Conservation genetics relies two main underlying assumptions that remain so far untested. The first is the existence of a relationship between the genetic component of biodiversity and populations 'evolutionary capital', i.e. they capacity to cope with environmental fluctuations. The second is the existence of a straightforward relationship between the molecular markers used, so far mostly considered as neutral, and the diversity of the genome as a whole, including markers potentially submitted to selection.
Experimental studies have been thus far mostly performed on seagrasses and provided evidence for a positive effect of genotypic diversity (i.e. the number of different clones in an experimental quadrate) on the resistance and/or resilience of populations of Zostera marina to experimental perturbations. Contradicting evidence however arise from field data, that depending on studies showed a either a positive (Z. marina) or a negative relationship (Z. marina , P. oceanica) between clonal diversity and the demographic status or resistance of populations to environmental forcing. Confronting those results, it appears that long term intraspecific competition through clonal growth may for example be neglected in experimental populations, and more generally that the distinct time and complexity scales are grasped by different experimental and field studies. Moreover, genetic diversity sensus stricto, i.e. allelic richness or heterozygosity, was not formally tested for thus far and may have a cross cutting influence with genotypic richness on the overall resistance or resilience of populations.
Experimental quadrates of increasing genotypic and allelic richness of Z. noltii were followed through an instant perturbation while long term field survey of genetically characterized meadows of Z. marina were used, in order to test further for the influence of genotypic and genetic diversity over various time scales.
Results/Conclusions
The results desmonstrate a predominant influence of genotypic richness on the short term response to high perturbation, while strong relationship was observed between genetic diversity and longer term demographic response of natural populations to forcing environmental parameters.
The synthesis of those studies with previous experiments and surveys supports the importance of both genotypic and genetic components of biodiversity on the resistance and/or resilience of populations to environmental fluctuations. It also confirms the accuracy of putatively neutral markers to reflect the diversity of the genome, including genes involved in the response to selective pressures.
