RESUMO
Lentinula (Basidiomycota, Agaricales) includes the most widely cultivated mushroom in the world, Lentinula edodes, also known as shiitake (Japanese) or xiang-gu (Chinese). At present, nine species are recognized in the genus, based on morphology, mating criteria, and geographic distribution. However, analyses of internal transcribed spacers (ITS) of ribosomal RNA genes have suggested that there are cryptic lineages. We analyzed a global-scale phylogenetic dataset from 325 Lentinula individuals from 24 countries in Asia-Australasia and the Americas plus Madagascar, with 325 sequences of ITS, 80 LSU sequences, and 111 sequences of translation elongation factor (tef1-α) genes. We recovered 15 independent lineages (Groups 1-15) that may correspond to species. Lineages in Asia-Australasia (Groups 1-5) and the Americas plus Madagascar (Groups 6-15) formed sister clades. Four lineages are represented only by sequences from single individuals and require further molecular sampling, including L. aff. raphanica (Group 7), L. ixodes (Group 8), L. boryana (Group 12), and L. aff. aciculospora (Group 14). Groups 1 and 5 are here referred to L. edodes and L. aff. edodes, respectively. However, these groups most likely represent the same species and are only recognized as (unsupported) monophyletic lineages by maximum likelihood analyses of ITS alone. Other putative species resolved here include L. lateritia (Group 2), L. novae-zelandieae (Group 3), L. aff. lateritia (Group 4), L. raphanica (Group 6), L. aff. detonsa (Group 9), L. detonsa (Group 10), L. guzmanii sp. nov. (Group 11), L. aciculospora (Group 13), and L. madagasikarensis (Group 15). Groups 9-12 represent the "L. boryana complex". Molecular clock and historical biogeographic analyses suggest that the most recent common ancestor (MRCA) of Lentinula can be placed in the middle Oligocene, ca. 30 million years ago (Ma), and had a likely presence in neotropical America. The MRCA of Lentinula in the Americas and Madagascar lived ca. 22 Ma in the Neotropics and the MRCA of Lentinula in Asia-Australasia lived ca. 6 Ma in Oceania. Given the current knowledge about plate tectonics and paleoclimatic models of the last 30 Myr, our phylogenetic hypothesis suggests that the extant distribution of Lentinula is likely to have arisen, in large part, due to long-distance dispersal. Lentinula collections include at least four dubious taxa that need further taxonomic studies: L. reticeps from the USA (Ohio); L. guarapiensis from Paraguay; Lentinus puiggarii from Brazil (São Paulo); and "L. platinedodes" from Vietnam. Approximately ten of the fifteen Groups are reported on Fagaceae, which appears to be the ancestral substrate of Lentinula.
Assuntos
Basidiomycota , Lentinula , Cogumelos Shiitake , Brasil , Humanos , Filogenia , Cogumelos Shiitake/genéticaRESUMO
Amanita cf. lavendula collections in eastern North America, Mexico, and Costa Rica were found to consist of four cryptic taxa, one of which exhibited consistently unreadable nuclear rDNA ITS1-5.8S-ITS2 (fungal barcode) sequences after ITS1 base 130. This taxon is designated here as Amanita cf. lavendula taxon 1. ITS sequences from dikaryotic basidiomata were cloned, but sequences recovered from cloning did not segregate into distinct haplotypes. Rather, there was a mix of haplotypes that varied among themselves predominantly at 28 ITS positions. Analysis of each of these 28 variable bases showed predominantly two alternate bases at each position. Based on these findings and additional sequence data from the nuclear rDNA 28S, RNA polymerase II subunit 2 (RPB2) and mitochondrial rDNA small subunit (SSU) and 23S genes, we speculate that taxon 1 represents an initial hybridization event between two divergent taxa followed by failure of the ribosomal repeat to homogenize. Homogenization failure may be a result of repeated hybridization between divergent internal transcribed spacer (ITS) types with inadequate time for concerted evolution of the ribosomal repeat or, alternately, a complete failure of the ribosomal homogenization process. To our knowledge, this finding represents the first report of a geographically widespread taxon (Canada, eastern USA, Costa Rica) with apparent homogenization failure across all collections. Findings such as these have implications for fungal barcoding efforts and the application of fungal barcodes in identifying environmental sequences.