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Host plant population size determines cascading effects in a plant-herbivore-parasitoid system
Stockholm University, Faculty of Science, Department of Botany.
2006 In: Basic and Applied Ecology, ISSN 1439-1791, Vol. 7, no 3, 191-200 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2006. Vol. 7, no 3, 191-200 p.
URN: urn:nbn:se:su:diva-24554OAI: diva2:197785
Part of urn:nbn:se:su:diva-7177Available from: 2007-11-15 Created: 2007-11-09Bibliographically approved
In thesis
1. The spatial and temporal dynamics of plant-animal interactions in the forest herb Actaea spicata
Open this publication in new window or tab >>The spatial and temporal dynamics of plant-animal interactions in the forest herb Actaea spicata
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Landscape effects on species performance currently receives much attention. Habitat loss and fragmentation are considered major threats to species diversity. Deciduous forests in southern Sweden are previous wooded pastures that have become species-rich communities appearing as islands in agricultural landscapes, varying in species composition. Actaea spicata is a long-lived plant occurring in these forests. In 150 populations in a 10-km2 area, I studied pre-dispersal seed predation, seed dispersal and pollination. I investigated spatio-temporal dynamics of a tritrophic system including Actaea, a specialist seed predator, Eupithecia immundata, and its parasitoids. In addition, effects of biotic context on rodent fruit dispersal and effects of flowering time and flower number on seed set, seed predation and parasitization were studied. Insect incidences of both trophic levels were related to resource population size and small Eupithecia populations were maintained by the rescue effect. There was a unimodal relationship between seed predation and plant population size. Seed predator populations frequently went extinct in small plant populations, resulting in low average seed predation. Parasitoids were present in large plant populations but did not affect seed predator density. Seed predators aggregated at edges, relaxing seed predation in patch interiors. Flowering phenology was unrelated to seed set and insect incidence. A higher flower number did not influence seed predation but was associated with higher seed set and a tendency for a higher parasitization rate. In the study on fruit dispersal more fruits were removed inside than outside populations. Within plant populations more fruits were removed from large aggregations. Overall, this thesis underlines the importance of plant-animal interactions during different phases of the life cycle. The spatial configuration of host plants plays an important role for the outcome of plant-animal interactions and trophic cascades.

Place, publisher, year, edition, pages
Stockholm: Botaniska institutionen, 2007. 33 p.
Eupithecia immundata, parasitoid, rodent, seed predation, dispersal, recruitment, multitrophic, metapopulation, trophic cascades, community complexity
National Category
Biological Sciences
Research subject
Plant Ecology
urn:nbn:se:su:diva-7177 (URN)978-91-7155-535-9 (ISBN)
Public defence
2007-12-07, föreläsningssalen, Botanicum, Lilla Frescativägen 5, Stockholm, 10:00
Available from: 2007-11-15 Created: 2007-11-09Bibliographically approved

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