Extinction-colonization dynamics and host-plant choice in butterfly metapopulations.
Species living in highly fragmented landscapes often occur as metapopulations with frequent population turnover. Turnover rate is known to depend on ecological factors, such as population size and connectivity, but it may also be influenced by the phenotypic and genotypic composition of populations. The Glanville fritillary butterfly (Melitaea cinxia) in Finland uses two host-plant species that vary in their relative abundances among distinct habitat patches (dry meadows) in a large network of approximately 1,700 patches. We found no effect of host species use on local extinction. In contrast, population establishment was strongly influenced by the match between the host species composition of an empty habitat patch and the relative host use by larvae in previous years in the habitat patches that were well connected to the target patch. This "colonization effect" could be due to spatially variable plant acceptability or resistance or to spatially variable insect oviposition preference or larval performance. We show that spatial variation in adult oviposition preference occurs at the relevant spatial scale and that the other possible causes of the colonization effect can be discounted. We conclude that the colonization effect is generated by host preference influencing the movement patterns of ovipositing females. Migrant females with dissimilar host preferences have different perceptions of relative patch quality, which influences their likelihood of colonizing patches with particular host composition.
Hanski
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Metapopulation Research Group, Department of Ecology and Systematics, P.O. Box 17 (Arkadiankatu 7), University of Helsinki, FIN-00014 Helsinki, Finland. ilkka.hanski@helsinki.fi
Singer
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MC