CHARACTER REMOVAL AS A MEANS FOR ASSESSING STABILITY OF CLADES

Abstract— The stability of each clade resolved by a data set can be assessed as the minimum number of characters that, when removed, cause resolution of the clade to be lost; a clade is regarded as having been lost when it does occur in the strict consensus tree. The clade stability index (CSI) is the ratio of this minimum number of characters to the number of informative characters in the data set. The CSI of a clade can range from 0 (absence from the consensus tree of the complete data set) to 1 (all informative characters must be removed for the clade to fail to be resolved). Minimum character removal scores are discoverable by a procedure known as successive character removal, in which separate cladistic analyses are conducted of all possible data sets derived by the removal of individual characters and character combinations of successively increasing number.     

PHYLOGENETIC RELATIONSHIPS IN SEED PLANTS

Abstract— The phylogenetic relationships of nineteen extant and fossil seed plants are considered. Analysis of 31 characters produced ten topologically similar and equally parsimonious cladograms. A strict consensus tree derived from these cladograms places Lyginopteris as the sister taxon to the other seed plants included. Within this clade all the taxa considered, except medullosans and cycads, form a single monophyletic group defined by the presence of flattened seeds and saccate pollen ("platy-sperms"). Relationships between medullosans, cycads, and "platysperms" were not resolved, but within the "platysperm" clade conifers and cordaites ( Cordaixylon, Mesoxylon ) + Ginkgo form a monophyletic group ("coniferophytes"). The "higher platysperms" (glossopterids, Caytonia , corystosperms, Bennettitales, Pentoxylon , Gnetales, and angiosperms) are also monophyletic, but their relationship to "coniferophytes," peltasperms, and Callistophyton is unresolved. Pentoxylon is placed as sister taxon to the Bennettitales, and together they form the sister group to a clade in which Gnetales and angiosperm are sister taxa. The Bennettitales + Pentoxylon + Gnetales + angiosperms ("anthophytes") form a monophyletic sister group to the corystosperms. This analysis is compared with current classifications of seed plants. It does not support a close relationship between Bennettitales and cycads, it provides no evidence for seed plant polyphyly, and it strongly suggests that the current concept of seed ferns has little value in a phylogenetic context.     

Evolutionary relationships of euthyneuran gastropods (Mollusca): a cladistic re-evaluation of morphological characters

Morphological characters of the Euthyneura available from the literature were re-evaluated in terms of terminology and primary homology. A total of 77 characters and 75 taxa were retained in a data matrix. Several assumptions on character weights and types were tested. In the cladistic analyses, it appeared that the data matrix was highly homoplastic, and only robust nodes (those which were little modified by variations in weight and coding of characters) were retained in a concensus tree. The evolutionary histories of all characters and monophylies of higher euthyneuran taxa were discussed. The following interrelationships of the taxa were obtained in a consensus tree: the clade Heterobranchia includes paraphyletic allogastropod taxa which emerge basally, and the clade Euthyneura. The latter includes the clade Pulmonata and at least 10 opisthobranch clades of unresolved relationship (Thecosomata, Gymnosomata, Acochlidioidea, Pyramidelloidea, Runcinoidea, Cephalaspidea, Sacoglossa, Umbraculoidea, Pleurobranchoidea, Nudibranchia). The Pulmonata include basommatophoran paraphyletic taxa and the clade Geophila (Onchidiidae, Soleolifera, Stylommatophora). The position of the Sacoglossa and the monophyly of the Notaspidea are also discussed.  © 2002 The Linnean Society of London, Zoological Journal of the Linnean Society , 2002, 135 , 403–470.     

银杏和苏铁类植物的生殖特征比较

银杏和苏铁类植物是现存种子植物中仅有的2个具多鞭毛游动精子的类群。自1896年Hirase和Ikeno分别发现银杏和苏铁类植物的游动精子以来,研究人员对它们的生活史、胚胎发育、系统演化等已进行了大量研究。本文综述了近年来银杏和苏铁类植物在生殖生物学方面的研究进展,比较了它们生殖特征的异同,并对它们间的亲缘关系进行了初步探讨。通过对一些演化上有重大意义的特征的比较,显示在雄配子体发育及种子发育方面苏铁类植物较银杏保留了更为原始的特征,而在雌配子体发育方面则较银杏更为特化;银杏和苏铁类植物均具有许多特有的结构特征,表明两者在进化过程中是平行发展的,在种系发生上不相关。     

广东省南雄,和平银杏的物候特征及其与气候因子的关系

对广东省南雄、和平两地银杏（ＧｉｎｋｇｏｂｉｌｏｂａＬ．）的物候特征进行了观测和分析,探讨了南雄银杏花期及果实成熟期与气候因子的定量关系。研究表明,影响南雄银杏花期的主要气候因子是当年２月份的平均气温,影响果实成熟期的主要气候因子是花期至成熟期的积温。     

Phylogenetic Analysis of the Hoplolaiminae Inferred from Combined D2 and D3 Expansion Segments of 28S rDNA

DNA sequences of the D2-D3 expansion segments of the 28S gene of ribosomal DNA from 23 taxa of the subfamily Hoplolaiminae were obtained and aligned to infer phylogenetic relationships. The D2 and D3 expansion regions are G-C rich (59.2%), with up to 20.7% genetic divergence between Scutellonema brachyurum and Hoplolaimus concaudajuvencus. Molecular phylogenetic analysis using maximum likelihood and maximum parsimony was conducted using the D2-D3 sequence data. Of 558 characters, 254 characters (45.5%) were variable and 198 characters (35.4%) were parsimony informative. All phylogenetic methods produced a similar topology with two distinct clades: One clade consists of all Hoplolaimus species while the other clade consists of the rest of the studied Hoplolaiminae genera. This result suggests that Hoplolaimus is monophyletic. Another clade consisted of Aorolaimus, Helicotylenchus, Rotylenchus, and Scutellonema species. Phylogenetic analysis using the outgroup species Globodera rostocheinsis suggests that Hoplolaiminae is paraphyletic. In this study, the D2-D3 region had levels of DNA sequence divergence sufficient for phylogenetic analysis and delimiting species of Hoplolaiminae.     

Phylogenetic significance of morphological characters in the tropical Hypotrachyna clade of parmelioid lichens (Parmeliaceae, Ascomycota)

Lichen-forming ascomycetes exhibit often complex morphologies of the vegetative thallus that are usually not found in non-lichenized fungi. This includes the thallus organization and appendical structures associated with the main thallus, such as cilia and rhizines. Such morphological characters are widely employed in the taxonomy of parmelioid lichens, especially at generic level. Within parmelioid lichens, several monophyletic groups can be distinguished, the Hypotrachyna clade being one of them, which includes mostly tropical taxa. In this first molecular study focused specifically on the Hypotrachyna clade, we used maximum parsimony and Bayesian analyses of a combined data set of nuclear ITS and mitochondrial SSU rDNA sequences to (1) test the monophyly of genera presently accepted within the clade and (2) evaluate the phylogenetic value of the morphological characters used to circumscribe genera in parmelioid lichens. Out of the 89 mtSSU and 88 nuITS sequences included in the present study, 121 sequences were newly obtained. Our results show that the taxa within the clade fall into two major groups and that the genus Hypotrachyna is polyphyletic. Everniastrum and Parmelinopsis are nested within Hypotrachyna sensu stricto, the latter being also polyphyletic. Bulbothrix is paraphyletic with Parmelinella nested within and is basal to the second major Hypotrachyna clade. Monophylies of Bulbothrix and Hypotrachyna are significantly rejected. The phylogenetic analysis demonstrates that morphological characters currently used to circumscribe genera in parmelioid lichens, such as cortical anatomy, lobe configuration, cilia, and rhizines have been overestimated and have only minor value in identifying monophyletic groups.     

Molecular phylogeny, character evolution, and biogeography of the grammitid fern genus Lellingeria (Polypodiaceae)

? Premise of the study: The recognition of monophyletic genera for groups that have high levels of homoplastic morphological characters and/or conflicting results obtained by different studies can be difficult. Such is the case in the grammitid ferns, a clade within the Polypodiaceae. In this study, we aim to resolve relationships among four clades of grammitid ferns, which have been previously recovered either as a polytomy or with conflicting topologies, with the goal of circumscribing monophyletic genera. ? Methods: The sampling included 89 specimens representing 61 species, and sequences were obtained for two genes (atpB and rbcL) and four intergenic spacers (atpB-rbcL, rps4-trnS, trnG-trnR, and trnL-trnF), resulting in a matrix of 5091 characters. The combined data set was analyzed using parsimony, likelihood, and Bayesian methods. Ninety-six morphological characters were optimized onto the generated trees, using the parsimony method. ? Key results: Lellingeria is composed of two main clades, the L. myosuroides and the Lellingeria s.s. clades, which together are sister to Melpomene. Sister to all three of these is a clade with two species of the polyphyletic genus Terpsichore. In the L. myosuroides clade, several dispersal events occurred between the neotropics, Africa, and the Pacific Islands, whereas Lellingeria s.s. is restricted to the neotropics, with about 60% of its diversity in the Andes. ? Conclusions: Overall, our results suggest that Lellingeria is monophyletic, with two clades that are easily characterized morphologically and biogeographically. Morphological characters describing the indument are the most important to define the clades within the ingroup. A small clade, previously considered in Terpsichore, should be recognized as a new genus.     

A Contribution to the Embryology of Ginkgo with a Discussion on the Affinity of the Ginkgoales

The ancestry of Ginkgoales or Ginkgophyta can be traced back to the Paleozoic. But today this order is represented only by a single species, Ginkgo biloba. Seward (1838) considered Ginkgo as one of the wonders of the world; it has persisted with little change until the present through a long succession of ages when the earth was inhabited by animals and plants for the most part far removed, in kind as in time, from their living descendents. Ginkgo is generally believed to be native to China, but so far it has not been found in wild state. A number of studies concerning the embryogeny of Ginkgo have been reported, on the basis of the materials accumulated during the past years and supplemented in 1978–1980, the embryogeny of Ginkgo is here described. Finally the phylogeny of Ginkgoales is discussed by comparing with the embryogeny of other groups of the living gymnosperms. Pollination usually takes place from the end of April to the first days of May and fertilization occurs around August 16–20 in the suburbs of Peking. Thus, the interval between pollination and fertilization is a few days less than four months. The embryo of Ginkgo is generally considered as suspensorless. In authors’ opinion, however, the somewhat elongated and much enlarged cells at the micropylar end of the embryo may be considered as the reduced suspensor cells though they are not the typical ones. There is no distinct demarcation between the proembryo and the young embryo in Ginkgo. In comparison with the embryogenesis in Coniferales, the tissue differentiation of the late embryo of Ginkgo is rather indistinct. Many authors such as Chamberlain (1935), Florin (1949), Delevoryas (1963), Sporne (1965) and others divide the gymnosperms into two major groups, Cycadophyta and Coniferophyta. From the point of view of morphological structure there are many significant common features shared by Ginkgoales and Coniferales. For example, Ginkgo possesses long shoot and short shoot while some conifers also have long and short shoots. The anatomical features of the stem of Ginkgo such as the well-developed secondary xylem, relatively small pith and the presence of bordered pits on the tracheids are also similar to those of the Coniferales. Not only Ginkgo has its characteristic leaf shape and the dichotomous venation but also they are quite different from the fronds of cycads. From the reproductive structure, on the other hand, Ginkgo and Cycadales are rather similar: both of them having one sulcate pollen grains, the pollen tube being of haustorial nature, the sperms being released from the base and not from the tip of the pollen tube, the presence of mulficiliate and rather large sperms, development of large female gametophyte bearing archegonia with exceptionally large eggs, more divisions of the free nuclear stage in the proembryo and less distinct differentiation of the ate embryo. All these features are primitive embryological characters. Thus, from the point of view of embryology the Ginkgo is close related to the Cycadales rather than to the Coniferales. Since Ginkgophyta are related to Cycadophyta in reproductive structures on one hand and similar to Coniferophyta in morphological and anatomical characters of the vegetative organs the Ginkgophyta are related to Cycadophyta in reproductive structures on one hand and similar to Coniferophyta in morphological and anatomical characters of the vegetative organs on the other hand, it indicates the interrelationship among these groups is clearly shown. Recently the discovery and studies on the progymnospermopsida (Beck, 1976) are worth notice, this fossil group contains the plants with certain characters of some conifers and certain characters of some cycads and this kind of plants bearing both homosporous and heterosporous forms are similar to ferns. They link the gymnosperms to the ferns. The present evidence, therefore, shows that the gymnosperms are very probably monophyletic and the progymnosperms might be the ancester of all the gymnosperms. The embryological characteristics supports the monophyletic origin of the gymnosperms.     

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.     

Reexamination of the morphological evidence for the cohort Epitheria (Mammalia,Eutheria)

Novacek and co-workers recognized a monophyletic clade Epitheria, comprising all eutherians except edentates and the extinct palaeoryctoids, on the basis of two synapomorphies: a stirrupshaped stapes and a foramen ovale enclosed within the alisphenoid. To evaluate this phylogenetic hypothesis, we reexamined the distributions of stapedial morphologies and positions of the foramen ovale across Recent and extinct mammals and nonmammalian cynodonts. The states and distributions of the stapes and forament ovale characters used by Novacek and coworkers were modified by recognizing two stapedial characters (one relating to shape of the crura, the other to the nature of the foramen) and a single, multistate foramen ovale character (within, behind, and lateral to the alisphenoid). The taxon-character matrix used by Novacek (1989, 1992b), substituting our amended stapedial and foramen ovale characters and adding several previously unscored extinct taxa and three new characters, was subjected to a series of PAUP manipulations. Identified among the most parsimonious trees were three major topologies for the base of Eutheria: (1) a polytomy including an Edentata/Ungulata clade, (2) a polytomy with Edentata and Ungulata as separate clades, and (3) Edentata and (when included) Palaeoryctoidea as the successive outgroups to a monophyletic Epitheria. We conclude that topology 2 best reflects the current state of knowledge. An edentate/ungulate clade is supported by three characters (from the mastoid region and subarcuate fossa); however, other morphological studies require modification of the distributions of these characters in xenarthrans and bassal ungulates, thereby eliminating support for this clade. In nearly all manipulations, obtaining a monophyletic Epitheria required that one or two steps be added to the most parsimonious trees. When a monophyletic Epitheria was obtained, it was supported by a triangular stapes and, in some trees, the reappearance of a stapedial artery (lost earlier at the level of Recent therians) and a transpromontorial internal carotid artery. In the most parsimonious trees, a foramen ovale within the alisphenoid was an equivocal synapomorphy of Recent therians or cutherians, and a stapes with strongly convex crura (our state closest to the stirrup-shaped state of Novacek and co-workers) appeared independently within various eutherian lineages. The reduction or loss of the stapedial foramen was identified as an independent event in monotremes and within marsupials and various eutherian lineages.To whom correspondence should be addressed.     

Genealogical concordance between the mating type locus and seven other nuclear genes supports formal recognition of nine phylogenetically distinct species within the Fusarium graminearum clade

Species limits were investigated within the Fusarium graminearum clade (Fg clade) through phylogenetic analyses of DNA sequences from portions of 11 nuclear genes including the mating-type (MAT) locus. Nine phylogenetically distinct species were resolved within the Fg clade, and they all possess contiguous MAT1-1 and MAT1-2 idiomorphs consistent with a homothallic reproductive mode. In contrast, only one of the two MAT idiomorphs was found in five other species, four of which were putatively asexual, and the other was heterothallic. Molecular evolutionary analyses indicate the MAT genes are under strong purifying selection and that they are functionally constrained, even in species for which a sexual state is unknown. The phylogeny supports a monophyletic and apomorphic origin of homothallism within this clade. Morphological analyses demonstrate that a combination of conidial characters could be used to differentiate three species and three species pairs. Species rank is formally proposed for the eight unnamed species within the Fg clade using fixed nucleotide characters.     

Phylogenetic relationships of North American garter snakes (Thamnophis) based on four mitochondrial genes: how much DNA sequence is enough?

The clade of garter snakes (Thamnophis) includes some of the most abundant and well-studied snakes in North America. However, phylogenetic relationships within this group have been little studied. We used DNA sequences of four mitochondrial genes (cytochrome b and NADH dehydrogenase subunits 1, 2, and 4) to estimate relationships among 29 of the 31 recognized species of Thamnophis plus the related species Adelophis foxi. Both maximum parsimony (MP) and maximum-likelihood (ML) analyses of all these genes combined produced well-resolved trees with moderate (70-89%) to strong (90-100%) bootstrap support for most clades. MP and ML trees were very similar, with no strongly supported conflict between the two analyses. These analyses identify a clade of 12 species largely restricted to México (the "Mexican clade"), and a clade containing 15 species that collectively range from Central America to southern Canada (the "widespread clade"). These two groups are identified as sister taxa in both MP and ML analyses. A clade consisting of the ribbon snakes (T. sauritus and T. proximus) and the common garter snake (T. sirtalis) is placed as the sister group to all other Thamnophis (i.e., the Mexican + widespread clades) in our analyses. High bootstrap proportions at several levels in the tree support the inclusion of both Thamnophis validus, which has traditionally been placed in the genus Nerodia, and the poorly known species Adelophis foxi within Thamnophis. We used randomly sampled characters (i.e., standard bootstrapping) and randomly sampled contiguous blocks of characters to examine the effect of number of characters on resolution of and support for relationships within Thamnophis using MP. In general, these analyses indicate that we have reached a point of strongly diminishing returns with respect to the effect of adding mtDNA sequence characters for the current set of taxa; our sample of 3809 mtDNA characters is apparently "enough." The next steps to improve the phylogenetic estimate may be to add nuclear DNA sequences, morphology, or behavior, or to sequence additional mtDNA lineages within species.     

The Usefulness of the Sting Apparatus in Phylogenetic Reconstructions in Vespids,with Emphasis on the Epiponini: More Support for the Single Origin of Eusociality in the Vespidae

This study aimed at testing the utility of characters derived from chitinous structures of the sting apparatus for elucidating relationships among the genera of Epiponini. The characters were obtained from the spiracular and quadrate plates, gonostylus, and sting. The data matrix was analyzed using parsimony with equal and implied weighting. Sting characters were also optimized on the tree of Wenzel & Carpenter (1994). Consensus of analysis using equal weights parsimony resulted in a tree with low resolution, but the use of implied weighting improved the results and a consensus tree with a better resolution was obtained. Implied weighting analysis showed an interesting result with Vespinae and Epiponini (the taxa that present the highest degree of sociality) together in a clade. The overall uniformity in morphology of sting apparatus and a possible influence of sociality on morphology could explain these results. The evolution of some characters is discussed.     

Soft anatomy, diffuse homoplasy, and the relationships of lizards and snakes

Most previous phylogenetic analyses of squamates (‘lizards’ and snakes) employing large character sets have focused on osteology. Soft anatomical traits bearing on this problem have usually been considered in small subsets. Here, a comprehensive phylogenetic analysis of squamate soft anatomy is attempted. 126 informative characters are assessed for 23 squamate lineages, representing snakes, amphisbaenians, dibamids, and all the traditionally recognized ‘families’ of lizards. The traditionally recognized groupings Iguania, Scleroglossa, Gekkota, Scincomorpha, Anguimorpha and Varanoidea are corroborated in this analysis. More controversial taxa are resolved as follows. Xantusiids, amphisbaenians and dibamids cluster with gekkotans, and snakes are strongly allied with anguimorphs in general, and varanids in particular. Nearly all these clades are congruent with those found in a recent comprehensive osteological analysis; the strong support for snake‐varanid relationships found in both studies is particularly notable. This congruence is surprising given that previous studies of soft anatomy tended to give differing and often heterodox results. These previous results can be attributed to overrepresentation of misleading characters in small isolated data sets. Such misleading signals are minimized when data sets are combined. For instance, the snake‐varanid clade is contradicted by many characters, and analyses of particular organ systems therefore give differing results. However, characters that are incongruent with the snake‐varanid clade also disagree with each other (diffuse homoplasy), rather than forming coherent support for some particular alternative clade (concerted homoplasy). In a combined analysis these incongruent but diffuse characters cancel each other out to leave a very strong (and orthodox) phylogenetic signal. These results underscore the view that the raw amount of homoplasy — as revealed by consistency and retention indices — is not the only determinant of phylogenetic signal; the distribution of that homoplasy is also important. Thus, questioning a phylogenetic hypothesis (e.g. the snake‐varanid clade) by identifying numerous conflicting characters is insufficient — the structure of the conflicting characters should be assessed in a rigorous phylogenetic analysis.     

Higher Level Phylogeny of Curculionidae (Coleoptera: Curculionoidea) based mainly on Larval Characters, with Special Reference to Broad-Nosed Weevils

A cladistic analysis of Curculionidae was performed using 49 characters (41 from larvae, three from pupae, and five from adults). Illustrations of characters of immatures are provided. The analysis involved 19 terminal units and a hypothetical ancestor determined by the outgroup comparison method used to root the tree. One most parsimonious cladogram was obtained based on the complete data set and the following phylogenetic hypothesis is proposed: Ithycerinae, Microcerinae, and Brachycrinae sensu stricto are broad-nosed weevils placed sequentially at the base of the cladogram. The remaining weevil subfamilies form two major natural groups: one constituted by the sister taxa Rhynchophorinae—Platypodinae; the other with Erirhininae at the base, as sister taxon of the "Curculionidae sensu stricto " which show an unresolved trichotomy involving Curculioninae, Cossoninae—Scolytinae, and the clade including the Entiminae and allied subfamilies. This latter clade of broad-nosed weevils has Thecesterninae at the base; the next branch is Amycterinae, the sister taxon of the clade comprising two groups: one constituted by Aterpinae, Rhytirrhininae, and Gonipterinae; the other is Entiminae whose units form two main clades: one constituted by the sister tribes Pachyrhynchini—Ectemnorhinini, and the other by Alophini, Sitonini, and Entimini. When the analysis was done using only immature characters, results congruent with those based on the complete data set were obtained, except for the placement of Erirhininae. According to the results the hypothesis of monophyly of broad-nosed weevils is not accepted; the Entiminae are justified as monophyletic and their natural classification into tribes is proposed and the phylogenetic position and relationships of higher taxa of Curculionidae are discussed. This paper shows the importance of immature characters in recognition of natural groups and relationships in Curculionidae.     

Phylogenetic analysis of Staphyliniformia (Coleoptera) based on characters of larvae and adults

Abstract. One hundred and twenty-one morphological characters of larvae and adults of the series Staphyliniformia were scored (multistate coding) and analysed to determine the family group relationships of the polyphagan groups Scarabaeoidea, Histeroidea, Hydrophiloidea and Staphylinoidea. Cladograms were rooted with exemplars of Adephaga, Archostemata, Myxophaga and the polyphagan families Dascillidae, Derodontidae, Eucinetidae and Scirtidae. Analyses of the same dataset with multistate characters re-coded as presence/absence (144 characters) produced cladograms that were similar to those produced from analyses of the original characters. Cladograms produced from partitioned larval and adult characters differed strongly, with adult-only trees more similar to those produced by combined data. The results confirm the monophyly of Hydrophiloidea + Histeroidea and of Staphylinoidea (including Hydraenidae). The Epimetopidae + Georissidae are the only strongly supported clade within Hydrophiloidea. A clade comprising Hydrochidae, Spercheidae and Hydrophilidae, and a sister-group relationship between the latter two families were confirmed in analyses of the data with presence/absence coding. Helophoridae, Epimetopidae and Georissidae are probably not a monophyletic unit, and additional evidence is needed for a reliable placement of Helophoridae. Scarabaeoidea are placed as a sister taxon of Hydrophiloidea + Histeroidea, but support for this relationship is weak. The branching pattern ((Hydraenidae + Ptiliidae) + (Leiodidae + Agyrtidae)), and a clade comprising Scydmaenidae, Silphidae and Staphylinidae (= ‘staphylinid group’) are well founded. The branching pattern (Orchymontiinae + (Prosthetopinae + (Ochthebiinae + Hydraeninae))) within Hydraenidae is confirmed. Poor resolution at the base of the trees and the placement of some nonstaphyliniform taxa (Dascillidae, Derodontidae, Scirtidae and Eucinetidae) as a sister group to a clade comprising Scarabaeoidea, Hydrophiloidea and Histeroidea suggests that Staphyliniformia may be paraphyletic. It is recommended that series names are eliminated from the classification of Polyphaga, at least for the more ‘primitive’ groups.     

Anatomical and molecular systematics of Asteliaceae and Hypoxidaceae

The astelioid group of asparagoid lilies (Lilianae - Asparagales) comprises Hypoxidaceae, Asteliaceae, Blandfordia and Lanaria. New information is presented on astelioid anatomy, together with a review of other systematic characters. These data are analysed in the context of recent evidence from rbc L nucleotide sequences that astelioids are related to orchids, and that astelioids and orchids (plus Alania and Borya ) form a clade that is sister to all other asparagoid taxa. Hypoxidaceae and Asteliaceae differ from each other in several respects, but there are certain characters linking the two families, notably branched hairs and mucilage canals, unusual characters in Lilianae. Family diagnoses are upheld, but the precise relationships of Blandfordia and Lanaria are still poorly supported within the astelioid clade.     

Convergent evolution and character correlation in burrowing reptiles: towards a resolution of squamate relationships

The affinities of three problematic groups of elongate, burrowing reptiles (amphisbaenians, dibamids and snakes) are reassessed through a phylogenetic analysis of all the major groups of squamates, including the important fossil taxa Sineoamphisbaena, mosasauroids and Pachyrhachis; 230 phylogenetically informative osteological characters were evaluated in 22 taxa. Snakes (including Pachyrhachis) are anguimorphs, being related firstly to large marine mosasauroids, and secondly to monitor lizards (varanids). Scincids and cordylids are not related to lacertiforms as previously thought, but to anguimorphs. Amphisbaenians and dibamids are closely related, and Sineoamphisbaena is the sister group to this clade. The amphisbaenian-dibamid-Sineoamphisbaena clade, in turn, is related to gekkotans and xantusiids. When the fossil taxa are ignored, snakes, amphisbaenians and dibamids form an apparently well-corroborated clade nested within anguimorphs. However, nearly all of the characters supporting this arrangement are correlated with head-first burrowing (miniaturization, cranial consolidation, body elongation, limb reduction), and invariably co-occur in other tetrapods with similar habits. These characters are potentially very misleading because of their sheer number and because they largely represent reductions or losses. It takes very drastic downweighting of these linked characters to alter tree topology: if fossils are excluded from the analysis, a (probably spurious) clade consisting of elongate, fossorial taxa almost always results. These results underscore the importance of including all relevant taxa in phylogenetic analyses. Inferring squamate phylogeny depends critically on the inclusion of certain (fossil) taxa with combinations of character states that demonstrate convergent evolution of the elongate, fossorial ecomorph in amphisbaenians and dibamids, and in snakes. In the all-taxon analysis, the position of snakes within anguimorphs is more strongly-corroborated than the association of amphisbaenians and dibamids with gekkotans. When the critical fossil taxa are deleted, snakes ‘attract’ the amphisbaenian-dibamid clade on the basis of a suite of correlated characters. While snakes remain anchored in anguimorphs, the amphisbaenian-dibamid clade moves away from gekkotans to join them. Regardless of the varying positions of the three elongate burrowing taxa, the interrelationships between the remaining limbed squamates (‘lizards’) are constant; thus, the heterodox affinities of scincids, cordylids, and xantusiids identified in this analysis appear to be robust. Finally, the position of Pachyrhachis as a basal snake rather than (as recently suggested) a derived snake is supported on both phylogenetic and evolutionary grounds.