An isozyme study of clone diversity and relative importance of sexual and vegetative recruitment in the grass Brachypodium pinnatum

Abstract

We asked whether differences in abundance and seed prodtiction of Brachypodium pinnatum after 16 yr of four different experimental land use regimes were reflected in differences in vegetative dispersal distance, clone diversity, clone area, and the proportions of sexual and vegetative recruitment. Mean vegetative dispersal distance was 5.5 mm yr‘. Electrophoresis of 5 polymorphic isozyme loci of 20 tillers sampled at defined positions in each of twelve 1 × 6 m sampling areas (3 per treatment) revealed considerable clonal diversity. Per sampling area we found on average 9.98 enzyme phenotypes (clones), mean Simpson index was 0.825. and mean Shannon index 0.801. The mean ratio of sexual vs vegetative recruitment was about 1:32000. Despite this low ratio, clonal diversity within the population of” B. pinnatum was higher than reported for other clonal plant populations, possibly because of its high ramet densities. Moan clone area was 5.73 m2‐. i.e. mean clone radius was 1.35 m. None of the 10 pairwise correlations between abundance and seed production on the one hand, and number of clones per plot sample, plot Simpson index, plot Shannon index, ratio of vegetative vs sexual recruitment, and clone area on the other, was significant. Mean clone radius was 245 times larger than the mean distance of yearly vegetative dispersal which suggests old ages and low turnover rates of clones. The time scale of the inert response of clonal diversity of B. pinnatum to changes in land use appears to largely exceed the experimental period of 16 yr.

On the evolution of clonal plant life histories

“…When molecular data are combined with spatial data on the location of ramets and on the distance between vegetative parent and offspring, they allow the estimation of the ratio of sexual vs . vegetative recruitment (Harada el al., 1997;Schlapfer and Fischer, 1998). Moreover, because [354] molecular genetic markers are assumed to be selectively neutral, they provide useful tools in the study of non-adaptive evolutionary forces such as genetic drift, inbreeding and gene flow (Hartl and Clark, 1994;Ouborg et al, 1999).…”

The Relation Between Unpalatable Species, Nutrients and Plant Species Richness in Swiss Montane Pastures

“…Gough and Grace 1998;Todd and Hoffman 1999). Many grassland plants are long-lived and it may therefore take a long time before the effects of experimental treatments are reflected in vegetation composition and species richness (Schla¨pfer and Fischer 1998). An alternative approach is to study vegetation patterns in grasslands that have been grazed for long periods of time.…”

Spatial genotypical diversity of Sesleria albicans (Poaceae) in a dry grassland community

“…The number of identified genotypes in the studied population (49 genets per m 2 ) is considerably higher than the number of genotypes observed for other grasses, e.g. 1.67 genets per m 2 for Brachypodium pinnatum (Schläpfer & Fischer 1998), 27-33 genets per m 2 for Festuca rubra (Suzuki et al 1999), 7.67 genets per m 2 for Festuca novae-zelandiae (Lord 1993). This fact could imply that in S. albicans generative reproduction plays an important role.…”