Genetic diversity and fitness in Scabiosa columbaria in the Swiss Jura in relation to population size
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- Pluess, A.R. & Stöcklin, J. Conservation Genetics (2004) 5: 145. doi:10.1023/B:COGE.0000029999.10808.c2
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Due to changes in land use, remnants ofunfertilised, nutrient-poor calcareousgrassland in the Swiss Jura are small in areaand are highly fragmented. We selected 89 seedfamilies from eleven populations of varioussizes of Scabiosa columbaria for a studyof molecular diversity, and used the samematerial in a greenhouse experiment to measurevariation in fitness-related traits and theability of populations to cope withcompetition. Using RAPD-PCR we detected 71RAPD-phenotypes among 87 genotypes. Moleculardiversity within populations was variable andrelatively high, with an expectedheterozygosity He ranging from 0.09 to0.24. He, the Shannon index (SI) and thepercentage of polymorphic bands were notcorrelated with population size, but thesmallest populations had the lowest moleculardiversity (He, SI). Populationdifferentiation was moderate with 12% of themolecular diversity among populations. Measuresof fitness in the greenhouse differed amongseed families (P < 0.001), but not amongpopulations. Mean above-ground biomass waslargely reduced when plants had to compete withBromus. Mean fitness of populationsdecreased when molecular diversity (He)was low, but only when plants had to competewith Bromus (P = 0.02). Accordingly, therelative competition ability of Scabiosaplants decreased when molecular diversity(He) was low (P = 0.01). Our resultssuggest an increased risk of local extinctionof Scabiosa columbaria in the Swiss Juracaused by a decreased viability and reducedphenotypic plasticity due to genetic erosion insmall populations.