Elevational changes in the composition of insects and other terrestrial arthropods at tropical latitudes: a comparison of multiple sampling methods and social spider diets

Abstract

Abstract. We explored the extent to which differences between elevations in arthropod composition – insects and arachnids – are reflected by different sampling methods and in the diet of local social and subsocial spiders. We surveyed two low‐elevation tropical rainforest and two upper montane cloud forest sites in eastern Ecuador using blacklighting, sweeping, malaise traps, beating, and visual search. We also observed the prey captured by social (lowland rainforest) and subsocial (upper montane cloud forest) spider colonies in each habitat and related their diets to the insect composition yielded by the individual and combined set of techniques. The most notable differences between high‐ and low‐elevation sites in eastern Ecuador were an increase in the relative abundance of Hymenoptera, in particular ants, and a concomitant reduction in the representation of homopterans, dipterans and coleopterans at lower elevations. Differences between elevations, however, were only detected by three of the techniques employed (beating, sweeping and blacklighting). The proportions of major taxa categories in the spider diets were only significantly different from samples from their respective environments for the upper elevation subsocial spider against blacklighting and the combined set of all techniques, excluding blacklighting. Nonetheless, only sweeping had similarity indices greater than 75% for both species, with beating and malaise being the next most similar. The more advanced level of sociality and larger nests of the social species may facilitate exploitation of a more representative range of insect types from its environment.