Fossil actinomycete filaments and fungal hyphae in dicotyledonous wood from the Eocene London Clay, Isle-of-Sheppey, Kent, England

Two types of filamentous microfossil are preserved within vessel elements and rays of pyritized and partly carbonized twigs from the Lower Eocene London Clay. The first type, probably a Streptomyces -like actinomycete, is slender (<1 µm) with branches and some regular septation. Wider filaments (>2 µm) are fungal hyphae; no reproductive structures are preserved. These filamentous organisms probably started growing saprophytically after the death of the twigs; the fungi created lysis tracks on cell walls. Both are seen to pass through pyrite crystals that fill the lumina of some vessel elements, showing that they are not Recent contaminants.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 383–394.     

Biomechanics and development of rattans: what is special about Plectocomia himalayana Griff. (Calamoideae,Plectocomiinae)?

Mechanical and morphological studies of Plectocomia himalayana (subtribe Plectocomiinae) revealed characteristics that differ strongly from species of subtribe Calaminae ( Calamus and Daemonorops ). In species of Calaminae tested previously, the contribution of the leaf sheath drastically increases stiffness in juvenile axes and towards the apex of older plants. In P. himalayana the relative contribution of the leaf sheath to axis stiffness is less and leaf sheath senescence does not strongly reduce axial stiffness as observed in Calamus and Daemonorops . Natural aerial branching, only described in Korthalsia and Laccosperma among rattans, is common in P. himalayana . Aerial branching and adventitious roots occur frequently along old stems allowing autonomy of stems, following mechanical injury and promoting vegetative propagation. The climbing habit is known to have evolved at least twice within the Calamoideae. The results observed here suggest that climbing habits may differ in detail and that different 'climbing strategies' may have evolved within the subfamily Calamoideae resulting from: (1) variable stem flexibility, (2) the variable mechanical role of the leaf sheath ( Calamus–Daemonorops ) and (3) production of branches and aerial roots conferring a higher degree of architectural plasticity ( Plectocomia ).  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 83–91.     

Plant clonality, mutation, diplontic selection and mutational meltdown

Apomixis is a very common characteristic in vascular plants. It occurs in two general forms: either subversion of the sexual system (agamospermous seeds or apogamous sporophytes in non-seed plants) or vegetative reproduction. In this communication, only the mutational consequences of vegetative reproduction are considered. Vegetative reproduction involves the replication of apical meristems, especially shoot apical meristems. Three general types of shoot apical meristems occur in the vascular plants: single tetrahedral apical initial, unstratified with impermanent initials and stratified with impermanent initials. Each meristem type has different consequences with regard to mutation, diplontic selection and the possibility of mutational meltdown.  © 2003 The Linnean Society of London. Biological Journal of the Linnean Society , 2003, 79 , 61–67.     

Disparity and geometry of the skull in Archosauria (Reptilia: Diapsida)

A metric comparison of 155 fossil and extant species in lateral view based on the proportions of three homologous units (braincase, orbit and rostrum) reveals the existence of an archosaurian skull geometry. An empirical morphospace depicting skull proportions shows that the most variable unit is the rostrum. Three skull types based on rostral proportion are proposed: meso-, longi- and brevirostral. These types depend, on one hand, on a direct numerical relationship between the braincase and the orbit, with a mean ratio of 1:1; never surpassing a 2:1 or 1:2 ratio limit. On the other hand, skull types show a significant negative correlation between braincase and rostrum proportions. Close relationships have been obtained between orbit and the rostrum, although with lower significance and a geometric meaning specific to each group. Skull types depend mainly on the proportional relationship between the rostrum and the braincase. Mesorostral types account for more natural occurrences within morphospace, implying a plesiomorphic condition in Archosauria. Skulls with highest longirostral values (flying forms) display a more restrictive braincase–orbit ratio relationship. Brevirostrals are limited to the smallest skull lengths, up to approximately 180 mm. 85% of brevirostral modern birds have altricial post-hatchling development. General allometric pattern is very similar for all sampled archosaurs, although giant taxa (i.e. non-avian theropods) display a different type of skull proportional growth, closer to isometry. Results reveal the existence of a constructional skull geometry, highlighting the importance of the deviance of the structural design from adaptive explanations on craniofacial morphology in macroevolution.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80, 67–88.     

A phylogenetic analysis of the genera of Lejeuneaceae (Hepaticae)

The Lejeuneaceae are the largest family of the liverworts (Hepaticae), with almost a thousand species in 91 currently accepted genera. We analysed phylogenetic relationships of 69 genera, representing all major subfamilies and tribes recognized in the family, by using 49 informative morphological characters (31 gametophytic, 18 sporophytic), one chemical character, and applying equal and successive weighting of characters and parsimony analysis. In all trees recovered, the Lejeuneaceae were monophyletic with Nipponolejeunea (subfam. Nipponolejeuneoideae) forming the basalmost lineage. The remaining genera clustered in two major groups, the monophyletic Lejeuneoideae (52 genera) and the paraphyletic Ptychanthoideae (16 genera). Within each, several multigeneric lineages corresponding in part to previously described taxa were recovered: the Acrolejeuneinae and Ptychanthinae clades in the Ptychanthoideae, and the Brachiolejeuneinae, Lejeuneeae and Tuyamaella–Cololejeunea clades in the Lejeuneoideae. Bryopteris , a genus sometimes treated as a separate family, was nested in the Ptychanthinae clade. The Tuyamaella–Cololejeunea lineage corresponded with three previously recognized subfamilies (Cololejeuneoideae, Myriocoleoideae and Tuyamaelloideae) and contained genera with neotenic features, in two subclades. These features seemed to have originated by multiple heterochronic events: single origins were detected for 'protonemal neoteny' and 'primary neoteny', whereas 'secondary neoteny' probably evolved twice. Relationships within the large Lejeuneeae clade (43 genera) remained largely unresolved, although several putative lineages were detected in majority rule trees. Additional characters such as DNA sequences may provide better phylogenetic resolution in this group.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 143 , 391–410.     

New chromosome counts in the genus Cousinia and the related genus Schmalhausenia (Asteraceae, Cardueae)

Twenty chromosome counts are reported in the genus Cousinia and the monotypic genus Schmalhausenia , which are part of the Arctium group, from Armenia, Iran, Kazakhstan and Uzbekistan. Twelve are new and eight provide confirmation of scarce or disputable previous data. The correlation between karyological data, pollen type and molecular phylogeny is very close, and on this basis two main groups can be defined. One is the arctioid group, which comprises the genera Arctium and Schmalhausenia , and a small part of the genus Cousinia , with x  = 18. The other is the genus Cousinia s.s. , with a dysploid series ranging from x  = 13–11. Some considerations on the chromosomal evolution in the group are made.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Socety , 2003, 143 , 411–418.     

Morphometric, AFLP and plastid microsatellite variation in populations of Scalesia divisa and S. incisa (Asteraceae) from the Galápagos Islands

Analysis of the stem vasculature of the American climbing palm Desmoncus reveals structural features differing significantly from the Old World rattan genus Calamus . Desmoncus has a more directly continuous vascular system but nevertheless shows a vessel distribution that makes for high hydraulic resistance in the axial xylem. Desmoncus is like Calamus in having a single very wide metaxylem vessel in each central axial bundle and is also without direct vascular contact between protoxylem and metaxylem tracheary elements. However, in Desmoncus the stem vascular bundle system resembles that in tree palms (as has been described in the model palm Rhapis excelsa ) in having a continuing axial bundle that branches from each outgoing leaf trace together with a large number of bridge connections between leaf traces and peripheral axial bundles. Resistance to axial water transport is, however, evident in the narrowness of the continuing metaxylem elements in the peripheral stem vascular region. Desmoncus has scalariform perforation plates with few thickening bars in the metaxylem vessels, unlike the simple perforation plates found in Calamus . Thus, Desmoncus shows only limited convergence in stem vascular architecture toward the extreme modifications found in Calamus . This is not unexpected since it is clear that the climbing habit evolved independently in the two genera.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 142 , 243−254.     

On the systematic status of the desert plated lizard (Angolosaurus skoogi): phylogenetic inference from DNA sequence analysis of the African Gerrhosauridae

The desert plated lizard ( Angolosaurus skoogi ), a 'sand sea' endemic of the northern Namib Desert, exhibits remarkable morphological convergence with other dune-dwelling lizards worldwide. This distinct ecomorphic condition sets Angolosaurus apart from the remaining genera in the family Gerrhosauridae. Indeed, a morphological phylogeny addressing generic relationships within the Cordyliformes (Cordylidae + Gerrhosauridae) identified Angolosaurus as the earliest diverging taxon among African gerrhosaurids. We re-evaluated the basal status of Angolosaurus , conducting a molecular phylogenetic analysis of the African and Madagascan gerrhosaurid genera. Our survey involved a comprehensive species-level comparison among the four nominal genera of mainland Africa ( Angolosaurus , Cordylosaurus , Tetradactylus and Gerrhosaurus ). Mitochondrial DNA sequence data from the cytochrome b , ND2, 12S and 16S rRNA genes were combined for analysis using both parsimony and maximum likelihood procedures. In contrast to the morphological hypothesis, our results do not depict Angolosaurus as the sister taxon to other African gerrhosaurids. Rather, the molecular analyses consistently place Angolosaurus within Gerrhosaurus , rendering the latter genus paraphyletic.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 78 , 253–261.     

Sclerotesta morphology and its systematic implications in magnoliaceous seeds

Seeds of 101 species from 14 genera were observed using stereoscopic and scanning electron microscopy. Sclerotesta morphology is stable within the genera of Magnoliaceae. Two different morphological types are described according to features of the chalazal region, which have great value in classification and have been found only in Magnoliaceae. One is the pore type, characterized by being simple, observed in the relatively primitive taxa of this family, including Manglietia, Pachylarnax, Magnolia (19 species), Aromadendron, Talauma (eight species), Parakmeria (one species), Kmeria (one species), Elmerrillia and Liriodendron . The other one is the tube type, which is characterized by having a more complex structure consisting of a central hollow tube contained within a hole. This type was observed in relatively advanced taxa, including Manglietiastrum, Magnolia (15 species), Talauma (three species), Parakmeria (four species), Kmeria (one species), Alcimandra, Michelia, Paramichelia and Tsoongiodendron . Transitional types between these two were observed in some species of Magnolia . Chalazal region morphology, together with other useful sclerotesta characters, including seed size, shape, the raphal sinus and the external surface of the sclerotesta, may be used as diagnostic characteristics of genera, and even species in Magnoliaceae. A key to identify the different genera is supplied.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 407–424.     

A new species of Scorzonera L. (Asteraceae) from south Anatolia, Turkey

A new species Scorzonera gokcheoglui O. Ünal & R. S. Göktürk sp. nov. from south Anatolia is described and illustrated. Its relationships with S. argyria and S. pisidica are discussed. A map showing the distribution of the species and other related species is given.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 465–468.     

Arbuscular mycorrhizal fungi: genetics of multigenomic, clonal networks and its ecological consequences

Arbuscular mycorrhizal fungi are thought to have remained asexual for 400 million years, although recent studies have suggested that considerable genetic and phenotypic variation could potentially exist in populations. A brief discussion of these multigenomic organisms is presented.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79 , 59–60.     

Two new species from Gabon show the need to reduce Commitheca to the synonymy of Pauridiantha (Rubiaceae, Pauridiantheae)

Two new Pauridiantha species (Pauridiantheae, Rubiaceae) from Gabon are described and illustrated. Pauridiantha pleiantha is characterized by a combination of entirely glabrous stems, stipules with a narrow base, and large inflorescences. Pauridiantha smetsiana is characterized by entirely glabrous stems, narrow, early deciduous stipules, leaves red-tinged when dry, and small inflorescences. The two new species, especially P. smetsiana , close the morphological gap between Commitheca and Pauridiantha in combining typical Commitheca characters, such as glabrous stems and a narrow stipular base, with Pauridiantha characters, such as eucamptodromous venation. A detailed morphological comparison (including ovary structure, seed morphology, exotesta anatomy, and pollen morphology) between the two genera is given; in conclusion, Commitheca is relegated to the synonymy of Pauridiantha . The necessary new specific combinations are provided.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 141 , 105–117.     

Some remarks on the genus Astragalus sect. Incani in Iran

New findings are given for the Astragalus sect. Incani , which occurs within the area covered by the Flora of Iran. Astragalus wojciechowskianus Ranjbar is described as a new species. A. procerus Boiss. & Hausskn . , A. cottonianus Aitch. & Baker, A. achundovii Grossh., A. orduabadensis Grossh. and A. glaucophyllus Bunge are reported as new records for the flora of Iran .   © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 143 , 443–447.     

Genetic changes within an aphid clone: homogenization of rDNA intergenic spacers after insecticide selection

A single asexual maternal lineage (i.e. clone) of the greenbug aphid, Schizaphis graminum (Rondani) was repeatedly selected with the insecticide disulfoton ( O , O -diethyl S- [2-(ethylthio)ethyl] phosphorodioate). A parallel colony of the non-selected clone was also maintained. After approximately 200 generations (4 years) of continuous selection, both the selected and non-selected clones were assayed for changes in intergenic spacer (IGS) length variants of the rRNA cistron. No changes in sets of IGS variants were detected in the non-selected clone. However, the selected clone was found to have lost three variants present in the non-selected clone. This probably occurred by unequal cross-over between sister chromatids, whereby the cistron became homogenized by an increase of frequency of two smaller variants. This documents a large-scale genetic change occurring within the rRNA cistron in a parthenogenetically reproducing aphid.  © 2003 The Linnean Society of London. Biological Journal of the Linnean Society , 2003, 79 , 101–105.     

A new species in the genus Dioon (Zamiaceae) from north-central Oaxaca, Mexico

Dioon argenteum sp. nov. (Zamiaceae) is described from northern Oaxaca, México. Flat leaves, and persistently tomentose, slightly imbricate leaflets with marginal prickles characterize this species. The specific epithet argenteum was chosen to describe the silver appearance of the persistent tomentum covering the new leaves. D. argenteum appears to have affinities with D. purpusii and D. califanoi.   © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 141 , 471–476.     

Chimerism following fusion in a clonal ascidian (Urochordata)

Many marine invertebrates bud vegetatively to produce a modular colony of individuals derived from a single zygote. Fusion of different colonies to produce a genetically composite entity (a chimera) is known from experiments on sponges, hydroids, corals, bryozoans and ascidians – groups which together dominate sessile faunas on marine hard substrates. Random amplified polymorphic DNA–polymerase chain reaction (RAPD–PCR) analysis was applied to individual modules (zooids) dissected from colonies of a colonial ascidian, Diplosoma listerianum (Milne Edwards), to investigate the presence and extent of chimerism. The technique revealed chimerism in wild material. In total, 288 colonies from eight different natural populations were analysed. Chimeric colonies were present in all populations, at frequencies of up to 61%, with up to six different genotypes present in some colonies. Zooids of different genetic origin often intermingled within a chimeric colony to produce a zooidal mosaic. Although fusion of colonies has been observed directly in the laboratory, an unknown proportion of the chimerism detected in wild populations might have arisen through somatic mutation. To assess this possibility, tissue of 12 clones in culture was sampled repeatedly over a period of 3 years and subjected to RAPD–PCR analysis. RAPD banding patterns were generally very stable; the changes noted mostly involved minor bands that would not, on their own, have been taken as evidence for chimerism under the conservative criteria adopted for the study of wild populations. It was concluded that a large proportion of natural chimerism is attributable to colony fusion.  © 2003 The Linnean Society of London. Biological Journal of the Linnean Society , 2003, 79 , 183–192.     

The evolutionary history of the Chydoridae (Crustacea: Cladocera)

Although much is known about the evolutionary history of the pelagic 'cladocerans', there is little information on benthic families such as the Chydoridae. In this study, we examine the phylogenetic history of 37 chydorid species using sequence variation in two mitochondrial genes, COI and 16S rDNA, and one nuclear gene, 18S rDNA. The four recognized subfamilies of chydorids (Eurycercinae, Saycinae, Aloninae and Chydorinae) were well supported, being separated by large sequence divergences of 14.3–16.4%. By contrast, the existing taxonomic system appears to be less clear at a generic level, since many genera (e.g. Alona , Chydorus , Pleuroxus ) consist of an amalgam of distantly related species. However, among those genera which are monophyletic, levels of divergence are very high, suggesting that they originated somewhere in the mid-Palaeozoic. The factors involved in promoting diversification in this group are discussed.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79, 629–643.     

A new late Westphalian fossil marattialean fern from Nova Scotia

Sydneia manleyi gen. et sp. nov. is based on part of a fertile frond from the upper Westphalian D of the Sydney Coalfield, Nova Scotia, Canada. It has small synangia composed of laterally fused sporangia that are elongate and with a circular cross-section. The sporangia yielded variably sized monolete and trilete spores with laevigate and microspinate ornamentation; intermediate forms were also observed. The spores can be correlated with the sporae dispersae species Latosporites minutus , Punctatosporites oculus and Laevigatosporites minimus . Size distribution of the spores is variable and highly skewed, suggesting heterogeneity of the spores within the sporangium. Spore ultrastructure indicates that the fossil is part of a fern, and the morphology of the spores and synangia indicate marattialean affinities.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 199–212.     

A revised classification of subtribe Helianthinae (Asteraceae: Heliantheae). I. Basal lineages

Results for nuclear ITS sequences were combined with previously obtained data from cpDNA restriction site studies to provide a comprehensive molecular phylogeny for subtribe Helianthinae. Results from the two molecular data sets were mostly congruent for basally diverging branches of the subtribe. Based on the results, combined with morphological observations, the basally diverging branches are placed in six genera, including one newly described. Bahiopsis is resurrected to accommodate species previously placed in Viguiera subgenus Bahiopsis . Calanticaria is newly proposed for the five species of Viguiera ser. Brevifolieae . Heliomeris is retained for the group sometimes included within Viguiera as sect. Heliomeris . Hymenostephium is revived and enlarged to include a number of species of similar habit and involucre, including members of Viguiera sect. Diplostichis , Haploca-lymma and Garcilassa . Although cpDNA results place the morphologically distinctive Sclerocarpus within the clade including species of Hymenostephium , the ITS data were consistent with morphology in suggesting it to be a distinctive lineage.  © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 140 , 65–76.     

A morphological phylogeny for four families of amblyceran lice (Phthiraptera: Amblycera: Menoponidae, Boopiidae, Laemobothriidae, Ricinidae)

The suborder Amblycera (Insecta: Phthiraptera) comprises seven recognized families of parasitic lice. Three of these families (the Menoponidae, Laemobothriidae and Ricinidae) are present on a wide range of avian hosts. The four remaining families are restricted to a small section of mammals (the Boopiidae are parasites of Australian and New Guinean marsupials, and the Gyropidae, Trimenoponidae and Abrocomophagidae parasitize South and Central American rodents). This study uses a morphological approach to examine the evolutionary relationships between the genera from four amblyceran families: the Menoponidae, Boopiidae, Laemobothriidae and Ricinidae. Genera are represented by exemplars and a total of 44 louse taxa and one outgroup taxon were included. A cladistic analysis of 147 unordered characters recovered six equally parsimonious trees. Bootstrap, jackknife and Bremer support analyses were undertaken to assess the level of support for each resolved node in the strict consensus topology. Strong support was found for deep branch relationships between the families and in some cases for supra-generic groupings within families. The clades present in the strict consensus tree are discussed with reference to supra-generic and interfamily relationships, character choice, morphological convergence and host distribution. This study is the first phylogeny presented solely for amblyceran genera.  © 2003 The Linnean Society of London, Zoological Journal of the Linnean Society , 2003, 138 , 39–82.