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Apex predator induces predator-rich ecosystem state innorthern lakes
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.ORCID iD: 0000-0003-2001-5077
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Large predators are disappearing from ecosystems around the world. If predator speciesfacilitate each other’s existence through niche construction, this development could causecascading predator collapses and reduce ecosystem resilience. However, the importance offacilitation for the assembly and function of predator communities remains poorly understood.Here, we show that a large piscivorous fish, the northern pike (Esox lucius), enables theformation of a numerous and diverse predator community by inducing a dwarf ecotype ofEuropean whitefish (Coregonus lavaretus). Pike increases the standing biomass of prey-sized(<200mm) whitefish with a factor of 12.6, allowing small-gaped fish species (Percafluviatilis, Lota lota, Salvelinus alpinus and Salmo trutta) to go from small-growinggeneralists, to large-growing piscivores. Similarly, a guild of piscivorous birds (Gavia arctica,G. stellata, Sterna paradisaea, S. hirundo, Mergus serrator and M. merganser) shift from amixed diet to relying mainly on whitefish prey in presence of pike. Through this regime shift,the functional piscivore biomass in the non-pike fish community increases with a factor of14.2, and the density- and species richness of piscivorous birds increase with factors of 2.08and 2.16, respectively. Our results demonstrate how feedbacks between presence/absence ofimportant predators and the phenotype of prey may keep complex ecosystems in predator-richor predator-depleted states.

National Category
Ecology
Research subject
biochemical pharmacology; biology
Identifiers
URN: urn:nbn:se:umu:diva-224499OAI: oai:DiVA.org:umu-224499DiVA, id: diva2:1858845
Available from: 2024-05-20 Created: 2024-05-20 Last updated: 2024-05-20
In thesis
1. Using environmental DNA to unravel aquatic ecosystem dynamics
Open this publication in new window or tab >>Using environmental DNA to unravel aquatic ecosystem dynamics
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Human-induced climate change has led to unprecedented declines in Earth's biodiversity and significant habitat loss. Aquatic ecosystems areespecially at risk, facing pollution, overexploitation, and destruction. Consequently, monitoring biodiversity is critical. Traditional monitoring methods are often low in detection rates, time-consuming, invasive, and harmful to species, which hampers comprehensive biodiversity assessments. Environmental DNA (eDNA) offers a rapid alternative fortaxonomic identification, extracting genetic material from soil, sediments, or water without capturing living organisms, proving useful where traditional methods fall short. However, its integration into aquatic ecology is hampered by unresolved methodological issues.

This thesis demonstrates how eDNA can help reconstruct fish colonization histories in lakes post-glacial retreat. I employed species-specific primers with digital droplet PCR and metagenomic shotgun sequencing on ancient DNA from Holocene lake sediments. My findings show the detectability of DNA from ancient fish populations. However, each method exhibited technical limitations that led to varying degrees offalse negatives and false positive results. Additionally, I examined how Northern pike (Esox Lucius) affects ecological speciation in Europeanwhitefish (Coregonus lavaretus), promoting a shift from insectivorous to piscivorous states, enhancing predator biodiversity and biomass. Dietan alyses of piscivorous birds through digital droplet PCR revealed that smaller whitefish support a larger, more diverse bird community. Finally, I compared two molecular techniques for quantifying bird diets from fecal DNA, finding that metabarcoding with a universal fish primer and digital droplet PCR yielded similar results. This research enhances ourunderstanding of the potential and limitations of molecular tools forspecies identification and aids the integration of eDNA into aquatic ecology.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2024. p. 24
Keywords
Environmental DNA, ancient DNA, colonization, apex predator, pike, whitefish, piscivorous birds, aquatic ecosystems, metabarcoding, digital droplet PCR
National Category
Ecology
Research subject
biology
Identifiers
urn:nbn:se:umu:diva-224501 (URN)978-91-8070-412-0 (ISBN)978-91-8070-413-7 (ISBN)
Public defence
2024-06-14, KBE303, Stora Hörsalen, KBC-huset, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2024-05-24 Created: 2024-05-20 Last updated: 2024-05-21Bibliographically approved

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Olajos, FredrikEnglund, Göran

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