Ophiostoma africanum sp. nov., and a key to ophiostomatoid species from Protea infructescences

Persistence of ecologically similar fungi in a restricted floral niche

Fungi in the genera Knoxdaviesia and Sporothrix dominate fungal communities within Protea flowerheads and seed cones (infructescences). Despite apparently similar ecologies, they show strong host recurrence and often occupy the same individual infructescence. Differences in host chemistry explain their host consistency, but the factors that allow co-occupancy of multiple species within individual infructescences are unknown. Sporothrix splendens and K. proteae often grow on different senescent tissue types within infructescences of their P. repens host, indicating that substrate-related differences aid their co-occupancy. Sporothrix phasma and K. capensis grow on the same tissues of P. neriifolia suggesting neutral competitive abilities. Here we test the hypothesis that differences in host-tissues dictate competitive abilities of these fungi and explain their co-occupancy of this spatially restricted niche. Media were prepared from infructescence bases, bracts, seeds, or pollen presenters of P. neriifolia and P. repens. As expected, K. capensis was unable to grow on seeds whilst S. phasma could. As hypothesised, K. capensis and S. phasma had equal competitive abilities on pollen presenters, appearing to explain their co-occupancy of this resource. Growth of K. proteae was significantly enhanced on pollen presenters while that of S. splendens was the same as the control. Knoxdavesia proteae grew significantly faster than S. splendens on all tissue types. Despite this, S. splendens was a superior competitor on all tissue types. For K. proteae to co-occupy infructescences with S. splendens for extended periods, it likely needs to colonize pollen presenters before the arrival of S. splendens.

Interplay between differential competition and actions of spore-vectors explain host exclusivity of saprobic fungi in Protea flowers

Protea flowers host saprobic Knoxdaviesia and Sporothrix fungi that are dispersed by pollinating insects and birds. Different Protea species contain sympatric populations of different fungal species. For example, P. repens host S. splendens and K. proteae, while P. neriifolia host K. capensis and S. phasma. Even though all fungi can grow vigorously on alternative hosts and they share the same spore vector species, they rarely colonise alternative hosts. We investigated the role of fungal differential competitive abilities on their usual and alternative hosts to explain their host exclusivity. In a de Wit replacement series experiment, S. splendens outcompeted and later overgrew all other fungi on media prepared from its usual and alternative hosts. Host exclusivity of S. splendens on P. repens may therefore be maintained by restricted movement of spore vectors rather than weaker competitive abilities on alternative hosts. On their preferred hosts, S. splendens and S. phasma rapidly overgrew Knoxdavesia species with which they do not usually share a host, explaining host exclusivity of the Knoxdavesia species. Knoxdaviesia proteae likely only persist on P. repens with sympatric S. splendens if it colonizes flowers earlier, in a different area, or completes its life cycle before being overgrown. On their usual P. neriifolia host, K. capensis and S. phasma had neutralistic interactions and S. phasma could not overgrow K. capensis, explaining their co-existence. Host exclusivity of saprobic Protea-associated Knoxdaviesia and Sporothrix may therefore be maintained by both the activities of spore vectors and differential competitive abilities on different hosts, but the influence of other competing microbes and micro-niche differentiation cannot be excluded.

The threat of emerging and re-emerging pathogenic Sporothrix species

Sporotrichosis is a neglected subcutaneous mycosis of humans and animals acquired by traumatic inoculation of soil and plant material (classical route) contaminated with infectious propagules of the pathogen or being bitten/scratched by infected cats (alternative route). Within a genus composed of 53 species displaying an essentially environmental core, there are only a few members which have considerable impacts on human or animal health. Infections are typically caused by S. brasiliensis, S. schenckii or S. globosa. Rare mammal pathogens include members of the S. pallida and S. stenocereus complexes. To illustrate the tremendous impact of emerging zoonotic sporotrichosis on public health, we discuss the main features of the expanding epidemics driven by S. brasiliensis in cats and humans. The cat entry in the transmission chain of sporotrichosis, causing epizooties (cat-cat) or zoonosis (cat-human), has contributed to the definition of new paradigms in Sporothrix transmission, reaching epidemic levels, making the disease a serious public health problem. Indeed, S. brasiliensis infection in humans and animals is likely to become even more important in the future, with projections of its expansion in biogeographic domains and host range, as well as greater virulence in mammals. Therefore, lessons from a long-standing outbreak in the state of Rio de Janeiro about the source and distribution of the etiological agents among outbreak areas can be used to create better control and prevention plans and increase awareness of sporotrichosis as a serious emerging zoonotic disease.

Genomic overview of closely related fungi with different Protea host ranges

Genome comparisons of species with distinctive ecological traits can elucidate genetic divergence that influenced their differentiation. The interaction of a microorganism with its biotic environment is largely regulated by secreted compounds, and these can be predicted from genome sequences. In this study, we considered Knoxdaviesia capensis and Knoxdaviesia proteae, two closely related saprotrophic fungi found exclusively in Protea plants. We investigated their genome structure to compare their potential inter-specific interactions based on gene content. Their genomes displayed macrosynteny and were approximately 10 % repetitive. Both species had fewer secreted proteins than pathogens and other saprotrophs, reflecting their specialized habitat. The bulk of the predicted species-specific and secreted proteins coded for carbohydrate metabolism, with a slightly higher number of unique carbohydrate-degrading proteins in the broad host-range K. capensis. These fungi have few secondary metabolite gene clusters, suggesting minimal competition with other microbes and symbiosis with antibiotic-producing bacteria common in this niche. Secreted proteins associated with detoxification and iron sequestration likely enable these Knoxdaviesia species to tolerate antifungal compounds and compete for resources, facilitating their unusual dominance. This study confirms the genetic cohesion between Protea-associated Knoxdaviesia species and reveals aspects of their ecology that have likely evolved in response to their specialist niche.

Two new Sporothrix species from Protea flower heads in South African Grassland and Savanna

The inflorescences and infructescences of African Protea trees provide habitat for a large diversity of Sporothrix species. Here we describe two additional members, Sporothrix nsini sp. nov. and Sporothrix smangaliso sp. nov., that are associated with the infructescences of various Protea species from grasslands and savannas in the KwaZulu-Natal, North-West, Gauteng and Mpumalanga provinces of South Africa. Their description raises the number of described Protea-associated Sporothrix species to twelve. S. smangaliso sp. nov. is distantly related to other Protea-associated species and, in phylogenies using multiple markers (ITS, beta-tubulin and calmodulin), groups with taxa such as Sporothrix bragantina from Brazil and Sporothrix curviconia from the Ivory Coast. S. nsini sp. nov. resolved as sister to a clade containing four other Protea-associated species within the Sporothrix stenoceras complex. S. nsini sp. nov. was collected from within the same infructescences of Protea caffra that also contained the closely related S. africana and S. protearum. This highlights the need to study and understand the factors that influence host selection and speciation of Sporothrix in this atypical niche.

Wounds on Rapanea melanophloeos provide habitat for a large diversity of Ophiostomatales including four new species

Rapanea melanophloeos, an important canopy tree in Afromontane forests, is commonly utilised for medicinal bark harvesting. Wounds created from these activities provide entrance for many fungi, including arthropod-associated members of the Ophiostomatales and Microascales (ophiostomatoid fungi). In this study we assessed the diversity of wound-associated Ophiostomatales on storm-damaged R. melanophloeos trees in the Afromontane forests of South Africa. Five species were identified based on micro-morphological and molecular phylogenetic analyses. These included Ophiostoma stenoceras and four newly described taxa Sporothrix itsvo sp. nov., S. rapaneae sp. nov., S. uta sp. nov. and O. noisomeae sp. nov. Four of these are members of the S. schenckii-O. stenoceras complex (O. stenoceras, S. itsvo sp. nov., S. rapaneae sp. nov., S. uta sp. nov.) while O. noisomeae groups basal in the Ophiostomatales alongside the S. lignivora complex and Graphilbum. In addition to other taxa known from this host, the present study shows that there is a rich, yet still poorly explored, diversity of Ophiostomatales associated with R. melanophloeos in Afromontane forests. More taxa are likely to be discovered with increased research effort. These must be assessed in terms of pathogenicity towards this ecologically and economically important tree.

Panmixia defines the genetic diversity of a unique arthropod-dispersed fungus specific to Protea flowers

Knoxdaviesia proteae, a fungus specific to the floral structures of the iconic Cape Floral Kingdom plant, Protea repens, is dispersed by mites phoretic on beetles that pollinate these flowers. Although the vectors of K. proteae have been identified, little is known regarding its patterns of distribution. Seed bearing infructescences of P. repens were sampled from current and previous flowering seasons, from which K. proteae individuals were isolated and cultured. The genotypes of K. proteae isolates were determined using 12 microsatellite markers specific to this species. Genetic diversity indices showed a high level of similarity between K. proteae isolates from the two different infructescence age classes. The heterozygosity of the population was high (0.74 ± 0.04), and exceptional genotypic diversity was encountered (Ĝ = 97.87%). Population differentiation was negligible, owing to the numerous migrants between the infructescence age classes (N m = 47.83) and between P. repens trees (N m = 2.96). Parsimony analysis revealed interconnected genotypes, indicative of recombination and homoplasies, and the index of linkage disequilibrium confirmed that outcrossing is prevalent in K. proteae ([Formula: see text] = 0.0067; P = 0.132). The high diversity and panmixia in this population is likely a result of regular gene flow and an outcrossing reproductive strategy. The lack of genetic cohesion between individuals from a single P. repens tree suggests that K. proteae dispersal does not primarily occur over short distances via mites as hypothesized, but rather that long-distance dispersal by beetles plays an important part in the biology of these intriguing fungi.

New species of Gondwanamyces from dying Euphorbia trees in South Africa

Gondwanamyces and its Custingophora anamorphs were first described from Protea infructescences in South Africa. Subsequently these unusual fungi were also found on Cecropia in Central America. During an investigation into the decline and death of native Euphorbia trees in South Africa, several fungal isolates resembling the anamorph state of Gondwanamyces were obtained from diseased tissues. In this study these isolates are identified based on morphology and comparisons of DNA sequences. Two previously unknown Gondwanamyces species were identified, both were associated with damage caused by beetles (Cossonus sp.). Inoculation studies showed that the new species of Gondwanamyces are pathogenic on Euphorbia ingens and may contribute to the decline of these trees.

Multi-gene phylogenies define Ceratocystiopsis and Grosmannia distinct from Ophiostoma

Ophiostoma species have diverse morphological features and are found in a large variety of ecological niches. Many different classification schemes have been applied to these fungi in the past based on teleomorph and anamorph features. More recently, studies based on DNA sequence comparisions have shown that Ophiostoma consists of different phylogenetic groups, but the data have not been sufficient to define clear monophyletic lineages represented by practical taxonomic units. We used DNA sequence data from combined partial nuclear LSU and β-tubulin genes to consider the phylogenetic relationships of 50 Ophiostoma species, representing all the major morphological groups in the genus. Our data showed three well-supported, monophyletic lineages in Ophiostoma. Species with Leptographium anamorphs grouped together and to accommodate these species the teleomorph-genus Grosmannia (type species G. penicillata), including 27 species and 24 new combinations, is re-instated. Another well-defined lineage includes species that are cycloheximide-sensitive with short perithecial necks, falcate ascospores and Hyalorhinocladiella anamorphs. For these species, the teleomorph-genus Ceratocystiopsis (type species O. minuta), including 11 species and three new combinations, is re-instated. A third group of species with either Sporothrix or Pesotum anamorphs includes species from various ecological niches such as Protea infructescences in South Africa. This group also includes O. piliferum, the type species of Ophiostoma, and these species are retained in that genus. Ophiostoma is redefined to reflect the changes resulting from new combinations in Grosmannia and Ceratocystiopsis. Our data have revealed additional lineages in Ophiostoma linked to morphological characters. However, these species are retained in Ophiostoma until further data for a larger number of species can be obtained to confirm monophyly of the apparent lineages.

Multi-gene phylogeny for Ophiostoma spp. reveals two new species from Protea infructescences

Ophiostoma represents a genus of fungi that are mostly arthropod-dispersed and have a wide global distribution. The best known of these fungi are carried by scolytine bark beetles that infest trees, but an interesting guild of Ophiostoma spp. occurs in the infructescences of Protea spp. native to South Africa. Phylogenetic relationships between Ophiostoma spp. from Protea infructescences were studied using DNA sequence data from the beta-tubulin, 5.8S ITS (including the flanking internal transcribed spacers 1 and 2) and the large subunit DNA regions. Two new species, O. phasma sp. nov. and O. palmiculminatum sp. nov. are described and compared with other Ophiostoma spp. occurring in the same niche. Results of this study have raised the number of Ophiostoma species from the infructescences of serotinous Protea spp. in South Africa to five. Molecular data also suggest that adaptation to the Protea infructescence niche by Ophiostoma spp. has occurred independently more than once.

Mite-mediated hyperphoretic dispersal of Ophiostoma spp. from the infructescences of South African Protea spp

Ophiostomatoid fungi are well known as economically important pathogens and agents of timber degradation. A unique assemblage of these arthropod-associated organisms including species of Gondwanamyces G. J. Marais and M. J. Wingf., and Ophiostoma Syd. and P. Syd. occur in the floral heads (infructescences) of Protea L. species in South Africa. It has recently been discovered that Ophiostoma found in Protea flower-heads are vectored by mites (Acarina) including species of: Tarsonemus Canestrini and Fonzago, Proctolaelaps Berlese, and Trichouropoda Berlese. It is, however, not known how the mites carry the fungi between host plants. In this study, we consider two possible modes of mite dispersal. These include self-dispersal between infructescences and dispersal through insect vectors. Results showed that, as infructescences desiccate, mites self-disperse to fresh moist infructescences. Long-range dispersal is achieved through a phoretic association with three beetle species: Genuchus hottentottus (F.), Trichostetha fascicularis L., and T. capensis L. The long-range, hyperphoretic dispersal of O. splendens G. J. Marais and M. J. Wingf. and O. phasma Roets et al. seemed effective, because their hosts were colonized during the first flowering season 3-4 yr after fire.

DNA sequence comparisons of Ophiostoma spp., including Ophiostoma aurorae sp. nov., associated with pine bark beetles in South Africa

BARK BEETLES (COLEOPTERA: Scolytinae) are well-recognized vectors of Ophiostoma species. Three non-native bark beetle species infest various Pinus species in South Africa, and they are known to carry at least 12 different species of ophiostomatoid fungi. Some of these fungi have not been identified to species level. The aim of this study was to determine or confirm the identities of Ophiostoma species associated with bark beetles in South Africa using comparisons of DNA sequence data. Identities of Ophiostoma ips, O. floccosum, O. pluriannulatum, O. quercus and O. stenoceras were confirmed. Ophiostoma abietinum, O. piliferum and Pesotum fragrans are recognised for the first time and the new species, O. aurorae sp. nov., is described from pine-infesting bark beetles in South Africa.

How many species of fungi are there at the tip of Africa?

Several recent studies have reviewed the extent of fungal biodiversity, and have used these data as basis for revised estimates of species numbers based on known numbers of plants and insects. None of these studies, however, have focused on fungal biodiversity in South Africa. Coinciding with the 100th anniversary of the National Collection of Fungi (PREM) in South Africa in 2005, it is thus timely to reflect on the taxonomic research that has been conducted in South Africa over the past Century. Information is presented on the extent of fungal collections preserved at PREM, and the associated research publications that have largely resulted from this resource. These data are placed in context of the known plant and insect biodiversity, and used as basis to estimate the potential number of fungi that could be expected in South Africa. The conservative estimate is of approximately 200 000 species without taking into account those associated with a substantial insect biodiversity.

Mechanisms of fungal speciation

The objective of this review is to provide a synthesis of speciation theory, of what is known about mechanisms of speciation in fungi and from this, what is expected, and of ideas on how speciation can be elucidated in more fungal systems. The emphasis is on process rather than pattern. Phylogeographic studies in some groups, such as the agarics, demonstrate predominantly allopatric speciation, often through vicariance, as seen in many plants and animals. The variety of life history factors in fungi suggests, however, a diversity in speciation mechanisms that is borne out in comparison of some key examples. Life history features in fungi with a bearing on speciation include genetic mechanisms for intra- and interspecies interactions, haploidy as monokaryons, dikaryons, or coenocytes, distinctive types of propagules with distinctive modes of dispersal, as well as characteristic relationships to the substrate or host as specialized or generalist saprotrophs, parasites or mutualists with associated opportunities and selective pressures for hybridization. Approaches are proposed for both retrospective, phylogeographic determination of speciation mechanisms, and experimental studies with the potential for genomic applications, particularly in examining the relationship between adaptation and reproductive isolation.

The Ophiostoma piceae complex in the Southern Hemisphere: a phylogenetic study

The Ophiostoma piceae species complex incorporates several economically important species, including serious tree pathogens and agents of bluestain. The species in the complex are morphologically similar, but can be distinguished from each other based on morphology, biology, mating type studies and molecular data. At present, all the species in the complex are considered to be native to the Northern Hemisphere, most of them with a very wide distribution. Only a few sporadic reports of members of the complex are available from the Southern Hemisphere, where they are believed to have been introduced, including New Zealand, Australia, Chile, Brazil and Uruguay. This study aims to confirm the identity of isolates resembling O. piceae originating from three Southern Hemisphere countries, using mating compatibility and rDNA sequencing. Our results show that O. quercus is widely distributed throughout South Africa on both native and exotic hardwoods. O. quercus is also reported for the first time from Brazil, again from a native host. O. floccosum is reported for the first time from South Africa, but from an exotic Pinus sp. These results suggest that species of the O. piceae complex are common in the Southern Hemisphere, and that current views on the origins of especially O. quercus need to be reconsidered.