bluuebunny/crossref_metadata_2025 huggingface dataset:
Population differentiation and gene flow within a metapopulation of a threatened tree,Magnolia stellata(Magnoliaceae)
Authors: Setsuko Suzuki , Ishida Kiyoshi , Ueno Saneyoshi , Tsumura Yoshihiko , Tomaru Nobuhiro
Published: February 2008

We examined genetic differentiation among eight local populations of a metapopulation ofMagnolia stellatausing 10 nuclear and three chloroplast microsatellite (nSSR and cpSSR) markers and evaluated the influence of historical gene flow on population differentiation. The coefficient of genetic differentiation among populations for nSSR (FST= 0.053) was less than half that for cpSSR (0.137). An isolation‐by‐distance pattern was detected for nSSRs, but not cpSSRs. These results suggest that pollen flow, as well as seed dispersal, has significantly reduced genetic differentiation among populations. We also examined patterns of contemporary pollen flow by paternity analysis of seeds from nine seed parents in one of the populations using the nSSR markers and found it to be greatly restricted by the distance between parents. Although most pollen flow occurred within the population, pollen flow from outside the population accounted for 2.5% of the total. When historical and contemporary pollen flows among populations were compared, the levels of pollen flow seem to have declined recently. We conclude that to conserveM. stellata, it is important to preserve the whole population by maintaining its metapopulation structure and the gene flow among its populations.
Comparative ontogeny of the cyathium in Euphorbia (Euphorbiaceae) and its allies: exploring the organ–flower–inflorescence boundary
Authors: Prenner Gerhard , Rudall Paula J.
Published: February 2008

We present a detailed comparative ontogenetic analysis of pseudanthia of representatives of all three subtribes of Euphorbieae (Euphorbiinae, Neoguillauminiinae, Anthosteminae) in order to clarify their homologies and interpretation. The cyathium of Euphorbia and its allies (subtribe Euphorbiinae) closely resembles a bisexual flower but is traditionally interpreted as an inflorescence bearing clusters of highly reduced male flowers surrounding a single terminal female flower. Previously unreported characters are (1) male flowers formed one above the other in the male inflorescences of some Euphorbiinae, (2) late‐developing perianthlike structures in some male flowers of Neoguillauminia cleopatra, (3) evidence for a bracteate origin of the female perianth in Anthosteminae and Neoguillauminiinae, and (4) spatiotemporally independent formation of abscission zone and perianth. Indistinct boundaries between inflorescence, flower, and floral organs demonstrate that defining the cyathium neither as an inflorescence nor as a flower is entirely satisfactory and indicate a “hybrid” flower/inflorescence nature of the cyathium. Based on our current knowledge and the existing phylogenetic context, it is most parsimonious to suggest that the cyathium evolved from a determinate thyrse with a terminal female flower surrounded by dichasial male partial inflorescences. We speculate that the cyathium was formed because of strong condensation and possible overlap between expression zones of regulatory genes.
Reproductive structures of Rhamnaceae from the Cerro del Pueblo (Late Cretaceous, Coahuila) and Coatzingo (Oligocene, Puebla) Formations, Mexico
Authors: Calvillo‐Canadell Laura , Cevallos‐Ferriz Sergio R. S.
Published: February 2008

Recently discovered fossil flowers from the Cretaceous Cerro del Pueblo and flowers and fruits from the Oligocene Coatzingo Formations are assigned to the Rhamnaceae. The Cretaceous flower, Coahuilanthus belindae Calvillo‐Canadell and Cevallos‐Ferriz, gen. et sp. nov., is actinomorphic with fused perianth parts forming a slightly campanulate to cupulate floral cup, with sepals slightly keeled and spatulate clawed petals. The Oligocene fossils include Nahinda axamilpensis Calvillo‐Canadell and Cevallos‐Ferriz, gen. et sp. nov. (characterized by its campanulate bisexual flower with stamens opposite, adnate to and enfolded by petals; and with the ovary ripening into a drupe), and a winged fruit assigned to Ventilago engoto Calvillo‐Canadell and Cevallos‐Ferriz, sp. nov. The flowers and drupe features indicate closer affinity to Zizipheae and/or Rhamneae, while the single samaroid fruit suggests the presence of Ventilagineae. However, the unique character combination in the fossil flowers precludes placing them in extant genera. Nevertheless, the history of the family is long and can be traced back to the Campanian. A detailed phylogenetic revision of the group that uses morphological characters from both extant and fossil plants is needed to better understand the significance of these records as well as other important fossils of the family.
The role of auxin transport during inflorescence development in maize (Zea mays, Poaceae)
Authors: Wu Xianting , McSteen Paula
Published: February 2008

Axillary meristems play a fundamental role in inflorescence architecture. Maize (Zea mays) inflorescences are highly branched panicles because of the production of multiple types of axillary meristems. We used auxin transport inhibitors to show that auxin transport is required for axillary meristem initiation in the maize inflorescence. The phenotype of plants treated with auxin transport inhibitors is very similar to that of barren inflorescence2 (bif2) and barren stalk1 (ba1) mutants, suggesting that these genes function in the same auxin transport pathway. To dissect this pathway, we performed RNA in situ hybridization on plants treated with auxin transport inhibitors. We determined that bif2 is expressed upstream and that ba1 is expressed downstream of auxin transport, enabling us to integrate the genetic and hormonal control of axillary meristem initiation. In addition, treatment of maize inflorescences with auxin transport inhibitors later in development results in the production of single instead of paired spikelets. Paired spikelets are a key feature of the Andropogoneae, a group of over 1000 grasses that includes maize, sorghum, and sugarcane. Because all other grasses bear spikelets singly, these results implicate auxin transport in the evolution of inflorescence architecture. Furthermore, our results provide insight into mechanisms of inflorescence branching that are relevant to all plants.
Complementarity in mineral nitrogen use among dominant plant species in a subalpine community
Authors: Pornon André , Escaravage Nathalie , Lamaze Thierry
Published: February 2008

The underlying mechanisms that enable plant species to coexist are poorly understood. Complementarity in resource use is among the major mechanisms proposed that could favor species coexistence but is insufficiently documented. In alpine soil, low temperatures are a major constraint for the supply of plant nitrogen. We carried out 15N labeling of soil mineral N to determine to what extent four major species of a subalpine community compete for N, or develop ionic (NH4+ vs. NO3−) or temporal complementarity. The Poaceae took up much more 15N per soil area unit than the ericaceous species, and all species displayed three major strategies in exploiting 15N: (1) uptake mainly early in the growing season (Vaccinium myrtillus), (2) uptake at a slow and similar rate throughout the growing season (Rhododendron ferrugineum), and (3) uptake at high rates over the growing season (Festuca eskia and Nardus stricta). However, while F. eskia used 15NH4+ mainly early and 15NO3− mainly late in the growing season, the reverse was observed for N. stricta. Taking into account 15N dilution in soil NH4+ and NO3− pools, we calculated that NH4+ provided more than 80% of the mineral N uptake in Ericaceae and about 60% in grasses. Together, such ionic and temporal complementarity would reduce competition between species and could be a major mechanism promoting species diversity.
Seed‐mass effects in four Mediterranean Quercus species (Fagaceae) growing in contrasting light environments
Authors: Quero José Luis , Villar Rafael , Marañón Teodoro , Zamora Regino , Poorter Lourens
Published: February 2008

Three hypotheses have been proposed to explain the functional relationship between seed mass and seedling performance: the reserve effect (larger seeds retain a larger proportion of reserves after germinating), the metabolic effect (seedlings from larger seeds have slower relative growth rates), and the seedling‐size effect (larger seeds produce larger seedlings). We tested these hypotheses by growing four Mediterranean Quercus species under different light conditions (3, 27, and 100% of available radiation). We found evidence for two of the three hypotheses, but none of the four species complied with all three hypotheses at the same time. The reserve effect was not found in any species, the metabolic effect was found in three species (Q. ilex, Q. pyrenaica, and Q. suber), and the seedling‐size effect in all species. Light availability significantly affected the relationships between seed size and seedling traits. For Q. ilex and Q. canariensis, a seedling‐size effect was found under all three light conditions, but only under the lowest light (3%) for Q. suber and Q. pyrenaica. In all species, the correlation between seed mass and seedling mass increased with a decrease in light, suggesting that seedlings growing in low light depend more upon their seed reserves. A causal model integrates the three hypotheses, suggesting that larger seeds generally produced larger seedlings.
Leaf physiology reflects environmental differences and cytoplasmic background inIpomopsis(Polemoniaceae) hybrids
Authors: Wu Carrie A. , Campbell Diane R.
Published: February 2008

Natural hybridization can produce individuals that vary widely in fitness, depending upon the performance of particular genotypes in a given environment. In a hybrid zone with habitat heterogeneity, differences in physiological responses to abiotic conditions could influence the fitness and spatial distribution of hybrids and parental species. This study compared gas exchange physiology ofIpomopsis aggregata,I. tenuituba, and their natural hybrids in situ and assessed whether physiological differences were consistent with their native environmental conditions. We also produced reciprocal F2s in a greenhouse study to test for cytonuclear effects on water‐use efficiency (WUE). The relative performance of natural hybrids and parentals was consistent with their native habitats:I. aggregataat the coolest, wettest locations had the lowest WUE, while hybrids from the most xeric sites had the highest WUE. In hybrids, the mechanism by which both natural and experimental hybrids achieved this high WUE depended on cytotype: those withI. tenuitubacytoplasm had reduced transpiration, while those withI. aggregatacytoplasm had an increased photosynthetic rate, consistent with patterns in the cytoplasmic parent. The high WUE in hybrids may contribute to their high survival in the dry center of the natural hybrid zone, consistent with environment‐dependent models of hybrid zone dynamics.
Flower development of Meliosma (Sabiaceae): evidence for multiple origins of pentamery in the eudicots
Authors: Wanntorp Livia , Ronse De Craene Louis P.
Published: February 2008

Flower developmental studies are a complement to molecular phylogenetics and a tool to understand the evolution of the angiosperm flower. Buds and mature flowers of Meliosma veitchiorum, M. cuneifolia, and M. dilleniifolia (Sabiaceae) were investigated using scanning electron microscopy to clarify flower developmental patterns and morphology, to understand the origin of the perianth merism, and to discuss the two taxonomic positions proposed for Sabiaceae, among rosids or in the basal grade of eudicots. Flowers in Meliosma appear pentamerous with two of the five sepals and petals strongly reduced, three staminodes alternating with two fertile stamens opposite the small petals, and a two‐carpellate gynoecium. The flower development in Meliosma is spiral without distinction between bracteoles and sepals. Because of this development, sepals, petals, and stamens are almost opposite and not alternating as expected in cyclical pentamerous flowers. In four‐sepal flowers the direction of petal initiation is reversed. The symmetry of the flower appears to be transversally zygomorphic, although this is hidden by the almost equal size of the larger petals. Evidence points to a unique pentamerous origin of flowers in Meliosma, and not to a trimerous origin, as earlier suggested, and adds support to multiple origins of pentamery in the eudicots.
Ascoma development and phylogeny of an apothecioid dothideomycete, Catinella olivacea
Authors: Greif Matthew D. , Gibas Connie Fe C. , Tsuneda Akihiko , Currah Randolph S.
Published: February 2008

Catinella olivacea is a discomycetous fungus often found fruiting within cavities in rotting logs. Because this habitat would lack the air currents upon which discomycete species normally rely for the dispersal of their forcibly ejected ascospores, we suspected an alternative disseminative strategy might be employed by this species. An examination of the development of the discomycetous ascomata in pure culture, on wood blocks, and on agar showed that the epithecium was gelatinous at maturity and entrapped released ascospores in a slimy mass. We interpreted this as an adaptation for ascospore disperal by arthropods. Developmental data also showed that C. olivacea was unusual among other discomycetes in the Helotiales (Leotiomycetes). For example, the ascoma developed from a stromatic mass of meristematically dividing cells and involved the formation of a uniloculate cavity within a structure better considered an ascostroma than an incipient apothecium. Furthermore, the ascus had a prominent ocular chamber and released its ascospores through a broad, bivalvate slit. These features, along with phylogenetic analyses of large subunit and small subunit rDNA, indicated that this unusual apothecial fungus is, surprisingly, more closely affiliated with the Dothideomycetes than the Leotiomycetes.
Widespread mycorrhizal specificity correlates to mycorrhizal function in the neotropical, epiphytic orchid Ionopsis utricularioides (Orchidaceae)
Authors: Otero J. Tupac , Flanagan Nicola S. , Herre E. Allen , Ackerman James D. , Bayman Paul
Published: February 2008

Tropical orchids constitute the greater part of orchid diversity, but little is known about their obligate mycorrhizal relationships. The specificity of these interactions and associated fungal distributions could influence orchid distributions and diversity. We investigated the mycorrhizal specificity of the tropical epiphytic orchid Ionopsis utricularioides across an extensive geographical range. DNA ITS sequence variation was surveyed in both plants and mycorrhizal fungi. Phylogeographic relationships were estimated for the mycorrhizal fungi. Orchid functional outcomes were determined through in vitro seed germination and seedling growth with a broad phylogenetic representation of fungi. Most fungal isolates derived from one clade of Ceratobasidium (anamorphs assignable to Ceratorhiza), with 78% within a narrower phylogenetic group, clade B. No correlation was found between the distributions of orchid and fungal genotypes. All fungal isolates significantly enhanced seed germination, while fungi in clade B significantly enhanced seedling growth. These results show that I. utricularioides associates with a phylogenetically narrow, effective fungal clade over a broad distribution. This preference for a widespread mycorrhizae may partly explain the ample distribution and abundance of I. utricularioides and contrasts with local mycorrhizal diversification seen in some nonphotosynthetic orchids. Enhanced orchid function with a particular fungal subclade suggests mycorrhizal specificity can increase orchid fitness.
Maternal effects of drought stress and inbreeding in Impatiens capensis (Balsaminaceae)
Authors: Riginos Corinna , Heschel M. Shane , Schmitt Johanna
Published: February 2008

Maternal effects can have substantial impacts on plant fitness and plant populations. Stressful environmental conditions can cause a maternal plant to inadequately provision its progeny, resulting in poor seedling growth, low reproductive success, and decreased competitive ability. Maternal effects consist of environmental and genetic load components, but the interactions between these two components have rarely been considered. To determine the effects of maternal drought stress and maternal inbreeding on progeny biomass (a fitness correlate) and physiological responses to drought stress, we conducted a greenhouse experiment with genetic lines from two populations (mesic site vs. dry site) of the herbaceous annual Impatiens capensis (Balsaminaceae). Seeds were collected from cleistogamous flowers of inbred or outcrossed maternal plants that were subject to either a drought or control treatment. These seeds were grown into juvenile plants that were also subject to either a drought stress or a control treatment. Plants from the mesic site had significantly reduced biomass from maternal drought stress, while plants from the dry site maintained biomass despite adverse maternal environmental conditions. Juvenile plants of both populations had reduced biomass only as a result of maternal inbreeding. Interestingly, inbreeding depression was more apparent when maternal environmental conditions were benign.
Quantifying the presence and absence of turgor for the spatial characterization of cortical senescence in roots of Triticum aestivum (Poaceae)
Authors: Bingham Ian J.
Published: February 2008

Cortical senescence is an important feature of the roots of a number of graminaceous species because it may contribute to rhizodeposition of carbon and influence the efficiency of nutrient uptake. A major limitation to understanding the physiological control of senescence and its impact on rhizosphere processes has been the lack of reliable techniques for characterizing the progress of senescence along the root. The use of a single‐cell pressure probe was evaluated for quantifying cell integrity in different regions of wheat roots. The percentage of locations with turgid cells declined with increasing distance behind the root apex. The decline preceded visible collapse of the cortex but after the loss of nuclear staining in the outer cortex. The percentage of locations with turgid cells was closely associated with root diameter, which suggests that measurements of changes in diameter, made using minirhizotrons under well‐watered conditions in the field, could provide estimates of in situ rates of cortical senescence.
Conservation genetics of an endemic and endangered epiphyticLaelia speciosa(Orchidaceae)
Authors: Ávila‐Díaz Irene , Oyama Ken
Published: February 2008

We used isozymes (16 loci in 11 enzymatic systems) fromLaelia speciosa, an endemic and endangered epiphytic orchid of Mexico, to assess the genetic diversity and population genetic structure in nine populations distributed along its geographic range, as well as to detect those populations that are genetically unique and therefore deserve high‐priority protection. On average, the genetic diversity was high (percentage of polymorphic loci,Pp= 76%, mean number of alleles per locus,A= 3.34, the average observed heterozygosityHO= 0.302, the average expected heterozygosityHE= 0.382). Moderate levels of inbreeding ( f= 0.216, 95% confidence interval = 0.029–0.381) were found. Low levels of genetic differentiation were observed among populations (θp= 0.040); however, there was a significant correlation between geographic and genetic distances among the populations (Mantel test:r2= 0.43,P< 0.05). Populations located within the same mountain range were genetically more similar. Private alleles were found, so proper management requires protection and maintenance of genetic diversity throughout its range. In case of reintroduction, we suggest using individuals propagated from seeds from as many capsules as possible, from close populations. An ex situ conservation strategy also is proposed.
Colored floral organs influence pollinator behavior and pollen transfer in Commelina communis (Commelinaceae)
Authors: Ushimaru Atushi , Watanabe Takeshi , Nakata Kensuke
Published: February 2008

Visual floral guides such as colored anthers, lines, dots, and UV‐absorption patterns on petals are commonly observed in insect‐pollinated angiosperms. Floral guides that are known to enhance foraging efficiency of visitors on flowers thus promote return visits (foraging facilitation hypothesis, which predicts that visitors will discriminate against flowers with inferior floral guides). In this study, we experimentally examined the hypothesis that floral guides also prevent pollen‐theft behavior by floral visitors (theft prevention hypothesis), which has rarely been tested. Nectarless flowers of Commelina communis have three types of brightly colored floral organs: large blue petals, rewarding yellow anthers, and nonrewarding yellow anthers. Colored floral organs were removed artificially from plants in two natural populations of C. communis. Removal of the nonrewarding yellow anthers diminished hoverings in front of flowers and tended to reduce the number of total floral visitor landings, supporting the foraging facilitation hypothesis. Additionally, removal of the rewarding yellow anther decreased the frequency of legitimate landings on flowers and the legitimate landing‐to‐total landing ratio, which is consistent with the theft prevention hypothesis. The nonrewarding anthers and the rewarding yellow anthers were shown to play an important role in increasing visitor landings and orienting floral visitors toward a landing point appropriate for pollination, respectively. We also showed that the absence of yellow anthers decreased both pollen dispatch from brown anthers and receipt by stigmas in C. communis. These findings support both the foraging facilitation hypothesis and the theft prevention hypothesis.
Comparison of whole chloroplast genome sequences to choose noncoding regions for phylogenetic studies in angiosperms: the tortoise and the hare III
Authors: Shaw Joey , Lickey Edgar B. , Schilling Edward E. , Small Randall L.
Published: February 2008

Although the chloroplast genome contains many noncoding regions, relatively few have been exploited for interspecific phylogenetic and intraspecific phylogeographic studies. In our recent evaluation of the phylogenetic utility of 21 noncoding chloroplast regions, we found the most widely used noncoding regions are among the least variable, but the more variable regions have rarely been employed. That study led us to conclude that there may be unexplored regions of the chloroplast genome that have even higher relative levels of variability. To explore the potential variability of previously unexplored regions, we compared three pairs of single‐copy chloroplast genome sequences in three disparate angiosperm lineages: Atropa vs. Nicotiana (asterids); Lotus vs. Medicago (rosids); and Saccharum vs. Oryza (monocots). These three separate sequence alignments highlighted 13 mutational hotspots that may be more variable than the best regions of our former study. These 13 regions were then selected for a more detailed analysis. Here we show that nine of these newly explored regions (rpl32‐trnL(UAG), trnQ(UUG)‐5′rps16, 3′trnV(UAC)‐ndhC, ndhF‐rpl32, psbD‐trnT(GGU), psbJ‐petA, 3′rps16–5′trnK(UUU), atpI‐atpH, and petL‐psbE) offer levels of variation better than the best regions identified in our earlier study and are therefore likely to be the best choices for molecular studies at low taxonomic levels.
Searching for the relatives of Coffea (Rubiaceae, Ixoroideae): the circumscription and phylogeny of Coffeeae based on plastid sequence data and morphology
Authors: Davis Aaron P. , Chester Michael , Maurin Olivier , Fay Michael F.
Published: February 2008

The circumscription of Coffeeae (Rubiaceae) and phylogenetic relationships within the tribe were evaluated using sequence data from four plastid regions (trnL‐F intron, trnL‐F intergenic spacer [IGS], rpl16 intron, and accD‐psa1 IGS) and a morphological data set. Eleven candidates for inclusion in Coffeeae were examined using plastid data, and a further three were investigated using morphology alone. Based on previous phylogenetic analysis of the subfamily Ixoroideae, nine genera representing five tribes were used as outgroups. Our results support an enlarged circumscription for Coffeeae, containing 11 genera, viz. Argocoffeopsis, Belonophora, Calycosiphonia, Coffea, Diplospora, Discospermum, Nostolachma, Psilanthus, Tricalysia, Sericanthe, and Xantonnea. The inclusion of Diplospora and Tricalysia within Coffeeae, based on published molecular data, and the inclusion of Argocoffeopsis, Belonophora, Calycosiphonia, Discospermum, and Sericanthe, based on morphological evidence, are well supported. Nostolachma is newly transferred from Gardenieae subtribe Diplosporinae to Coffeeae, and Xantonnea from Octotropideae to Coffeeae. The exclusion of Bertiera from Coffeeae and placement in tribe Bertiereae is supported on the basis of molecular and morphological data. The removal of Diplospora and all other genera from Gardenieae subtribe Diplosporinae to Coffeeae and Octotropideae renders Diplosporinae superfluous. It is proposed that Xantonneopsis be transferred to Octotropideae; Petitiocodon is tentatively placed in Gardenieae. The monophyly of seven genera is supported, but Coffea is identified as paraphyletic in relation to Psilanthus on the basis of molecular and combined molecular and morphological data.
Diversity of Kranz anatomy and biochemistry in C4 eudicots
Authors: Muhaidat Riyadh , Sage Rowan F. , Dengler Nancy G.
Published: February 2008

C4 photosynthesis and Kranz anatomy occur in 16 eudicot families, a striking example of convergent evolution. Biochemical subtyping for 13 previously undiagnosed C4 eudicot species indicated that 10 were NADP‐malic enzyme (ME) and three were NAD‐ME. A total of 33 C4 species, encompassing four Kranz anatomical types (atriplicoid, kochioid, salsoloid, and suaedioid), and 21 closely related C3 species were included in a quantitative anatomical study in which we found that, unlike similar studies in grasses and sedges, anatomical type had no predictive value for the biochemical subtype. In a multivariate canonical discriminant analysis, C4 species were distinguished from C3 species by the mesophyll to bundle sheath ratio and exposure of the bundle sheath surface to intercellular space. Discrimination between NADP‐ME and NAD‐ME was not significant, although in a Mantel test grouping by biochemical subtype was significant, while grouping by family was not. This comprehensive survey of C4 anatomy and biochemistry unequivocally demonstrated that atriplicoid anatomy and NADP‐ME biochemistry predominate in many evolutionary lineages. In addition to a main decarboxylating enzyme, high activity of a second decarboxylating enzyme was often observed. Notably, PEP‐carboxykinase activity was significant in a number of species, demonstrating that this enzyme could also serve as a secondary pathway for C4 metabolism in eudicots.
Key innovations in the evolution of Kranz anatomy and C4 vein pattern in Flaveria (Asteraceae)
Authors: McKown Athena D. , Dengler Nancy G.
Published: February 2008

Kranz anatomy and C4 vein pattern are required for C4 biochemical functioning in C4 plants; however, the evolutionary timing of anatomical and biochemical adaptations is unknown. From the genus Flaveria, 16 species (C3, C4, intermediates [C3–C4, C4‐like]) were analyzed, novel anatomical and vein pattern characters were analyzed and key anatomical differences among photosynthetic groups were highlighted. A stepwise acquisition of anatomical and vein pattern traits prior to derived biochemistry was outlined on the basis of the phylogeny of Flaveria. Increased vein density represents a potential “precondition” contributing to lower ratios of photosynthetic tissues (mesophyll, bundle sheath) and precedes further anatomical and biochemical modifications observed in derived C3–C4 intermediates. In derived Flaveria species, bundle sheath volume is modified through cell expansion, whereas mesophyll volume is altered through mesophyll cell expansion, reductions in the number of ground tissue layers, and increased vein density. Results demonstrated that key anatomical features of C4 plants are also required for C3–C4 biochemical intermediacy, and anatomical and biochemical alterations acquired during evolution of intermediacy may predispose a species for evolution of C4 photosynthesis. C4‐like species are similar to C4 species, demonstrating that Kranz anatomy is fully evolved before complete C4 biochemistry is achieved.
Molecular phylogenetic evidence for the origin of a diploid hybrid of Paeonia (Paeoniaceae)
Authors: Pan Jin , Zhang Daming , Sang Tao
Published: February 2008

There is growing evidence that hybridization not only by means of allopolyploidy but also at the homoploidy level was a major driving force of plant diversification. While allopolyploidy is known to be a common mode of speciation in Paeonia (Paeoniaceae), hybrid speciation at the diploid level needs further evaluation. Paeonia anomala was previously considered to be an interspecific hybrid but with an unknown ploidy level. In this study P. anomala is identified as a diploid (2n = 10). With increased sampling of populations and molecular markers, we showed that P. anomala is a homoploid hybrid that originated from a cross between P. veitchii and P. lactiflora. Five populations of P. anomala were sequenced for the following molecular markers: the matK gene and two intergenic spacers, psbA‐trnH and rps16‐trnQ, of the chloroplast genome; the internal transcribed spacers (ITS) of nuclear ribosomal DNA; and three low‐copy nuclear genes, Adh1, Adh2, and Gpat. The populations of P. anomala were grouped together with P. veitchii on the ITS and Gpat phylogenies but with P. lactiflora on the chloroplast phylogeny. Sequence polymorphism was found at the Adh1 and Adh2 loci within individuals of P. anomala. These polymorphic sequences were grouped with P. veitchii and P. lactiflora, respectively. Phenetic analysis indicated that P. anomala is morphologically similar to P. veitchii. Phenotypic evolution resulting from the combination of two diverged genomes might have occurred primarily at the physiological level and allowed P. anomala to adapt to geographic regions different from those of its parents.
Relative pollination effectiveness of floral visitors of Pitcairnia angustifolia (Bromeliaceae)
Authors: Fumero‐Cabán José J. , Meléndez‐Ackerman Elvia J.
Published: February 2008

The effectiveness of flower visitors as pollinators will determine their potential role as selective agents on flower traits. Pitcairnia angustifolia has floral characters that would fit pollination by long‐billed hummingbirds, and they should be the most effective pollinators for this plant. To test this prediction, we characterized the behavior of visitors toward flowers and their pollination effectiveness. Coereba flaveola (bananaquits) was the most frequent flower visitor and acted as a primary nectar robber; however, they pollinated incidentally and deposited pollen on stigmas. The endemic short‐billed hummingbird Chlorostilbon maugaeus behaved as a secondary robber and did not pollinate flowers. As expected, the long‐billed hummingbird, Anthracothorax viridis, was the most efficient visitor in terms of pollen deposition; however, it was the least frequent flower visitor. Introduced Apis mellifera (honeybees) were second in efficiency at depositing pollen and performed one third of the flower visits. Estimates of the expected rate of pollen deposition by each pollinator did not identify a single most effective pollinator. For P. angustifolia at least three flower visitors including an exotic bee and a nectar robber may be equally important to reproductive success. While these results limit our ability to make predictions on the role of hummingbird‐pollination on current flower evolution, they do suggest the potential for pollination redundancy among flower visitors for P. angustifolia populations.
Genotype, soil type, and locale effects on reciprocal transplant vigor, endophyte growth, and microbial functional diversity of a narrow sagebrush hybrid zone in Salt Creek Canyon, Utah
Authors: Miglia Kathleen J. , McArthur E. Durant , Redman Regina S. , Rodriguez Russell J. , Zak John C. , Freeman D. Carl
Published: February 2008

When addressing the nature of ecological adaptation and environmental factors limiting population ranges and contributing to speciation, it is important to consider not only the plant's genotype and its response to the environment, but also any close interactions that it has with other organisms, specifically, symbiotic microorganisms. To investigate this, soils and seedlings were reciprocally transplanted into common gardens of the big sagebrush hybrid zone in Salt Creek Canyon, Utah, to determine location and edaphic effects on the fitness of parental and hybrid plants. Endophytic symbionts and functional microbial diversity of indigenous and transplanted soils and sagebrush plants were also examined. Strong selection occurred against the parental genotypes in the middle hybrid zone garden in middle hybrid zone soil; F1 hybrids had the highest fitness under these conditions. Neither of the parental genotypes had superior fitness in their indigenous soils and habitats; rather F1 hybrids with the nonindigenous maternal parent were superiorly fit. Significant garden‐by‐soil type interactions indicate adaptation of both plant and soil microorganisms to their indigenous soils and habitats, most notably in the middle hybrid zone garden in middle hybrid zone soil. Contrasting performances of F1 hybrids suggest asymmetrical gene flow with mountain, rather than basin, big sagebrush acting as the maternal parent. We showed that the microbial community impacted the performance of parental and hybrid plants in different soils, likely limiting the ranges of the different genotypes.
Ecological and evolutionary determinants of a key plant functional trait: wood density and its community‐wide variation across latitude and elevation
Authors: Swenson Nathan G. , Enquist Brian J.
Published: February 2008

Wood density is an important trait in trees indicative of their life history and mechanical and physiological strategies. The following examines the evolutionary ecology of wood density using a large database for seed plants. In particular, we focused on the geographic and phylogenetic variation in wood density for both gymnosperms and angiosperms. A phylogenetic supertree was constructed for over 4600 taxa, allowing for comprehensive analyses of divergences across the seed plant phylogeny. Community‐wide means and variances for wood densities were quantified for 171 standardized forest communities. Wood density was generally highly conserved across the entire seed plant phylogeny, yet large divergences were found within the rosid clade. Geographic and community variation in wood density, however, was significantly lower in temperate and high elevation communities, dominated by gymnosperms, than in tropical lowland communities, dominated by angiosperms, suggesting an increase in trait and, to some extent, clade filtering with latitude and elevation. Together, our results support the notion that both biotic and abiotic forces have been important in the evolution of wood density as well as in controlling the observed trait mean and variance across geographic gradients.
A molecular approach to species identification of Chenopodiaceae pollen grains in surface soil
Authors: Zhou Ling‐Juan , Pei Ke‐Quan , Zhou Bo , Ma Ke‐Ping
Published: February 2008

Pollen identification and classification are important not only for palynologists, but also for systematists and ecologists. Because palynological methods for the identification of pollen in surface soil until now could resolve at best to the generic level, we have developed a molecular approach to species‐level identification of Chenopodiaceae pollen in surface soils. Surface soil samples were collected in the central area of Junggar Desert Basin, Xinjiang, China. Fresh leaves of 19 Chenopodiaceae species were sampled for DNA sequencing, establishing a database of internal transcribed spacer (ITS) regions of nuclear ribosomal DNA for Chenopodiaceae. Individual chenopod pollen grains in a soil sample were separated from the soil and the ITS1 region of each pollen grain was amplified using nested PCR and sequenced. By comparing the amplified ITS1 sequences to those in the Chenopodiaceous database, we identified the pollen in the soil samples to the level of species. The new method provides a technical reference for species identification of soil surface pollen for other families. This work is necessary for further efforts to interpret the relationship of surface soil pollen to vegetation characteristics. It also has significant potential for enhancing the ability to identify pollen in clinical airborne allergen or criminological studies.
A search for phylogenetically informative wood characters within Lecythidaceae s.l.
Authors: Lens Frederic , Baas Pieter , Jansen Steven , Smets Erik
Published: February 2008

The wood structure of 71 species representing 24 genera of the pantropical Lecythidaceae s.l., including the edible Brazil nuts (Bertholletia excelsa) and the spectacular cannon‐ball tree (Couroupita guianensis), was investigated using light and scanning electron microscopy. This study focused on finding phylogenetically informative characters to help elucidate any obscure evolutionary patterns within the family. The earliest diverging subfamily Napoleonaeoideae has mixed simple/scalariform vessel perforations, scalariform vessel‐ray pitting, and high multiseriate rays, all features that are also present in Scytopetaloideae. The wood structure ofNapoleonaeais distinct, but its supposed close relativeCrateranthusstrongly resembles Scytopetaloideae. The isolated position ofFoetidia(Foetidioideae) can be supported by a unique type of vessel‐ray pitting that is similar in shape and size to intervessel pitting (distinctly bordered, <5 μm). The more derived Planchonioideae and Lecythidoideae share exclusively simple perforations and two types of vessel‐ray pitting, but they can easily be distinguished from each other by the size of intervessel pitting, shape of body ray cells in multiseriate rays, and the type of crystalliferous axial parenchyma cells. The anatomical diversity observed is clearly correlated with differences in plant size (shrubs vs. tall trees): the percentage of scalariform perforations, as well as vessel density, and the length of vessel elements, fibers, and multiseriate rays are negatively correlated with increasing plant size, while the reverse is true for vessel diameter.
Light‐dependent leaf trait variation in 43 tropical dry forest tree species
Authors: Markesteijn Lars , Poorter Lourens , Bongers Frans
Published: February 2008

Our understanding of leaf acclimation in relation to irradiance of fully grown or juvenile trees is mainly based on research involving tropical wet forest species. We studied sun–shade plasticity of 24 leaf traits of 43 tree species in a Bolivian dry deciduous forest. Sampling was confined to small trees. For each species, leaves were taken from five of the most and five of the least illuminated crowns. Trees were selected based on the percentage of the hemisphere uncovered by other crowns. We examined leaf trait variation and the relation between trait plasticity and light demand, maximum adult stature, and ontogenetic changes in crown exposure of the species. Leaf trait variation was mainly related to differences among species and to a minor extent to differences in light availability. Traits related to the palisade layer, thickness of the outer cell wall, and Narea and Parea had the greatest plasticity, suggesting their importance for leaf function in different light environments. Short‐lived pioneers had the highest trait plasticity. Overall plasticity was modest and rarely associated with juvenile light requirements, adult stature, or ontogenetic changes in crown exposure. Dry forest tree species had a lower light‐related plasticity than wet forest species, probably because wet forests cast deeper shade. In dry forests light availability may be less limiting, and low water availability may constrain leaf trait plasticity in response to irradiance.
Climatic reconstruction at the Miocene Shanwang basin, China, using leaf margin analysis, CLAMP, coexistence approach, and overlapping distribution analysis
Authors: Yang Jian , Wang Yu‐Fei , Spicer Robert A. , Mosbrugger Volker , Li Cheng‐Sen , Sun Qi‐Gao
Published: February 2008

The reconstruction of the climate in the Miocene Shanwang basin is an important link in understanding past climate and environmental changes in East Asia. A recent study showed that the mean annual temperature (MAT) estimates derived from leaf margin analysis (LMA) and the Climate Leaf Analysis Multivariate Program (CLAMP) conflicted with and were remarkably lower than those estimated by the coexistence approach (CA). Overlapping distribution analysis (ODA), a new method introduced here, is used to reconstruct the Shanwang Miocene climate based explicitly on local plant distribution data and associated meteorological stations. The Shanwang flora (17–15.2 Ma) suggests a MAT of 10.9–14.5°C and a mean annual precipitation (MAP) of 1107.3–1880.0 mm. This result is closer to the values derived from CLAMP and LMA than that obtained by CA. This report is the first comprehensive intercomparison of foliar physiognomic and nearest living relative climate proxies in a Chinese context and provides important cross validation of results.
Cobbania corrugatagen. et comb. nov. (Araceae): a floating aquatic monocot from the Upper Cretaceous of western North America
Authors: Stockey Ruth A. , Rothwell Gar W. , Johnson Kirk R.
Published: February 2008

The fossil record of aquatic flowering plants broadens our understanding of their former diversity and origins from terrestrial ancestors. This paper describes a floating aquatic monocot from 71 whole plants and several isolated leaf fragments from Upper Cretaceous oxbow lake sediments in the Dinosaur Park Formation, Alberta, Canada. The new material is represented by rosettes of leaves and roots attached to short stems that are interconnected by stolons and corresponds to the fossil aroid originally described asPistia corrugataLesquereux. Up to six plants have been found interconnected on a single slab suggesting that these plants grew in extensive floating mats covering lakes and calm stretches of rivers. Stems have up to six leaves and large numbers of branched aquatic roots. The leaf is trumpet‐shaped with an elongate clasping petiole, large aerenchymatous base, and a nearly circular blade rim. Leaf bases are often filled with sediment giving the leaf the appearance of having a basal pouch. Petioles have 6–9 veins that divide into an upper and lower set, and veins converge at an apical notch. A submarginal collective vein and at least two marginal veins with branching veins form the leaf rim. A series of dichotomizing and anastomosing veins characterize the adaxial leaf surface. Tertiary and quaternary veins form polygonal areolae. Leaf surfaces are covered in trichomes that, like those inPistia stratiotes, probably aided in buoyancy. A reconstruction of the plant is presented. Based on unique leaf morphology, these fossil plants are clearly not assignable to the genusPistiaand are described asCobbania corrugata(Lesquereux) Stockey, Rothwell et Johnson gen. et comb. nov. Recent systematic analyses using molecular characters resolve two separate origins of floating aquatic aroids included in the duckweeds and the genusPistia. This new fossil genus increases our understanding of colonization of aquatic habitats by revealing a third possible origin of the floating aquatic habit within Araceae.
Hawkmoth pollination of aerangoid orchids in Kenya, with special reference to nectar sugar concentration gradients in the floral spurs
Authors: Martins Dino J. , Johnson Steven D.
Published: February 2008

The African orchid flora has a high proportion of species with long‐spurred white flowers. Few data exist to test the prediction that this floral syndrome pattern reflects an important role for hawkmoth pollination in the evolution and ecology of these orchids. The pollination biology of five aerangoid orchid species (Rangaeris amaniensis,Aerangis brachycarpa,A. confusa,A. thomsonii, andA. kotschyana) was investigated in Kenya. Four of these have long spurs (>10 cm) and were pollinated byAgrius convolvuliandCoelonia fulvinotata.Aerangis confusa, which has relatively short spurs (ca. 4 cm), was pollinated by the short‐tongued hawkmothsHippotion celerioandDaphnis nerii. Nectar frequently filled the entire spur in some of the study species, even at anthesis. Sugar concentration of the nectar of four species was found to vary from ca. 1% at the mouth of the spur to 20% at the tip. Gradients were expressed more strongly in species with long, straight spurs. Species with spirally twisted spurs showed both steep and shallow nectar gradients. These gradients, previously unknown in plants, may function as a “sugar trail,” enticing long‐tongued hawkmoths to probe deeply into spurs without incurring the cost of filling an entire spur with concentrated nectar. In addition, the most concentrated nectar is kept out of reach of short‐tongued pollinators.
Transfer of glyphosate resistance: evidence of hybridization in Conyza (Asteraceae)
Authors: Zelaya Ian A. , Owen Micheal D. K. , VanGessel Mark J.
Published: February 2008

Transfer of herbicide resistance genes between crops and weeds is relatively well documented; however, far less information exists for weed‐to‐weed interactions. The hybridization between the weedy diploids Conyza canadensis (2n = 18) and C. ramosissima (2n = 18) was investigated by monitoring transmission of the allele conferring resistance to N‐phosphonomethyl glycine (glyphosate). In a multivariate quantitative trait analysis, we described the phylogenic relationship of the plants, whereas we tested seed viability to assess potential postzygotic reproductive barriers (PZRB) thus affecting the potential establishment of hybrid populations in the wild. When inflorescences were allowed to interact freely, approximately 3% of C. ramosissima or C. canadensis ova were fertilized by pollen of the opposing species and produced viable seeds; >95% of the ova were fertilized under no‐pollen competition conditions (emasculation). The interspecific Conyza hybrid () demonstrated an intermediate phenotype between the parents but superior resistance to glyphosate compared to the resistant C. canadensis parent. Inheritance of glyphosate resistance in the selfed () followed the partially dominant nuclear, single‐gene model; backcrosses confirmed successful introgression of the resistance allele to either parent. Negligible PZRB were observed in the hybrid progenies, confirming fertility of the C. canadensis × C. ramosissima nothotaxa. The implications of introgressive hybridization for herbicide resistance management and taxonomy of Conyza are discussed.