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Population dynamics of epiphytic orchids in a metapopulation context

BACKGROUND AND AIMS: Populations of many epiphytes show a patchy distribution where clusters of plants growing on individual trees are spatially separated and may thus function as metapopulations. Seed dispersal is necessary to (re)colonize unoccupied habitats, and to transfer seeds from high- to lo...

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Autores principales: Winkler, Manuela, Hülber, Karl, Hietz, Peter
Formato: Texto
Lenguaje:English
Publicado: Oxford University Press 2009
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2749534/
https://www.ncbi.nlm.nih.gov/pubmed/19671576
http://dx.doi.org/10.1093/aob/mcp188
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author Winkler, Manuela
Hülber, Karl
Hietz, Peter
author_facet Winkler, Manuela
Hülber, Karl
Hietz, Peter
author_sort Winkler, Manuela
collection PubMed
description BACKGROUND AND AIMS: Populations of many epiphytes show a patchy distribution where clusters of plants growing on individual trees are spatially separated and may thus function as metapopulations. Seed dispersal is necessary to (re)colonize unoccupied habitats, and to transfer seeds from high- to low-competition patches. Increasing dispersal distances, however, reduces local fecundity and the probability that seeds will find a safe site outside the original patch. Thus, there is a conflict between seed survival and colonization. METHODS: Populations of three epiphytic orchids were monitored over three years in a Mexican humid montane forest and analysed with spatially averaged and with spatially explicit matrix metapopulation models. In the latter, population dynamics at the scale of the subpopulations (epiphytes on individual host trees) are based on detailed stage-structured observations of transition probabilities and trees are connected by a dispersal function. KEY RESULTS: Population growth rates differed among trees and years. While ignoring these differences, and averaging the population matrices over trees, yields negative population growth, metapopulation models predict stable or growing populations because the trees that support growing subpopulations determine the growth of the metapopulation. Stochastic models which account for the differences among years differed only marginally from deterministic models. Population growth rates were significantly lower, and extinctions of local patches more frequent in models where higher dispersal results in reduced local fecundity compared with hypothetical models where this is not the case. The difference between the two models increased with increasing mean dispersal distance. Though recolonization events increased with dispersal distance, this could not compensate the losses due to reduced local fecundity. CONCLUSIONS: For epiphytes, metapopulation models are useful to capture processes beyond the level of the single host tree, but local processes are equally important to understand epiphyte population dynamics.
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spelling pubmed-27495342009-10-14 Population dynamics of epiphytic orchids in a metapopulation context Winkler, Manuela Hülber, Karl Hietz, Peter Ann Bot Original Articles BACKGROUND AND AIMS: Populations of many epiphytes show a patchy distribution where clusters of plants growing on individual trees are spatially separated and may thus function as metapopulations. Seed dispersal is necessary to (re)colonize unoccupied habitats, and to transfer seeds from high- to low-competition patches. Increasing dispersal distances, however, reduces local fecundity and the probability that seeds will find a safe site outside the original patch. Thus, there is a conflict between seed survival and colonization. METHODS: Populations of three epiphytic orchids were monitored over three years in a Mexican humid montane forest and analysed with spatially averaged and with spatially explicit matrix metapopulation models. In the latter, population dynamics at the scale of the subpopulations (epiphytes on individual host trees) are based on detailed stage-structured observations of transition probabilities and trees are connected by a dispersal function. KEY RESULTS: Population growth rates differed among trees and years. While ignoring these differences, and averaging the population matrices over trees, yields negative population growth, metapopulation models predict stable or growing populations because the trees that support growing subpopulations determine the growth of the metapopulation. Stochastic models which account for the differences among years differed only marginally from deterministic models. Population growth rates were significantly lower, and extinctions of local patches more frequent in models where higher dispersal results in reduced local fecundity compared with hypothetical models where this is not the case. The difference between the two models increased with increasing mean dispersal distance. Though recolonization events increased with dispersal distance, this could not compensate the losses due to reduced local fecundity. CONCLUSIONS: For epiphytes, metapopulation models are useful to capture processes beyond the level of the single host tree, but local processes are equally important to understand epiphyte population dynamics. Oxford University Press 2009-10 2009-08-11 /pmc/articles/PMC2749534/ /pubmed/19671576 http://dx.doi.org/10.1093/aob/mcp188 Text en © 2009 The Author(s) http://creativecommons.org/licenses/by-nc/2.0/uk/ This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Original Articles
Winkler, Manuela
Hülber, Karl
Hietz, Peter
Population dynamics of epiphytic orchids in a metapopulation context
title Population dynamics of epiphytic orchids in a metapopulation context
title_full Population dynamics of epiphytic orchids in a metapopulation context
title_fullStr Population dynamics of epiphytic orchids in a metapopulation context
title_full_unstemmed Population dynamics of epiphytic orchids in a metapopulation context
title_short Population dynamics of epiphytic orchids in a metapopulation context
title_sort population dynamics of epiphytic orchids in a metapopulation context
topic Original Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2749534/
https://www.ncbi.nlm.nih.gov/pubmed/19671576
http://dx.doi.org/10.1093/aob/mcp188
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