生花植物概念简介及其名称的商榷

在上个世纪最后的 2 0年里 ,系统学家应用形态性状对种子植物进行了大量的分支分析。其结果显示灭绝的五柱木属加上灭绝的本内苏铁目及尚存的买麻藤目是被子植物的姊妹群 ,形成一个强支 ,称之为生花植物支。生花植物假说对探讨被子植物起源有着重要影响 ,它激发人们讨论被子植物起源时间可能要提前到三叠纪甚至石炭纪 ,除了支持原有的真花学说外 ,还提出新恩格勒学说。但是 ,近年来对现存种子植物进行分子系统学研究的结果是 :(1)拒绝接受生花植物概念 ;(2 )买麻藤目并不是被子植物的姊妹群而是松柏目的姊妹群 ,甚至网结于松柏类而成为松科的姊妹群。这些结果并不使人惊讶 ,因为对探讨像包含许多灭绝类群的种子植物系统 ,决不可能是仅仅单独应用现代类群资料所能完成的。假如生花植物支是成立的 ,但其名称以AGPB支代替生花植物支可能较为合理。     

Phylogeny of seed plants based on evidence from eight genes

Relationships among the five groups of extant seed plants (cycads, Ginkgo, conifers, Gnetales, and angiosperms) remain uncertain. To explore relationships among groups of extant seed plants further and to attempt to explain the conflict among molecular data sets, we assembled a data set of four plastid (cpDNA) genes (rbcL, atpB, psaA, and psbB), three mitochondrial (mtDNA) genes (mtSSU, coxI, and atpA), and one nuclear gene (18S rDNA) for 19 exemplars representing the five groups of living seed plants. Analyses of the combined eight-gene data set (15?772 base pairs/taxon) with maximum parsimony (MP), maximum likelihood (ML), and Bayesian approaches reveal a gymnosperm clade that is sister to angiosperms. Within the gymnosperms, a conifer clade includes Gnetales as sister to Pinaceae. Cycads and Ginkgo are either successive sisters to this conifer clade (including Gnetales) or a clade that is sister to conifers and Gnetales. All analyses of the mtDNA partition and ML analyses of the nuclear partition yield very similar topologies. However, MP analyses of the combined cpDNA genes place Gnetales as sister to all other seed plants with strong bootstrap support, whereas ML and Bayesian analyses of the cpDNA data set place Gnetales as sister to Pinaceae. Maximum parsimony and ML analyses of first and second codon positions of the cpDNA partiation also place Gnetales as sister to Pinaceae. In contrast, MP analyses of third codon positions place Gnetales as sister to other seed plants, although ML analyses of third codon positions place Gnetales with Pinaceae. Thus, most of the discrepancies in seed plant topologies involve third codon positions of cpDNA genes. The likelihood ratio (LR) and Shimodaira-Hasegasa (SH) tests were applied to the cpDNA data. The preferred topology based on the LR test is that Gnetales are sister to Pseudotsuga. The SH test based on first and second codon and all three codon positions indicated that there is no significant difference between the best topology (Gnetales sister to Pseudotsuga) and Gnetales sister to a conifer clade. However, there is a significant difference between the best topology and topologies in which Gnetales are sister to the rest of the seed plants or Gnetales sister to angiosperms.     

Is the anthophyte hypothesis alive and well? New evidence from the reproductive structures of Bennettitales

Bennettitales is an extinct group of seed plants with reproductive structures that are similar in some respects to both Gnetales and angiosperms, but systematic relationships among the three clades remain controversial. This study summarizes characters of bennettitalean plants and presents new evidence for the structure of cones and seeds that help clarify relationships of Bennettitales to flowering plants, Gnetales, and other potential angiosperm sister groups. Bennettitales have simple mono- or bisporangiate cones. Seeds are borne terminally on sporophylls. They have a unique structure that includes a nucellus with a solid apex, no pollen chamber, and a single integument, and they are clearly not enclosed by a cupule or other specialized structures. Such features differ substantially from Gnetales, flowering plants, and the seed fern Caytonia, providing no compelling evidence for the origin of the angiospermous carpel. Cladistic tests were performed to assess the strength of the "anthophyte hypothesis" and possible relationships of Bennettitales, Gnetales, and Caytonia to flowering plants. Our results do not support the anthophyte hypothesis for the origin of angiosperms by a transformation of fertile organs that were already aggregated into a cone or flower-like structure. However, the anthophyte topology of the seed plant tree continues to be supported by morphological analyses of living and extinct taxa.     

A duplicate gene rooting of seed plants and the phylogenetic position of flowering plants

Flowering plants represent the most significant branch in the tree of land plants, with respect to the number of extant species, their impact on the shaping of modern ecosystems and their economic importance. However, unlike so many persistent phylogenetic problems that have yielded to insights from DNA sequence data, the mystery surrounding the origin of angiosperms has deepened with the advent and advance of molecular systematics. Strong statistical support for competing hypotheses and recent novel trees from molecular data suggest that the accuracy of current molecular trees requires further testing. Analyses of phytochrome amino acids using a duplicate gene-rooting approach yield trees that unite cycads and angiosperms in a clade that is sister to a clade in which Gingko and Cupressophyta are successive sister taxa to gnetophytes plus Pinaceae. Application of a cycads + angiosperms backbone constraint in analyses of a morphological dataset yields better resolved trees than do analyses in which extant gymnosperms are forced to be monophyletic. The results have implications both for our assessment of uncertainty in trees from sequence data and for our use of molecular constraints as a way to integrate insights from morphological and molecular evidence.     

Molecules, Morphology, Fossils, and the Relationship of Angiosperms and Gnetales

Morphological analyses of seed plant phylogeny agree that Gnetales are the closest living relatives of angiosperms, but some studies indicate that both groups are monophyletic, while others indicate that angiosperms are nested within Gnetales. Molecular analyses of several genes agree that both groups are monophyletic, but differ on whether they are related. Conflicts among morphological trees depend on the interpretation of certain characters; when these are analyzed critically, both groups are found to be monophyletic. Conflicts among molecular trees may reflect the rapid Paleozoic radiation of seed plant lines, aggravated by the long branches leading to extant taxa. Trees in which angiosperms are not related to Gnetales conflict more with the stratigraphic record. Even if molecular data resolve the relationships among living seed plant groups, understanding of the origin of angiosperm organs will require integration of fossil taxa, necessarily using morphology.     

Seed plant phylogeny and the origin of angiosperms: An experimental cladistic approach

We present a numerical cladistic (parsimony) analysis of seed plants plus progymnosperms, using characters from all parts of the plant body, outgroup comparison, and a method of character coding that avoids biases for or against alternative morphological theories. The robustness of the results was tested by construction of alternative trees and analysis of subsets of the data. These experiments show that although some clades are strongly supported, they can often be related to each other in very different but nearly equally parsimonious ways, apparently because of extensive homoplasy. Our results support Rothwell’s idea that coniferopsids are derived fromCallistophyton- like platyspermic seed ferns with saccate pollen, but the hypothesis that they evolved fromArchaeopteris- like progymnosperms and the seed arose twice is nearly as parsimonious. Meyen’s division of seed plants into radiospermic and primarily and secondarily platyspermic lines is highly unparsimonious, but his suggestion that ginkgos are related to peltasperms deserves attention. Angiosperms belong among the platyspermic groups, as the sister group of Bennettitales,Pentoxylon, and Gnetales, and this “anthophyte” clade is best related toCaytonia and glossopterids, although relationships with other combinations of Mesozoic seed fern taxa are nearly as parsimonious. These results imply that the angiosperm carpel can be interpreted as a modified pinnate sporophyll bearing anatropous cupules (=bitegmic ovules), while gnetalian strobili are best interpreted as aggregations of highly reduced bennettitalian flowers, as anticipated by Arber and Parkin and Crane. Our most parsimonious trees imply that the angiosperm line (though not necessarily all its modern features) extended back to the Triassic, but a later derivation of angiosperms from some species ofCaytonia or Bennettitales, which would be nearly as parsimonious, should also be considered. These results raise the possibility that many features considered key adaptations in the origin and rise of angiosperms (insectpollinated flowers, rapid reproduction, drought tolerance) were actually inherited from their gymnospermous precursors. The explosive diversification of angiosperms may instead have been a consequence of carpel closure, resulting in increased speciation rates due to potential for stigmatic isolating mechanisms and/or new means of dispersal. DNA sequencing of extant plants and better information on anatomy, chemistry, sporophyll morphology, and embryology of Bennettitales and Caytoniales and the morphological diversity of Mesozoic anthophytes could provide critical tests of relationships.     

Phylogenomics and Coalescent Analyses Resolve Extant Seed Plant Relationships

The extant seed plants include more than 260,000 species that belong to five main lineages: angiosperms, conifers, cycads, Ginkgo, and gnetophytes. Despite tremendous effort using molecular data, phylogenetic relationships among these five lineages remain uncertain. Here, we provide the first broad coalescent-based species tree estimation of seed plants using genome-scale nuclear and plastid data By incorporating 305 nuclear genes and 47 plastid genes from 14 species, we identify that i) extant gymnosperms (i.e., conifers, cycads, Ginkgo, and gnetophytes) are monophyletic, ii) gnetophytes exhibit discordant placements within conifers between their nuclear and plastid genomes, and iii) cycads plus Ginkgo form a clade that is sister to all remaining extant gymnosperms. We additionally observe that the placement of Ginkgo inferred from coalescent analyses is congruent across different nucleotide rate partitions. In contrast, the standard concatenation method produces strongly supported, but incongruent placements of Ginkgo between slow- and fast-evolving sites. Specifically, fast-evolving sites yield relationships in conflict with coalescent analyses. We hypothesize that this incongruence may be related to the way in which concatenation methods treat sites with elevated nucleotide substitution rates. More empirical and simulation investigations are needed to understand this potential weakness of concatenation methods.     

Perspective: the origin of flowering plants and their reproductive biology--a tale of two phylogenies

Recently, two areas of plant phylogeny have developed in ways that could not have been anticipated, even a few years ago. Among extant seed plants, new phylogenetic hypotheses suggest that Gnetales, a group of nonflowering seed plants widely hypothesized to be the closest extant relatives of angiosperms, may be less closely related to angiosperms than was believed. In addition, recent phylogenetic analyses of angiosperms have, for the first time, clearly identified the earliest lineages of flowering plants: Amborella, Nymphaeales, and a clade that includes Illiciales/ Trimeniaceae/Austrobaileyaceae. Together, the new seed plant and angiosperm phylogenetic hypotheses have major implications for interpretation of homology and character evolution associated with the origin and early history of flowering plants. As an example of the complex and often unpredictable interplay of phylogenetic and comparative biology, we analyze the evolution of double fertilization, a process that forms a diploid embryo and a triploid endosperm, the embryo-nourishing tissue unique to flowering plants. We demonstrate how the new phylogenetic hypotheses for seed plants and angiosperms can significantly alter previous interpretations of evolutionary homology and firmly entrenched assumptions about what is synapomorphic of flowering plants. In the case of endosperm, a solution to the century-old question of its potential homology with an embryo or a female gametophyte (the haploid egg-producing generation within the life cycle of a seed plant) remains complex and elusive. Too little is known of the comparative reproductive biology of extant nonflowering seed plants (Gnetales, conifers, cycads, and Ginkgo) to analyze definitively the potential homology of endosperm with antecedent structures. Remarkably, the new angiosperm phylogenies reveal that a second fertilization event to yield a biparental endosperm, long assumed to be an important synapomorphy of flowering plants, cannot be conclusively resolved as ancestral for flowering plants. Although substantive progress has been made in the analysis of phylogenetic relationships of seed plants and angiosperms, these efforts have not been matched by comparable levels of activity in comparative biology. The consequence of inadequate comparative biological information in an age of phylogenetic biology is a severe limitation on the potential to reconstruct key evolutionary historical events.     

The sequence of the largest subunit of RNA polymerase II is a useful marker for inferring seed plant phylogeny

We used RT-PCR to sequence approximately 3 kb of the gene coding for the largest subunit of RNA polymerase II (rpb1) from nine land plants. Our results show that plant rpb1 genes all have a similar GC-content and that their amino acid sequences evolve at a similar rate in most species we examined, except for the Arabidopsis thaliana and rice sequences which evolve faster. This gene also exists as a single copy in most species and contains enough phylogenetically informative sites to resolve the evolutionary relationships among seed plants. Protein maximum parsimony, as well as neighbor-joining and maximum likelihood analyses of DNA and protein sequences, all generated identical tree topologies with similar strong support values at each node. The angiosperms are a clade comprising Amborella as a sister group to all other angiosperms, followed by Nymphaea, Magnolia, Arabidopsis, and a monocot clade containing maize and rice. The gymnosperms also form a monophyletic clade with Welwitschia and pine grouped together and sister to a Cycas and Zamia clade. These findings concur with recent studies that refute the Anthophyte Hypothesis and place Amborella at the base of the angiosperm tree. These rpb1 sequences also give a more consistent picture of seed plant relationships than similar analyses performed on data sets made of 18S rDNA, atpB, and rbcL sequences from the same species. These sequences therefore show great promise to help further resolve the phylogenetic relationships of seed plants.     

轮藻和陆地植物系统发育及其进化

Charophytic algae and land plants together make up a monophyletic group, streptophytes, which represents one of the main lineages of multicellular eukaryotes and has contributed greatly to the change of the environment on earth in the Phanerozoic Eon. Significant progress has been made to understand phylogenetic relationships among members of this group by phylogenetic studies of morphological and molecular data over the last twenty-five years. Mesostigma viride is now regarded as among the earliest diverging unicellular organisms in streptophytes. Characeae are the sister group to land plants. Liverworts represent the first diverging lineage of land plants. Hornworts and lycophytes are extant representatives of bryophytes and vascular plants, respectively, when early land plants changed from gametophyte to sporophyte as the dominant generation in the life cycle. Equisetum, Psilotaceae, and ferns constitute the monophyletic group of monilophytes, which are sister to seed plants. Gnetales are related to conifers, not to angiosperms as previously thought. Amborella, Nymphaeales, Hydatellaceae, Illiciales, Trimeniaceae, and Austrobaileya represent the earliest diverging lineages of extant angiosperms. These phylogenetic results, together with recent progress on elucidating genetic and developmental aspects of the plant life cycle, multicellularity, and gravitropism, will facilitate evolutionary developmental studies of these key traits, which will help us to gain mechanistic understanding on how plants adapted to environmental challenges when they colonized the land during one of the major transitions in evolution of life.     

Error, bias, and long-branch attraction in data for two chloroplast photosystem genes in seed plants

Sequences of two chloroplast photosystem genes, psaA and psbB, together comprising about 3,500 bp, were obtained for all five major groups of extant seed plants and several outgroups among other vascular plants. Strongly supported, but significantly conflicting, phylogenetic signals were obtained in parsimony analyses from partitions of the data into first and second codon positions versus third positions. In the former, both genes agreed on a monophyletic gymnosperms, with Gnetales closely related to certain conifers. In the latter, Gnetales are inferred to be the sister group of all other seed plants, with gymnosperms paraphyletic. None of the data supported the modern "anthophyte hypothesis," which places Gnetales as the sister group of flowering plants. A series of simulation studies were undertaken to examine the error rate for parsimony inference. Three kinds of errors were examined: random error, systematic bias (both properties of finite data sets), and statistical inconsistency owing to long-branch attraction (an asymptotic property). Parsimony reconstructions were extremely biased for third-position data for psbB. Regardless of the true underlying tree, a tree in which Gnetales are sister to all other seed plants was likely to be reconstructed for these data. None of the combinations of genes or partitions permits the anthophyte tree to be reconstructed with high probability. Simulations of progressively larger data sets indicate the existence of long-branch attraction (statistical inconsistency) for third-position psbB data if either the anthophyte tree or the gymnosperm tree is correct. This is also true for the anthophyte tree using either psaA third positions or psbB first and second positions. A factor contributing to bias and inconsistency is extremely short branches at the base of the seed plant radiation, coupled with extremely high rates in Gnetales and nonseed plant outgroups.     

Squamate phylogeny and the relationships of snakes and mosasauroids

Cladistic analysis of extant and fossil squamates (95 characters, 26 taxa) finds the fossil squamate, Coniasaurus Owen, 1850, to be the sister-group of the Mosasauroidea (mosasaurs and aigialosaurs). This clade is supported in all 18 shortest cladograms (464 steps; CI 0.677; HI 0.772) by nine characters of the dermatocranium, maxilla, and mandible. A Strict Consensus Tree of the 18 shortest trees collapses to a basal polytomy for most major squamate clades including the clade (Coniasaurus, Mosasauroidea). A Majority Rule Consensus Tree shows that, in 12 of 18 shortest cladograms, the clade Coniasaurus- Mosasauroidea is the sister-group to snakes (Scolecophidia (Alethinophidia, Dinilysia); this entire clade, referred to as the Pythonomorpha ([[Scolecophidia [Alethinophidia, Dinilysia]], [Coniasaurus, Mosasauroidea]]) is the sister-group to all other scleroglossans. Pythonomorpha is supported in these 12 cladograms by nine characters related to the lower jaw and cranial kinesis. In 6 of 18 shortest cladograms, snakes are the sister-group to the clade (Amphisbaenia (Dibamidae (Gekkonoidea, Eublepharidae))). None of the cladograms support the hypothesis that coniasaurs and mosasauroids are derived varanoid anguimorphs. Two additional analyses were conducted: (1) manipulation and movement of problematic squamate clades while constraining ‘accepted’ relationships; (2) additional cladistic analyses beginning with extant taxa, and sequentially adding fossil taxa. From Test I, at 467 steps, Pythonomorpha can be the sister-group to the Anguimorpha, Scincomorpha, ‘scinco-gekkonomorpha’ [scincomorphs, gekkotans, and amphibaenids-dibamids]. At 471 steps Pythonomorpha can be placed within Varanoidea. Treating only mosasauroids and coniasaurs as a monophyletic group: 469 steps, mosasauroids and coniasaurs as sister-group to Anguimorpha; 479 steps, mosasauroids and coniasaurs nested within Varanoidea. Test II finds snakes to nest within Anguimorpha in a data set of only Mosasauroidea + Extant Squamates; the sistergroup to snakes + anugimorphs is (Amphisbaenia (Dibarnidae (Gekkonoidea, Eublepharidae))). No one particular taxon is identified as a keystone taxon in this analysis, though it appears truc that fossil taxa significantly alter the structure of squamate phylogenetic trees.     

Early Cretaceous mesofossils from Portugal and eastern North America related to the Bennettitales-Erdtmanithecales-Gnetales group

Four new genera and six new species of fossil seed (Buarcospermum tetragonium, Lignierispermum maroneae, Lobospermum glabrum, L. rugosum, L. stampanonii, Rugonella trigonospermum) are described from five Early Cretaceous mesofossil floras from Portugal and eastern North America. The four genera are distinguished by differences in size, shape, and details of seed anatomy, but all are unusual in having an outer seed envelope with a distinctive anatomical structure that surrounds the nucellus and the integument. The integument is extended apically into a long, narrow micropylar tube. The four new genera are part of a diverse, but previously unrecognized, complex of extinct plants that was widespread in Early Cretaceous vegetation and that coexisted in similar habitats with early angiosperms. The distinctive structure of these seeds, and the strong similarities to other fossil seeds (Ephedra, Ephedripites, Erdtmanispermum, Raunsgaardispermum, and some Bennettitales) already known from the Early Cretaceous, suggests that this newly recognized complex of extinct plants, together with Bennettitales, Erdtmanithecales, and Gnetales (the BEG group), is phylogenetically closely related.     

Comments on hexanchiform phylogeny (Pisces, Neoselachii)

The Hexanchiformes (Cow Sharks) are regarded as a monophyletic taxon. Cladistic analysis shows that among the various neoselachian taxa proposed so far as the sister group of the Hexanchiformes a sister group relationship between the Hexanchiformes and a (still unnamed) taxon comprising the Squaliformes and Pristiophoriformes appears as the most probable hypothesis. In addition, MAISEY and WOLFRAM'S (1984) concept of hexanchiform interrelationships is critically reviewed. An alternative cladogram of hexanchiform interrelationships is developed which includes Recent as well as fossil hexanchiform taxa. In this cladogram the living genera Hexancbus and Notorynchus are sister groups and both taxa together form the sister group of the Recent Heptranchias. The fossil taxa +Notidanoides, +“Hexanchus” gracilis, +Notidanodon and +Weltonia are arranged in the stem lineage of recent Hexanchiformes.     

Molecular phylogeny of Laetiporus and other brown rot polypore genera in North America

Phylogenetic relationships were investigated among North American species of Laetiporus, Leptoporus, Phaeolus, Pycnoporellus and Wolfiporia using ITS, nuclear large subunit and mitochondrial small subunit rDNA sequences. Members of these genera have poroid hymenophores, simple septate hyphae and cause brown rots in a variety of substrates. Analyses indicate that Laetiporus and Wolfiporia are not monophyletic. All North American Laetiporus species formed a well supported monophyletic group (the "core Laetiporus clade" or Laetiporus s.s.) with the exception of L. persicinus, which showed little affinity for any genus for which sequence data are available. Based on data from GenBank, the southern hemisphere species L. portentosus also fell well outside the core Laetiporus clade. Wolfiporia dilatohypha was found to represent a sister group to the core Laetiporus clade. Isolates of Phaeolus, Pycnoporellus and members of the core Laetiporus clade all fell within the Antrodia clade of polypores, while Leptoporus mollis and Laetiporus portentosus fell within the phlebioid clade of polypores. Wolfiporia cocos isolates also fell in the Antrodia clade, in contrast to previous studies that placed W. cocos in the core polyporoid clade. ITS analyses resolved eight clades within Laetiporus s.s., three of which might represent undescribed species. A combined analysis using the three DNA regions resolved five major clades within Laetiporus s.s.: a clade containing conifer-inhabiting species ("Conifericola clade"), a clade containing L. cincinnatus ("Cincinnatus clade"), a clade containing L. sulphureus s.s. isolates with yellow pores ("Sulphureus clade I"), a clade containing L. sulphureus s.s. isolates with white pores ("Sulphureus clade II") and a clade containing L. gilbertsonii and unidentified isolates from the Caribbean ("Gilbertsonii clade"). Although there is strong support for groups within the core Laetiporus clade, relationships among these groups remain poorly resolved.     

The evolutionary split of Pinaceae from other conifers: evidence from an intron loss and a multigene phylogeny.

The second intron in the mitochondrial gene nad1 was surveyed using PCR, DNA sequencing, or Southern hybridization in 323 species (313 genera, 212 families) of seed plants. The intron was absent in all 22 species (22 genera, 8 families) of non-Pinaceae conifers studied, in Welwitschia mirabilis, and in seven angiosperms. Whereas absence of the intron in seven angiosperms and Welwitschia is likely due to seven independent losses when evaluated against the recently published multigene phylogenies, the lack of the intron in all non-Pinaceae conifers can be best explained by a single loss. These data suggest that the non-Pinaceae conifers represent a monophyletic group. We also conducted a phylogenetic analysis of seed plants using a combined data set of the partial exon and intron sequences of nad1 generated from this study and published sequences of mitochondrial cox1 and small subunit (SSU) rDNA, chloroplast rbcL, and nuclear 18S rDNA. The results supported the split of conifers into two groups: Pinaceae and non-Pinaceae conifers. The Gnetales were sister to Pinaceae, in agreement with the conclusion from other recent molecular phylogenetic studies that refute the anthophyte hypothesis.     

Phylogeny and patterns of floral diversity in the genus Piper (Piperaceae)

With ～1000 species distributed pantropically, the genus Piper is one of the most diverse lineages among basal angiosperms. To rigorously address the evolution of Piper we use a phylogenetic analysis of sequences of the internal transcribed spacers (ITS) of nuclear ribosomal DNA based on a worldwide sample. Sequences from a total of 51 species of Piper were aligned to yield 257 phylogenetically informative sites. A single unrooted parsimony network suggested that taxa representing major geographic areas could potentially form three monophyletic groups: Asia, the South Pacific, and the Neotropics. The position of Pothomorphe was well supported among groups of New World taxa. Simultaneous phylogenetic analysis of an expanded alignment including outgroups suggested that taxa from the South Pacific and Asia formed a monophyletic group, provisionally supporting a single origin of dioecy. Within the Neotropical sister clade, resolution was high and strong bootstrap support confirmed the monophyly of several traditionally recognized infrageneric groups (e.g., Enckea [including Arctottonia], Ottonia, Radula, Macrostachys). In contrast, some of the species representing the highly polytypic subgroup Steffensia formed a clade corresponding to the previously recognized taxon Schilleria, while others were strongly associated with several of the more specialized groups of taxa. The distribution of putatively derived inflorescence and floral character states suggested that both umbellate and solitary axillary inflorescences have multiple origins. Reduction in anther number appears to be associated with highly packaged inflorescences or with larger anther primordia per flower, trends that are consistent with the suppression of later stages of androecial development.     

A genus-level supertree of Adephaga (Coleoptera)

A supertree for Adephaga was reconstructed based on 43 independent source trees – including cladograms based on Hennigian and numerical cladistic analyses of morphological and molecular data – and on a backbone taxonomy. To overcome problems associated with both the size of the group and the comparative paucity of available information, our analysis was made at the genus level (requiring synonymizing taxa at different levels across the trees) and used Safe Taxonomic Reduction to remove especially poorly known species. The final supertree contained 401 genera, making it the most comprehensive phylogenetic estimate yet published for the group. Interrelationships among the families are well resolved. Gyrinidae constitute the basal sister group, Haliplidae appear as the sister taxon of Geadephaga+Dytiscoidea, Noteridae are the sister group of the remaining Dytiscoidea, Amphizoidae and Aspidytidae are sister groups, and Hygrobiidae forms a clade with Dytiscidae. Resolution within the species-rich Dytiscidae is generally high, but some relations remain unclear. Trachypachidae are the sister group of Carabidae (including Rhysodidae), in contrast to a proposed sister-group relationship between Trachypachidae and Dytiscoidea. Carabidae are only monophyletic with the inclusion of a non-monophyletic Rhysodidae, but resolution within this megadiverse group is generally low. Non-monophyly of Rhysodidae is extremely unlikely from a morphological point of view, and this group remains the greatest enigma in adephagan systematics. Despite the insights gained, our findings highlight that a combined and coordinated effort of morphologists and molecular systematists is still required to expand the phylogenetic database to enable a solid and comprehensive reconstruction of adephagan phylogeny. See also Supplementary material in the online edition at doi:10.1016/j.ode.2006.05.003     

睡莲科的系统发育:核糖体DNA ITS区序列证据

以金鱼藻Ceratophyllum demersum为外类群,使用PAUP4.0b4A软件对睡莲科Nymphaeaceae植物7属11个代表种的ITS区序列进行了系统发育分析。采用最大简约法分析获得了3个最简约树,步长为1125,一致性指数(CI)和维持性指数(RI)值分别为0.7618和0.7214。利用3个最简约树获取严格一致树。结果表明:(1)莲属Nelumbo位于系统树的基部,自展支持率为100%,可从睡莲科中独立出来成立莲科Nelumbonaceae和莲目Nelumbonales;(2)萍蓬草属Nuphar是一单系类群,位于分支Ⅱ的基部,并和睡莲科其他属(不包括莲属)植物聚在一起构成姐妹群,故萍蓬草属仍应置于睡莲科中;(3)水盾草属Cabomba和莼菜属Brasenia聚成一小支并构成姐妹群,自展支持率为99%,说明这两属之间亲缘关系较近;(4)睡莲属和芡实属Euryale、王莲属Victoria聚成一小支并构成姐妹群,自展支持率为94%,说明三者亲缘关系较近,仍应置于睡莲科中。     

Leave it to the leaves: a molecular phylogenetic study of Malaxideae (Epidendroideae, Orchidaceae)

Nuclear ITS and plastid matK sequences were collected for 71 taxa of Malaxideae (Orchidaceae). Resulting cladograms are highly resolved and well supported by jackknife analyses. These indicate that the traditional classification system of the tribe using characters primarily related to floral morphology does not reflect the evolutionary history of these taxa. Rather, the tribe is split into two major clades: one of terrestrial species and another of epiphytes. Within the epiphytic clade, taxa with laterally compressed leaves (Oberonia) are monophyletic, whereas the remaining taxa (Liparis pro parte) have elongate conduplicate leaves and form a paraphyletic grade of at least two additional monophyletic lineages. Within the terrestrial clade, taxa with plicate leaves (Liparis p.p. and Malaxis p.p.) clearly separate from taxa with conduplicate leaves (Liparis p.p. and Malaxis p.p.). Although further taxon sampling should take place before nomenclature is changed, it seems evident that Malaxideae will need to be divided into at least seven genera. Furthermore, the transition from epiphytic to terrestrial habit is documented to have occurred only once in Malaxideae, and the value of vegetative over reproductive features in classifying some groups of orchids is again demonstrated.