Abstract
The study of insect populations is dominated by research on terrestrial insects. Are aquatic insect populations different or are they just presumed to be different? We explore the evidence across several topics. (1) Populations of terrestrial herbivorous insects are constrained most often by enemies, whereas aquatic herbivorous insects are constrained more by food supplies, a real difference related to the different plants that dominate in each ecosystem. (2) Population outbreaks are presumed not to occur in aquatic insects. We report three examples of cyclical patterns; there may be more. (3) Aquatic insects, like terrestrial insects, show strong oviposition site selection even though they oviposit on surfaces that are not necessarily food for their larvae. A novel outcome is that density of oviposition habitat can determine larval densities. (4) Aquatic habitats are often largely 1-dimensional shapes and this is presumed to influence dispersal. In rivers, drift by insects is presumed to create downstream dispersal that has to be countered by upstream flight by adults. This idea has persisted for decades but supporting evidence is scarce. Few researchers are currently working on the dynamics of aquatic insect populations; there is scope for many more studies and potentially enlightening contrasts with terrestrial insects.
Highlights
The study of population dynamics is central to much ecological research
Population dynamics has been a cornerstone of insect ecology for centuries, aquatic insects are seldom considered in this context even though much research on aquatic insects relates directly or indirectly to various key principles of population ecology
The general aim of this paper is to explore some similarities and differences, both real and presumed, between the ecologies of aquatic and terrestrial insects, and to identify areas where aquatic insects can make a significant contribution to a general understanding of population dynamics
Summary
The study of population dynamics is central to much ecological research. It is a field with a history of controversy and debate, which galvanized a great deal of productive research. The frequency and magnitude of physical disturbances, such as floods and droughts, can reduce population sizes [17,18,19] These environmental impacts may involve density-independent mortality, but density-dependent mechanisms are possible when, for example, the availability of disturbance refugia results in density-dependent mortality [20] and through changes in consumer–resource dynamics [21,22,23]. Regulation of aquatic insects by predators (top-down control) may reduce population sizes through direct consumption of larvae or eggs [35,36], and via impacts on life history traits such as developmental time, adult body size and fecundity [37,38,39]. There are, some differences in the characteristics of aquatic and terrestrial ecosystems that may lead to differences in the way various processes play out in populations or how frequently different mechanisms of regulation appear in aquatic vs. terrestrial populations
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