Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Reciprocal sowing

The objective of this study was to investigate whether plants of the monocarpic perennial composites Tragopogon pratensis and Carlina vulgaris show local adaptations at a small scale within populations. The two species differ in their dispersability: Dispersal of the seeds of Carlina is relatively poor in comparison to the dispersal of the seeds of Tragopogon. This difference in dispersability may affect the degree of local adaptation in the two species. It was expected that Carlina, which is relatively poorly dispersed, would be locally adapted to a higher degree than the more better dispersed Tragopogon.

This study complements the larger scale adaptation studies (see 9380). To study the occurrence of small-scale (within-population) local adaptation, reciprocal transplant experiments were carried in one German population of each species. Ten mother plants of each species that were growing within 300m of each other were selected, their position marked, and the seeds of these plants were collected and germinated in the greenhouse. Several seedlings from each mother plant were then transplanted into the vicinity of each mother plant.

A number of fitness-related traits (survival, growth, flowering) was examined in the transplants over two growing seasons. No evidence for small-scale local adaptation was found in the species. There was no home site advantage and no effect of distance to the mother plant. Instead, some target sites were consistently favourable and others unfavourable irrespective of the origin of the transplants. These differences in performance could not be related to habitat characteristics recorded at the target microsites.

The results indicate that even in populations that are not obviously heterogeneous, there is strong spatial heterogeneity in the quality of microsites for plants at a small scale. This is surprising, because the successful reproduction of the mother plants indicates that all microsites had been favourable for the species. Local adaptation appears not to be important at this scale; selection may be too weak and genes flow too strong for local adaptation to develop. In conclusion, the results suggest that in restoration projects seeds should be broadcast over the whole site to increase their probability of reaching at least some favourable microsites.

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