CLONAL DIVERSITY AND ALLOZYME VARIATION IN POPULATIONS OF THE ARCTIC SEDGE CAREX-BIGELOWII (CYPERACEAE)

1 A study of allozyme variation in vegetatively propagating population s of the rhizomatous sedge Carex bigelowii, revealed high levels of cl onal diversity (genet diversity) within populations. The structure of allelic variation within the populations suggests that sexual reproduc tion has played a significant role in these C. bigelowii populations, despite present lack of seedling recruitment. The study was carried ou t in moss-heath communities on Icelandic lava-fields. Two adjacent pop ulations were studied at one site, while a third population was studie d at a second site, 35 km away from the first two populations. 2 The n umber of genets detected in each population, among 85-88 analysed rame ts, ranged from 41 to 55 (minimum estimate). Samples were taken every 4m along transects in the populations. Ramets with the same allozyme g enotype were often spatially aggregated. No seedlings have been observ ed in the populations during five years of demographic studies. 3 All the populations studied showed a diploid expression of allozymes and h igh levels of allelic variation, with on average 49% polymorphic loci (P), 1.77 alleles per locus (A) and an allelic diversity (H-S) of 0.16 7, Similar levels of within-population variability are found in many w ind-pollinated and outcrossing plant species. 4 The difference between observed and expected heterozygosity was small in all populations, su ggesting high levels of outbreeding. 5 Comparisons with other Carer ta xa show that the levels of and structuring of allozyme diversity in C. bigelowii is similar to that in other outbreeding species (usually rh izomatous), and much higher than in inbreeding species (which are usua lly caespitose). 6 Only 5% of the total allelic diversity was explaine d by differences between the two study sites (G(ST) = 0.055), suggesti ng extensive recent or historic gene-flow.