Martin Westberg

Species delimitation and evolution of metal bioaccumulation in the lichenized Acarospora smaragdula (Ascomycota, Fungi) complex

The crustose lichenized fungi in the Acarosporaceae are splendid examples of organisms managing to survive in extremely harsh environments, such as highly mineralized rocks and low‐pH habitats. Some representatives of the Acarospora smaragdula complex are known to accumulate substantial amounts of potentially toxic metals including iron and copper, resulting in populations with highly divergent coloration and morphology. These populations have often been treated as distinct species by lichen taxonomists. Parsimony and parsimony jackknifing analyses of β‐tubulin, nuclear ITS rDNA, and mtSSU rDNA sequence data sets was used to investigate the evolution of iron and copper accumulation and the production of the secondary compound norstictic acid in populations within the A. smaragdula species complex in Sweden, with additional samples mainly from Norway and the UK. Phylogenetic species recognition (concordance of single‐gene phylogenies) was used to investigate species delimitations. Seven species are recognized in the complex. Atypically green, copper‐accumulating samples, often given species rank, do not form a distinct group but are nested within A. smaragdula s. str., indicating that this ability is widespread in this species. Rust‐coloured, iron‐accumulating samples form two well supported separate groups, indicating that two morphologically distinct, obligate, iron‐accumulating species are present, but facultatively iron‐accumulating populations occur in at least one additional species. Norstictic acid, sometimes claimed to characterize the whole A. smaragdula complex, is only present in A. smaragdula s. str. The evolutionary significance of metal accumulation in Acarospora is discussed, as is the significance of our results for the application of phylogenetic species recognition/gene tree concordance‐based species recognition, and DNA barcoding. 
© The Willi Hennig Society 2009.

Host switching promotes diversity in host-specialized mycoparasitic fungi: uncoupled evolution in the Biatoropsis - Usnea system

Fungal mycoparasitism—fungi parasitizing other fungi—is a common lifestyle in some basal lineages of the basidiomycetes, particularly within the Tremellales. Relatively nonaggressive mycoparasitic fungi of this group are in general highly host specific, suggesting cospeciation as a plausible speciation mode in these associations. Species delimitation in the Tremellales is often challenging because morphological characters are scant. Host specificity is therefore a great aid to discriminate between species but appropriate species delimitation methods that account for actual diversity are needed to identify both specialist and generalist taxa and avoid inflating or underestimating diversity. We use the Biatoropsis‐Usnea system to study factors inducing parasite diversification. We employ morphological, ecological, and molecular data—methods including genealogical concordance phylogenetic species recognition (GCPSR) and the general mixed Yule‐coalescent (GMYC) model—to assess the diversity of fungi currently assigned to Biatoropsis usnearum. The degree of cospeciation in this association is assessed with two cophylogeny analysis tools (ParaFit and Jane 4.0). Biatoropsis constitutes a species complex formed by at least seven different independent lineages and host switching is a prominent force driving speciation, particularly in host specialists. Combining ITS and nLSU is recommended as barcode system in tremellalean fungi.

Diagnostics for a troubled backbone: testing topological hypotheses of trapelioid lichenized fungi in a large-scale phylogeny of Ostropomycetidae (Lecanoromycetes)

Trapelioid fungi constitute a widespread group of mostly crust-forming lichen mycobionts that are key to understanding the early evolutionary splits in the Ostropomycetidae, the second-most species-rich subclass of lichenized Ascomycota. The uncertain phylogenetic resolution of the approximately 170 species referred to this group contributes to a poorly resolved backbone for the entire subclass. Based on a data set including 657 newly generated sequences from four ribosomal and four protein-coding gene loci, we tested a series of a priori and new evolutionary hypotheses regarding the relationships of trapelioid clades within Ostropomycetidae. We found strong support for a monophyletic group of nine core trapelioid genera but no statistical support to reject the long-standing hypothesis that trapelioid genera are sister to Baeomycetaceae or Hymeneliaceae. However, we can reject a sister group relationship to Ostropales with high confidence. Our data also shed light on several long-standing questions, recovering Anamylopsoraceae nested within Baeomycetaceae, elucidating two major monophyletic groups within trapelioids (recognized here as Trapeliaceae and Xylographaceae), and rejecting the monophyly of the genus Rimularia. We transfer eleven species of the latter genus to Lambiella and describe the genus Parainoa to accommodate a previously misunderstood species of Trapeliopsis. Past phylogenetic studies in Ostropomycetidae have invoked “divergence order” for drawing taxonomic conclusions on higher level taxa. Our data show that if backbone support is lacking, contrasting solutions may be recovered with different or added data. We accordingly urge caution in concluding evolutionary relationships from unresolved phylogenies.

Candelariella (Candelariaceae) in western United States and northern Mexico: the 8-spored, lecanorine species

Abstract This paper treats 12 Candelariella species occurring in western North America characterized by having lecanorine apothecia and 8-spored asci. Six new names are proposed: C. aggregata, C. californica, C. complanata, C. corallizoides, C. deppeanae and C. immarginata. Candelariella terrigena and C. deflexa are treated as synonyms of C. citrina and C. aurella, respectively. Candelariella kansuensis is newly reported from North America. Distribution maps for western North America are presented for all species. Candelariella citrina, C. rosulans and C. terrigena are lectotypified. A key to Candelariella in western North America is presented.

Silobia , a new genus for the Acarospora smaragdula complex (Ascomycota, Acarosporales ) and a revision of the group in Sweden

The new genus Silobia M. Westb. & Wedin is proposed for the Acarospora smaragdula group, which is taxonomically and nomenclaturally revised in Sweden. The proposed taxonomy results from our former molecular phylogeny, together with morphological and anatomical investigations and analysis of secondary metabolites. Seven species are recognized in Sweden in this paper: Silobia dilatata sp. nov., S. myochroa sp. nov., S. rhagadiza comb. nov., S. rufescens comb. nov., S. scabrida comb. nov., S. smaragdula comb. nov. and S. tangerina sp. nov. Acarospora alberti, A. amphibola, A. isortoquensis, A. murina and A. undata are recognized as synonyms of S. smaragdula, Acarospora verruciformis as a synonym of S. scabrida and A. scyphulifera as a synonym of S. rhagadiza. The following names are lectotypified: Acarospora amphibola, A. amphibola f. testacea, A. lesdainii, A. lesdainii var. subochracea, A. murina, A. scyphulifera f. subdiscreta, Endocarpon smaragdulum, Lecanora rhagadiza and Sagedia rufescens. Acarospora scyphulifera is neotypified. Acarospora fusca is excluded from the Swedish checklist as the specimen was found to belong to S. rufescens. A key to the species is presented.

Candelariella (Candelariaceae) in western United States and northern Mexico: the polysporous species

Abstract Six species of Candelariella with polysporous asci are recognized from western North America. The species are: C. borealis sp. nov., C. efflorescens, C. lutella, C. placodizans, C. vitellina and C. xanthostigma. Candelariella vitellina is lectotypified. A key to the polysporous species in western North America is provided and their distribution in the study area is mapped.

Candelariella (Candelariaceae) in western United States and northern Mexico : the species with biatorine apothecia

Abstract Three species of Candelariella in western North America, characterized by biatorine apothecia, are treated. Two new species are described, C. biatorina and C. lichenicola. Candelariella biatorina is a corticolous species growing in montane conifer forests in western North America. Candelariella lichenicola, described from northwestern Mexico, is a lichenicolous fungus that lacks an independent thallus and the apothecia develop on the thallus of Candelina submexicana. The third species, C. subdeflexa, is a rare species on bark in Arizona, Colorado and Utah in western North America. Macroconidia are described in the Candelariaceae for the first time in C. biatorina. In C. subdeflexa conidia are borne externally on the lower side of the thallus squamules. The distribution of the three species in western North America is mapped.

Microbiome change by symbiotic invasion in lichens

Lichens are obligate symbioses between fungi and green algae or cyanobacteria. Most lichens resynthesize their symbiotic thalli from propagules, but some develop within the structures of already existing lichen symbioses. Diploschistes muscorum starts as a parasite infecting the lichen Cladonia symphycarpa and gradually develops an independent Diploschistes lichen thallus. Here we studied how this process influences lichen-associated microbiomes and photobionts by sampling four transitional stages, at sites in Sweden and Germany, and characterizing their microbial communities using high-throughput 16S rRNA gene and photobiont-specific ITS rDNA sequencing, and fluorescence in situ hybridization. A gradual microbiome shift occurred during the transition, but fractions of Cladonia-associated bacteria were retained during the process of symbiotic reorganization. Consistent changes observed across sites included a notable decrease in the relative abundance of Alphaproteobacteria with a concomitant increase in Betaproteobacteria. Armatimonadia, Spartobacteria and Acidobacteria also decreased during the infection of Cladonia by Diploschistes. The lichens differed in photobiont specificity. Cladonia symphycarpa was associated with the same algal species at all sites, but Diploschistes muscorum had a flexible strategy with different photobiont combinations at each site. This symbiotic invasion system suggests that partners can be reorganized and selected for maintaining potential roles rather than depending on particular species.

Evidence of weak habitat specialisation in microscopic animals.

Macroecology and biogeography of microscopic organisms (any living organism smaller than 2 mm) are quickly developing into fruitful research areas. Microscopic organisms also offer the potential for testing predictions and models derived from observations on larger organisms due to the feasibility of performing lab and mesocosm experiments. However, more empirical knowledge on the similarities and differences between micro- and macro-organisms is needed to ascertain how much of the results obtained from the former can be generalised to the latter. One potential misconception, based mostly on anedoctal evidence rather than explicit tests, is that microscopic organisms may have wider ecological tolerance and a lower degree of habitat specialisation than large organisms. Here we explicitly test this hypothesis within the framework of metacommunity theory, by studying host specificify in the assemblages of bdelloid rotifers (animals about 350 µm in body length) living in different species of lichens in Sweden. Using several regression-based and ANOVA analyses and controlling for both spatial structure and the kind of substrate the lichen grow over (bark vs rock), we found evidence of significant but weak species-specific associations between bdelloids and lichens, a wide overlap in species composition between lichens, and wide ecological tolerance for most bdelloid species. This confirms that microscopic organisms such as bdelloids have a lower degree of habitat specialisation than larger organisms, although this happens in a complex scenario of ecological processes, where source-sink dynamics and geographic distances seem to have no effect on species composition at the analysed scale.

Phylogeny of the Acarosporaceae (Lecanoromycetes, Ascomycota, Fungi) and the evolution of carbonized ascomata

The phylogeny of the Acarosporaceae (Lecanoromycetes, Acarosporomycetidae, Acarosporales) is investigated using data from three molecular markers; nuclear ITS-LSU rDNA, mitochondrial SSU and β-tubulin. Acarosporaceae is shown to be constituted by six main clades; Myriospora, Timdalia, Pleopsidium, a clade composed by “Acarospora” rhizobola and “A.” terricola, the poorly supported Sarcogyne clade (including several Polysporina and Acarospora species) and the Acarospora clade (including the type of Polysporina, P. simplex, and several other Polysporina species). The common ancestor of the Acarosporaceae did not produce strongly black pigmented (carbonized or melanized) ascomata, but this trait has arisen secondarily and independently numerous times in the evolution of the group. The number of changes in character states of both carbonized epihymenium and carbonized exciple are considerably more than the minimum number. The genera Sarcogyne and Polysporina—largely circumscribed based on the presence of black pigmented ascomata—are shown to be distinctly non-monophyletic. The presence of green algae in the ascoma margin (lecanorine or lecideine ascomata) may vary even within single species.