Aim: The ectomycorrhizal genus Strobilomyces is widely distributed throughout many parts of the world, but its origin, divergence and distribution patterns remain largely unresolved. In this study, we aim to explore the species diversity, distribution and evolutionary patterns of Strobilomyces on a global scale by establishing a general phylogenetic framework with extensive sampling.Location: Africa, Australasia, East Asia, Europe, North America, Central America and Southeast Asia.
Methods:The genealogical concordance phylogenetic species recognition method was used to delimit phylogenetic species. Divergence times were estimated using a Bayesian uncorrelated lognormal relaxed molecular clock. The ancestral area and host of Strobilomyces were inferred via the programs RASP and MESQUITE. The change of diversification rate over time was estimated using Ape, Laser and Bammtools software packages.Results: We recognize a novel African clade and 49 phylogenetic species with morphological evidence, including 18 new phylogenetic species and 23 previously described ones. Strobilomyces probably originated in Africa, in association with Detarioideae/Phyllanthaceae/Monotoideae during the early Eocene. The dispersal to Southeast Asia can be explained by Wolfe's "Boreotropical migration" hypothesis.East Asia, Australasia, Europe and North/Central America are primarily the recipients of immigrant taxa during the Oligocene or later. A rapid radiation implied by one diversification shift was inferred within Strobilomyces during the Miocene.Main conclusions: An unexpected phylogenetic species diversity within Strobilomyces was uncovered. The highest diversity, resulting probably from a rapid
BackgroundDNA barcoding has been developed as a useful tool for species discrimination. Several sequence-based species delimitation methods, such as Barcode Index Number (BIN), REfined Single Linkage (RESL), Automatic Barcode Gap Discovery (ABGD), a Java program uses an explicit, determinate algorithm to define Molecular Operational Taxonomic Unit (jMOTU), Generalized Mixed Yule Coalescent (GMYC), and Bayesian implementation of the Poisson Tree Processes model (bPTP), were used. Our aim was to estimate Chinese katydid biodiversity using standard DNA barcode cytochrome c oxidase subunit I (COI-5P) sequences.ResultsDetection of a barcoding gap by similarity-based analyses and clustering-base analyses indicated that 131 identified morphological species (morphospecies) were assigned to 196 BINs and were divided into four categories: (i) MATCH (83/131 = 64.89%), morphospecies were a perfect match between morphospecies and BINs (including 61 concordant BINs and 22 singleton BINs); (ii) MERGE (14/131 = 10.69%), morphospecies shared its unique BIN with other species; (iii) SPLIT (33/131 = 25.19%, when 22 singleton species were excluded, it rose to 33/109 = 30.28%), morphospecies were placed in more than one BIN; (iv) MIXTURE (4/131 = 5.34%), morphospecies showed a more complex partition involving both a merge and a split. Neighbor-joining (NJ) analyses showed that nearly all BINs and most morphospecies formed monophyletic cluster with little variation. The molecular operational taxonomic units (MOTUs) were defined considering only the more inclusive clades found by at least four of seven species delimitation methods. Our results robustly supported 61 of 109 (55.96%) morphospecies represented by more than one specimen, 159 of 213 (74.65%) concordant BINs, and 3 of 8 (37.5%) discordant BINs.ConclusionsMolecular species delimitation analyses generated a larger number of MOTUs compared with morphospecies. If these MOTU splits are proven to be true, Chinese katydids probably contain a seemingly large proportion of cryptic/undescribed taxa. Future amplification of additional molecular markers, particularly from the nuclear DNA, may be especially useful for specimens that were identified here as problematic taxa.Electronic supplementary materialThe online version of this article (10.1186/s12862-019-1404-5) contains supplementary material, which is available to authorized users.
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