Habitat Fragmentation and Seasonal Variation Shape Butterfly Community Structure in a Tropical University Landscape, Nigeria

Habitat fragmentation and seasonal variation are key ecological factors influencing butterfly community structure in tropical ecosystems.  This study investigated their effects at Federal University Wukari, Taraba State, Nigeria.  Surveys were conducted along a 1500 m transect within each of two habitat types (fragmented and non-fragmented), sampled weekly for four weeks per season, using sweep-netting and the Pollard walk method.  Data were analyzed in R for species richness, abundance, diversity (Shannon–Wiener, Simpson), evenness, dominance, and Jaccard similarity, with paired comparisons across replicate weekly samples testing habitat and seasonal effects.  A total of 438 individuals representing 45 species and five families were recorded; Nymphalidae was dominant (164 individuals, 37.4%), followed by Pieridae (124, 28.3%) and Lycaenidae (105, 24.0%).  The non-fragmented habitat had significantly greater abundance (303; t = 4.01, p = 0.005) and richness (41 species; t = 5.48, p < 0.001) than the fragmented habitat (135; 26 species), persisting after rarefaction to equal sample size.  Diversity indices were higher in the non-fragmented habitat (Shannon = 3.121; Simpson = 0.935) than the fragmented habitat (Shannon = 2.493; Simpson = 0.861).  The dry season had significantly higher abundance than the wet season (251 vs 187; t = 2.39, p = 0.048), though richness did not differ significantly (p = 0.157); wet-season diversity and evenness were slightly higher.  Species composition showed moderate similarity between habitats (Jaccard = 0.489) and seasons (0.556), indicating turnover.  These findings show habitat fragmentation exerts a stronger, statistically supported influence on community structure than seasonal variation, underscoring the value of intact vegetation for tropical university landscapes.