bluuebunny/crossref_metadata_2025 huggingface dataset:
Reading Comprehension and Fluency: Examining the Effects of Tutoring and Video Self-Modeling on First-Grade Students with Reading Difficulties
Authors: Hitchcock Caryl H. , Prater Mary Anne , Dowrick Peter W.
Published: February 2007

The need for research-based instructional support for culturally and linguistically diverse students with reading difficulties is a national priority. In this rural Hawaii study, teachers and parents selected four first-grade students who were experiencing delays in reading fluency and comprehension skills to receive tutoring and video self-modeling interventions. Two students were identified as having specific learning disabilities, one as being developmentally delayed, and one was in the process of being referred for special education. Community partners were trained to provide tutoring with the 25-step ACE reading protocol. Two 2-minute self-modeling videotapes were constructed: the first depicted the student fluently reading a passage; the second showed the student applying a story map and successfully answering comprehension questions. A multiple-baseline design across two behaviors (reading fluency and comprehension) was used to observe the effect of each intervention on reading fluency and comprehension skills. Reading fluency, measured in number of correct words per minute, doubled for three students and quadrupled for the fourth by the end of eight weeks. Reading comprehension, measured in number of correct responses, reached pre-established criteria. Viewing the self-modeling videotapes was associated with reduced variability and maintenance of increased performance. Follow-up indicated that gains maintained for six months. Teachers and parents reported generalization to classroom and home.
A Comparative Study of the Personality Characteristics of Primary-School Students with Learning Disabilities and their Nonlearning Disabled Peers
Authors: Sharma Gitanjali
Published: February 2007

This study examined the personality characteristics of 180 boys and girls of ages 8, 9, and 10 with learning disabilities (LD) in 3rd, 4th, and 5th grade in urban and rural primary schools of Andhrapradesh, India. The subjects were identified based on their scholastic achievement on a spelling dictation test, an oral reading test, a reading comprehension test and an arithmetic test developed specifically for the purpose, along with mental ability tests - Raven's Standard Progressive Matrices and Draw-A-Man. An adapted version of the Children's Personality Questionnaire (CPQ) was administered to the subjects with LD and a comparison group of children without learning disabilities (NLD). Examination of scores obtained by LD and NLD subjects on the CPQ portrays the LD child as having problems in social and emotional adjustment. Further, the older LD children tended to show a more maladaptive behavioral disposition than the younger, and there was a significant gender effect among LD children.
Principals' and Teachers' Perceptions of Learning Disabilities: A Study from NARA Prefecture, Japan
Authors: Kataoka Mika , van Kraayenoord Christina E. , Elkins John
Published: February 2007

In this study, perceptions of learning disabilities were obtained from 128 principals and 123 teachers in the Nara Prefecture, Japan. A factor analysis indicated that five factors underlie perceptions of learning disabilities: changes in the family and social situation, insufficient knowledge of and support for learning disabilities, teachers' abilities and professional development, teachers' situation and governmental issues. Teachers' situation was perceived to be the main factor, whereas the least important factor was governmental issues. Teachers mainly indicated agreement on the factor of insufficient knowledge of and support for students with learning disabilities. Principals were more aware of governmental issues than teachers.
LD Identification: It's Not Simply a Matter of Building a Better Mousetrap
Authors: Mellard Daryl F. , Deshler Donald D. , Barth Amy
Published: February 2007

Historically, researchers, policy makers, and practitioners have sought improved solutions to the issues associated with LD identification decisions. Since the passage of P.L. 94–142, numerous identification methods has been proposed, implemented, and studied. While each new method has been successful, at least partially, in addressing some of the limitations of earlier methods, each new identification model is saddled with its own set of shortcomings. This article argues that factors beyond specific LD identification technology significantly influence the decision-making process and ultimately decisions about who is and who is not LD. Results from focus group discussions with six stakeholder groups (LD parents, LD teachers, general education teachers, directors of special education, school principals, and school psychologists/diagnosticians) are reported, indicating that a broad array of factors beyond a student's performance on formal and informal assessments influence ultimate decisions made about a student's eligibility for learning disability services. Thus, the search for new identification technologies should also include efforts to better understand the values and biases of critical stakeholders and how to include these factors in the overall decision-making process.
Tests of pre‐ and postpollination barriers to hybridization between sympatric species of Ipomopsis (Polemoniaceae)
Authors: Wolf Paul G. , Campbell Diane R. , Waser Nickolas M. , Sipes Sedonia D. , Toler Trent R. , Archibald Jenny K.
Published: February 2007

The Ipomopsis aggregata species complex (Polemoniaceae) includes species pairs that hybridize readily in nature as well as pairs that meet along contact zones with no apparent hybridization. Artificial hybrids can be made between I. aggregata and I. arizonica, yet morphological intermediates between these two species have not been observed in natural populations. This apparent lack of hybridization is perplexing given that plants of the two species often grow within a few metres of each other and both species have red flowers visited by the same species of hummingbirds. We used trained hummingbirds to examine pollen transfer within and between species. We also hand‐pollinated flowers to examine paternal success of heterospecific and conspecific pollen, testing paternity with electrophoretic examination of seeds. Hummingbirds were not simply better at transferring pollen within than between species. Instead, I. arizonica was a better pollen donor so that considerable pollen transfer was observed from I. arizonica to I. aggregata, but very little in the opposite direction. Conversely, once pollen arrived at stigmas, I. arizonica pollen performed very poorly on I. aggregata pistils. However, pollen from I. aggregata could, in some cases, sire seeds on I. arizonica. We hypothesize that hybrids are scarce in nature, in part, because of asymmetric barriers to reproduction: little pollen transfer in one direction and poor pollen performance in the other.
Estimating near‐infrared leaf reflectance from leaf structural characteristics
Authors: Slaton Michèle R. , Raymond Hunt E. , Smith William K.
Published: February 2007

The relationship between near‐infrared reflectance at 800 nm (NIRR) from leaves and characteristics of leaf structure known to affect photosynthesis was investigated in 48 species of alpine angiosperms. This wavelength was selected to discriminate the effects of leaf structure vs. chemical or water content on leaf reflectance. A quantitative model was first constructed correlating NIRR with leaf structural characteristics for six species, and then validated using all 48 species. Among the structural characteristics tested in the reflectance model were leaf trichome density, the presence or absence of both leaf bicoloration and a thick leaf cuticle (>1 μm), leaf thickness, the ratio of palisade mesophyll to spongy mesophyll thickness (PM/SM), the proportion of the mesophyll occupied by intercellular air spaces (%IAS), and the ratio of mesophyll cell surface area exposed to IAS (Ames) per unit leaf surface area (A), or Ames/A. Multiple regression analysis showed that measured NIRR was highly correlated with Ames/A, leaf bicoloration, and the presence of a thick leaf cuticle (r2 = 0.93). In contrast, correlations between NIRR and leaf trichome density, leaf thickness, the PM/SM ratio, or %IAS were relatively weak (r2 < 0.25). A model incorporating Ames/A, leaf bicoloration, and cuticle thickness predicted NIRR accurately for 48 species (r2 = 0.43; P < 0.01) and may be useful for linking remotely sensed data to plant structure and function.
Phylogenetic relationships of Loasaceae subfamily Gronovioideae inferred from matK and ITS sequence data
Authors: Moody Michael L. , Hufford Larry , Soltis Douglas E. , Soltis Pamela S.
Published: February 2007

Members of subfamily Gronovioideae are distinctive among Loasaceae in their androecial and gynoecial simplicity. The four genera of the subfamily differ, however, in chromosome number, floral novelties, and pollen exine sculpturing, which led to suggestions that the Gronovioideae were polyphyletic. Phylogenetic analyses based on sequences of the chloroplast gene matK and the internal transcribed spacer region (ITS) of nuclear rDNA have been conducted using parsimony and maximum likelihood methods to assess the monophyly of Gronovioideae and to determine the sister group relationships of gronovioid genera. The results show Gronovioideae are monophyletic and placed as the sister to Mentzelia. Within Gronovioideae, Petalonyx is sister to a clade consisting of Cevallia, Gronovia, and Fuertesia. Among the remaining Loasaceae, subfamily Mentzelioideae, as originally circumscribed, is paraphyletic. Subfamily Loasoideae is placed as the sister to the Gronovioideae‐Mentzelia clade.
Stem vascular architecture in the rattan palmCalamus(Arecaceae–Calamoideae–Calaminae)
Authors: Tomlinson P. Barry , Fisher Jack B. , Spangler Russell E. , Richer Renee A.
Published: February 2007

Climbing stems in the rattan genusCalamuscan reach lengths of well over 100 m, are long‐lived, and yet their vascular tissue is entirely primary. Such a combination suggests that stem vasculature is efficient and resistant to hydraulic disruption. By means of an optical shuttle and video recording of sequential images we analyzed the stem of a cultivated species. The stem has vascular features that are unusual compared with those in arborescent palms and seemingly inefficient in terms of long‐distance water transport. Axial bundles are discontinuous basally because leaf traces, when followed downwards, always end blindly below. Furthermore, there is no regular distal branching of each leaf trace at its level of departure into a leaf, so that neither a continuing axial bundle nor bridges to adjacent axial bundles are produced as in the standard palm construction. Instead, the axial bundles in the stem periphery are connected to leaf traces and to each other by narrow and irregular transverse or oblique commissures that are not the developmental homologues of bridges. As in other palms, metaxylem within a leaf trace is not continuous into the leaf so that the only connection to a leaf is via protoxylem. Within the stem, protoxylem (tracheids) and metaxylem (vessels) are never contiguous, unlike in other palms, which suggests that water can only move from metaxylem to protoxylem, and hence into the leaf, across a hydraulic resistance. We suggest that this minimizes cavitation of vessels and/or may be associated with an unknown mechanism that refills embolized vessels. Also, the metaxylem can be significant in stem water storage in the absence of abundant ground parenchyma.
Patterns of allozyme diversity in the threatened plantErigeron parishii(Asteraceae)
Authors: Neel Maile C. , Ellstrand Norman C.
Published: February 2007

Thirty‐one occurrences ofErigeron parishii, a narrowly endemic plant threatened by mining, were sampled for allozyme diversity. This taxon held considerable genetic variation at the 14 allozyme loci surveyed. Species (e.g., alleles per locus [A] = 4.3 and proportion of polymorphic loci [P] = 0.64) and population (e.g.,A= 2.15 [SD = 0.3] and P = 0.53 [SD = 0.12]) genetic diversity measures were higher than expected for narrowly endemic plant taxa. The proportion of polymorphic loci and numbers of alleles per locus indicated thatE. parishiihas not experienced severe or long‐lasting population bottlenecks. Within‐populationfindicated low to moderate levels of inbreeding. Populations were only moderately differentiated (theta‐p = 0.12), suggesting either that there is substantial gene flow among populations or that populations have not been isolated long enough to detect effects of genetic drift. There was no significant differentiation among populations in different vegetation types nor was there a relationship between genetic distance and geographic distance among sites. Continued fragmentation by mining activities would isolate populations, disrupting gene flow, exacerbating loss of diversity, and increasing inbreeding in the remaining fragments. Protection of large, interconnected populations throughout the range of the taxon is warranted to maintain processes that have sustained the observed diversity.
The effect of maternal and paternal environments on seed characters in the herbaceous plant Campanula Americana (Campanulaceae)
Authors: Galloway Laura F.
Published: February 2007

Maternal environments typically influence the phenotype of their offspring. However, the effect of the paternal environment or the potential for joint effects of both parental environments on offspring characters is poorly understood. Two populations of Campanula americana, a woodland herb with a variable life history, were used to determine the influence of maternal and paternal light and nutrient environments on offspring seed characters. Families were grown in the greenhouse in three levels of light or three levels of nutrients. Crosses were conducted within each environmental gradient to produce seeds with all combinations of maternal and paternal environments. On average, increasing maternal nutrient and light levels increased seed mass and decreased percentage germination. The paternal environment affected seed mass, germination time, and percentage germination. However, the influence of the paternal environment varied across maternal environments, suggesting that paternal environmental effects should be evaluated in the context of maternal environments. Significant interactions between family and the parental environments for offspring characters suggest that parental environmental effects are genetically variable. In C. americana, the timing of germination determines life history. Therefore parental environmental effects on germination timing, and genetic variation in those parental effects, suggest that parental environments may influence life history evolution in this system.
Population‐level variation in the expression of heterostyly in three species of Rubiaceae: does reciprocal placement of anthers and stigmas characterize heterostyly?
Authors: Faivre Amy E. , McDade Lucinda A.
Published: February 2007

Heterostyly (i.e., reciprocal placement of anthers and stigmas between two or three floral morphs) is hypothesized to enhance outcrossing and reduce selfing. However, few studies have documented reciprocity among individual plants; instead, mean anther and stigma heights for floral morphs are usually reported, masking interindividual variation. We measured eight floral dimensions for individuals in five populations of three heterostylous Rubiaceae. The three methods used to quantify reciprocity yielded different conclusions regarding the degree to which populations conformed to expectations for heterostylous plants. Only Psychotria poeppigiana had stigma and, to a lesser degree, anther heights in discrete classes. Variation among plants of Bouvardia ternifolia and Psychotria chiapensis yielded a continuum of anther and stigma heights across populations. Comparison of distances between stigma and anthers indicated that only flowers of B. ternifolia had, as expected, a constant value for this distance. Finally, regression relationships between anther and stigma heights and corolla length showed that only in one population each of B. ternifolia and P. poeppigiana, and in P. chiapensis, was distance between anthers and stigmas the same across the range of corolla sizes for both floral morphs. Variation among these species in expression of heterostyly was not clearly linked to phylogenetic relationship or pollinator syndromes. Two approach herkogamous (AH) species were studied for comparison. Flowers of Psychotria brachiata were consistently AH, but flowers of P. pittieri were highly variable. Determining fitness consequences of population‐level variation in sexual systems requires studies linking floral morphology to pollinator behavior and pollen transfer.
Danthonia Spicata (Poaceae) and Atkinsonella Hypoxylon (Balansiae): environmental dependence of a symbiosis
Authors: McCormick Melissa K. , Gross Katherine L. , Smith Robin A.
Published: February 2007

Epiphytic and endophytic fungal infections often enhance plant growth. However, supporting active fungal tissue may be costly to plants in low‐nutrient conditions and may affect the spatial distribution of host plants in heterogeneous environments. We examined the field distribution of Danthonia spicata infected and uninfected by the epiphytic fungus Atkinsonella hypoxylon relative to soil resource levels. We also conducted a greenhouse experiment to determine how D. spicata growth and performance responded to soil fertility and moisture. In two of three field populations, locations where A. hypoxylon occurred had higher ammonia, but lower soil moisture, than locations where D. spicata were uninfected. Infected and uninfected plants had similar growth rates across greenhouse treatments, but infected plants had a performance (size × survival) disadvantage relative to uninfected plants in high‐nutrient, high‐moisture and low‐nutrient, low‐moisture conditions. Field locations with D. spicata had low soil moisture, thus the performance disadvantage of infected plants in low‐nutrient, low‐moisture conditions corresponds to field observations that infected plants are rare in habitats with low ammonia. In a field common garden, infected plants had higher nitrogen concentrations than uninfected plants, suggesting that high nitrogen demand by A. hypoxylon may exclude infected plants from low‐fertility field locations.
Mediterranean climate effects. II. Conifer growth phenology across a Sierra Nevada ecotone
Authors: Royce E. B. , Barbour M. G.
Published: February 2007

Growth and xylem water potential of the lower elevation conifers Pinus jeffreyi and Abies concolor and the higher elevation Pinus monticola and Abies magnifica were monitored in their montane Mediterranean habitat of the southernmost Sierra Nevada mountains of California. Measurements were made across the ecotone between the midmontane and upper montane forests and through light and heavy snowfall years.

Radial stem growth, averaging ∼1.5 mm/yr, started 2 wk after snow melt, providing that maximum air temperatures had reached 21°C, and ended when predawn water potentials fell rapidly at the onset of the summer drought. Leader growth started on or after a fixed date, providing that minimum air temperatures were above −4°C for Pinus species or +2.5°C for Abies species. The cue for leader growth was inferred to be photoperiodic. Leader growth ended when either a determinate internode length of ∼1 mm was reached or predawn water potentials fell rapidly. Abies magnifica grew more rapidly than the low‐elevation species, but had a shorter growth period; its annual leader growth, as a consequence, was only 35 mm/yr vs. 50 mm/yr for the low‐elevation species. Needle growth was similarly determinate in the absence of early drought. This growth phenology contributes to determining species distribution across the ecotone.
Seedlings ofNeuwiedia(Orchidaceae subfamily Apostasioideae) have typical orchidaceous mycotrophic protocorms
Authors: Kristiansen Kim A. , Rasmussen Finn N. , Rasmussen Hanne N.
Published: February 2007

Naturally occurring seedlings ofNeuwiedia veratrifoliawere found in three localities in Sabah, Borneo, Malaysia. Seedlings consisted of an irregular oblong protocorm and a terminal leafy rooted shoot. Protocorms contained mycotrophic tissue of the kind typical of orchid mycorrhiza (tolypophagy). This finding demonstrates an important synapomorphy betweenNeuwiediaand other orchids and strongly supports the monophyly of Orchidaceae in the broad sense, including apostasiod orchids.
Patterns of leaf‐pathogen infection in the understory of a Mexican rain forest: incidence, spatiotemporal variation, and mechanisms of infection
Authors: García‐Guzmán Graciela , Dirzo Rodolfo
Published: February 2007

This study assessed the levels of damage by leaf pathogens and their variability in terms of host species, space (four mature forest sites) and season of the year (dry and rainy), and the mechanisms of infection in the understory of the Los Tuxtlas tropical rain forest. Sixty‐five percent of the species surveyed in the dry season (N = 49) and 64.9% of those surveyed in the rainy season (N = 57) were damaged by fungi. Leaf area damaged per plant, on average, was <1% (range: 0.25–20.52%). There was considerable variation in the degree of infection among species, but not among sites and seasons. The survey showed that 43% of the leaves were damaged by herbivores and pathogens concurrently, 16% showed damage by insect herbivory alone, and only 1.4% of the sampled leaves showed damage by pathogens alone. Pathogenicity assays experimentally confirmed that the predominant mechanism of fungal establishment was wounding, such as that caused by herbivory (or other similar sources), and only rarely did infection occur through direct contact (without wounds). The results revealed the omnipresence of leaf fungal infection, although with low damage per plant, and the importance of herbivorous insects in the facilitation of fungal infection in tropical understory plants.
Different cost of reproduction for the males and females of the rare dioecious shrub Corema conradii (Empetraceae)
Authors: Rocheleau Anne‐Françoise , Houle Gilles
Published: February 2007

Males and females of dioecious plant species often differ in their reproductive investment. Such differences frequently result in differential demographic costs represented by lower growth, survival, and/or frequency of reproduction, and/or by more variable reproductive effort through time for females. We present the results of a study on Corema conradii, a rare dioecious shrub of the coastal dune heathlands of northeastern North America. We estimated the reproductive investment of both males and females, determined their age structure, and compared their spatial patterns in a population at Îles‐de‐la‐Madeleine, Quebec. We also determined the sex ratio of the four populations known to occur on the islands. Males invested more in reproduction at flowering, but when fruit production was considered, female reproductive investment was higher in terms of biomass, Mg, and Ca, but not in terms of N, P, and K. The age frequency distribution of males and females did not differ significantly from one another. The population dispersion pattern was contagious, with patches of similar‐age individuals. There was no spatial segregation between males and females, although the sex ratio varied somewhat spatially. Females did not start reproducing at a later age than males and did not appear to have a shorter longevity. However, the crown and radial growth rates of females were lower than those of males. When estimated by the crown intercept method, the sex ratio of all four populations was male biased. However, because males had a higher crown growth rate, genet sex ratio was in fact balanced. Higher investment in reproduction was associated with a lower growth rate, which represents a differential cost of reproduction according to sex in this species.
Leaf optical properties in higher plants: linking spectral characteristics to stress and chlorophyll concentration
Authors: Carter Gregory A. , Knapp Alan K.
Published: February 2007

A number of studies have linked responses in leaf spectral reflectance, transmittance, or absorptance to physiological stress. A variety of stressors including dehydration, flooding, freezing, ozone, herbicides, competition, disease, insects, and deficiencies in ectomycorrhizal development and N fertilization have been imposed on species ranging from grasses to conifers and deciduous trees. In all cases, the maximum difference in reflectance within the 400–850 nm wavelength range between control and stressed states occurred as a reflectance increase at wavelengths near 700 nm. In studies that included transmittance and absorptance as well as reflectance, maximum differences occurred as increases and decreases, respectively, near 700 nm. This common optical response to stress could be simulated closely by varying the chlorophyll concentration of model leaves (fiberglass filter pads) and by the natural variability in leaf chlorophyll concentrations in senescent leaves of five species. The optical response to stress near 700 nm, as well as corresponding changes in reflectance that occur in the green–yellow spectrum, can be explained by the general tendency of stress to reduce leaf chlorophyll concentration.
Chromosome numbers and pollen stainability of three species of Pacific Island breadfruit (Artocarpus, Moraceae)
Authors: Ragone Diane
Published: February 2007

Chromosome numbers were determined for 48 accessions of breadfruit (Artocarpus altilis, A. mariannensis, and A. camansi [Moraceae]) from 16 Pacific Island groups, Indonesia, and the Philippines. Artocarpus camansi and A. mariannensis exhibit counts of 2n = 56; 2n = 56 (diploidy) and 2n = 84 (triploidy) were observed for A. altilis. Most diploid cultivars of A. altilis were seeded, but two cultivars with reduced seed number were observed. Micronesian accessions included putative interspecific hybrids between A. altilis and A. mariannensis. The majority of these accessions were seedless diploids, but triploid putative hybrids were also observed. Pollen stainablility was shown to correlate with the degree of seediness.
Effect of aquatic weeds on methane emission from submerged paddy soil
Authors: Inubushi Kazuyuki , Sugii Hotaka , Nishino Shouji , Nishino Eisho
Published: February 2007

Paddy fields are one of the dominant anthropogenic sources of methane emission to the atmosphere, and the main passageway of methane from paddy soil is through the rice plant. However, the effect of aquatic weeds on methane emission from rice paddies has not been properly evaluated yet. Methane emission from weeded pots and unweeded ones with anaerobic paddy soil was measured throughout the period of rice growth. More than double the amount of methane was emitted from weeded pots compared with unweeded ones. Peroxidase activity of rice root was not different between weeded and unweeded pots. However, methanogenic bacteria populations were higher in weeded pots than in unweeded ones, while methane oxidation activity, measured by the propylene oxidation technique, was higher in unweeded pots than in weeded ones. Methane oxidation activity of roots from three typical aquatic weeds in paddy fields, Lipocarpha sp., Rotala indica, and Ludwigia epilobioides, was higher than that of rice plants, while lower stems of these aquatic plants showed similar or lower activity compared with the same areas of rice plants. These results indicate that the role of aquatic weeds in paddy soil in methane emission should not be overlooked in evaluating mitigation options for reducing methane emission from paddy fields.
Pollen limitation of reproductive success in two sympatric alpine willows (Salicaceae) with contrasting pollination strategies
Authors: Totland Ørjan , Sottocornola Matteo
Published: February 2007

We compared the extent of pollen limitation on female reproductive success of Salix lanata L., an entirely insect‐pollinated willow, and S. lapponum L., which is 50 : 50% insect : wind pollinated (ambophilous). Supplemental hand‐pollination significantly increased seed number per fruit by nearly 50% in the insect‐pollinated willow, but had no significant impact on seed number in the dually pollinated species. Fruit set was not affected by the treatment in either of the species. These results demonstrate that pollen limitation on reproductive success is most pronounced in the species that depends entirely on insects for pollination. In general, pollinator visitation was highest to S. lapponum, but bumble bees were only observed on S. lanata, suggesting that the quantity and quality of pollinator visitation differed between the species. Our results empirically support the hypothesis that a dual pollination strategy is most effective in alpine environments with low and infrequent pollinator activity and high wind speeds.
Family‐ and population‐level responses to atmospheric CO2 concentration: gas exchange and the allocation of C, N, and biomass in Plantago lanceolata (Plantaginaceae)
Authors: Jenkins Klus Dawn , Kalisz Susan , Curtis Peter S. , Teeri James A. , Tonsor Stephen J.
Published: February 2007

To ascertain the inheritance of responses to changing atmospheric CO2 content, we partitioned response to elevated CO2 in Plantago lanceolata between families and populations in 18 families in two populations. Plants were grown in 35 Pa and 71 Pa partial pressure of CO2 (pCO2) in open‐top chambers. We measured above‐ and belowground mass, carbon (C), nitrogen (N), hexose sugar, and gas exchange properties in both CO2 treatments. Families within populations differed in mass, mass allocation, root : shoot ratios, aboveground percentage N, C : N ratio, and gas exchange properties. The CO2 × family interaction is the main indicator of potential evolutionary responses to changing CO2. Significant CO2 × family interactions were observed for N content, C : N ratio, and photosynthetic rate (A: instantaneous light‐saturated carbon assimilation capacity), intercellular CO2 concentration, transpiration rate (E), and water use efficiency (WUE = A/E), but not for stomatal conductance. Families differed significantly in acclimation across time. The ratio of A in elevated vs. ambient growth CO2, when measured at a common internal CO2 partial pressure was 0.79, indicating down‐regulation of A under CO2 enrichment. Mass, C : N ratio, percentage, C (%C), and soluble sugar all increased significantly but overall %N did not change. Increases in %C and sugar were significant and were coincident with redistribution of N aboveground. The observed variation among populations and families in response to CO2 is evidence of genetic variation in response and therefore of the potential for novel evolutionary trajectories with rising atmospheric CO2.
Correlated evolution of chloroplast heat shock protein expression in closely related plant species
Authors: Knight Charles A. , Ackerly David D.
Published: February 2007

Interspecific variation in chloroplast low molecular weight (cLMW) HSP (heat shock protein) expression was examined with respect to phylogeny, species specific leaf area, chlorophyll fluorescence, and mean environmental conditions within species ranges. Eight species of Ceanothus (Rhamnaceae) were heat shocked for 4 h at several different temperatures. Leaf samples were collected immediately after the heat shock, and cLMW HSP expression was quantified using Western blots. At 45°C species from the subgenus Cerastes had significantly greater cLMW HSP expression than species from the subgenus Ceanothus. Specific leaf area was negatively correlated with cLMW HSP expression after the 45°C heat treatment. In addition, chlorophyll fluorescence (Fv/Fm) 1 h after the heat shocks was positively correlated with cLMW HSP expression. Contrary to our prediction, there was no correlation between July maximum temperature within species ranges and cLMW HSP expression. These results suggest that evolutionary differentiation in cLMW HSP expression is associated with leaf physiological parameters and related aspects of life history, yet associations between climatic conditions within species ranges and cLMW HSP expression require further study.
Pollinator‐mediated selection on a flower color polymorphism in experimental populations of Antirrhinum (Scrophulariaceae)
Authors: Niovi Jones Kristina , Reithel Jennifer S.
Published: February 2007

We quantified pollinator visit behavior, pollen receipt and export, and changes in allele and genotype frequencies from initial Hardy‐ Weinberg conditions in experimental arrays of two color morphs of snapdragons (Antirrhinum majus) visited by freely foraging bumble bees (Bombus appositus and B. flavifrons). The number of pollen grains received by a flower depended most on the number of pollinator visits to the flower, whereas the number of grains exported was best predicted by the total time pollinators spent inside the flower. The pattern of mating generally was assortative with respect to color, as bees tended to overvisit one color or the other within a foraging bout. In arrays where nectar was augmented in one color, the augmented color received both more visits and longer visits. Allele and genotype frequencies in offspring samples were in accord with qualitative expectations based on the pollinator observations, demonstrating that pollinators can directly influence the evolution of single‐locus floral traits, at least under simplified experimental conditions.
The dalbergioid legumes (Fabaceae): delimitation of a pantropical monophyletic clade
Authors: Lavin Matt , Pennington R. Toby , Klitgaard Bente B. , Sprent Janet I. , de Lima Haroldo Cavalcante , Gasson Peter E.
Published: February 2007

A monophyletic pantropical group of papilionoid legumes, here referred to as the “dalbergioid” legumes, is circumscribed to include all genera previously referred to the tribes Aeschynomeneae and Adesmieae, the subtribe Bryinae of the Desmodieae, and tribe Dalbergieae exceptAndira, Hymenolobium, Vatairea, andVataireopsis. This previously undetected group was discovered with phylogenetic analysis of DNA sequences from the chloroplasttrnK(includingmatK) andtrnLintrons, and the nuclear ribosomal 5.8S and flanking internal transcribed spacers 1 and 2. All dalbergioids belong to one of three well‐supported subclades, the Adesmia, Dalbergia, and Pterocarpus clades. The dalbergioid clade and its three main subclades are cryptic in the sense that they are genetically distinct but poorly, if at all, distinguished by nonmolecular data. Traditionally important taxonomic characters, such as arborescent habit, free stamens, and lomented pods, do not provide support for the major clades identified by the molecular analysis. Short shoots, glandular‐based trichomes, bilabiate calyces, and aeschynomenoid root nodules, in contrast, are better indicators of relationship at this hierarchical level. The discovery of the dalbergioid clade prompted a re‐analysis of root nodule structure and the subsequent finding that the aeschynomenoid root nodule is synapomorphic for the dalbergioids.
Vessels in ferns: structural, ecological, and evolutionary significance
Authors: Carlquist Sherwin , Schneider Edward L.
Published: February 2007

We have studied macerated xylem of ferns, supplemented by sections, by means of scanning electron microscopy (SEM) in a series of 20 papers, the results of which are summarized and interpreted here. Studies were based mostly on macerations, but also on some sections; these methods should be supplemented by other methods to confirm or modify the findings presented. Guidelines are cited for our interpretations of features of pit membranes. Fern xylem offers many distinctive features: (1) presence of numerous vessels and various numbers of tracheids in most species; (2) presence of vessels in both roots and rhizomes in virtually all species; (3) presence of specialized end walls in vessels of only a few species; (4) multiple end‐wall perforation plates in numerous species; (5) lateral‐wall perforation plates in numerous species; (6) porose pit membranes associated with perforation plates in all species; and (7) pit dimorphism, yielding wide membrane‐free perforations alternating with extremely narrow pits. Multiple end wall perforation plates and lateral wall perforation plates are associated with the packing of tracheary elements in fascicles in ferns: facets of tips of elements contact numerous facets of adjacent elements; all such contacts are potential sites for conduction by means of perforations. This packing differs from that in primary xylem of dicotyledons and monocotyledons. Porosities in pit membranes represent a way of interconnecting vessel elements within a rhizome or root. In addition, these porosities can interconnect rhizome vessel elements with those of roots, a feature of importance because roots are adventitious in ferns as opposed to those of vascular plants with taproots. Fully‐formed or incipient (small‐to‐medium sized porosities in pit membranes) perforation plates are widespread in ferns. These are believed to represent (1) ease of lysis of pit membranes via pectinase and cellulase; (2) numerous potential sites for perforation plate formation because of fasciculate packing of tracheary elements; (3) evolution of ferns over a long period of time, so that lysis pathways have had time to form; (4) lack of disadvantage in perforation plate presence, regardless of whether habitat moisture fluctuates markedly or little, because ferns likely have maintaining integrity of water columns that override the embolism‐confining advantage of tracheids. Although all ferns share some common features, the diversity in xylem anatomy discovered thus far in ferns suggests that much remains to be learned.
Evolution of the FAD2‐1 fatty acid desaturase 5′ UTR intron and the molecular systematics of Gossypium (Malvaceae)
Authors: Liu Qing , Brubaker Curt L. , Green Allan G. , Marshall Don R. , Sharp Peter J. , Singh Surinder P.
Published: February 2007

The FAD2‐1 microsomal ω‐6 desaturase gene contains a large intron (∼1133 bp [base pairs]) in the 5′ untranslated region that may participate in gene regulation and, in Gossypium, is evolving at an evolutionary rate useful for elucidating recently diverged lineages. FAD2‐1 is single copy in diploid Gossypium species, and two orthologs are present in the allotetraploid species. Among the diploid species, the D‐genome FAD2‐1 introns have accumulated substitutions 1.4–1.8 times faster than the A‐genome introns. In the tetraploids, the difference between the D‐subgenome introns and their A‐subgenome orthologs is even greater. The substitution rate of the intron in the D‐genome diploid G. gossypioides more closely approximates that of the A genome than other D genome species, highlighting its unique evolutionary history. However, phylogenetic analyses support G. raimondii as the closest living relative of the D‐subgenome donor. The Australian K‐genome species diverged 8–16 million years ago into two clades. One clade comprises the sporadically distributed, erect to suberect coastal species; a second clade comprises the more widely spread, prostrate, inland species. A comparison of published gene trees to the FAD2‐1 intron topology suggests that G. bickii arose from an early divergence, but that it carries a G. australe‐like rDNA captured via a previously undetected hybridization event.
Phylogenetic relationships in the genusLeonardoxa(Leguminosae: Caesalpinioideae) inferred from chloroplasttrnL intron andtrnL‐trnF intergenic spacer sequences
Authors: Brouat Carine , Gielly Ludovic , McKey Doyle
Published: February 2007

The African genusLeonardoxa(Leguminosae: Caesalpinioideae) comprises two Congolean species and a group of four mostly allopatric subspecies principally located in Cameroon and clustered together in theL. africanacomplex.Leonardoxaprovides a good opportunity to investigate the evolutionary history of ant–plant mutualisms, as it exhibits various grades of ant–plant interactions from diffuse to obligate and symbiotic associations. We present in this paper the first molecular phylogenetic study of this genus. We sequenced both the chloroplast DNAtrnLintron (677 aligned base pairs [bp]) andtrnL‐trnFintergene spacer (598 aligned bp). Inferred phylogenetic relationships suggested first that the genus is paraphyletic. TheL. africanacomplex is clearly separated from the two Congolean species, and the integrity of the genus is thus in question. In theL. africanacomplex, our data showed a lack of congruence between clades suggested by morphological and chloroplast characters. This, and the low level of molecular divergence found between subspecies, suggests gene flow and introgressive events in theL. africanacomplex.
A phylogenetic analysis of Prunus and the Amygdaloideae (Rosaceae) using ITS sequences of nuclear ribosomal DNA
Authors: Lee Sangtae , Wen Jun
Published: February 2007

The economically important plum or cherry genus (Prunus) and the subfamily Amygdaloideae of the Rosaceae have a controversial taxonomic history due to the lack of a phylogenetic framework. Phylogenetic analysis using the ITS sequences of nuclear ribosomal DNA (nrDNA) was conducted to construct the evolutionary history and evaluate the historical classifications of Prunus and the Amygdaloideae. The analyses suggest two major groups within the Amygdaloideae: (1) Prunus s.l. (sensu lato) and Maddenia, and (2) Exochorda, Oemleria, and Prinsepia. The ITS phylogeny supports the recent treatment of including Exochorda (formerly in the Spiraeoideae) in the Amygdaloideae. Maddenia is found to be nested within Prunus s.l. in the parsimony and distance analyses, but basal to Prunus s.l. in the maximum likelihood analysis. Within Prunus, two major groups are recognizable: (1) the Amygdalus–Prunus group, and (2) the Cerasus–Laurocerasus–Padus group. The clades in the ITS phylogeny are not congruent with most subgeneric groups in the widely used classification of Prunus by Rehder. A broadly defined Prunus is supported.
The Genealogical Mentality in Modern China
Authors: Pieke Frank N.
Published: February 2007

Xuanwei, a county-level municipality (xianji shi) located in the northeastern corner of Yunnan province, has nothing remarkable to boast. It is, of course, one of the largest counties in China and “home of the Yunnan ham.” Xuanwei is even the native place of Zhuo Lin, wife of the late Deng Xiaoping. Such trivia apart, Xuanwei's vital statistics read as a microcosm of interior China that moreover cover a wide variety of ecological and socioeconomic regimes. For mainly this reason, Stig Thøgersen of Aarhus University and I decided in 1998 that Xuanwei's unremarkable status made it the ideal rural inland fieldwork site that we sought for European researchers.
It's All in the Name: Failure-Induced Learning by Multiunit Chains
Authors: Chuang You-Ta , Baum Joel A. C.
Published: February 2007

We examine factors leading multiunit chains to adopt a common naming strategy, that is, naming components in a manner that identifies them with each other and the overall chain, rather than a local naming strategy that identifies a chain's components with their locations but not each other. Because chains' naming strategies have been shown to be critical to their success, we examine the effects of component failures on naming strategies. We advance organizational and interorganizational learning processes to explain chains' adoption of local naming strategies, which stress local adaptation, or common naming strategies, which emphasize standardization. In contrast to past research emphasizing learning from success, we focus on learning from the failure of strategy, specifically, the failure of a chain's own and other chains' commonly and locally named components. Two fundamental results emerge from our analysis of Ontario nursing home chains' naming strategies from 1971 to 1996. One is that nursing home chains learned from their own and others' failures, and the second is that the chains learned less from failures when they had a historical investment in the failing strategy.
Relating Physical Environment to Self-Categorizations: Identity Threat and Affirmation in a Non-Territorial Office Space
Authors: Elsbach Kimberly D.
Published: February 2007

I used qualitative methods to explore why some employees working in a newly created, non-territorial office environment perceived that their workplace identities were threatened and used particular tactics to affirm those threatened identities. Findings suggest that the non-territorial work environment threatened some employees' workplace identities because it severely limited their abilities to affirm categorizations of distinctiveness (versus status) through the display of personal possessions. Categorizations of distinctiveness appeared to be most threatened by the loss of office personalization because of three characteristics: (1) their absolute, rather than graded membership structure, (2) their high subjective importance and personal relevance, and (3) their high reliance on physical markers for affirmation. In affirming threatened identity categorizations, employees chose different tactics, in terms of the amount of effort required and their conformance with company rules, based on the acceptability and importance of affirming the threatened categorization.
The Pressure of the Past: Network Imprinting in Intercorporate Communities
Authors: Marquis Christopher
Published: February 2007

This paper extends organizational imprinting theory to networks by examining how the social technology available during the establishment of community-based intercorporate networks continues to influence contemporary network structures despite major changes in the U.S. corporate environment. I examine the 51 largest U.S. community network systems in 1986, the same networks in 2000, and the network activity of the component organizations of those network systems. Results show that even when controlling for many plausible alternative explanations, communities established prior to the advent of air travel technology have preserved locally focused networks, which suggests that this pattern is maintained by emulation of locally legitimate templates of action. This research contributes to work on imprinting by extending it to networks and in theorizing the social mechanisms that result in the persistence of social forms. Furthermore, it contributes to work on directorship networks by suggesting that the way information flows through this network may be geographically contingent.
Network Structure and Knowledge Transfer: The Effects of Cohesion and Range
Authors: Reagans Ray , McEvily Bill
Published: February 2007

This research considers how different features of informal networks affect knowledge transfer. As a complement to previous research that has emphasized the dyadic tie strength component of informal networks, we focus on how network structure influences the knowledge transfer process. We propose that social cohesion around a relationship affects the willingness and motivation of individuals to invest time, energy, and effort in sharing knowledge with others. We further argue that the network range, ties to different knowledge pools, increases a person's ability to convey complex ideas to heterogeneous audiences. We also examine explanations for knowledge transfer based on absorptive capacity, which emphasizes the role of common knowledge, and relational embeddedness, which stresses the importance of tie strength. We investigate the network effect on knowledge transfer using data from a contract R&D firm. The results indicate that both social cohesion and network range ease knowledge transfer, over and above the effect for the strength of the tie between two people. We discuss the implications of these findings for research on effective knowledge transfer, social capital, and information diffusion.