Oviposition preferences indicate a wide range of host plant species in two regionally declining butterfly species

Different host plants may vary in their effects on butterfly larvae or adult performance, with possibly pervasive consequences for the viability of local populations. Understanding host plant preferences is therefore crucial for butterfly conservation. Lycaena phlaeas and L. tityrus are rather widespread butterflies in Central Europe. They though recently declined in several regions. Both Lycaena species use Rumex species as host plants, with so far unknown preferences within this genus. We investigated oviposition preferences of both butterfly species in a simultaneous choice experiment, considering five to six Rumex species (R. acetosa,R. acetosella,R. crispus, R. obtusifolius, R. thyrsiflorus, and in L. phlaeas additionally R. sanguineus). Oviposition proportions of both Lycaena species differed among Rumex species. Rumex acetosella was avoided, while all other species were utilized quite evenly. This finding suggests that all tested Rumex species are generally suitable host plants. The wide host plant range likely reflects a risk-spreading strategy, as females are limited in their ability to identify highly suitable plants for their larvae.