Leptidea reali; Protozoa. Invertebrata; Sinapis
• ISSN: 0030-1299; 1600-0706
• DOI: 10.1111/j.0030-1299.2008.16740.x

The sister species Leptidea reali and L. sinapis have partitioned their niches differently in different parts of their sympatric distribution. In Spain and France L. sinapis is a widespread generalist whereas L. reali is specialized on high altitude open areas. Interestingly, the reverse is true in Ireland and the Czech Republic where L. reali is widespread and L. sinapis specialized on meadows. In Sweden, L. reali is a habitat specialist confined to meadows, whereas L. sinapis is a habitat generalist also inhabiting forests. Ultimately, the geographic mosaic of niche separation is the result of local processes in each contact zone or a secondary effect of the host plant distribution, if L. sinapis and L. reali prefer different legume host plants. Hence, in Sweden L. sinapis might utilize the forest habitat either due to a wider habitat preference or due to a wider host plant preference than L. reali. Studies of wild butterflies showed that L. sinapis laid 26% of their eggs on forest-associated legumes compared to 6% in L. reali, although laboratory experiments showed that both species had virtually identical host plant preferences strongly preferring the meadow-associated legume Lathyrus pratensis. Furthermore, flight duration tests in a variety of temperatures demonstrated a between-species difference; L. sinapis females reached their flight optimum at a lower temperature than L. reali females. The lower L. sinapis flight temperature optimum is most probably a secondary effect due to habitat-specific selection, and therefore a consequence rather than the cause of the habitat partitioning. The finding that habitat choice precedes host plant choice suggests that the European geographic mosaic of niche separation, with L. sinapis and L. reali shifting habitat specialist/generalist roles, is not caused by rigid between-species differences in a related niche parameter, but instead is a result of local processes within each secondary contact zone.