Phylogenetic species delimitation in ectomycorrhizal fungi and implications for barcoding: the case of the Tricholoma scalpturatum complex (Basidiomycota).
Population studies have revealed that the fungal ectomycorrhizal morphospecies Tricholoma scalpturatum consists of at least two genetically distinct groups that occur sympatrically in several geographical areas. This discovery prompted us to examine species boundaries and relationships between members formerly assigned to T. scalpturatum and allied taxa using phylogenetic analyses. Sequence data were obtained from three nuclear DNA regions [internal transcribed spacer (ITS), gpd and tef], from 101 carpophores collected over a large geographical range in Western Europe, and some reference sequences from public databases. The ITS was also tested for its applicability as DNA barcode for species delimitation. Four highly supported phylogenetic clades were detected. The two previously detected genetic groups of T. scalpturatum were assigned to the phylospecies Tricholoma argyraceum and T. scalpturatum. The two remaining clades were referred to as Tricholoma cingulatum and Tricholoma inocybeoides. Unexpectedly, T. cingulatum showed an accelerated rate of evolution that we attributed to narrow host specialization. This study also reveals recombinant ITS sequences in T. inocybeoides, suggesting a hybrid origin. The ITS was a useful tool for the determination of species boundaries: the mean value of intraspecific genetic distances in the entire ITS region (including 5.8S rDNA) was <0.2%, whereas interspecific divergence estimates ranged from 1.78% to 4.22%. Apart from giving insights into the evolution of the T. scalpturatum complex, this study contributes to the establishment of a library of taxonomically verified voucher specimens, an a posteriori correlation between phenotype and genotype, and DNA barcoding of ectomycorrhizal fungi.
Université de Toulouse, UPS, UMR5174 EDB (Laboratoire Evolution et Diversité Biologique); 118 route de Narbonne, F-31062 Toulouse, France. jargeat@cict.fr
Patricia
P
Jargeat
Florent
F
Martos
Fabian
F
Carriconde
Hervé
H
Gryta
Pierre-Arthur
PA
Moreau
Monique
M
Gardes
D002467:Cell Nucleus / Q000235:genetics; D058893:DNA Barcoding, Taxonomic; D004271:DNA, Fungal / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D005060:Europe; D014644:Genetic Variation; D006239:Haplotypes; D038821:Mycorrhizae / Q000145:classification / Q000235:genetics; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D055439:Tricholoma / Q000145:classification* / Q000235:genetics
D004271:DNA, Fungal; D021903:DNA, Ribosomal Spacer