bluuebunny/crossref_metadata_2025 huggingface dataset:
Outcrossing rates in the gynomonoecious‐gynodioecious species Dianthus sylvestris (Caryophyllaceae)
Authors: Collin Carine L. , Shykoff Jacqui A.
Published: February 2008

Some species described as gynodioecious are truly gynomonoecious‐gynodioecious. Three distinct phenotypes may be found in their natural populations—female and hermaphrodite pure‐sexed plants bearing either only pistillate or perfect flowers, respectively, and mixed plants bearing both types of flowers. In one such species, Dianthus sylvestris, we investigated mating system parameters using allozyme data. Outcrossing rates and correlations of outcrossed paternity were calculated for the three types of plants and separately for pistillate and perfect flowers on mixed plants. The mean outcrossing rate for the population was tm ± SD = 0.885 ± 0.032. Females were more outcrossed than hermaphrodites (0.987 ± 0.112 and 0.790 ± 0.076, respectively), whereas mixed plants were not significantly more or less outcrossed than hermaphrodites (0.840 ± 0.060). Within mixed plants, perfect flowers showed an intermediate outcrossing rate (0.898 ± 0.057), whereas pistillate flowers were as selfed as perfect flowers on hermaphrodite plants (0.782 ± 0.111). Family estimates of outcrossing rates were highly variable. Globally, no biparental inbreeding was detected in this species, and there was a mean of 61.5 ± 19.9% of full‐sibs within families. Floral dimorphism between small pistillate and large perfect flowers together with pollinator preference for larger flowers could explain the observed patterns for both mating parameters. The advantages of gynomonoecy‐gynodioecy are discussed. We conclude that mixed plants do not reduce selfing for all flowers on a plant, but perfect flowers on these plants seem to have an outcrossing advantage.
Evolution of Polaskia chichipe (Cactaceae) under domestication in the Tehuacán Valley, central Mexico: reproductive biology
Authors: Otero‐Arnaiz Adriana , Casas Alejandro , Bartolo Carmen , Pérez‐Negrón Edgar , Valiente‐Banuet Alfonso
Published: February 2008

Polaskia chichipe, a columnar cactus, is cultivated for its edible fruits in central Mexico. This study analyzed whether artificial selection has modified its reproduction patterns and caused barriers to pollen exchange between wild, managed in situ, and cultivated populations. Anthesis was diurnal (∼16 h in winter, ∼10 h in spring) as well as partly nocturnal (∼12 h in winter, ∼3 h in spring), and flowers were pollinated by bees, hummingbirds, and hawk moths. Manual cross‐pollination was ∼37–49% effective in all populations. Self‐pollination was ∼12% successful in the wild, but twice as successful (∼22–27%) in managed and cultivated populations. Diurnal pollination was ∼35–55% effective in winter and 100% in spring. Nocturnal pollination was successful only in winter (15%). Crosses among individuals were more effective within populations than among populations, including populations under a similar management regimen. The least successful crosses were between wild and cultivated populations. Flowers were produced in all populations from January to March, but flowering peaks differed by 1 mo among wild, managed, and cultivated populations and by 2 mo between wild and cultivated populations. The latter interrupted pollen exchange in May. Seeds from managed and cultivated populations germinated faster than those from wild individuals. Domestication has seemingly favored self‐compatible P. chichipe plants with higher fruit yield, a longer period of fruit production, and faster seed germination, attributes that have resulted in partial reproductive barriers between wild and manipulated populations.
Characterization and localization of short‐specific polygalacturonase in distylous Turnera subulata (Turneraceae)
Authors: Athanasiou A. , Khosravi D. , Tamari F. , Shore J. S.
Published: February 2008

We describe for distylous Turnera subulata a polygalacturonase specific to short‐styled plants that is localized to the style transmitting tissue (the tissue through which pollen tubes grow). The polygalacturonase gene is linked to and may be upregulated by the S allele of the distyly locus. Because of its tissue‐specific location, the polygalacturonase may be involved in the self‐incompatibility response, acting in a complementary or antagonistic manner, or possibly in signalling downstream events. A pollen‐specific polygalacturonase was also identified and may be a member of a small multigene family of pollen polygalacturonases. The role, if any, played by the pollen polygalacturonase in distyly, is presently unknown.
The Effect of NaCl on growth, N2 fixation (acetylene reduction), and percentage total nitrogen in Leucaena leucocephala (Leguminosae) var. K‐8
Authors: Anthraper Annie , DuBois John D.
Published: February 2008

Leucaena leucocephala var. K‐8 is a fast‐growing, tropical leguminous tree that has multiple economic uses. This study was conducted to evaluate the effect(s) of varying NaCl concentrations on growth, N2 fixation, and percentage of total tissue nitrogen in different organs in L. leucocephala. Seeds were germinated and grown for 10 wk with a nitrogen‐free fertilizer applied every 2 wk. At 10 wk, plants were treated for either 0, 7, 14, 21, or 28 wk with either deionized water (control), 0.00625 mol/L, 0.0125 mol/L, 0.025 mol/L, 0.05 mol/L, or 0.1 mol/L NaCl in addition to the fertilizer every 2 wk. Growth was measured as plant height, nodule number and mass, and dry tissue mass. N2 fixation was measured by the acetylene reduction assay. Percentage of tissue nitrogen was determined using Kjeldahl analysis. In younger plants (7‐wk treatment), major fluctuations in NaCl tolerance were observed in the different plant organs. As plants matured (14‐ and 21‐wk treatment) NaCl concentrations of 0.025 mol/L and higher caused the greatest reduction in growth and tissue nitrogen. We conclude that NaCl concentrations of 0.025 mol/L and greater caused a major decrease in growth, N2 fixation, and percentage of tissue nitrogen in L. leucocephala plants that were less than 1 yr old.
Post‐dispersal seed fates of four prairie species
Authors: Clark Deborah L. , Wilson Mark V.
Published: February 2008

After dispersal, seeds can germinate and establish as seedlings, persist as seeds, or die. Knowledge of these three seed fates is crucial for understanding the abundance and distribution of plant populations and ultimately, community composition and diversity. Few studies, however, have simultaneously measured these fates, while also examining the factors causing mortality. The goal of this research was to simultaneously quantify the three seed fates and factors causing death (predation and fungal disease) for four species found in prairies in western Oregon, USA. The most common seed fate for the four study species was death (44–80%). Fungal disease, which has seldom been quantified in natural ecosystems, generally caused less than 10% mortality for each of the four species. Vertebrate predation substantially reduced seed numbers only for Bromus carinatus (21%). Of the unmeasured mortality factors, indirect evidence showed invertebrate predation was a cause of death for seeds of only one species, Prunella vulgaris. In addition, competitive pressures caused seedling death for only the two grass species, Bromus carinatus and Cynosurus echinatus. Survival as established seedlings was generally much more common than survival as persistent seed, with the exception of Daucus carota, in which 14% of the sown seeds persisted the first year.
A Middle‐Late Eocene inflorescence of Caryophyllaceae from Tasmania, Australia
Authors: Jordan Gregory J. , Macphail Michael K.
Published: February 2008

A new genus and species (Caryophylloflora paleogenica genus and species nova G. J. Jord. & Macphail) are proposed for a fossil inflorescence found in Middle‐Late Eocene sediments at Locharbour, northeastern Tasmania, Australia. A parsimony analysis of 75 extant species of the order Caryophyllales and five outgroups placed the fossil within Caryophyllaceae, either subfamily Alsinoideae or Caryophylloideae. The analysis used molecular (rbcL and/or matK), morphological, and anatomical data for the extant species and morphological data for the fossil. Tests on extant species imply that the placement of the fossil should be convincing. The fossil appears to be of a lineage distinct from any extant Australian Caryophyllaceae. In situ pollen are consistent with the form species, Periporopollenites polyoratus. This relatively simple pollen type first appears in Australia and New Zealand in the Late Cretaceous, the oldest known record of the Caryophyllaceae. The last appearance of P. polyoratus in Australia is in the Oligocene, and extant Australian members of the Caryophyllaceae are best interpreted as having evolved from species that dispersed from elsewhere during the Neogene or Quaternary.
Characterization of the asymmetric growth of gravistimulated snapdragon spikes by stem and cell dimension analyses
Authors: Friedman Haya , Meir Shimon , Halevy Abraham H. , Philosoph‐Hadas Sonia
Published: February 2008

Growth patterns of detached spikes of gravistimulated snapdragon (Antirrhinum majus L.) were analyzed in detail. The length increment of 5‐mm marked subsections in the upper and lower flanks of the stem‐bending zone was measured during gravistimulation using time‐lapse photographs. At the onset of bending, a negative relative growth rate of the upper flank was detected, followed by increased relative growth rate in both lower and upper flanks. Consequently, a differential stem growth pattern was obtained during gravistimulation, which was significantly and specifically abolished by calcium antagonists reported previously to inhibit stem curvature of snapdragon. The differential growth patterns resulted from dynamic modifications of the cell dimensions in the epidermal and cortical stem layers. Bending started with both shrinking and widening of the epidermal cells and a parallel decrease in length and height of cortical cells at the upper stem flank. These changes were accompanied with a concomitant increase in length and height of the cortical cells on the lower stem flank, followed by a growth increase of epidermal cells. Our results suggest that both the epidermal and cortical cells play an important role in gravitropic shoot bending of snapdragon.
Susceptibility of clover species to fungal infection: the interaction of leaf surface traits and environment
Authors: Bradley Devon J. , Gilbert Gregory S. , Parker Ingrid M.
Published: February 2008

Many foliar pathogens require free water to germinate; therefore, disease pressure should favor plants that are able to repel water. For a suite of 18 sympatric clover species (Trifolium and Medicago, Fabaceae), we evaluated leaf traits affecting leaf wetness and susceptibility to infection by the fungal pathogen Stemphylium sp., causal agent of Stemphylium leaf spot. Spore germination increased with time in free water, and the relative susceptibility of host plants to infection was proportional to the duration of water retention on leaves. Larger leaves captured more water and retained it longer. Unexpectedly, trichomes and leaf wettability did not affect water capture. For clovers planted within natural clover populations at two sites, infection was threefold greater at the wetter site. At the drier site, water retention on the leaf surface was an important predictor of infection rates across host species, but persistent fog and dew at the wetter site reduced the importance of rapid leaf drying. Our results suggest that plant adaptations that reduce water retention on leaves may also reduce disease incidence, but the selective advantage of these traits will vary among habitats.
Reproductive assurance varies with flower size in Collinsia parviflora (Scrophulariaceae)
Authors: Elle Elizabeth , Carney Robert
Published: February 2008

A central question in plant evolutionary ecology is how mixed mating systems are maintained in the face of selection against self‐pollination. Recently, attention has focused on the potential reproductive assurance (RA) benefit of selfing: the ability to produce seeds via autonomous selfing when the potential for outcrossing is reduced or absent. To date, there is little experimental support for this benefit under natural pollination conditions. In addition, the RA hypothesis has not been tested experimentally in a species displaying morphological variation for traits expected to influence the mating system, such as flower size, which affects both attractiveness to pollinators and ability to self autonomously. Here, we document significant among‐population variation in flower size in Collinsia parviflora and show that pollinators preferred large flowers over small flowers in experimental arrays. The pollinator community varied among three study sites, and two small‐flowered populations had lower pollinator visitation rates than one large‐flowered population. We compared seed production between intact flowers (can self) and experimentally emasculated flowers (require a pollinator) on large‐ and small‐flowered plants. As predicted by the RA hypothesis, small‐flowered plants show a greater RA benefit of selfing than large‐flowered plants; emasculated, small flowers produced very few seeds, relative to intact, small flowers or either emasculated or intact, large flowers. We also show that the RA benefit is pollination‐context dependent, differing between small‐ and large‐flowered test sites, likely due to a combination of pollinator discrimination against small flowers and differences between test sites in the pollinator community. This paper is the first experimental evidence showing a trait‐dependent RA benefit of selfing under natural pollination conditions.
Males outcompete hermaphrodites for seed siring success in controlled crosses in the polygamous Fraxinus excelsior (Oleaceae)
Authors: Morand‐Prieur Marie‐Elise , Raquin Christian , Shykoff Jacqui A. , Frascaria‐Lacoste Nathalie
Published: February 2008

Polygamy (including trioecy and subdioecy), the co‐occurrence of males, hermaphrodites, and females in natural populations, is a rare and poorly studied breeding system expressed in Fraxinus excelsior L. (Oleaceae), a wind‐pollinated tree. Here we investigate siring ability of pollen from male vs. hermaphrodite individuals to better understand this sex polymorphism. We conducted single‐donor and two‐donor pollination experiments and compared both fruit set and seed siring success, assessed with polymorphic microsatellite markers, of male and hermaphrodite individuals. Single pollen donor crosses allowed us to verify the male function of hermaphrodites. However, pollen from hermaphrodites was much less proficient than male pollen, with males siring 10 times as many fruits in single donor pollination treatments. This result was strengthened by the surprisingly low reproductive success of hermaphrodites in pollen competition conditions: of the 110 seedlings analyzed three were selfed and only one was sired by the hermaphrodite donor. The remaining 106 were sired by the male pollen donor. These results raise the question of the maintenance of male fertility in hermaphrodites in Fraxinus excelsior. Male function of hermaphrodites in this species now needs to be assessed under field conditions.
Fitness ofCuscuta salina(Convolvulaceae) parasitizingBeta vulgaris(Chenopodiaceae) grown under different salinity regimes
Authors: Frost Abigail , López‐Gutiérrez Juan Carlos , Purrington Colin B.
Published: February 2008

The distribution of saltmarsh dodder (Cuscuta salina) worldwide is restricted to areas of high salinity, where it parasitizes a variety of salt‐tolerant plants. Because dodders do not maintain root connections to the soil, this pattern of parasitization may be related to the effects of salt stress on the host that increase the ability of attached dodders to more easily transfer host contents. This study explored whether a saline host environment is required for successful infection and whether stem contents of potential hosts become more concentrated in response to salinity. Fecundity of dodder was highest when hosts (Beta vulgaris) were grown either without salt or at high (250 mmol/L) salinity; it produced significantly fewer flowers and fruit at intermediate salinities. Stem constituents of two unparasitized host species had high conductivity and elevated levels of dissolved sugars at increasing salinities. Nitrate content of stems was also increased by salinity, but declined at the extreme salinity (400 mmol/L). Salinity effects on host suitability may partially explain differences in growth and vigor ofC. salinain certain areas of salt marsh, but information on nonrandom dispersal ofC. salinaseeds may be needed to fully explain this parasite's distribution.
Drought constraints on leaf gas exchange by Miconia ciliata (Melastomataceae) in the understory of an eastern Amazonian regrowth forest stand
Authors: Fortini Lucas B. , Mulkey Stephen S. , Zarin Daniel J. , Vasconcelos Steel S. , de Carvalho Claudio J. R.
Published: February 2008

Analyses of the effects of drought stress on Amazonian regrowth stands are lacking. We measured leaf gas exchange and leaf water potential of Miconia ciliata (Melastomataceae) in a dry‐season irrigation experiment in 14‐yr‐old regrowth. In the dry season, irrigated plants maintained significantly higher leaf water potentials, photosynthetic capacity at light saturation (Amax), stomatal conductance (gs), internal CO2 concentration (Ci), and lower Amax/gs than control plants. The degree of dry‐season down‐regulation of control plant Amax, along with its fast recovery following rain, reveals the importance of occasional dry‐season rains to the carbon budget of M. ciliata. During the wet season, we observed higher Amax for control plants than for plants that had been irrigated during the dry season. We hypothesize that reduced drought constraints on photosynthesis of irrigated plants advanced the flowering and fruiting phenology of irrigated plants into the dry season. Flowers and fruits of control plants developed later, during the wet season, potentially stimulating a compensatory reproductive photosynthesis response in nearby leaves. The relative drought intolerance of M. ciliata may be a deciding factor in its ability to survive through the dynamic successional development of the regrowth stand studied.
Phylogeographic relationships within Packera sanguisorboides (Asteraceae), a narrow endemic species that straddles a major biogeographic boundary
Authors: Bain John F. , Golden Joanne L.
Published: February 2008

Packera sanguisorboides is endemic to the Sangre de Cristo and Sacramento Mountains of New Mexico, USA. As such, its distribution spans the boundary between two major floristic regions: the southern Rocky Mountain region and the Madrean region. Chloroplast DNA haplotype polymorphism patterns in populations from both regions show that most of the molecular variance exists among populations rather than between mountain ranges and that hybridization with at least one other Packera species containing distinct cpDNA haplotypes has contributed to the cpDNA diversity within P. sanguisorboides. Based on morphological and cpDNA data, the closest relatives to P. sanguisorboides are thought to be mesic species similar to P. glabella and P. sanguisorbae.
Comparative anatomy and morphology of Vitis vinifera (Vitaceae) somatic embryos from solid‐ and liquid‐culture‐derived proembryogenic masses
Authors: Jayasankar S. , Bondada Bhaskar R. , Li Zhijian , Gray D. J.
Published: February 2008

Ontogeny of somatic embryos of grapevine (Vitis vinifera) produced from solid‐ and liquid‐culture‐derived proembryogenic masses (PEM) was compared using light and scanning electron microscopy. Somatic embryos produced from solid‐medium‐derived PEM (SPEM) had large cotyledons, little or no visible suspensor structure, and a relatively undeveloped concave shoot apical meristem, whereas those from liquid‐medium‐derived PEM (LPEM) had smaller cotyledons, a distinct suspensor, and a flat‐to‐convex shoot apical meristem. The convex shoot apical meristem in LPEM‐derived somatic embryos formed as early as the heart stage of development; it was 4–6 cell layers deep and rich in protein. Suspensors persisted in fully developed and mature LPEM‐derived somatic embryos. The SPEM‐derived somatic embryos exhibited dormancy, as do mature zygotic embryos, which also have a rudimentary suspensor, whereas LPEM‐derived embryos were not dormant. We hypothesize that the presence of a persistent suspensor in LPEM‐derived somatic embryos modulates development, ultimately resulting in rapid germination and a high plant‐regeneration rate.
Rapid evolution of parental rDNA in a synthetic tobacco allotetraploid line
Authors: Skalická Kamila , Lim K. Yoong , Matyášek Roman , Koukalová Blažena , Leitch Andrew R. , Kovařík Ales
Published: February 2008

Unidirectional gene conversion of rDNA units has occurred in the evolution of natural tobacco (Nicotiana tabacum). In this paper we report the use of the synthetic tobacco line Th37, 4n (N. sylvestris × N. tomentosiformis), to study early rDNA evolution associated with allopolyploidy. At least three classes of newly amplified rDNA unit variants were identified (17/20 plants). Their presence was often accompanied by near‐complete elimination of N. tomentosiformis‐donated rDNA units (15/20 plants). Novel rDNA units were of N. tomentosiformis‐type and contained rearranged subrepeats in the intergenic spacer. The maternal N. sylvestris‐derived units were unchanged, except for some alteration in the ratio of individual gene family members. A cytogenetic analysis revealed rDNA sites on N. sylvestris‐derived chromosomes S10, S11, and S12 and N. tomentosiformis‐derived chromosomes T3 and in some cases T4. An rDNA locus does not occur on N. tomentosiformis chromosome 4. The locus on chromosome T4 of some hybrids correlates with the occurrence of the novel units that probably amplified at the locus. Combined with an analysis of tobacco cultivars, the data indicate that an initial burst of rDNA evolution associated with allopolyploidy was followed by a slower process that led towards reduced complexity and a decreased number of rDNA variants.
Geometrical relationships specifying the phyllotactic pattern of aquatic plants
Authors: Kelly Wanda J. , Cooke Todd J.
Published: February 2008

The complete range of various phyllotaxes exemplified in aquatic plants provide an opportunity to characterize the fundamental geometrical relationships operating in leaf patterning. A new polar‐coordinate model was used to characterize the correlation between the shapes of shoot meristems and the arrangements of young leaf primordia arising on those meristems. In aquatic plants, the primary geometrical relationship specifying spiral vs. whorled phyllotaxis is primordial position: primordia arising on the apical dome (as defined by displacement angles θ ≤ 90° during maximal phase) are often positioned in spiral patterns, whereas primordia arising on the subtending axis (as defined by displacement angles of θ ≥ 90° during maximal phase) are arranged in whorled patterns. A secondary geometrical relationship derived from the literature shows an inverse correlation between the primordial size : available space ratio and the magnitude of the Fibonacci numbers in spiral phyllotaxis or the number of leaves per whorl in whorled phyllotaxis. The data available for terrestrial plants suggest that their phyllotactic patterning may also be specified by these same geometrical relationships. Major exceptions to these correlations are attributable to persistent embryonic patterning, leaflike structures arising from stipules, congenital splitting of young primordia, and/or non‐uniform elongating of internodes. The geometrical analysis described in this paper provides the morphological context for interpreting the phenotypes of phyllotaxis mutants and for constructing realistic models of the underlying mechanisms responsible for generating phyllotactic patterns.
Consequences of differences in flowering date on seed production in Heloniopsis orientalis (Liliaceae)
Authors: Morinaga Shin‐Ichi , Tsuji Kazuki , Sakai Satoki
Published: February 2008

We examined the consequences of differences in flowering date on seed production in the self‐compatible herb Heloniopsis orientalis. The number of selfed seeds per fruit, as determined by microsatellite markers, did not depend on when the plant flowered, whereas the number of outcrossed seeds per fruit increased with later flowering dates. Consequently, the selfing rate decreased with later flowering dates. The number of seeds (including both selfed and outcrossed ones) per fruit and the seed : ovule ratio increased with later flowering dates. We also examined the effects of pollinators and plant size on seed production. The visitation rate of Diptera did not depend on the flowering season, whereas that of Hymenoptera markedly increased as the flowering season progressed. Diptera stayed longer than Hymenoptera on each plant and flower. Seed production per fruit did not depend on plant size. Thus, the change in selfing rate associated with later flowering dates resulted from the seasonal change in pollinators rather than plant size.
Effects of herbivory and its timing across populations of Trillium grandiflorum (Liliaceae)
Authors: Knight Tiffany M.
Published: February 2008

The goal of this study was to identify the degree to which the frequency and timing of herbivory by white‐tailed deer (Odocoileus virginianus) and subsequent plant response varied across 12 populations of the perennial herb Trillium grandiflorum. Effects of natural and experimental herbivory on the stage and size of reproductive plants were measured. Both the frequency and timing of herbivory varied across T. grandiflorum populations. Reproductive plants were more likely to regress to nonreproductive stages in the next growing season when (1) reproductive plants were consumed by deer (vs. intact reproductive plants); (2) reproductive plants were consumed early in the growing season (vs. reproductive plants consumed late in the growing season); (3) reproductive plants were smaller in size. Clipped plants that remained reproductive were smaller in the following season than unclipped controls. Plant size was positively correlated with the number of ovules, suggesting that reductions in the growth rate of reproductive plants diminish their future reproductive success. Populations with high levels of natural herbivory had a greater proportion of reproductive plants that regressed to nonreproductive stages, probably because reproductive plants in these populations were smaller in size. However, the plant response to herbivory was similar across populations.
Genetic and historical relationships among geothermally adapted Agrostis (bentgrass) of North America and Kamchatka: evidence for a previously unrecognized, thermally adapted taxon
Authors: Tercek Michael T. , Hauber Donald P. , Darwin Steven P.
Published: February 2008

Agrostis species have been known to evolve ecotypes rapidly in response to unusual edaphic conditions. The geographic distribution of Agrostis taxa in Lassen Volcanic National Park (California) and Yellowstone National Park (Wyoming) in the United States and the Valley of the Geysers (Kamchatka Peninsula) in Russia suggests that Agrostis scabra might have independently evolved morphologically similar ecotypes several times. We used RAPDs to show that, contrary to expectation, the thermal populations are not independently evolved, but instead constitute a single taxon that currently has four names. A UPGMA including the four thermal and nine nonthermal Agrostis taxa showed that the thermal cluster divides into geographically distinct subclusters, but that two morphologically distinct thermal taxa do not cluster independently. Even though currently confused with the thermal populations, nonthermal A. scabra is not closely related. An analysis of molecular variance (AMOVA) showed significant differentiation between the thermal populations and the nonthermal species sampled in this study. Splitting a hypothesized thermal operational taxonomic unit (OTU) into its components (geographically separated populations) does not greatly affect the partitioning of variation among OTUs. All thermal populations therefore should be assigned to the same taxon, but its taxonomic rank cannot be determined at this time.
An extinct genus of Salicaceae based on twigs with attached flowers, fruits, and foliage from the Eocene Green River Formation of Utah and Colorado, USA
Authors: Boucher Lisa D. , Manchester Steven R. , Judd Walter S.
Published: February 2008

A newly recovered twig with attached leaves and flowers from the Eocene Green River Formation of Utah provides the basis for recognizing a new, extinct genus of Salicaceae sensu lato (s.l.). Pseudosalix handleyi gen. et sp. nov. has alternate lanceolate leaves with pinnate, semicraspedodromous venation and a serrate margin with glandular teeth. The inflorescence is terminal on the twig and is unisexual, composed of flowers organized in a paniculoid cyme, with lateral paraclades of pedicellate flowers. The attached pistillate flowers have four prominent sepals that are valvate in bud, spreading but basally fused at anthesis; the single pistil of each flower is ovoid with three or four longitudinal sutures, indicating development to a capsular fruit. Three or four recurved styles radiate from the apex of the pistil, each with a distal globose stigma. The infructescence, verified by attachment to twigs with the same kind of leaves, bore capsular fruits of three and four valves. Associated but unattached, staminate flowers also have four well‐developed, basally connate sepals. They are pedicellate and bear several stamens, each with a short filament and globose anther. The available morphological characters place the fossil species within the Salicaceae s.l. as an immediate sister to the clade containing Populus and Salix. Although the likely outgroup genera (including Itoa, Poliothyrsis, Carrierea, and Idesia) to tribe Saliceae all occur in Asia today and not North America, the occurrence of both Pseudosalix and Populus in the Eocene of Utah raises the possibility of a North American origin for the Saliceae.
Transgenic overproduction of glutathione reductase does not protect cotton, Gossypium hirsutum (Malvaceae), from photoinhibition during growth under chilling conditions
Authors: Logan Barry A. , Monteiro Gary , Kornyeyev Dmytro , Payton Paxton , Allen Randy D. , Holaday A. Scott
Published: February 2008

In some studies, tissues from plants that have been genetically transformed to overproduce antioxidant enzymes sustain less damage when abruptly exposed to short‐term chilling in the laboratory. However, few studies have examined the performance of transgenic plants during longer‐term growth under chilling conditions. We compared growth of transgenic cotton that overproduces glutathione reductase (GR+; ∼40‐fold overproduction) to growth of the wild type in a controlled environment chamber as leaf temperature was lowered from 28° to 14°C over 9 d and for a subsequent 9‐d period at 14°C. In wild‐type and GR+ cotton, chilling temperatures resulted in decreased dark‐adapted Fv/Fm (the ratio of variable to maximal fluorescence; a measure of maximum photosystem II quantum yield) and mid‐light period photosystem II quantum yield, coupled with increased 1 − qP (a nonlinear estimate of the reduction state of the primary quinone acceptor of photosystem II). The capacity for photosynthetic oxygen evolution decreased during the first portion of the chilling exposure, but recovered slightly during the second half. At no point during the chilling exposure did the performance of GR+ plants differ significantly from that of wild‐type plants in any of the above parameters. The absence of an effect of GR overproduction under longer‐term chilling may be explained, in part, by the fact that wild‐type cotton acclimated to chilling by upregulating native GR activity.
The phylogeny of Gaura (Onagraceae) based on ITS, ETS, andtrnL‐F sequence data
Authors: Hoggard Gloria D. , Kores Paul J. , Molvray Mia , Hoggard Ronald K.
Published: February 2008

Gaura (Onagraceae: Onagreae) is a small North American genus of 21 species consisting mostly of night‐blooming, moth‐pollinated annuals and perennials. The current infrageneric classification based on differences in habit, floral symmetry, and fruit morphology recognizes eight sections within the genus. We examine the phylogenetic relationships of all 21 species of Gaura using DNA sequence data from the internal transcribed spacer region (ITS), the external transcribed spacer region (ETS), and the plastid trnL‐F region. Combined analysis of these regions indicate Gaura is monophyletic only if it includes Stenosiphon, a monotypic genus comprised of S. linifolius. Within Gaura, our studies indicate that sections Gauridium, Schizocarya, Campogaura, Stipogaura, Xenogaura, and Gaura are monophyletic, but sections Xerogaura and Pterogaura are not and should be reevaluated. In addition, molecular data provide support for the hypothesis that G. sinuata and G. drummondii arose via interspecific hybridization followed by genome doubling; their influence on phylogenetic reconstruction is discussed.
Mating system and population structure of Acacia aroma and A. macracantha (Fabaceae)
Authors: Casiva Paola Vanesa , Vilardi Juan César , Cialdella Ana María , Saidman Beatriz O.
Published: February 2008

Acacia aroma and A. macracantha are closely related species that inhabit northern and central Argentina. The reproductive barriers between them seem to be weak. They exhibit low genetic differentiation, high levels of interspecific gene flow, and extensive areas of sympatry. Isoenzymatic approaches were used to evaluate the population structure and mating system parameters in natural Argentine populations of A. aroma and A. macracantha and to provide new tools for the analysis of relationships between these two species. All studied populations had high levels of genetic variability and no significant departures from Hardy‐Weinberg expectations, but the two species did not differ from each other. Most variability occured within populations. Mating system analysis showed high levels of outcrossing, no biparental inbreeding, and a high probability that individuals within progeny arrays are full rather than half sibs. In all A. aroma and A. macracantha populations, polymorphic loci had the same allelic variants, and no geographic or genetic isolation between species was found. The results favor the hypothesis that these two entities represent a single polymorphic species rather than two distinct species.
Genetic structure of hybrid zones betweenPinus pumilaandP. parvifloravar.pentaphylla(Pinaceae) revealed by molecular hybrid index analysis
Authors: Watano Yasuyuki , Kanai Akiko , Tani Naoki
Published: February 2008

Pinusspecies have three differently inherited genomes: paternal chloroplast, maternal mitochondrial, and biparental nuclear. Our previous study on the hybrid zones between alpinePinus pumilaand montane to subalpineP. parvifloravar.pentaphyllademonstrated contrasting patterns of introgression of two cytoplasmic genomes, i.e., the paternal cpDNA flowed fromP. parvifloravar.pentaphyllatoP. pumila, and the maternal mtDNA flowed in the reverse direction. In the present study, we developed codominant nuclear DNA markers diagnostic or mostly diagnostic for each parental species by single‐strand conformation polymorphism (SSCP) of polymerase chain reaction (PCR) products, using expressed sequence tag (EST) primers ofPinus taeda. To describe the introgressive patterns of the nuclear genes, the molecular hybrid index (MHI) showing the overall proportion of alleles inferred to be derived fromP. pumilawas determined for each plant collected in hybrid zones on Mt. Asahidake and Mt. Higashiazuma, Japan. At Mt. Asahidake, the MHI values changed clinally according to the altitudes at which the plants were collected. However, at Mt. Higashiazuma, there was a gap in the MHI values between the plants above and below theAbiesandTsugaforest zone (alt. 1800–1900 m). This suggested that the zone plays a role in creating an effective barrier to gene flow in the hybrid zone.
Dinoflagellates: a remarkable evolutionary experiment
Authors: Hackett Jeremiah D. , Anderson Donald M. , Erdner Deana L. , Bhattacharya Debashish
Published: February 2008

In this paper, we focus on dinoflagellate ecology, toxin production, fossil record, and a molecular phylogenetic analysis of hosts and plastids. Of ecological interest are the swimming and feeding behavior, bioluminescence, and symbioses of dinoflagellates with corals. The many varieties of dinoflagellate toxins, their biological effects, and current knowledge of their origin are discussed. Knowledge of dinoflagellate evolution is aided by a rich fossil record that can be used to document their emergence and diversification. However, recent biogeochemical studies indicate that dinoflagellates may be much older than previously believed. A remarkable feature of dinoflagellates is their unique genome structure and gene regulation. The nuclear genomes of these algae are of enormous size, lack nucleosomes, and have permanently condensed chromosomes. This chapter reviews the current knowledge of gene regulation and transcription in dinoflagellates with regard to the unique aspects of the nuclear genome. Previous work shows the plastid genome of typical dinoflagellates to have been reduced to single‐gene minicircles that encode only a small number of proteins. Recent studies have demonstrated that the majority of the plastid genome has been transferred to the nucleus, which makes the dinoflagellates the only eukaryotes to encode the majority of typical plastid genes in the nucleus. The evolution of the dinoflagellate plastid and the implications of these results for understanding organellar genome evolution are discussed.
Phylogeny and evolution of ferns (monilophytes) with a focus on the early leptosporangiate divergences
Authors: Pryer Kathleen M. , Schuettpelz Eric , Wolf Paul G. , Schneider Harald , Smith Alan R. , Cranfill Raymond
Published: February 2008

The phylogenetic structure of ferns (= monilophytes) is explored here, with a special focus on the early divergences among leptosporangiate lineages. Despite considerable progress in our understanding of fern relationships, a rigorous and comprehensive analysis of the early leptosporangiate divergences was lacking. Therefore, a data set was designed here to include critical taxa that were not included in earlier studies. More than 5000 bp from the plastid (rbcL, atpB, rps4) and the nuclear (18S rDNA) genomes were sequenced for 62 taxa. Phylogenetic analyses of these data (1) confirm that Osmundaceae are sister to the rest of the leptosporangiates, (2) resolve a diverse set of ferns formerly thought to be a subsequent grade as possibly monophyletic (((Dipteridaceae, Matoniaceae), Gleicheniaceae), Hymenophyllaceae), and (3) place schizaeoid ferns as sister to a large clade of “core leptosporangiates” that includes heterosporous ferns, tree ferns, and polypods. Divergence time estimates for ferns are reported from penalized likelihood analyses of our molecular data, with constraints from a reassessment of the fossil record.
The origin and diversification of angiosperms
Authors: Soltis Pamela S. , Soltis Douglas E.
Published: February 2008

The angiosperms, one of five groups of extant seed plants, are the largest group of land plants. Despite their relatively recent origin, this clade is extremely diverse morphologically and ecologically. However, angiosperms are clearly united by several synapomorphies. During the past 10 years, higher‐level relationships of the angiosperms have been resolved. For example, most analyses are consistent in identifyingAmborella, Nymphaeaceae, and Austrobaileyales as the basalmost branches of the angiosperm tree. Other basal lineages include Chloranthaceae, magnoliids, and monocots. Approximately three quarters of all angiosperm species belong to the eudicot clade, which is strongly supported by molecular data but united morphologically by a single synapomorphy—triaperturate pollen. Major clades of eudicots include Ranunculales, which are sister to all other eudicots, and a clade of core eudicots, the largest members of which are Saxifragales, Caryophyllales, rosids, and asterids. Despite rapid progress in resolving angiosperm relationships, several significant problems remain: (1) relationships among the monocots, Chloranthaceae, magnoliids, and eudicots, (2) branching order among basal eudicots, (3) relationships among the major clades of core eudicots, (4) relationships within rosids, (5) relationships of the many lineages of parasitic plants, and (6) integration of fossils with extant taxa into a comprehensive tree of angiosperm phylogeny.
Monocot relationships: an overview
Authors: Chase Mark W.
Published: February 2008

In 10 years, the monocots have gone from being one of the least studied and most phylogenetically misunderstood groups of the angiosperms to one of the best characterized. Based on analyses of seven genes representing all three genomes, the following clades have high bootstrap support: Acorales (with the single genus Acorus) is sister to the rest of the monocots, followed successively by Alismatales (including Araceae and Tofieldiaceae), Petrosaviales, Dioscoreales/Pandanales, Liliales, Asparagales, and finally a polytomy of Arecales, Commelinales/Zingiberales, Dasypogonaceae, and Poales. Many of these results also have support from at least some morphological data, but some are unique to the trees created from DNA sequence data. Monocots have been shown in molecular clock studies to be at least 140 million years old, and all major clades and most families date to well before the end of the Cretaceous. More data are required to clarify the positions of the remaining unclearly placed orders, Asparagles, Liliales, and Arecales, as well as Dasypogonaceae. More sequences from the nuclear and mitochondrial genomes are also needed to complement those from the plastid genome, which is the most sampled and thus far most pattern‐rich.
Reconstructing patterns of reticulate evolution in plants
Authors: Linder C. Randal , Rieseberg Loren H.
Published: February 2008

Until recently, rigorously reconstructing the many hybrid speciation events in plants has not been practical because of the limited number of molecular markers available for plant phylogenetic reconstruction and the lack of good, biologically based methods for inferring reticulation (network) events. This situation should change rapidly with the development of multiple nuclear markers for phylogenetic reconstruction and new methods for reconstructing reticulate evolution. These developments will necessitate a much greater incorporation of population genetics into phylogenetic reconstruction than has been common. Population genetic events such as gene duplication coupled with lineage sorting and meiotic and sexual recombination have always had the potential to affect phylogenetic inference. For tree reconstruction, these problems are usually minimized by using uniparental markers and nuclear markers that undergo rapid concerted evolution. Because reconstruction of reticulate speciation events will require nuclear markers that lack these characteristics, effects of population genetics on phylogenetic inference will need to be addressed directly. Current models and methods that allow hybrid speciation to be detected and reconstructed are discussed, with a focus on how lineage sorting and meiotic and sexual recombination affect network reconstruction. Approaches that would allow inference of phylogenetic networks in their presence are suggested.
Effects of pollen quantity and quality on reproduction and offspring vigor in the rare plant Scorzonera humilis (Asteraceae)
Authors: Colling Guy , Reckinger Claude , Matthies Diethart
Published: February 2008

We studied the effects of pollinator exclusion, interparental distance, and supplementary hand pollination on reproduction and progeny vigor in Scorzonera humilis (Asteraceae), a rare plant of fragmented, nutrient‐poor grasslands. Caged flowers produced no seeds and selfed flowers only very rarely, indicating that S. humilis is mainly self‐incompatible. Seed production, seed mass, and seed germination following between‐population crosses were consistently, but not significantly, higher than after within‐population crosses. Seed set increased with local density of conspecifics, indicating that the reduced plant density in fragmented populations may reduce plant reproductive success. Seed set was pollen limited in all four populations studied. Supplementary hand‐pollination strongly increased the survival of offspring, indicating that either pollinators transferred pollen from related individuals resulting in inbreeding depression in spite of the incompatibility system or that higher pollen loads increased pollen competition and the selectivity among gametes. In one of the populations, adding pollen from a different population strongly increased progeny fitness compared with both natural pollination and pollen supplementation from the same population. The results indicate that S. humilis is sensitive to inbreeding and that pollen limitation can reduce both the number and quality of offspring.
The origins of an important cactus crop, Opuntia ficus‐indica (Cactaceae): new molecular evidence
Authors: Griffith M. Patrick
Published: February 2008

Opuntia ficus‐indica is a long‐domesticated cactus crop that is important in agricultural economies throughout arid and semiarid parts of the world. The biogeographic and evolutionary origins of this species have been obscured through ancient and widespread cultivation and naturalization. The origin of O. ficus‐indica is investigated through the use of Bayesian phylogenetic analyses of nrITS DNA sequences. These analyses support the following hypotheses: that O. ficus‐indica is a close relative of a group of arborescent, fleshy‐fruited prickly pears from central and southern Mexico; that the center of domestication for this species is in central Mexico; and that the taxonomic concept of O. ficus‐indica may include clones derived from multiple lineages and therefore be polyphyletic.
American Journal of Botany at 90: a librarian perspective
Authors: Pellack Lorraine J.
Published: February 2008

The American Journal of Botany (AJB) is available on the shelves of most college and university libraries in the U.S., as well as in many faculty offices, and in research libraries affiliated with botanical gardens. This article presents information on how librarians view AJB, the role that scientific associations play in the perceived quality of the journals they publish, the unique nature of botany literature (compared to other sciences), AJB as a core journal, and a general discussion of the factors that influence librarians decisions when deciding to cancel a subscription or keep a journal in their collection.