Francois Roets

Stellenbosch University | SUN · Department of Conservation Ecology and Entomology

Flower mites are well-known nectar and pollen thieves of hummingbird-pollinated plants in the Americas, where they may reduce seed set and alter host population dynamics. They use hummingbirds for transport and are pollinators of some plants. Among African ornithophilous Protea shrubs, the hummingbird-pollination niche is occupied by sugarbirds and...

Over the past two decades, numerous Geosmithia fungi have been isolated from the bodies and galleries of wood–boring beetles. However, this genus of asexual Sordariomycetes remains taxonomically and ecologically understudied, especially in the Southern Hemisphere. In South Africa, two prior surveys reported Geosmithia species from bark beetles, but...

Sub-cortical beetles and mites contribute to tree mortality by creating wounds and by spreading potential pathogens. Here we elucidate associations between sub-cortical beetles, mites, and ophiostomatoid fungi from trees in Afromontane forests in South Africa. Bark and wood samples were collected from native tree species and exotic Pinus radiata an...

Widdringtonia is a genus of native southern African Cupressaceae trees comprising two species that occur in the mountains of the Western Cape province, South Africa. Widdringtonia cedarbergensis has a localised distribution and is critically endangered, while W. nodiflora is widespread and common. Little is known regarding the biotic associations o...

The polyphagous shot hole borer (PSHB) beetle, Euwallacea fornicatus (Eichhoff) (Coleoptera: Curculionidae, Scolytinae), and its phytopathogenic fungal symbiont (Fusarium euwallaceae Freeman et al.) threaten commercial and urban tree species worldwide. This pest–fungus complex has been newly discovered in the commercial deciduous fruit industry (We...

Mediterranean-type shrublands are rich in vascular plant diversity, but unfortunately are facing severe anthropogenic pressures including land use conversion, climate change, invasive species introductions, and alterations to their key ecological drivers. Insect diversity of Mediterranean-type shrublands remains poorly studied and we are only begin...

A highly threatened and range-restricted, mountain-relic stag beetle species in the genus Colophon Gray, 1832 (Coleoptera: Lucanidae), Colophon scholtzi Roets & Durie sp. nov. is described from a peak in the Riviersonderend Mountain range of South Africa. It is morphologically allied to species in the Colophon stokoei Barnard, 1929 species complex...

Fusarium euwallaceae , vectored by the paninvasive polyphagous shot hole borer beetle ( Euwallacea fornicatus ), is an emerging threat to trees globally. Proven pathogenic to cultivated deciduous fruits in South Africa, it recently has been isolated from cultivated European ( Olea europaea subsp. europaea ) and native African ( Olea europaea subsp....

In 2014 the blueberry bud mite, Acalitus vaccinii (Acari: Trombidformes: Eriophyidae), was detected causing significant damage to cultivated blueberries in the Mpumalanga province of South Africa. This was the first detection of this pest outside of North America, to which it is native. However, its taxonomic description at that time lacked critica...

The polyphagous shot hole borer (PSHB), Euwallacea fornicatus Eichhoff (Coleoptera: Curculionidae, Scolytinae), is a significant tree-killing pest recently introduced into South Africa. Many native trees in urban settings are susceptible to infestation, but the presence of PSHB in natural ecosystems is unstudied. The presence and drivers of PSHB co...

Benefits provided by urban trees are increasingly threatened by non-native pests and pathogens. Monitoring of these invasions is critical for the effective management and conservation of urban tree populations. However, a shortage of professionally collected species occurrence data is a major impediment to assessments of biological invasions in urb...

The polyphagous shot hole borer beetle (PSHB, Euwallacea fornicatus ) is a pest of global significance. PSHB is an ambrosia beetle which, together with its mutualistic fungi (including Fusarium euwallaceae ), can cause the death of more than 100 tree species in invaded ranges. Management of PSHB mostly relies on the removal of infested plant materi...

We present the first report of Fusarium euwallaceae and its ambrosia beetle vector Euwallacea fornicatus in deciduous fruit tree orchards in South Africa. Fusarium euwallaceae , is shown to be pathogenic to pear ( Pyrus communis ) and the beetle can establish viable colonies in this host.

Euphorbia mauritanica is a succulent shrub that is indigenous to South Africa and widely distributed throughout the country. Dying plants have been observed in their natural habitat in the Northern and Western Cape Provinces of South Africa in recent years. Stems displaying lesions were collected and the emerging cultures were identified based on I...

Cankers leading to branch, stem and plant death were observed on the South African endemic Rafnia amplexicaulis ( Fabaceae ) in the Cederberg Wilderness Area, South Africa, during September 2021. Conidiomatal pycnidia were found developing on the cankers, and isolations consistently yielded a Microsphaeropsis species. Phylogenetic analysis based on...

Context Land use change can significantly affect plant-fungal interactions. Objectives We assessed how fungal endophytes within African wild olive (Olea europaea subsp. cuspidata) twigs are influenced by different levels of land use change and differences in surrounding vegetation types. Methods Twigs were sampled in the Western Cape Province (Sout...

Host identity and location help shape fungal endophyte assemblages in plants. Hosts act as uptake filters from the environment and closely related hosts in the same location may harbour similar assemblages. We assessed the influence of host identity and geographic location on endophytic fungal assemblages within the native African olive and cultiva...

Combined studies of the communities and interaction networks of bird and insect pollinators are rare, especially along environmental gradients. Here, we determined how disturbance by fire and variation in sugar resources shape pollinator communities and interactions between plants and their pollinating insects and birds. We recorded insect and bird...

Knoxdaviesia and Sporothrix species occupy the flower heads of some Protea plants in southern Africa. Knoxda-viesia species display exceptional genetic diversity within the Core Cape Subregion (CCR) and are readily dispersed across large distances. This study aimed to determine whether overlapping ecologies have led to a similar population genetic...

Fungi Mites Ophiostomatoid Symbiosis Vector a b s t r a c t A unique microbiome occurs within the flower heads of various Protea species endemic to Africa. These include two lineages of ophiostomatoid fungi, Knoxdaviesia (Microascales) and Sporothrix (Ophiostomatales), that have members occurring exclusively in this environment and that rely on mit...

Euwallacea fornicatus (polyphagous shot hole borer, PSHB) is an invasive ambrosia beetle that infests hundreds of tree species worldwide. Damage occurs due to colonization of host sapwood with both the beetle and its fungal symbiont, Fusarium euwallaceae, which leads to Fusarium dieback disease in highly susceptible hosts. Except for almond (Prunus...

Bark beetles are destructive insect pests known to form symbioses with different fungal taxa, including yeasts. The aim of this study was to (1) determine the prevalence of the rare yeast Hyphopichia heimii in bark beetle frass from wild olive trees in South Africa and to (2) predict the potential interaction of this yeast with trees and bark beetl...

Traits mediate mutualistic and antagonistic interactions between plants and animals, and should thus be useful for predicting trophic species interactions. Studies to date have examined the importance of morphological trait matching for plant–animal interactions, but have rarely explored the extent to which these interactions are shaped by matching...

The polyphagous shot hole borer, Euwallacea fornicatus (PSHB) is an ambrosia beetle that poses a serious threat to hundreds of tree species in invaded countries. In its invaded range, it relies on a mutualistic fungus, Fusarium euwallaceae, for colony establishment and nutrition. Together, the beetle‐fungus complex can cause Fusarium dieback diseas...

Cypress canker is a branch and stem canker disease of Cupressaceae trees, particularly those in the genera Cupressus and Hesperocyparis. These trees have been planted in many parts of the world as ornamentals and the Seiridium species that cause the disease, consequently, also have an almost global distribution. The taxonomy of Seiridium species ca...

Studies addressing the economic impacts of invasive alien species are biased towards ex-post assessments of the costs and benefits of control options, but ex-ante assessments are also required to deal with potentially damaging invaders. The polyphagous shot hole borer Euwallacea fornicatus (Coleoptera: Curculionidae) is a recent and potentially dam...

Insects perform many ecosystem functions, yet their responses to disturbance can be unpredictable. Changes in climate may interact with land use disturbances, and given that arthro-pod species diversity, abundance, and traits within assemblages vary with habitat structure and climatic variables, ecological function may be impaired. Here, we assesse...

Novel species of fungi described in this study include those from various countries as follows: Australia , Agaricus albofoetidus , Agaricus aureoelephanti and Agaricus parviumbrus on soil, Fusarium ramsdenii from stem cankers of Araucaria cunninghamii , Keissleriella sporoboli from stem of Sporobolus natalensis , Leptosphaerulina queenslandica and...

Novel species of fungi described in this study include those from various countries as follows: Australia, Agaricus albofoetidus, Agaricus aureoelephanti and Agaricus parviumbrus on soil, Fusarium ramsdenii from stem cankers of Araucaria cunninghamii, Keissleriella sporoboli from stem of Sporobolus natalensis, Leptosphaerulina queenslandica and Pes...

The ambrosia beetle Euwallacea fornicatus (Polyphagous Shot Hole Borer; PSHB), native to Asia, was documented in South Africa for the first time in 2012. Death of susceptible host trees is caused by blocking of xylem tissues by the mutualistic plant-pathogenic fungus, Fusarium euwallaceae and extensive tunnelling by the beetles into the sapwood. Wi...

Reasons for the higher-than-expected soil and litter faunal diversity are still poorly understood – the so-called ‘enigma of soil animal diversity’ - especially regarding the extent of specialization of arthropod detritivores towards leaf-litter species. Here, we assess soil detritivorous arthropod diversity patterns in relation to eight, green lea...

Pathogenicity of Fusarium euwallaceae, a mutualist of the Euwallacea fornicatus beetle, was assessed on apple and grapevine following its first detection on these hosts in South Africa. Fusarium euwallaceae caused lesions in xylem tissues of apple (Pink Lady), but not grapevine (Merlot and Cabernet Sauvignon). Koch's postulates were satisfied throu...

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 c...

The mating-type (MAT1) locus encodes transcription factors essential for the onset of the sexual cycle in ascomycete fungi. This locus has been characterised in only a few heterothallic, plant pathogenic Mycosphaerellaceae and Teratosphaeriaceae. We used available genome sequences for Mycosphaerellales species to investigate the presence of two uni...

Mammals are globally in decline, with habitat loss a primary driver. There are also human–wildlife conflicts, such as elephants destroying crops, which results in the ranges of many large mammal species being fenced off. Yet, how this activity affects functional associations of insects with large mammals has received little attention. Previous work...

Contamination in sequenced genomes is a relatively common problem and several methods to remove non-target sequences have been devised. Typically, the target and contaminating organisms reside in different kingdoms, simplifying their separation. The authors present the case of a genome for the ascomycete fungus Teratosphaeria eucalypti, contaminate...

We assessed the effect of rangeland abandonment on dung beetle biodiversity and functional diversity in an African semi-desert region. Dung beetles were sampled on farms that were abandoned either over 10 years ago, abandoned one year ago, or not abandoned. We sampled from tree dominant landscape features including dry riverbeds, flatlands, and hil...

Sporothrix and Knoxdaviesia fungi use pollinators to colonize Protea flowers at anthesis. These saprobes remain dominant in the nutrient-rich, fire-retardant Protea seed-cones (infructescences) for at least a year after flowering. We tested the hypothesis that they competitively exclude potentially detrimental fungi from infructescences during this...

Teratosphaeria destructans is one of the most aggressive foliar pathogens of Eucalyptus. The biological factors underpinning T. destructans infections, which include shoot and leaf blight on young trees, have never been interrogated. Thus, the means by which the pathogen modifies its host environment to overcome host defences remain unknown. By app...

The polyphagous shot hole borer (PSHB) beetle is a recent invader in South Africa. Together with its fungal symbiont, Fusarium euwallaceae, it can rapidly kill highly susceptible host plants. Its impact is most profound in urban areas, but it has also been found infesting important forestry, agricultural crop and native species. Since its first det...

Teratosphaeria pseudoeucalypti is a fungal pathogen that causes a severe leaf blight disease on Eucalyptus trees. While presumed to be native to Australia, T. pseudoeucalypti has become well established and an important constraint to forestry in South America. The aim of this study was to use microsatellite markers to investigate the genetic divers...

Fungi in the genera Knoxdaviesia and Sporothrix dominate fungal communities within Protea flowerheads and seed cones (infructescences). Despite 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...

The diverse bacterial communities in and around plants provide important benefits, such as protection against pathogens and cycling of essential minerals through decomposition of moribund plant biomass. Biodiverse fynbos landscapes generally have limited dead-wood habitats due to the absence of large trees and frequent fire. In this study, we deter...

The Polyphagous Shot Hole Borer (PSHB) beetle is a recent invader in South Africa. Together with its fungal symbiont, Fusarium euwallaceae, it can rapidly kill highly susceptible host plants. Its impact is most profound in urban areas, but it has also been found infesting important forestry, agricultural crop and native species. Since its first det...

Replacement of complex assemblages of native mammal fauna with livestock species reduces niche heteroge-neity. This negatively affects taxa such as dung beetles, which depend on them and can, in turn, affect ecosystem functioning. We assessed the response of dung beetle diversity, biomass and body condition to cattle-farming pressures in protected...

The Eucalyptus foliar pathogen Teratosphaeria destructans causes severe and widespread damage in South-East Asian and South African plantations. In 2016, leaf blight symptoms resembling those caused by T. destructans were observed in a plantation of a Eucalyptus grandis × E. urophylla hybrid in Sabah, Malaysia. The aims of this study were to confir...

The microbial diversity associated with natural vegetation in the Greater Cape Floristic Region of South Africa is largely unexplored. As part of the Cape Citizen Science programme and independent research, surveys were conducted between 2015 and 2019 to catalogue the diversity of Phytophthora species associated with many plant species endemic to t...

An order, family and genus are validated, seven new genera, 35 new species, two new combinations, two epitypes, two lectotypes, and 17 interesting new host and / or geographical records are introduced in this study. Validated order, family and genus: Superstratomycetales and Superstratomycetaceae (based on Superstratomyces). New genera: Haudseptori...

Few economic assessments have been developed to inform national priorities on the management of high-impact, early-stage invasive alien species (IAS). Economic assessments are biased towards ex post assessments of the costs and benefits of control options and are in need of refinement to deal with potentially vigorous invaders with considerable unc...

Tree canopies in forests host exceptional levels of biodiversity. However ecologists are still faced with vast regional gaps in need of fundamental information on the nature of tree canopy diversity. The southern Afrotemperate forests at the tip of Africa are ancient, existing today as a biogeographical string of natural remnants from long-past cli...

Teratosphaeria foliar pathogens cause leaf and shoot blight on Eucalyptus trees in many parts of the world. Among them, T. destructans is one of the most aggressive pathogens causing defoliation of young Eucalyptus trees in tropic regions. Identification of T. destructans to species level is currently not possible based solely on morphological char...

To decipher the <30% of unexplained variation in leaf litter decomposition, a process important for nutrient cycling yet vulnerable to rising CO2 levels, numerous hypotheses have been proposed. The home-field advantage (HFA) hypothesis states that leaf litter decomposes more rapidly beneath canopies of tree species from which the leaves originate (...

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...

The arrival and establishment of invasive forest pests can cause devastating environmental damage and great economic impact. For example, the cost over the past decade of dealing with the arrival of a single invasive beetle in the USA, the emerald ash borer (Agrilus planipennis), is estimated at more than USD10 billion. Originating from Asia, this...

Abstract Biodiversity studies on forest canopies often have narrow arthropod taxonomic focus, or refer to a single species of tree. In response, and to better understand the wide range of drivers of arthropod diversity in tree canopies, we conducted a large-scale, multi-taxon study which (a) included effect of immediate surroundings of an individua...

The aggressive Eucalyptus leaf pathogen, Teratosphaeria destructans, causes widespread damage in tropical and subtropical Eucalyptus‐growing regions of Indonesia, China, Thailand, East Timor, Vietnam, Lao and South Africa. Little is known regarding the origin, pathways of dispersal or reproductive biology of this pathogen. The aim of this study was...

Female stag beetles (Lucanidae) possess internal mycangia to maintain microbial cultures. Yeasts from these mycangia may help with larval nutrition in nutrient poor woody substrates, but only a few Lucanidae taxa have been studied and all reports originate from Europe and Asia. We identify the first mycangial yeasts of a South African endemic Lucan...

Novel species of fungi described in this study include those from various countries as follows: Antarctica, Cladosporium arenosum from marine sediment sand. Argentina, Kosmimatamyces alatophylus (incl. Kosmimatamyces gen. nov.) from soil. Australia, Aspergillus banksianus, Aspergillus kumbius, Aspergillus luteorubrus, Aspergillus malvicolor and Asp...

Ambrosia beetles farm specialised fungi in sapwood tunnels and use pocket-like organs called mycangia to carry propagules of the fungal cultivars. Ambrosia fungi selectively grow in mycangia, which is central to the symbiosis, but the history of coevolution between fungal cultivars and mycangia is poorly understood. The fungal family Ceratocystidac...

One of the main threats to forests in the Anthropocene are novel or altered interactions among trees, insects and fungi. To critically assess the contemporary research on bark beetles, their associated fungi, and their relationships with trees, the international Bark Beetle Mycobiome research coordination network has been formed. The network compri...

Female stag beetles (Lucanidae) possess internal mycangia to maintain microbial cultures. Yeasts from these mycangia may help with larval nutrition in nutrient poor woody substrates, but only a few Lucanidae taxa have been studied and all reports originate from Europe and Asia. We identify the first mycangial yeasts of a South African endemic Lucan...

1. The present study tested the hypothesis that tree context (natural, semi‐natural or planted) and contrast (height of surrounding vegetation) affect tree physiological characters (leaf size, nutrient content, and stress‐related factors), and also alter the arthropod biodiversity patterns either directly or indirectly. 2. Arthropods were collected...

Ophiostomatoid fungi, a well-known tree-associated group, include some of the most important forest pathogens globally. Several ophiostomatoid species were reported already from Rapanea melanophloeos of the Afromontane forests from the Cape Floristic Region (CFR) of South Africa. The aim of this study was to investigate the diversity of ophiostomat...

The Eucalyptus stem canker pathogens, Teratosphaeria gauchensis and T. zuluensis (Capnodiales, Teratosphaeriaceae) are found in many tropical regions of the world where their hosts are cultivated for plantation forestry. Population genetic analyses have suggested that some populations undergo recombination, even though their sexual states have neve...

Novel species of fungi described in this study include those from various countries as follows: Antarctica , Apenidiella antarctica from permafrost, Cladosporium fildesense from an unidentified marine sponge. Argentina , Geastrum wrightii on humus in mixed forest. Australia , Golovinomyces glandulariae on Glandularia aristigera , Neoanungitea eucal...

Draft genomes of the fungal species Fusarium xylarioides, Teratosphaeria gauchensis and T. zuluensis are presented. In addition an annotation of the genome of Ceratocystis fimbriata is presented. Overall these genomes provide a valuable resource for understanding the molecular processes underlying pathogenicity and potential management strategies o...

Background: Plant-endophyte symbioses often revolve around nitrogen metabolism, and involve varying degrees of intimacy. Although evidence for vertical inheritance of nitrogen-fixing endophytic bacteria is increasing, it is confined mostly to crop plants, and to date no such system has been reported for geophytes. Methods: Bacterial endophytes asso...

Phytophthora species are important plant pathogens especially due to their ability to invade and change ecosystems. However, information regarding their diversity and distribution is not available in many parts of the world. In these areas, surveys of botanical gardens can provide opportunities to detect novel plant-microbe interactions on both ind...

Communities are mostly composed of rare species; yet, the factors that determine their patterns of occurrence remain obscure. Theory predicts that, in contrast with common species, the occurrence of rare species will be poorly correlated with environmental variables (niches) and more affected by stochasticity (ecological drift), but how this patter...

Forests are sensitive ecosystems with a distinctive micro-climate to which forest arthropods have adapted. In intact primary forests, sunlight only fully reaches forest floors temporarily through tree fall, or more permanently at forest edges. Roads that cut through pristine forests are however permanent features that fragment forests and increase...

Insect predator densities and plant nutritional status can affect insect herbivore densities, but these effects have not yet been assessed in the context of an invasive species management. This study investigated the influence of (i) altered predatory arthropod abundance and community composition (top-down-effects); and (ii) altered leaf nitrogen a...

There has been a recent increase in new records of insects from the subtropical parts of South Africa that have expanded their historic ranges to now include the biologically and climatically atypical south-western Cape region at the tip of the African continent. Suggested mechanisms include climate change, provision of previously absent nutriments...

The European paper wasp Polistes dominula has invaded many parts of the globe and often displaces similar native species. Factors contributing to this remain unclear but may include longer seasonal activity period, natural enemy release, greater colony productivity and smaller body size. Since its discovery in South Africa in 2008, the local abunda...

Strip mining in arid ecosystems causes extreme ecological destruction that may take decades to recover. The present study examined the effect of different plant-community rehabilitation treatments on arthropods after strip mining in the arid Namaqualand region of South Africa. Vegetation cover and plant species richness were significantly lower at...