bluuebunny/crossref_metadata_2025 huggingface dataset:
The criteria for biomass partitioning of the current shoot: water transport versus mechanical support
Authors: Taneda Haruhiko , Tateno Masaki
Published: February 2008

In this study, we determine the theoretical criteria for biomass partitioning into the leaf and stem of the current shoot, using two quantitative models. The water transport model, based on the biochemical model of CO2 assimilation, predicts the relationship between the water transport capacity per biomass investment in the stem (stem mass specific conductivity) and the partitioning of biomass that maximizes shoot productivity. The mechanical support model, based on Euler's buckling formula, predicts the relationship between the mechanical strength per biomass investment in the stem (the inverse relationship of stem mass density) and the partitioning of biomass to avoid mechanical failures such as lodging. These models predict the stem properties of mass specific conductivity and stem mass density that result in optimum partitioning just sufficient to provide adequate water transport and static mechanical support. In reality, the stem properties of plants differ from those predicted for optimum partitioning: the partitioning of biomass in the current shoot of both angiosperms and gymnosperms is mainly governed by the mechanical support criterion, although gymnosperms are probably more affected by the water transport criterion. This tendency is supported by actual measurements of biomass partitioning in plants.
Chemical composition of anther volatiles in Ranunculaceae: genera‐specific profiles in Anemone, Aquilegia, Caltha, Pulsatilla, Ranunculus, and Trollius species
Authors: Jürgens Andreas , Dötterl Stefan
Published: February 2008

Anther volatiles of 12 Ranunculaceae species distributed in six genera (Anemone, Aquilegia, Caltha, Pulsatilla, Ranunculus, and Trollius) were investigated by thermal desorption of anthers in quartz microvials inserted into a modified injector. Chemical analysis (GC‐MS) yielded a total of 116 compounds from which 103 compounds could be identified. A great diversity of compounds was observed, including aliphatic compounds, aromatics, mono‐ and sesquiterpenoids, and nitrogen‐bearing compounds. Intraspecific variation in the chemical profiles was significantly lower than interspecific variation. Eight compounds explained 96.1% of the observed total variation between the taxa: protoanemonin, octanal, (E,E)‐α‐farnesene, 2‐phenyl ethanol, pentadecane, α‐muurolene, phenyl acetaldehyde, and linalool oxide (pyranoid) were either present only in specific taxa or varied greatly in their relative amount between the taxa. An analysis of the scent data using the chord‐normalized expected species shared (CNESS) distances of chemical profiles of the species, followed by visualization of the data with nonmetric multidimensional scaling (NMDS) showed that most species belonging to the same genus have similar chemical compositions. The differences in the chemical composition of anther volatiles are discussed with respect to the taxonomy and pollination biology of the species.
Heterogeneous reflected light influences asymmetry in leaf anatomy and gas exchange
Authors: Greaver Tara L. , Herbert Thomas J.
Published: February 2008

Soil and vegetative groundcovers reflect light heterogeneously in habitats lacking a continuous overhead canopy, however the effects of reflected light on vegetation in these habitats has received little attention. We test the hypothesis that reflected light flux affects leaf optical properties, anatomy, and photosynthesis of Ipomoea pes‐caprae (Convolvulacae), a common sand dune vine with functionally symmetric leaves, by comparing leaves growing over patches of high and low reflected light flux. Patches of high reflected light were found directly over sand and reflected 26.0 ± 0.9% (mean ± 1 SE) of incident photosynthetically active radiation (PAR) while patches of low reflected light were found over vegetation and reflected 6.1 ± 0.7% of incident PAR. Using a novel in situ method to simultaneously illuminate and measure gas exchange of one leaf surface at a time, we show that abaxial surface photosynthetic maxima and palisade parenchyma in sand patches were, respectively, 2.6 times greater and 20% thicker than those found over vegetation patches. Our results suggest that reflected light strongly influences leaf anatomy and gas exchange of I. pes‐caprae, demonstrating that reflected light can be an important component of the light environment for vegetation of habitats characterized by high‐albedo substrates.
Population genetic diversity of the clonal plantGeum reptans(Rosaceae) in the Swiss Alps
Authors: Pluess Andrea R. , Stöcklin Jürg
Published: February 2008

In the alpine landscape most plant populations are spatially isolated due to extreme patchiness and strong natural fragmentation. We used RAPD‐PCR (randomly amplified polymorphic DNA polymerase chain reaction) for a study of the genetic diversity within and among 20 populations ofGeum reptans, an outcrossing clonal plant species in the Swiss Alps. Populations were sampled at different altitudes, in early‐, medium‐ and late‐successional habitats (population origin) using a spatially hierarchical design, with distances among populations ranging from 0.2 to 208 km. Seed and pollen dispersibility was estimated by direct measurements. Seed dispersibility by wind was low with only 0.015% of the seeds flying over 100 m. Observed pollen flow was even more restricted. Molecular diversity within populations was irrespective of population origin (He= 0.22 ± 0.004) and similar to the average of other RAPD studies. Contrary to our expectation, populations were only moderately differentiated (Gst= 0.14). However, there was a clear spatial genetic structure and a positive relationship between pairwise genetic and geographic distances. Our results indicate considerable gene flow among populations within the same regional area, and we found no indication for genetic depletion during succession or in peripheral habitats. We conclude that, despite the high natural fragmentation and the importance of vegetative reproduction in this alpine plant, gene flow and repeated seedling recruitment during succession might be more frequent than commonly suggested.
Temporal changes in calyx tube length of Clematis stans (Ranunculaceae): a strategy for pollination by two bumble bee species with different proboscis lengths
Authors: Dohzono Ikumi , Suzuki Kazuo , Murata Jin
Published: February 2008

We examined the adaptive significance of a temporal decrease in the calyx tube length of Clematis stans, a dioecious species pollinated by Bombus diversus (long proboscis) and B. honshuensis (short proboscis). We compared visitation frequency, pollen removal, pollen deposition, and fruit set after a single visit among three flower stages, differentiated by calyx tube length. Bombus diversus frequently visited and removed significantly more pollen from long flowers. Bombus honshuensis visited and tended to remove more pollen from short flowers. Both pollinators deposited more pollen in short flowers, resulting in higher fruit set. These results indicate that size correspondence between the proboscis and the calyx tube enhances visitation frequency and pollen removal, but not pollen deposition. Because a single visit does not fertilize all ovules of a flower, multiple visits by two bumble bee species may increase seed production and genetic diversity of offspring. By temporally changing calyx tube length, C. stans can use two bumble bee pollinators and maintain specialized relationships with each. This strategy may be adaptive when the pollinator fauna fluctuates, and is economical because it eliminates costs required to produce different types of flowers. This constitutes a novel pattern of temporal specialization in flower‐pollinator relationships.
De novo variation in life‐history traits and responses to growth conditions of resynthesized polyploid Brassica napus (Brassicaceae)
Authors: Schranz M. Eric , Osborn Thomas C.
Published: February 2008

Variation that arises in generations immediately following polyploidization may be important for the establishment, adaptation, and persistence of new polyploid species. We previously showed divergence for flowering time among lines from a resynthesized Brassica napus allopolyploid lineage derived from a cross of diploid B. rapa and B. oleracea. In this study, we more fully assess phenotypic differentiation of lines from the previously studied lineage and of lines derived from an additional resynthesized B. napus lineage. Nine polyploid lines and their diploid parents were grown under four growth conditions and measured for eight life‐history traits. Polyploid lines within a lineage were expected to be genetically identical because they were derived from individual, chromosome‐doubled amphihaploid plants. However, significant differences were found among lines within lineages for every phenotypic trait measured and in response to different growth conditions (genotype by environment interactions). When phenotypes of each polyploid line for each trait in each environment were compared with their diploid progenitors, approximately 30% were like one or the other parent, 50% were intermediate, and 20% were transgressive. Our results demonstrate extensive de novo variation in new polyploid lineages. Such changes could contribute to the evolutionary potential in naturally occurring polyploids.
The reproductive biology of Sophora fernandeziana (Leguminosae), a vulnerable endemic species from Isla Robinson Crusoe
Authors: Bernardello Gabriel , Aguilar Ramiro , Anderson Gregory J.
Published: February 2008

Sophora fernandeziana is the only legume endemic to Isla Robinson Crusoe (Archipelago Juan Fernández, Chile); it is uncommon and becoming rare. Although its preservation status is listed as “vulnerable,” as with many species, little is known of its reproductive biology. Flowering phenology, floral morphology, nectar features, breeding system, and visitors were analyzed in two populations. Flowering is from late winter to early spring. Flowers last 6 d and have a number of ornithophilous features. A floral nectary begins to secrete highly concentrated nectar 48 h after flowers open. Nectar secretion increases as the flower ages but culminates in active nectar reabsorption as the flower senesces. Nectar production is negatively affected by nectar removal. Self‐pollen germinates and tubes grow down the style. However, pollen tubes were only observed to enter the ovaries in open pollinated styles, suggesting the possibility of an ovarian self‐incompatibility mechanism. Both sexes of the two hummingbird species that inhabit the island are regular visitors. Low fruit and seed set, low genetic diversity, and a shrinking number of populations all contribute to increased concern about the future of this species—and perhaps the hummingbirds that depend on it.
Phylogeny and biogeography of Caltha (Ranunculaceae) based on chloroplast and nuclear DNA sequences
Authors: Schuettpelz Eric , Hoot Sara B.
Published: February 2008

The genus Caltha (Ranunculaceae) consists of 10 species of low‐growing, perennial herbs distributed throughout the moist temperate and cold regions of both the Northern and Southern Hemispheres. Traditionally, the species have been divided into two sections: section Psychrophila in the Southern Hemisphere with diplophyllous leaves and section Caltha in the Northern Hemisphere with leaves lacking inflexed appendages. This study uses chloroplast and nuclear DNA sequences to determine the relationships among the 10 species, test the monophyly of sections Psychrophila and Caltha, trace the evolutionary history of diplophylly, and explore biogeographical hypotheses for the genus. Analysis of these data resulted in a well‐resolved and well‐supported phylogeny. Section Psychrophila (C. sagittata, C. appendiculata, C. dionaeifolia, C. obtusa, C. introloba, and C. novae‐zelandiae) was resolved as monophyletic, indicating a single origin of diplophylly. The species of section Caltha (C. natans, C. scaposa, C. palustris, and C. leptosepala) formed a paraphyletic grade. The resulting phylogeny strongly supports a Northern Hemisphere origin for Caltha, followed by dispersal to the Southern Hemisphere (Gondwanaland). A vicariance model is invoked to explain present‐day distributions in South America, Australia, and New Zealand.
The floral biology of Curcumorpha longiflora (Zingiberaceae): a ginger with two‐day flowers
Authors: Gao Jiang‐Yun , Zhang Ling , Deng Xiao‐Bao , Ren Pan‐Yu , Kong Ji‐Jun , Li Qing‐Jun
Published: February 2008

Curcumorpha longiflora is a perennial chasmophyte (rock fissure plant) ginger that usually grows in crevices of calcareous rocks and forms patches on the understory of limestone monsoon rainforests. The pollination ecology of C. longiflora was studied by monitoring phenology and flowering behavior, observing pollinator activity (frequency and behavior of visitors), and the quantity and quality of pollination services. We also investigated the germination of pollen grains and growth of pollen tubes after different pollination treatments to detect its breeding system. Based on the results: (1) for the first time in Zingiberaceae a new protandrous mechanism was found with a two‐day flowering to avoid autogamy in this species; (2) under field conditions, all individuals of C. longiflora usually produced only one flower every other day to keep geitonogamy to a minimum; (3) germination of pollen grains and growth rates of pollen tubes under different pollination treatments were the same 4 h later after pollination, suggesting that C. longiflora is completely self‐compatible; (4) among the limited visitors, Bombus sp. and Apis florae were effective pollinators, but they were active at different times and at different stages of the flower, probably receiving different rewards.
Biomechanics and anatomy of Lycopersicon esculentum fruit peels and enzyme‐treated samples
Authors: Matas Antonio J. , Cobb Edward D. , Bartsch James A. , Paolillo Dominick J. , Niklas Karl J.
Published: February 2008

We report the biomechanics and anatomy of fruit wall peels (before and after cellulase/pectinase treatment) from two Lycopersicon esculentum cultivars (i.e., Inbred 10 and Sweet 100 cherry tomatoes). Samples were tested before and after enzyme treatment in uniaxial tension to determine their rate of creep, plastic and instantaneous elastic strains, breaking stress (strength), and work of fracture. The fruit peels of both cultivars exhibited pronounced viscoelastic and strain‐hardening behavior, but differed significantly in their rheological behavior and magnitudes of material properties, e.g., Inbred 10 peels crept less rapidly and accumulated more plastic strains (but less rapidly), were stiffer and stronger, and had a larger work of fracture than Sweet 100 peels. The cuticular membrane (CM) also differed; e.g., Sweet 100 CM strain‐softened at forces that caused Inbred 10 to strain‐harden. The mechanical behavior of peels and their CM correlated with anatomical differences. The Inbred 10 CM develops in subepidermal cell layers, whereas the Sweet 100 CM is poorly developed below the epidermis. Based on these and other observations, we posit that strain‐hardening involves the realignment of CM fibrillar elements and that this phenomenon is less pronounced for Sweet 100 because fewer cell walls contribute to its CM compared to Inbred 10.
Post‐glacial history ofTrillium grandiflorum(Melanthiaceae) in eastern North America: inferences from phylogeography
Authors: Griffin Steven R. , Barrett Spencer C. H.
Published: February 2008

Dispersal and migration are important processes affecting the evolutionary history and genetics of species. Here we investigate post‐glacial migration and gene flow inTrillium grandiflorum(Melanthiaceae), a wide‐ranging, forest herb from eastern North America. Using phylogeographic approaches, we examined cpDNA and allozyme diversity in 35 populations ofT. grandiflorumsampled from throughout the geographic range of the species. Nested clade analysis (NCA) of cpDNA haplotypes indicated thatT. grandiflorumlikely survived in two refugia in the southeastern US during the last glaciation and that long‐distance dispersal characterized the post‐glacial recolonization of northern areas. There was no evidence for reduced allozyme diversity in populations from glaciated compared to ice‐free regions, probably because of the greater abundance and larger effective size of populations in the north. An analysis of isolation‐by‐distance based on the allozyme data suggested a pattern of population differentiation consistent with restricted gene flow. Notwithstanding the significance of rare seed dispersal events for migration, a comparison of allozyme and cpDNA genetic structure indicates that pollen flow between populations is more likely than seed dispersal. These results forT. grandiflorumrepresent the first phylogeographic analysis of a temperate woodland herb in eastern North America and support the importance of occasional long‐distance dispersal events in the post‐glacial migration of plants.
Intergeneric and infrafamilial phylogeny of subfamily Monsteroideae (Araceae) revealed by chloroplast <011>trnL‐F sequences
Authors: Tam Sheh‐May , Boyce Peter C. , Upson Tim M. , Barabé Denis , Bruneau Anne , Forest Felix , Parker John S.
Published: February 2008

The chloroplast trnL‐F region was used as an independent data set for phylogenetic analysis of 118 aroid taxa. We investigated the intergeneric relationships of subfamily Monsteroideae (Araceae) and used this as a basis for an interspecific phylogenetic study of Rhaphidophora Hassk., the largest genus of the Monsteroideae. Results of the molecular tree were useful for inferring subfamilial and tribal circumscription and evolution in Araceae. Our results show that family Araceae consists of five clades that correspond to the subfamilies traditionally recognized. Starting from the most basal clade, these correspond to subfamilies Gymnostachydoideae and Orontioideae (proto aroids), with Lemna sp. (Lemnaceae) embedded in the Araceae and sister to the true aroids consisting of Pothoideae sister to Monsteroideae, immediately sister to Lasioideae and Aroideae. There is less agreement with existing tribal classifications. Complex relationships exist between members of the Monsteroideae. Our results show that Rhaphidophora and Epipremnum are paraphyletic with species of Rhaphidophora sampled, forming three informal groups with other genera of the Monstereae. Phylogenetic results may be used to suggest taxonomic changes to the current systematics of the monsteroids.
Natural selection favors rapid reproductive phenology in Potentilla pulcherrima (Rosaceae) at opposite ends of a subalpine snowmelt gradient
Authors: Stinson Kristina A.
Published: February 2008

In high altitude plants, flowering quickly ensures reproductive success within a short snow‐free period, but limits maturation time and fecundity. Natural selection on prefloration intervals may therefore vary in contrasting snowmelt environments and could influence the outcome of phenological responses to climatic change. This study investigated adaptive differentiation and plasticity of prefloration intervals in the subalpine perennial Potentilla pulcherrima. Three years of in situ field observations were combined with phenotypic selection analyses and a common garden experiment. Plants from high, intermediate, and low altitudes expressed similar prefloration intervals and plasticity when grown at common altitude, indicating no evidence for adaptive differentiation. Selection on the prefloration interval was negative at both low and high altitudes before and after accounting for strong positive selection on size. Environmental differences between high and low altitudes indicated that long, dry seasons and short, wet seasons both favored rapid reproduction. Therefore, quicker reproduction was adaptive in response to late snowmelt, but slower reproduction in response to earlier snowmelt appeared to be maladaptive. Selection differed marginally between late snowmelt years and dry ones. Plastic responses to future precipitation patterns may therefore have positive or negative effects on fitness within a single species, depending upon altitude and year.
Genetic diversity in harvested and protected populations of wild American ginseng,Panax quinquefoliusL. (Araliaceae)
Authors: Cruse‐Sanders Jennifer M. , Hamrick J. L.
Published: February 2008

Genetic diversity was examined at 16 allozyme loci in 21 wild populations of the medicinal plant American ginseng,Panax quinquefoliusL. (Araliaceae). This species has been harvested from forests in North America for more than 250 years. Average expected heterozygosity was significantly greater within protected populations (He= 0.076) than within populations in which harvesting was permitted (He= 0.070). More notably, genetic structure was greater among unprotected populations (GST= 0.491) than among protected populations (GST= 0.167). These differences in the level and distribution of genetic diversity in American ginseng populations indicate that harvesting may have significant evolutionary implications for this species. Age class structure also shifted toward smaller, nonreproductive plants in unprotected populations. Juvenile plants had lower genetic diversity (He= 0.067) than reproductive plants (He= 0.076) suggesting that conserving a proportion of the largest (oldest) plants in each population is important to protect reproductive fitness and the evolutionary potential of the species. Due to its high genetic structure, conservation recommendations include protecting populations throughout the range ofP. quinquefolius.
Growth, nitrogen uptake, and metabolism in two semiarid shrubs grown at ambient and elevated atmospheric CO2 concentrations: effects of nitrogen supply and source
Authors: Causin Humberto Fabio , Tremmel David C. , Rufty Thomas W. , Reynolds James F.
Published: February 2008

The effect of differences in nitrogen (N) availability and source on growth and nitrogen metabolism at different atmospheric CO2 concentrations in Prosopis glandulosa and Prosopis flexuosa (native to semiarid regions of North and South America, respectively) was examined. Total biomass, allocation, N uptake, and metabolites (e.g., free NO3−, soluble proteins, organic acids) were measured in seedlings grown in controlled environment chambers for 48 d at ambient (350 ppm) and elevated (650 ppm) CO2 and fertilized with high (8.0 mmol/L) or low (0.8 mmol/L) N (Nlevel), supplied at either 1 : 1 or 3 : 1 NO3− : NH4+ ratios (Nsource). Responses to elevated CO2 depended on both Nlevel and Nsource, with the largest effects evident at high Nlevel. A high NO3− : NH4+ ratio stimulated growth responses to elevated CO2 in both species when N was limiting and increased the responses of P. flexuosa at high Nlevel. Significant differences in N uptake and metabolites were found between species. Seedlings of both species are highly responsive to N availability and will benefit from increases in CO2, provided that a high proportion of NO3‐ to NH4‐N is present in the soil solution. This enhancement, in combination with responses that increase N acquisition and increases in water use efficiency typically found at elevated CO2, may indicate that these semiarid species will be better able to cope with both nutrient and water deficits as CO2 levels rise.
Correlation between distyly and ploidy level in Damnacanthus (Rubiaceae)
Authors: Naiki Akiyo , Nagamasu Hidetoshi
Published: February 2008

Somatic chromosomes were observed in 661 individuals of 14 taxa, nine species and five varieties, of Damnacanthus (Rubiaceae). Chromosome numbers are reported for the first time for 13 taxa. Diploid (2n = 22) and tetraploid (2n = 44) counts were obtained. Distyly is reported for the first time for four species, D. angustifolius, D. henryi, D. labordei, and D. officinarum. A strong correlation exists between chromosome number and occurrence of distyly. Regardless of taxa in Damnacanthus, distylous populations are diploid, and monomorphic populations are tetraploid. Flowers of the monomorphic populations observed have a long style and short stamens with few exceptions. Polyploidization may have caused the breakdown of distylous to monomorphic flowers. In D. indicus, leaves from the tetraploid populations tend to be larger than those from the diploid populations. Populations of tetraploid D. indicus were distributed in more northern areas than those of the diploid. Three types of sympatric distribution were found for the varieties of D. indicus in Japan: diploid and tetraploid, two diploids, and two tetraploids. Based on the present chromosome number study, the taxonomy of the varieties of D. indicus should be revised.
Self‐pollination in island and mainland populations of the introduced hummingbird‐pollinated plant,Nicotiana glauca(Solanaceae)
Authors: Schueller Sheila K.
Published: February 2008

Traits associated with self‐pollination are common in island plants. This pattern could simply reflect the vestige of selection during colonization. Alternatively (or in addition), the ability to self‐pollinate may provide a reproductive assurance benefit in established island plant populations due to inferior island pollinator service. To test these alternatives I studied an introduced plant (Nicotiana glauca; Solanaceae) on the California mainland and on two Channel Islands colonized at different times (approximately 30 and 100 yr ago). I compared these populations in terms of (1) capacity for self‐pollination (self‐compatibility, autogamy, stigma–anther distance, and incidence of a crumpled floral morph) and (2) current selection for the ability to self‐pollinate (pollinator service by hummingbirds and the effect of emasculation on reproductive success). In general, island plants exhibited a higher capacity for self‐pollination than mainland plants, especially on the most recently colonized island. However, island plants were not visited less frequently or more variably, nor did I detect current selection for selfing on islands. This supports the hypothesis that selfing traits in island plants are the product of a filter to successful establishment during colonization and not of selection for selfing in established island populations.
Seedling recruitment and survival of an endangered limestone endemic in its natural habitat and experimental reintroduction sites
Authors: Maschinski Joyce , Baggs Joanne E. , Sacchi Christopher F.
Published: February 2008

The largest and most fecund population of the endangered Purshia subintegra is restricted to limestone mesas in Verde Valley, Arizona, USA, where habitat destruction is imminent. To examine factors limiting its distribution and potential for expansion, we compared recruitment and survival of seedlings growing in soils from occupied and unoccupied habitat in caged field experiments and compared survival of caged and wild seedling cohorts from 1998 to 2003. In field tests, seeds germinated in soils from occupied and unoccupied habitats. Seedling survival, however, was greatest in currently occupied habitat and dropped to zero in some unoccupied habitats with the onset of severe drought. Among 16 factors measured, soil moisture significantly explained between 62% and 71% of the variation in recruitment in both wild and caged plots. Shrubs conferred protection to wild seedlings, but decreased caged seedling survival. For 5 yr following germination, caged seedlings had greater survival than natural seedling cohorts indicating that reintroduction was comparatively more successful than natural recruitment. Expansion of P. subintegra into novel habitats is limited by soil moisture capacity, and this condition varied during the experimental time frame. Reintroductions to limestone mesas are possible and most promising if cages and supplemental watering are used.
On the origin of the fig: phylogenetic relationships of Moraceae from ndhF sequences
Authors: Datwyler Shannon L. , Weiblen George D.
Published: February 2008

The majority of species in the mulberry family (Moraceae) are figs (Ficus), marked by a specialized inflorescence (syconium) and an obligate mutualism with pollinating fig wasps. Because of the unique morphology of the syconium, it has been difficult to investigate the evolutionary position of the fig. We sequenced the chloroplast gene ndhF to examine relationships in Moraceae and to elucidate shifts in reproductive traits. The reclassification of tribes is warranted, and the limits of Artocarpeae, Moreae, and Castilleae are revised to reflect evolutionary relationships. The results point to ancestral dioecy in Moraceae and multiple origins of monoecy, androdioecy, and gynodioecy. Ancestral wind pollination gave way to insect pollination at least twice. Strong support for the sister‐group relationship of a revised Castilleae with Ficus suggests that entomophily and involucral bracts encircling the flowers preceded the evolution of the syconium. Bracts surround flowers in Castilleae only during early development, but in Ficus the involucre and the receptacle enclose the fruit as well. Molecular dating suggests that fig pollination is at least 80–90 million years old. The diversity of Ficus relative to its sister group is a likely consequence of ancient specialization and cospeciation with pollinating fig wasps.
Anatomy of the vessel network within and between tree rings of Fraxinus lanuginosa (Oleaceae)
Authors: Kitin Peter B. , Fujii Tomoyuki , Abe Hisashi , Funada Ryo
Published: February 2008

The three‐dimensional (3‐D) arrangement of vessels and the vessel‐to‐vessel connections in the secondary xylem of the stem of the ring‐porous hardwood tree Fraxinus lanuginosa were studied in series of thick transverse sections with epifluorescence microscope and confocal laser scanning microscope. Vessels were traced in sequential sections, and vessel networks were reconstructed in two segments of wood with dimensions of 2 × 1.4 × 21.2 mm3 and 2 × 1.4 × 5.8 mm3 (tangential × radial × axial). The arrangement of vessels and intervessel pits were visualized by scanning electron microscopy in low‐density polyethylene microcasts and on exposed tangential faces of growth‐ring boundaries. The vessels deviated from the stem axis in the tangential direction and, to a lesser extent, in the radial direction. Some neighboring vessels were twisted around each other. Vessels that appeared solitary in single sections were found to be sequentially contiguous with a number of other vessels, forming networks that extended in the tangential direction and across growth‐ring boundaries. In the 21.2‐mm wood block, all earlywood vessels at the growth‐ring boundary made contact with latewood vessels in the previous tree ring. Within a growth ring however, only a single contact was observed between individual earlywood and latewood vessels. Densely arranged intervessel pits were characteristic in the regions where adjacent vessels made contact with each other. Such bordered pits were abundant in the tangential walls of vessel elements adjacent to growth‐ring boundaries. Therefore, bordered pits appear to provide the pathway for the radial transport of water via the vessel network across growth‐ring borders. Fiber‐tracheids, observed as terminal cells in the tree rings, might also contribute to the apoplastic transfer of water across ring borders.
Correlation between molecular markers and adaptively significant genetic variation in Bromus tectorum (Poaceae), an inbreedingannual grass
Authors: Ramakrishnan Alisa P. , Meyer Susan E. , Waters Jennifer , Stevens Mikel R. , Coleman Craig E. , Fairbanks Daniel J.
Published: February 2008

Single sequence repeat (SSR) and amplified fragment length polymorphic (AFLP) molecular marker genotypes in cheatgrass (Bromus tectorum) were compared to published data on phenotypic variation in seed dormancy, vernalization requirement, and resistance to the pathogen Ustilago bullata. Several features of cheatgrass facilitated this study: it is a recent invader in the western United States, has considerable phenotypic polymorphism, and is an obligate self‐pollinator. Forty self‐pollinating lines from four populations common to the three phenotypic data sets were analyzed for molecular genetic variation using seven SSR loci and 31 AFLP loci. We examined correlations between distance matrices using the Mantel test for each pair of studies. The two molecular data sets were significantly correlated (r = 0.636). The AFLP markers often distinguished among several lines with identical SSR genotypes. The AFLP data were also significantly correlated with the phenotypic data (r values from 0.4640 to 0.5658), but the SSR data were much more highly correlated (r values from 0.677 to 0.844). The difference between molecular marker systems was especially notable when an outlier population from Potosi Pass, Nevada, was excluded from the analysis. These results suggest that SSR markers may be good surrogates for phenotypic traits in population genetic studies of strongly inbreeding species such as cheatgrass.
Diploid and polyploid cytotype distribution inMelampodium cinereumandM. leucanthum(Asteraceae, Heliantheae)
Authors: Stuessy Tod F. , Weiss‐Schneeweiss Hanna , Keil David J.
Published: February 2008

Previous chromosomal studies withinMelampodium(Asteraceae, Heliantheae) of Mexico and Central America have documented chromosome numbersn= 9, 10, 11, 12, 18, 20, 23, 25 ± 1, 27, 30, and 33. Some species also have been shown to exhibit infra‐ and interpopulational polyploidy. The presence of cytotype mixtures is especially pronounced in the white‐rayed complex, which occurs in the southwestern United States and adjacent Mexico. This group includesM. cinereum(n= 10 and 20),M. leucanthum(n= 10 and 20), andM. argophyllum(n= 30). Cytotype distribution has been newly analyzed in 415 plants from 152 populations and added to existing data from 185 plants from 113 populations, yielding information from a total of 600 individuals from 265 populations. WithinM. cinereumandM. leucanthumare parapatric distributions of cytotypes, with tetraploids centered in the eastern and diploids in the western portions of their ranges. Tetraploids are most likely of autopolyploid origin, forming recurrently, with adaptations that allow colonization and establishment in new ecological regions. Contact zones are relatively narrow and only two triploid individuals have been detected. The tetraploid cytotypes probably extended eastward into central and southern Texas to the natural barriers at the edge of the Edward's Plateau inM. leucanthumand the low sandy plains inM. cinereum. The hexaploidM. argophyllumis interpreted as a relict surviving in the low mountains of northern Mexico; it may be an allopolyploid of hybrid origin between ancestors of the evolutionary lines that eventually yieldedM. cinereumandM. leucanthum.
Phylogenetic reconstruction of the evolution of stylar polymorphisms in Narcissus (Amaryllidaceae)
Authors: Graham Sean W. , Barrett Spencer C. H.
Published: February 2008

We investigated the origin of stylar polymorphisms in Narcissus, which possesses a remarkable range of stylar conditions and diverse types of floral morphology and pollination biology. Reconstruction of evolutionary change was complicated by incomplete resolution of trees inferred from two rapidly evolving chloroplast regions, but we bracketed reconstructions expected on the fully resolved plastid‐based tree by considering all possible resolutions of polytomies on the shortest trees. Stigma‐height dimorphism likely arose on several occasions in Narcissus and persisted across multiple speciation events. As proposed in published models, this rare type of stylar polymorphism is ancestral to distyly. While there is no evidence in Narcissus that dimorphism preceded tristyly, a rapid transition between them may explain the lack of a phylogenetic footprint for this evolutionary sequence. The single instances of distyly and tristyly in Narcissus albimarginatus and N. triandrus, respectively, are clearly not homologous, an evolutionary convergence unique to Amaryllidaceae. Floral morphology was likely an important trigger for the evolution of stylar polymorphisms: Concentrated‐changes tests indicate that a long, narrow floral tube may have been associated with the emergence of stigma‐height dimorphism and that this type of tube, in combination with a deep corona, likely promoted, or at least was associated with, the parallel origins of heterostyly.
Molecular cytogenetic analysis of recently evolvedTragopogon(Asteraceae) allopolyploids reveal a karyotype that is additive of the diploid progenitors
Authors: Pires J. Chris , Lim K. Yoong , Kovarík Ales , Matyásek Roman , Boyd Amy , Leitch Andrew R. , Leitch Ilia J. , Bennett Michael D. , Soltis Pamela S. , Soltis Douglas E.
Published: February 2008

Tragopogon mirusandT. miscellus(both 2n= 4x= 24) are recent allotetraploids derived fromT. dubius×T. porrifoliusandT. dubius×T. pratensis(each 2n= 2x= 12), respectively. The genome sizes ofT. mirusare additive of those of its diploid parents, but at least some populations ofT. miscellushave undergone genome downsizing. To survey for genomic rearrangements in the allopolyploids, four repetitive sequences were physically mapped. TPRMBO (unit size 160 base pairs [bp]) and TGP7 (532 bp) are tandemly organized satellite sequences isolated fromT. pratensisandT. porrifolius, respectively. Fluorescent in situ hybridization to the diploids showed that TPRMBO is a predominantly centromeric repeat on all 12 chromosomes, while TGP7 is a subtelomeric sequence on most chromosome arms. The distribution of tandem repetitive DNA loci (TPRMBO, TGP7, 18S‐5.8S‐26S rDNA, and 5S rDNA) gave unique molecular karyotypes for the three diploid species, permitting the identification of the parental chromosomes in the polyploids. The location and number of these loci were inherited without apparent changes in the allotetraploids. There was no evidence for major genomic rearrangements inTragopogonallopolyploids that have arisen multiple times in North America within the last 80 yr.
Seedling establishment and life history trade‐offs in alpine plants
Authors: Forbis Tara A. , Doak Daniel F.
Published: February 2008

Seedling establishment is central to population maintenance for nonclonal plant species. Plants with low recruitment rates are expected to have high survival rates, and life history theory indicates there should be a single curve for the trade‐off between recruitment and mortality that applies to most or all plant species. Alpine perennials are thought to have extraordinarily low recruitment rates because of the harsh environment, but the importance of recruitment in the life history of these plants is unknown. Two alpine cushion plant species, Minuartia obtusiloba and Paronychia pulvinata, were used to (1) determine the role of recruitment in population maintenance and (2) determine whether the fecundity/mortality trade‐off for these alpine plants falls on or off of the curve for other perennial plant species. Using size‐based population projection matrices, we determined that the life history of Minuartia and Paronychia emphasizes recruitment less than that of any other nonclonal species in a literature survey. Estimated maximum life spans of these two species are 200 and 324 yr, respectively, and a regression with other perennial species from the literature indicated that the relationship between fecundity and mortality in these alpine species is consistent with the predicted trade‐off curve for perennial species from other environments.
Systematics of Ipomoea subgenus Quamoclit (Convolvulaceae) based on ITS sequence data and a Bayesian phylogenetic analysis
Authors: Miller Richard E. , McDonald J. Andrew , Manos Paul S.
Published: February 2008

A Bayesian phylogenetic analysis of 36 Ipomoea species using sequence data from the internal transcribed spacer region was compared with classification schemes based on traditional methods and a previously published cpDNA restriction fragment length polymorphism (RFLP) study. These molecular studies support a diversity of groups that were circumscribed on the basis of phenetic principles and agree generally with the results from cpDNA RFLP analyses. The congruence between the phylogenetic hypotheses based on new molecular data and the understanding of relationships developed in earlier studies indicate that these classifications may reflect evolutionary history. Two large clades of species, with one including sections Tricolores, Calonyction, and Pharbitis and the other including sections Mina and Leptocallis, were identified. Furthermore, morphologically distinct groups of Ipomoea species received support from the DNA sequence data. Indices of convergence for the Markov chain Monte Carlo (MCMC) in the Bayesian phylogenetic analysis were evaluated. A limited range of posterior probabilities for each node in the trees from a set of five MCMC samples provides a useful index of convergence. Bayesian node support values were generally higher than bootstrap values from a maximum parsimony analysis. This is consistent with the notion that these measures of support estimate different qualities of the data.
Variation in wetland seed banks across a tidal freshwater landscape
Authors: Peterson Jessica E. , Baldwin Andrew H.
Published: February 2008

Almost nothing is known about landscape‐level variation in seed bank composition across complexes of hydrologically connected wetlands. We examined species composition of seed and spore banks in three habitats of tidal freshwater wetlands (marshes, swamp hollows, and swamp hummocks) along 48 km of tributaries throughout the tidal freshwater portions of the Nanticoke River watershed (Maryland and Delaware). Taxa and seedling density decreased with increasing distance upstream in the swamp hollows and hummocks, but increased or remained constant proceeding upstream in the marshes. Species rarefaction curves indicated equal taxa richness (28) between marshes and swamp hummocks at 175 individuals, with lower richness in swamp hollows (19). However, communities in swamp hollows were patchier and had an estimated total taxa richness of 52, similar to the marshes (50) and higher than swamp hummocks (41). Coefficients of variation for seedling emergence densities (136–180%) were greater than those of published seed bank studies conducted at smaller spatial scales in tidal freshwater marshes (36–117%). Our literature searches suggest that ours is the first study to document significant spatial trends in seed bank diversity and density across a wetland landscape.
Molecular evidence for limited dispersal of vegetative propagules in the epiphytic lichenLobaria pulmonaria
Authors: Walser Jean‐Claude
Published: February 2008

Propagation, whether sexual or asexual, is a fundamental step in the life cycle of every organism. In lichenized fungi, a great variety of vegetative propagules have evolved in order for the symbiotic partners to disperse simultaneously. For lichens with the ability of sexual and asexual reproduction, the relative contribution of vegetative dispersal is unknown but could, nonetheless, be inferred by studying genotype distribution. The genetic structure of threeLobaria pulmonaria(Lobariaceae) populations from Switzerland was investigated based on the observed variation at six microsatellite loci. All three populations had a clustered distribution of identical genotypes at small spatial scales. The maximum distance between identical genotypes was 230 m. At a distance of 350 m from a source tree, seemingly suitable habitat patches were too far apart to be colonized. Some multilocus genotypes were frequent within local populations but no genotypes were shared among populations. The restricted occurrences of common genotypes as well as the clustered distributions are evidence for a limited dispersal of vegetative propagules inL. pulmonaria. Gene flow among isolated populations will ultimately depend on the capacity of long‐distance dispersal and thus probably depend on sexual reproduction.
Natural hybridization and hybrid zones betweenQuercus crassifoliaandQuercus crassipes(Fagaceae) in Mexico: morphological and molecular evidence
Authors: Tovar‐Sánchez Efraín , Oyama Ken
Published: February 2008

Hybrid zones provide interesting systems to study genetic and ecological interaction between different species. The correct identification of hybrids is necessary to understand the evolutionary process involved in hybridization. An oak species complex occurring in Mexico formed by two parental species,Quercus crassifoliaH. & B. andQ. crassipesH. & B., and their putative hybrid species,Q. dysophylla, was analyzed with molecular markers (random amplified polymorphic DNA [RAPDs]) and morphological tools in seven hybrid zones (10 trees per taxa in each hybrid zone) and two pure sites for each parental species (20 trees per site). We tested whether geographic proximity of hybrid plants to the allopatric site of a parental species increases its morphological and genetic similarity with its parent. Seventeen morphological traits were measured in 8700 leaves from 290 trees. Total DNA of 250 individuals was analyzed with six diagnostic RAPD primers.Quercus crassifoliadiffered significantly fromQ. crassipesin all the examined characters. Molecular markers and morphological characters were highly coincident and support the hypothesis of hybridization in this complex, although both species remain distinct in mixed stands. Clusters and a hybrid index (for molecular and morphological data) showed that individuals from the same parental species were more similar among themselves than to putative hybrids, indicating occasional hybridization with segregation in hybrid types or backcrossing to parents. Evidence does not indicate a unidirectional pattern of gene flow.
Leaf longevity of Oxalis acetosella (Oxalidaceae) in the Catskill Mountains, New York, USA
Authors: Tessier Jack T.
Published: February 2008

Leaf habit correlates with multiple physiological traits. Understanding ecophysiology is therefore dependent on knowledge of leaf habit. A variety of leaf habits exists within forest understory plant communities. Oxalis acetosella is one such understory plant and has long been considered a wintergreen, meaning that it keeps a set of leaves for one full year, replacing them with a new set during spring. To assess the leaf habit of O. acetosella and place it into a classification scheme of leaf habits, leaves of four populations of O. acetosella were repeatedly censused for two years in a northern hardwood forest of the Catskill Mountains, New York, USA. New leaves developed and old leaves senesced throughout the year, yielding a continual replacement of leaves and a summer peak in leaf number. Leaves that developed in the fall and winter had longer maximum life spans than leaves that developed during the summer. The name “seasonalgreen” is suggested to describe the continual development, senescence, and presence of leaves and annual peak in leaf number within O. acetosella. The functional significance of this leaf habit in this species and the possibility of its presence in other species deserve further study.