Seasonal Changes in Vertical Stratification of Moth Diversity in Tropical Rainforests of Thailand

Abstract

Canopies of tropical rainforests present distinguished microclimates and habitats, creating vertically stratified forest biodiversity. Although distances from the ground to canopy layers are at most tens of meters, vertical turnover of communities are generally much greater than horizontal turnover which can stretch hundreds or thousands of meters. Insect diversity is stratified along vertical gradients, as insects, especially herbivorous insects, depend on various food resources and microhabitats provided by canopy trees. Although seasonal changes in insect community composition have been extensively documented, little attention has been paid to understand how vertical stratification of insects change across seasons. Here we investigated how moth diversity change vertically and horizontally across seasons in tropical rainforests located at different latitudes in Thailand. Moth samples were collected at Mo Singto (MS, 14º22ʹ55ʺN 101º25ʹ54ʺE) Khao Yai National Park, and Klong Naka Wildlife Sanctuary (KN, 9º27ʹ34ʺN 98º30ʹ15ʺE) in wet and dry seasons. At each site, moth samples were collected from the canopy and understory layers at a total of nine sampling plots established within a 300 m × 300 m grid. We identified moths to family as family level data can be compared across sites at different latitudes. The results showed that vertical stratification of moth diversity was more distinct in KN than MS plots, whereas seasonal change in moth diversity was more distinct in MS than KN. Our study suggests that vertical stratification of moth diversity is universal, as is suggested by other studies, but seasonal influence on vertical stratification may be highly variable across different latitudes.