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Environmental context influences the impact of pre-dispersal seed predation on host plant population dynamics in multiple ways
Stockholm University, Faculty of Science, Department of Botany.
Stockholm University, Faculty of Science, Department of Botany.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Environmental heterogeneity influences species distributions as well as population dynamics within species. Effects of the environment can be both direct and indirect, altering the outcome of biotic interactions. Although it is well known that biotic interactions may strongly affect several vital rates, few studies have investigated how the effect of biotic interactions on life-time fitness and population dynamics depends on environmental context. We studied how the effect of pre-dispersal seed predation on host plant population growth rates varied with soil conditions and vegetation height, monitoring 24 populations of the perennial herb Primula farinosa during three consecutive years. First, we investigated how reductions in population growth rate due to seed predators were related to predation intensity and the sensitivity of population growth rate to predation, respectively. Second, we examined how predation intensity and sensitivity were related to environmental context in terms of soil depth, soil moisture, soil nutrient composition and vegetation height. Both seed predation intensity and sensitivity of population growth rate to seed predation varied considerably among populations, and both contributed to variation in the effects of seed predation on population growth rate. Soil moisture influenced population growth rate in three different ways; via direct effects on potential growth rate, via effects on predation intensity and via effects on the sensitivity of population growth rates to seed predation. We conclude that, in our study system, environmental context influences how biotic interactions affect population dynamics, and that a given environmental parameter can influence population growth rate in different directions through effects on potential growth rate, intensity of biotic interactions, and the sensitivity of population growth rate to these biotic interactions.

National Category
Botany Ecology
Research subject
Plant Ecology
Identifiers
URN: urn:nbn:se:su:diva-79480OAI: oai:DiVA.org:su-79480DiVA: diva2:549457
Funder
Formas
Available from: 2012-09-05 Created: 2012-09-04 Last updated: 2012-09-07Bibliographically approved
In thesis
1. Environmental heterogeneity, population dynamics and life-history differentiation in Primula farinosa
Open this publication in new window or tab >>Environmental heterogeneity, population dynamics and life-history differentiation in Primula farinosa
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Allocation to reproduction is a key life-history trait. Optimal allocation to reproduction depends on environmental conditions because of their effects both on costs and benefits of reproduction and on patterns of growth, fecundity, and mortality. In this thesis, I studied 24 populations of the perennial herb Primula farinosa in the northern part of the Great Alvar on Öland, SE Sweden, and in an experimental garden at Stockholm University to investigate how plant allocation patterns and population dynamics vary along environmental gradients. In the first study, I performed experimental manipulations of reproduction to study costs of reproduction in relation to water availability. In the second study, I performed a demographic survey to investigate the effects of pre-dispersal seed predation on host-plant population dynamics in relation to environmental context. In the third study, I used a common garden experiment to investigate whether environmental variation among natural populations was correlated with genetic differentiation in reproductive effort, and in the fourth study, I performed reciprocal transplantations among four populations to investigate whether genetically based adaptive differentiation among local populations could be detected. The results showed that under natural conditions, plant reproductive costs, intensity of pre-dispersal seed predation, population growth rate and reproductive effort varied with water availability and vegetation height. Costs of reproduction were detected at high and low water availability but not under intermediate soil moisture conditions (paper I). Population dynamics of P. farinosa were affected by environmental conditions both directly, through effects on potential population growth rate (in the absence of seed predation) and indirectly, through effects on seed predation intensity and sensitivity to seed predation (paper II). Among-population genetic differentiation in reproductive allocation was documented in the common-garden experiment (paper III). However, reciprocal transplantations among populations separated by up to 6.2 km provided no evidence of local adaptation to current environmental conditions. Moreover, large differences in the performance of individuals transplanted to different study sites suggest that the study populations display considerable phenotypic plasticity (paper IV). Taken together, the results of these studies suggest that environmental variation has important direct and indirect effects on population dynamics and life history trade-offs in P. farinosa, and that differences in reproductive effort partly reflect genetic differentiation, but that phenotypic variation observed among natural populations does not reflect adaptations to current environmental conditions.  

Place, publisher, year, edition, pages
Stockholm: Department of Botany, Stockholm University, 2012. 30 p.
National Category
Ecology Botany
Research subject
Plant Ecology
Identifiers
urn:nbn:se:su:diva-79566 (URN)978-91-7447-547-0 (ISBN)
Public defence
2012-10-12, föreläsningssalen, Botaniska institutionen, Lilla Frescativägen 5, Stockholm, 10:00 (English)
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Formas
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.

Available from: 2012-09-20 Created: 2012-09-06 Last updated: 2012-09-07Bibliographically approved

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