Adaptation, population viability and colonization-extinction dynamics of Silene tatarica in riparian habitats
1University of Oulu, Faculty of Science, Department of Biology
2University of Oulu, Oulanka Research Station
|Online Access:||PDF Full Text (PDF, 0.8 MB)|
|Persistent link:|| http://urn.fi/urn:isbn:9514278208
|Publish Date:|| 2005-09-06
|Thesis type:||Doctoral Dissertation
|Defence Note:||Academic Dissertation to be presented with the assent of the Faculty of Science, University of Oulu, for public discussion in Kuusamonsali (Auditorium YB210), Linnanmaa, on September 16th, 2005, at 12 noon
Accociate Professor Johan Ehrlén
Docent Veikko Salonen
Plants in riparian environments have to tolerate disturbances like floods and erosion. In the absence of disturbances, habitats will gradually become unfavorable for early-successional species. This can have fundamental consequences not only for adaptation at the individual level, but also for the viability of local populations as well as for the persistence of the species on a regional scale.
Silene tatarica is a rare perennial plant exposed to annual floods of the Oulanka River. After sand burial most plants formed vertical rhizomes and new meristems by bud ramification. The special anatomical features of these fleshy underground structures seemed to allow the plants to be very resilient against fast-flowing water. Seed structure may enhance long-distance dispersal by water. Selection gradients for plant height were positive at the individual and group levels, but for the number of stems they were in opposition, as selection at the group level favored a smaller number of stems. This can be associated with pollination and herbivory, since taller and larger plants often attract more pollinators and mammalian herbivores.
At the local level, population growth was most sensitive to the survival and growth of juvenile individuals. The populations showed different fates, and according to stochastic simulations some of them will disappear in the near future. Their colonization and extinction rates varied between the years, but their balance over the study period was positive. Small patches had the highest risk of extinction and recolonization of extinct patches was very rare. Elasticity analysis indicated that the survival of patches made a much greater contribution to patch dynamics than did the production of new patches.
The short-term dynamics of S. tatarica depend primarily on local dynamics but, in the long run, the species will track the availability of habitat, and its persistence will depend on successful colonizations. The amount of suitable habitat depends on river disturbance. Conservation of this species requires the creation of new suitable open sites for colonization, a dispersal process leading to successful colonizations, and favorable habitats for survival. These conditions can be maintained either by natural processes of river disturbance or by active conservation management.
Acta Universitatis Ouluensis. A, Scientiae rerum naturalium
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