Asynchrony in the dynamics of chironomids across six locations in northeastern Iceland

Abstract

Simultaneously studying population dynamics at multiple locations can provide insights into the ecological processes shaping changes in the abundances of species. Here, we examine 18-year time series of abundances of non-biting midges (Diptera: Chironomidae) from window trap samples at five lakes in northeastern Iceland: Miklavatn, Sílalækjarvatn, Skjálftavatn, Víkingavatn, and Mývatn. The largest lake, Mývatn, consists of two distinct basins which we treat as separate locations. Fluctuations in aggregate midge abundance show little correlation among locations, with even neighboring locations exhibiting asynchronous patterns. Such spatial asynchrony suggests that regional environmental forcing and interlake movement are insufficient to synchronize midge dynamics across sites. Instead, the observed patterns are consistent with the importance of lake-specific ecological processes, which may include differences in habitat structure, resource dynamics, species interactions, or local consumer-resource dynamics. Additional evidence for the importance of lake-specific processes is the cyclicity of the aggregate abundance of midge species found for all locations, which suggests that the dominant species are subject to strong internal processes that act separately at each location. The results have implications for conservation management of species such as insectivorous birds that can migrate between locations and take advantage of episodic, localized peaks in midge abundance.