Abstract
This thesis describes a journey of discovery of the reproductive mechanisms used by certain members of the Icmadophilaceae – a group of lichens about whose reproductive mechanisms there has been much confusion in the academic literature. This thesis focuses on Icmadophila splachnirima, a rare lichen that occurs mostly in endangered subalpine boggy habitats of New Zealand and South-East Australia. It grows on continuously moist peaty soil, over mosses and plant debris, within a landscape dominated by tussock and low shrubs. It is found in Victoria, Tasmania, the South Island of New Zealand, Stewart Island, Chatham Islands and the subantarctic Auckland and Campbell Islands. A comprehensive geo-referenced compilation of all currently known localities of this species provided. This thesis describes a molecular genetic reassessment of the genus Icmadophila and provides evidence supporting the reinstatement of the genus Knightiella, comprising the single species Knightiella splachnirima. Also the recently described Icmadophila eucalypti belongs in a genus of its own, leaving only three species in Icmadophila s. str. Contrary to previous reports, it is shown that the type species of the genus, I. ericetorum, does most likely not occur in New Zealand.
A population genetic approach was used to examine whether gene flow exists between the very disjunct known populations of the focal species and to assess the relative importance of sexual versus vegetative propagules for long distance dispersal. Evidence is provided that I. splachnirima is most likely not self-fertile. Sexual reproduction via ascospores is the primary mechanism for long-distance dispersal, and the spores can combine with multiple algal partners of Coccomyxa s. lat. Furthermore, field experiments show that under unfavourable environmental conditions, particularly insufficient hydration, the species can reversibly resort to vegetative reproduction.
Based on this reproductive strategy, the author assumes that populations of I. splachnirima will be able to maintain themselves in their natural environment, in spite of potentially deteriorating habitat conditions in the course of climatic change. However, especially small and isolated populations may not be able to recover from genetic bottenecks and habitat loss due to anthropogenic activity. Therefore, monitoring of small and isolated populations is advised, and if necessary, transplants of compatible mating partners should be considered to ensure their long-term survival.
In the course of the research undertaken for this thesis, the author observed and proved that sexual reproduction occurs in two other members of the family Icmadophilaceae, Siphula decumbens and S. fastigiata, whose ability for sexual reproduction had previously been unknown. The resurrenction of the genus Nylanderiella is proposed for the Siphula decumbens group.