Polarity of peatmoss (Sphagnum) evolution: who says bryophytes have no roots?

The class Sphagnopsida (Bryophyta) includes two genera: Ambuchanania and Sphagnum. Ambuchanania contains just one rare species known from two Tasmanian localities, but Sphagnum comprises a speciose clade of mosses that dominates many wetland ecosystems, especially in the boreal zone of the Northern Hemisphere. Recent phylogenetic analyses have resolved well-supported clades within Sphagnum, but polarizing Sphagnum evolution has been problematic because the genus is so isolated that it is difficult to determine homologies between morphological and/or molecular traits within Sphagnum with those of any potential outgroup. DNA sequences from 16 genomic regions representing the mitochondrial, chloroplast, and nuclear genomes (ca. 16 kilobases) were obtained from 24 species of Sphagnum plus one species each from Takakia and Andreaea in order to resolve a rooted phylogeny. Two tropical species, S. sericeum and S. lapazense, were resolved as sister to the rest of the genus and are extremely divergent from all other sphagna. The main Sphagnum lineage consists of two clades; one includes the sections Sphagnum, Rigida, and Cuspidata, and the other includes Subsecunda, Acutifolia, and Squarrosa. The placement of section Subsecunda is weakly supported, but other nodes are strongly supported by maximum parsimony, maximum likelihood, and Bayesian analyses. In addition to homogeneous Bayesian analyses, heterogeneous models were employed to account for different patterns of nucleotide substitution among genomic regions.     

基部藓类分子系统学研究

基部藓类是稳定地处于藓类系统发育树基部的类群.它包括7纲,2亚纲,10目,10科,34属,637种.基部藓类虽然只占藓类种类的5％,但由于其内部各类群孢子体形态极为丰富,因此对于理解整个藓类植物的系统发育具有重要意义.通过对48个种(36个藓类、4个维管植物、2个角苔、4个苔类和2个藻类)的9个DNA片段(NU:26S,18S; MT:nad5,cox1; CP:rbcL,rps4,cp-LSU,cp-SSU,atpB)进行分子系统学分析,综合最大似然法(maximum likelihood)、最大简约法(most parsimony)和贝叶斯分析(Bayesian inference)方法的建树结果,理清了前人研究中存在冲突的类群之间的关系并为已确定的关系提供了更高的支持率.研究结果如下:(1)藻苔纲和泥炭藓纲互为姐妹类群,处于整个藓类的最基部;(2)黑藓纲与黑真藓纲互为姐妹类群(3)长台藓纲和具齿藓类组成单系;(4)四齿藓纲是所有具齿藓类的基部类群;(5)烟杆藓亚纲处于真藓纲的最基部,其次是短颈藓亚纲.以上结论在分子系统树上得到了很高的支持率.     

Development of the enigmatic peristome of Timmia megapolitana (Timmiaceae; Bryophyta)

The Timmiaceae (Bryophyta) have been traditionally classified within the Bryales based on peristome architecture. Phylogenetic analyses of nucleotide sequences have revealed relationships that are incongruent with this hypothesis and have implicated an origin for this lineage early in the radiation of arthrodontous mosses (Bryopsida). This unexpected phylogenetic placement raises important questions about the evolutionary significance of the Timmia peristome, which differs from all other mosses by 64 isomorphic filaments topping the endostomial membrane. A developmental study of the peristome in Timmia megapolitana was undertaken to examine alignments of anticlinal cell walls in the inner peristomial layer (IPL) with those of the primary peristomial layer (PPL), a character that has been used to define major arthrodontous lineages. Criteria were established for assessing longitudinally homologous regions that contribute to the peristome-forming region. Young sporophytes were examined using histological techniques, and the alignment of the cell wall divisions was quantified. Critical divisions in the IPL of T. megapolitana were determined to be symmetrical, similar to patterns in the Funariales. This research provides novel developmental observations for a putative ancestral lineage of arthrodontous mosses, reevaluates criteria used to compare developmental studies of different lineages and discusses the phylogenetic implications of these observations.     

Phylogenetic relationships of Moxostoma and Scartomyzon (Catostomidae) based on mitochondrial cytochrome b sequence data

A recent phylogenetic study based on morphological, biochemical and early life history characters resurrected the genus Scartomyzon (jumprock suckers, c . eight−10 species) from Moxostoma (redhorse suckers, c . 10–11 species) and advanced the understanding of relationships among species in these two genera, and the genealogical affinities of these genera with other evolutionary lineages within the tribe Moxostomatini in the subfamily Catostominae. To further examine phylogenetic relationships among moxostomatin suckers, the complete mitochondrial (mt) cytochrome b gene was sequenced from all species within this tribe and representative outgroup taxa from the Catostomini and other catostomid subfamilies. Phylogenetic analysis of gene sequences yielded two monophyletic clades within Catostominae: Catostomus + Deltistes + Xyrauchen + Erimyzon + Minytrema and Moxostoma + Scartomyzon + Hypentelium + Thoburnia . Within the Moxostomatini, Thoburnia was either unresolved or polyphyletic; Thoburnia atripinnis was sister to a monophyletic Hypentelium . In turn, this clade was sister to a monophyletic clade containing Scartomyzon and Moxostoma . Scartomyzon was never resolved as monophyletic, but was always recovered as a polyphyletic group embedded within Moxostoma , rendering the latter genus paraphyletic if ' Scartomyzon ' continues to be recognized. Relationships among lineages within the Moxostoma and' Scartomyzon 'clade were resolved as a polytomy. To better reflect phylogenetic relationships resolved in this analysis, the following changes to the classification of the tribe Moxostomatini are proposed: subsumption of' Scartomyzon 'into Moxostoma ; restriction of the tribe Moxostomatini to Moxostoma ; resurrect the tribe Erimyzonini, containing Erimyzon and Minytrema , classified as incertae sedis within Catostominae; retain the tribe Thoburniini.     

Evolutionary history of the Corallinales (Corallinophycidae, Rhodophyta) inferred from nuclear, plastidial and mitochondrial genomes

Systematics of the red algal order Corallinales has a long and convoluted history. In the present study, molecular approaches were used to assess the phylogenetic relationships based on the analyses of two datasets: a large dataset of SSU sequences including mainly sequences from GenBank; and a combined dataset including four molecular markers (two nuclear: SSU, LSU; one plastidial: psbA; and one mitochondrial: COI). Phylogenetic analyses of both datasets re-affirmed the monophyly of the Corallinales as well as the two families (Corallinaceae and Hapalidiaceae) currently recognized within the order. Three of the four subfamilies of the Corallinaceae (Corallinoideae, Lithophylloideae, Metagoniolithoideae) were also resolved as a monophyletic lineage whereas members of the Mastophoroideae were resolved as four distinct lineages. We therefore propose to restrict the Mastophoroideae to the genera Mastophora, Metamastophora, and possibly Lithoporella in the aim of rendering this subfamily monophyletic. In addition, our phylogenies resolved the genus Hydrolithon in two unrelated lineages, one containing the generitype Hydrolithon reinboldii and the second containing Hydrolithon onkodes, which used to be the generitype of the now defunct genus Porolithon. We therefore propose to resurrect the genus Porolithon for the second lineage encompassing those species with primarily monomerous thalli, and trichocyte arrangements in large pustulate horizontal rows. Moreover, our phylogenetic analyses revealed the presence of cryptic diversity in several taxa, shedding light on the need for further studies to better circumscribe species frontiers within the diverse order Corallinales, especially in the genera Mesophyllum and Neogoniolithon.     

RADseq resolves the phylogeny of Hawaiian Myrsine (Primulaceae) and provides evidence for hybridization

The Hawaiian radiation of Myrsine (primrose family, Primulaceae) is the only one among the ten most species‐rich Hawaiian plant lineages that has never been included in a phylogenetic analysis. Our study is based on a RADseq dataset of nearly all Hawaiian Myrsine species and a Sanger sequencing dataset based on a worldwide sampling of Myrsine and related genera. Myrsine as a whole might be paraphyletic with respect to the monotypic Macaronesian genera Heberdenia and Pleiomeris, whereas Hawaiian Myrsine is resolved as monophyletic. The Sanger sequencing proved to be insufficient to resolve the Hawaiian lineage, whereas RADseq fully resolved the relationships with high support. Hawaiian Myrsine consists of three main lineages, of which one contains the majority of species and is mainly confined to Kauaʻi, and the other two lineages primarily consist of few widespread species. Although phylogenetic reconstructions delivered fully resolved and supported tree topologies, Quartet Sampling and HyDe analyses reveal phylogenetic incongruence throughout the phylogeny and provide the first molecular evidence of extensive hybridization in the lineage.     

Phylogeny of muroid rodents: relationships within and among major lineages as determined by IRBP gene sequences

The rodent family Muridae is the single most diverse family of mammals with over 1300 recognized species. We used DNA sequences from the first exon ( approximately 1200bp) of the IRBP gene to infer phylogenetic relationships within and among the major lineages of muroid rodents. We included sequences from every recognized muroid subfamily except Platacanthomyinae and from all genera within the endemic Malagasy subfamily Nesomyinae, all recognized tribes of Sigmodontinae, and a broad sample of genera in Murinae. Phylogenetic analysis of the IRBP data suggest that muroid rodents can be sorted into five major lineages: (1) a basal clade containing the fossorial rodents in the subfamilies Spalacinae, Myospalacinae, and Rhizomyinae, (2) a clade of African and Malagasy genera comprising the subfamilies Petromyscinae, Mystromyinae, Cricetomyinae, Nesomyinae, and core dendromurines, (3) a clade of Old World taxa belonging to Murinae, Otomyinae, Gerbillinae, Acomyinae, and Lophiomyinae, (4) a clade uniting the subfamilies Sigmodontinae, Arvicolinae, and Cricetinae, and (5) a unique lineage containing the monotypic Calomyscinae. Although relationships among the latter four clades cannot be resolved, several well-supported supergeneric groupings within each are identified. A preliminary examination of molar tooth morphology on the resulting phylogeny suggests the triserial murid molar pattern as conceived by evolved at least three times during the course of muroid evolution.     

Detection, isolation, and characterization of acidophilic methanotrophs from Sphagnum mosses

Sphagnum peatlands are important ecosystems in the methane cycle. Methane-oxidizing bacteria in these ecosystems serve as a methane filter and limit methane emissions. Yet little is known about the diversity and identity of the methanotrophs present in and on Sphagnum mosses of peatlands, and only a few isolates are known. The methanotrophic community in Sphagnum mosses, originating from a Dutch peat bog, was investigated using a pmoA microarray. A high biodiversity of both gamma- and alphaproteobacterial methanotrophs was found. With Sphagnum mosses as the inoculum, alpha- and gammaproteobacterial acidophilic methanotrophs were isolated using established and newly designed media. The 16S rRNA, pmoA, pxmA, and mmoX gene sequences showed that the alphaproteobacterial isolates belonged to the Methylocystis and Methylosinus genera. The Methylosinus species isolated are the first acid-tolerant members of this genus. Of the acidophilic gammaproteobacterial strains isolated, strain M5 was affiliated with the Methylomonas genus, and the other strain, M200, may represent a novel genus, most closely related to the genera Methylosoma and Methylovulum. So far, no acidophilic or acid-tolerant methanotrophs in the Gammaproteobacteria class are known. All strains showed the typical features of either type I or II methanotrophs and are, to the best of our knowledge, the first isolated (acidophilic or acid-tolerant) methanotrophs from Sphagnum mosses.     

Patterns of clade support across the major lineages of moss phylogeny

Relationships among the major branches of moss phylogeny are understudied compared with other major land‐plant groups. We addressed this by surveying 14–17 plastid genes from taxa representing the major lineages, using different phylogenetic methods (parsimony, likelihood) and codon‐ and gene‐based data partitioning schemes (likelihood). Our phylogenetic inferences generally corroborated the best supported clades across multiple recent studies, with comparable or higher levels of clade support here. We resolved persistent ambiguities with strong to moderate support across analyses, including several early nodes in subclass Dicranidae, and relationships among other subclasses of peristomate mosses. In particular, we resolved a sister‐group relationship between Bryidae and Dicranidae, between these subclasses and Timiidae, and between this entire clade and Funariidae. We consistently recovered Tetraphidopsida (a nematodontous class) as the sister group of arthrodontous mosses (Bryopsida), although with only weak support. Strongly conflicting arrangements at the base of moss phylogeny concerning Takakiopsida and Sphagnopsida, two non‐peristomate moss lineages, were inferred in parsimony and likelihood analysis, but this depended on how base‐frequency parameters were estimated and how data were partitioned in likelihood analysis. Relationships inferred for the remaining peristomate and non‐peristomate moss clades, and their associated support values, were otherwise broadly congruent across analyses.     

Systematics of the Pezizomycetes--the operculate discomycetes

The Pezizomycetes (order Pezizales) is an early diverging lineage within the Pezizomycotina. A shared derived character, the operculate ascus, supports the Pezizales as monophyletic, although functional opercula have been lost in certain taxa. Phylogenetic relationships within Pezizales were studied using parsimony and Bayesian analyses of partial SSU and LSU rDNA sequences from 100 taxa representing 82 genera and 13 of the 15 families currently recognized. Three primary lineages are identified that more or less correspond to the A, B and C lineages resolved in previous analyses using SSU rDNA: (A) Ascobolaceae and Pezizaceae; (B) Discinaceae-Morchellaceae and Helvellaceae-Tuberaceae; (C) Ascodesmidaceae, Glaziellaceae, Pyronemataceae, Sarcoscyphaceae and Sarcosomataceae. In contrast the monotypic Rhizinaceae and Caloscyphaceae are resolved as two independent lineages. Bayesian analyses support a relationship among Rhizina and two species of Psilopezia (Pyronemataceae). Only lineage C is highly supported. The B and C lineages form a strongly supported monophyletic group. None of these lineages corresponds to earlier proposed suborders. The A and B lineages are supported by certain morphological features (e.g. ascus bluing reaction in iodine, cytology of spores and paraphyses, septal pore structures and excipulum structure); these characters have been subject to homoplasy. Lineage C is the largest and most heterogeneous, and no unifying morphological features support its recognition. The Pyronemataceae, in which almost half of the species in the order are found, is not monophyletic because the Ascodesmidaceae and Glaziellaceae are nested within it. The relationships among all families in the C lineage remain uncertain. The origin of various forms of ascomata, including hypogeous forms (truffles and truffle-like), epigeous cleistothecia, simple reduced apothecia and highly elaborate, stipitate forms (helvelloid and morchelloid), are discussed.     

Development of eight mitochondrial markers for Funariaceae (Musci) and their amplification success in other mosses

? Premise of the study: In comparison to the wide use of chloroplast markers, few mitochondrial markers are available for phylogenetic studies in bryophytes. We investigated the phylogenetic suitability of several mtDNA markers within the Funariaceae and across mosses. ? Methods and Results: By comparing mitochondrial genomes of two mosses, eight regions with higher substitution rates were identified and sequenced for three species in the Funariaceae and one outgroup taxon. Variations in the substitution rate of these new loci were compared to previously used markers. Thirty-four samples representing all major moss lineages were targeted to assess the universality of the newly designed primers. ? Conclusions: The new markers provided similar or more sequence variations in Funariaceae compared to previously developed mtDNA markers. Five out of eight loci were amplified in 70% of other taxa, indicating that these markers may be suitable for phylogenetic studies in other moss lineages.     

Phylogenetic relationships of major clades of Catostomidae (Teleostei: Cypriniformes) as inferred from mitochondrial SSU and LSU rDNA sequences

Suckers (Family Catostomidae) are holarctic in distribution and include 76 recent species in 14 genera, with 13 genera and 75 species occurring in North and Central America and Siberia. Although this group constitutes a significant component of many aquatic ecosystems, most historic systematic effort has been either alpha- or limited beta-level studies focusing on the two largest tribes within the family, the Catostomini and the Moxostomatini. A recent phylogenetic study based on morphological, biochemical, and early life history characters has advanced current understanding of relationships among catostomid fishes. To further examine phylogenetic relationships among basal lineages of catostomids, we sequenced the entire mitochondrial (mt) SSU and LSU rRNA genes from genera representing all subfamilies and tribes within Catostomidae. Phylogenetic analysis of gene sequences yielded monophyletic Catostomidae, Ictiobinae, and Catostominae and para- or polyphyletic Cycleptinae, with Myxocyprinus as the basal-most taxon and Cycleptus as either the next most-basal taxon or the taxon basal to the Catostominae. Relationships within the Catostominae were generally consistent with those proposed in the above-noted recent phylogenetic study although Thoburnia and Hypentelium were either a clade sister to or a grade group relative to Moxostoma and Scartomyzon. In all trees, Scartomyzon was paraphyletic and embedded within Moxostoma. Phylogenetic affinities of Erimyzon and Minytrema varied depending on data set and character weighting scheme employed. To better reflect phylogenetic relationships resolved in this extensive analysis, we propose the following changes to the classification of catostomids: formation of the new subfamily Myxocyprininae, containing Myxocyprinus from China; restriction of the Cycleptinae to the two species of Cycleptus from North America; restriction of the tribe Moxostomatini to Moxostoma and Scartomyzon; Erimyzon and Minytrema are incertae sedis within Catostominae; and resurrection of the tribe Thoburniini, containing Thoburnia and expanded to include Hypentelium.     

Interferences between Sphagnum and vascular plants: effects on plant community structure and peat formation

The interference between vascular plants and peat mosses with respect to nitrogen and phosphorus was studied in a fertilization experiment and with respect to competition for light in a removal experiment in poor fens with either soligenous or topogenous hydrology using Narthecium ossifragum (L.) Huds. and three species of Sphagnum sect. Sphagnum as targets. Adding fertilizer either on the moss surface or below it confirmed the hypotheses of an asymmetric competition for nutrients, viz. that the Sphagnum mosses relied on the atmospheric supply while Narthecium depended on mineralization in the peat. The results of the removal experiments and the negatively correlated growth of Narthecium and Sphagnum mosses demonstrated a symmetric competition for light. The intensity of the competition for light increased as the availability of N and P increased. The nutrient resources in the total biomass decreased with decreasing standing crop of Narthecium . Only with a considerable amount of mineral nutrients in the biomass has Narthecium the capacity to grow ahead of Sphagnum, because the asymmetric competition for N and P gives Sphagnum the capacity to reduce the performance of vascular plants. The mosses are more efficient in their use of nutrients and produce a decay-resistant litter inducing low mineralization and increasing the peat accumulation rate, and that withdraws N and P from the rhizosphere. The Sphagnum mosses thus act as ecological engineers structuring the plant community and determining the carbon balance of the system. The development of ombrotrophic conditions through peat accumulation seems less probable on soligenous than on topogenous mires owing to the higher mineralization rate there supporting the growth of the vascular plants. Correspondingly, disturbances of the Sphagnum cover, such as through airborne pollutants, increase the productivity of the vascular plants and decrease the capacity for carbon accumulation.     

Phylogeny of the Neotropical cichlid fish tribe Cichlasomatini (Teleostei: Cichlidae) based on morphological and molecular data, with the description of a new genus

Phylogenetic relationships among cichlasomatine cichlids were studied using an extensive taxon sampling and both morphological and molecular data sets. A new genus, Andinoacara n. gen. with six species ( A. pulcher-rivulatus group of previous authors) from trans-andean South America and NW cis-andean South America, is described based on results of phylogenetic and diagnosability analyses and tests of alternative topologies Our results demonstrate that cichlasomatine cichlid diversity is divided into five principal lineages composed of eleven genera and three suprageneric clades: the [( Bujurquina , Tahuantinsuyoa ), ( Andinoacara ) (BAT) clade; the ( Cleithracara , ( Nannacara , Ivanacara )] clade (NIC) plus Laetacara and 'Aequidens' hoehnei ; and the ( Aequidens , Cichlasoma ) clade, where Aequidens is paraphyletic to Cichlasoma . Two former Aequidens species are additionally transferred into Krobia ( K. potaroensis , K. paloemeuensis ). 'Aequidens' hoehnei probably represents a unique evolutionary lineage and would thus qualify for a separate generic status. Molecular data are yet not available for this species and its generic status requires further study. Relationships between the three suprageneric clades and between Acaronia and Krobia could not be convincingly resolved with our data set of two mitochondrial (16S and cyt b ) and two nuclear (S7 and RAG1) molecular markers and 96 morphological characters.     

Molecular phylogeny of the Entomophthoromycota

The Entomophthoromycota is a ubiquitous group of fungi best known as pathogens of a wide variety of economically important insect pests, and other soil invertebrates. This group of fungi also includes a small number of parasites of reptiles, vertebrates (including humans), macromycetes, fern gametophytes, and desmid algae, as well as some saprobic species. Here we report on recent studies to resolve the phylogenetic relationships within the Entomophthoromycota and to reliably place this group among other basal fungal lineages. Bayesian Interference (BI) and Maximum Likelihood (ML) analyses of three genes (nuclear 18S and 28S rDNA, mitochondrial 16S, and the protein-coding RPB2) as well as non-molecular data consistently and unambiguously identify 31 taxa of Entomophthoromycota as a monophyletic group distinct from other Zygomycota and flagellated fungi. Using the constraints of our multi-gene dataset we constructed the most comprehensive rDNA phylogeny yet available for Entomophthoromycota. The taxa studied here belong to five distinct, well-supported lineages. The Basidiobolus clade is the earliest diverging lineage, comprised of saprobe species of Basidiobolus and the undescribed snake parasite Schizangiella serpentis nom. prov. The Conidiobolus lineage is represented by a paraphyletic grade of trophically diverse species that include saprobes, insect pathogens, and facultative human pathogens. Three well supported and exclusively entomopathogenic lineages in the Entomophthoraceae center around the genera Batkoa, Entomophthora and Zoophthora, although several genera within this crown clade are resolved as non-monophyletic. Ancestral state reconstruction suggests that the ancestor of all Entomophthoromycota was morphologically similar to species of Conidiobolus. Analyses using strict, relaxed, and local molecular clock models documented highly variable DNA substitution rates among lineages of Entomophthoromycota. Despite the complications caused by different rates of molecular evolution among lineages, our dating analysis indicates that the Entomophthoromycota originated 405±90million years ago. We suggest that entomopathogenic lineages in Entomophthoraceae probably evolved from saprobic or facultatively pathogenic ancestors during or shortly after the evolutionary radiation of the arthropods.     

Range change evolution of peat mosses (Sphagnum) within and between climate zones

Peat mosses (Sphagnum) hold exceptional importance in the control of global carbon fluxes and climate because of the vast stores of carbon bound up in partially decomposed biomass (peat). This study tests the hypothesis that the early diversification of Sphagnum was in the Northern Hemisphere, with subsequent range expansions to tropical latitudes and the Southern Hemisphere. A phylogenetic analysis of 192 accessions representing the moss class Sphagnopsida based on four plastid loci was conducted in conjunction with biogeographic analyses using BioGeoBEARS to investigate the tempo and mode of geographic range evolution. Analyses support the hypothesis that the major intrageneric clades of peat‐forming species accounting for >90% of peat moss diversity originated and diversified at northern latitudes. The genus underwent multiple range expansions into tropical and Southern Hemisphere regions. Range evolution in peat mosses was most common within latitudinal zones, attesting to the relative difficulty of successfully invading new climate zones. Allopolyploidy in Sphagnum (inferred from microsatellite heterozygosity) does not appear to be biased with regard to geographic region nor intrageneric clade. The inference that Sphagnum diversified in cool‐or cold‐climate regions and repeatedly expanded its range into tropical regions makes the genus an excellent model for studying morphological, physiological, and genomic traits associated with adaptation to warming climates.     

A molecular assessment of phylogenetic relationships and lineage accumulation rates within the family Salamandridae (Amphibia, Caudata)

We examine phylogenetic relationships among salamanders of the family Salamandridae using approximately 2700 bases of new mtDNA sequence data (the tRNALeu, ND1, tRNAIle, tRNAGln, tRNAMet, ND2, tRNATrp, tRNAAla, tRNAAsn, tRNACys, tRNATyr, and COI genes and the origin for light-strand replication) collected from 96 individuals representing 61 of the 66 recognized salamandrid species and outgroups. Phylogenetic analyses using maximum parsimony and Bayesian analysis are performed on the new data alone and combined with previously reported sequences from other parts of the mitochondrial genome. The basal phylogenetic split is a polytomy of lineages ancestral to (1) the Italian newt Salamandrina terdigitata, (2) a strongly supported clade comprising the "true" salamanders (genera Chioglossa, Mertensiella, Lyciasalamandra, and Salamandra), and (3) a strongly supported clade comprising all newts except S. terdigitata. Strongly supported clades within the true salamanders include monophyly of each genus and grouping Chioglossa and Mertensiella as the sister taxon to a clade comprising Lyciasalamandra and Salamandra. Among newts, genera Echinotriton, Pleurodeles, and Tylototriton form a strongly supported clade whose sister taxon comprises the genera Calotriton, Cynops, Euproctus, Neurergus, Notophthalmus, Pachytriton, Paramesotriton, Taricha, and Triturus. Our results strongly support monophyly of all polytypic newt genera except Paramesotriton and Triturus, which appear paraphyletic, and Calotriton, for which only one of the two species is sampled. Other well-supported clades within newts include (1) Asian genera Cynops, Pachytriton, and Paramesotriton, (2) North American genera Notophthalmus and Taricha, (3) the Triturus vulgaris species group, and (4) the Triturus cristatus species group; some additional groupings appear strong in Bayesian but not parsimony analyses. Rates of lineage accumulation through time are evaluated using this nearly comprehensive sampling of salamandrid species-level lineages. Rate of lineage accumulation appears constant throughout salamandrid evolutionary history with no obvious fluctuations associated with origins of morphological or ecological novelties.     

DIVERSITY AMONG TETRASPORALEAN TAXA: EVIDENCE FROM ULTRASTRUCTURE AND MOLECULES

Recent phylogenetic studies of tetrasporalean exemplars using 18S rDNA revealed the extent of diversity among taxa in this non-monophyletic group (Booton et al. 1998). In particular, two distinct tetrasporalean lineages were identified; one group allied with chlamydomonadalean taxa and the other group comprising taxa now placed in a separate order, the Chaetopeltidales. Using these observations as a framework, a new investigation of diversity among a broader sampling of putative tetrasporalean genera (e.g. Asterococcus , Chloranomala , Chlorophysema , Gloeocystis , Gloeodendron , Palmella , Paulschulzia , Physocytium , Schizochlamys and Tetraspora ) was undertaken. Phylogenetic studies of both 18S and 26S rDNA were compared with ultrastructural investigations of vegetative cells. Molecular phylogenetic analyses corroborate the earlier 18S rDNA results, but also reveal additional diversity. The new data raise doubts regarding the monophyly of two genera, Palmella and Tetraspora. The new data also link two enigmatic green algal genera, Physocytium and Heterochlamydomonas , in a long-branch lineage within the Chlamydomonadales. Another enigmatic genus, Schizochlamys , is allied with Bracteacoccus in the Sphaeropleales. Lastly, Chloranomala is resolved as an ally of Paulschulzia , Tetraspora sp., and the green flagellate, Lobomonas. Comparison of pyrenoid ultrastructure generally supports the molecular phylogenetic analyses, suggesting that this non-molecular character will be a useful marker for broad phylogenetic studies of chlamydomonadalean taxa. (Supported by NSF grant, DEB 9726588)