Seed and microsite limitations of recruitment and the impacts of post-dispersal seed predation at the within population level |
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Authors: | María Calviño-Cancela |
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Institution: | (1) Department of Ecology and Animal Biology, University of Vigo, E.U.E.T. Forestal, Campus Universitario, 36005 Pontevedra, Spain;(2) Present address: Department of Environmental Biology, Curtin University of Technology, GPO Box U1987, Perth, WA, 6845, Australia |
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Abstract: | Seed predation may cause important seed losses in plant populations, but its impact on the dynamics of populations will depend
on the degree of seed or microsite limitations for recruitment. Seed losses will only affect recruitment if it is seed limited.
The nature of recruitment limitation (seeds or microsites) is usually ascribed to whole plant populations but it may vary
within populations among microhabitats and habitats. Thus, the potential impact of seed predation will also vary within the
population, being highest where recruitment is seed limited. The impact to the whole population will depend on the spatial
concordance between the intensity of seed predation and that of seed limitation. Recruitment limitations (with seed addition
experiments), seed predation (with seed removal experiments), and the dynamics of seed availability in the soil (with soil
samples taken both after seed dispersal and before the following dispersal event) of the shrub Corema album (Empetraceae) were investigated in dunes in NW Spain, at microhabitats ‘open ground’, ‘underneath C. album ♀’, and ‘underneath C. album ♂’ at two habitats, sparse and dense scrub. The nature of recruitment limitation (seeds vs. microsites) varied within the
population. It was seed limited in the microhabitat ‘open ground’ and microsite limited under shrub cover. The spatial patterns
of seedling recruitment were unrelated to seed availability but strongly affected by germination requirements. The spatial
discordance between seed availability and recruitment implies a crucial constraint for processes affecting seed availability
(seed predation but also e.g., dispersal) to impact recruitment. They will not affect its spatial pattern but only its quantity
as long as they act in those sites selected by seeds to germinate. Seed predation was highest underneath mother plants and lowest in open ground. Thus, its potential
impact is low, as it is centred where recruitment is not seed limited. This study shows that the analysis of seed predation
in relation to recruitment limitations at smaller spatial scales within the population provides more insight to understand
its impact. |
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Keywords: | Recruitment limitation Seed availability Seed-addition experiments Spatial heterogeneity Spatial concordance Spatial patterns |
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