Genetic identity affects performance of species in grasslands of different plant diversity: an experiment with Lolium perenne cultivars.
OBJECTIVE
Recent biodiversity research has focused on ecosystem processes, but less is known about responses of populations of individual plant species to changing community diversity and implications of genetic variation within species. To address these issues, effects of plant community diversity on the performance of different cultivars of Lolium perenne were analysed.


METHODS
Populations of 15 genetic cultivars of Lolium perenne were established in experimental grasslands varying in richness of species (from 1 to 60) and functional groups (from 1 to 4). Population sizes, mean size of individual plants, biomass of individual shoots and seed production were measured in the first and second growing season after establishment.


RESULTS
Population sizes of all cultivars decreased with increasing community species richness. Plant individuals formed fewer shoots with a lower shoot mass in more species-rich plant communities. A large proportion of variation in plant size and relative population growth was attributable to effects of community species and functional group richness, but the inclusion of cultivar identity explained additional 4-7 % of variation. Cultivar identity explained most variation (28-51 %) at the shoot level (biomass of individual tillers and reproductive shoots, seed production, heading stage). Coefficients of variation of the measured variables across plant communities were larger in cultivars with a lower average performance, indicating that this variation was predominantly due to passive growth reductions and not a consequence of larger adaptive plastic responses. No single cultivar performed best in all communities.


CONCLUSIONS
The decreasing performance of Lolium perenne in plant communities of increasing species richness suggests a regulation of competitive interactions by species diversity. Genetic variation within species provides a base for larger phenotypic variation and may affect competitive ability. However, heterogeneous biotic environments (= plant communities of different species composition) are important for the maintenance of intra-specific genetic variation.
Roscher
Christiane
C
Institute of Ecology, Friedrich Schiller University Jena, Dornburger Strasse 159, D-07743 Jena, Germany. croscher@bgc-jena.mpg.de
Schumacher
Jens
J
Weisser
Wolfgang W
WW
Schulze
Ernst-Detlef
ED
D044822:Biodiversity; D018533:Biomass; D014644:Genetic Variation; D008129:Lolium / Q000235:genetics* / Q000254:growth & development*; D011157:Population Dynamics; D013045:Species Specificity