Individual-level size distribution patterns in fruit-feeding butterfly communities along a forest restoration gradient in the Afrotropics

Abstract

The loss and degradation of tropical rainforests pose significant challenges to global conservation, yet the impact of forest restoration on the functional diversity of animal communities, particularly at the intraspecific level, remains poorly understood. This study investigates the size distribution of fruit-feeding butterflies along a gradient of tropical forest restoration ages in Kibale National Park, Uganda. Study sites were categorised into three forest age groups: younger restored (10–16 years), older restored (21–26 years), and primary forests. Butterflies were sampled across 48 sites, and individual forewing lengths were measured to analyse changes in mean forewing length, diversity, skewness, and kurtosis. The mean forewing length and diversity increased, while skewness and kurtosis decreased, towards primary forest age group. Significant differences in size metrics were observed among forest age groups, with younger restored forests showing lower diversity compared to older restored and primary forests. Intraspecific differences in forewing length were detected in six of the 12 species studied, highlighting the nuanced insights provided by individual-level data compared to species-level analyses. Kernel density plots demonstrated a gradual shift towards more uniform size distributions along the restoration gradient, suggesting that morphological diversity increases as forests mature. These findings underscore the value of considering intraspecific variation in understanding community responses to forest restoration. The study highlights the prolonged but steady progress towards primary forest, offering important implications for tropical forest conservation and applied ecology.