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Plant Groups (plant + groups)
Selected AbstractsPARASITES, THEIR RELATIONSHIPS AND THE DISINTEGRATION OF SCROPHULARIACEAE SENSU LATOCURTIS'S BOTANICAL MAGAZINE, Issue 4 2010Michael F. Fay Summary. Plants that parasitise other plants have been among the most difficult plant groups to fit into classification systems due to their modified biology and their often highly reduced morphology. They are now considered to be found in about 16 families of flowering plants. Here we summarise current ideas about their relationships and provide information about their characteristics and utilisation. A major consequence of the revised classification of Orobanchaceae and related families has been the break-up of the traditional Scrophulariaceae, and here we summarise the new classification, focusing on genera of horticultural interest. [source] ON QUANTIFYING TOLERANCE OF HERBIVORY FOR COMPARATIVE ANALYSESEVOLUTION, Issue 9 2008Michael J. Wise As the evolutionary importance of plant tolerance of herbivory is increasingly appreciated, more and more studies are not just measuring a plant's tolerance, but are comparing tolerance among plant genotypes, populations, species, and environments. Here, we suggest that caution must be taken in such comparative studies in the choice of measurement scales (and data transformations) for damage levels and plant performance. We demonstrate with a simple scenario of two plant groups of equal tolerance how the choice of scales can lead one to infer that the first group is more tolerant, the second group is more tolerant, or the two groups are equally tolerant,using the identical dataset. We conclude that to make reliable, logically consistent inferences when comparing tolerances among groups of plants, damage and performance should both be on an additive scale or both on a multiplicative scale. [source] Effect of soil and physiographic factors on ecological plant groups in the eastern Elborz mountain rangeland of IranGRASSLAND SCIENCE, Issue 2 2010Mohammadreza Tatian Abstract To investigate the cause of differences among ecological plant groups in the east of the Elborz mountain rangeland, the role of edaphical and topographical characteristics was considered. Two ordination techniques, detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA), were used. The values of slope, aspect, altitude and lithology information were provided by Geographic Information System (GIS), and geomorphological land units were determined by intersection of overlaid data layers. Plant sampling was undertaken within nine land units with similar lithology and altitude but which differed in slope and aspect, using 30 randomly selected 1 m2 plots per land unit. Soil samples were taken from two depths (0,20 and 20,50 cm) in each plot. Organic matter, bulk density, texture, calcium carbonate, total nitrogen and available phosphorus and potassium contents were determined. The results indicated that plant species have different responses to edaphical and topographical parameters. The invader species group had a balanced amount of influence from all soil components and topographic factors, whereas the native grasses were located in productive soils, which typically have a low grazing intensity, such as the north facing slopes. Coniferous bushy trees, cushion plants and some shrub plant groups were found on steep slopes with alkaline soils. The broad-leaved bushy trees plant group was abundant in fine texture soils on low and humid slopes. [source] Patterns of species richness on very small islands: the plants of the Aegean archipelagoJOURNAL OF BIOGEOGRAPHY, Issue 7 2006Maria Panitsa Abstract Aim, To investigate the species,area relationship (SAR) of plants on very small islands, to examine the effect of other factors on species richness, and to check for a possible Small Island Effect (SIE). Location, The study used data on the floral composition of 86 very small islands (all < 0.050 km2) of the Aegean archipelago (Greece). Methods, We used standard techniques for linear and nonlinear regression in order to check several models of the SAR, and stepwise multiple regression to check for the effects of factors other than area on species richness (,habitat diversity', elevation, and distance from nearest large island), as well as the performance of the Choros model. We also checked for the SAR of certain taxonomic and ecological plant groups that are of special importance in eastern Mediterranean islands, such as halophytes, therophytes, Leguminosae and Gramineae. We used one-way anova to check for differences in richness between grazed and non-grazed islands, and we explored possible effects of nesting seabirds on the islands' flora. Results, Area explained a small percentage of total species richness variance in all cases. The linearized power model of the SAR provided the best fit for the total species list and several subgroups of species, while the semi-log model provided better fits for grazed islands, grasses and therophytes. None of the nonlinear models explained more variance. The slope of the SAR was very high, mainly due to the contribution of non-grazed islands. No significant SIE could be detected. The Choros model explained more variance than all SARs, although a large amount of variance of species richness still remained unexplained. Elevation was found to be the only important factor, other than area, to influence species richness. Habitat diversity did not seem important, although there were serious methodological problems in properly defining it, especially for plants. Grazing was an important factor influencing the flora of small islands. Grazed islands were richer than non-grazed, but the response of their species richness to area was particularly low, indicating decreased floral heterogeneity among islands. We did not detect any important effects of the presence of nesting seabird colonies. Main conclusions, Species richness on small islands may behave idiosyncratically, but this does not always lead to a typical SIE. Plants of Aegean islets conform to the classical Arrhenius model of the SAR, a result mainly due to the contribution of non-grazed islands. At the same time, the factors examined explain a small portion of total variance in species richness, indicating the possible contribution of other, non-standard factors, or even of stochastic effects. The proper definition of habitat diversity as pertaining to the taxon examined in each case is a recurrent problem in such studies. Nevertheless, the combined effect of area and a proxy for environmental heterogeneity is once again superior to area alone in explaining species richness. [source] Landscape patterns of indicator plants for soil acidity in the Bavarian AlpsJOURNAL OF BIOGEOGRAPHY, Issue 10 2003Sebastian Schmidtlein Abstract Aim, Electronic distribution atlases and lists of ecological indicator values are becoming important tools in plant geography. In this contribution, we combine a geographical and an ecological data bank, and map out patterns of indicator value spectra (instead of single or average values) across a physiographically complex landscape. For our study, we select indicators of soil pH and carbonate content as key environmental factors that strongly affect overall plant diversity patterns in the temperate zone. Our goal is to relate the distribution and diversity of plant groups that are indicators of soil pH and carbonate content to environmental controls at the landscape-scale, and thus contribute to a causal understanding of species pools. Location, We studied the Bavarian Alps, which represent the German portion of the Northern Alps. Methods, Based on the existing floristic survey, we calculated relative frequencies of nine classes of indicator plants for soil pH and carbonate content in grid cells. The resulting attribute matrix (cells by indicator class frequencies) was subjected to principal components analysis and to k-means clustering. Results were compared and mapped out in the grid array of the whole region, resulting in continuous and discrete representations of species pool structure. We used a geographical information system to derive physiographical landscape properties from a geological map and a digital elevation model, and analysed their statistical relationship with the shapes of indicator spectra. Results and Main conclusions, Averages of indicator values for soil pH and carbonate content follow the geological structure quite closely. Surprisingly, the diversity of indicator plant groups does not appear to be a function of geological or topographic heterogeneity. Rather, it seems to be related to areas of high elevation with uniform geology. The effect is a matter of additional acidophytes in high mountain areas and, in the high calcareous Alps, extreme calciphytes, while species with intermediate requirements are rarer than usual. For explanation, we suggest two facts: (1) a frequent lack of mature soils at high elevations and (2) particularities in soil genetic processes occurring under the harsh climatic conditions of high mountains. [source] Biological images of geological history: through a glass darkly or brightly face to face?JOURNAL OF BIOGEOGRAPHY, Issue 2 2003Jeremy D. Holloway Abstract Aim, To explore the implications for historical biogeography of a recent review of island biogeographical theory in three main thematic areas and to suggest ways in which a synthesis between the two approaches might be achieved to the benefit of both. Location, The Indo-Australian tropics. Theme 1, discusses the relationship of species number to area, and how the nestedness of faunas may influence the methodology used for some types of analysis and also the quality of data expected from an archipelago embracing an extreme range of island sizes. Theme 2, examines the way in which the processes of speciation may lead to development of biogeographical patterns through a complex archipelago, illustrated in particular with reference to Sulawesi where biotic enrichment from different lepidopteran groups follows predictions from island biogeographical theory. This also has implications for patterns of endemism in the archipelago, another constraint on the quality of data available for historical biogeography. Theme 3, addresses ecological determinism as an influence in development of biogeographical pattern, focusing on the theme of specificity in insect,plant relationships and the potential for parallel development of pattern in an insect group and its particular plant host group. This theme is developed with particular reference to moth and plant groups that may represent Gondwanan elements in the Oriental fauna, with an analysis of Sarcinodes, a geometrid moth genus associated with Proteaceae. Main conclusions, Prospects are assessed for the synthesis of the two approaches of island biogeography and historical biogeography. Modelling pattern development with the former may complement the methods of analysis of the latter, particularly if some satisfactory method for dating events of pattern development can also be incorporated. [source] Analysis of plant species diversity with respect to island characteristics on the Channel Islands, CaliforniaJOURNAL OF BIOGEOGRAPHY, Issue 3 2000Aaron Moody Abstract Aim Species richness of native, endemic, and exotic plant groups is examined relative to island area, disturbance history, geological history, and other physical characteristics. Of particular interest are the biogeographic factors that underlie (a) differences in species-area and species-isolation relationships between plant groups; and (b) adherence or departure of individual islands and/or plant groups from expected patterns. Location The eight Channel Islands lie along the continental margin between the U.S./Mexico border and Point Conception, CA. They range in size from 2.6 to 249 km2, and are located from 20 to 100 km off the coast. The islands are known for their high degree of plant endemism, and they have undergone a long history of human occupation by indigenous peoples, followed by over a century of intensive grazing and other biotic disturbances. Methods The study is based on linear regression and residual analysis. Cases where individual islands and/or specific plant groups do not adhere to patterns expected under species-area and species-isolation paradigms, are evaluated with respect to other island characteristics that are not captured by considering only island size and isolation. Results All three plant groups exhibit strong, positive relationships between species richness and island size. For native species, the variance that remains after consideration of island size is largely explained by island isolation. For exotic species, residuals from the species-area relationship are unrelated to isolation. For endemic species, residuals from the species-area relationship are negatively related to isolation. Several islands are outliers for endemic and exotic species, for which richness values are not explained by either island area or isolation. Main,conclusions Species-area and species-isolation relationships for native, endemic, and exotic plant groups differ in accordance with hypothesized differences in the biogeographic factors that govern species diversity for these three groups. Most notably, endemic richness increases with isolation, suggesting the influence of this variable on processes of speciation and relictualism. These general relationships persist despite a long and varied history of human activity on the islands. Analysis of residuals suggests that deviations from expected patterns correspond to island-specific biogeographic factors. It is hypothesized that primary among these factors are land-use history, island environmental characteristics, and community-type richness. [source] The ghost of hybridization past: niche pre-emption is not the only explanation of apparent monophyly in island endemicsJOURNAL OF ECOLOGY, Issue 3 2005TOMÁ? Summary 1Published molecular phylogenies show that many plant groups in the Canary Islands are monophyletic despite the fact that the short distance between the islands and Africa should have led to many independent colonization events. 2Low establishment rates of later migrants owing to niche pre-emption by earlier, already established, colonists could explain these patterns. The apparent monophyly is, however, also compatible with multiple colonizations, with later colonizers making only limited contributions to the total gene pool (and therefore being undetected in the molecular phylogeny) or being wiped out by stochastic processes. 3Experimental evidence for niche pre-emption and species-specific interactions in plants is weak, with survival and establishment of a newly immigrant species depending on the overall composition of the community, rather than on the presence of a particular ,ecologically similar' species. 4Although niche pre-emption might have contributed to the observed patterns of monophyly, we do not think that phylogeographical data from Macaronesia can be taken as evidence for its action in the geological past. [source] Homologous Comparisons of Photosynthetic System I Genes among Cyanobacteria and ChloroplastsJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 8 2008Jie Yu Abstract It has now believed that chloroplasts arose from cyanobacteria, however, during endosymbiosis, the photosynthetic genes in chloroplasts have been reduced. How these changes occurred during plant evolution was the focus of the present study. Beginning with photosystem I (PSI) genes, a homologous comparison of amino acid sequences of 18 subunits of PSI from 10 species of cyanobacteria, chloroplasts in 12 species of eucaryotic algae, and 28 species of plants (including bryophytes, pteridophytes, gymnospermae, dicotyledon and monocotyledon) was undertaken. The data showed that 18 genes of PSI can be divided into two groups: Part I including seven genes (psaA, psaB, psaC, psaI, psaJ, ycf3 and ycf4) shared both by cyanobacteria and plant chloroplasts; Part II containing another 11 genes (psaD, psaE, psaF, psaK, psaL, psaM, btpA, ycf37, psaG, psaH and psaN) appeared to have diversified in different plant groups. Among Part I genes, psaC, psaA and psaB had higher homology in all species of cyanobacteria and chloroplasts. Among Part II genes, only psaG, psaH and psaN emerged in seed plants. [source] Competitive displacement or biotic resistance?JOURNAL OF VEGETATION SCIENCE, Issue 2 2010Disentangling relationships between community diversity, invasion success of tall herbs, shrubs Abstract Questions: Are negative invasion,diversity relationships due to biotic resistance of the invaded plant community or to post-invasion displacement of less competitive species? Do invasion,diversity relationships change with habitat type or resident traits? Location/species: Lowlands and uplands of western and southern Germany, Heracleum mantegazzianum; mountain range in central Germany, Lupinus polyphyllus; and coastal dunes of northwest Germany, Rosa rugosa. Methods: We tested the significance and estimated regression slopes of invasion,diversity relationships using generalized linear (mixed effects) models relating invader cover and habitat type to species richness in different plant groups, stratified based on size, life cycle and community association. Results: We found negative, positive and neutral relationships between invader cover and species richness. There were negative linear correlations of invader cover with small plant species throughout, but no negative linear correlation with tall species. Invasion,diversity relationships tended to be more negative in early-successional habitats, such as dunes or abandoned grasslands, than in late-successional habitats. Conclusions: Invasion diversity,relationships are complex; they vary among habitat types and among different groups of resident species. Negative invasion,diversity relationships are due to asymmetric competitive displacement of inferior species and not due to biotic resistance. Small species are displaced in early-successional habitats, while there is little effect on persistence of tall species. [source] Recovery of plant DNA using a reciprocating saw and silica-based columnsMOLECULAR ECOLOGY RESOURCES, Issue 1 2007PATRICK J. ALEXANDER Abstract The time needed for hand grinding and the cost of commercially available extraction kits remain to be the major limitations in plant DNA extraction for many researchers. We present inexpensive techniques for (i) simultaneously machine grinding large numbers of plant samples for DNA extraction using a commercially available reciprocating saw; and (ii) DNA recovery using silica column-based extractions similar to that used in some commercially available kits. Used together, these allow for the rapid recovery of plant DNA at relatively low cost. Furthermore, these methods appear to be widely applicable within plants with good yields recovered in test extractions across major plant groups (ferns, gymnosperms, monocots and eudicots). [source] O3 impacts on plant development: a meta-analysis of root/shoot allocation and growthPLANT CELL & ENVIRONMENT, Issue 7 2006D. A. GRANTZ ABSTRACT The mechanism of O3 action on plants remains poorly characterized. Symptoms include visible lesions on the leaf surface, reduced growth and a hypothesized reduction in allocation of carbohydrate to roots. The generality of this latter phenomenon has not been demonstrated. Here, a meta-analysis is performed of all available experimental data, to test the hypotheses that O3 exposure of the shoot inhibits biomass allocation below ground (the root/shoot allometric coefficient, k) and inhibits whole-plant growth rate [relative growth rate (RGR)]. Both k and RGR were significantly reduced by O3 (5.6 and 8.2%, respectively). Variability in k was greater than in RGR, and both exhibited some positive as well as mostly negative responses. The effects on k were distinct from the effects on RGR. In some cases, k was reduced while RGR was unaffected. Slow-growing plants (small RGR) exhibited the largest declines in k. These observations may have mechanistic implications regarding O3 phytotoxicity. There were no effects of type of exposure chamber on sensitivity to O3. The analyses indicate that the O3 inhibition of allocation to roots is real and general, but variable. Further experiments are needed for under-represented plant groups, to characterize exceptions to this generalization and to evaluate O3,environment interactions. [source] Understory vegetation response to thinning disturbance of varying complexity in coniferous standsAPPLIED VEGETATION SCIENCE, Issue 4 2009Adrian Ares Abstract Question: Can augmented forest stand complexity increase understory vegetation richness and cover and accelerate the development of late-successional features? Does within-stand understory vegetation variability increase after imposing treatments that increase stand structural complexity of the overstory? What is the relative contribution of individual stand structural components (i.e. forest matrix, gaps, and leave island reserves) to changes in understory vegetation richness? Location: Seven study sites in the Coastal Range and Cascades regions of Oregon, USA. Methods: We examined the effects of thinning six years after harvest on understory plant vascular richness and cover in 40- to 60-year-old forest stands dominated by Douglas-fir (Pseudotsuga menziesii). At each site, one unthinned control was preserved and three thinning treatments were implemented: low complexity (LC, 300 trees ha,1), moderate complexity (MC, 200 trees ha,1), and high complexity (HC, variable densities from 100 to 300 trees ha,1). Gaps openings and leave island reserves were established in MC and HC. Results: Richness of all herbs, forest herbs, early seral herbs and shrubs, and introduced species increased in all thinning treatments, although early seral herbs and introduced species remained a small component. Only cover of early seral herbs and shrubs increased in all thinning treatments whereas forest shrub cover increased in MC and HC. In the understory, we found 284 vascular plant species. After accounting for site-level differences, the richness of understory communities in thinned stands differed from those in control stands. Within-treatment variability of herb and shrub richness was reduced by thinning. Matrix areas and gap openings in thinned treatments appeared to contribute to the recruitment of early seral herbs and shrubs. Conclusions: Understory vegetation richness increased 6 years after imposing treatments, with increasing stand complexity mainly because of the recruitment of early seral and forest herbs, and both low and tall shrubs. Changes in stand density did not likely lead to competitive species exclusion. The abundance of potentially invasive introduced species was much lower compared to other plant groups. Post-thinning reductions in within-treatment variability was caused by greater abundance of early seral herbs and shrubs in thinned stands compared with the control. Gaps and low-density forest matrix areas created as part of spatially variably thinning had greater overall species richness. Increased overstory variability encouraged development of multiple layers of understory vegetation. [source] Is there a relationship between herbaceous species richness and buffel grass (Cenchrus ciliaris)?AUSTRAL ECOLOGY, Issue 5 2005JANICE JACKSON Abstract Cenchrus ciliaris L. (buffel grass) (Poaceae) is recognized as one of Australia's most serious environmental weeds. This introduced grass has been associated with loss of native species and alteration of fire regimes. However, it is also highly valued as a pasture species for arid and semiarid zones and its weed status is highly controversial. Quantitative studies are needed to determine its ecological effects. The relationship between C. ciliaris and herbaceous species richness was investigated in two studies at a range of scales up to 64 m2 in open woodlands in the Dalrymple Shire, north-eastern Queensland. In the first study, the herbaceous species composition of sites with and without C. ciliaris were compared. Cenchrus ciliaris -dominated sites had fewer herbaceous species than non- C. ciliaris sites at all scales investigated and this pattern was found for the major plant groups (perennial grasses, legumes and other forbs) present. In the second study, the relationship between varying levels of C. ciliaris biomass and species richness was investigated. The relationship between varying levels of a dominant native grass, Bothriochloa ewartiana (Domin) C.E. Hubb. (Poaceae), and species richness was also determined for comparison with the C. ciliaris biomass-richness relationship. In this study, species richness was negatively associated with increasing C. ciliaris biomass at some scales and it appeared that C. ciliaris had a greater effect on richness than B. ewartiana. The negative association between C. ciliaris and species richness is consistent with the view that invasion by C. ciliaris poses a threat to biodiversity. However, the precise cause of the relationship has yet to be determined. [source] Testing coevolutionary hypotheses over geological timescales: interactions between Cretaceous dinosaurs and plantsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010RICHARD J. BUTLER Testing coevolutionary scenarios over extended geological timescales is fraught with difficulties. Most tests rely on comparisons of temporal variations in taxonomic diversity for the groups of interest: however, this approach typically excludes spatiotemporal data. Here, we apply a quantitative method that incorporates the spatiotemporal distributions of the proposed coevolving groups using a Geographical Information System. Distributional data for Cretaceous dinosaur and plant groups were mapped onto palaeogeographical reconstructions in a series of time-slices. Within each time-slice, palaeocontinental surfaces were divided into a series of grids, each of which was scored as present, absent or inapplicable (unsampled) for each group. Distributions were compared statistically to determine whether the putative coevolving groups co-occurred within grid squares more or less frequently than expected by chance. Pairwise comparisons were made between herbivorous dinosaur clades and major plant groups (e.g. cycads, angiosperms) on a global scale. Only three nonrepeated associations of marginal significance were recovered, demonstrating that, in general, current knowledge of the spatiotemporal distributions of these groups provides little support for coevolutionary hypotheses. The Geographical Information System methods used are readily applicable to many other questions whose answers are reliant on a detailed knowledge of organismal distributions in time and space. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 1,15. [source] | ||||||||||||||||||||||