Species delimitation and phylogeography of the Pectenia species-complex: A misunderstood case of species-pairs in lichenized fungi, where reproduction mode does not delimit lineages

Notulae to the Italian flora of algae, bryophytes, fungi and lichens: 12

In this contribution, new data concerning bryophytes, fungi and lichens of the Italian flora are presented. It includes new records, confirmations or exclusions for the bryophyte genera Acaulon, Campylopus, Entosthodon, Homomallium, Pseudohygrohypnum, and Thuidium, the fungal genera Entoloma, Cortinarius, Mycenella, Oxyporus, and Psathyrella and the lichen genera Anaptychia, Athallia, Baeomyces, Bagliettoa, Calicium, Nephroma, Pectenia, Phaeophyscia, Polyblastia, Protoparmeliopsis, Pyrenula, Ramalina, and Sanguineodiscus.

A case study on the re-establishment of the cyanolichen symbiosis: where do the compatible photobionts come from?

BACKGROUND AND AIMS

In order to re-establish lichen symbiosis, fungal spores must first germinate and then associate with a compatible photobiont. To detect possible establishment limitations in a sexually reproducing cyanolichen species, we studied ascospore germination, photobiont growth and photobiont association patterns in Pectenia plumbea.

METHODS

Germination tests were made with ascospores from 500 apothecia under different treatments, and photobiont growth was analysed in 192 isolates obtained from 24 thalli. We determined the genotype identity [tRNALeu (UAA) intron] of the Nostoc cyanobionts from 30 P. plumbea thalli from one population. We also sequenced cyanobionts of 41 specimens of other cyanolichen species and 58 Nostoc free-living colonies cultured from the bark substrate.

KEY RESULTS

Not a single fungal ascospore germinated and none of the photobiont isolates produced motile hormogonia. Genetic analyses revealed that P. plumbea shares Nostoc genotypes with two other cyanolichen species of the same habitat, but these photobionts were hardly present in the bark substrate.

CONCLUSIONS

Due to the inability of both symbionts to thrive independently, the establishment of P. plumbea seems to depend on Dendriscocaulon umhausense, the only cyanolichen species in the same habitat that reproduces asexually and acts as a source of appropriate cyanobionts. This provides support to the hypothesis about facilitation among lichens.

Discovering cryptic species in the Aspiciliella intermutans complex (Megasporaceae, Ascomycota) - First results using gene concatenation and coalescent-based species tree approaches

Taxonomic identifications in some groups of lichen-forming fungi have been challenge largely due to the scarcity of taxonomically relevant features and limitations of morphological and chemical characters traditionally used to distinguish closely related taxa. Delineating species boundaries in closely related species or species complexes often requires a range of multisource data sets and comprehensive analytical methods. Here we aim to examine species boundaries in a group of saxicolous lichen forming fungi, the Aspiciliella intermutans complex (Megasporaceae), widespread mainly in the Mediterranean. We gathered DNA sequences of the nuclear ribosomal internal transcribed spacer (nuITS), the nuclear large subunit (nuLSU), the mitochondrial small subunit (mtSSU) ribosomal DNA, and the DNA replication licensing factor MCM7 from 80 samples mostly from Iran, Caucasia, Greece and eastern Europe. We used a combination of phylogenetic strategies and a variety of empirical, sequence-based species delimitation approaches to infer species boundaries in this group. The latter included: the automatic barcode gap discovery (ABGD), the multispecies coalescent approach *BEAST and Bayesian Phylogenetics and Phylogeography (BPP) program. Different species delimitation scenarios were compared using Bayes factors species delimitation analysis. Furthermore, morphological, chemical, ecological and geographical features of the sampled specimens were examined. Our study uncovered cryptic species diversity in A. intermutans and showed that morphology-based taxonomy may be unreliable, underestimating species diversity in this group of lichens. We identified a total of six species-level lineages in the A. intermutans complex using inferences from multiple empirical operational criteria. We found little corroboration between morphological and ecological features with our proposed candidate species, while secondary metabolite data do not corroborate tree topology. The present study on the A. intermutans species-complex indicates that the genus Aspiciliella, as currently circumscribed, is more diverse in Eurasia than previously expected.

Cryptic diversity, pathogenicity, and evolutionary species boundaries in Cercospora populations associated with Cercospora leaf spot of Beta vulgaris

The taxonomy and evolutionary species boundaries in a global collection of Cercospora isolates from Beta vulgaris was investigated based on sequences of six loci. Species boundaries were assessed using concatenated multi-locus phylogenies, Generalized Mixed Yule Coalescent (GMYC), Poisson Tree Processes (PTP), and Bayes factor delimitation (BFD) framework. Cercospora beticola was confirmed as the primary cause of Cercospora leaf spot (CLS) on B. vulgaris. Cercospora apii, C. cf. flagellaris, Cercospora sp. G, and C. zebrina were also identified in association with CLS on B. vulgaris. Cercospora apii and C. cf. flagellaris were pathogenic to table beet but Cercospora sp. G and C. zebrina did not cause disease. Genealogical concordance phylogenetic species recognition, GMYC and PTP methods failed to differentiate C. apii and C. beticola as separate species. On the other hand, multi-species coalescent analysis based on BFD supported separation of C. apii and C. beticola into distinct species; and provided evidence of evolutionary independent lineages within C. beticola. Extensive intra- and intergenic recombination, incomplete lineage sorting and dominance of clonal reproduction complicate evolutionary species recognition in the genus Cercospora. The results warrant morphological and phylogenetic studies to disentangle cryptic speciation within C. beticola.