Ploidy level, genetic diversity, and differentiation in two closely related mosses, Scorpidium cossonii and S. revolvens (Calliergonaceae)

Abstract

As ploidy level and mating system can affect genetic diversity and differentiation, we conducted population genetic analyses of two closely related mosses, Scorpidium cossonii (Schimp.) Hedenäs, and S. revolvens (Sw. ex Anonymo) Rubers which differ in ploidy level and sexual system. We collected 315 specimens in total from five populations of S. cossonii and four populations of S. revolvens in the Swiss Alps. Ploidy level, genetic diversity within populations, and genetic differentiation between populations and species were estimated using nine microsatellite markers. In each S. cossonii sample, each locus bore only one allele, while in S. revolvens, seven out of the nine loci were fixed or nearly fixed for two alleles per locus per individual. These findings are consistent with a gametophytic haploid S. cossonii and allodiploid S. revolvens. The haploid and dioicous S. cossonii was genetically more diverse than the (allo)diploid and monoicous S. revolvens. Differences in genetic diversity between the two species may be explained by different mating systems, different population sizes, and different population histories. Genetic differentiation among populations of S. cossonii was higher than among those of S. revolvens. The low genetic differentiation among populations of the monoicous species was not unexpected, since monoicous species frequently produce sporophytes, long-distance spore dispersal is more likely and leads to low differentiation.

Keywords:

• Allodiploidy
• Calcareous fen
• Dioicous
• Haploid
• Monoicous

Acknowledgements

This study was supported by a scholarship to YK (Higher Educational Strategic Scholarships for Frontier Research Network, Thailand) and a grant from the Federal Office for the Environment to AB and CS (00·0294.PZ/J462-2334). SW was supported by a Marie Curie Fellowship (LICHENOMICS) within the People programme of the European Commission (FP7) and received logistic support from University of Iceland. The authors thank the Genetic Diversity Centre, ETH Zurich for technical assistance, L. Excoffier for statistical advice, T. Karpati for help with various methodological issues, L. Hedenäs for commenting on an earlier draft of the manuscript, and two anonymous reviewers for their helpful comments.

Taxonomic Additions and Changes: Nil.