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Transplant + analysis

Due to habitat destruction and fragmentation for many plant species in Europe more populations are currently becoming extinct than are founded. A useful tool to re-establish a balance between extinctions and colonisations could be the re-introduction of species into sites where the habitat is suitable, but the species do not occur due to insufficient dispersal of seeds. However, little is known about the importance of the source of seeds for the success of reintroductions. Large populations are assumed to be less affected by genetic drift and inbreeding than small populations and may therefore be better sources of seeds. However, frequently, large local populations from which seeds could be collected are not available, whereas in other areas large populations still exist.

If plants were adapted to regional or even local environmental conditions, choosing the right source for re-introductions would be very important for the success of these measures. We carried out reciprocal transplant experiments with several plant species both at a large scale (among several European regions) and a small scale (among several sites within European regions) and studied the survival and performance of plants of different origin. The likelihood of gene flow among populations is larger in species with good dispersal ability and the generation time longer in long-lived species. Therefore, in long-lived and well-dispersed species the differentiation among populations and their adaptation to local conditions may be less pronounced than in short-lived species of poor dispersal ability.

We used three species with different life-history traits for reciprocal transplant experiments at different geographical scales: Carlina vulgaris (short-lived, monocarpic, poor dispersal ability), Hypochoeris radicata (polycarpic, high dispersal ability) and Pimpinella saxifraga (long-lived, low dispersal ability). In collaboration with the project partners (WP 3, WP4 and WP6), seedlings of C. vulgaris were reciprocally transplanted among five different European regions (Czechia, Germany, Sweden, Switzerland, Luxembourg) and among four populations of different size within these different European regions (local scale); seedlings of H. radicata were reciprocally transplanted among three regions (Czechia, Germany, The Netherlands) and within the regions among 3-4 populations each; and seedlings of P. saxifraga were reciprocally transplanted among three regions (Czechia, Germany, The Netherlands) and within the regions among 4 populations each. Survival and performance of the transplants were recorded during at least two growing seasons.

In Pimpinella the survival rate was very low in all regions independent of the origin of the seedlings. Thus, reintroduction of this species using seedlings would require large numbers. In Carlina the region of origin of the plants influenced their performance. Overall, plants from Sweden performed much worse than plants from the other regions. In Hypochoeris the effects of population origin were much weaker than in Carlina, which supports the hypothesis that differentiation among populations is stronger in the short-lived species with low dispersal ability (Carlina). The most important result was that in both species there were clear indications of adaptation at the regional scale.

Survival and overall performance of Carlina transplants were higher in their home region and decreased with increasing geographical distance to their site of origin and transplants of Hypochoeris survived best in their region of origin. At the local scale, plants from their home site performed better than plants from other populations of origin in Hypochoeris, but not in Carlina. Transplants of Carlina originating from large populations had a higher fitness than those from small populations. In Hypochoeris population size did not have an effect, suggesting that this better dispersed species was suffering less from the effects of inbreeding in small populations.

The conclusion from the studies is that plant species that occur in different European countries consist of different ecotypes that are adapted to the specific conditions in these regions. It is therefore important to conserve large viable populations in the different regions to preserve plant genetic resources. Moreover, red data lists at the regional level and management measures at that level to conserve populations of rare plants are important. Because of the strong regional genetic differentiation, a strong decline of a species in one or more regions is a reason for concern, even if at the European scale the species is not threatened. For reintroductions material from large populations within the same region should be used, in particular, if a species is not well dispersed. If no large populations are left, plants from small populations in the same region should be propagated and used.

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35043 Marburg
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