bluuebunny/crossref_metadata_2025 huggingface dataset:
Population genetic analysis of European Prunus spinosa (Rosaceae) using chloroplast DNA markers
Authors: Mohanty Aparajita , Martín Juan Pedro , Aguinagalde Itziar
Published: February 2008

Chloroplast DNA diversity in Prunus spinosa, a common shrub of European deciduous forests, was assessed using the polymerase chain reaction restriction fragment length polymorphism (PCR‐RFLP) technique. Thirty‐two haplotypes were detected in 25 populations spread across the European continent. Ten haplotypes were shared by two or more populations, and 22 were private. The major proportion of the total cpDNA diversity (HT = 0.73) was located within the populations (HS = 0.49), and differentiation between populations was low (GST = 0.33) compared with other forest species. Haplotype diversity was higher in southern Europe than in northern Europe, indicating probable localization of glacial refugia in southern Europe. The minimum‐length spanning tree of haplotypes showed incongruency between the phylogeny of haplotypes and their geographic locations. This might be the result of intensive seed movements following recolonization, which thereby erased the phylogeographic structure in P. spinosa.
Reproductive effort and herbivory timing in a perennial herb: fitness components at the individual and population levels
Authors: García María B. , Ehrlén Johan
Published: February 2008

We experimentally investigated how pollinator‐ and herbivore‐induced changes influence the performance of the long‐lived herb Primula veris. Eight treatments that corresponded to natural factors normally affecting this species were designed to enhance or reduce reproductive success and resource availability (flower removal, supplementary pollination, defoliation). During the experimental season and in the following year we quantified responses in terms of survival, growth, and seed production of reproductive plants. Matrix population models were used to calculate population growth rate using the demographic parameters recorded in permanent plots and respective treatment groups. Seed production was not limited by pollen availability, and we found no evidence of a cost of reproduction. Leaf removal had either no effect or a negative effect on future performance, depending on the timing of removal. Defoliation early in the season reduced current seed production and future growth, whereas removal during fruit development affected performance in the following year. Demographic models suggest that leaf damage has a smaller negative impact than flower removal on overall performance in this population. Our results suggest that the source‐sink paths vary over the season and that the timing of herbivory may influence the extent to which effects are carried over to subsequent reproductive seasons.
Architecture of coastal and desert Encelia farinosa (Asteraceae): consequences of plastic and heritable variation in leaf characters
Authors: Housman David C. , Price Mary V. , Redak Richard A.
Published: February 2008

The shrub Encelia farinosa (Asteraceae) exhibits geographic variation in aboveground architecture and leaf traits in parallel with environmental variation in temperature and moisture. Measurements of plants occurring across a natural gradient demonstrated that plants in desert populations produce smaller, more pubescent leaves and are more compact and branched than plants in more mesic coastal environments. This phenotypic variation is interpreted in part as adaptive genetic differentiation; small size and pubescence reduce leaf temperature and thus increase water‐use efficiency but at the cost of lower photosynthetic rate, which results in slower growth and more compact growth form. We explored the basis of phenotypic variation by planting seed offspring from coastal and desert populations in common gardens in both environments. Phenotypic differences among populations persisted in both common gardens, suggesting a genetic basis for trait variation. Desert offspring outperformed coastal offspring in the desert garden, suggesting superior adaptation to hot, dry conditions. Herbivore damage was greater for all offspring in the coastal garden. Phenotypic characters also showed plastic responses; all offspring had smaller, more pubescent leaves and more compact growth form in the desert garden. Our results confirm that leaf size and pubescence are heritable characters associated with pronounced variation in plant architecture.
Separate effects of human visitation and touch on plant growth and herbivory in an old‐field community
Authors: Cahill James F. , Castelli Jeffrey P. , Casper Brenda B.
Published: February 2008

Although animal scientists have long been aware that methods used to measure an experimental system can affect the subject of measurement, similar confounding effects of commonly used field methods have only recently been acknowledged by plant ecologists. Here we demonstrate significant effects of weekly visitation (walking up to a focal plant) and handling (taking morphological measures) on plant growth and herbivory in an old‐field community. Of the three species examined, Apocynum cannabinum was the most severely affected by our treatments. For Apocynum, weekly visitations resulted in a positive relationship between initial and final size, which did not occur in the unvisited plants. Visitation also increased leaf herbivory, resulting in a reduced leaf:stem biomass ratio. Handling the plants nearly doubled the proportion of individuals with a stem borer emergence hole. Growth of the other species in this study, Potentilla recta and Erigeron philadelphicus, was altered by either visitation or visitation plus handling. Visiting plants in order to observe them and touching them as one would when making morphological measurements can have important biological consequences. We suggest that plant ecologists treat repeated entry into a natural system as a research method, subject to the same scrutiny and justification as all other experimental methods.
Monophyly of the Convolvulaceae and circumscription of their major lineages based on DNA sequences of multiple chloroplast loci
Authors: Stefanović Saša , Krueger Lori , Olmstead Richard G.
Published: February 2008

Convolvulaceae, a large family of worldwide distribution, exhibit a rich diversity of morphological characteristics and ecological habitats. Previous efforts to systematize this diversity without a cladistic phylogenetic framework have disagreed on the circumscription of the family as well as tribal composition and relationship. In order to circumscribe the family and assess the relationships among its major lineages, a broad data set was constructed containing representatives of all ten recognized tribes of Convolvulaceae plus representatives of putatively related families within Asteridae. This is done by using four chloroplast regions: rbcL, atpB, psbE‐J operon, and trnL‐trnF intron/spacer. The results indicate that Convolvulaceae are monophyletic and sister to Solanaceae. Two of the three groups that have been proposed previously as separate families, Cuscuta and Dichondreae, are nested within the Convolvulaceae in this analysis, and the third, Humbertia, is the sister to all other members of the family. The exact position of Cuscuta could not be ascertained, but some alternatives were rejected with confidence. The study identified several distinct monophyletic groups, some of which correspond to earlier taxonomic treatments. Close relationships of tribes Hildebrandtieae with Cresseae and Ipomoeeae with Argyreieae (forming Echinoconieae) were confirmed. The polyphyly of Merremieae, Convolvuleae, Poraneae, and Erycibeae is first identified in this study.
Eucommia (Eucommiaceae), a potential biothermometer for the reconstruction of paleoenvironments
Authors: Wang Yu‐Fei , Li Cheng‐Sen , Collinson Margaret E. , Lin Jian , Sun Qi‐Gao
Published: February 2008

The living trees of Eucommia ulmoides, an endemic species in China, grow from 200 to 1700 m above sea level, within the geographic range from 102° E to 118° E and from 25° N to 35° N. Spring temperatures in these regions vary from 12.3°C to 20.1°C. A physiological study (using germination tests) of E. ulmoides has been undertaken to test the role of spring temperature as a factor controlling the distribution of Eucommia. Results show that the spring temperature is a limiting factor for Eucommia seed germination and hence for the distribution pattern of the genus. The suitable range of temperature for seed germination, established experimentally, is from 13°C to 22°C, with an optimum of 18°C. Specimens of fossil Eucommia cf. ulmoides, preserved as a branch segment and leaves, showing the distinctive latex, were found in Middle Miocene sediments of Shanwang Formation, Shandong Province, East China. If the climatic tolerances documented here for E. ulmoides are extrapolated to Shanwang, they are in fact consistent with other predictions of the paleoclimate at this site, indicative of the potential value of Eucommia as a biothermometer. These Miocene fossils, and one previously described Eocene fruit specimen, prove the former existence of Eucommia in China in addition to North America and Europe. This confirms that the genus is not a recent arrival in China and extends our understanding of the past biogeography of the genus.
Phylogeny of the sundews, Drosera (Droseraceae), based on chloroplast rbcL and nuclear 18S ribosomal DNA Sequences
Authors: Rivadavia Fernando , Kondo Katsuhiko , Kato Masahiro , Hasebe Mitsuyasu
Published: February 2008

The sundew genus Drosera consists of carnivorous plants with active flypaper traps and includes nearly 150 species distributed mainly in Australia, Africa, and South America, with some Northern Hemisphere species. In addition to confused intrageneric classification of Drosera, the intergeneric relationships among the Drosera and two other genera in the Droseraceae with snap traps, Dionaea and Aldrovanda, are problematic. We conducted phylogenetic analyses of DNA sequences of the chloroplast rbcL gene for 59 species of Drosera, covering all sections except one. These analyses revealed that five of 11 sections, including three monotypic sections, are polyphyletic. Combined rbcL and 18S rDNA sequence data were used to infer phylogenetic relationships among Drosera, Dionaea, and Aldrovanda. This analysis revealed that all Drosera species form a clade sister to a clade including Dionaea and Aldrovanda, suggesting that the snap traps of Aldrovanda and Dionaea are homologous despite their morphological differences. MacClade reconstructions indicated that multiple episodes of aneuploidy occurred in a clade that includes mainly Australian species, while the chromosome numbers in the other clades are not as variable. Drosera regia, which is native to South Africa, and most species native to Australia, were clustered basally, suggesting that Drosera originated in Africa or Australia. The rbcL tree indicates that Australian species expanded their distribution to South America and then to Africa. Expansion of distribution to the Northern Hemisphere from the Southern Hemispere occurred in a few different lineages.
Asynchronous development of stigmatic receptivity in the pear (Pyrus communis; Rosaceae) flower
Authors: Sanzol Javier , Rallo Pilar , Herrero María
Published: February 2008

While stigma anatomy is well documented for a good number of species, little information is available on the acquisition and cessation of stigmatic receptivity. The aim of this work is to characterize the development of stigma receptivity, from anthesis to stigma degeneration, in the pentacarpellar pear (Pyrus communis) flower. Stigma development and stigmatic receptivity were monitored over two consecutive years, as the capacity of the stigmas to offer support for pollen germination and pollen tube growth. In an experiment where hand pollinations were delayed for specified times after anthesis, three different stigmatic developmental stages could be observed: (1) immature stigmas, which allow pollen adhesion but not hydration; (2) receptive stigmas, which allow proper pollen hydration and germination; and (3) degenerated stigmas, in which pollen hydrates and germinates properly, but pollen tube growth is impaired soon after germination. This developmental characterization showed that stigmas in different developmental stages coexist within a flower and that the acquisition and cessation of stigmatic receptivity by each carpel occur in a sequential manner. In this way, while the duration of stigmatic receptivity for each carpel is rather short, the flower has an expanded receptive period. This asynchronous period of receptivity for the different stigmas of a single flower is discussed as a strategy that could serve to maximize pollination resources under unreliable pollination conditions.
Genetic structure of an endangered plant,Antirrhinum microphyllum(Scrophulariaceae): allozyme and RAPD analysis
Authors: Torres Elena , Iriondo José M. , Pérez César
Published: February 2008

Thirteen allozyme loci and 68 random amplified polymorphic DNA (RAPD) markers were analyzed to assess the genetic diversity and population structure of threatenedAntirrhinum microphyllum(Scrophulariaceae), a narrow endemic of central Spain known from only four populations. According to allozyme data, species genetic diversity (p= 46.15%,A= 2.61, andHe= 0.218), as well as within‐population genetic diversity (p= 44.23%,A= 2.10, andHe= 0.204), were high when compared to average estimates for other narrowly distributed plant species. Ninety‐four percent of species genetic diversity corresponded to within‐population genetic diversity. Nevertheless, significant differences were found among populations in allele frequencies of four of the six polymorphic loci, and three private alleles were detected. Inbreeding coefficients (FIS) suggest that populations are structured in genetic neighborhoods. The RAPDs also showed high levels of genetic diversity (p= 89.71% andHe= 0.188 at the species level, andp= 67.65% andHe= 0.171 at the population level). Nei's genetic distances estimated both from allozymes and RAPDs indicated low differentiation among populations. In spite of this, the low frequencies of certain alleles and the presence of private alleles indicate that efforts should be made to conserve all four remaining populations.
Repeat intercontinental dispersal and Pleistocene speciation in disjunct Mediterranean and desert Senecio (Asteraceae)
Authors: Coleman Max , Liston Aaron , Kadereit Joachim W. , Abbott Richard J.
Published: February 2008

To explore the biogeographic history of Mediterranean/arid plant disjunctions, Old and New World Senecio sect. Senecio were analyzed phylogenetically using nuclear ribosomal DNA sequences (ITS). A clade corresponding to sect. Senecio was strongly supported. Area optimization indicated this clade to be of southern African origin. The Mediterranean and southern African floras were not distinguishable as sources of the main New World lineage, estimated to have become established during the middle Pliocene. Another previously suspected recent dispersal to the New World from the Mediterranean was confirmed for the recently recognized disjunction in S. mohavensis. The loss of suitable land connections by the Miocene means that both New World lineages must represent long‐distance dispersal, providing the first evidence of repeat intercontinental dispersal in a Mediterranean group. In contrast, migration within Africa may have utilized an East African arid corridor. Recent dispersal to northern Africa is supported for S. flavus, which formed part of a distinct southern African lineage. Novel pappus modifications in both disjunct species may have enabled dispersal by birds. An estimated early Pliocene origin of sect. Senecio coincides with the appearance of summer‐dry climate. However, diversification from 1.6 BP highlights the importance of Pleistocene climate fluctuations for speciation.
Vegetative regeneration in invasiveReynoutria(Polygonaceae) taxa: the determinant of invasibility at the genotype level
Authors: Pyšek Petr , Brock John H. , Bímová Kateřina , Mandák Bohumil , Jarošík Vojtěch , Koukolíková Irena , Pergl Jan , Štěpánek Jan
Published: February 2008

Vegetative regeneration of individual genotypes of AsianReynoutriataxa, which are invasive in the Czech Republic, was studied inR. sachalinensis(five genotypes),R. japonica(a single genotype present in the country), and their hybridR. ×bohemica(nine genotypes). Identity of genotypes was confirmed by isozyme analysis. Ten rhizome segments of each genotype were planted in a randomized block design. After 30 d, the regeneration rate of each genotype was measured as the proportion of rhizomes that produced shoots. Emergence time and final mass of each shoot were recorded. The regeneration rate and final shoot mass were significantly affected by genotype inR. ×bohemicabut not inR. sachalinensis. InR. ×bohemica, easily regenerating genotypes grew faster. Regeneration characteristics that crucially contribute to the fitness of these vegetatively spreading plants are closely related to each other. In genotypes with a low regeneration rate, early‐emerging shoots produced more biomass, while in those with a high regeneration rate, shoot mass was independent of emergence time. Mean clone size recorded in the field was marginally significantly related to emergence time during regeneration; regeneration characteristics might thus affect the extent ofR. ×bohemicainvasion at a regional scale. Hybrids genetically intermediate between the parents regenerated better than those closely related to parents. Novel hybrid invasive genotypes may be produced by rare sexual reproduction, fixed by clonal growth, and present a previously unknown threat to native vegetation.
Characterization and adaptive evolution of α‐tubulin genes in the Miscanthus sinensis complex (Poaceae)
Authors: Wu Wen‐Luan , Schaal Barbara A. , Hwang Chung‐Yu , Hwang Ming‐Der , Chiang Yu‐Chung , Chiang Tzen‐Yuh
Published: February 2008

To investigate the organization of and mode of selection in the α‐tubulin genes, full‐length α‐tubulin genes were cloned from four intraspecific taxa of Miscanthus sinensis and its close relatives M. floridulus and M. condensatus using standard polymerase chain reaction (PCR) and rapid amplification of genomic ends (RAGE)‐PCR strategies. Genealogical analysis of angiosperms recovered a monophyletic group of Miscanthus α‐tubulin genes, which is homologous to the tua5 locus of maize. Two clusters of nearly equal frequency revealed paraphyly within each Miscanthus taxon. Between‐cluster recombination was frequent. Additional evidence for co‐occurrence of two haplotypes within individuals and a large‐scale crossover all suggested a likely allelic relationship between the Miscanthus clusters. Given a long between‐species divergence time in Miscanthus, wide occurrence of the trans‐species polymorphisms in α‐tubulin genes and the approximately equal frequency of each allelic type make it extremely unlikely that α‐tubulin diversity has been maintained under neutrality. Balancing selection may have contributed to such an apportioning of genetic variability as well as to high levels of genetic variation in α‐tubulin and higher substitution rates at synonymous sites of exons than at intron bases of M. sinensis. In addition, certain effects of demographic oscillation may have distorted the scenario of a functional locus operating under balancing selection.
Floral development and morphology of Vochysiaceae. I. The structure of the gynoecium
Authors: Litt Amy , Stevenson Dennis W.
Published: February 2008

Vochysiaceae are divided into two tribes on the basis of ovary structure (superior trilocular or inferior unilocular). The superior trilocular ovary has been considered basal in the family, and the term “pseudomonomerous” was used to indicate the presumed evolutionary derivation of the unilocular condition from the trilocular. However, recent evidence that Vochysiaceae are Myrtalean suggests that the superior ovary may be secondarily derived. In addition, published figures cast doubt on the interpretation of the putatively unilocular ovaries. To understand these features, floral ontogeny and anatomy were examined using scanning electron microscopy and serial sectioning. In all taxa examined, the ovary develops in an epigynous fashion, on a concave floral apex, supporting the hypothesis that the superior ovary is secondarily derived. Subsequent to initiation of the ovary, differential growth results in ovaries that are superior, inferior, or partly inferior in different genera. Sections of floral buds of the two unilocular genera, Erisma and Erismadelphus, show aborted locules in the latter but not in the former. The application of the term “pseudomonomerous” to both genera obscures this significant difference. The position of the placenta in the truly unilocular genus varies among species, suggesting a character transformation series from multilocular through intermediates to truly unilocular.
Floral development and morphology of Vochysiaceae. II. The position of the single fertile stamen
Authors: Litt Amy , Stevenson Dennis W.
Published: February 2008

A conspicuous feature of Vochysiaceae flowers is their single fertile stamen. In some genera, the stamen is in front of a petal, whereas in others it is in front of a sepal. This difference has been attributed to two independent reductions, which implies the stamen is not homologous across the family. The observation that genera with an antesepalous stamen have only one petal, whereas those with an antepetalous stamen have three or five petals, led us to the hypothesis that in all genera the stamen arises in an antepetalous position, but that it is displaced during development in single‐petaled taxa. We examined developing buds of five genera using scanning electron microscopy and serial sectioning and conclude that the stamen in all genera is fundamentally antepetalous. The stamen is not displaced. The petal, however, appears to be displaced in some genera. Further, the position of the fertile stamen in Erisma has been misinterpreted. We discuss the evolution of the androecium in this family in a phylogenetic context and consider the significance of symmetry and of loss vs. suppression in the development of Vochysiaceae flowers.
The Enigmatic Paleozoic plants Spermopteris and Phasmatocycas reconsidered
Authors: Axsmith Brian J. , Serbet Rudolph , Krings Michael , Taylor Thomas N. , Taylor Edith L. , Mamay Sergius H.
Published: February 2008

Ovule‐bearing leaves from the Paleozoic of North America assigned to Spermopteris and Phasmatocycas have been interpreted as primitive cycad megasporophylls. According to this hypothesis, Cycas megasporophylls were derived from a Spermopteris‐like ancestor via Phasmatocycas and various other taeniopterid forms. This putative transformation entailed the phyletic shift of ovule attachment from the abaxial lamina surface of Spermopteris to the leaf midrib in Phasmatocyas. However, reexamination of the original Spermopteris specimens from the Lawrence Shale of Kansas has shown that the ovules are attached to the leaf midrib. Therefore, Spermopteris and Phasmatocyas differ only in a few details of lamina morphology. The apical cleft of the ovules of both forms is interpreted as an original feature rather than a preservational artifact; however, the abaxial flange is probably a result of compression of a terete midrib. Spermopteris is typified by sterile specimens of Taeniopteris coriacea from Europe, which are of uncertain affinity to the fertile leaves. Therefore, we propose that the ovule‐bearing leaves now known as Spermopteris coriacea be named as a new species of Phasmatocycas (Phasmatocycas bridwellii sp. nov.). The new concept of Phasmatocyas is less cycad‐like than previously thought, and the phylogenetic position of the genus is unclear.
Under how wide a set of conditions will nonrandom mating occur in Raphanus sativus (Brassicaceae)?
Authors: Shaner Marieken G. M. , Marshall Diane L.
Published: February 2008

Studies of the weedy annual Raphanus sativus have demonstrated that nonrandom mating, a prerequisite for sexual selection, can occur in greenhouse plants. To determine whether this nonrandom mating pattern can occur under a wide range of conditions, including conditions that might occur in the field, we considered variation in both maternal condition and pollen load size. Maternal condition was varied by altering the watering regime. Pollen load size was varied from approximately 26 to 343 pollen grains per stigma. At the smallest pollen load size, patterns of seed paternity were altered in two of the three pollen donor pairs; seed paternity became more equal among donors. For one of three pollen donor pairs, seed paternity was more divergent among donors on stressed maternal plants. Finally, for one pollen donor pair, rank order of pollen donor performance changed from the medium to the small pollen loads on stressed vs. control maternal plants. Thus, some field conditions may alter patterns of nonrandom mating in wild radish.
Linking pollinator visitation rate and pollen receipt
Authors: Cayenne Engel E. , Irwin Rebecca E.
Published: February 2008

The majority of flowering plants require animals for pollination, a critical ecosystem service in natural and agricultural systems. However, quantifying useful estimates of pollinator visitation rates can be nearly impossible when pollinator visitation is infrequent. We examined the utility of an indirect measure of pollinator visitation, namely pollen receipt by flowers, using the hummingbird‐pollinated plant, Ipomopsis aggregata (Polemoniaceae). Our a priori hypothesis was that increased pollinator visitation should result in increased pollen receipt by stigmas. However, the relationship between pollinator visitation rate and pollen receipt may be misleading if pollen receipt is a function of both the number of pollinator visits and variation in pollinator efficiency at depositing pollen, especially in the context of variable floral morphology. Therefore, we measured floral and plant characters known to be important to pollinator visitation and/or pollen receipt in I. aggregata (corolla length and width and plant height) and used path analysis to dissect and compare the effect of pollinator visitation rate vs. pollinator efficiency on pollen receipt. Of the characters we measured, pollinator visitation rate (number of times plants were visited multiplied by the mean percentage of flowers probed per visit) had the strongest direct positive effect on pollen receipt, explaining 36% of the variation in pollen receipt. Plant height had a direct positive effect on pollinator visitation rate and an indirect positive effect on pollen receipt. Despite the supposition that floral characters would directly affect pollen receipt as a result of changes in pollinator efficiency, corolla length and width only weakly affected pollen receipt. These results suggest a direct positive link between pollinator visitation rate and pollen receipt across naturally varying floral morphology in I. aggregata. Understanding the relationship between pollinator visitation rate and pollen receipt may be of critical importance in systems where pollinator visitation is difficult to quantify.
Population genetic structure of Venezuelan chiropterophilous columnar cacti (Cactaceae)
Authors: Nassar Jafet M. , Hamrick J. L. , Fleming Theodore H.
Published: February 2008

We conducted allozyme surveys of three Venezuelan self‐incompatible chiropterophilous columnar cacti: two diploid species,Stenocereus griseusandCereus repandus, and one tetraploid,Pilosocereus lanuginosus. The three cacti are pollinated by bats, and both bats and birds disperse seeds. Population sampling comprised two spatial scales: all Venezuelan arid zones (macrogeographic) and two arid regions in northwestern Venezuela (regional). Ten to 15 populations and 17–23 loci were analyzed per species. Estimates of genetic diversity were compared with those of other allozyme surveys in the Cactaceae to examine how bat‐mediated gene dispersal affects the population genetic attributes of the three cacti. Genetic diversity was high for both diploid (Ps= 94.1–100,Pp= 56.7–72.3,Hs= 0.182–0.242,Hp= 0.161–0.205) and tetraploid (Ps= 93.1,Pp= 76.1,Hs= 0.274,Hp= 0.253) species. Within‐population heterozygote deficit was detected in the three cacti at macrogeographic (FIS= 0.145–0.182) and regional (FIS= 0.057–0.174) levels. Low genetic differentiation was detected at both macrogeographic (GST= 0.043–0.126) and regional (GST= 0.009–0.061) levels for the three species, suggesting substantial gene flow among populations. Gene exchange among populations seems to be regulated by distance among populations. Our results support the hypothesis that bat‐mediated gene dispersal confers high levels of genetic exchange among populations of the three columnar cacti, a process that enhances levels of genetic diversity within their populations.
Angiosperm phylogeny based on <011>matK sequence information
Authors: Hilu Khidir W. , Borsch Thomas , Müller Kai , Soltis Douglas E. , Soltis Pamela S. , Savolainen Vincent , Chase Mark W. , Powell Martyn P. , Alice Lawrence A. , Evans Rodger , Sauquet Hervé , Neinhuis Christoph , Slotta Tracey A. B. , Rohwer Jens G. , Campbell Christopher S. , Chatrou Lars W.
Published: February 2008

Plastid matK gene sequences for 374 genera representing all angiosperm orders and 12 genera of gymnosperms were analyzed using parsimony (MP) and Bayesian inference (BI) approaches. Traditionally, slowly evolving genomic regions have been preferred for deep‐level phylogenetic inference in angiosperms. The matK gene evolves approximately three times faster than the widely used plastid genes rbcL and atpB. The MP and BI trees are highly congruent. The robustness of the strict consensus tree supercedes all individual gene analyses and is comparable only to multigene‐based phylogenies. Of the 385 nodes resolved, 79% are supported by high jackknife values, averaging 88%. Amborella is sister to the remaining angiosperms, followed by a grade of Nymphaeaceae and Austrobaileyales. Bayesian inference resolves Amborella + Nymphaeaceae as sister to the rest, but with weak (0.42) posterior probability. The MP analysis shows a trichotomy sister to the Austrobaileyales representing eumagnoliids, monocots + Chloranthales, and Ceratophyllum + eudicots. The matK gene produces the highest internal support yet for basal eudicots and, within core eudicots, resolves a crown group comprising Berberidopsidaceae/Aextoxicaceae, Santalales, and Caryophyllales + asterids. Moreover, matK sequences provide good resolution within many angiosperm orders. Combined analyses of matK and other rapidly evolving DNA regions with available multigene data sets have strong potential to enhance resolution and internal support in deep level angiosperm phylogenetics and provide additional insights into angiosperm evolution.
Chromosome studies of cheilanthoid ferns (Pteridaceae: Cheilanthoideae) from the western United States and Mexico
Authors: Windham Michael D. , Yatskievych George
Published: February 2008

Although analyses of chromosome numbers represent a fundamental step in the study of any group of organisms, the xeric‐adapted cheilanthoid ferns (Pteridaceae: subfamily Cheilanthoideae) have received little attention from cytogeneticists due to the difficulty in obtaining samples and accurate chromosome counts. In an effort to clarify patterns of chromosomal evolution in this group, we present 131 chromosome counts representing 75 taxa of cheilanthoid ferns from the western United States and Mexico. First reports are provided for 24 taxa, including the first count for the genus Cheiloplecton. Nine other taxa yielded numbers that had not been reported previously. Our data suggest that chromosome base numbers are more stable than previously thought and that much of the reported variation may involve erroneous counts. When coupled with published DNA sequence data, our counts suggest that the plesiomorphic base number of subfamily Cheilanthoideae is x = 30 and that x = 29 has arisen just once or twice among the taxa studied.
The development of enantiostyly
Authors: Jesson Linley K. , Kang Julie , Wagner Sara L. , Barrett Spencer C. H. , Dengler Nancy G.
Published: February 2008

Enantiostyly, the deflection of the style either to the left (left‐styled) or right (right‐styled) side of the floral axis, has evolved in at least ten angiosperm families. Two types of enantiostyly occur: monomorphic enantiostyly, in which individuals exhibit both stylar orientations, and dimorphic enantiostyly, in which the two stylar orientations occur on separate plants. To evaluate architectural or developmental constraints on the evolution of both forms of enantiostyly, we examined inflorescence structure and floral development among unrelated enantiostylous species. We investigated relations between the position of left‐ and right‐styled flowers and inflorescence architecture in four monomorphic enantiostylous species, and we examined the development of enantiostyly in nine monomorphic and dimorphic enantiostylous species from five unrelated lineages. The location of left‐ and right‐styled flowers within inflorescences ranged from highly predictable (in Solanum rostratum) to random (in Heteranthera mexicana). There were striking differences among taxa in the timing of stylar bending. In Wachendorfia paniculata, Dilatris corymbosa, and Philydrum lanuginosum, the style deflected in the bud, whereas in Heteranthera spp., Monochoria australasica, Cyanella lutea, and Solanum rostratum, stylar bending occurred at the beginning of anthesis. Comparisons of organ initiation and development indicated that asymmetries along the left‐right axis were expressed very late in development, despite the early initiation of a dorsiventral asymmetry. We suggest that the evolution of dimorphic enantiostyly from monomorphic enantiostyly may be constrained by a lack of left‐right positional information in the bud.
Effects of simulated herbivory and resources on Chinese tallow tree (Sapium sebiferum, Euphorbiaceae) invasion of native coastal prairie
Authors: Rogers William E. , Siemann Evan
Published: February 2008

Trade‐offs associated with maintaining herbivory resistance and herbivory tolerance are frequently inferred in plant life histories. Invasive success for many non‐native plants is often attributed to novel resistance that repels native herbivores. Chinese tallow tree (Sapium sebiferum, Euphorbiaceae) is a non‐native invader that threatens ecosystems throughout the southeastern United States, including imperiled coastal prairie regions. Low herbivore loads due to costly resistance are generally assumed to give Sapium a competitive advantage over native plants. We predicted that if Sapium experienced higher damage levels it would show significant decreases in growth and reduced ability to compete with native prairie vegetation. We conducted full‐factorial, paired greenhouse and field experiments designed to assess the effects of simulated leaf herbivory on Sapium growth in the presence of prairie vegetation at different levels of light and nitrogen. Contrary to our expectations, neither low‐intensity, chronic defoliation nor high‐intensity, acute defoliation negatively affected Sapium seedlings in any resource combination in either experiment. These studies reveal that Sapium possesses considerable phenotypic plasticity, and herbivory tolerance is a newly appreciated trait that likely contributes to its invasive potential.
Reexamination of a canonical model for plant organ biomass partitioning
Authors: Niklas Karl J.
Published: February 2008

A previously proposed “canonical” model for the scaling relations among leaf, stem, and root biomass (ML, MS, and MR, respectively) asserts that the proportional relations ML ∝ MS3/4 ∝ MR3/4 and MS ∝ MR hold across seed plant species. This model is scrutinized by determining whether the scaling relations between ML, MS, and MR vs. basal stem diameter DS and between ML, MS, and MR vs. plant height h are logically consistent with previously predicted scaling exponents. For example, if ML is observed to scale as the 2‐power of DS and the model asserts that ML ∝ MS3/4, then MS must scale as the 8/3‐power of DS if the model is valid. Using a large data base for species with self‐supporting stems, statistical support was found for most such comparisons between predicted and observed scaling relationships. However, this judgement is predicated on (1) the assertion that the scaling exponents for MR with respect to DS (or h) are numerically “deflated” due to a systematic underestimate of fine and small root biomass and (2) the stringent protocol used to calculate the 95% confidence intervals of scaling exponents, which favors rejection of the model. In light of these features, the “canonical” model is logically consistent with the new scaling relations reported here. Therefore, the model is judged valid within the context of this evaluation.
On the economy and safety of hollow non‐septate peduncles
Authors: Hogan Christopher J. , Niklas Karl J.
Published: February 2008

We examined the allometry and mechanical properties of the peduncles of Hieracium pilosella and other species in the Asteraceae (H. aurantiacum, Taraxicum officinale, Tragopogon pratensi) to evaluate the hypothesis that tapered, tubular, and non‐septate peduncles optimize the trade‐offs among stem biomass allocation, elevating flowers and thus their wind‐dispersed fruits, and the requirement for a factor of safety against mechanical failure. This hypothesis was evaluated by comparing peduncle morphometry (e.g., biomass Ms, floral biomass Mf, and length L) and mechanical properties (e.g., bending rigidity EI) for populations growing in windy and wind‐sheltered sites as well as transplants between sites. Regardless of ambient wind speeds, Ms ∝ L4/3 and EI ∝ L11/4 ∝ Ms5/3, whereas Mf /Ms ∝ L−1.15, i.e., peduncles disproportionately increase in their biomass as they increase in length, but mechanically support a disproportionately smaller floral biomass relative to their biomass. Calculations show that the tall peduncles from wind‐sheltered sites have a larger fruit dispersal range and a lower factor of safety than the shorter peduncles produced in open sites. These and other observations are interpreted to indicate that tubular peduncles enhance relative fitness in terms of propagule dispersal (but not propagule number per stem) while maintaining a sufficient factor of safety against mechanical failure.
Random amplified polymorphic DNA assessment of diversity in western Mediterranean populations of the seagrass Posidonia oceanica
Authors: Jover Maria Angeles , del Castillo‐Agudo Lucas , Garcia‐Carrascosa Manuel , Segura Juan
Published: February 2008

Posidonia oceanica is an endemic Mediterranean seagrass species that has often been assumed to contain low levels of genetic diversity. Random amplified polymorfic DNA (RAPD) markers were used to assess genetic diversity among five populations from three geographical regions (north, central, and south) of the western Mediterranean Sea. Stranded germinating seeds from one of the central populations were also included in the analysis. Forty‐one putative genets were identified among 76 ramets based on 28 RAPD markers. Genotypic diversity strongly depended on the spatial structure, age, and maturity of the meadows. The lowest clonal diversity was found in the less structured and youngest prairies. Conversely, a high genotypic diversity was found in the highly structured meadows. The genotypic diversity in these meadows was at the same level as in P. australis and higher than previously reported data for P. oceanica populations in the Tyrrhenian Sea near the coast of Italy.
Floral scents affect reproductive success in fly‐pollinated Alocasia odora (Araceae)
Authors: Miyake Takashi , Yafuso Masako
Published: February 2008

We evaluated the role of floral scents in the reproductive success of Alocasia odora C. Koch (Araceae). Alocasia odora is pollinated by its specific pollinators, Colocasiomyia alocasiae (Okada) and C. xenalocasiae (Okada) (Diptera: Drosophilidae). These flies use the spadix of A. odora as breeding sites. The appendix, which is at an upper part of the spadix and is the most attractive region, attracted these pollinators by emitting volatiles, although the male zone of the inflorescence was also attractive. The number of flies attracted was positively correlated with appendix size. During the pistillate phase of the protogynous spadix, attracted flies aggregated in the lower part (female zone) to mate, lay eggs, and perhaps obtain nutrients. The flies moved to the upper part (male zone) of the spadix by the tightening of the constriction separating the upper and lower parts, and then the staminate phase started. This movement of the flies on the spadix promotes outcrossing of A. odora. Removal of the appendix or the whole upper part of the spadix resulted in much reduced fruit set, suggesting that the absence of the scent‐producing region leads to insufficient pollination because of reduced pollinator attraction.
Gunnerales are sister to other core eudicots: implications for the evolution of pentamery
Authors: Soltis Douglas E. , Senters Anne E. , Zanis Michael J. , Kim Sangtae , Thompson James D. , Soltis Pamela S. , Ronse De Craene Louis P. , Endress Peter K. , Farris James S.
Published: February 2008

Phylogenetic relationships among many lineages of angiosperms have been clarified via the analysis of large molecular data sets. However, with a data set of three genes (18S rDNA, rbcL, and atpB), relationships among lineages of core eudicots (Berberidopsidales, Caryophyllales, Gunnerales, Santalales, Saxifragales, asterids, rosids) remain essentially unresolved. We added 26S rDNA sequences to a three‐gene matrix for 201 eudicots (8430 base pair aligned nucleotides per taxon). Parsimony analyses provided moderate (84%) jackknife support for Gunnerales, which comprise the two enigmatic families Gunneraceae and Myrothamnaceae, as sister to all other core eudicots. This position of Gunnerales has important implications for floral evolution. A dimerous or trimerous perianth is frequently encountered in early‐diverging eudicots (e.g., Buxaceae, Proteales, Ranunculales, Trochodendraceae), whereas in core eudicots, pentamery predominates. Significantly, dimery is found in Gunneraceae and perhaps Myrothamnaceae (the merosity of the latter has also been interpreted as labile). Parsimony reconstructions of perianth merosity demonstrate lability among early‐diverging eudicots and further indicate that a dimerous perianth could be the immediate precursor to the pentamerous condition characteristic of core eudicots. Thus, the developmental canalization that yielded the pentamerous condition of core eudicots occurred after the node leading to Gunnerales.
Phylogenetic analysis of Asplenium subgenus Ceterach (Pteridophyta: Aspleniaceae) based on plastid and nuclear ribosomal ITS DNA sequences
Authors: Van den heede Caroline J. , Viane Ronald L. L. , Chase Mark W.
Published: February 2008

Phylogenetic relationships among 20 taxa of the fern genus Asplenium subgenus Ceterach (Filicopsida, represented by 73 accessions) were investigated using DNA sequence data from the nuclear ribosomal internal transcribed spacers (ITS nDNA) and plastid trnL‐F intergenic spacer. In addition, a single sample per taxon was used in an analysis of the plastid rbcL gene. Chromosome counts were determined for all the samples, and these demonstrated a range from diploid to octoploid. Analyses of the DNA sequence data indicated that Asplenium subgenus Ceterach is polyphyletic, implicating homoplasy in the characters previously used to circumscribe this taxon. Plastid trnL‐F and rbcL analyses resulted in identical tree topologies. The trees produced from the separate plastid and nuclear matrices agree in (1) the recognition of identical groups of accessions corresponding to A. dalhousiae, A. ceterach, A. aureum, A. cordatum, A. phillipsianum, and A. haughtonii; (2) the division of A. subg. Ceterach into two subclades, a Eurasian‐Macaronesian and a strictly African alliance; (3) the position of A. dalhousiae as a member of the former subclade; (4) the lack of genetic variation in A. cordatum despite its morphological variability; and (5) the clustering of each autopolyploid with their diploid ancestor. However, the plastid and nuclear trees differ in their placement of A. haughtonii and A. dalhousiae, which might be due to different evolutionary histories of nuclear and plastid genomes, and is possibly an indication of ancient hybridization. The analyses confirm the existence of several strictly African taxa. Asplenium phillipsianum and A. cordatum each form species complexes of diploid and autopolyploid taxa, from which a third, morphologically intermediate, allotetraploid species has originated. Asplenium haughtonii is a distinct endemic species from Saint Helena. The maternally inherited plastid sequences support the hypothesis that A. aureum is an ancestor of A. lolegnamense and of A. octoploideum. Because gene conversion did not eliminate divergent ITS alleles in the allopolyploids, their reticulate ancestry could be demonstrated. Biparentally inherited nrITS sequences support the allopolyploid status of A. aureum, A. lolegnamense, and A. punjabense, indicating they share the ancestral A. javorkeanum genome.
TheBio‐Logic and machinery of plant morphogenesis
Authors: Niklas Karl J.
Published: February 2008

Morphogenesis (the development of organic form) requires signal‐trafficking and cross‐talking across all levels of organization to coordinate the operation of metabolic and genomic networked systems. Many biologists are currently converging on the pictorial conventions of computer scientists to render biological signaling as logic circuits supervising the operation of one or more signal‐activated metabolic or gene networks. This approach can redact and simplify complex morphogenetic phenomena and allows for their aggregation into diagrams of larger, more “global” networked systems. This conceptualization is discussed in terms of how logic circuits and signal‐activated subsystems work, and it is illustrated for examples of increasingly more complex morphogenetic phenomena, e.g., auxin‐mediated cell expansion, entry into the mitotic cell cycle phases, and polar/lateral intercellular auxin transport. For each of these phenomena, a posited circuit/subsystem diagram draws rapid attention to missing components, either in the logic circuit or in the subsystem it supervises. These components must be identified experimentally if each of these basic phenomena is to be fully understood. Importantly, the power of the circuit/subsystem approach to modeling developmental phenomena resides not in its pictorial appeal but in the mathematical tools that are sufficiently strong to reveal and quantify the synergistics of networked systems and thus foster a better understanding of morphogenesis.
Lack of latitudinal trends in wood anatomy of Dodonaea viscosa (Sapindaceae), a species with a worldwide distribution
Authors: Liu Jianquan , Noshiro Shuichi
Published: February 2008

Latitudinal or altitudinal variation in several anatomical characters of wood is common for woody dicotyledonous genera with a wide distribution, but whether such variation exists at the species level is disputed. Latitudinal and altitudinal trends in wood anatomy of Dodonaea viscosa were studied, using 102 samples collected between 41.2° S and 33.3° N latitude and 7–2750 m altitude. We studied variation in four quantitative features: vessel element length, fiber length, vessel frequency, and tangential vessel diameter. Ontogenetic trends were minimal with a slight decrease or increase in the innermost stem and were negligible among the studied specimens. Throughout the distributional range of the species, no latitudinal trends were detected in either the Northern or Southern Hemispheres. Altitudinal trends were also nonexistent, except for two features in specimens from China and Japan. Absence of latitudinal or altitudinal trends in this widely distributed species suggests that in some species the species‐level variation in wood anatomy is not controlled by ecological gradients.