Temporal distribution of fruit-feeding butterflies (Lepidoptera, Nymphalidae) in the eastern extreme of the Amazon region

ABSTRACT Rainfall is one of the most influential factors driving insect seasonality in the Amazon region. However, few studies have analyzed the temporal dynamics of fruit-feeding butterflies in the Brazilian Amazon, specially in its eastern portion. Here, we evaluated the diversity patterns and temporal distribution of fruit-feeding butterflies in a remnant of eastern Amazon forest in the Baixada Maranhense, northeastern Brazil. Specifically, we tested whether fruit-feeding butterflies are temporally structured and whether rainfall influences species richness and abundance. Butterflies were collected with baited traps in both the rainy and dry seasons for two consecutive years. In total, we captured 493 butterflies belonging to 28 species, 15 genera and eight tribes. Three species comprised about half of the overall abundance, and Satyrinae was the most representative subfamily. The fruit-feeding butterfly assemblage showed a strong temporal structure during the second year of sampling, but not during the first year. Species composition and richness did not differ between rainy and dry seasons, and neither abundance nor richness was influenced by rainfall. Our results indicate that seasonality is not a strong environmental filter in this region, and that other biotic and abiotic factors are probably driving the community structure. The predominance of palms in the Baixada Maranhense, which are used as host plants by larvae of several lepidopteran species (specially satyrines) and are available year-round, might have contributed to the observed patterns of temporal diversity.

摘要 降雨是驱动亚马逊地区昆虫季节性发生的最关键影响因子之一。然而目前针对巴西亚马逊地区，尤其是其东部区域的食果蝴蝶时间动态的研究仍较为匮乏。本研究以巴西东北部马拉尼昂州低地的一处亚马逊东部森林残存斑块为研究对象，对该区域食果蝴蝶的多样性格局与时间分布特征进行了评估。具体而言，本研究旨在验证两个科学问题：食果蝴蝶群落是否存在时间结构，以及降雨是否会对物种丰富度与个体丰度产生影响。研究采用诱饵诱捕法，在连续两年的雨季与旱季均开展了蝴蝶采集工作。本次研究共采集到493头食果蝴蝶，隶属于28种、15属及8族。其中3个物种的个体数占总捕获量的近一半，眼蝶亚科（Satyrinae）为占比最高的亚科。食果蝴蝶群落仅在采样的第二年呈现出显著的时间结构，第一年则未观测到此特征。雨季与旱季间的物种组成与物种丰富度均无显著差异，且个体丰度与物种丰富度均未受降雨的调控。本研究结果表明，季节性变化并非该区域的强环境过滤因子，其他生物与非生物因素可能才是驱动群落结构形成的核心因素。马拉尼昂州低地广泛分布的棕榈科植物可作为多种鳞翅目幼虫（尤其是眼蝶亚科物种）的寄主植物，且全年均可获取，这可能是促成本次观测到的时间多样性格局的重要原因。