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Trade-offs and habitat constraints in the establishment of epiphytic bryophytes
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution. (Ecology of mire plants and bryophytes)
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution. (Ecology of mire plants and bryophytes)
2010 (English)In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 24, no 4, 887-897 p.Article in journal (Refereed) Published
Abstract [en]

1. Diversity of patch-tracking epiphyte metacommunities depends on successful colonization of new habitats. Habitat constraints and critical stages in the establishment have gained little attention in metacommunity studies, but a trade-off between dispersal ability and establishment rate is often assumed. This assumption remains largely untested, and alternative dispersal and reproductive strategies offer several trade-offs to be explored.

2. We used in vitro experiments to identify critical stages in the establishment of obligate epiphytic bryophytes with contrasting dispersal strategies [sexual via small (< 20 mu m) or large (> 20 mu m) spores, asexual via gemmae or gemmae-like branchlets], and to identify habitat constraints of diaspore establishment and trade-offs among species traits.

3. Across all stages of the establishment process, large asexual diaspores performed better than small sexual ones. Asexual species also had a higher ability to establish from fragments than sexual species. Germination of all diaspore types was limited by pH with highest germination rates at intermediate pH. Large moss spores showed a higher desiccation tolerance than small ones, but lower germination and protonemal growth rates. Liverwort spores had the lowest desiccation tolerance, germination and protonemal growth rates, but rapidly developed gametophytic shoots once they had germinated.

4. Combining the results with earlier studies on dispersal distances in epiphytes, our study demonstrated a trade-off between dispersal distance and establishment ability, which may be central for the evolution of asexual dispersal in epiphytes. The evolution of spore size may additionally involve trade-offs between high germination and protonemal growth rates, desiccation tolerance, and a rapid development from protonema to shoots. We suggest that trade-offs in epiphytes are shaped by conflicting selection pressures imposed by habitat patchiness, landscape dynamics and irregular water supply.

Place, publisher, year, edition, pages
2010. Vol. 24, no 4, 887-897 p.
Keyword [en]
desiccation, germination, life-history trade-offs, metacommunity, pH, patch-tracking, protonema, reproductive strategies
National Category
Biological Sciences
Research subject
Ecological Botany
Identifiers
URN: urn:nbn:se:uu:diva-107315DOI: 10.1111/j.1365-2435.2010.01705.xISI: 000279837700022OAI: oai:DiVA.org:uu-107315DiVA: diva2:228733
Note
Part of PhD-thesis which will be defended the 26th of September 2009Available from: 2009-08-05 Created: 2009-08-05 Last updated: 2011-12-29Bibliographically approved
In thesis
1. Metapopulation and metacommunity processes, dispersal strategies and life-history trade-offs in epiphytes
Open this publication in new window or tab >>Metapopulation and metacommunity processes, dispersal strategies and life-history trade-offs in epiphytes
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis was to increase knowledge about metapopulation and metacommunity processes in patchy, dynamic landscapes, using epiphytic bryophytes as a model system. Host trees and deciduous forest stands in the coniferous landscape are patchy, temporal and undergo changes in habitat quality during succession. Epiphytes must track this dynamic habitat network for their long-term survival. Community patterns at different spatial scales were explored and linked to regional metapopulation processes and local population dynamics.

Spatial structuring in species richness both at a local and regional scale indicated stronger dispersal limitation but lower sensitivity to habitat quality in species with large asexual than in species with small sexual diaspores. In sexually dispersed species, a strong rescue effect was indicated by a bimodal frequency distribution of the species and by increasing local abundance with increasing patch connectivity. Present connectivity to other deciduous forest patches had positive effects on richness of asexually dispersed species, whereas richness of sexually dispersed species was instead related to the landscape connectivity 30 years ago. A study of local growth and reproduction suggested that this is caused by delayed sexual, but not asexual, reproduction. Habitat conditions affected the production of sporophytes, but not of asexual diaspores. No differences in either growth rates or competitive abilities among species with different dispersal and life-history strategies were found. In vitro experiments showed that establishment is higher from large asexual diaspores than from small sexual. Establishment of all diaspore types was limited by pH. There were indications of trade-offs between high germination and protonemal growth rates, desiccation tolerance and a rapid development of shoots from protonema.

The results indicated that the epiphyte metacommunity is structured by two main trade-offs: dispersal distance (diaspore size) versus age at first reproduction, and dispersal distance versus sensitivity to habitat quality. Trade-offs in species traits may have evolved as a consequence of conflicting selection pressures imposed by habitat turnover, connectivity and irregular water supply rather than by species interactions. Syndromes of interrelated species traits imply that fairly small changes in habitat conditions can lead to distinct changes in metacommunity diversity: the results indicate that increasing distances among patches cause most harm to asexually dispersed species, whereas cuttings of forests of high age and quality as well as increasing patch dynamics are most harmful to sexually dispersed species.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 37 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 661
Keyword
asexual, biodiversity, bryophytes, dispersal limitation, establishment, evolution of reproductive traits, germination, growth, habitat fragmentation, landscape dynamics, local processes, patch-tracking, pH, reproduction, species richness, species interactions
National Category
Other Biological Topics
Research subject
Ecological Botany
Identifiers
urn:nbn:se:uu:diva-106847 (URN)978-91-554-7578-9 (ISBN)
Public defence
2010-05-20, Lindahlsalen, EBC, Norbyvägen 18B, 752 36, Uppsala, 10:00 (English)
Opponent
Supervisors
Note
Senarelagd disputation från: 2009-09-26, Lindahlsalen, EBC, Villavägen 9, 75236 Uppsala, Uppsala, 10:00 Available from: 2010-03-09 Created: 2009-07-06 Last updated: 2011-03-02Bibliographically approved

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Löbel, SwantjeRydin, Håkan

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