Spatial and temporal shifts are known to influence species abundances in both the short (season) and long term (years) and across small and large distances. For example, seasonal changes in temperature and resource availability can affect the egg-laying phenology of some caddisfly species. These shifts are often species specific, arising from different phenology, environmental preferences, and other factors, and so cause varying community composition through space and time.
Here, we investigated the spatial and temporal variation in the abundances of egg masses of eight caddisfly species. We conducted seasonal surveys in nine riffles across four rivers for four years (2023 – 2026). We found species-specific differences at large and small scales. Oviposition patterns differed among years, rivers, and riffles. At a finer scale, we found species-specific seasonal patterns in egg numbers and in oviposition locations across rivers (from bank to bank). The largest river surveyed, the Rubicon River, had the highest abundances of egg masses for all species except Ulmerochorema seonum. Autumn had the highest abundances of egg masses for all species except Koetonga clivicola whose highest abundances were recorded in the spring.
How species partition under different environmental conditions determines both the impact of environmental conditions on their performance and potential competitive interactions. These processes can occur at many scales, though their holistic impact is what ultimately drives population and community dynamics. Observing a single snapshot, such as one sampling season, or a mean over space or time, can miss important features of the system. The seasonal trends and spatial differences of species abundances seen here provide critical knowledge to better understand community dynamics, species coexistence and responses to impacts such as climate change.