Consumer–resource interactions and cyclic population dynamics of Tanytarsus gracilentus (Diptera: Chironomidae)

Abstract

Summary 1.Tanytarsus gracilentus population dynamics in Lake Myvatn show a tendency to cycle, with three oscillations occurring between 1977 and 1999 having periods of roughly 7 years. The population abundance fluctuated over four orders of magnitude. 2. A partial autocorrelation function (PACF) accounting for measurement error revealed a strong positive lag-1 autocorrelation and a moderate negative lag-2 partial autocorrelation. This suggests that the dynamics can be explained by a simple secondorder autoregressive process. 3. We tested the alternative hypotheses that the cyclic dynamics of T. gracilentus were driven by consumer-resource interactions in which T. gracilentus is the consumer, or predator-prey interactions in which T. gracilentus is the prey. We analysed autoregressive models including both consumer-resource interactions and predator-prey interactions. 4. Wing length of T. gracilentus was used as a surrogate for resource abundance and/or quality, because body size is known to fluctuate with resource abundance and quality in dipterans. Furthermore, the wing lengths of Micropsectra lindrothi , a species ecologically similar to T. gracilentus , fluctuated synchronously with T. gracilentus wing lengths, thereby indicating that the shared resources of these two species were indeed cycling. Wing lengths of other chironomid species were not synchronized. 5. The predators of T. gracilentus included midges in the genera Procladius and Macropelopia , and the fish Gasterosteus aculeatus (three-spined stickleback). 6. The autoregressive models supported the hypothesis that T. gracilentus dynamics were driven by consumer-resource interactions, and rejected the hypothesis that the dynamics were driven by predator-prey interactions. 7. The models also revealed the consequences of consumer-resource interactions for the magnitude of fluctuations in T. gracilentus abundance. Consumer-resource interactions amplified the exogenous variability affecting T. gracilentus per capita population growth rates (e.g. temperature, rainfall, etc.), leading to variability in abundance more than two orders of magnitude greater than the exogenous variability.

Population trends in the Slavonian grebe Podiceps auritus (L.) and Chironomidae (Diptera) at a Scottish loch

“…Erratic inter-annual fluctuations in the size of the chironomid population, which are also reflected in Slavonian grebe productivity, also appear to be correlated with inter-annual changes in lake productivity indicated by DI-TP values. Our results corroborate studies in Iceland (Einarsson et al 2002;Ives et al 2008), which have suggested that chironomid population fluctuations are resource-linked and do not appear to be driven by climate or predator-prey interactions. Our study suggests that lake productivity may be the ultimate driver of chironomid population fluctuations at Loch Ruthven, which in turn affect breeding success of the Slavonian grebes.…”

“…The abundance of prey species may be more significant. Studies at Myvatn, Iceland, where abundance of adult chironomids was recorded each year over 25 years and compared annually to the size of duck populations (Einarsson et al 2002Gardarsson and Einarsson 1994) suggested that the productivity of several species of duck is influenced by the abundance of non-biting midges (Diptera: Chironomidae). Small fish, particularly the threespined stickleback, Gasterosteus acutelatus, which feeds on chironomid larvae, are also an important component of the diet of adult Slavonian grebes (Fjeldså 1973).…”

Chironomids (Diptera) and oxy‐regulatory capacity: An experimental approach to paleolimnological interpretation

“…The adaptive and/or competitive advantages of T. gracilentus in these lakes do not, however, have to be related to oxygen regimes. Consumerresource interactions has recently been shown to be important as well (Einarsson et al 2002). The two pigmented Chi- (Table 3) and environmental variables are from Brodersen and Anderson (2002).…”

Long-term changes in benthic Cladocera populations in Lake Myvatn, Iceland

“…Reduced nutritive quality of the detritus is suggested by a delayed negative correlation between body size and population density of T. gracilentus observed by Einarsson et al (2002). The changes in physical structure are described by Gardarsson & Snorrason (1993) and Ólafsson and Paterson (2004).…”

“…Monitoring of the chironomid populations started in 1977 (Gardarsson et al 1995, three-spined sticklebacks (Gasterosteus aculeatus L.) in 1989 (Gíslason et al 1998), and since 1990 density of benthic Cladocera has been monitored with activity traps (Örnólfsdóttir & Einarsson 2004). Monitoring at Lake Myvatn has already yielded much insight into the long term food web dynamics of the lake, notably its oscillatory behaviour, interaction between chironomids and their sediment resources (e.g., Einarsson et al 2002) and the response of breeding duck populations to year-to-year variation in chironomid abundance (e.g., .…”