title: When phenology matters: age-size truncation alters population response to trophic mismatch.
abstract: Climate-induced shifts in the timing of life-history events are a worldwide phenomenon, and these shifts can de-synchronize species interactions such as predator-prey relationships. In order to understand the ecological implications of altered seasonality, we need to consider how shifts in phenology interact with other agents of environmental change such as exploitation and disease spread, which commonly act to erode the demographic structure of wild populations. Using long-term observational data on the phenology and dynamics of a model predator-prey system (fish and zooplankton in Windermere, UK), we show that age-size truncation of the predator population alters the consequences of phenological mismatch for offspring survival and population abundance. Specifically, age-size truncation reduces intraspecific density regulation due to competition and cannibalism, and thereby amplifies the population sensitivity to climate-induced predator-prey asynchrony, which increases variability in predator abundance. High population variability poses major ecological and economic challenges as it can diminish sustainable harvest rates and increase the risk of population collapse. Our results stress the importance of maintaining within-population age-size diversity in order to buffer populations against phenological asynchrony, and highlight the need to consider interactive effects of environmental impacts if we are to understand and project complex ecological outcomes.
authors.affiliation: Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, PO Box 1066 Blindern, 0316 Oslo, Norway jan.ohlberger@ibv.uio.no.
authors.forename: Jan
authors.identifier: http://orcid.org/0000-0001-6795-240X
authors.initials: J
authors.lastname: Ohlberger
authors.affiliation: Lake Ecosystems Group, Centre for Ecology & Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster, Lancashire LA1 4AP, UK.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Thackeray
authors.affiliation: Lake Ecosystems Group, Centre for Ecology & Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster, Lancashire LA1 4AP, UK.
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Winfield
authors.affiliation: Lake Ecosystems Group, Centre for Ecology & Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster, Lancashire LA1 4AP, UK.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Maberly
authors.affiliation: Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, PO Box 1066 Blindern, 0316 Oslo, Norway.
authors.forename: L Asbjørn
authors.initials: LA
authors.lastname: Vøllestad
mesh_terms: D000818:Animals; D033361:Cladocera / Q000254:growth & development / Q000502:physiology*; D002980:Climate; D004739:England; D020387:Food Chain; D060106:Lakes; D008954:Models, Biological; D010471:Perches / Q000254:growth & development / Q000502:physiology*; D011157:Population Dynamics; D012621:Seasons; D015048:Zooplankton
keywords: age–size truncation; climate change; density dependence; phenological mismatch; population variability