Rare Butterflies: Tomares nesimachus and Apharitis cilissa

This research was conducted by Zohar Afek as part of her master’s degree in ecology under the supervision of Prof. Tamar Dayan and Dr. Orr Comay, at the Steinhardt Museum of Natural History and the School of Zoology, Tel Aviv University.

Abstract

The widespread decline reported in insects, including butterflies, is expected to have severe ecological and economic consequences. The Levantine Vernal Copper (Tomares nesimachus) and the Levantine Silverline (Cigaritis cilissa) are threatened butterflies in Israel. Some populations of these species have shown long-term declines in abundance, but the causes remain unknown.

This study examined whether there is a trend in the abundance of these butterfly populations across Israel (excluding C. cilissa in the Upper Galilee), and explored the relationship between abundance and various environmental factors. For each species, data from seven annual surveys—most conducted through citizen science—were used, spanning 18 years for T. nesimachus and 15 years for C. cilissa. A relative abundance index was calculated for each site in each survey.

A sharp decline in abundance was found for both species over time, alongside interannual fluctuations. T. nesimachus showed an average overall decline of approximately 90%, depending on temperature, while C. cilissa declined by about 95% in dry habitats and exhibited a non-significant ~40% decline in habitats enriched with surface water, such as seasonal pools. Populations of T. nesimachus declined more steeply with higher temperatures; under the most severe climate scenario, a 98% total decline was observed. The annual rate of decline in abundance for both species (13–20% for T. nesimachus, nearly 20% for C. cilissa) is much higher than the global insect decline rate (1–2%), raising concerns about their continued survival in Israel. T. nesimachus is expected to continue declining with rising temperatures, while C. cilissa is likely to be affected by ongoing climate drying.

The impacts of mitigation and adaptation policies will only be seen in the long term, while the current decline requires short-term solutions. Each species requires a network of suitable habitats within a landscape matrix that allows for dispersal. The rapid rate of open space loss in Israel highlights the importance of strengthening protections for the habitats of both butterflies. In addition, conserving C. cilissa depends on preserving and restoring wetland habitats in the Sharon region. Both species are likely influenced by additional factors; further research should investigate their microhabitat preferences, focusing on the quality of resources for immature life stages. Such knowledge would support the preservation of necessary conditions through dynamic management adapted to both interannual and long-term environmental changes.