Dispersal in a sterile lichen-forming fungus,Thamnolia subuliformis(Ascomycotina: Icmadophilaceae)This paper is one of a selection of papers published in the Special Issue on Systematics Research.

Abstract

Thamnolia subuliformis (Ehrh.) Culb. is a sterile lichen-forming ascomycete with no known sexual or vegetative reproductive structures except fragments of thallus branches. The open tundra in northern Manitoba contains fragments of T. subuliformis randomly scattered over the landscape, giving the appearance that dispersal is common. This may provide a misleading impression of gene flow, but similar fragmentation is seen in seven other locally occurring species of lichen-forming fungi. The primary objective of this study was to examine the population structure of T. subuliformis using four multilocus markers (interspersed simple sequence repeats; ISSR) and a single locus marker (the presence/absence of a group I intron in the nuclear 18S rDNA locus). Significant population subdivision is reported for two different classifications of what constitutes a population. Thallus fragments of T. subuliformis may be intact and slow growing, having accumulated tissue over a long period of time, with low levels of gene flow occurring in localized areas. The presence of the group 1 intron in localized transects may suggest either that the intron was introduced recently and has not had sufficient time to disperse among populations, or that it has been lost in other locations.