The Rare Butterfly Tomares Nesimachus (Lycaenidae) as a Bioindicator for Pollination Services and Ecosystem Functioning in Northern Israel

Abstract

Evidence suggests that insects whose existence depends on fruit production may serve as good bioindicators, especially for pollination services. In this study we examined this hypothesis, focusing on one of Israel's rarest butterflies, Tomares nesimachus (Rhopalocera; Lycaenidae). The butterfly is affiliated with open grasslands in the north of Israel, where its sole host plant, Astragalus macrocarpus, occurs. In a two-year field study, we mapped the distribution of the butterfly in Israel and tried to evaluate the causes of its rarity and decline. We found that its abundance in habitat patches was correlated with several factors, including (a) fruit production of the host plants in each patch, (b) the number of other patches in the vicinity, (c) the characteristics of the "matrix" outside the patches within a distance of up to 2 km, (d) the richness of large bee species (the plant pollinators), and (e) the grazing management of the butterfly's habitat. The characteristics of the matrix further affected the richness of bees in the butterfly's habitat. Since butterfly abundance is correlated with species richness of pollinators, it can serve as an indicator of diverse, species-rich butterfly habitats (grasslands). We deduce that species that depend on fruit production and by themselves do not contribute to their host-plant pollination, may almost necessarily be affected by multiple ecological factors and therefore can indeed serve as good indicators. Our results further indicate that the butterfly's population dynamics are affected by large-scale processes, and hence its conservation requires the preservation of large open landscapes. Consequently, T. nesimachus may also serve as an umbrella species.

Keywords:

• butterflies
• bioindicator
• umbrella species
• pollination service
• eco-system functioning
• grasslands
• grazing management
• Tomares nesimachus