Diversity and dispersal of the ophiostomatoid fungus, Knoxdaviesia proteae, within Protea repens infructescences

[摘要] ENGLISH ABSTRACT: Two genera of ophiostomatoid fungi occur in the seed-bearing structures of serotinousProtea species in the Cape Floristic Region. These fungi are dispersed by arthropods,including mites and beetles that visit the Protea host plants. Although the vectors of Proteaassociatedophiostomatoid fungi are known, their dispersal patterns remain unknown –especially the manner in which recently burnt fynbos vegetation is recolonized. Additionally,their reproduction strategy has not previously been investigated. The focus of this study was,therefore, to determine the extent of within- and between-plant dispersal of Proteaassociatedophiostomatoid fungi at the population level and to investigate their reproductivestrategy. One Protea-associated ophiostomatoid fungus, Knoxdaviesia proteae, is foundexclusively in the fruiting structures of P. repens and was the focus of this study. In order tointerrogate natural populations of this fungus, 12 polymorphic microsatellite markersspecific to K. proteae were developed with an ISSR-PCR enrichment strategy andpyrosequencing. These markers were amplified in two distantly separated populations of K.proteae. The genetic and genotypic diversities of both populations were exceptionally highand neither showed significant population differentiation. The lack of population structure inboth populations implies that K. proteae individuals within a P. repens stand are inpanmixia. As one of the sampling sites had burnt recently, the process whereby youngfynbos is recolonized could be investigated. Compared to the adjacent, unburnt area, K.proteae individuals in the burnt area of this population had significantly less private alleles,suggestive of a young population that had experienced a genetic bottleneck. Knoxdaviesiaproteae individuals that did not originate from the adjacent unburnt area were encounteredwithin the burnt site and, additionally, isolation-by-distance could not be detected. Theparsimony-based haplotype networks and the tests for linkage disequilibrium indicated thatrecombination is taking place within as well as between the two distantly separatedpopulations. The observed panmixia in P. repens stands, widespread recolonization and the high genetic similarity and number of migrants between the two populations emphasizeslong-distance dispersal and therefore the role of beetles in the movement of K. proteae. Thiscohesive genetic structure and connection across large distances is likely a result of multiplemigration events facilitated by beetles carrying numerous phoretic mites.

[发布机构] Stellenbosch University