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Individual variation between spiders on shores in the utilization of aquatic subsidies
Stockholm University, Faculty of Science, Department of Botany.
Stockholm University, Faculty of Science, Department of Botany.
Stockholm University, Faculty of Science, Department of Botany.
Stockholm University, Faculty of Science, Department of Botany.
(English)Manuscript (Other academic)
Abstract [en]

Intrapopulation variation is common in nature, and many generalist species actually consists of individual specialists. In food web ecology, stable isotope analysis is a common tool for examining energy and nutrient flows both between and within ecosystems, but large intrapopulation variation in isotopic values may lead to over- or underestimations of dietary variation between populations or species. Such large intraguild variation is common in spiders, which often are generalist predators. In this study we have used carbon and nitrogen stable isotope analysis to examine diets of shore-dwelling spiders, in relation to aquatic inflows to shore ecosystems. The study was carried out on shores inside and outside a eutrophicated bay in the Baltic Sea, using carbon and nitrogen stable isotope analysis. Aquatic subsidies consisted of inflows of algae (mainly green filamentous algae) and emerging insects (Chironomidae). We found that spiders inside the bay all utilized mainly terrestrial prey, while spiders outside the bay, in particular wolf spiders, were separated into individuals utilizing either terrestrial or aquatic prey. The total population niche width was therefore larger outside than inside the bay. This individual specialization may be related to differences in nutrient enrichment in the aquatic ecosystem and/or salinity between sites inside and outside the bay, and we suggest that eutrophication decreases total niche width by affecting prey availability and prey choice of individual predators. We also conclude that while stable isotope analysis remains a useful tool for examining flows across ecosystem boundaries, caution is needed in the interpretation of data with large intrapopulation variation.

National Category
Ecology
Research subject
Plant Ecology
Identifiers
URN: urn:nbn:se:su:diva-27224OAI: oai:DiVA.org:su-27224DiVA: diva2:213001
Available from: 2009-04-26 Created: 2009-04-26 Last updated: 2010-01-14Bibliographically approved
In thesis
1. The Spider and the Sea: Effects of marine subsidies on the role of spiders in terrestrial food webs
Open this publication in new window or tab >>The Spider and the Sea: Effects of marine subsidies on the role of spiders in terrestrial food webs
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The purpose of this study was to identify if terrestrial arthropod predators on Baltic Sea shores vary in their use of marine versus terrestrial food items, and to construct a bottom-up food web for Baltic Sea shores. The inflow of marine nutrients in the area consists mainly of marine algal detritus and emerging aquatic insects (e.g. phantom midges, Chironomidae). Diets of coastal arthropods were examined using carbon and nitrogen stable isotope analysis, and a two source mixing model was used to examine proportions of marine carbon to diets. The results suggest that spiders are the terrestrial predators mainly utilizing nutrients and energy of marine origin on Baltic Sea shores, while insect predators such as beetles and hemipterans mainly utilize nutrients and energy derived from terrestrial sources, possibly due to differences in hunting behaviour. That spiders are the predators that benefit the most from the marine inflow suggest that eventual effects of marine subsidies for the coastal ecosystem as a whole are likely mediated by spiders.

Place, publisher, year, edition, pages
Stockholm: Department of Botany, Stockholm University, 2009. 44 p.
Keyword
marine subsidies, food webs, stable isotopes, shore ecosystems, predators, spiders, Pardosa, algae, emerging insects
National Category
Ecology
Research subject
Plant Ecology
Identifiers
urn:nbn:se:su:diva-27227 (URN)978-91-7155-877-0 (ISBN)
Public defence
2009-06-05, föreläsningssalen, Botanicum, Lilla Frescativägen 5, Stockholm, 13:00 (English)
Opponent
Supervisors
Available from: 2009-05-14 Created: 2009-04-26 Last updated: 2009-04-27Bibliographically approved

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