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This issue of Mycological Research News features: Cause of the Irish potato famine finally identified; A lichen theme; Other papers in this issue; and Pathogen introduction as a collateral effect of military activity.
The fast-tracked lead paper in this part reports the identity of the Phytophthora infestans halpotype responsible for the Irish potato famine in the 1840s.
Seven papers are collected together to make this a Lichen Theme issue. These address mating systems in Xanthoria; secondary compound production in culture in Ramalina spp.; the molecular phylogeny of Physconia spp. and the Lecanora rupicola group; molecular, morphological and ecological variation and systematics in marine Collemopsidium spp.; a revision of non-yellow Rhizocarpon spp. in Nordic countries; and new corticolous Trichothelium spp.
Other papers show that the generic name Verticillium has been misapplied and take action to maintain its current use; examine the survival of chytrid spores in stressful soils; and compare the seasonality of a Laboulbenia and its beetle host.
The following new scientific names are introduced in this part: Trichothelium angustisporum, T. caudatum, and T. kalbii spp. nov.; Acrostalagmus luteo-albus (syn. Sporotrichum luteo-album), Collemopsidium foveolatum (syn. Arthopyrenia foveolata), and C. ostrearum (syn. Lecanactis ostrearum) combs. nov.; and Lecanora rouxii (syn. Lepraria flavescens) nom. nov.
The mtDNA haplotypes of the plant pathogen Phytophthora infestans present in dried potato and tomato leaves from herbarium specimens collected during the Irish potato famine and later in the 19th and early 20th century were identified. A 100 bp fragment of ribosomal DNA (rDNA) specific for P. infestans was amplified from 90% of the specimens (n=186), confirming infection by P. infestans. Primers were designed that distinguish the extant mtDNA haplotypes. 86% percent of the herbarium specimens from historic epidemics were infected with the Ia mtDNA haplotype. Two mid-20th century potato leaves from Ecuador (1967) and Bolivia (1944) were infected with the Ib mtDNA haplotype of the pathogen. Both the Ia and IIb haplotypes were found in specimens collected in Nicaragua in the 1950s. The data suggest that the Ia haplotype of P. infestans was responsible for the historic epidemics during the 19th century in the UK, Europe, and the USA. The Ib mtDNA haplotype of the pathogen was dispersed later in the early 20th century from Bolivia and Ecuador. Multiple haplotypes were present outside Mexico in the 1940s–60s, indicating that pathogen diversity was greater than previously believed.
Genetic variability among sterile cultured single ascospore isolates of Xanthoria parietina, X. calcicola, X. ectaneoides, X. capensis, X. polycarpa and X. resendei was investigated with RAPD-PCR. If available five out of eight ascospores per ascus were analysed. In some samples multispore and mycelial isolates from ascomata were included in the analysis. Ascospore germination rates and phenotypic features such as growth rate, pigmentation and secondary metabolites were uniform in X. parietina sporelings of the same ascus, but varied among the progeny of meiosis in all other species. Phenotypic features correlated with genetic variability. X. parietina revealed polymorphisms among specimens from different worldwide locations. In contrast nine out of ten sets of sibling spores were genetically uniform, with only 2% polymorphism in the remaining set, indicating that X. parietina might be homothallic. X. calcicola, X. ectaneoides, X. capensis, X. polycarpa and X. resendei revealed 9–66% polymorphic loci and therefore are considered heterothallic.
Mycobiont isolation experiments were performed on six species of Ramalina from Brazil: R. celastri, R. complanata, R. dendriscoides, R. gracilis, R. peruviana and R. sprengelii. This study aimed to optimize the culture conditions and nutrient requirements of the selected mycobionts. The aposymbiotic R. complanta was successfully isolated from ascospores, while aposymbiotic R. peruviana was obtained from thallus fragments. In R. peruviana the production of secondary metabolites was investigated under aposymbiotical growth conditions using HPLC. When cultivated on solid medium, this mycobiont produced the typical chemosyndrome (sekikaic acid and satellite compounds), found in the voucher lichen thallus. When cultivated in liquid medium (immersed in malt yeast medium in the absence of agar), only one, the major lichen substance, sekikaic acid, was synthesized by the fungus. In addition, atranorin was formed, but was not detected in any of the voucher specimens. Red pigments were found in solid and liquid cultures. These were separated into two compounds, but could not be fully identified. R. celastri spores germinated, but did not form mycelia. R. dendriscoides, R. gracilis and R. sprengelii were not successfully cultivated in aposymbiotic conditions, although eight different culture media were tested.
A Bayesian analysis of nuclear ribosomal DNA internal transcribed spacer (ITS) sequences was used to infer phylogenetic relationships of 14 Physconia species. The analysis supports the monophyly of the genus. Three well supported clades can be distinguished within Physconia: the series griseae, venustae and pulverulentae. The relationships of these clades, however, is not resolved with confidence. Cortical characters are re-evaluated on the basis of the phylogenetic hypothesis. Anatomical features of the upper cortex are only diagnostic above the species level for two special forms of two-layered cortices, while morphological characters, such as lower surface and rhizine-type are characteristic for distinct clades. P. venusta and P. perisidiosa are not separated in this analysis, but populations of P. muscigena, and European and North American samples of P. americana are clearly distinct and the monophyly of both P. americana and P. muscigena s. lat. is rejected on the basis of a Bayesian hypothesis testing.
A molecular phylogeny of the Lecanora rupicola group is presented, based on ITS sequence analyses. The study includes saxicolous and corticolous members of the Lecanora rupicola group as well as other Lecanora species with pruinose apothecia. A phylogenetic hypothesis for species in Lecanora s. lat. and various other genera in Lecanoraceae, based on an alignment-free distance estimation technique, shows that the Lecanora rupicola group forms a monophyletic clade within Lecanoraceae. Affinities to the core group of Lecanora are not well supported, likewise the monophyly of Lecanora s. str. with other species groups in Lecanora, such as the lobate taxa (and Rhizoplaca) is not supported. A more detailed analysis involving Lecanora species with pruinose apothecial discs was carried out with model-based Bayesian Markov chain Monte Carlo (B/MCMC) tree sampling. The results suggest the monophyly of the Lecanora species that are characterized by the presence of chromones. Corticolous as well as saxicolous species are included. Lepraria flavescens is closely related to the Lecanora swartzii subgroup, and the new name Lecanora rouxii nom. nov. is introduced for that species. Other Lecanora species with pruinose discs are not closely related to the Lecanora rupicola group.
The taxonomy of the marine species of Collemopsidium in northwest Europe was investigated using morphological and molecular evidence. 210 specimens were collected from the west coasts of Norway and Ireland, and morphological and ecological variables recorded. ITS1 rDNA sequences were obtained from 24 specimens. A phylogenetic analysis, resulting in a single optimal tree, was performed under the unweighted least squares optimality criterion based on maximum likelihood distances obtained from unaligned sequences. Principal components analysis (PCA) was performed on morphological variables of the sequenced specimens, and classification was carried out by maximizing agreement between the phylogenetic tree and the PCA. Thallus immersion, and perithecial immersion and size, were the most important characters for discriminating between taxa. Apart from substratum, niche separation between taxa was small but statistically significant as shown by a redundancy analysis (RDA). Variance partitioning indicated that genetic variation is vastly more important than ecology for explaining phenotypic variation. Five species of marine Collemopsidium are recognized, including two new combinations: C. foveolatum (syn. Arthopyrenia foveolata) and C. ostrearum (syn. Lecanactis ostrearum) combs. nov.
The taxonomy of the non-yellow species of the genus Rhizocarpon (Rhizocarpaceae, lichenized Ascomycota) occurring in the Nordic countries, with hyaline and muriform ascospores, has been revised. Rhizocarpon amphibium, R. anaperum, R. distinctum, R. furfurosum, R. lavatum, R. petraeum, R. postumum, R. reductum, R. roridulum, R. rubescens, R. subgeminatum, R. sublavatum (reported from the study area for the first time), R. subpostumum, R. suomiense, R. timdalii, and R. umbilicatum are recognized. Their morphology, anatomy, secondary chemistry, ecology, and distribution in the Nordic countries are investigated and discussed. Distribution maps and a key to the species are provided. The most important characters for separating the treated species are pruinose/epruinose thallus, number of ascospores in asci, ascospore size and number of cells per ascospore in optical view, insoluble lichen pigments of the epihymenium and the proper excipulum, and lichen substances. Seven names are lectotypified and two are neotypified.
A survey of corticolous crustose lichen collections in connection with the Flora Neotropica project revealed a number of undescribed species of Trichothelium. While a few typically foliicolous taxa may occasionally be found on bark, five species seem to be exclusively corticolous, all with a Trentepohlia photobiont. Three of them are new species: T. angustisporum, T. caudatum, and T. kalbii spp. nov. A key is provided to all five corticolous species, accompanied by data on their distribution and ecology. A considerable range extension is reported for T. horridulum, with new collections from Costa Rica and north-eastern Brazil.
The monotype species of the genus Verticillium, Verticillium tenerum, is a synonym of the older name Sporotrichum luteo-album. Its purported teleomorph connection with ‘Nectria’ inventa is refuted and the preserved specimens of that species are considered as probably identical with Stephanonectria keithii (Bionectriaceae). V. luteo-album takes a unique position in the Glomerella clade of ascomycetes, as sister of the Verticillium–Plectosphaerella clade, which comprises plant-pathogenic species. V. luteo-album is not closely related to V. dahliae and its relatives, which are also situated in this clade. Conservation of the name Verticillium with V. dahliae as conserved type will be necessary to retain this generic name for the plant-pathogenic Verticillium species. In anticipation of this conservation, the new combination Acrostalagmus luteo-albus (syn. Sporotrichum luteo-album) is made.
Rhizophlyctis rosea was found in 44% of 59 soil samples from national parks, urban reserves and gardens, and agricultural lands of eastern New South Wales, Australia. As some of the soils are periodically dry and hot, we examined possible mechanisms that enable survival in stressful environments such as agricultural lands. Air-dried thalli of R. rosea in soil and pure cultures of R. rosea, two isolates of Allomyces anomalus, one isolate of Catenaria sp., one of Catenophlyctis sp. and one of Spizellomyces sp. recovered following incubation at 90 °C for two days. Powellomyces sp. recovered following incubation at 80 °. Sporangia of all seven fungi shrank during air-drying, and immediately returned to turgidity when rehydrated. Some sporangia of R. rosea released zoospores immediately upon rehydration. These data indicate that some Chytridiomycota have resistant structures that enable survival through periodic drying and high summer temperatures typical of soils used for cropping. Eleven Chytridiomycota isolated from soil did not survive either drying or heat. Neither habitat of the fungus nor morphological type correlated with the capacity to tolerate drying and heat.
Terrestrial invertebrates in central Amazonian floodplains must cope with annual long-term inundation. Parasites should be affected mainly indirectly through the specific life-cycles of their hosts. We studied the temporal structure of a beetle–fungus system at a central Amazonian blackwater floodplain (Rio Negro, Brazil). The host species Phaeoxantha aequinoctialis (Coleoptera, Carabidae, Cicindelinae) showed a seasonal, univoltine life-cycle triggered by the annual flood pulse. Infestation frequency of its fungal parasite, Laboulbenia phaeoxanthae (Ascomycota, Laboulbeniales), varied seasonally. However, the seasonality was opposed in host and parasite: the lowest infestation frequencies were observed during periods of highest beetle abundance and vice versa. Periods of lowest beetle abundance coincided with the end of the old generation, those with highest abundance with the appearance of new adults. The resulting annual patterns of a slow spread in the host population resembled the few records of temporal patterns from temperate regions. It is explicitly demonstrated that older adult female beetles are more frequently infested than younger ones. Future studies may reveal whether this is simply the result of specific host life-cycles (driven by a flood pulse, winter, or other factors), or might also be related to potentially easier infestation in older individuals.