Enhancing nectar provision in vineyard habitats for the endemic New Zealand butterfly, Lycaena salustius

Nectar is an important factor influencing the level and persistence of butterfly populations, but particular sources of nectar may not be optimal for all species. In a farmland context, it is not always clear whether nectar sources used by butterflies are good quality species. They may be used opportunistically in the absence of true preferences, therefore possibly limiting maximal reproduction. This study investigated the use of nectar by adults of the endemic New Zealand butterfly, the common copper Lycaena salustius, in two ways: (1) a choice experiment in the field using a replicated design of different plant species, and (2) a greenhouse no-choice bioassay examining fitness enhancement by different flower species. In the field experiment, only Lycaena salustius males were observed in large numbers, and they spent a significantly longer time on flowers of Veronica ‘Youngii’ and Fagopyrum esculentum than on species already available in vineyards. In the laboratory, Veronica salicifolia and Fagopyrum esculentum flowers significantly enhanced the fitness of females over Achillea millefolium and the water control. These findings together imply that superior and preferred floral resources are not yet available to adult Lycaena salustius in vineyard landscapes. The no-choice greenhouse experiment suggests that the plant group with which the butterfly may have co-evolved is more beneficial than other exotic species, and that such plants could enhance populations in vineyards. The conservation of other butterfly populations in farmland and other ecosystems may benefit from similar investigations.