An origin of aerial branch parasitism in the mistletoe family, Loranthaceae

The large mistletoe family, Loranthaceae, contains 75 genera and approximately 1000 species. The family originated in the Southern Hemisphere and dispersed, apparently early, between fragments of Gondwana. It is now widely distributed on land surfaces of the former supercontinent. The Loranthaceae has three terrestrial, root-parasitic genera-a habit considered ancestral-and 72 genera of aerial, branch parasites. For almost two centuries, the origin of the mistletoe habit has been of interest to biologists. Two main evolutionary pathways have been proposed to explain the transition from terrestrial to aerial parasitism in the family. One theorizes the presence of an intermediate climbing ancestor in the path to the aerial habit. The other proposes a direct transfer from terrestrial to epiphytic growth following the germination of seeds on tree branches. Here we present molecular and morphological evidence that (1) the terrestrial species Nuytsia floribunda is ancestral within the Loranthaceae, (2) aerial parasitism has had multiple origins in the family, (3) the first aerial branch parasites had epicortical roots, and (4) the origin of aerial parasitism in one Old World clade involved the direct transfer from terrestrial to epiphytic growth following the germination of seeds on tree branches. Our results suggest that it is not necessary to evoke a climbing intermediate in the origins of aerial parasitism in the Santalales.     

Comparative morphology of epicortical roots in Old and New World Loranthaceae with reference to root types, origin, patterns of longitudinal extension and potential for clonal growth

The large mistletoe family, Loranthaceae, contains 75 genera, three of which are terrestrial root parasites. The remaining 72 genera are aerial parasites. Four basic haustorial system types are found in aerial genera: epicortical roots (ERs), wood roses, clasping unions and bark strands. The focus of this report is on genera in which ERs are present. Presence of ERs is based on our worldwide collection of haustoria and from literature sources. Our collections include 78% of all aerial genera and 72% of genera with ERs. Collections were analyzed using comparative morphological methods. Of the 72 aerial genera 40 (56%) have ERs and 75% of these are Old World. ERs are the most common haustorial type for Loranthaceae on every major landmass except Africa. Three ER types are described, basal, cauline and adventitious. Basal and adventitious ERs occur in both the Old and New World, whereas cauline ERs are exclusively New World. Adventitious ERs form in a few species in response to injury or epiparasitism. Significant differences occur between basal and cauline ERs in the extent and pattern of elongation, frequency of lateral root formation, and production of haustoria and shoots. Three patterns of axis extension of ERs are recognized, the monochasial sympodium, dichasial sympodium and monopodium. Marked differences in patterns of axis elongation occur between the Old and New World genera analyzed. In Old World taxa 94% of lateral roots contributed to a monochasial sympodium, whereas in New World taxa 84% of root extension was monopodial. Two strategies of resource procurement occur in genera with ERs; the “phalanx” strategy is found in species with basal ERs only, the “guerilla” strategy in New World species with cauline ERs. Species with ERs have the potential for clonal growth through fragmentation of stems, ERs, or both, but the extent of clonal growth in nature is unknown. The large number and wide distribution of genera with ERs add support to the hypothesis that the presence of ERs is an ancestral trait for aerial Loranthaceae.     

Comparative vegetative anatomy and systematics of the angraecoids (Vandeae, Orchidaceae) with an emphasis on the leafless habit

The vegetative anatomy and morphology of 142 species of the angraecoid orchids (Angraecinae + Aerangidinae) and 18 species of Aeridinae were examined using light and scanning electron microscopy. Leafless members of Vandeae were of particular interest because of their unique growth habit. Leafy and leafless members of Angraecinae and Aerangidinae were examined and compared with specimens of Aeridinae. Vandeae were homogeneous in both leaf and root anatomy. A foliar hypodermis and fibre bundles were generally absent. Stegmata with spherical silica bodies were found associated with sclerenchyma and restricted to leaves in almost all specimens examined. Distinct inner tangential wall thickenings of the endovelamen occurred in several vandaceous genera. Exodermal proliferations and aeration units commonly occurred in both leafy and leafless Vandeae. Cladistic analyses of Angraecinae and Aerangidinae with members of Aeridinae and Polystachyinae as outgroups using 26 structural characters resulted in 20 000+ equally parsimonious trees. Vandeae formed the only well-supported clade in bootstrap analyses and were characterized by having a monopodial growth habit, spherical stegmata, loss of mucilage, and loss of tilosomes.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 165–218.     

Evolution of epiphytes in Davalliaceae and related ferns

The evolution of epiphytes in Davalliaceae was investigated by field observations and molecular phylogenetic analyses. Field studies revealed that in Davalliaceae and related ferns, epiphytes in a broad sense are classified into climber, secondary hemi-epiphyte, and obligate epiphyte, based on combinations of the places (ground vs. tree) of inferred spore germination and sporophyte growth. Some species of Davalliaceae have multiple life forms, i.e. secondary hemi-epiphyte and obligate epiphyte, whereas others are obligate epiphytes. Phylogenetic trees obtained from rbcL and accD gene sequences supported that secondary hemi-epiphytic Oleandra is sister to the epiphytic Davalliaceae and polygrammoid ferns. Analyses of life form evolution based on the phylogenetic relationships suggested that obligate epiphytes of the Davalliaceae and polygrammoid ferns evolved from secondary hemi-epiphytes, or less likely from climbers. We hypothesized a scenario for the evolution of life forms in Davalliaceae and related groups that involves successive changes in rhizome habit, root function, and germination place. Rhizome dorsiventrality and scale morphology, shared by climbers, secondary hemi-epiphytes, and obligate epiphytes examined, may be other innovations for the ferns to have evolved into epiphytes.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 495–510.     

An unusual case of epigeal cryptocotylar germination in Rollinia salicifolia (Annonaceae)

An unusual case of epigeal cryptocotylar germination found in Rollinia salicifolia Schltdl. (Annonaceae) is described and is discussed in relation to the terminology used for germination studies. The terms cryptocotylar and phanerocotylar are used to describe the permanence of cotyledons within the seed coat or endocarp; the terms epigeal and hypogeal are used to refer the position of cotyledons in relation to ground level. The terms to describe position about ground level and permanence of cotyledons within the seed coat or endocarp are not used simultaneously in many papers, and some authors consider the terms cryptocotylar and hypogeal to be synonyms. Cases of epigeal cryptocotylar germination seem to be scarce in the literature. The morphological characters shown by R. salicifolia seeds and seedlings − a non-chlorophyllous embryo, abundant endosperm, thick woody seed coat, thickened hypocotyl and non-photosynthetic haustorial cotyledons − are closely related to its epigeal cryptocotylar germination. This is the first record of this type of germination in Argentina.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 53–56.     

A new divergent lineage of Daphnia (Cladocera: Anomopoda) and its morphological and genetical differentiation from Daphnia curvirostris Eylmann, 1887

The systematic biology of the subgenus Daphnia s . s . remains confused. Prior attempts at resolution used chiefly postabdominal claw morphology, chromosome numbers and rRNA gene sequences as characters for higher-level relations. Still, several taxa, such as Daphnia curvirostris Eylmann, 1878, have unclear affiliations. We addressed the position of D. curvirostris in this genus by estimating phylogenetic trees from a rapidly evolving protein coding gene (ND2), conducting broad geographical comparisons and carrying out detailed morphological comparisons. The Japanese ' curvirostris' was found to be a new divergent lineage in the subgenus Daphnia , and to possess distinctive morphological characteristics from D. curvirostris . We described this new species as Daphnia tanakai sp. nov. , and redescribed D. curvirostris . The polymorphic postabdominal claw morphology and the distinctive chromosome number of D. tanakai sp. nov. provided evidence for rapid evolution of these traits. Our new morphological, chromosomal and genetic assessment of Daphnia weakened the argument for division of the subgenus Daphnia ( Daphnia ) O. F. Müller, 1785 sensu Johnson, 1952, into two further subgenera.  © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society , 2006, 146 , 385–405.     

The green-veined white (Pieris napi L.), its Pierine relatives, and the systematics dilemmas of divergent character sets (Lepidoptera, Pieridae)

The butterfly Pieris napi (L.) and relatives exemplify recently evolving taxa, exhibiting variation that makes their evolutionary dynamics interesting, but their systematics difficult. Wing-pattern characters commonly used to distinguish these Holarctic insects display both genetic polymorphism and environmentally-cued polyphenism. Often, these causes of variation are confounded, impairing the characters' phylogenetic usefulness. DNA sequences of four mitochondrial genes offer an independent view of pierine phylogeny. Sampling diverse relatives within family Pieridae assists resolution of the P. napi complex, suggests previous underestimation of clade diversity in subfamily Pierinae, and shows that other genera near Pieris also display confusions of wing-pattern-based phylogenetic inference. The European P. napi is sister to all North American taxa, and is well diverged from them all in sequences. The North American taxa comprise a northern subclade including Pieris oleracea , and questionably distinct Pieris ' angelika ', and a southern subclade including distinct Pieris virginiensis , Pieris marginalis , and Pieris macdunnoughii , and other regional entities yet to be clarified. Weak bootstrap support for some nodes in this group arises from a closeness of sequence identity rather than character conflict; more sequence data and denser geographical sampling may resolve these nodes more clearly. Evidence of reproductive isolation, from other experimental hybridization studies, agrees with the DNA results where these conflict with other divergent character sets. The system offers much promise for a deeper understanding of character evolution in relation to phyletic differentiation.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 413–435.     

Chromosomes of four species in three genera of Commelinaceae from China and their systematic implications

Chromosomes of four species in three genera of Commelinaceae from China were examined. Spatholirion longifolium had 2 n  = 20. This small genus is considered to be of a possible polyploid origin based on x  = 5, a basic number shared by its closest ally, the monospecific genus Streptolirion , with its only species having 2 n  = 10. The two genera were found to be very different from each other in their karyotypic constitution. The differences in both chromosome number (2 n  = 20 vs. 10) and karyotypic constitution support their separation as two independent genera. The remaining three species, Amischotolype hispida , Porandra ramosa and P. scandens , all had 2 n  = 36. In view of the occasional occurrence of 2 n  = 18 in the African Coleotrype , a genus very close to Amischotolype and Porandra in gross morphology, these three species are all very probably polyploid based on x  = 9. The high degree of karyotypic similarity of the three genera also strongly indicates their close affinity and supports their placement in the subtribe Coleotrypinae. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 152 , 399–403.     

Comparative morphology of the leaf epidermis in Schisandra (Schisandraceae)

The leaf epidermis of 127 samples representing ten species within Schisandra Michaux. and one species of the related genus, Kadsura Kaempf. ex Juss., was investigated using light and scanning electron microscopy. Many characters of the leaf epidermis in Schisandra , such as pattern of epidermal cells, type of stomata, shape of guard cell pairs and cuticular ornamentation, are usually constant within species and thus make good characters for studying the relationship between and within genera. A new character, rim number, of the outer stomatal rim in the genus is introduced. It is shown that double outer stomatal rims occur only in evergreen Schisandra species, whereas a single rim occurs in deciduous species. This character supports the classification of Schisandra into two subgenera based on habit and androecial organs. This classification is also supported by additional morphological and molecular taxonomic characters. Kadsura coccinea (Lem.) Smith A. C. is the most primitive taxon in the related genus Kadsura . The outer stomatal rim of this species also has double rims. Combined with morphological and molecular evidence, this suggests that Schisandra and Kadsura are closely related and may share a recent common ancestor.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 39–56.     

Two new South American species of Struthanthus (Loranthaceae) posing a challenge to circumscription of neotropical genera

Two new, closely related species of Struthanthus (Loranthaceae) are described, S. meridionalis from southern Bolivia and S. prancei from northern Brazil, each showing significant deviations from the generic norm in their inflorescence morphology. In both cases, a very high proportion of inflorescences bear bracteolate and/or ebracteolate monads as lateral units rather than the triads which characterize the rest of the genus. The place of inflorescence morphology in the development of generic concepts in small-flowered neotropical Loranthaceae is briefly reviewed, leaving the two new species in Struthanthus for the time being.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 469–474.     

Chromosome studies in Hippeastrum (Amaryllidaceae): variation in genome size

This paper presents the karyotype and DNA content of 12 diploid species of Hippeastrum from South America. The variation in genome size is compared with the karyotype and DNA content of Amaryllis belladonna from South Africa. The Hippeastrum species present a uniform and bimodal basic karyotype formula, but significant differences are found in the total chromosome volume (TCV) and nuclear DNA content. A positive correlation between the DNA content and TCV is also observed. The karyotype's constancy is a product of changes in DNA content occurring in the whole chromosome complement. The DNA addition to the long and short sets of chromosomes varies independently. In species with higher DNA contents, the short chromosomes add equal DNA amounts to both arms, maintaining their metacentric morphology, whereas the long chromosomes add DNA only to the short arm, increasing the chromosome symmetry. These data show that the evolutionary changes in DNA amount are proportional to chromosome length, maintaining the karyotypic uniformity. A. belladonna has a larger DNA content and possesses a karyotype different from that of Hippeastrum spp., supporting the distinction between the two genera and upholding the name Amaryllis for the South African entity against Hippeastrum for the South American genus.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 155 , 171–178.     

Ecological diversification and phylogeny of emydid turtles

Ecological diversification is a central topic in ecology and evolutionary biology. We undertook the first comprehensive species-level phylogenetic analysis of Emydidae (an ecologically diverse group of turtles), and used the resulting phylogeny to test four general hypotheses about ecological diversification. Phylogenetic analyses were based on data from morphology (237 parsimony-informative characters) and mitochondrial DNA sequences (547 parsimony-informative characters) and included 39 of the 40 currently recognized emydid species. Combined analyses of all data provide a well-supported hypothesis for intergeneric relationships, and support monophyly of the two subfamilies (Emydinae and Deirochelyinae) and most genera (with the notable exception of Clemmys and Trachemys ). Habitat and diet were mapped onto the combined-data tree to test fundamental hypotheses about ecological diversification. Using continuous coding of ecological characters showed that lineages changed in habitat before diet, ecological change was most frequently from generalist to specialist, and habitat and diet rarely changed on the same branch of the phylogeny. However, we also demonstrate that the results of ancestral trait reconstructions can be highly sensitive to character coding method (i.e. continuous vs. discrete). Finally, we propose a simple model to describe the pattern of ecological diversification in emydid turtles and other lineages, which may reconcile the (seemingly) conflicting conclusions of our study and two recent reviews of ecological diversification.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79, 577–610.     

Karyological evolution in Rhaponticum Vaill. (Asteraceae, Cardueae) and related genera

Chromosome counts are reported in 29 populations representing 20 species and one subspecies of the genera Callicephalus (one sp.), Klasea (seven spp.), Myopordon (two spp.), Oligochaeta (one sp.), and Rhaponticum (nine spp., one ssp.). Eleven reports are new, the others supplement limited previous data. New and published cytological data are summarized and evaluated critically in light of current taxonomic treatments and evolutionary hypotheses. Basic chromosome numbers are a valuable source of taxonomic information and relate well to the phylogeny. They are quite conserved in Klasea (only x  = 15), the sister group of the remaining genera, and in the early branching genera of the Rhaponticum group ( x  = 14 for Centaurothamnus and Callicephalus ). However, a more complex pattern of genome evolution is present among the more derived clades, Oligochaeta plus Myopordon ( x  = 12, 14) and the genus Rhaponticum ( x  = 12, 13). The occurrence of x  = 12 in Oligochaeta divaricata and Rhaponticum carthamoides seems to be the result of a recent event of chromosome fusion, as suggested by the fragility of particularly long pairs of chromosomes. The use of chromomycin staining, including an enzymatic digestion step that facilitates spreading and permits a reduction of potential fragmentation, only partially resolves this problem.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 153 , 193–201.     

Cytotaxonomy of Lychnophoriopsis Sch.Bip. and Paralychnophora MacLeish species (Asteraceae: Vernonieae: Lychnophorinae)

The genera Lychnophoriopsis and Paralychnophora are endemic to Brazilian 'campo rupestre' in the States of Minas Gerais and Bahia. To analyse the status of the cytotaxonomy of these genera, we carried out chromosome counts on several species. Two chromosome numbers were obtained for four species of Paralychnophora : 2 n  = 36 and 2 n  = 38. For three species of Lychnophoriopsis , only 2 n  = 36 was observed. The chromosome size (1.0–2.58 µm) and morphology (mainly metacentric, with some submetacentric) were analysed in four species of Paralychnophora and showed relative constancy .   © 2007 The Linnean Society of London. Botanical Journal of the Linnean Society , 2007, 154 , 109–114.     

Pollen morphology of the Swertiinae (Gentianaceae): phylogenetic implications

Recent molecular surveys of the Swertiinae (Gentianaceae–Gentianeae) revealed unexpected phylogenetic relationships, including polyphyly of the genera Gentianella , Jaeschkea , Lomatogonium and Swertia . To find new non-molecular characters supporting the phylogeny, we examined the exine variation of 73 species of all major lineages of subtribe Swertiinae using environmental scanning electron miscroscopy supplementing older, mainly light microscopical, studies. In contrast to previous studies, we were able to pick out taxa from phylogenetic key positions with particular focus on Swertia . Many distantly related taxa such as parts of Frasera , Gentianopsis , Halenia , Gentianella , Megacodon and several lineages of Swertia share a striate–reticulate or reticulate exine pattern. This is interpreted as the plesiomorphic character state of Swertiinae. There is also considerable variation of derived patterns; for example, different types of microechinate or almost smooth pollen was repeatedly observed in distantly related groups. Another extreme was the ring-shaped reticulation found in a North American species of Gentianopsis . Unfortunately, major relationships as revealed by molecular analyses were rarely supported because of the abundance of the plesiomorphic type and homoplasy even on low taxonomic levels; for example, within Lomatogonium . Exine variation was particularly useful in characterizing independent lineages of Swertia . For example, according to pollen characters and in agreement with other data, the Asian Swertia cuneata is a sister group of a strongly diversified African lineage and Swertia yunnanensis , which is rather aberrant in flower morphology, seems close to parts of Lomatogonium .  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 323–341.     

Evolution of micromorphological and chemical characters in the lichen-forming fungal family Pertusariaceae

Micromorphological characters of the fruiting bodies, such as ascus-type and hymenial amyloidity, and secondary chemistry have been widely employed as key characters in Ascomycota classification. However, the evolution of these characters has yet not been studied using molecular phylogenies. We have used a combined Bayesian and maximum likelihood based approach to trace character evolution on a tree inferred from a combined analysis of nuclear and mitochondrial ribosomal DNA sequences. The maximum likelihood aspect overcomes simplifications inherent in maximum parsimony methods, whereas the Markov chain Monte Carlo aspect renders results independent of any particular phylogenetic tree. The results indicate that the evolution of the two chemical characters is quite different, being stable once developed for the medullary lecanoric acid, whereas the cortical chlorinated xanthones appear to have been lost several times. The current ascus-types and the amyloidity of the hymenial gel in Pertusariaceae appear to have been developed within the family. The basal ascus-type of pertusarialean fungi remains unknown.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 615–626.     

Morphological perspective on the classification and evolution of Recent Pterioidea (Mollusca: Bivalvia)

The evolutionary relationships of the Recent Pterioidea are inferred from a phylogenetic analysis of representatives of all pterioidean genera based on original observations of anatomy and shell morphology, and an extensive survey of bivalve literature. The well-resolved cladogram supports monophyly for the superfamily, but renders all but one family (the monotypic Pulvinitidae) polyphyletic. In addition, these results reveal a considerable level of convergence and parallelisms through the Pterioidea. The branching order of pterioid genera in the morphological analysis is largely corroborated by the sequence of their appearance in the fossil record. The palaeontological evidence provides important information on dating lineage splitting events and transitional taxa. The proposed phylogeny integrates the cladistic analysis of the Recent Pterioidea with the fossil record and suggests that the crown-group pterioideans probably originated in the Triassic from the Bakevelliidae, an extinct paraphyletic stem group from which the Ostreoidea are also ultimately derived.  © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society , 2006, 148 , 253–312.     

Karyological studies in Tripleurospermum (Asteraceae, Anthemideae) from north-east Anatolia

Chromosome number and morphology in 14 taxa belonging to 19 populations of Tripleurospermum Sch. Bip. were studied using karyological and numerical taxonomical techniques. Data on chromosome measurements were analysed using cluster analysis. Chromosome numbers of these taxa are 2 n  = 2 x  = 18, 4 x  = 36 and 5 x  = 42–48. Seven records are new, two are not consistent with previous counts, and the remainder confirm the very limited previous data (one to three records). A new ploidy level (pentaploidy) is reported for the first time for the genus. Some correlations between ploidy levels and morphological characters are noted and several systematic and evolutionary aspects of the genus are discussed in the light of karyological data.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 146 , 427–438.