Spatial and temporal patterns of insect-order activity in the fynbos, South Africa

Abstract

The fynbos of South Africa is renowned for its high richness of plant species, many of which are insectpollinated. We conducted a visual survey of arthropod activity to examine how environmental factors influence activity patterns across the biome. We estimated the activity of moving medium- to large-sized Hymenoptera, Diptera, Lepidoptera and Coleoptera using an abundance-weighted presence score. Broken stick regression analysis shows that insect activity increased with ambient air temperatures to between 22 and 30 °C and then stabilized in the case of Hymenoptera, or decreased for Diptera, Lepidoptera and Coleoptera. There was also a clear negative impact of wind speed on arthropod activity. Insect activity across the biome was poorly explained by landscape temperature and rainfall variables, and was instead best explained by flower availability. A summer-autumn survey observed greater insect activity with no within-month variation, while the transition from winter to spring for the winter-spring survey saw more insect activity associated with the later months. More detailed studies of activity in the fynbos are needed at the species level, as predicted climate change impacts on temperature suggest likely consequences for plant-pollinator interactions, agricultural pest species, and arthropod-predator interactions.