Three species of higher algicolous fungi were examined at the autecologica1, cultural, light microscope, and scanning and transmission electron microscope levels. Fungal development and the host-parasite relationship are described for each association. The seasonal occurrence of marine fungi from intertidal populations of Dilsea carnosa, Ascophyllum nodosum and Chondrus crispus was examined at Bembridge, Isle of Wight, UK. A basidiomycete pathogen, Mycaureola dilseae, was found on D. carnosa, and two ascomycetes, Mycosphaerella ascophylli and Lautitia danica, on A. nodosum and C. crispus, respectively. Mycaureola dilseae is host specific and exhibited a limited reproductive cycle with green necrotic lesions and basidiomata observed only during September and October. Mycosphaerella ascophylli is an obligate endophyte of A. nodosum, an association in which the fungal and algal reproductive cycles were found to be synchronous with sporocarps confmed to host receptacles. This fungus is also found in Pelvetia canaliculata. Sporocarps of L. danica were recorded on cystocarpic C. crispus throughout the year, with a higher incidence of the fungus on older fronds. Tetrasporic C. crispus was also infected and in both cases the fungus was confmed to algal reproductive tissues. Mycosphaerella ascophylli was isolated from A. nodosum and P. canaliculata tissues and the anamorph, Septoria ascophylli was induced to sporulate. Growth of M. di/seae from D. carnosa lesions was limited and Lautitia danica could not be isolated from infected C. crispus tissues. Ascospore (L. danica and M. ascophylli) and basidiospore (M. di/seae) cultures did not grow beyond the germ tube phase. Hyphae of M. dilseae grew both inter- and intra-cellularly in D. carnosa. Penetration of algal cells was initially achieved by fme bifurcated penetration hyphae and there is evidence of mechanical pressure and localized enzyme action. The fungus caused a progressive breakdown of algal cell walls and cell contents; particularly evident was the damage to chloroplasts and dissolution of Floridean starch grains. Infection fmally resulted in the formation on necrotic lesions, each surrounded by a ring of basidiomata. Transmission electron microscopy showed the ascus of M. ascophylli to be bitunicate with a thick endoascus and thin ectoascus. Intra-membranous haustoria were occasionally observed in the outer cell wall of A. nodosum and P. canaliculata. Lautitia danica asci were bitunicate and ascospores were covered with a mucilagenous layer. Penetration of host cells caused extensive damage and blackening of host reproductive tissues. The relevance of these results are discussed in relation to algal pathology and marine fungal ultrastructure.

No description available.

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

Not available / text

Not available / text

Not available / text

published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Thesis (MSc)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Five new species of ophiostomatoid fungi, colon ising the infructescences of serotinous Protea species, have recently been discovered in South Africa. Prior to this, ophostomatoid fungi were thought to be restricted to the Northern Hemisphere. The discovery of these five species thus extensively expanded the known geographical range of these fungi, now also to include the Southern Hemisphere. Since this discovery, few studies have focused on the interesting ecology of this group, which is uniquely adapted for spore dispersal by arthropods. Studies focussed on ophiostomatoid fungi provide an unique opportunity to study inter-organism interactions between fungi, their host plants and the arthropods responsible for their spore dispersal. Very few similar studies have been undertaken, particularly in the Fynbos Biome, to which most of our economically important Protea species are confined. The current study provides insight into some ecological aspects of these complex interactions. The seasonal distribution of the ophiostomatoid fungi associated with the infructescences of members of the Proteaceae was investigated. Definite seasonal patterns were observed, with peak fungal colonisation occurring during the wetter winter months. While determining the host specificity of these fungi, a new Protea host for Ophiostoma splendens was identified, and a new species of Rhyncomeliola was discovered. All ophiostomatoid species native to Fynbos in the Stellenbosch region are exclusively associated with the infructescences of species in the plant genus Protea. By employing a multiplex Polymerase Chain Reaction (PCR), a set of group specific primers was developed for the identification of South African Ophiostoma and Gondwanamyces fungal DNA. This newly developed method was used to scan arthropods collected from the infructescences of P. repens for the presence of 0. splendens and G. proteae spores. By using these group-specific primers, three insects possibly responsible for long range dispersal of fungal spores were identified. Three further insect species, possibly contributing to the short-range dispersal of ophiostomatoid spores, were also implicated through this method. All arthropods associated with the fruiting structures of selected members of the Proteaceae were also investigated. A total of 62 pseudospecies (ca. 7500 individuals), belonging to 45 different arthropod families, were collected. Proteaceae species with larger fruiting structures housed more arthropod species and higher numbers of individuals than Proteaceae taxa with smaller fruiting structures. Some plant species housed similar arthropod communities, while others housed unique suites of arthropods. Seasonal patterns in arthropod numbers were observed, and it was found that, in most instances, arthropod numbers peaked during the autumn and winter months. Twenty-five fungal taxa were isolated from various Proteaceae arthropods, many of which are genera known to include Proteaceae pathogenic species. Ophiostomatoid fungi have a saprophytic relationship with their Protea hosts, and may deter some of these potentially harmful fungi from colon ising the infrutescences. Some fungi showed a high degree of specificity towards potential vectors, while others were found on a diverse range of arthropods. This study highlights the existence of complex inter-organismal interactions within the Fynbos Biome, a study area where the interactions between plants, fungi and insects have been grossly neglected. The few studies that have been conducted in this field have mostly focussed on a limited number of organisms, and no wide-scale attempts, such as presented here, have been published. It is important to obtain a holistic view in any ecological study that focuses on interactions between different suites of organisms. Ultimately this will aid in the development of better conservation strategies. This study thus provides a muchneeded start in studies on multi-organismal interactions in the Fynbos Biome. / AFRIKAANSE OPSOMMING: Vyf nuwe ophiostoma-agtige fungus spesies is onlangs in die vrug-liggame van Suid Afrikaanse Protea plante ontdek. Voor hierdie ontdekking, was die algemene opvatting dat ophiostoma-agtige fungi beperk is tot die Noordelike Halfrond. Die ontdekking van hierdie vyf spesies het dus die bekende geografiese verspreiding van hierdie tipe fungi vergroot om nou ook die Suidelike Halfrond in te sluit. Sederdien het min studies gefokus op die interesante ekologie van hierdie groep, wat aangepas is vir spoorverspreiding deur geleedpotiges. Studies wat fokus op die ophiostoma-agtige fungi voorsien 'n unieke geleentheid om die inter-organismiese-interaksies tussen fungi, hul gasheer plante en die geleedpotiges wat hul spore versprei, te bestudeer. Baie min soortgelyke studies is al voorheen in die Fynbos Bioom, waar die meeste van ons ekonomies-belangrike Protea spesies voorkom, onderneem. Die huidige studie verleen meer inligting oor sommige ekologiese aspekte van hierdie komplekse interaksies. Seisoenale verspreidingspatrone van ophiostoma-agtige fungi geassosieer met die vrug-liggame van lede van die Proteaceae, is ondersoek. Daar is defnitiewe seisoenale patrone in die aanwesigheid van fungi gevind, met 'n piek in fungi kolonisasie-getalle gedurende die vogtiger wintermaande. 'n Nuwe Protea gasheer vir Ophiostoma splendens en 'n nuwe fungus spesie (Rhyncomeliola sp.), is ontdek. Alle Fynbos ophiostoma-agtige spesies in die Stellenbosch area, is beperk tot Protea spesies. 'n Multipleks Polimerase Ketting Reaksie is ontwikkel om die spesifieke DNS van ophiostoma-agtige fungi te herken. Hierdie metode is gebruik om te toets vir die aanwesigheid van spore van hierdie fungi op die liggame van geleedpotiges (geassosieerd met P. repens). Hierdeur is drie insekte wat waarskynlik verantwoordelik is vir die langafstand verspreiding van spore geidentifiseer. Drie verdere insekte wat moontlik verantwoordelik is vir die kortafstand verspreiding van ophiostoma-agtige fungi is ook aangewys. Alle geleedpotiges geassosieer met die vrugstrukture van geselekteerde lede van die Proteaceae is ondersoek. 'n Totaal van 62 pseudo-spesies (omtrent 7500 individue), wat tot 45 families behoort, is versamel. Proteaceae spesies met groter vrugstrukture het meer geleedpotige spesies en individue gehuisves as taksa met kleiner vrugstrukture. Sommige plant spesies het soortgelyke geleedpotige gemeenskappe gehuisves, terwyl unieke groepe geleedpotiges in ander plante voorgekom het. Alhoewel die geleedpotiges seisonale variasies in getalle geopenbaar het, het die meeste groepe 'n piek in getalle getoon gedurende die herfs- en wintermaande. Vyf-en-twintig fungi taksa is geïsoleer vanaf verskeie Proteaceae geleedpotiges. Sommige van hierdie is genera wat Proteaceae patogeniese spesies insluit. Sommige fungi het 'n hoë graad van spesifisiteit teenoor potensiële vektore getoon, terwyl ander weer algemeen op verskeie geleedpotige spesies gevind is. Hierdie studie dui op die bestaan van komplekse inter-organismiese-interaksies in die Fynbos Bioom, in 'n area waar die studie van interaksies tussen plante, fungi en insekte nog baie min aandag geniet het. Die beperkte aantal studies wat tot dusver in hierdie veld onderneem is, fokus gewoonlik slegs op 'n paar organismes. Geen grootskaalse studies, soos die een hier voorgelê, is al gepubliseer nie. In enige ekologiese studie wat fokus op interaksies tussen verskeie organismes, is dit belangrik om 'n holistiese siening te probeer verkry. Uiteindelik sal dit bydra tot die ontwikkeling van beter bewarings-strategië. Hierdie studie verleen dus 'n noodsaaklike begin tot studies op multiorganismiese- interaksies.

Fungal endophytes are highly diverse, cryptic plant endosymbionts that form asymptomatic infections within host tissue. They represent a large fraction of the millions of undescribed fungal taxa on our planet with some demonstrating mutualistic benefits to their hosts including herbivore and pathogen defense and abiotic stress tolerance. Other endophytes are latent saprotrophs or pathogens, awaiting host plant senescence to begin alternative stages of their life cycles. Most, however, are likely plant commensals with no observable benefits to their hosts while under study. Yet, when considering the context-dependence that may determine plant resistance to pathogen attack, the consortium of endophytes present in the host could alter these outcomes, thereby affecting plant evolution. Despite the excitement of exploiting endophytes for their potential to produce bioactive compounds that are useful to medicine and agriculture, fungal endophyte community ecology is a lagging field. Much remains unknown regarding their colonization patterns within hosts, their spatial and temporal turnover and their diversity. Further, a severe deficiency exists in work on endophytes in seed-free plants, particularly ferns. Since ferns exist in free-living forms in both the haploid and diploid stages, are the second largest group of vascular plants, occupy important ecological niches and represent an older lineage of land plants, this is a major shortcoming in our understanding of plant-fungal ecology and evolution. For these reasons, I have examined endophyte community ecology in a widespread fern host in the Pacific Northwest, Polystichum munitum, addressing several gaps in the endophyte literature. Since an understanding of the degree of early endophyte colonization, temporal turnover and the relative contribution of priority effects to community composition are unknown, I conducted a temporal survey of fern endophyte communities utilizing culture-independent, next-generation sequencing on a monthly basis for an entire growing season. A high degree of temporal turnover was observed early in the growing season, where a late colonist rapidly took over the fern population and persisted throughout the year. This colonist, which was isolated from several of the same plants, appears to support growth rates of the host plant when in the gametophytic stage, but is not highly competitive against other endophytes in vitro. Additionally, in an effort to examine host and habitat specificity I examined the spatial turnover of endophytes across four distinct habitat types: a coastal site, a coniferous understory site, a montane site near Mount Saint Helens but not impacted by the 1980 eruption, and a secondary succession site at Mount Saint Helens, spanning 150-km at a single point in time. A high degree of host specificity was found when compared to endophyte communities in neighboring plant taxa and a lack of distance decay was also observed contrasting with other work examining endophyte biogeographic patterns. We conclude that a high degree of host filtering, combined with an abundance of senescent fern material around the base of the plant--which potentially serves as a reservoir of endophyte inoculum--is likely responsible for the observed results. In the process of the ecological studies described above, I isolated over 500 strains of endophytes that corresponded to ca. 100 operational taxonomic units (OTUs). Four of these OTUs are previously undescribed and form a new family and genus, Catenosporaceae and Catenospora, respectively. One of these taxa is responsible for the strong spatial and temporal signals found in the ecological studies. We emphasize that future work should examine if the same phenomena are observed in other fern systems and further encourage endophyte researchers to expand the scope of their investigations into non-traditional plant lineages, as exciting ecological interactions that contribute to our understanding endophyte ecology--and community ecology as a whole--are waiting to be discovered.

Not available / text