An Assessment of Species Diversity and Temporal Variation of Butterflies in Pinnawala Open Air Butterfly Park, Sri Lanka

Abstract

Butterflies (Lepidoptera) contribute to maintaining the health and diversity of ecosystems. Sri Lanka has nearly 248 species of butterflies, including 31 endemic species, and has established a series of conservation schemes, such as the Pinnawala Open-Air Butterfly Park, giving butterfly conservation an ex-situ environment. This study assessed butterfly species diversity and temporal variation in the park through comparison of species release reports by park management for 2019, 2022, and 2023 (no data between 2020-2021 because of the COVID19 pandemic). The data were supplemented through direct observation in the field and key informant interviews. Species diversity indices such as Shannon Diversity Index (H), Shannon Equitability Index (EH), Simpson Diversity Index (D), and Gini Simpson Index (G)—were calculated, and thematic analysis was conducted based on interview data. 7,388 individuals belonging to 20 species across four families (Papilionidae, Pieridae, Nymphalidae, and Lycaenidae) were tallied, of which Nymphalidae was the most species-rich. Evenness (EH = 0.85) and diversity (H = 2.34; D = 0.11) were highest in 2019, and richness was highest in 2023 (S = 20). The monthly trends indicated the lowest diversity in February and November, and the highest diversity in April, June and December. Season peak occurrence was correlated to mid-year environmental trends and effective management of the gardens, such as limiting temperature range variation as well as abundant nectar, water, and host plant supplies. It stresses the critical feature of routine upkeep in the parks towards the continued butterfly diversity. The enhancement of conservation and culture, as well as the introduction of new species on top of their rightful host vegetation, is recommended towards the optimization of the extent of ex-situ sites such as the Pinnawala Open-Air Butterfly Park towards enhanced biodiversity.