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Dispersal and life-history strategies in epiphyte metacommunities: alternative solutions to survival in patchy, dynamic landscapes
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)
2009 (English)In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 161, no 3, 569-579 p.Article in journal (Refereed) Published
Abstract [en]

Host trees for obligate epiphytes are dynamic patches that emerge, grow and fall, and metacommunity diversity critically depends on efficient dispersal. Even though species that disperse by large asexual diaspores are strongly dispersal-limited, asexual dispersal is common. The stronger dispersal limitation of asexually reproducing species compared to species reproducing sexually via small spores may be compensated by higher growth rates, lower sensitivity to habitat conditions, higher competitive ability or younger reproductive age.

We compared growth and reproduction of different groups of epiphytic bryophytes with contrasting dispersal (asexual vs sexual) and life-history strategies (colonists, short- and long-lived shuttle species, perennial stayers) in an old-growth forest stand in the boreo-nemoral region in Eastern Sweden.

No differences were seen in relative growth rates between asexual and sexual species. Long-lived shuttles had lower growth rates than colonists and perennial stayers. Most groups grew best at intermediate bark pH. Interactions with other epiphytes had a small, often positive effect on growth. Neither differences in sensitivity of growth to habitat conditions nor differences in competitive abilities among species groups were found. Habitat conditions, however, influenced the production of sporophytes, but not of asexual diaspores. Presence of sporophytes negatively affected growth, whereas presence of asexual diaspores did not. Sexual species had to reach a certain colony size before starting to reproduce, whereas no such treshold existed for asexual reproduction.

The results indicate that the epiphyte metacommunity is structured by two main trade-offs: dispersal distance vs reproductive age, and dispersal distance vs sensitivity to habitat quality. There seems to be a trade-off between growth and sexual reproduction, but not asexual. Trade-offs in species traits may be shaped by conflicting selection pressures imposed by habitat turnover and connectivity rather than by species interactions.

Place, publisher, year, edition, pages
2009. Vol. 161, no 3, 569-579 p.
Keyword [en]
Growth, Local processes, Metapopulation, Reproduction, Trade-offs
National Category
Biological Sciences
Research subject
Ecological Botany
Identifiers
URN: urn:nbn:se:uu:diva-107314DOI: 10.1007/s00442-009-1402-1ISI: 000269010300012OAI: oai:DiVA.org:uu-107314DiVA: diva2:228732
Available from: 2009-08-05 Created: 2009-08-05 Last updated: 2017-12-13Bibliographically 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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