Dispersal potential of spores and asexual propagules
in the epixylic hepatic Anastrophyllum hellerianum |
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Authors: | Maria Pohjamo Sanna Laaka-Lindberg Otso Ovaskainen Helena Korpelainen |
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Institution: | (1) Department of Applied Biology, University of Helsinki, P.O. Box 27, FI-00014 Helsinki, Finland;(2) Lammi Biological Station, FI-16900 Lammi, Finland;(3) Department of Biological and Environmental Sciences, University of Helsinki, P.O. Box 65, FI-00014 Helsinki, Finland |
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Abstract: | Dispersal ability is of great importance for plants, which commonly occupy spatially and temporally limited substrate patches.
Mixed reproductive strategies with abundant diaspore production are favoured in a heterogeneous landscape to ensure successful
colonisation at different distances. In bryophytes, long-distance dispersal has been thought to take place primarily by spores,
while asexual propagules are important in local dispersal and in the maintenance of colonies. In the present study, we investigated
the dispersal potential of two equally sized propagules, sexually formed spores and asexually produced gemmae in the dioecious,
epixylic hepatic, Anastrophyllum hellerianum, which inhabits spatially and temporally limited substrate patches. We trapped propagules at different distances (0–10 m)
and directions from the source colonies in two experiments: one in a natural habitat within a forest and another involving
an artificial set-up in an open habitat. Spore dispersal showed only slight distance dependence both in the open and the forest
habitats, presumably as a consequence of wind affecting the dispersal pattern. Gemma dispersal was more strongly distance-dependent
in the open habitat than in the forest sites. Considerably more gemmae were deposited during rainy than dry periods, possibly
because of the effect of rain drops on gemma release. However, weather conditions had no effect on the dispersal patterns
of spores or gemmae. In A. hellerianum, the combination of occasional spore production and practically continuous, massive gemma production facilitates dispersal
both on local scale and over long distances. Unlike previously assumed, not only spores but also the asexual propagules may
contribute to long-distance dispersal, thus allowing considerable gene flow at the landscape level. |
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Keywords: | Bryophytes Deposition pattern Diaspores Fragmented habitat Mode of reproduction Old-growth forest |
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