bluuebunny/crossref_metadata_2025 huggingface dataset:
Phylogenetic relationships of functionally dioecious FICUS (Moraceae) based on ribosomal DNA sequences and morphology
Authors: Weiblen George D.
Published: April 2006

Figs (Ficus, Moraceae) are either monoecious or gynodioecious depending on the arrangement of unisexual florets within the specialized inflorescence or syconium. The gynodioecious species are functionally dioecious due to the impact of pollinating fig wasps (Hymenoptera: Agaonidae) on the maturation of fig seeds. The evolutionary relationships of functionally dioecious figs (Ficus subg. Ficus) were examined through phylogenetic analyses based on the internal transcribed spacer (ITS) region of nuclear ribosomal DNA and morphology. Forty‐six species representing each monoecious subgenus and each section of functionally dioecious subg. Ficus were included in parsimony analyses based on 180 molecular characters and 61 morphological characters that were potentially informative. Separate and combined analyses of molecular and morphological data sets suggested that functionally dioecious figs are not monophyletic and that monoecious subg. Sycomorus is derived within a dioecious clade. The combined analysis indicated one or two origins of functional dioecy in the genus and at least two reversals to monoecy within a functionally dioecious lineage. The exclusion of breeding system and related characters from the analysis also indicated two shifts from monoecy to functional dioecy and two reversals. The associations of pollinating fig wasps were congruent with host fig phylogeny and further supported a revised classification of Ficus.
Ribosomal DNA evolution and phylogeny in Aloe (Asphodelaceae)
Authors: Adams Stuart P. , Leitch Ilia J. , Bennett Michael D. , Chase Mark W. , Leitch Andrew R.
Published: April 2006

All Aloe taxa (∼400 species) share a conserved bimodal karyotype with a basic genome of four large and three small submetacentric/acrocentric chromosomes. We investigated the physical organization of 18S–5.8S–26S and 5S ribosomal DNA (rDNA) using fluorescent in situ hybridization (FISH) to 13 Aloe species. The organization was compared with a phylogenetic tree of 28 species (including the 13 used for FISH) constructed by sequence analysis of the internal transcribed spacer (ITS) of 18S–5.8S–26S rDNA. The phylogeny showed little divergence within Aloe, although distinct, well‐supported clades were found. FISH analysis of 5S rDNA distribution showed a similar interstitial location on a large chromosome in all species examined. In contrast, the distribution of 18S–5.8S–26S rDNA was variable, with differences in number, location, and size of loci found between species. Nevertheless, within well‐supported clades, all species had the same organizational patterns. Thus, despite the striking stability of karyotype structure and location of 5S rDNA, the distribution of 18S–5.8S–26S rDNA is not so constrained and has clearly changed during Aloe speciation.
Effects of pollen load size and composition on pollen donor performance in wild radish, Raphanus sativus (Brassicaceae)
Authors: Marshall Diane L. , Avritt Joy J. , Shaner Marieken , Saunders R. Leigh
Published: April 2006

A critical concern in the debate over the importance of sexual selection in plants is whether the nonrandom mating demonstrable in greenhouse crosses can occur in the field. Field populations likely experience smaller and more variable pollen load sizes than those that have been used in many greenhouse experiments. Therefore, we performed a greenhouse experiment in which we varied both pollen load size and composition in wild radish, Raphanus sativus, and examined the paternity of seeds. We used five maternal plants and four pairs of pollen donors. We were able to produce pollen loads of 40, 118, and 258 grains per stigma. The smallest of the pollen loads was scant enough to result in a slight, but significant reduction in seed number per fruit. While variation in pollen load composition significantly affected the proportions of seeds fathered by different donors, variation in pollen load size did not. The relative performance of different donors was constant across pollen load sizes, suggesting that, for this species, differential performance of pollen donors can occur at pollen load sizes that are likely to occur in field populations.
Combined phylogenetic analysis in the Rubiaceae‐Ixoroideae: morphology, nuclear and chloroplast DNA data
Authors: Andreasen Katarina , Bremer Birgitta
Published: April 2006

Parsimony analyses of morphology, restriction sites of the cpDNA, sequences from the nuclear, ribosomal internal transcribed spacer (ITS), and the chloroplast generbcLwere performed to asses tribal and generic relationships in the subfamily Ixoroideae (Rubiaceae). The tribes Vanguerieae and Alberteae (Antirheoideae) are clearly part of Ixoroideae, as are some Cinchonoideae taxa. Pavetteae should excludeIxoraand allies, which should be recognized as the tribe Ixoreae.Heinsenia, representing Aulacocalyceae, is part of Gardenieae, as isDuperrea, a genus earlier placed in Pavetteae.PosoqueriaandBertieraand the taxa in the subtribe Diplosporinae should be excluded from Gardenieae.Bertieraand three Diplosporinae taxa are part of Coffeeae, whileCremaspora(Diplosporinae) is best housed in a tribe of its own, Cremasporeae. The mangrove genusScyphiphora, recently placed in Diplosporinae, is closer to Ixoreae and tentatively included there. The combined analysis resulted in higher resolution compared to the separate analyses, exemplifying that combined analyses can remedy the incapability of one data set to resolve portions of a phylogeny. Twenty‐four newrbcLsequences representing all five Ixoroideae tribes (sensu Robbrecht) are presented.
ITS sequence data support a single origin for North American Astereae (Asteraceae) and reflect deep geographic divisions in Aster s.l.
Authors: Noyes Richard D. , Rieseberg Loren H.
Published: April 2006

The Astereae is the largest tribe of Asteraceae in North America. Morphological diversity suggests that the North American assemblage is polyphyletic as 12 endemic genera, as well as lineages of the genus Erigeron and Conyza (Conyzinae), have been hypothesized to represent at least five separate invasions of North America from Africa, Australia, Eurasia, and South America. This hypothesis was tested with a phylogenetic analysis of nucleotide sequence data from the internal transcribed spacers (ITS) of nuclear ribosomal DNA. Sequences for 62 taxa represent seven outgroup taxa and all major Northern and Southern Hemisphere groups of Astereae, including broad taxonomic and geographic sampling of Conyzinae and Aster s.l. (sensu lato). Parsimony analyses indicate that all North American Astereae are members of a strongly supported clade, and that a diverse group of predominantly woody taxa from Africa, Australia, and South America, are basal Astereae. Furthermore, Aster s.l. is deeply polyphyletic as Eurasian taxa, including Aster s.s. (sensu stricto), appear more closely related to Southern Hemisphere taxa than to North American Aster segregates. There is only low to moderate agreement between proposed higher level Astereae relationships based on ITS and those based either on morphology or chloroplast restriction site data.
Germination and growth responses of hybridizing Carpobrotus species (Aizoaceae) from coastal California to soil salinity
Authors: Weber Ewald , D'Antonio Carla M.
Published: April 2006

Germination, growth, and physiological responses of hybridizing Carpobrotus from coastal California to soil salinity were studied. Hybrids are presumably the result of hybridization and introgression between the exotic Carpobrotus edulis, a succulent perennial invading coastal habitats, and the native or long‐naturalized C. chilensis. Germination responses were investigated at 0, 10, 20, and 50% seawater. Seedling growth and physiology were compared by irrigating seedlings with solutions of the same seawater concentrations and in low and high nutrients. Germination was inhibited in the presence of salt, but recovered after transferring the seeds to fresh water. Seeds exposed to salt had higher final germination rates than control. Growth of Carpobrotus was slightly enhanced by low seawater concentrations but reduced at high salinity at both nutrient regimes. Leaf cell sap osmolarity increased with increasing soil salinity, and taxa did not differ significantly in this physiological adjustment. Leaf carbon isotope ratios (∂13C) ranged from −28 to −22‰ and became less negative at higher salinities, indicating an improved water use efficiency in the seedlings at high salt concentrations. In addition, ∂13C values were generally less negative at high than at low nutrients. Differences among taxa were generally small. The results show that salinity affects both establishment and growth of hybridizing Carpobrotus. The overall weak species differences in salt tolerance indicate that the exotic C. edulis can occupy the same sites as C. chilensis in terms of salinity. The similarity of hybrids in their response to salinity suggests that they may contribute to the invasion by Carpobrotus.
Short‐term effects of fire and competition on growth and plasticity of the yellow pitcher plant,Sarracenia alata(Sarraceniaceae)
Authors: Brewer J. Stephen
Published: April 2006

Although recurrent fires are widely assumed to reduce competitive interference of plants of pine savannas, rarely has this assumption been tested explicitly. This 2‐yr study reports on the interactive effects of fire and neighbors on short‐term growth responses and plasticity in allocation patterns of a carnivorous plant, the yellow pitcher plant,Sarracenia alata.This species relies upon pitfall traps (pitchers) to attract and capture insects to obtain nutrients. Neighbors reduced the growth rate of individual ramet transplants (phytometers) in one but not both years of the study. The effect of neighbors on total (i.e., both above‐ and belowground) productivity of phytometers was not reduced by a winter fire. Neighbors had a greater effect on large plants than on small plants. Although fire did not affect the growth rate of phytometers in the short term, allocation patterns were greatly altered by both neighbors and fire. Allocation to pitchers increased at the expense of belowground organs following fire and in the absence of neighbors at the unburned site. Results of the current study suggest that adult pitcher plants may tolerate competition from neighboring vegetation by reducing allocation to costly pitchers during years without fire.
Molecular evidence for allopolyploid speciation and a single origin of the narrow endemic Draba ladina (Brassicaceae)
Authors: Widmer Alex , Baltisberger Matthias
Published: April 2006

Draba ladina (Brassicaceae) is a small alpine flower endemic to the Swiss Alps. It occurs exclusively at elevations between 2600 and 3000 m and is restricted to less than a dozen mountains in the Lower Engadin. Morphological characters and polyploidy suggest a hybrid origin. Potential diploid progenitor species are distributed widely and often occur sympatrically. To study the evolutionary history of D. ladina we assessed intra‐ and interspecific sequence variation at noncoding chloroplast DNA loci and nuclear rDNA ITS sequences in D. ladina and its presumed progenitor species D. aizoides, D. dubia, and D. tomentosa. A single ITS (Internal Transcribed Spacer) genotype was found in each of D. aizoides and D. dubia and two in D. tomentosa. Additivity of ITS sequences of D. aizoides and D. tomentosa was found in D. ladina, supporting the hypothesis of an allotetraploid origin. Intraspecific cpDNA variation was found in all diploid species, but not in D. ladina. The single chloroplast DNA haplotype found in the latter was closest to one cpDNA haplotype found in D. tomentosa, suggesting that D. tomentosa was the maternal parent. These results suggest that D. ladina is a relatively young, presumably postglacial, taxon with a single allopolyploid origin.
Auxin metabolism in mosses and liverworts
Authors: Ester Sztein A. , Cohen Jerry D. , de la Fuente Ine´s Garci´a , Cooke Todd J.
Published: April 2006

The plant hormone auxin (indole‐3‐acetic acid, IAA) is involved in the control of many phenomena during plant development. By characterizing steady‐state free and conjugated IAA levels using a stable isotope dilution method coupled with gas chromatography‐ selected ion monitoring‐ mass spectrometry, this paper provides a detailed characterization of IAA metabolism in five liverworts, four mosses, and two tracheophytes. Long‐term IAA conjugation patterns were monitored by incubating actively growing tissue with 14C‐IAA and then analyzing the de novo synthesis of IAA conjugates with radioimaging techniques. The liverworts, mosses, and tracheophytes can be differentiated by the total amount of IAA metabolites, the proportion of free and conjugated IAA, the chemical nature of their IAA conjugates, and the rates of IAA conjugation. Our tentative conclusion is that the liverworts appear to employ a biosynthesis–degradation strategy for the regulation of free IAA levels, in contrast to the conjugation–hydrolysis strategy apparently used by the mosses and tracheophytes. Such alternative metabolic strategies may have profound implications for macroevolutionary processes in these plant groups.
Identifying inflorescence phytoliths from selected species of wheat (Triticum monococcum, T. dicoccon, T. dicoccoides, and T. aestivum) and barley (Hordeum vulgare and H. spontaneum) (Gramineae)
Authors: Ball Terry B. , Gardner John S. , Anderson Nicole
Published: April 2006

Analysis of microfossil silica phytoliths is becoming an increasingly important research tool for taxonomists, archaeobotanists, and paleoecologists. Expanded use of phytolith analysis by researchers is dependent upon development of phytolith systematics. In this study phytoliths produced by the inflorescence bracts from four species of wheat, Triticum monoccocum, T. dicoccon, T. dicoccoides, and T. aestivum, and two species of barley, Hordeum vulgare, and H. spontaneum, were analyzed using computer‐assisted image and statistical analysis with the intent to develop taxonomic tools to distinguish among the taxa. A classification key based on significant differences among the mean morphometries of the inflorescence phytoliths produced by each species was created and tested. Discriminant analysis of the morphometries of several morphotypes of phytoliths was also conducted to determine whether this computer‐assisted statistical procedure could be used as another method to classify the taxa and to determine which morphotypes have measurements that can best be used in discriminant functions. Test results indicated that, at the genus level, both the classification key and discriminant analysis of certain morphotypes of phytoliths were relatively reliable tools for distinguishing among phytoliths produced in the inflorescence bracts of the taxa considered. For distinguishing among the taxa at the species level, the classification key was most reliable. Of the discriminant analyses tested, that based on all the phytolith morphotypes combined was more reliable than those based on only one morphotype.
The mechanical role of bark
Authors: Niklas Karl J.
Published: April 2006

The ability of stem bark to resist bending forces was examined by testing in bending segments of Acer saccharum, Fraxinus americana, and Quercus robur branches with and without their bark. For each species, the bark contributed significantly to the ability of stem segments differing in age to resist bending forces, but its contribution was age‐dependent and differed among the three species. The importance of the mechanical role of the bark decreased basipetally with increasing age of F. americana and Q. robur stem segments and was superceded by that of the wood for segments ≥ 6 yr old. A. saccharum bark was as mechanically important as the wood for stem segments 7 yr old but was not a significant stiffening agent for younger or older portions of stems. On average, the stiffness of the bark from all three species was 50% that of the wood. However, the geometric contribution to the flexural rigidity of stems made by the bark (i.e., the bark's second moment of area) was sufficiently large to offset its lower stiffness (Young's modulus) relative to that of the wood. A simple model is presented that shows that the bark must be as mechanically important as the wood when its radial thickness equals 32% that of the wood and its stiffness is 50% that of the wood. Based on this model, which is shown to comply with the data from three species purported to have stiff woods, it is evident that the role of the bark cannot be neglected when considering the mechanical behavior of juvenile woody stems subjected to externally applied bending forces.
The effects of hybridization in plants on secondary chemistry: implications for the ecology and evolution of plant–herbivore interactions
Authors: Orians Colin M.
Published: April 2006

Natural hybridization is a frequent phenomenon in plants. It can lead to the formation of new species, facilitate introgression of plant traits, and affect the interactions between plants and their biotic and abiotic environments. An important consequence of hybridization is the generation of qualitative and quantitative variation in secondary chemistry. Using the literature and my own results, I review the effects of hybridization on plant secondary chemistry, the mechanisms that generate patterns of chemical variation, and the possible consequences of this variation for plants and herbivores. Hybrids are immensely variable. Qualitatively, hybrids may express all of the secondary chemicals of the parental taxa, may fail to express certain parental chemicals, or may express novel chemicals that are absent in each parent. Quantitatively, concentrations of parental chemicals may vary markedly among hybrids. There are five primary factors that contribute to variation: parental taxa, hybrid class (F1, F2, etc.), ploidy level, chemical class, and the genetics of expression (dominance, recessive vs. additive inheritance). This variation is likely to affect the process of chemical diversification, the potential for introgression, the likelihood that hybrids will facilitate host shifts by herbivores, and the conditions that might lead to enhanced hybrid susceptibility and lower fitness.
Allozyme evidence for genetic autopolyploidy and high genetic diversity in tetraploid cranberry, Vaccinium oxycoccos (Ericaceae)
Authors: Mahy Grégory , Bruederle Leo P. , Connors Bridget , Van Hofwegen Michael , Vorsa Nicholi
Published: April 2006

Polyploidy has been important in the evolution of angiosperms and may significantly affect population genetic diversity and structure. Nineteen isoenzyme loci were studied in diploid and tetraploid populations of Vaccinium oxycoccos (Ericaceae), and the results are compared with data previously reported for the related V. macrocarpon. Diploid V. oxycoccos and V. macrocarpon were readily discriminated based on their allozymic variation. No evidence for fixed heterozygosity was found in tetraploid V. oxycoccos. In contrast, all polymorphic loci exhibited both balanced and unbalanced heterozygotes, with some individuals exhibiting a pattern consistent with the presence of three alleles. These results support an autopolyploid origin for tetraploid V. oxycoccos. However, tetraploid V. oxycoccos possessed a suite of alleles not found in diploid V. oxycoccos; half of these alleles were shared with V. macrocarpon. This suggests that autotetraploid V. oxycoccos may have undergone hybridization with V. macrocarpon or that the autotetraploid retained the genetic variation present in an ancestral diploid species. Following theoretical expectations, proportion of polymorphic loci, mean number of alleles, and observed heterozygosity were significantly higher for the autotetraploid than for the diploid. Mean inbreeding (FIS) was similar for diploid and tetraploid V. oxycoccos. The latter exhibited population differentiation (FST) exceeding both diploid species.
Phylogeny and biogeography of Eupatorium (Asteraceae: Eupatorieae) based on nuclear ITS sequence data
Authors: Schmidt Gregory J. , Schilling Edward E.
Published: April 2006

The classification of the predominantly Neotropical Eupatorieae depends upon the circumscription of the core genus Eupatorium. The recently proposed narrowing of Eupatorium to ∼42 species in eastern temperate North America, Europe, and eastern Asia was tested with phylogenetic analysis of nucleotide sequence variation in the internal transcribed spacer (ITS) region of nuclear ribosomal DNA. A total of 40 samples (36 species) of Eupatorieae was analyzed. Several species from North America, South America, and Eurasia that were formerly recognized within a large Eupatorium s.l. (sensu lato) were included in the study. Other taxa included were representative of the majority of the subtribes native to eastern temperate North America. Parsimony analysis supported the contention that Eupatorium be defined narrowly and suggested that Eupatoriadelphus is distinct. The tree topology suggested that Eupatorium and Eupatoriadelphus share a common North American ancestor with Liatris relative to other Eupatorieae. It was apparent that the presumed sister taxa in Eupatoriinae from South America belong to a different clade. These results suggest that, following initial divergence in North America, Eupatorium reached Europe via dispersal during the late Pliocene with subsequent radiation in Asia.
The questionable relationship ofMontinia(Montiniaceae): evidence from a floral ontogenetic and anatomical study
Authors: Decraene Louis P. Ronse , Linder H. Peter , Smets Erik F.
Published: April 2006

The systematic position of Montiniaceae remains uncertain: a relationship with Cornales has been suggested on phytochemical and embryological evidence, while molecular data point to a relationship with Solanales. We investigated the floral development and anatomy of the South AfricanMontinia caryophyllaceato add a new set of characters for clarifying the systematic position of the family Montiniaceae. Pistillate inflorescences show a higher degree of reduction than staminate, with flowers set terminally on short lateral branches. Flowers have an irregular initiation sequence, with frequent abortions of organs. InMontinia, petals grow rapidly, and no zonal growth takes place. The gynoecium develops as a pit surrounded by a girdle. Placentation is basically parietal and becomes axillary by the postgenital fusion of placental lobes; unitegmic ovules are arranged in two parallel rows with adjacent ovules partly overlapping each other. Unisexuality is respectively attained at the stage of anther development and carpel initiation. The floral anatomy of pistillate and staminate flowers is illustrated and discussed. Observations onMontiniaare compared with data of taxa from Saxifragaceae sensu stricto, Cornales, and Solanales. The absence of sympetaly inMontiniais discussed. Morphological and anatomical evidence points to a high similarity with Escalloniaceae. Although a position in the asterids is most probable, there is little support for the relationship with Solanales indicated by molecular data.
A new chromosome race of Calycadenia pauciflora (Asteraceae: Heliantheae–Madiinae) from Butte County, California
Authors: Carr Gerald D. , Carr Robert L.
Published: April 2006

We initiated a biosystematic study of a recently discovered population of Calycadenia pauciflora in order to evaluate its cytogenetic relationship to previously characterized chromosome races of that species. Cytogenetic analyses of six or more artificially produced individuals of each of the five possible interracial hybrid combinations indicated that the new race (designated Wurlitzer) is differentiated from the other races (Elegans, Healdsburg, Pauciflora, Ramulosa, and Tehama) by the equivalent of 2–4 reciprocal chromosome translocations and in one instance apparently a pericentric inversion. Mean pollen stainability in the hybrids ranged from 13 to 26%. The floral and vegetative features of the new race are very similar to those of races Pauciflora, Ramulosa, and Tehama of C. pauciflora. We ascribe the apparent lack of single‐step cytogenetic events in the evolution of the races of C. pauciflora to one or more of the following: (1) (in some cases) the occurrence of saltational chromosome reorganization; (2) extinction of or failure to detect intermediate populations in C. pauciflora; and (3) an insufficient consideration of the possibility of the existence of intermediate races in the closely related species, C. fremontii. We conclude that the C. fremontii–C. pauciflora alliance is one of the most complex and potentially instructive examples of diploid chromosome evolution in plants.
Environmental distribution of fourCarexspecies (Cyperaceae) in an old‐growth forest
Authors: Vellend Mark , Lechowicz Martin J. , Waterway Marcia J.
Published: April 2006

We conducted an in‐depth characterization of the range of micro‐environments (1 m2) in which fourCarexspecies (C. backii, C. communis, C. plantaginea, andC. platyphylla) grow in the understory of an old‐growth, deciduous forest in southern Québec, Canada. All four species occurred in significantly different micro‐environments.Carex plantagineawas found at the wet end of a moisture gradient, in soils with high nitrate availability.Carex backiiandC. platyphyllawere found at the dry end of the moisture gradient, withC. backiioccupying soils with higher phosphorus availability thanC. platyphylla. Carex communis, the only ant‐dispersed species studied, was found in the broadest range of environmental conditions. Our results suggest that environmental heterogeneity and interspecific microhabitat preferences are important for the maintenance of local species diversity in the forest understory, not only for common species as demonstrated in previous studies, but for infrequent species, and those within a functional group (uplandCarexspecies). However, there was some evidence that the distributions ofC. backiiandC. communiswere not in equilibrium with current environmental conditions, indicating that historical factors, such as dispersal and colonization events, may also have important effects on the distributions of these species and the maintenance of species diversity in old‐growth forest.
Studies in Neotropical paleobotany. XIV. A palynoflora from the Middle Eocene Saramaguacán Formation of Cuba
Authors: Graham Alan , Cozadd Duane , Areces‐Mallea Alberto , Frederiksen Norman O.
Published: April 2006

An assemblage of 46 fossil pollen and spore types is described from a core drilled through the middle Eocene Saramaguacán Formation, Camagüey Province, eastern Cuba. Many of the specimens represent unidentified or extinct taxa but several can be identified to family (Palmae, Bombacaceae, Gramineae, Moraceae, Myrtaceae) and some to genus (Pteris, Crudia, Lymingtonia?). The paleoclimate was warm‐temperate to subtropical which is consistent with other floras in the region of comparable age and with the global paleotemperature curve. Older plate tectonic models show a variety of locations for proto‐Cuba during Late Cretaceous and later times, including along the norther coast of South America. More recent models depict western and central Cuba as two separate parts until the Eocene, and eastern Cuba (joined to northern Hispaniola) docking to central Cuba also in the Eocene. All fragments are part of the North American Plate and none were directly connected with northern South America in late Mesozoic or Cenozoic time. The Saramaguacán flora supports this model because the assemblage is distinctly North American in affinities, with only one type (Retimonocolpites type 1) found elsewhere only in South America.
Genetic discontinuity revealed by chloroplast microsatellites in eastern North American Abies (Pinaceae)
Authors: Clark Catherine M. , Wentworth Thomas R. , O'Malley David M.
Published: April 2006

Development of conservation strategies for Fraser fir (Abies fraseri) in the southern Appalachian Mountains depends in part on recognition of the extent to which Fraser fir is genetically distinct from the closely related balsam (A. balsamea) and intermediate (A. balsamea var. phanerolepis) fir. These sibling species have exhibited intergrading, clinal variation in morphological, chemical, and genetic characteristics in prior research. Chloroplast microsatellite markers were polymerase chain reaction amplified from genomic DNA samples of 78 individuals representing the geographic ranges of Fraser, balsam, and intermediate fir. Gene diversity levels at two loci ranged among taxa from 0.65 to 0.84. Allele frequencies demonstrated significant differentiation among taxa, with RST values of 0.36 and 0.10. Haplotype diversity and D2SH were highest for balsam fir and lowest for intermediate fir. A haplotype network analysis based on allele size distribution for the two loci revealed two distinct clusters of haplotypes and population‐specific haplotypes. Ninety‐two percent of the haplotypes in one cluster were from balsam fir and intermediate fir, and 84% of the haplotypes in the other cluster were from Fraser fir and intermediate fir. The genetic differentiation of chloroplast DNA markers provides justification for the recognition of Fraser fir as a distinct Management Unit (MU) for conservation purposes, regardless of its taxonomic classification.
Factors affecting establishment of a gypsophyte: the case of Lepidium subulatum (Brassicaceae)
Authors: Escudero Adrián , Iriondo José M. , Olano José M. , Rubio Agustín , Somolinos Roberto C.
Published: April 2006

The restriction of vascular plants to gypsum‐rich soils under arid or semiarid climates has been reported by many authors in different parts of the world. However, factors controlling the presence of gypsophytes on these soils are far from understood. We investigated the establishment of Lepidium subulatum, a gypsophyte, in a nondisturbed semiarid gypsum‐soil landscape in central Spain, both from spatial and temporal perspectives. Over 1400 seedlings were tagged, and their growth and survival were monitored for a 2‐yr period. Several biotic and abiotic variables were measured to determine the factors controlling the emergence and early survival. These variables included the cover of annual plants, bryophytes, lichens, litter, gypsum crystals, bare fraction and cover of each perennial plant, and several soil properties (gravel, fine gravel, and fine‐earth fraction, conductivity, pH, gypsum content, organic matter and penetrometer soil resistance). Our results support the linkage of gypsophily with some physical properties of the surface crust. Seedlings tended to establish on the gypsum surface crust, and their survival was size dependent, probably as a consequence of the necessity of rooting below the surface crust before summer drought arrives. However, once seedlings emerged, a higher survival rate occurred on the alluvial soils of the piedmont‐slope boundary where soil crusts are absent or thinner. We conclude that Lepidium subulatum may be considered a refuge model endemic with a distribution range that occupies a reduced fraction of a wider habitat from which it is probably excluded by competition.
Phylogeny and biogeography of Juglans (Juglandaceae) based on matK and ITS sequence data
Authors: Stanford Alice M. , Harden Rachel , Parks Clifford R.
Published: April 2006

We investigated phylogenetic and biogeographic relationships within Juglans (walnuts), a Tertiary disjunct genus, using 15 species of Juglans and related (Juglandaceae) outgroups. The relationships were analyzed using nucleotide sequences of the chloroplast gene matK and its flanking spacers and of the internal transcribed spacers (ITS) and 5.8S gene of the nuclear ribosomal DNA. The DNA sequences provided 246 informative characters for parsimony analysis. ITS data supported as monophyletic groups the four generic sections, Cardiocaryon, Dioscaryon, Rhysocaryon, and Trachycaryon. Within Rhysocaryon, the temperate black walnuts and the tropical black walnuts were supported as monophyletic groups. When the two data sets were combined, J. cinerea was nested within Cardiocaryon. Combined analysis with published nuclear DNA restriction site data placed J. cinerea in a monophyletic group with Cardiocaryon. These analyses consistently supported Juglans as a monophyletic group and as the sister group to the genus Pterocarya. The results of this work are consistent with the known geological history of Juglans. The fossil record suggests that the butternuts had evolved by the early Oligocene in North America. The presence of butternuts in Eurasia could be the result of migration from North America to Eurasia during the warming trend of the mid Oligocene.
Chloroplast DNA evidence for the evolution of Microseris (Asteraceae) in Australia and New Zealand after long‐distance dispersal from western North America
Authors: Vijverberg Kitty , Mes Ted H. M. , Bachmann Konrad
Published: April 2006

Restriction site mutations and trnL(UAA)‐trnF(GAA) intergenic spacer length variants in the chloroplast genome were used to investigate the phylogenetic relationships among 53 Australian and New Zealand Microseris populations and to assess their position within their primarily North American genus. The study was performed to enhance understanding of evolutionary processes within this unique example of intercontinental dispersal and subsequent adaptive radiation. A southern blot method using four‐base restriction enzymes and fragment separation on polyacryamide gels resulted in 55 mutations of which 30 were potentially phylogenetically informative. Most mutations were small indels of <162 bp, 80% of which were <20 bp. The small indels were useful for phylogenetic reconstruction of Australasian Microseris as judged by the high consistency indexes. The results confirmed the monophyly of the Australian and New Zealand Microseris. The occurrence of “hard” basal polytomies in the most parsimonious trees indicated that rapid radiation has occurred early in the history of the taxon. The monophyly of M. lanceolata, which includes the self‐incompatible ecotypes of the Australian mainland, was confirmed. Within this species three clades were found that reflect more geographic distribution than morphological entities, suggesting that migration and possibly introgression between different ecotypes, or parallel evolution of similar adaptations, has occurred. One of the three clades was supported by a 162‐bp deletion in the trnL‐trnF spacer, while a subgroup of this exhibited also a tandemly repeated trnF exon. The data were inconclusive about the monophyly of the second Australasian species, M. scapigera, which comprises the New Zealand, Tasmanian, and autofertile ecotypes of Australia.
Why Canny's theory doesn't hold water
Authors: Comstock Jonathan P
Published: April 2006

A critique of Martin Canny's theory of water transport supported by tissue pressure is given with reference to basic principles of cellular water relations and biomechanics. It is shown that the application of tissue pressure in Canny's theory is neither internally consistent nor compatible with basic biophysics. Canny's translation of tissue pressure into an altered steady‐state pressure in the xylem conduits has no defensible mechanism, relying instead on untenable action‐at‐a‐distance and poor definitions. Tissue pressure itself, as defined by Canny and illustrated by the example of a turgid leaf, may well exist. However, it cannot function in whole‐plant processes as envisioned by Canny, nor can it exist in the magnitude his theory would require. Rigid outer tissue layers containing internal pressures of the magnitude postulated by Canny would require a tensile strength quite incompatible with the observed biological materials. A simple application of La Place's Law illustrates that this is an issue of scale and that the turgor generated by osmotic potentials must be balanced primarily at the cellular level, and not the tissue level.
Quantitative evaluation of stigma polymorphism in a tristylous weed,Lythrum salicaria(Lythraceae)
Authors: Hermann Brian P , Mal Tarun K , Williams Russell J , Dollahon Norman R
Published: April 2006

Tristyly involves three different forms of flowers that differ reciprocally in the heights of stigmas and anthers within flowers. Apart from the style and stamen lengths, heterostylous species also demonstrate pollen and stigma polymorphisms. We quantified stigma polymorphism in tristylousLythrum salicariaby measuring the stigma diameters, structure of papillae, and density and distribution of papillae on the stigma from flower samples of 201 individuals belonging to three morphs. The diameter of the stigma and the distribution of papillae were quantified using a scanning electron microscope, and the structure of papillae was determined using a light microscope. The stigma diameter in the long morph was significantly greater than in the mid and short morphs. While the density of stigmatic papillae was significantly greater in the mid and short morphs than in the long morph, the total number of papillae per stigma did not differ across morphs. The length and diameter of papillae at the apex, neck, and base were significantly greater in the long morph followed by the mid and short morphs. A discriminant function analysis separated the long morph from the mid and short morphs based on the canonical scores of measurements of papillae structure. The stigma polymorphism coupled with those of pollen may play a functional role in self‐incompatibility mechanisms.
Genotypic variation for condensed tannin production in trembling aspen (POPULUS TREMULOIDES, salicaceae) under elevated CO2 and in high‐ and low‐fertility soil
Authors: Mansfield Jennifer L , Curtis Peter S , Zak Donald R , Pregitzer Kurt S
Published: April 2006

The carbon/nutrient balance hypothesis suggests that leaf carbon to nitrogen ratios influence the synthesis of secondary compounds such as condensed tannins. We studied the effects of rising atmospheric carbon dioxide on carbon to nitrogen ratios and tannin production. Six genotypes of Populus tremuloides were grown under elevated and ambient CO2 partial pressure and high‐ and low‐fertility soil in field open‐top chambers in northern lower Michigan, USA. During the second year of exposure, leaves were harvested three times (June, August, and September) and analyzed for condensed tannin concentration. The carbon/nutrient balance hypothesis was supported overall, with significantly greater leaf tannin concentration at high CO2 and low soil fertility compared to ambient CO2 and high soil fertility. However, some genotypes increased tannin concentration at elevated compared to ambient CO2, while others showed no CO2 response. Performance of lepidopteran leaf miner (Phyllonorycter tremuloidiella) larvae feeding on these plants varied across genotypes, CO2, and fertility treatments. These results suggest that with rising atmospheric CO2, plant secondary compound production may vary within species. This could have consequences for plant–herbivore and plant–microbe interactions and for the evolutionary response of this species to global climate change.
The Role of Public International Law in the WTO: How Far Can We Go?
Authors: Pauwelyn Joost
Published: April 2006

How does the World Trade Organization (WTO) relate to the wider corpus of public international law? What, in turn, is the role of public international law in WTO dispute settlement? This paper aims at resolving these two difficult questions. No straightforward answers to them can be found in WTO rules. Yet answering them has major ramifications both for the WTO (is the WTO a largely “self-contained regime” or is it not?) and for international law (is the future of international law further fragmentation or increased unity?). This exercise will be conducted under the law as it stands today—that is, the law as it may be invoked at present before the WTO “judiciary” (panels and the Appellate Body). Of course, WTO members (viz., the WTO “legislator”) could clarify or change the relationship between WTO rules and other rules of international law. However, it is unlikely that such changes will occur any time soon. In part I, I examine the general relationship between public international law and WTO law. I then assess, more specifically, the role of public international law in WTO dispute settlement in part II and offer some conclusions in part III.
On the Biological Standard of Living in Russia and the Soviet Union
Authors: Komlos John
Published: April 2006

The systematic study of the physical characteristics of human beings reaches well back into the eighteenth century. By the 1830s, scientists began to recognize that human biological outcomes were influenced, not only by inherited characteristics, but by both the natural and the socioeconomic environment. Genetic variation, by itself, did not account for the spatial, social, or temporal variation in physical stature. Only in the 1970s, however, did historians begin in earnest to explore the welfare implications of anthropometric measures. With the birth of “anthropometric history,” biological indicators, including physical stature, were used to assess the welfare of human beings as complements to such conventional indicators as income or real wages.
Aleksandr Sergeevich Pushkin on the World Wide Web: An Annotated Bibliography
Authors: Marsh-Flores Ann
Published: April 2006

The advent of the world wide web and electronic publishing has increased the number of resources available for Pushkinists and their students. Search engines, when asked to return lists of sites containing the keywords "Aleksandr Pushkin" offer hundreds (and often thousands) of potential matches; these hits range from websites including the more traditional scholarly apparatus of bibliographies and footnotes to reader-responses and grade school projects.
Traditional and Modern Approaches to Customary International Law: A Reconciliation
Authors: Roberts Anthea Elizabeth
Published: April 2006

The demise of custom as a source of international law has been widely forecasted. This is because both the nature and the relative importance of custom’s constituent elements are contentious. At the same time, custom has become an increasingly significant source of law in important areas such as human rights obligations. Codification conventions, academic commentary, and the case law of the International Court of Justice (the Court) have also contributed to a contemporary resurrection of custom. These developments have resulted in two apparently opposing approaches, which I term “traditional custom” and “modern custom.” The renaissance of custom requires the articulation of a coherent theory that can accommodate its classic foundations and contemporary developments. This article seeks to provide an enriched theoretical account of custom that incorporates both the traditional and the modern approaches rather than advocating one approach over the other.
Afterword: The Linkage Problem—Comments on Five Texts
Authors: Jackson John H.
Published: April 2006

The problem of linkage between “nontrade” subjects and the World Trade Organization is certainly one of the most pressing and challenging policy puzzles for international economic relations and institutions today. It is extensively and harshly debated by political leaders and diplomats, at both the national and the international levels of discourse, and is one of several issues that derailed the WTO Third Ministerial Conference in Seattle in late 1999. It also posed problems for the Fourth Ministerial Conference in Doha, Qatar, in November of 2001, and it threatens to derail the successful functions of the WTO itself.
The Case Against Military Commissions
Authors: Koh Harold Hongju
Published: April 2006

In January 2002, Zacarias Moussaoui, a French national of Moroccan descent, pleaded not guilty in Virginia federal court to six counts of conspiring to commit acts of international terrorism in connection with the September 11 attacks on the Pentagon and the World Trade Center. In other times, it would have seemed unremarkable for someone charged with conspiring to murder American citizens and destroy American property on American soil to be tried in a U.S. civilian court. More than two centuries ago, Article I, Section 8, Clause 10 of the United States Constitution granted Congress the power to "define and punish Piracies, Felonies committed on the High Seas, and Offenses against the Law of Nations," a power that Congress immediately exercised by criminalizing piracy, the eighteenth-century version of modern terrorism. Since then, Congress has criminalized numerous other international offenses. In recent decades, United States courts have decided criminal cases convicting international hijackers, terrorists, and drug smugglers, as well as a string of well-publicized civil lawsuits adjudicating gross human rights violations. Most pertinent, federal prosecutors have successfully tried and convicted in U.S. courts numerous members of Al Qaeda, the very terrorist group charged with planning the September 11 attacks, for earlier attacks on the World Trade Center and the U.S. embassies in Tanzania and Kenya.
Grigor'ev in Orenburg, 1851-1862: Russian Orientalism in the Service of Empire?
Authors: Knight Nathaniel
Published: April 2006

In December 1851, Vasilii Vasil'evich Grigor'ev, one of Russia's foremost specialists on the history and languages of Central Asia and the Near East, set off from St. Petersburg to build a new career as an administrator in the turbulent borderlands around the city of Orenburg. Grigor'ev's reasons for leaving Petersburg were both professional and personal. Unable to find an acceptable position in either the educational system or the state bureaucracy, Grigor'ev, formerly a professor at the Richelieu Lycee in Odessa, had subsisted for several years as assistant editor of the journal of the Ministry of Internal Affairs, and by 1851, with little prospect for advancement, he was willing to look further afield for employment. Grigor'ev's biographer also alludes to personal problems—a painful conflict with a close friend that made his presence in St. Petersburg unpleasant if not unbearable.
Cold War in the Kitchen: Gender and the De-Stalinization of Consumer Taste in the Soviet Union under Khrushchev
Authors: Reid Susan E.
Published: April 2006

Consumption, a key issue in the study of post-Soviet culture, was already a central concern during the Cold War. In the late 1950s and early 1960s, the Khrushchev regime staked its legitimacy at home, and its credibility abroad, on its ability to provide its population with consumer goods and a decent standard of living. Despite promising "abundance for all" as the precondition for the imminent transition to communism, the regime could not afford to leave abundance undefined. In this article, Susan E. Reid examines the way discourses of consumption, fashion, and the ideal Soviet home sought to remake consumers’ conceptions of culturedness, good taste, and comfort in rational, modern terms that took into account the regime’s ideological commitment and economic capacity. Such efforts to shape and regulate desire were directed above all at women. Reid proposes that the study of consumption provides insights into the ways in which post-Stalinist regimes manipulated and regulated people through regimes of personal conduct, taste, and consumption habits, as opposed to coercion. Indeed, the management of consumption was as significant for the Soviet system's longevity as for its ultimate collapse.