Nicolas Magain

Microsatellite primers in the Peltigera dolichorhiza complex (lichenized ascomycete, Peltigerales)

UNLABELLED PREMISE OF THE STUDY Microsatellite primers were developed for the lichen-forming fungus Peltigera dolichorhiza to investigate partitioning of genetic variation in a widespread, morphologically and chemically variable taxon likely to represent a complex of cryptic lineages, including P. neopolydactyla. • METHODS AND RESULTS Using next generation shotgun sequence reads, 331 primer pairs were designed to amplify microsatellite sequences from an African accession of P. dolichorhiza. Eleven primer pairs representing the longest repeat units identified were tested on 15 P. dolichorhiza accessions from Africa (incl. Réunion), South America, Papua New Guinea, and on two accessions of P. neopolydactyla from North America. The primers amplified di-, tri, tetra-, and pentanucelotide repeats with 3-8 alleles per locus. All individuals represent distinct multiloci genotypes. • CONCLUSIONS These results indicate the utility of the new microsatellite primers for testing genetic differentiation within the widespread complex of P. dolichorhiza.

Do photobiont switch and cephalodia emancipation act as evolutionary drivers in the lichen symbiosis? A case study in the Pannariaceae (Peltigerales).

Lichen symbioses in the Pannariaceae associate an ascomycete and either cyanobacteria alone (usually Nostoc; bipartite thalli) or green algae and cyanobacteria (cyanobacteria being located in dedicated structures called cephalodia; tripartite thalli) as photosynthetic partners (photobionts). In bipartite thalli, cyanobacteria can either be restricted to a well-delimited layer within the thallus (‘pannarioid’ thalli) or spread over the thallus that becomes gelatinous when wet (‘collematoid’ thalli). We studied the collematoid genera Kroswia and Physma and an undescribed tripartite species along with representatives of the pannarioid genera Fuscopannaria, Pannaria and Parmeliella. Molecular inferences from 4 loci for the fungus and 1 locus for the photobiont and statistical analyses within a phylogenetic framework support the following: (a) several switches from pannarioid to collematoid thalli occured and are correlated with photobiont switches; the collematoid genus Kroswia is nested within the pannarioid genus Fuscopannaria and the collematoid genus Physma is sister to the pannarioid Parmeliella mariana group; (b) Nostoc associated with collematoid thalli in the Pannariaceae are related to that of the Collemataceae (which contains only collematoid thalli), and never associated with pannarioid thalli; Nostoc associated with pannarioid thalli also associate in other families with similar morphology; (c) ancestors of several lineages in the Pannariaceae developed tripartite thalli, bipartite thalli probably resulting from cephalodia emancipation from tripartite thalli which eventually evolved and diverged, as suggested by the same Nostoc present in the collematoid genus Physma and in the cephalodia of a closely related tripartite species; Photobiont switches and cephalodia emancipation followed by divergence are thus suspected to act as evolutionary drivers in the family Pannariaceae.

Discovering the lichen diversity of a remote tropical island: working list of species collected on Reunion (Mascarene archipelago, Indian Ocean)

Abstract: van den Boom, P. P. G., Brand, M., Ertz, D., Kalb, K., Magain, N., Masson, D., Schiefelbein, U., Sipman, H. J. M. & Sérusiaux, E. 2011. Discovering the lichen diversity of a remote tropical island: working list of species collected on Reunion (Mascarene archipelago, Indian Ocean). — Herzogia 24: 325–349. 463 lichen taxa are reported from the island of Reunion (Mascarene archipelago) in the Indian Ocean. This report is based on extensive collections recently made by the authors or hosted in B and LG. A total of c. 600 species is estimated for the number of lichenized fungi present on the island; although this is a low figure for a varied tropical area, this is plausible due to its small size and remoteness. The significance of the lichen diversity of the island lays in its endemics, which need further study for a reliable assessment, and in the occurrence of a poorly known southern hemisphere element (“austral” species). The discovery of the following in Reunion is of special interest as it considerably enlarges their distribution range: Anzia corallophora, Caloplaca caesiosorediata, Coccocarpia delicatula, Fuscopannaria praetermissa, Gomphillus morchelloides, G. pedersenii, Gyalideopsis bispora, Heterodermia koyana, Hypotrachyna evansii, Lithogyalideopsis zeylandica, Lobaria asperula, Megaloblastenia marginiflexa var. dimota, Menegazzia capitata, Myeloconis erumpens and Pannaria squamulosa.

Further photomorphs in the lichen family Lobariaceae from Reunion (Mascarene archipelago) with notes on the phylogeny of Dendriscocaulon cyanomorphs

Abstract Two new photomorphs in the Lobariaceae have been found on the remote island of Reunion in the Mascarene archipelago: the free-living Dendriscocaulon-like cyanomorph of the pantropical Lobaria discolor, and the cyanomorph of Sticta dichotoma, a species apparently endemic to the western parts of the Indian Ocean, known only from its chloromorph. Inferences from three loci demonstrate that the fungus involved in each morph of either pair belongs to the same species. Phylogenetic analyses resolve all genera of the Lobariaceae as polyphyletic, and all Dendriscocaulon-like cyanomorphs within Lobaria, except for D. dendroides, which belongs to Sticta.

Macroevolution of Specificity in Cyanolichens of the Genus Peltigera Section Polydactylon (Lecanoromycetes, Ascomycota).

Abstract Patterns of specificity among symbiotic partners are key to a comprehensive understanding of the evolution of symbiotic systems. Specificity of mutualistic partners, within a widespread monophyletic group for which all species are sampled has rarely been explored. Here, we assess the level of specificity between the cosmopolitan lichen‐forming fungus (mycobiont) from the genus Peltigera, section Polydactylon, and its cyanobacterial partner Nostoc (cyanobiont). The mycobiont and cyanobiont phylogenies are inferred from five nuclear loci and the rbcLX region, respectively. These sequences were obtained from 206 lichen thalli, representing ca. 40 closely related Peltigera species sampled worldwide, doubling the number of known species in this group. We found a broad spectrum of specificity for both partners ranging from strict specialists to generalists. Overall, mycobionts are more specialized than cyanobionts by associating mostly with one or a few Nostoc phylogroups, whereas most cyanobionts associate frequently with several Peltigera species. Specialist mycobionts are older than generalists, supporting the hypothesis that specialization of mycobionts to one or few cyanobionts, is favored through time in geographic areas where species have been established for long periods of time. The relatively recent colonization of a new geographic area (Central and South America) by members of section Polydactylon is associated with a switch to a generalist pattern of association and an increased diversification rate by the fungal partner, suggesting that switches to generalism are rare events that are advantageous in new environments. We detected higher genetic diversity in generalist mycobionts. We also found that Peltigera species specialized on a single Nostoc phylogroup have narrower geographical distributions compared with generalist species.

Dismantling the treasured flagship lichen Sticta fuliginosa (Peltigerales) into four species in Western Europe

In the framework of a worldwide project on the phylogeny of the lichen genus Sticta, dedicated sampling was performed in four regions of Western Europe, roughly along an east–west line between N 48°02′ E 07°01′ and N 52°01′ W 09°30′, ranging from France/Vosges to Ireland/Kerry. Five clearly distinct ITS haplotypes were detected for isidia-producing species where only two were expected. Subtle anatomical and morphological characters, together with a strongly supported 4-loci molecular phylogeny, permit distinguishing, besides the easily recognized S. canariensis and S. limbata: 1) the two well-known S. fuliginosa and S. sylvatica, whose type collections have been carefully reassessed; the former is widespread in both hemispheres, while the latter is correctly identified only from continental Europe and the Andes in Colombia. The barcode ITS of S. fuliginosa differs by a single substitution from S. limbata (with a single exception), and the 4-loci phylogenetic tree does not resolve them as distinct lineages, most probably highlighting a very recent divergence and incomplete lineage sorting. 2) Three species that were formely included in S. fuliginosa: the resurrected S. ciliata Taylor, belonging to a complex group yet to be disentangled and occurring in the Neotropics, Africa, Macaronesia, and Western Europe, and two species described as new to science, S. fuliginoides, found in continental Europe, the Canary Islands, eastern North America, and Colombia, and S. atlantica only known from Ireland and the Azores archipelago. Molecular inferences demonstrate active divergence and dispersion within S. ciliata that may require recognition of further species. Fresh material can be identified with a morphological and anatomical preliminary key provided here. We propose that the taxonomy of all lichen species be urgently reviewed in the light of molecular data in an evolutionary context, particularly those used as bioindicators of environmental change and woodland management.

Lecania falcata, a new species from Spain, the Canary Islands and the Azores, close to Lecania chlorotiza

Lecania chlorotiza and L. falcata, described here as new from Spain/Navarra, the Canary Islands and the Azores, do not belong to Lecania s. str. They belong to a strongly supported clade comprising Bacidia, Bacidina, Scutula and Toninia when examined with maximum parsimony, maxi- mum likelihood and Bayesian inferences using mtSSU, nuLSU and nuITS sequences. This clade represents the Bacidiaceae and is included in the Ramalinaceae s. lat. Most genera included in that family need further work before a new genus can possibly be described for Lecania chlorotiza and L. falcata.

Conserved genomic collinearity as a source of broadly applicable, fast evolving, markers to resolve species complexes: A case study using the lichen-forming genus Peltigera section Polydactylon

Synteny can be maintained for certain genomic regions across broad phylogenetic groups. In these homologous genomic regions, sites that are under relaxed purifying selection, such as intergenic regions, could be used broadly as markers for population genetic and phylogenetic studies on species complexes. To explore the potential of this approach, we found 125 Collinear Orthologous Regions (COR) ranging from 1 to >10kb across nine genomes representing the Lecanoromycetes and Eurotiomycetes (Pezizomycotina, Ascomycota). Twenty-six of these COR were found in all 24 eurotiomycete genomes surveyed for this study. Given the high abundance and availability of fungal genomes we believe this approach could be adopted for other large groups of fungi outside the Pezizomycotina. Asa proof of concept, we selected three Collinear Orthologous Regions (COR1b, COR3, and COR16), based on synteny analyses of several genomes representing three classes of Ascomycota: Eurotiomycetes, Lecanoromycetes, and Lichinomycetes. COR16, for example, was found across these three classes of fungi. Here we compare the resolving power of these three new markers with five loci commonly used in phylogenetic studies of fungi, using section Polydactylon of the cyanolichen-forming genus Peltigera (Lecanoromycetes) - a clade with several challenging species complexes. Sequence data were subjected to three species discovery and two validating methods. COR markers substantially increased phylogenetic resolution and confidence, and highly contributed to species delimitation. The level of phylogenetic signal provided by each of the COR markers was higher than the commonly used fungal barcode ITS. High cryptic diversity was revealed by all methods. As redefined here, most species represent lineages that have relatively narrower, and more homogeneous biogeographical ranges than previously understood. The scabrosoid clade consists of ten species, seven of which are new. For the dolichorhizoid clade, twenty-two new species were discovered for a total of twenty-nine species in this clade.

High diversity, high insular endemism and recent origin in the lichen genus Sticta (lichenized Ascomycota, Peltigerales) in Madagascar and the Mascarenes

Lichen biodiversity and its generative evolutionary processes are practically unknown in the MIOI (Madagascar and Indian Ocean Islands) biodiversity hotspot. We sought to test the hypothesis that lichenized fungi in this region have undergone a rapid radiation, following a single colonization event, giving rise to narrow endemics, as is characteristic of other lineages of plants. We extensively sampled specimens of the lichen genus Sticta in the Mascarene archipelago (mainly Réunion) and in Madagascar, mainly in the northern range (Amber Mt and Marojejy Mt) and produced the fungal ITS barcode sequence for 148 thalli. We further produced a four-loci data matrix for 68 of them, representing the diversity and geographical distribution of ITS haplotypes. We reconstructed the phylogenetic relationships within this group, established species boundaries with morphological context, and estimated the date of the most recent common ancestor. Our inferences resolve a robust clade comprising 31 endemic species of Sticta that arose from the diversification following a single recent (c. 11 Mya) colonization event. All but three species have a very restricted range, endemic to either the Mascarene archipelago or a single massif in Madagascar. The first genus of lichens to be studied with molecular data in this region underwent a recent radiation, exhibits micro-endemism, and thus exemplifies the biodiversity characteristics found in other taxa in Madagascar and the Mascarenes.

Strong specificity and network modularity at a very fine phylogenetic scale in the lichen genus Peltigera

Identifying the drivers and evolutionary consequences of species interactions is a major goal of community ecology. Network-based analyses can provide mathematical tools to detect non-random patterns of interactions, and potentially help predicting the consequences of such patterns on evolutionary dynamics of symbiotic systems. Here, we characterize the structure of a lichen network at a very fine phylogenetic scale, by identifying the photosynthetic partners (i.e., cyanobacteria of the genus Nostoc) of lichenized fungi belonging to a monophyletic section of a single genus (i.e., section Polydactylon of the genus Peltigera), worldwide. Even at such a fine phylogenetic scale, we found that interactions were highly modular and anti-nested, indicating strong preferences in interactions. When considering local Peltigera communities, i.e., datasets at small spatial scales with only a slightly broader phylogenetic range, interactions remained modular but were asymmetric, with generalist Nostoc partners interacting with specialized Peltigera species. This asymmetry was not detected with our global spatial scale dataset. We discuss these results in the light of lichen community assembly, and explore how such interaction patterns may influence coevolution in lichens and the evolutionary stability of the mutualism in general.