Towards standardizing taxonomic ranks using divergence times-a case study for reconstruction of the Agaricus taxonomic system

The recognition of taxonomic ranks in the Linnean classification system is largely arbitrary.Some authors have proposed the use of divergence time as a universally standardized criterion.Agaricus(Agaricaceae,Agaricales)is a mushroom genus that contains many species of high commercial value.Recent studies using ITS sequence data discovered 11 new phylogenetic lineages within the genus,however their taxonomic ranks were uncertain due to the lack of criteria to define them within traditional taxonomy.In this study,we analyzed ITS sequence data from 745 collections(nearly 600 being newly generated)including 86 from type specimens of previously recognized subgenera and sections.Many monophyletic groups were recognized,but most basal relationships were unresolved.One hundred and fourteen representatives of the identified ITS clades were selected in order to produce a multi-gene phylogeny based on combined LSU,tef-1α,and rpb2 sequence data.Divergence times within the multi-gene phylogeny were estimated using BEAST v1.8.Based on phylogenetic relationships and with respect to morphology,we propose a revised taxonomic system for Agaricus that considers divergence time as a standardized criterion for establishing taxonomic ranks.We propose to segregate Agaricus into five subgenera and 20 sections.Subgenus Pseudochitonia is substantially emended;circumscription of the subgenera Agaricus and Flavoagaricus is restricted to taxa of sections Agaricus and Arvenses,respectively;and two new subgenera(Minores and Spissicaules)are introduced.Within Pseudochitonia,sections Bivelares,Brunneopicti,Chitonioides,Nigrobrunnescentes,Sanguinolenti and Xanthodermatei are maintained,but the latter two are reduced because we raise subsection Bohusia to sectional rank and a clade within section Xanthodermatei is formally introduced as section Hondenses;and sections Rubricosi,Crassispori,Flocculenti,and Amoeni are introduced.Section Laeticolores is placed in the subgenus Minores and sections Rarolentes and Subrutilescentes are placed in the subgenus Spissicaules.Twenty-two new species belonging to various sections are described.This work exemplifies that ITS data,while useful at lower taxonomic levels(i.e.,detection of species and species groups),are of limited value for inferring deeper phylogenetic relationships.Finally,we suggest that the establishment of a standardized taxonomic system based on divergence times could result in a more objective,and biologically more meaningful,taxonomic ranking of fungi.

The impact of ancestral population size and incomplete lineage sorting on Bayesian estimation of species divergence times

Although the effects of the coalescent process on sequence divergence and genealogies are well understood, the vir- tual majority of studies that use molecular sequences to estimate times of divergence among species have failed to account for the coalescent process. Here we study the impact of ancestral population size and incomplete lineage sorting on Bayesian estimates of species divergence times under the molecular clock when the inference model ignores the coalescent process. Using a combination of mathematical analysis, computer simulations and analysis of real data, we find that the errors on estimates of times and the molecular rate can be substantial when ancestral populations are large and when there is substantial incomplete lineage sorting. For example, in a simple three-species case, we find that if the most precise fossil calibration is placed on the root of the phylogeny, the age of the internal node is overestimated, while if the most precise calibration is placed on the internal node, then the age of the root is underestimated. In both cases, the molecular rate is overestimated. Using simulations on a phylogeny of nine species, we show that substantial errors in time and rate estimates can be obtained even when dating ancient divergence events. We analyse the hominoid phylogeny and show that estimates of the neutral mutation rate obtained while ignoring the coalescent are too high. Using a coalescent-based technique to obtain geological times of divergence, we obtain estimates of the mutation rate that are within experimental estimates and we also obtain substantially older divergence times within the phylogeny [Current Zoology 61 （5）： 874-885, 2015].

Phylogenetic diversity of eastern Asia-eastern North America disjunct plants is mainly associated with divergence time

The underlying causes of biodiversity disparities among geographic regions have long been a fundamental theme in ecology and evolution.However,the patterns of phylogenetic diversity(PD) and phylogenetic beta diversity(PBD) of congeners that are disjunctly distributed between eastern Asia-eastern North America(EA-ENA disjuncts) and their associated factors remain unknown.Here we investigated the standardized effect size of PD(SES-PD),PBD,and potentially associated factors in 11natural mixed forest sites(five in EA and six in ENA) where abundant EA-ENA disjuncts occur.We found that the disjuncts in ENA possessed higher SES-PD than those in EA at the continental scale(1.96vs-1.12),even though the number of disjunct species in ENA is much lower than in EA(128 vs 263).SESPD of the EA-ENA disjuncts tended to decrease with increasing latitude in 11 sites.The latitudinal diversity gradient of SES-PD was stronger in EA sites than in ENA sites.Based on the unweighted unique fraction metric(UniFrac) distance and the phylogenetic community dissimilarity,PBD showed that the two northern sites in EA were more similar to the six-site ENA group than to the remaining southern EA sites.Based on the standardized effect size of mean pairwise distances(SES-MPD),nine of eleven studied sites showed a neutral community structure(-1.96 ≤SES-MPD ≤1.96).Both Pearson’s r and structural equation modeling suggested that SES-PD of the EA-ENA disjuncts was mostly associated with mean divergence time.Moreover,SES-PD of the EA-ENA disjuncts was positively correlated with temperaturerelated climatic factors,although negatively correlated with mean diversification rate and community structure.By applying approaches from phylogenetics and community ecology,our work sheds light on historical patterns of the EA-ENA disjunction and paves the way for further research.

Evolutionary timescale of chalcidoid wasps inferred from over one hundred mitochondrial genomes

Chalcidoidea is one of the most biologically diverse groups among Hymenoptera.Members are characterized by extraordinary parasitic lifestyles and extensive host ranges,among which several species attack plants or serve as pollinators.However,higher-level chalcidoid relationships remain controversial.Here,we performed mitochondrial phylogenomic analyses for major clades(18out of 25 families)of Chalcidoidea based on 139 mitochondrial genomes.The compositional heterogeneity and conflicting backbone relationships in Chalcidoidea were assessed using various datasets and tree inferences.Our phylogenetic results supported the monophyly of 16families and polyphyly of Aphelinidae and Pteromalidae.Our preferred topology recovered the relationship(Mymaridae+(Signiphoridae+Leucospidae)+(Chalcididae+((Perilampidae+Eucharitidae)+remaining Chalcidoidea))).The monophyly of Agaonidae and Sycophaginae was rejected,while the gall-associated((Megastigmidae+Ormyridae)+(Ormocerinae+Eurytomidae))relationship was supported in most results.A six-gene inversion may be a synapomorphy for most families,whereas other derived gene orders may introduce confusion in phylogenetic signals at deeper nodes.Dating estimates suggested that Chalcidoidea arose near the Jurassic/Cretaceous boundary and that two dynamic shifts in diversification occurred during the evolution of Chalcidoidea.We hypothesized that the potential codiversification between chalcidoids and their hosts may be crucial for accelerating the diversification of Chalcidoidea.Ancestral state reconstruction analyses supported the hypothesis that gallinducers were mainly derived from parasitoids of gallinducers,while other gall-inducers were derived from phytophagous groups.Taken together,these findings advance our understanding of mitochondrial genome evolution in the major interfamilial phylogeny of Chalcidoidea.

A new species of Discostella guiyangensis sp.nov.(Bacillariophyta,Stephanodiscales)from Guiyang,China:morphology and phylogeny

We describe a new species of Discostella from Guiyang based on light and scanning electron microscopic observations,as well as molecular analysis.This species is morphologically distinguished from other species by a relatively smooth and slightly recessed central area with marginal striae of unequal lengths forked near the margin.Marginal fultoportulae and a single rimoportula are situated between every two costae or on the costae.Both morphological characters and the concatenated data of rbc L and SSU rDNA indicate that Discostella guiyangensis is a unique and new species.According to divergence time estimation analysis,Discostella guiyangensis is the oldest species among the Discostella species sequenced currently.In addition,we complement molecular data of Discostella asterocostata and Discostella stelligera.

Divergence time, historical biogeography and evolutionary rate estimation of the order Bangiales (Rhodophyta) inferred from multilocus data

Bangiales is the only order of the Bangiophyceae and has been suggested to be monophyletic. This order contains approximately 190 species and is distributed worldwide. Previous molecular studies have produced robust phylogenies among the red algae, but the divergence times, historical biogeography and evolutionary rates of Bangiales have rarely been studied. Phylogenetic relationships within the Bangiales were examined using the concatenated gene sets from all available organellar genomes. This analysis has revealed the topology((( Bangia, Porphyra) Pyropia) Wildemania). Molecular dating indicates that Bangiales diversifi ed approximately 246.40 million years ago(95% highest posterior density(HPD)= 194.78–318.24 Ma, posterior probability(PP)=0.99) in the Late Permian and Early Triassic, and that the ancestral species most likely originated from eastern Gondwanaland(currently New Zealand and Australia) and subsequently began to spread and evolve worldwide. Based on pairwise comparisons, we found a slower rate of nucleotide substitutions and lower rates of diversifi cation in Bangiales relative to Florideophyceae. Compared with Viridiplantae(green algae and land plants), the evolutionary rates of Bangiales and other Rhodophyte groups were found to be dramatically faster, by more than 3-fold for plastid genome(ptDNA) and 15-fold for mitochondrial genome(mtDNA). In addition, an average 2.5-fold lower dN/dS was found for the algae than for the land plants, which indicates purifying selection of the algae.

Insights into cryptic speciation of quillworts in China

Cryptic species are commonly misidentified because of high morphological similarities to other species.One group of plants that may harbor large numbers of cryptic species is the quillworts(Isoetes spp.),an ancient aquatic plant lineage.Although over 350 species of Isoetes have been reported globally,only ten species have been recorded in China.The aim of this study is to better understand Isoetes species diversity in China.For this purpose,we systematically explored the phylogeny and evolution of Isoetes using complete chloroplast genome(plastome)data,spore morphology,chromosome number,genetic structure,and haplotypes of almost all Chinese Isoetes populations.We identified three ploidy levels of Isoetes in Chinaddiploid(2n=22),tetraploid(2n=44),and hexaploid(2n=66).We also found four megaspore and microspore ornamentation types in diploids,six in tetraploids,and three in hexaploids.Phylogenetic analyses confirmed that I.hypsophila as the ancestral group of the genus and revealed that Isoetes diploids,tetraploids,and hexaploids do not form monophyletic clades.Most individual species possess a single genetic structure;however,several samples have conflicting positions on the phylogenetic tree based on SNPs and the tree based on plastome data.All 36 samples shared 22 haplotypes.Divergence time analysis showed that I.hypsophila diverged in the early Eocene(~48.05 Ma),and most other Isoetes species diverged 3-20 Ma.Additionally,different species of Isoetes were found to inhabit different water systems and environments along the Yangtze River.These findings provide new insights into the relationships among Isoetes species in China,where highly similar morphologic populations may harbor many cryptic species.

Molecular phylogeny and identification of agromyzid leafminers in China,with a focus on the worldwide genus Liriomyza(Diptera:Agromyzidae)

Leaf-mining flies(Diptera:Agromyzidae)are a diverse family of small-bodied insects that feed on living plant tissues as larvae.Various species in this family are considered globally invasive and have caused great agricultural economic losses.In China,economically important vegetable crops have been seriously damaged by these pest insects,especially by species of the genus Liriomyza.However,these species are difficult to differentiate because of their morphological similarities,and the Chinese fauna remains poorly known.To explore the relevant pest species in China and their phylogeny,agromyzid leafminers were collected from 2016 to 2019,and identified based on morphological characteristics and DNA barcodes.In total,27 species from five genera of Agromyzidae were sampled and identified,including 16species of Liriomyza.Both mitochondrial and nuclear genes were used to reconstruct their phylogenetic relationships and estimate the divergence time.Highly congruent and well-supported phylogenetic trees were obtained using the Bayesian inference and maximum-likelihood methods.This analysis revealed two main clades in Liriomyza,and clade 2was inferred to have diverged from clade 1 approximately 27.40 million years ago(95%highest posterior density:23.03–31.52 million years ago)in the Oligocene.Differences were observed in the distribution patterns and host associations between the Liriomyza clades.Clade 2 species are distributed in cool,high-latitude environments,suggesting that they may have evolved into a cool-adapted lineage.

Phylogenetic relationships of five species of Dorippinae (Crustacea, Decapoda) revealed by 16S rDNA sequence analysis

A molecular phytogeny is presented for the subfamily Dorippinae (including 9 individuals, representing 5 species and 4 genera), based on the sequence data from 16S rRNA gene. Two-cluster test between lineages in these phylogenetic trees has been performed. On the basis of rate constancy, the rate of nucleotide substitutions of 16S rDNA sequence data is estimated as 0.27% per million years. The analysis strongly supports the recognition of the Dorippinae as a monophyletic subfamily. Phylogenetic tree indicates that the subfamily Dorippinae is divided into two main clades, and genus Dorippe appears basal in the subfamily, diverging from other species 36.6 Ma ago. It is also clear that the Heikea is closely related to the genus Neodorippe. The divergence time between them is 15.8 Ma.

Phylogenetic biogeography and taxonomy of disjunctly distributed bryophytes

More than 200 research papers on the molecular phylogeny and phylogenetic biogeography ofbryophytes have been published since the beginning of this millenium. These papers corroborated assumptions of a complex genetic structure of morphologically circumscribed bryophytes, and raised reservations against many morphologically justified species concepts, especially within the mosses. However, many molecular studies allowed for corrections and modifications of morphological classification schemes. Several studies reported that the phylogenetic structure of disjunctly distributed bryophyte species reflects their geographical ranges rather than morphological disparities. Molecular data led to new appraisals of distribution ranges and allowed for the reconstruction of refugia and migration routes. Intercontinental ranges of bryophytes are often caused by dispersal rather than geographical vicariance. Many distribution patterns of disjunct bryophytes are likely formed by processes such as short distance dispersal, rare long distance dispersal events, extinction, recolonization and diversification.

Phylogenetics and biogeography of eastern Asian–North American disjunct genus Pachysandra (Buxaceae) inferred from nucleotide sequences

Pachysandra is an eastern Asian-North American disjtunct genus with three species, two in eastern Asia （Pachysandra axillaris and Pachysandra terminalis） and one in eastern North America （Pachysandra procurnbens）. Although morphological and cytological studies suggest a close affinity of Pprocumbens with P axillaris, molecular data from nuclear and chloroplast DNA regions have provided conflicting signals. In this study, we tested previous phylogenetic hypotheses using sequences of nuclear ribosomal DNA internal transcribed spacers and chloroplast ndhF gene from multiple individuals of each of the three species. We also estimated the time of divergence between eastem Asia and eastern North America. Our results support the morphological and cytological conclusion that P procumbens is more closely related to P axillaris than to P terminalis. The estimated time of divergence of P axillaris and P procumbens was 14.6±5.5 mya, consistent with estimates from many other eastern Asian-North American disjunct genera. The migration of Pachysandra populations from eastern Asia to North America might have occurred by way of the North Atlantic land bridge.

Phylogenetic, evolutionary, and biogeographic origin of the genus Sheathia (Batrachospermales, Rhodophyta)

The genus Sheathia consists of over 20 species primarily distributed in Asia,Europe,Oceania,North America,and Africa.However,the origin and evolution of this genus remain unclear.Two gametophyte stage specimens(SAS18052 and SAS18523)and two“Chantransia”stage specimens(YTS19161 and YTS19017)were collected from Shanxi and Henan Provinces in China,respectively.Based on morphological data,isolates YTS19161 and YTS19017 were similar to Audouinella pygmaea,whereas the morphological characteristics of SAS18052 and SAS18523 were in good agreement with the circumscription description of S.longipedicellata.Molecular sequences of rbc L,COI-5P,and psb A were used to investigate the phylogenetic,evolutionary,and biogeographic origin of the genus Sheathia.The three molecular markers supported that the two gametophyte stage specimens belong to S.longipedicellata,while the isolates YTS19161 and YTS19017 were the“Chantransia”of S.longipedicellata.Ancestral area reconstruction and divergence time estimation speculated that Sheathia originated in North America,a portion of the Pangaea at approximately 328.07-184.73 million years ago(Ma).Our relaxed molecular clock analysis suggests that the Florideophyceae diverged approximately 741.04(894.36-631.70)Ma.The major divergences in this class involved the emergence of Nemaliophycidae[ca.662.01(779.83-580.51)Ma],and the split of orders Batrachospermales and Thoreales[ca.456.10(552.80-367.88)Ma].

Maximal sequence length of exact match between members from a gene family during early evolution

Mutation (substitution, deletion, insertion, etc.) in nucleotide acid causes the maximal sequence lengths of exact match (MALE) between paralogous members from a duplicate event to become shorter during evolution. In this work, MALE changes between members of 26 gene families from four representative species (Arabidopsis thaliana, Oryza sativa, Mus mus- culus and Homo sapiens) were investigated. Comparative study of paralogous’ MALE and amino acid substitution rate (dA<0.5) indicated that a close relationship existed between them. The results suggested that MALE could be a sound evolutionary scale for the divergent time for paralogous genes during their early evolution. A reference table between MALE and divergent time for the four species was set up, which would be useful widely, for large-scale genome alignment and comparison. As an example, de- tection of large-scale duplication events of rice genome based on the table was illustrated.

Population genomic analysis unravels the evolutionary roadmap of pericarp color in rice

Pigmented rice stands out for its nutritional value and is gaining more and more attention.Wild rice,domes-ticated red rice,and weedy rice all have a red pericarp and a comprehensive genetic background in terms of the red-pericarp phenotype.We performed population genetic analyses using 5104 worldwide rice acces-sions,including 2794 accessions with red or black pericarps,85 of which were newly sequenced in this study.The results suggested an evolutionary trajectory of red landraces originating from wild rice,and the split times of cultivated red and white rice populations were estimated to be within the past 3500 years.Cultivated red rice was found to feralize to weedy rice,and weedy rice could be further re-domesticated to cultivated red rice.A genome-wide association study based on the 2794 accessions with pigmented peri-carps revealed several new candidate genes associated with the red-pericarp trait for further functional characterization.Our results provide genomic evidence for the origin of pigmented rice and a valuable genomic resource for genetic investigation and breeding of pigmented rice.

Phylogeny,divergence time estimation,and biogeography of the genus Heterobasidion(Basidiomycota,Russulales)

There have been several investigations into the genus Heterobasidion,however,differentiation of species in these studies have depended on the gene regions analyzed.Reliable defining of species,establishing species divergence times and establishing species biogeographical distributions have been challenging.Here,we used a multilocus phylogenetic approach and maximum parsimony,maximum likehood,and Bayesian analyses to infer the phylogenetic relationships of Heterobasidion species.In addition,we focused on a fungus fossil-based approach and used the largest subunit of RNA polymerase II-the second subunit of RNA polymerase II(RPB1-RPB2)dataset to perform maximum likelihoodbased estimation and Bayesian binary analyses,to assess the divergence and biogeographical distributions of Heterobasidion species.The Heterobasidion annousum/H.insulare species complex clusters in three groups in the phylogenetic analyses.Molecular dating suggests that ancestral Heterobasidion species originated in Eurasia during the Early Miocene,followed by dispersal and speciation to other continents during the Middle Miocene and Early Pliocene.Our data are compatible with the previous viewpoint that H.irregulare and H.occidentale colonized North America via different routes,which has been interpreted as Beringian and Thulean North Atlantic vicariance.In addition,we propose that the occurrence of H.araucariae in the southern Hemisphere was probably due to recent human-mediated introductions.Plate tectonics and long-distance dispersal are the most likely factors that influenced Heterobasidion speciation and biogeography.

Ancient DNA sequences from Coelodonta antiquitatis in China reveal its divergence and phylogeny

Ancient DNA data have supported a sister relationship between woolly rhinoceros and extant Sumatran rhinoceros.This relationship has been used to explore the divergent times for the woolly rhinoceros from their relatives.Complete and partial ancient DNA sequences of the mitochondrial cytochrome b(cyt b)gene were retrieved from bones of the late Pleistocene Coelodonta antiquitatis excavated from northern and northeastern China.The newly obtained sequences together with the European and northern Asian Coelodonta antiquitatis sequences from GenBank were used to estimate the evolutionary divergence time.Phylogenetic analyses showed the exchange of genetic information between the Chinese individuals and Coelodonta antiquitatis of north Asia,which also indicated a more recent evolutionary timescale(3.8–4.7 Ma)than previous molecular estimations(17.5–22.8 or 21–26 Ma)for woolly rhinoceros based on the fossil calibration of outgroups.This new timescale was more consistent with the fossil record of the earliest known genus Coelodonta.

Chromosome-scale genomes provide new insights into subspecies divergence and evolutionary characteristics of the giant panda

Extant giant pandas are divided into Sichuan and Qinling subspecies.The giant panda has many speciesspecific characteristics,including comparatively small organs for body size,small genitalia of male individuals,and low reproduction.Here,we report the most contiguous,high-quality chromosomelevel genomes of two extant giant panda subspecies to date,with the first genome assembly of the Qinling subspecies.Compared with the previously assembled giant panda genomes based on short reads,our two assembled genomes increased contiguity over 200-fold at the contig level.Additional sequencing of 25 individuals dated the divergence of the Sichuan and Qinling subspecies into two distinct clusters from 10,000 to 12,000 years ago.Comparative genomic analyses identified the loss of regulatory elements in the dachshund family transcription factor 2(DACH2)gene and specific changes in the synaptotagmin 6(SYT6)gene,which may be responsible for the reduced fertility of the giant panda.Positive selection analysis between the two subspecies indicated that the reproduction-associated IQ motif containing D(IQCD)gene may at least partly explain the different reproduction rates of the two subspecies.Furthermore,several genes in the Hippo pathway exhibited signs of rapid evolution with giant panda-specific variants and divergent regulatory elements,which may contribute to the reduced inner organ sizes of the giant panda.

Genome-scale angiosperm phylogenies based on nuclear,plastome,and mitochondrial datasets

Angiosperms dominate the Earth’s ecosystems and provide most of the basic necessities for human life.The major angiosperm clades comprise 64 orders,as recognized by the APGⅣclassification.However,the phylogenetic relationships of angiosperms remain unclear,as phylogenetic trees with different topologies have been reconstructed depending on the sequence datasets utilized,from targeted genes to transcriptomes.Here,we used currently available de novo genome data to reconstruct the phylogenies of 366 angiosperm species from 241 genera belonging to 97 families across 43 of the 64 orders based on orthologous genes from the nuclear,plastid,and mitochondrial genomes of the same species with compatible datasets.The phylogenetic relationships were largely consistent with previously constructed phylogenies based on sequence variations in each genome type.However,there were major inconsistencies in the phylogenetic relationships of the five Mesangiospermae lineages when different genomes were examined.We discuss ways to address these inconsistencies,which could ultimately lead to the reconstruction of a comprehensive angiosperm tree of life.The angiosperm phylogenies presented here provide a basic framework for further updates and comparisons.These phylogenies can also be used as guides to examine the evolutionary trajectories among the three genome types during lineage radiation.

Taxonomy,phylogeny and evolution of freshwater Hypocreomycetidae(Sordariomycetes)

Hypocreomycetidae is a highly diverse group with species from various habitats. This subclass has been reported as pathogenic,endophytic, parasitic, saprobic, fungicolous, lichenicolous, algicolous, coprophilous and insect fungi from aquatic andterrestrial habitats. In this study, we focused on freshwater fungi of Hypocreomycetidae which resulted 41 fresh collectionsfrom China and Thailand. Based on morphological and phylogenetic analyses, we identified 26 species that belong to twoorders (Hypocreales and Microascales) and six families (Bionectriaceae, Halosphaeriaceae, Microascaceae, Nectriaceae,Sarocladiaceae and Stachybotryaceae). Ten new species are introduced and 13 new habitats and geographic records arereported. Mariannaea superimposita, Stachybotrys chartarum and S. chlorohalonatus are recollected from freshwater habitatsin China. Based on phylogenetic analysis of combined LSU, ITS, SSU, rpb2 and tef1-α sequences data, Emericellopsisis transferred to Hypocreales genera incertae sedis;Pseudoacremonium is transferred to Bionectriaceae;Sedecimiella isplaced in Nectriaceae;Nautosphaeria and Tubakiella are excluded from Halosphaeriaceae and placed in Microascalesgenera incertae sedis;and Faurelina is excluded from Hypocreomycetidae. Varicosporella is placed under Atractium as asynonym of Atractium. In addition, phylogenetic analysis and divergence time estimates showed that Ascocodina, Campylospora,Cornuvesica and Xenodactylariaceae form distinct lineages in Hypocreomycetidae and they evolved in the family/order time frame. Hence, a new order (Xenodactylariales) and three new families (Ascocodinaceae, Campylosporaceae andCornuvesicaceae) are introduced based on phylogenetic analysis, divergence time estimations and morphological characters.Ancestral character state analysis is performed for different habitats of Hypocreomycetidae including freshwater, marineand terrestrial taxa. The result indicates that marine and freshwater fungi evolved independently from terrestrial ancestors.The results further support those early diverging clades of this subclass, mostly comprising terrestrial taxa and freshwaterand marine taxa have been secondarily derived, while the crown clade (Nectriaceae) is represented in all three habitats. Theevolution of various morphological adaptations towards their habitual changes are also discussed.

Nuclear phylotranscriptomics and phylogenomics support numerous polyploidization events and hypotheses for the evolution of rhizobial nitrogenfixing symbiosis in Fabaceae

Fabaceae are the third largest angiosperm family,with 765 genera and~19500 species.They are important both economically and ecologically,and global Fabaceae crops are intensively studied in part for their nitrogen-fixing ability.However,resolution of the intrasubfamilial Fabaceae phylogeny and divergence times has remained elusive,precluding a reconstruction of the evolutionary history of symbiotic nitrogen fixation in Fabaceae.Here,we report a highly resolved phylogeny using>1500 nuclear genes from newly sequenced transcriptomes and genomes of 391 species,along with other datasets,for a total of 463 legumes spanning all 6 subfamilies and 333 of 765 genera.The subfamilies are maximally supported as mono-phyletic.The clade comprising subfamilies Cercidoideae and Detarioideae is sister to the remaining legumes,and Duparquetioideae and Dialioideae are successive sisters to the clade of Papilionoideae and Caesalpinioideae.Molecular clock estimation revealed an early radiation of subfamilies near the K/Pg boundary,marked by mass extinction,and subsequent divergence of most tribe-level clades within~15 million years.Phylogenomic analyses of thousands of gene families support 28 proposed putative whole-genome duplication/whole-genome triplication events across Fabaceae,including those at the ancestors of Fabaceae and five of the subfamilies,and further analyses supported the Fabaceae ancestral polyploidy.The evolution of rhizobial nitrogen-fixing nodulation in Fabaceae was probed by ancestral character reconstruction and phylogenetic analyses of related gene families and the results support the hypotheses of one or two switches)to rhizobial nodulation followed by multiple losses.Collectively,these results provide a foundation for further morphological and functional evolutionary analyses across Fabaceae.