bluuebunny/crossref_metadata_2025 huggingface dataset:
Fertility of Vriesea gigantea Gaud. (Bromeliaceae) in southern Brazil
Authors: Paggi Gecele M. , Palma‐Silva Clarisse , Silveira Lucas C. T. , Kaltchuk‐Santos Eliane , Bodanese‐Zanettini Maria H. , Bered Fernanda
Published: February 2008

Plant fertility is a central subject of many questions in plant evolutionary and conservation biology. Pollen availability, abiotic resources, and flowering pattern can limit fruit and seed production. Open pollination and pollen supplementation studies are used to estimate any pollen limitation in natural populations. To study the impact of these factors on the reproductive success of Vriesea gigantea, an epiphytic bromeliad in the Atlantic Rainforest in Brazil, its fertility in four natural populations in Itapuã State Park was assessed by considering plant and inflorescence size, flower production, fruit and seed set, flower and fruit set pattern, and seed viability and germination rate. Supplemental pollination in adult plants was used to determine whether fruit production in V. gigantea is limited by reception of pollen. The results showed that V. gigantea has a high production of flowers, fruits, and seeds. Seeds are highly viable in all populations, presenting an average germination rate of 94% (SE ± 3.5). Plants of V. gigantea from Itapuã State Park are highly fertile. The high proportion of fruit and seed set after manual hand pollination indicates that the species is self‐compatible. Pollination treatments showed evidence of pollinator limitation in the Itapuã State Park population.
Floral organogenesis and floral evolution of the Lecythidoideae (Lecythidaceae)
Authors: Tsou Chih‐Hua , Mori Scott A.
Published: February 2008

The subfamily Lecythidoideae of Lecythidaceae (Brazil nut family) is a dominant group in neotropical forests, especially those of Amazonia. New World members of the family have large showy flowers that are either polysymmetric or monosymmetric. In this study, floral organogenesis of all 10 neotropical genera was examined using SEM. Our observations of floral development are put into the context of a molecular phylogeny based on sequences of the ndhF and trnL‐F genes (Am. J. Bot. 94: 289–301). Floral evolution of the subfamily is explained as having undergone four different levels of complexity in regard to floral symmetry. The basal most genera, Grias and Gustavia, have polysymmetric flowers. At level two, represented only by Couroupita, monosymmetry is established through the expression of abaxial dominance and the development of an androecial hood; at this level, abaxial dominance impacts the perianth and androecium, but not the gynoecium. At the third level, monosymmetry is developed in groups of Couratari and Cariniana domestica; but, in the Allantoma/Cariniana decandra lineage, a reversal back to polysymmetric flowers, resulting from a gradual weakening of abaxial dominance, and the loss of the hood has occurred. Finally, in level four, including Bertholletia, Corythophora, Eschweilera, and Lecythis, monosymmetry is so strongly expressed that the gynoecium is also influenced by abaxial dominance. In this group, the hood is complicated in both structure and function, and the floral axis is changed from straight to slightly inclined. This study demonstrates that the development of floral abaxial dominance is the proximate cause of monosymmetry in the Lecythidoideae. We suggest that monosymmetric flowers are more efficiently pollinated, and therefore the bees and bats that pollinate the monosymmetric flowers in this group are ultimately responsible for the monosymmetry.
Reproductive potential of balsam fir (Abies balsamea), white spruce (Picea glauca), and black spruce (P. mariana) at the ecotone between mixedwood and coniferous forests in the boreal zone of western Quebec
Authors: Messaoud Yassine , Bergeron Yves , Asselin Hugo
Published: February 2008

The reproductive potentials of balsam fir and white spruce (co‐dominants in mixedwood forests) and black spruce (dominant in coniferous forests) were studied to explain the location of the ecotone between the two forest types in the boreal zone of Quebec. Four sites were selected along a latitudinal gradient crossing the ecotone. Cone crop, number of seeds per cone, percentage filled seeds, and percentage germination were measured for each species. Balsam fir and white spruce cone crops were significantly lower in the coniferous than in the mixedwood forest, while black spruce had greater crop constancy and regularity between both forest types. Mast years were more frequent for black spruce than for balsam fir in both forest types (mast year data not available for white spruce). The number of seeds per cone was more related to cone size than to forest type for all species. Black spruce produced more filled seeds in the coniferous forest than balsam fir or white spruce. The sum of growing degree‐days and the maximum temperature of the warmest month (both for the year prior to cone production) significantly affected balsam fir cone production. The climate‐related northward decrease in reproductive potential of balsam fir and white spruce could partly explain the position of the northern limit of the mixedwood forest. This could change drastically, however, as the ongoing climate warming might cancel this competitive advantage of black spruce.
Ecophysiological responses of two herbaceous species to prescribed burning, alone or in combination with overstory thinning
Authors: Huang Jianjun , Boerner Ralph E. J. , Rebbeck Joanne
Published: February 2008

The oak‐rich deciduous forests of the central Appalachian Mountains of eastern North America have changed significantly since the onset of effective fire suppression early in the 20th century. Those changes have resulted in progressively decreasing light and nutrient supplies to herbaceous perennial understory species. Application of ecological restoration treatments such as reintroduction of frequent dormant‐season fire and overstory thinning to pre‐suppression density often increase light, soil temperature and moisture, and short‐term nutrient availability to pre‐suppression levels. To persist in this environment, perennial understory herbs must be able to acclimate phenotypically to the very different resource supply combinations present with and without fire suppression. As part of a larger study of the response of the long‐lived herbaceous perennialsDesmodium nudiflorumandPanicum bosciito ecosystem restoration treatments in Ohio mixed‐oak forests, this study examined the ecophysiological effects of prescribed burning (B) and the combination of burning and thinning (T + B) in mixed‐oak forests in southern Ohio. Control (C) plants had significantly lower maximum photosynthetic rate (Amax) than those in the treated plots. The enhancement ofAmaxaveraged 26.7% and 52.7% in the B and T + B treatments, respectively. Plants from the T + B plots had higher quantum yield, stomatal conductance, and photosynthetic nutrient use efficiency than B and C plants. B plants had greater intrinsic water use efficiency (WUE) than plants in the C or T + B treatments. Light saturation point (LSP), light compensation point (LCP), and “dark” respiration (DR) did not differ among treatments. Photosynthetic parameters did vary significantly between the species, but no significant treatment × species interactions were detected. Our results support the hypothesis that prescribed burning, especially when combined with overstory thinning, in these perennial herbs can result in phenotypic acclimation characterized by enhanced photosynthetic performance.
Ecological distribution of homobaric and heterobaric leaves in tree species of Malaysian lowland tropical rainforest
Authors: Kenzo Tanaka , Ichie Tomoaki , Watanabe Yoko , Hiromi Toru
Published: February 2008

Tree species can generally be classified into two groups, heterobaric and homobaric leafed species, according to whether bundle‐sheath extensions (BSEs) are found in the leaf (heterobaric leaf) or not (homobaric leaf). In this study, we study whether the leaf type is related to the growth environment and/or life form type, even in a tropical rain forest, where most trees have evergreen leaves that are generally homobaric. Accordingly, we investigated the distribution of leaf morphological differences across different life forms of 250 tree species in 45 families in a tropical rainforest. In total, 151 species (60%) in 36 families had homobaric leaves, and 99 species (40%) in 21 families had heterobaric leaves. We found that the proportion of heterobaric and homobaric leaf species differed clearly across taxonomic groups and life form types, which were divided into five life form types by their mature tree heights (understory, subcanopy, canopy, and emergent species) and as canopy gap species. Most understory (94%) and subcanopy (83%) species such as Annonaceae had homobaric leaves. In contrast, heterobaric leaf trees appeared more frequently in the canopy species (43%), the emergent species (96%) (such as Dipterocarpaceae), and the canopy gap species (62%). Our results suggest that tree species in the tropical rainforest adapt to spatial differences in the environmental conditions experienced at the mature height of each tree species, such as light intensity and vapor pressure difference, by having differing leaf types (heterobaric or homobaric) because these types potentially have different physiological and/or mechanical functions.
Attenuation of incident light in Galax urceolata (Diapensiaceae): concerted influence of adaxial and abaxial anthocyanic layers on photoprotection
Authors: Hughes Nicole M. , Smith William K.
Published: February 2008

Although anthocyanin coloration in lower (abaxial) leaf cells has been documented for numerous species, the functional significance of this character has not been comprehensively investigated according to habitat or leaf orientation. Here, we demonstrate that abaxial anthocyanin may function as a photoprotectant, similarly to its purported role in upper (adaxial) cells, in leaves vulnerable to high irradiance incident on abaxial surfaces. Spectral scans were derived for Galax urceolata leaves with the following phenotypes: abaxial or adaxial anthocyanin only, abaxial and adaxial anthocyanin, and no anthocyanin. To determine whether anthocyanins conferred protection from photoinhibition, maximum photosystem II efficiencies of red (anthocyanic) and green (acyanic) surfaces were compared during and after exposure to photoinhibitory conditions. Leaves were either positioned with their adaxial surfaces facing the light source or inverted to expose abaxial surfaces. Spectral scans showed increased absorptance of 500–600 nm wavelengths by red surfaces (consistent with the absorbance spectrum of anthocyanin), regardless of whether that surface was abaxial or adaxial. Leaves with anthocyanin in either illuminated surface were also photoinhibited less than leaves lacking anthocyanin in that surface. These results suggest that anthocyanic layers reduce absorbed sunlight in the mesophyll not only for adaxial surfaces, but also for the abaxial. Adaxial/abaxial anthocyanin plasticity may therefore be adaptive in high‐light environments or during light‐sensitive developmental stages where leaf orientation and/or substrate albedo are variable.
Drought response of two Mexican oak species, Quercus laceyi and Q. sideroxyla (Fagaceae), in relation to elevational position
Authors: Poulos H. M. , Goodale U. M. , Berlyn G. P.
Published: February 2008

To investigate the relationship between the altitudinal distribution of Quercus laceyi and Q. sideroxyla and their physiological responses to drought, we measured relative water content (RWC), water potentials (Ψpredawn and Ψmidday), photosynthesis (Amax), stomatal conductance (g), chlorophyll fluorescence (Fv/Fm), and spectral reflectance (400–1100 nm) five times during a 7 wk acute drought. Quercus laceyi was drought tolerant, while Q. sideroxyla was a drought avoider; Q. laceyi tolerated lower RWC (Q. sideroxyla = 54%, Q. laceyi = 44%), Ψpd (Q. sideroxyla = −2.6 MPa, Q. laceyi = −3.3 MPa), and Ψmd (Q. sideroxyla = −4.5 MPa, Q. laceyi = −6.6 MPa). The Fv/Fm also declined first in Q. sideroxyla in wk 6, whereas Fv/Fm did not decline in Q. laceyi until wk 7. Amax and g fell in wk 4, 6, and 7 in drought seedlings of both species, suggesting a decline in CO2 assimilation during the drought. Leaf spectral reflectance increased with time in response to decreases in leaf photosynthetic pigment concentrations in latter weeks of the drought. The results suggest a close association between the altitudinal distributions of these species and their adaptation to water stress.
Population structure of Pacific Cordyline fruticosa (Laxmanniaceae) with implications for human settlement of Polynesia
Authors: Hinkle Anya E.
Published: February 2008

The Polynesian‐introduced Cordyline fruticosa is used as a proxy for reconstructing human colonization patterns in Oceania. Because of its material, nutritional, medicinal, and religious importance, green‐leaved C. fruticosa was transferred by Polynesian settlers to virtually every habitable Pacific island before European contact. Previous studies propose that green‐leaved C. fruticosa is unable to reproduce sexually. To confirm sterility, crosses between fertile and putatively sterile forms were performed. To look for population structure in C. fruticosa that might confirm sterility as well as illustrate patterns of human migration, amplified fragment length polymorphism data were generated. Genotypic similarities were visualized using neighbor joining phenograms and analyses of molecular variance and principal components. The results from greenhouse crosses show that the Eastern Polynesian form is sterile; this finding is corroborated by a lack of genetic variability in Eastern Polynesian accessions. Sterile C. fruticosa appears to have been preferentially transferred throughout Eastern Polynesia; selection for the sterile form may be related to consumption of its rhizomes. Identification of a sterile form of C. fruticosa, possibly developed within Western Polynesia, may be significant to the systematics of Cordyline because it raises the possibility that the fertile form may actually be native to some Pacific islands.
A molecular phylogeny of scaly tree ferns (Cyatheaceae)
Authors: Korall Petra , Conant David S. , Metzgar Jordan S. , Schneider Harald , Pryer Kathleen M.
Published: February 2008

Tree ferns recently were identified as the closest sister group to the hyperdiverse clade of ferns, the polypods. Although most of the 600 species of tree ferns are arborescent, the group encompasses a wide range of morphological variability, from diminutive members to the giant scaly tree ferns, Cyatheaceae. This well‐known family comprises most of the tree fern diversity (∼500 species) and is widespread in tropical, subtropical, and south temperate regions of the world. Here we investigate the phylogenetic relationships of scaly tree ferns based on DNA sequence data from five plastid regions (rbcL, rbcL‐accD IGS, rbcL‐atpB IGS, trnG‐trnR, and trnL‐trnF). A basal dichotomy resolves Sphaeropteris as sister to all other taxa and scale features support these two clades: Sphaeropteris has conform scales, whereas all other taxa have marginate scales. The marginate‐scaled clade consists of a basal trichotomy, with the three groups here termed (1) Cyathea (including Cnemidaria, Hymenophyllopsis, Trichipteris), (2) Alsophila sensu stricto, and (3) Gymnosphaera (previously recognized as a section within Alsophila) + A. capensis. Scaly tree ferns display a wide range of indusial structures, and although indusium shape is homoplastic it does contain useful phylogenetic information that supports some of the larger clades recognised.
Seed size, seedling morphology, and response to deep shade and damage in neotropical rain forest trees
Authors: Baraloto Christopher , Forget Pierre‐Michel
Published: February 2008

To investigate the existence of coordinated sets of seedling traits adapted to contrasting establishment conditions, we examined evolutionary convergence in seedling traits for 299 French Guianan woody plant species and the stress response in a shadehouse of species representing seed size gradients within five major cotyledon morphology types. The French Guianan woody plant community has larger seeds than other tropical forest communities and the largest proportion of hypogeal cotyledon type (59.2%) reported for tropical forests. Yet the community includes many species with intermediate size seeds that produce seedlings with different cotyledonal morphologies. A split‐plot factorial design with two light levels (0.8% and 16.1% PAR) and four damage treatments (control, seed damage, leaf damage, stem damage) was used in the shadehouse experiment. Although larger‐seeded species had higher survival and slower growth, these patterns were better explained by cotyledon type than by seed mass. Even larger‐seeded species with foliar cotyledons grew faster than species with reserve‐type cotyledons, and survival after stem grazing was five times higher in seedlings with hypogeal cotyledons than with epigeal cotyledons. Thus, to predict seedling performance using seed size, seedling morphology must also be considered.
Molecular and morphological evidence reveals introgression in swarms of the invasive taxa Fallopia japonica, F. sachalinensis, and F. ×bohemica (Polygonaceae) in the United States
Authors: Gammon Melinda A. , Grimsby Jonna L. , Tsirelson Dina , Kesseli Rick
Published: February 2008

Fallopia japonica (Japanese knotweed, Polygonaceae) is a well‐known East Asian perennial that is established throughout the U.S. and Europe. Another congener, F. sachalinensis, and their hybrid, F. ×bohemica, also persist on both continents. Their invasive success is primarily attributed to their ability to spread via clonal growth. However, mounting evidence suggests invasion history and dynamics differ between continents and that sexual reproduction is more common than previously assumed. We used published morphological traits designed to distinguish the three taxa to characterize their distribution in 24 New England towns. We found continuous variation of all five traits, with 84% of our 81 individuals having at least one trait outside parental limits. Hierarchical cluster analysis, along with two chloroplast and one nuclear species‐specific markers, suggests the presence of intercrossing, segregating hybrids, and likely introgression between F1 hybrids and F. japonica. Our markers also show the first evidence of bidirectional hybridization between parental taxa in the U.S., emphasizing the complex structure of populations in our region. This study is a first step toward unraveling the evolutionary forces that have made these taxa such aggressive invaders in the U.S. The data may also affect management strategies originally designed for largely monomorphic, clonal populations.
Increased selfing and decreased effective pollen donor number in peripheral relative to central populations inPicea sitchensis(Pinaceae)
Authors: Mimura Makiko , Aitken Sally N.
Published: February 2008

Because mating system can be influenced by effective neighborhood size, density, and isolation, populations at range peripheries may differ from those in the center. The importance of peripheral populations to conservation and evolution is controversial, and additional information about their genetic structure and evolutionary dynamics will inform conservation strategies. In wind‐pollinated species, selfing rate is generally negatively correlated with population size and density, and inbreeding may therefore increase toward range peripheries.Picea sitchensishas a long and narrow range along the Pacific Coast of North America that tapers toward the northern and southern peripheries. We investigated whether central and peripheral populations differ in mating system parameters. The results suggest that population position within the range has a strong effect on mating system, and geographic isolation appears to be associated with higher selfing. The estimated effective number of pollen donors was much higher in the center of the range (mean = 18.5) than at the periphery (mean = 3.6), while selfing rate increased from 7.3% in central populations to as high as 35.2% in the northern, isolated population. These strong geographical patterns suggest mating system is influenced by both population size and isolation at range peripheries.
Cell wall degradation and modification during programmed cell death in lace plant, Aponogeton madagascariensis (Aponogetonaceae)
Authors: Gunawardena Arunika H. L. A. N. , Greenwood John S. , Dengler Nancy G.
Published: February 2008

An unusual form of leaf morphogenesis occurs in the aquatic, lace plant, Aponogeton madagascariensis (Aponogetonaceae). Early in development, discrete patches of cells undergo programmed cell death (PCD) and form perforations during leaf expansion. In addition to the protoplasts, walls of the dying cells are degraded during PCD. The cuticle of the perforation site is eroded first, followed by dissolution of cell wall matrix components, so that walls appear as loose fibrillar networks as perforations form. Gel diffusion assays of wall‐degrading enzyme activity indicated that pectinases are active throughout leaf development, while cellulase activity was restricted to early stages of perforation formation. Alcian blue staining showed that degrading walls remain rich in pectin, and immunolocalization of pectin epitopes indicated that the proportions of esterified and de‐esterifed pectins do not change significantly. Walls of perforation border cells are modified by suberin deposition late in development, and reactive oxygen species, thought to have a role in polymerization of phenolic suberin monomers, are present at the same stage. This timing suggests that suberization may limit the spread of PCD and provide an apoplastic barrier against microbial invasion but does not initiate PCD.
Plant biomechanical strategies in response to frequent disturbance: uprooting of Phyllostachys nidularia (Poaceae) growing on landslide‐prone slopes in Sichuan, China
Authors: Stokes Alexia , Lucas Adrien , Jouneau Luc
Published: February 2008

Bamboo is considered useful for controlling landslides, but we observed numerous shallow‐slope failures in forests of big node bamboo (Phyllostachys nidularia) in Sichuan, China. Therefore, we inventoried landslide occurrence and vegetation type along one valley. To quantify bamboo root anchorage, we performed uprooting tests and measured plant morphological characteristics. Landslide occurrence was greatest at sites with bamboo and young trees. Culm failure was common because of the high length to diameter ratio (242 ± 6). Uprooting tests showed that the maximal force to cause failure was small (1615 ± 195 N). Uprooting force was strongly and positively regressed with a combination of the predictors lateral root number and volume (R2 = 0.92), and root systems were highly superficial (depth = 0.15 ± 0.12 m), contributing little to slope stability. In P. nidularia, which grows on landslide‐prone slopes, surprisingly few resources have been allocated to anchorage. We suggest that this strategy puts this pioneer at an advantage on steep slopes, where it contributes little to slope stability and colonizes frequently formed gaps through vegetative regeneration. Fewer disturbances would result in subsequent secondary succession and dying back of this shade intolerant species.
Delayed stigma receptivity inCollinsia heterophylla(Plantaginaceae): genetic variation and adaptive significance in relation to pollen competition, delayed self‐pollination, and mating‐system evolution
Authors: Lankinen Åsa , Armbruster W. Scott , Antonsen Liv
Published: February 2008

To increase our knowledge about mating‐system evolution, we need to understand the relationship between specific floral traits and mating system. Species ofCollinsia(Plantaginaceae) vary extensively in mating system; this variation is associated with variation in floral morphology and development and with the timing of self‐pollination. Counterintuitively, large‐flowered, more outcrossing species tend to have delayed stigma receptivity, reducing the amount of time that the stigma is receptive to cross‐pollination before autonomous self‐pollination. To understand how the timing of stigma receptivity is related to mating‐system evolution, we studied in detail the timing of both stigma receptivity and self‐pollination (anther–stigma contact) in two greenhouse‐grown populations of large‐floweredCollinsia heterophylla. Crosses on emasculated flowers at different stages of floral development always produced seeds, suggesting that cross‐fertilization can be effected by pollen arriving prior to physiological receptivity. Phenotypic and genetic variation within populations in the timing of stigma receptivity and anther–stigma contact was substantial, although slightly less for the contact. Despite strong interspecific and interpopulation correlations, we did not find an among‐genet phenotypic correlation between the traits. This indicates that each trait may respond independently to selection, and the trait association may be the result of correlational selection.
AFLP and DNA sequence variation in an Andean domesticate, pepino (Solanum muricatum, Solanaceae): implications for evolution and domestication
Authors: Blanca José M. , Prohens Jaime , Anderson Gregory J. , Zuriaga Elena , Cañizares Joaquín , Nuez Fernando
Published: February 2008

The pepino (Solanum muricatum) is a vegetatively propagated, domesticated native of the Andes, where it grows with wild relatives. We used AFLPs and a 1‐kb sequence of the 3‐methylcrotonyl‐CoA carboxylase gene to study variation of 27 accessions of S. muricatum and 35 collections of 10 species of wild relatives (Solanum section Basarthrum). A total of 298 AFLP fragments and 29 DNA sequence haplotypes were detected. Cluster and principal coordinate analyses and other genetic parameters estimated from both types of markers, show that S. muricatum is closely related to the species from one of the series (Caripensia) of section Basarthrum and that >90% of the variation of the cultigen is also represented in that series. Pepino is highly diverse, either because it is not monophyletic or it has been subjected to regular introgression with wild species, or both. Although a continuous distribution of the genetic variation occurred within the cultivated species, three genetic clusters were recognized. Cluster 1 is mostly centered in Ecuador, cluster 2 in Ecuador and Peru, and cluster 3 in Colombia and Ecuador. Cluster 3 also includes all modern cultivars studied. These results and other evidence suggest that northern Ecuador/southern Colombia is the main center of pepino diversity and the center of origin. The high genetic variation of this cultigen indicates that domestication does not always produce a genetic bottleneck.
The molecular phylogeny of Rebutia (Cactaceae) and its allies demonstrates the influence of paleogeography on the evolution of South American mountain cacti
Authors: Ritz Christiane M. , Martins Ludwig , Mecklenburg Rainer , Goremykin Vadim , Hellwig Frank H.
Published: February 2008

The tropical Andes harbor a major part of the world's plant biodiversity. The montane cacti of the tribes Browningieae, Cereeae, and Trichocereeae underwent extensive radiation and thus are well suited as a model group to study the diversification of Andean plants. We reconstructed their phylogeny employing three noncoding chloroplast regions and explained it in the context of the geological history of South America. We found that the clade of cephalia‐bearing cacti with naked pericarpels is centered in northeastern Brazil, whereas almost all other clades comprise Andean species. The spatial split between the clades was probably caused by the Andean uplift and the concurrent formation of intracontinental marine basins in the Tertiary. The phylogenetic reconstructions based on parsimony and Bayesian approaches do not reflect the traditional delimitation of the tribes and of the large genera. Our results suggest that Rebutia s.l. and Echinopsis s.l. are not monophyletic and that Sulcorebutia, Weingartia, and Cintia should be united into one genus. Even though this “Weingartia‐complex” and the genus Gymnocalycium are similar in size and morphological diversity, Gymnocalycium has a very high molecular divergence suggesting a comparably older radiation.
Molecular phylogeny of the moonseed family (Menispermaceae): implications for morphological diversification
Authors: Ortiz Rosa Del C. , Kellogg Elizabeth A. , Van Der Werff Henk
Published: February 2008

We used the chloroplast gene ndhF to reconstruct the phylogeny of the moonseed family (Menispermaceae), a morphologically diverse and poorly known cosmopolitan family of dioecious, primarily climbing plants. This study includes a worldwide sample of DNA sequences for 88 species representing 49 of the 70 genera of all eight traditionally recognized tribes. Phylogenetic relationships were estimated, and the Shimodaira–Hasegawa test was used to compare the likelihood of alternative phylogenetic hypotheses and to evaluate the monophyly of tribes currently in use. The monospecific Indo‐Malesian Tinomiscium is sister to the remaining members of the family, within which are two major clades. Within these two clades, well‐supported clades correspond to four of the eight traditionally recognized tribes, while others, such as Menispermeae, are polyphyletic. Mapping of major morphological characters on the phylogeny indicates that the crescent‐shaped seed is derived from a straight seed, the tree habit has arisen multiple times, endosperm has been lost many times, but unicarpellate flowers evolved only once. Morphological synapomorphies for Menispermaceae include the presence of a condyle, a large embryo, and druplets. The phylogeny provides for the first time a detailed molecular‐based assessment of relationships in Menispermaceae and clarifies our understanding of morphological diversification within the family.
Structural attributes of the hypogeous holoparasiteHydnora tricepsDrège & Meyer (Hydnoraceae)
Authors: Tennakoon Kushan U. , Bolin Jay F. , Musselman Lytton J. , Maass Erika
Published: February 2008

The morphology of the hypogeous root holoparasiteHydnora tricepsis highly reduced, and as with many holoparasites, the vegetative body is difficult to interpret. The vegetative body ofH. tricepshas been historically considered a “pilot root” studded with lateral appendages known as “haustorial roots.” We found the vegetative body ofH. tricepsto consist of a rhizome with a thickened root‐cap‐like structure that covered a vegetative shoot apical meristem. From the apical meristem, procambial strands originated and developed into endarch collateral vascular bundles arranged radially around a pith without an interfascicular cambium. Xylem vessels had scalariform pitting and simple perforation plates. A continuous periderm without root hairs was observed. Increase in girth was attributed to cork and fascicular cambia. “Haustorial roots” or bumps on the surface of the vegetative body were exogenous, contained meristems and were the origins of vegetative branching, budding, and haustoria. The haustoria ofH. tricepswere cylindrical and penetrated the host root stele. Phloem and xylem elements were observed within the endophyte, and direct xylem to host‐xylem contacts were observed. The arrangement of vascular tissues and xylem anatomy ofH. tricepsare likely plesiomorphic features in light of Hydnoraceae's placement in the Piperales.
Polyploidy and self‐fertilization in flowering plants
Authors: Barringer Brian C.
Published: February 2008

Mating systems directly control the transmission of genes across generations, and understanding the diversity and distribution of mating systems is central to understanding the evolution of any group of organisms. This basic idea has been the motivation for many studies that have explored the relationships between plant mating systems and other biological and/or ecological phenomena, including a variety of floral and environmental characteristics, conspecific and pollinator densities, growth form, parity, and genetic architecture. In addition to these examples, a potentially important but poorly understood association is the relationship between plant mating systems and genome duplication, i.e., polyploidy. It is widely held that polyploid plants self‐fertilize more than their diploid relatives, yet a formal analysis of this pattern does not exist. Data from 235 species of flowering plants were used to analyze the association between self‐fertilization and ploidy. Phylogenetically independent contrasts and cross‐species analyses both lend support to the hypothesis that polyploids self‐fertilize more than diploids. Because polyploidy and self‐fertilization are so common among angiosperms, these results contribute not only to our understanding of the relationship between mating systems and polyploidy in particular, but more generally, to our understanding of the evolution of flowering plants.
Growth pattern and age determination for Cecropia sciadophylla (Urticaceae)
Authors: Zalamea Paul‐Camilo , Stevenson Pablo R. , Madriñán Santiago , Aubert Pierre‐Marie , Heuret Patrick
Published: February 2008

Cecropia species, ranging from Mexico to northern Argentina and the West Indies, are pioneer trees that colonize cleared areas with high light. To determine their ages to help pinpoint the date of the area's disturbance, we need to understand their developmental and architectural changes over time. The simple architecture of Cecropia conforms to the model of Rauh; that is, it has orthotropic axes with lateral flowering and rhythmic branching. The axes are made of a succession of nodes and internodes whose length and associated lateral productions remain measurable for years. Thus, by describing the tree trunk node by node, we can depict the sequence of events involved in tree development. For 25 trees of C. sciadophylla, from two stations in French Guiana and Colombia, we recorded internode length and any presence of branches, and flowers for each node. Using autocorrelation coefficients, we found a high periodicity in flowering and branching, with inflorescences at every 25 nodes, stages of branches spaced by a multiple of 25 nodes, and alternation of long and short nodes every 25 nodes. Considering that flowering is annual for many Cecropia species, the main conclusion of this work is that C. sciadophylla has strong annual growth, branching, and flowering rhythms. In addition, the age of the tree can be estimated retrospectively by observing its adult morphology.
Dispersal limitations, rather than bottlenecks or habitat specificity, can restrict the distribution of rare and endemic rainforest trees
Authors: Rossetto Maurizio , Kooyman Robert , Sherwin William , Jones Rebecca
Published: February 2008

Despite their narrow distribution, Australian rainforests still contain considerable levels of diversity and include many ancient, but often rare, lineages. Very little is known about the general biology of rainforest species, yet their long‐term management depends on a better understanding of the main factors leading to rarity. For instance, are they highly endemic taxa, at the early stages of expansion, nearing the end of a period of decline, or persisting at low numbers over the long term? In this study we combine molecular, environmental, and ecological data to identify the factors responsible for the narrow distribution of a paleoendemic rainforest tree: Elaeocarpus sedentarius (Elaeocarpaceae). Between‐population and between‐generation comparisons of genetic diversity across all known populations of E. sedentarius show evidence of mutation–drift equilibrium rather than evidence of a recent bottleneck. Similarly, floristic and environmental data negate the hypothesis of rarity as a consequence of highly specialized habitat requirements. Instead, genetic structure and the available ecological data support the hypothesis of dispersal limitation as the main cause of endemism and that the species may have attained genetic equilibrium without realizing its full niche potential. We suggest that these factors are likely to explain narrow endemism in a broader range of taxa.
A Practical Guide to Opportunity Assessment Methods
Authors: Liao Peter , Witsil Amy
Published: February 2008

Based on the authors' experience, a gap is apparent between technology managers' needs and opportunity assessment resources. Many organizations need a tool for evaluating seed funding or small business investment opportunities, but they lack a means for determining what options are available. This research report describes several opportunity assessment methods and matches the methods to user types in public and private sector organizations in analyzing technical, business, and market information for investment and commercialization decisions. Organizations that may benefit from this review share a common goal of seeking to strengthen the viability of a new technology venture or capitalizing on their investment in new technology. These include venture capitalists who choose investments (in early-stage technology companies) that will return the largest return on investment for their client investors, angel investors placing their own money in pet projects, public or quasi-public new or small business-funding agencies, and academic and government research and development agencies. The authors' focus was to evaluate not only the availability of methods but also the associated analysis framework in order to understand which opportunity assessment methods are optimal in supporting various investment objectives and stakeholders. This report should also provide individuals in the technology transfer and commercialization community with a succinct, useful reference for identifying what methods are available to them and which methods work best in various situations.
Xanthine Oxidoreductase
Authors: Nishino Takeshi , Pai Emil F
Published: March 2008

A single gene product has been identified as responsible for the two catalytic activities, xanthine dehydrogenase, XDH (EC 1.1.1.204), and xanthine oxidase, XO (EC 1.2.3.2). Synthesized as XDH (ultimate electron acceptor NAD+), the protein can be converted to XO (ultimate electron acceptor oxygen) either reversibly by oxidation of cysteine residues or irreversibly by proteolysis. Xanthine oxidoreductase (XOR) is a ubiquitous enzyme; its physiological role is the oxidation of hypoxanthine to xanthine and further to uric acid, althoughin vitrothe enzyme's specificity is rather broad, accepting a large number of purines, pteridines, and aldehydes as substrates. XOR, in contrast to most other hydroxylases, incorporates water‐derived oxygen into its substrate. The electrons are transferred from xanthine to a Mopterin center and from there via two Fe2–S2clusters and FAD to NAD+or oxygen, respectively. The enzyme is the target of the antigout drug allopurinol; it is involved in hyperuricemia and xanthinuria and postulated to participate in postischemic reperfusion injury. Crystal structures have been determined for native and mutant XDHs and XOs from man, cow, rat, andRhodobacter capsulatus. The conformational changes linked to the dehydrogenase/oxidase transition have been identified and interpreted. A structure‐based explanation for the catalytic mechanism is emerging.
CO
Dehydrogenase/Acetyl‐
Co
A
Synthase
Authors: Fontecilla‐Camps Juan C , Volbeda Anne
Published: March 2008

The bifunctional tetrameric (α
2
β
2
) enzyme carbon monoxide dehydrogenase (CODH)/acetyl‐CoA synthase (ACS) is a central component of the Wood‐Ljungdahl pathway of acetogenic bacteria. In this pathway, two CO
2
molecules are reduced to a methyl group by folate‐containing enzymes and to CO by CODH, respectively. These two substrates are subsequently combined in ACS to form an Ni‐bound acetyl group that is reductively eliminated as acetyl‐CoA. The CODH and ACS active sites are about 70 Å apart and are connected by a network of hydrophobic tunnels. Thus, CO produced at the former enzyme migrates inside the bifunctional protein to the ACS site. Site‐directed mutagenesis has confirmed the functional role of the tunnels. The ACS subunit undergoes a conformational change that blocks the tunnel near the active site, preventing the escape of the toxic CO from within the enzyme upon methyl binding to nickel.
Association of PIP5K2A with schizophrenia: A study in an indonesian family sample
Authors: Saggers‐Gray L. , Heriani H. , Handoko H.Y. , Irmansyah I. , Kusumawardhani A.A.A.A. , Widyawati I. , Amir N. , Nasrun M.W.S. , Schwab S.G. , Wildenauer D.B.
Published: March 2008

PIP5K2A variants have been shown to be associated with schizophrenia in Caucasian populations. This study tested 12 PIP5K2A SNPs for association with schizophrenia in a sample of 152 sib‐pair families of Indonesian descent. All SNPs had previously been tested for association with schizophrenia in a German family sample by Schwab et al. [2006; Mol Psychiatry] and seven SNPs were nominally associated with schizophrenia in this previous study. The purpose of the study was to examine whether previously implicated PIP5K2A variants influence susceptibility to schizophrenia in populations of non‐European descent. No single markers showed nominal association with schizophrenia in this Indonesian family sample, however multi‐marker haplotypes including a previously associated exonic SNP marker revealed nominally significant association (P = 0.03). Power to detect association was greater than 80% for all previously implicated variants except for rs11013052, where power was greatly reduced due to the low minor allele frequency of this marker in the Indonesian sample. An explorative study combining the results of this study with those of our previous study indicated that rs11013052 was significantly associated with schizophrenia in the combined sample (P = 0.002). The results of this study suggest that any contribution of previously implicated DNA variants within the PIP5K2A gene to schizophrenia susceptibility in the Indonesian population is only minor. © 2008 Wiley‐Liss, Inc.
Recognition of rhesus macaque (Macaca mulatta) noisy screams: evidence from conspecifics and human listeners
Authors: Fugate Jennifer M.B. , Gouzoules Harold , Nygaard Lynne C.
Published: March 2008

Vocalizations are among the diverse cues that animals use to recognize individual conspecifics. For some calls, such as noisy screams, there is debate over whether such recognition occurs. To test recognition of rhesus macaque noisy screams, recorded calls were played back to unrelated and related conspecific group members as either single calls or short bouts. Higher‐ranking, but not lower‐ranking, monkeys looked longer toward the playback speaker in trials containing screams from kin than in those composed of screams from nonkin. In a second study, human listeners performed a “same/different” discrimination task between presentations of rhesus screams from either the same or two different monkeys. Listeners discriminated between “same” and “different” callers above an established empirical threshold, whether screams were presented singly or in short bouts. Together, these results suggest that rhesus monkeys can distinguish noisy screams between kin and nonkin, and humans are able to discriminate different individuals' noisy screams, even when the duration of the bout is short. Whether noisy screams are ideally designed signals for individual recognition is discussed with respect to possible evolutionary origins of the calls. Am. J. Primatol. 70:594–604, 2008. © 2008 Wiley‐Liss, Inc.
Exogene Wirkstoffe zur Erkennung von Transmembrandomänen von Proteinen
Authors: Yin Hang
Published: March 2008

Ungefähr ein Drittel aller im menschlichen Genom codierten Proteine sind Membranproteine. Funktion und Struktur ihrer Transmembrandomänen sind weitaus weniger gut verstanden als die der wasserlöslichen Regionen. Die größte Hürde bei der Untersuchung dieser Domänen ist der Mangel an geeigneten exogenen Substanzen, die als spezifisch bindende Sonden eingesetzt werden könnten. Trotz dieser Schwierigkeiten ist es in jüngster Zeit mehrfach gelungen, die Transmembrandomänen verschiedener Membranproteine gezielt anzusteuern. In biophysikalischen Modellsystemen, bakteriellen Membranen und Säugerzellen konnten hohe Affinitäten und Selektivitäten erzielt werden.
Generalized Inferences on the Overall Treatment Effect in Meta‐analysis with Normally Distributed Outcomes
Authors: Tian Lili
Published: March 2008

This paper focuses on inferences about the overall treatment effect in meta‐analysis with normally distributed responses based on the concepts of generalized inference. A refined generalized pivotal quantity based on t distribution is presented and simulation study shows that it can provide confidence intervals with satisfactory coverage probabilities and perform hypothesis testing with satisfactory type‐I error control at very small sample sizes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Mixed Approach for Proving Non‐Inferiority in Clinical Trials with Binary Endpoints
Authors: Rousson Valentin , Seifert Burkhardt
Published: March 2008

When a new treatment is compared to an established one in a randomized clinical trial, it is standard practice to statistically test for non‐inferiority rather than for superiority. When the endpoint is binary, one usually compares two treatments using either an odds‐ratio or a difference of proportions. In this paper, we propose a mixed approach which uses both concepts. One first defines the non‐inferiority margin using an odds‐ratio and one ultimately proves non‐inferiority statistically using a difference of proportions. The mixed approach is shown to be more powerful than the conventional odds‐ratio approach when the efficacy of the established treatment is known (with good precision) and high (e.g. with more than 56% of success). The gain of power achieved may lead in turn to a substantial reduction in the sample size needed to prove non‐inferiority. The mixed approach can be generalized to ordinal endpoints. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Holding period effect and home price indexes: a dynamic analysis
Authors: He Ling T.
Published: March 2008

Four major home price indexes have been used in this study, and are based on different calculation methods and from different sources. The descriptive statistics indicate no meaningful differences among them. However, by analysing the orthogonalized impulse response and variance decomposition matrixes from the vector autoregressions, this study found some noticeable differences in the dynamic relationships between these indexes and three other housing factors – mortgage rates, existing home sales and new home sales – in addition to the inflation factor. The results may reflect the holding period effect in repeat sales house price indexes. Copyright © 2008 John Wiley & Sons, Ltd.