Recent disease surveys in the Western Cape province of South Africa have revealed a previously unknown and serious stem canker disease on native Rapanea melanophloeos (Myrsinaceae, Ericales) trees. ...Cankers commonly result in the death of branches or entire stems. Fruiting structures typical of fungi in the Cryphonectriaceae were observed on the surfaces of cankers. In this study, the fungus was identified and its pathogenicity to R. melanophloeos was tested. Multigene phylogenetic analyses based on DNA sequences of the partial LSU gene, ITS region of the nuclear ribosomal DNA gene and two regions of the β‐tubulin (BT) gene, showed that the fungus represents a formerly undescribed genus and species in the Cryphonectriaceae. The fungus was also morphologically distinct from other genera in this family. Inoculation trials showed that the fungus described here as Immersiporthe knoxdaviesiana gen. et sp. nov. is an aggressive pathogen of R. melanophloeos trees.
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 partial nucleotide sequences of the internal transcribed spacers (ITS), the nuclear large subunit (LSU) and RNA polymerase II second largest subunit ( RPB2 ) regions showed that the fungus represented an undescribed species. Based on the multigene phylogeny and morphological characteristics, we describe the species here as M. rafniae sp. nov. Pathogenicity tests and the fulfilment of Koch’s postulates confirmed that M. rafniae sp. nov. is the cause of the cankers of R. amplexicaulis . Presently, this disease is known from a single location in South Africa, and further surveys are required to determine its distribution and relative importance.
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 diversity of
T. pseudoeucalypti
outbreaks occurring in plantations in two distinct environments. In the New South Wales (NSW) plantation in Australia, a hybrid of two native
Eucalyptus
species was planted outside of its natural environment. In contrast, the plantations in Uruguay were of a non-native
Eucalyptus
species. Sixteen polymorphic microsatellite loci, identified in two genomes of
T. pseudoeucalypti
, were used to genotype 36 individuals from the NSW plantation and 21 were collected from across Uruguay. Genetic diversity in the NSW population was low (
H
exp
= 0.05), comprising five genotypes of which one occurred in > 80% of individuals. Despite high clonality and one
MAT1-1
isolate among many
MAT1-2
isolates, different genotypes co-occurred on a single tree and the hypothesis of recombination was not rejected. The diversity in the NSW plantation was consistent with that of an introduced pathogen, either from the surrounding native forests, or supporting earlier findings that
T. pseudoeucalypti
has only recently established in NSW. All isolates from Uruguay were clonal, harbouring the
MAT1-1
idiomorph and a genotype distinct from those in Australia. This clonality suggests a single introduction of
T. pseudoeucalypti
into that country.
There has been a recent increase in new records of insects from the subtropical parts of South Africa that have expanded their historical ranges to now include the biologically and climatically ...atypical southwestern Cape region at the tip of the African continent. Suggested mechanisms include climate change, provision of previously absent nutriments and direct transport of individuals via human activities. Here we summarise previous reports of fruit chafer beetles (Scarabaeidae: Cetoniinae: Cetoniini) invading the southwestern Cape region, provide additional data on their distributions and provide data for additional taxa that have now also been newly recorded in the region. The newly reported species Pachnoda sinuata sinuata probably naturally occurs in the region but has gone unnoticed due to specialised habitat requirements and morphological similarity to a widespread generalist. Some taxa are very recent arrivals while others have been known from the region for a long time, but all are experiencing noticeable population increases in urban and agricultural areas. We propose that these species likely dispersed from their native ranges to the southwestern Cape via direct transport of colonised nursery stock and their recent increases in population size are consistent with what is expected when founder populations overcome barriers to reproduction. All of the new arrivals are well-adapted to transformed landscapes in the subtropics and do not occupy natural vegetation in the newly invaded ranges, strengthening the hypothesis that pre-adaptation to human settlements aid biological invasions of otherwise unsuitable bioregions in South Africa. As many additional species are pre-adapted to transformed biotopes in subtropical areas, one would expect that additional species will colonise the southwestern Cape in the future with unknown economic, ecological and evolutionary consequences.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The negative effects of alien invasive plants on habitats have been well-documented. However, the exchange of organisms between these and native taxa has been far less researched. Here we assess the ...exchanges of arthropod associates of a native (Virgilia divaricata) and an invasive (Acacia mearnsii) legume tree within the ecotone between forest and fynbos vegetation within the Cape Floristic Region of South Africa. Arthropod species richness, abundance, species assemblage composition and measures of beta-diversity were assessed between these two legume species where they grow sympatrically. Except for spiders and ants, arthropod species richness did not differ significantly between the two tree taxa. The overall abundance of arthropods was, however, significantly higher on the native tree species. This pattern was strongly driven by herbivores, as is consistent with predictions of the Enemy Release Hypothesis. When excluding rare taxa, over 75 % of all arthropod species collected in this study were associated with both host trees. However, arthropod community composition differed significantly between the two host plant taxa, largely due to differences between their herbivore communities. Arthropod beta diversity was high on the native host, with arthropod communities on the invasive host being much more homogenous across the sampling range. These results indicate that there are numerous exchanges of arthropods between these native and invasive plants. The invasive plant may provide arthropods with a pathway to other habitats between previously isolated native populations. This will have significant implications for biodiversity conservation at the habitat, species and population level.
Numerous dead and dying individuals of the Western Cape endemic tree Virgilia oroboides (Fabaceae) were recently observed within a South African national botanical garden. Root‐rot fungi and fungi ...symbiotic with bark beetles (Curculionidae; Scolytinae) from diseased trees were assessed for their respective roles in V. oroboides mortality. Disease progression was also monitored over 1 year. Fungi were isolated from surface sterilized bark and root samples from diseased trees and provisionally identified using data from the internal transcribed spacer regions (ITS1, ITS2), including the 5·8S rRNA gene (ITS). Pathogenicity of selected fungi towards V. oroboides was tested under field conditions. The pathogenicity of various bark beetle‐associated Geosmithia (Hypocreales: Hypocreomycetidae) spp. from V. oroboides were similarly assessed. The only fungus consistently isolated from lesions on the roots and bark of declining V. oroboides, and never from healthy individuals, represented an undescribed Diaporthe (Diaporthales, Diaporthaceae) species that was characterized using molecular (using data from the ITS marker and part of the β‐tubulin gene, TUB), cultural and morphological characters. It is an aggressive pathogen of V. oroboides, newly described here as Diaporthe virgiliae sp. nov. Trees of all ages are susceptible to this pathogen with subsequent bark beetle attack of mature trees only. All Geosmithia spp. from beetles and/or infected trees were nonpathogenic towards V. oroboides. Diaporthe virgiliae caused a severe decline in the health of the monitored V. oroboides population over a period of only 1 year and should be considered as a significant threat to these trees.
Small islands are particularly vulnerable to degradation by invasive species and often lack source populations to replace those lost during localized extinctions. Robben Island, a significant South ...African cultural heritage site, has a long history of anthropogenic impact. Introduced alien mammals and trees have resulted in numerous localized plant extinctions with their impact on arthropod biodiversity remaining unclear. We used Robben Island’s arthropod fauna as focal group to investigate the rehabilitation potential of this transformed island. Ground surface-living, foliage-inhabiting and flower-visiting arthropods were collected using five sampling techniques. Arthropod diversity was highest in the two ‘natural’ habitats compared to alien
Eucalyptus
plantations. Arthropod compositional diversity differed significantly between alien plantations and natural habitats. Nevertheless, a remarkable 17 % of all species were confined to plantations. However, when we corrected for the effect of rarity, only 15 species (4 %) were unique to alien plantations and all those identified to species level were either alien in origin or were widespread generalists only normally associated with transformed areas. This emphasizes the need to identify species that drive similarity indices to fully comprehend the conservation value of alien vegetation. Arthropods found in the remaining natural vegetation showed remarkable tolerance of long-term grazing pressures from introduced alien mammals. Only eight Orthoptera species were sampled, yet one was a rediscovery of a rare species and another a range extension. All indigenous species showed strong preferences for natural habitats. Thus, Robben Island could still hold conservation value if the natural habitats are rehabilitated and the
Eucalyptus
plantations removed.
A new Oxalis (Oxalidaceae) species from the Hantamsberg (South Africa) is described and typified as Oxalis noctiflora using morphological, palynological, and molecular characters. Superficially it ...closely resembles Oxalis aridicola, Oxalis callosa, Oxalis odorata, and Oxalis primuloides, and it shares a unique supra-areolate pollen type with most of these species. No single vegetative morphological character defines this species, but a unique combination of bulb and leaflet characters distinguishes it from all other known species. The flowers of Oxalis noctiflora are unique for the genus in displaying typical moth-pollination characters. The white flowers open at night, have a long, unusually narrow, corolla tube, and produce a strong sweet scent. All previously described Oxalis species have flowers that open during the day. Phylogenetic analyses based on nuclear Internal Transcribed Spacer data placed this species sister to O. aridicola within a clade of morphologically and palynologically similar taxa.
The aquatic lineage consisting of the sister taxa
Oxalis dines
and
O. disticha
is confined to a few small vernal pools in the semi-arid Greater Cape Floristic Region of South Africa. All known ...populations are at risk of extinction due to anthropogenically induced disturbance. To identify priority sites for focused conservation management, the chloroplast intergenic spacer regions
psb
A-
trn
H and
trn
S-
trn
G were used to determine population structure and genetic diversity in this lineage across its distribution range. Population viability was assessed using flower morph ratios as surrogate for sexual health. Fourteen and four haplotypes were identified from
O. disticha
and
O. dines
populations, respectively. Analyses of Molecular Variance indicated an extremely high level of interpopulation differentiation across the entire aquatic lineage as well as within
O. disticha
and
O. dines
. Fifty percent of the eighteen haplotypes were confined to single pools, and 84% of populations contained only a single haplotype, even though pool interspacing distance for
O. disticha
was often less than 5 km. Almost half of
O. disticha
haplotype diversity was restricted to very small populations. Two
O. dines
haplotypes were restricted to small populations, with one of these presenting a divergent haplotype sister to the remainder of the aquatic lineage. Flower morph frequency ratio analyses suggested that most populations were reproductively healthy. Low haplotypic diversity within local populations and differentiation between populations are consistent with very low seed-level gene flow and sporadic founder effects. Conservation efforts should be focussed on preserving as many pools as possible with small, genetically distinct populations representing a main concern.
The Cape Floristic Region (CFR) displays high levels of plant diversity and endemism, and has received focused botanical systematic attention. In contrast, fungal diversity patterns and ...co-evolutionary processes in this region have barely been investigated. Here we reconstruct molecular phylogenies using the ITS and β-tubulin gene regions of the ophiostomatoid fungi
Gondwanamyces and
Ophiostoma associated with southern African
Protea species. Results indicate that they evolved in close association with
Protea. In contrast to
Protea,
Ophiostoma species migrated to the CFR from tropical and subtropical Africa, where they underwent subsequent radiation. In both
Gondwanamyces and
Ophiostoma vector arthropods probably facilitated long-distance migration and shorter-distance dispersal. Although ecological parameters shaped most associations between ophiostomatoid fungi and
Protea, there is congruence between fungal–host-associations and the systematic classification of
Protea. These results confirm that the entire biotic environment must be considered in order to understand diversity and evolution in the CFR as a whole.
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