Oviposition site selection of the Alcon blue butterfly at the northern range margin

• Published in: Journal of insect conservation 2016-12, Vol.20 (6), p.1059-1067
• Main Authors: Vilbas, Margus, Esperk, Toomas, Edovald, Triin, Kaasik, Ants, Teder, Tiit
• Format: Article
• Language: English
• Subjects: Animal Ecology; Animal populations; Animal reproduction; Biodiversity; Biomedical and Life Sciences; Butterflies & moths; Conservation Biology/Ecology; Conspecifics; Eggs; Entomology; Gentiana cruciata; Habitats; Herbivores; Host plants; Lepidoptera; Life Sciences; Lycaenidae; Microclimate; Offspring; Original Paper; Plants; Site selection; Vegetation
• ISSN: 1366-638X; 1572-9753
• DOI: 10.1007/s10841-016-9939-x

Female oviposition decisions in insects may strongly affect offspring growth and survival, and thus determine population performance. In this study, we examined oviposition site selection in the xerophilous ecotype of the endangered myrmecophilous butterfly Phengaris (= Maculinea ) alcon (Lepidoptera, Lycaenidae) in Estonia, at the northern distribution margin of both the butterfly and its host plant, Gentiana cruciata L. Egg distribution on individual host plants appeared to be highly uneven: plants carrying high egg loads contrasted to a high proportion of host plants without any or with a few eggs. Host plant use for oviposition was strongly dependent on plant characteristics and environmental context. Host plant height relative to the surrounding vegetation rather than the absolute height of host plants was a key factor determining the use of particular host plant individuals for oviposition. In particular, plants protruding above surrounding vegetation had a higher probability of being used for oviposition, and carried more eggs. Additionally, the number of eggs laid on individual host plants was positively associated with the presence of flowers and the number of shoots. More aggregated host plants received fewer eggs than those with less conspecifics around. Feeding damage by wild herbivores, found in a substantial proportion of the butterfly’s host plants, strongly reduced the number of eggs on individual plants. Our results underline the need to assure that butterfly’s host plants do not become overgrown by surrounding vegetation. Best practices for opening vegetation around host plants may need further studies that explicitly account for butterfly’s host ants—their abundance in relation to vegetation height and their response to opening vegetation.