A study of genetic variation in the threatened hepatic Petalophyllum ralfsii (Wils.) Nees. and Gottsche (Fossombroniaceae)

Genetic diversity of the dioicous thallosehepatic Petalophyllum ralfsii wasinvestigated and its significance for thespecies' conservation assessed. This globallythreatened hepatic apparently reaches itsgreatest abundance in the British Isles.Samples were taken from throughout the Britishrange; 178 individual thalli from 24 coloniesin nine localities were scored for variation in11 enzyme systems and 16 putative loci. Novariation was observed. Many studiesdemonstrating allozymic monomorphism inbryophytes have been of bisexual, orpredominantly vegetatively propagating taxa.Lack of variability in an obligatelyoutbreeding taxon, with no specialisedvegetative dispersal mechanism, lends supportto the view that hepatic taxa, at least withinEurope, routinely support little allozymicvariation. Unlike flowering plants, lifehistory and breeding system do not appear tohave significant effects on the extent andpartitioning of allozymic diversity.