CLOSTERIUM MONILIFERUM-EHRENBERGII (CHAROPHYCEAE, CHLOROPHYTA) SPECIES COMPLEX VIEWED FROM THE 1506 GROUP I INTRON AND ITS2 OF NUCLEAR rDNA

To assess phylogenetic relationships and speciation modes in Closterium , we sequenced two noncoding regions of the nuclear ribosomal cistron, the 1506 group I intron in small subunit and the internal transcribed spacer 2, for a total of 58 strains of the Closterium moniliferum-ehrenbergii species complex. These include both homothallic and heterothallic C. moniliferum Erenberg ex Ralfs v. moniliferum , heterothallic C. moniliferum v. submoniliferum (Woronichin) Krieger, and heterothallic C. ehrenbergii Meneghini ex Ralfs that can be divided into several mating groups. We found no or very little sequence divergence within single mating groups of C. ehrenbergii and among all heterothallic strains of C. moniliferum v. moniliferum or C. moniliferum v. submoniliferum. Nevertheless, sequence divergence was much greater between those mating groups of C. ehrenbergii and also among the three traditional taxa . Maximum parsimony and maximum likelihood analyses showed that the taxon C. ehrenbergii was not monophyletic. The two varieties of C. moniliferum appeared as a sister clade to certain mating groups of C. ehrenbergii . Among the clades that were recovered in different trees by maximum parsimony and maximum likelihood analyses, we consistently found two large conspicuous clades: clade I consisted of mating groups A, B, C, H, K, and L of C. ehrenbergii whose zygospores have smooth-walls, and clade II contained the mating groups D, E, I, J, and S whose zygospores are scrobiculate. Phylogenetic incongruences observed are discussed from the viewpoints of the different molecular nature of the group I intron and internal transcribed spacer 2, as well as putative rapid diversification of the mating groups and probable ancient ancestral hybridization.     

An evaluation of the monophyly of Massarina based on ribosomal DNA sequences

The monophyletic status of the genus Massarina was evaluated on the basis of phylogenetic analysis of the partial small subunit gene (SSU), internal transcribed spacers (ITS 1 & 2), and 5.8S gene sequences of the ribosomal DNA. Species of Massarina used in the study clustered into two distinct clades with high bootstrap support in trees generated from maximum parsimony, weighted parsimony, maximum likelihood, and neighbor-joining analyses. The hypothesis that Massarina species belong to a phylogenetically monophyletic group is rejected. Species with narrowly fusiform ascospores form a monophyletic clade with Lophiostoma, a genus highly similar in morphology. The five species currently accepted in Massarina with such spore morphology are here transferred into the genus Lophiostoma. Massarina species with broadly fusiform to ellipsoidal ascospores are retained as Massarina s. str., lectotypified by M. eburnea. Massarina walkeri is presently excluded from both Massarina and Lophiostoma. The transfer of M. papulosa to a new genus Oletheriostrigula is verified.     

Evidence for host-specific clades of tetraphyllidean tapeworms (Platyhelminthes: Eucestoda) revealed by analysis of 18S ssrDNA

Sequence data from the V4 and V7-V9 variable regions of the 18S small subunit ribosomal DNA (ssrDNA) gene were used to examine relationships among 26 tetraphyllidean and two lecanicephalidean taxa. Newly collected specimens of 21 of the tetraphyllidean species were used to generate ssrDNA sequences that were combined with sequences previously available, including those of two diphyllidean taxa used for outgroup rooting. The sequences were aligned by eye according to secondary structural motifs of the conserved core of the molecule. Of the 1520 sites in the alignment, 874 (58%) were excluded from analysis due to alignment gaps and lack of positional homology as inferred by manual inspection. Genetic variability of the ssrDNA gene regions compared was greater than would be expected, based on the present taxonomy of the ingroup species, and the genetic divergences among tetraphyllidean 'families' and genera were comparable to that among tapeworm orders. Phylogenetic hypotheses were generated by the methods of maximum parsimony and maximum likelihood (GTR + I + Gamma nucleotide substitution model). Four most parsimonious trees resulted from analysis by maximum parsimony. Strict consensus of the four trees supported the monophyly of the Tetraphyllidea, with the lecanicephalidean taxa forming a sister lineage. Among the tetraphyllidean taxa included in the analysis were three major clades: a basal clade including species of the phyllobothriid genera Anthocephalum, Echeneibothrium, Rhinebothrium, Rhodobothrium and Spongiobothrium; a clade uniting the phyllobothriids of the genus Duplicibothrium with the dioecotaeniid genus Dioecotaenia; and a larger sister clade to the Duplicibothrium + Dioecotaenia clade that included the phyllobothriid genera Caulohothrium, Ceratobothrium, Clistobothrium, Paraoryigmatobothrium and Prosobothrium, the litobothriid genus Litobothrium and the onchobothriid genera Acanthobothrium, Calliobothrium, Phoreiobothrium and Platybothrium. Maximum likelihood analysis resulted in a topology that was congruent where nodes were strongly supported by parsimony analysis, but differed in the relative positions of the well-supported clades. In addition,maximum likelihood analysis grouped the lecanicephalidean taxa among the tetraphyllidean taxa, indicating paraphyly of the order Tetraphyllidea as currently defined. Relationships suggested by both methods of analysis reflected common host associations of the taxa better than their current classification, suggesting that coevolution has had a significant role in the evolution of the group.     

Molecular Phylogeny of Conjugating Green Algae (Zygnemophyceae,Streptophyta) Inferred from SSU rDNA Sequence Comparisons

Nuclear-encoded SSU rDNA sequences have been obtained from 64 strains of conjugating green algae (Zygnemophyceae, Streptophyta, Viridiplantae). Molecular phylogenetic analyses of 90 SSU rDNA sequences of Viridiplantae (inciuding 78 from the Zygnemophyceae) were performed using complex evolutionary models and maximum likelihood, distance, and maximum parsimony methods. The significance of the results was tested by bootstrap analyses, deletion of long-branch taxa, relative rate tests, and Kishino-Hasegawa tests with user-defined trees. All results support the monophyly of the class Zygnemophyceae and of the order Desmidiales. The second order, Zygnematales, forms a series of early-branching clades in paraphyletic succession, with the two traditional families Mesotaeniaceae and Zygnemataceae not recovered as lineages. Instead, a long-branch Spirogyra/Sirogonium clade and the later-diverging Netrium and Roya clades represent independent clades. Within the order Desmidiales, the families Gonatozygaceae and Closteriaceae are monophyletic, whereas the Peniaceae (represented only by Penium margaritaceum) and the Desmidiaceae represent a single weakly supported lineage. Within the Desmidiaceae short internal branches and varying rates of sequence evolution among taxa reduce the phylogenetic resolution significantly. The SSU rDNA-based phylogeny is largely congruent with a published analysis of the rbcL phylogeny of the Zygnemophyceae (McCourt et al. 2000) and is also in general agreement with classification schemes based on cell wall ultrastructure. The extended taxon sampling at the subgenus level provides solid evidence that many genera in the Zygnemophyceae are not monophyletic and that the genus concept in the group needs to be revised.     

Phylogenetic analysis of the genus <Emphasis Type="Italic">Petunia</Emphasis> (Solanaceae) based on the sequence of the <Emphasis Type="Italic">Hf1</Emphasis> gene

Polymerase chain reaction fragment length polymorphisms and nucleotide sequences for a cytochrome P450 gene encoding flavonoid-3',5'-hydroxylase, Hf1, were studied in 19 natural taxa of Petunia. Natural Petunia taxa were classified into six groups based on major insertion or deletion events that occurred only in intron II of the locus. The maximum parsimony method was used to calculate strict consensus trees based on nucleotide sequences in selected regions of the Hf1 locus. Petunia taxa were divided into two major clades in the phylogenetic trees. Petunia axillaris (including three subspecies), P. exserta, and P. occidentalis formed a clade with 100% bootstrap support. This clade is associated with a consistently inflexed pedicel, self-compatibility in most taxa, and geographical distribution in southern and western portions of the genus range. The other clade, which comprised the remainder of the genus is, however, less supported (up to 71% bootstrap); it is characterized by a deflexed pedicel in the fruiting state (except P. inflata), self-incompatibility, and a northeastern distribution. A nuclear gene, Hf1, seems to be a useful molecular marker for elucidating the phylogeny of the genus Petunia when compared with the nucleotide sequence of trnK intron of chloroplast DNA.     

Cryptic Speciation in the Genus Cryptoglena (Euglenaceae) Revealed by Nuclear and Plastid SSU and LSU rRNA Gene

The photosynthetic euglenoid genus Cryptoglena is differentiated from other euglenoid genera by having a longitudinal sulcus, one chloroplast, two large trough‐shaped paramylon plates positioned between the chloroplast and pellicle, and lack of metaboly. The genus contains only two species. To understand genetic diversity and taxonomy of Cryptoglena species, we analyzed molecular and morphological data from 25 strains. A combined data set of nuclear SSU and LSU and plastid SSU and LSU rRNA genes was analyzed using Bayesian, maximum likelihood, maximum parsimony, and distance (neighbor joining) methods. Although morphological data of all strains showed no significant species‐specific pattern, molecular data segregated the taxa into five clades, two of which represented previously known species: C. skujae and C. pigra, and three of which were designated as the new species, C. soropigra, C. similis, and C. longisulca. Each species had unique molecular signatures that could be found in the plastid SSU rRNA Helix P23_1 and LSU rRNA H2 domain. The genetic similarity of intraspecies based on nr SSU rDNA ranged from 97.8% to 100% and interspecies ranged from 95.3% to 98.9%. Therefore, we propose three new species based on specific molecular signatures and gene divergence of the nr SSU rDNA sequences.     

Morphological convergence characterizes the evolution of Xanthophyceae (Heterokontophyta): evidence from nuclear SSU rDNA and plastidial rbcL genes

Xanthophyceae are a group of heterokontophyte algae. Few molecular studies have investigated the evolutionary history and phylogenetic relationships of this class. We sequenced the nuclear-encoded SSU rDNA and chloroplast-encoded rbcL genes of several xanthophycean species from different orders, families, and genera. Neither SSU rDNA nor rbcL genes show intraspecific sequence variation and are good diagnostic markers for characterization of problematic species. New sequences, combined with those previously available, were used to create different multiple alignments. Analyses included sequences from 26 species of Xanthophyceae plus three Phaeothamniophyceae and two Phaeophyceae taxa used as outgroups. Phylogenetic analyses were performed according to Bayesian inference, maximum likelihood, and maximum parsimony methods. We explored effects produced on the phylogenetic outcomes by both taxon sampling as well as selected genes. Congruent results were obtained from analyses performed on single gene multiple alignments as well as on a data set including both SSU rDNA and rbcL sequences. Trees obtained in this study show that several currently recognized xanthophycean taxa do not form monophyletic groups. The order Mischococcales is paraphyletic, while Tribonematales and Botrydiales are polyphyletic even if evidence for the second order is not conclusive. Botrydiales and Vaucheriales, both including siphonous taxa, do not form a clade. The families Botrydiopsidaceae, Botryochloridaceae, and Pleurochloridaceae as well as the genera Botrydiopsis and Chlorellidium are polyphyletic. The Centritractaceae and the genus Bumilleriopsis also appear to be polyphyletic but their monophyly cannot be completely rejected with current evidence. Our results support morphological convergence at any taxonomic rank in the evolution of the Xanthophyceae. Finally, our phylogenetic analyses exclude an origin of the Xanthophyceae from a Vaucheria-like ancestor and favor a single early origin of the coccoid cell form.     

Molecular Phylogeny of Conjugating Green Algae (Zygnemophyceae, Streptophyta) Inferred from SSU rDNA Sequence Comparisons

Abstract Nuclear-encoded SSU rDNA sequences have been obtained from 64 strains of conjugating green algae (Zygnemophyceae, Streptophyta, Viridiplantae). Molecular phylogenetic analyses of 90 SSU rDNA sequences of Viridiplantae (inciuding 78 from the Zygnemophyceae) were performed using complex evolutionary models and maximum likelihood, distance, and maximum parsimony methods. The significance of the results was tested by bootstrap analyses, deletion of long-branch taxa, relative rate tests, and Kishino–Hasegawa tests with user-defined trees. All results support the monophyly of the class Zygnemophyceae and of the order Desmidiales. The second order, Zygnematales, forms a series of early-branching clades in paraphyletic succession, with the two traditional families Mesotaeniaceae and Zygnemataceae not recovered as lineages. Instead, a long-branch Spirogyra/Sirogonium clade and the later-diverging Netrium and Roya clades represent independent clades. Within the order Desmidiales, the families Gonatozygaceae and Closteriaceae are monophyletic, whereas the Peniaceae (represented only by Penium margaritaceum) and the Desmidiaceae represent a single weakly supported lineage. Within the Desmidiaceae short internal branches and varying rates of sequence evolution among taxa reduce the phylogenetic resolution significantly. The SSU rDNA-based phylogeny is largely congruent with a published analysis of the rbcL phylogeny of the Zygnemophyceae (McCourt et al. 2000) and is also in general agreement with classification schemes based on cell wall ultrastructure. The extended taxon sampling at the subgenus level provides solid evidence that many genera in the Zygnemophyceae are not monophyletic and that the genus concept in the group needs to be revised.     

A Molecular Study of Euglenoid Phylogeny using Small Subunit rDNA

The euglenoids are an ancient and extremely diverse lineage of eukaryotic flagellates with unclear relationships among taxa. Synapomorphies for the euglenoids include a surface pellicle and a closed mitosis with a series of separate sub-spindles. The taxonomy currently in use is inconsistent with the available data and needs revision. Most euglenoid phylogenies are largely intuitive reconstructions based on a limited number of morphological characters. Therefore, we have added molecular characters from the Small Subunit (SSU) rDNA to generate an overall phylogenetic framework for the euglenoids. SSU rDNA sequences from photosynthetic, osmotrophic, and phagotrophic euglenoids were aligned based on secondary structure. Phylogenetic analysis using the conserved areas of the sequence was performed using parsimony, maximum likelihood, and distance methods. Trees derived using different criteria are in agreement. The euglenoids form a distinct monophyletic clade with phagotrophic members diverging prior to the phototrophic and osmotrophic members. Among photosynthetic members, the biflagellate form diverged prior to the uniflagellate form. Additionally, the genus Euglena appears to be paraphyletic, with osmotrophic taxa, such as Astasia and Khawkinea, diverging independently within the clade containing the photosynthetic genus Euglena.     

Molecular systematics of a speciose, cosmopolitan songbird genus: defining the limits of, and relationships among, the Turdus thrushes

The avian genus Turdus is one of the most speciose and widespread of passerine genera. We investigated phylogenetic relationships within this genus using mitochondrial DNA sequence data from the ND3, ND2 and cytochrome b genes. Our sampling of Turdus included 60 of the 65 extant species currently recognized, as well as all four species from three genera previously shown to fall inside Turdus (Platycichla, Nesocichla, and Cichlherminia). Phylogenetic trees based on maximum likelihood and maximum parsimony algorithms were congruent. Most of the Turdus taxa sampled fall into one of four clades: an African clade, a Central American-Caribbean clade, a largely South American clade, and a Eurasian clade. Still other taxa are placed either at the base of Turdus, or as links between clades. In no instance is any continent reciprocally monophyletic for the species distributed on it. A general lack of nodal support near the base of the phylogeny seems related to a rapid intercontinental establishment of the major clades within Turdus very early in the history of the genus. The monotypic genus Psophocichla is distantly related to, but clearly the sister of, Turdus rather than a constituent member of it.     

Molecular phylogeny of ateline new world monkeys (Platyrrhini, atelinae) based on gamma-globin gene sequences: evidence that brachyteles is the sister group of lagothrix

Nucleotide sequences, each spanning approximately 7 kb of the contiguous gamma1 and gamma2 globin genomic loci, were determined for seven species representing all extant genera (Ateles, Lagothrix, Brachyteles, and Alouatta) of the New World monkey subfamily Atelinae. After aligning these seven ateline sequences with outgroup sequences from several other primate (non-ateline) genera, they were analyzed by maximum parsimony, maximum likelihood, and neighbor-joining algorithms. All three analyzes estimated the same phylogenetic relationships: [Alouatta [Ateles (Brachyteles, Lagothrix)]]. Brachyteles and Lagothrix are sister-groups supported by 100% of bootstrap replications in the parsimony analyses. Ateles joins this clade, followed by the basal genus Alouatta; these joinings were strongly supported, again with 100% bootstrap values. This cladistic pattern for the four ateline genera is congruent with that obtained in previous studies utilizing epsilon-globin, IRBP, and G6PD nuclear genomic sequences as well as mitochondrial COII sequences. Because the number of aligned nucleotide positions is much larger in the present datasetoff than in any of these other datasets, much stronger support was obtained for the cladistic classification that divides subfamily Atelinae into tribes Alouattini (Alouatta) and Atelini, while the latter divides into subtribes Atelina (Ateles) and Brachytelina (Brachyteles and Lagothrix).     

Phylogenetic relationships in Bupleurum (apiaceae) based on nuclear ribosomal DNA its sequence data

BACKGROUND AND AIMS: The genus Bupleurum has long been recognized as a natural group, but its infrageneric classification is controversial and has not yet been studied in the light of sequence data. METHODS: Phylogenetic relationships among 32 species (35 taxa) of the genus Bupleurum were investigated by comparative sequencing of the ITS region of the 18-26S nuclear ribosomal DNA repeat. Exemplar taxa from all currently accepted sections and subsections of the genus were included, along with outgroups from four other early branching Apioideae genera (Anginon, Heteromorpha, Physospermum and Pleurospermum). RESULTS: Phylogenies generated by maximum parsimony, maximum likelihood, and neighbour-joining methods show similar topologies, demonstrating monophyly of Bupleurum and the division of the genus into two major clades. This division is also supported by analysis of the 5.8S coding sequence alone. The first branching clade is formed by all the species of the genus with pinnate-reticulate veined leaves and B. rigidum with a unique type of leaf venation. The other major clade includes the remaining species studied, all of which have more or less parallel-veined leaves. CONCLUSIONS: These phylogenetic results do not agree with any previous classifications of the genus. Molecular data also suggest that the endemic Macaronesian species B. salicifolium is a neoendemic, as the sequence divergence between the populations in Madeira and Canary Islands, and closer mainland relatives in north-west Africa is small. All endemic north-west African taxa are included in a single unresolved but well-supported clade, and the low nucleotide variation of ITS suggests a recent radiation within this group. The only southern hemisphere species, B. mundii (southern Africa), is shown to be a neoendemic, apparently closely related to B. falcatum, a Eurasian species.     

基于线粒体ND1和CO1基因序列探讨锯眼蝶-亚科主要类群的系统发生关系

研究测定了锯眼蝶亚科4族、10属共20个国产代表种的线粒体ND1和COI基因的部分序列,结合从GenBank中获得的4个国外产种类的同源序列,以凤蝶科的迪洛尔娟凤蝶、丝带凤蝶,以及娟蝶科的西猛娟蝶为外类群,通过邻接法、最大简约法、最大似然法和贝叶斯法重建了分子系统树,分析了该亚科及其主要类群的系统发生关系。分析结果表明：帻眼蝶族和锯眼蝶族具有较近的亲缘关系;黛眼蝶族不是单系群,该族中的黛眼蝶属、荫眼蝶属与眉眼蝶族具有较近的亲缘关系,带眼蝶属、藏眼蝶属、毛眼蝶属和帕眼蝶属聚合为一个独立的支系,其中带眼蝶属和藏眼蝶属在所有的分析方法中均以100%的置信度（BP=100%, PP=1.00）相聚合,笔者倾向于将它们合并为一属。     

An examination of the monophyly of morning glory taxa using Bayesian phylogenetic inference

The objective of this study was to obtain a quantitative assessment of the monophyly of morning glory taxa, specifically the genus Ipomoea and the tribe Argyreieae. Previous systematic studies of morning glories intimated the paraphyly of Ipomoea by suggesting that the genera within the tribe Argyreieae are derived from within Ipomoea; however, no quantitative estimates of statistical support were developed to address these questions. We applied a Bayesian analysis to provide quantitative estimates of monophyly in an investigation of morning glory relationships using DNA sequence data. We also explored various approaches for examining convergence of the Markov chain Monte Carlo (MCMC) simulation of the Bayesian analysis by running 18 separate analyses varying in length. We found convergence of the important components of the phylogenetic model (the tree with the maximum posterior probability, branch lengths, the parameter values from the DNA substitution model, and the posterior probabilities for clade support) for these data after one million generations of the MCMC simulations. In the process, we identified a run where the parameter values obtained were often outside the range of values obtained from the other runs, suggesting an aberrant result. In addition, we compared the Bayesian method of phylogenetic analysis to maximum likelihood and maximum parsimony. The results from the Bayesian analysis and the maximum likelihood analysis were similar for topology, branch lengths, and parameters of the DNA substitution model. Topologies also were similar in the comparison between the Bayesian analysis and maximum parsimony, although the posterior probabilities and the bootstrap proportions exhibited some striking differences. In a Bayesian analysis of three data sets (ITS sequences, waxy sequences, and ITS + waxy sequences) no supoort for the monophyly of the genus Ipomoea, or for the tribe Argyreieae, was observed, with the estimate of the probability of the monophyly of these taxa being less than 3.4 x 10(-7).     

Tubeufia asiana, the teleomorph of Aquaphila albicans in the tubeufiaceae, pleosporales, based on cultural and molecular data

The teleomorph of Aquaphila albicans was discovered on submerged wood collected in Thailand. Its black, soft-textured, setose ascomata, bitunicate asci and hyaline to pale brown, multiseptate ascospores indicated an affinity to Tubeufiaceae (Dothideomycetes). After morphological or molecular comparisons with related species in Tubeufia, Acanthostigma and Taphrophila, it is described and illustrated as a new species, T. asiana Sivichai & K.M. Tsui, sp. nov. Finding this Tubeufia teleomorph was surprising, given the falcate conidia of its A. albicans anamorph, which superficially resemble the conidia of Fusarium and not the coiled, helicosporous conidia of other species in Tubeufiaceae. We assessed the phylogenetic relationships of A. albicans-T. asiana with ribosomal sequences from SSU and ITS and partial LSU regions by parsimony and Bayesian analysis. An initial set of 40 taxa representing a wide range of ascomycete families and their SSU sequences from GenBank showed A. albicans-T. asiana to be nested within the Tubeufiaceae with 100% bootstrap support. Their placement was inferred with ITS and partial LSU ribosomal sequences. The nearly identical ITS sequences of two isolates of A. albicans and one isolate of Tubeufia asiana united these fungi as a monophyletic group with 100% bootstrap support and further nested them, with 88% bootstrap support, in a clade containing Helicoon gigantisporum and Helicoma chlamydosporum. This is the first molecular phylogenetic study to place a nonhelicosporous species within the Tubeufiaceae and to show that helical conidia were lost at least once within the family.     

A systematic study of North American Angelica species (Apiaceae) based on nrDNA ITS and cpDNA sequences and fruit morphology

Angelica is a taxonomically complex genus widespread throughout the North Temperate Zone. Previous phylogenetic studies of the genus have focused primarily on its East Asian species. The relationships among its North American members, the monophyly of these species, and the value of fruit morphology in circumscribing its taxa have yet to be examined. This study represents the most comprehensive sampling of Angelica to date (100 species) and includes all 26 species in North America. Relationships are inferred using Bayesian inference, maximum likelihood, and maximum parsimony analyses of ITS sequences and, for multiple accessions of each North American species, cpDNA ndhF-rpl32, rpl32-trnL, and psbM-psbD sequences. The fruit morphological characters examined were those considered phylogenetically important in East Asian Angelica. The results revealed that the North American species fell into three major clades: North American Angelica clade, Archangelica clade, and the Eurasian Angelica clade. Angelica dawsonii has affinities with Lomatium brandegeei. Fourteen species within the North American Angelica clade were strongly supported as monophyletic. Two paraphyletic species resulted in new combinations in A. lineariloba and A. venenosa. Conflict between the ITS-derived and cpDNA-derived phylogenies and the lack of resolution in portions of the trees may be due to chloroplast capture and rapid species radiation. Fruit morphology supported some interspecific relationships based on molecular data, and relationships revealed by ITS and cpDNA data were roughly in accordance with fruit classification type and geographic distribution region, respectively. A diagnostic key based on fruit morphology is provided for the identification of the North American Angelica taxa.     

Phylogeny of eusocial Lasioglossum reveals multiple losses of eusociality within a primitively eusocial clade of bees (Hymenoptera: Halictidae)

We performed a phylogenetic analysis of the species, species groups, and subgenera within the predominantly eusocial lineage of Lasioglossum (the Hemihalictus series) based on three protein coding genes: mitochondrial cytochrome oxidase I, nuclear elongation factor 1alpha and long-wavelength rhodopsin. The entire data set consisted of 3421 aligned nucleotide sites, 854 of which were parsimony informative. Analyses by equal weights parsimony, maximum likelihood, and Bayesian methods yielded good resolution among the 53 taxa/populations, with strong bootstrap support and high posterior probabilities for most nodes. There was no significant incongruence among genes, and parsimony, maximum likelihood, and Bayesian methods yielded congruent results. We mapped social behavior onto the resulting tree for 42 of the taxa/populations to infer the likely history of social evolution within Lasioglossum. Our results indicate that eusociality had a single origin within Lasioglossum. Within the predominantly eusocial clade, however, there have been multiple (six) reversals from eusociality to solitary nesting, social polymorphism, or social parasitism, suggesting that these reversals may be more common in primitively eusocial Hymenoptera than previously anticipated. Our results support the view that eusociality is hard to evolve but easily lost. This conclusion is potentially important for understanding the early evolution of the advanced eusocial insects, such as ants, termites, and corbiculate bees.     

Phylogenetic Analyses of Meloidogyne Small Subunit rDNA

Phylogenies were inferred from nearly complete small subunit (SSU) 18S rDNA sequences of 12 species of Meloidogyne and 4 outgroup taxa (Globodera pallida, Nacobbus abberans, Subanguina radicicola, and Zygotylenchus guevarai). Alignments were generated manually from a secondary structure model, and computationally using ClustalX and Treealign. Trees were constructed using distance, parsimony, and likelihood algorithms in PAUP* 4.0b4a. Obtained tree topologies were stable across algorithms and alignments, supporting 3 clades: clade I = [M. incognita (M. javanica, M. arenaria)]; clade II = M. duytsi and M. maritima in an unresolved trichotomy with (M. hapla, M. microtyla); and clade III = (M. exigua (M. graminicola, M. chitwoodi)). Monophyly of [(clade I, clade II) clade III] was given maximal bootstrap support (mbs). M. artiellia was always a sister taxon to this joint clade, while M. ichinohei was consistently placed with mbs as a basal taxon within the genus. Affinities with the outgroup taxa remain unclear, although G. pallida and S. radicicola were never placed as closest relatives of Meloidogyne. Our results show that SSU sequence data are useful in addressing deeper phylogeny within Meloidogyne, and that both M. ichinohei and M. artiellia are credible outgroups for phylogenetic analysis of speciations among the major species.