Seasonal Variation of Forest Butterfly Diversity in Tropical Lowland Nepal

Butterfly populations and diversity vary with the seasons due to bioclimatic factors, particularly precipitation and temperature. Their seasonality in the tropical region of Nepal has not been well studied, and climatic factors have yet to be incorporated into research. Hence, this study examined the seasonal variation of forest butterfly diversity, community composition, and the effect of precipitation and temperature on diversity in the tropical lowland of Nepal. Butterflies were sampled for a year using Pollard Walk and checklist methods. Different forms of diversity indices, similarity/dissimilarity, and indicator species analysis were performed using data from the Pollard Walk. Generalized Linear Mixed Models were employed to assess the effect of precipitation and temperature on species richness and abundance. Data from the checklist method was utilized to account for the overall species richness. A total of 115 butterfly species from six families were documented. The diversity and community composition varied significantly between the seasons, with two seasonal peaks of richness: pre-monsoon and post-monsoon. Species richness and abundance also varied significantly among the families. Species such as Euthalia aconthea, Hypolimnas misippus, Jamides celeno, and Vanessa indica were found to be strong indicators for particular seasons. Nymphalidae was the richest, most abundant, and most diverse family. Different families exhibited noticeable variations in diversity throughout the seasons. Species richness and abundance were positively affected by increased temperature but negatively affected by increased precipitation. The present study highlights the significance of seasonal shifts for butterfly diversity in a tropical region. The seasonality of butterflies in the study area may have also been influenced by anthropogenic activities and human-created habitat heterogeneity, resulting in the dominance of generalist species during specific seasons.