bluuebunny/crossref_metadata_2025_split huggingface dataset:
Divergent juvenile growth and development mediated by food limitation and foraging in the water strider Aquarius remigis (Heteroptera: Gerridae)
Authors: Blanckenhorn W. U. 
Published: September 2010

AbstractThe factors leading to variation in growth, development and body size are of central importance for the study of life histories. I investigated the effect of food limitation on patterns of growth and development in the water strider Aquarius remigis (Heteroptera: Gerridae). Groups of 10 juveniles were allowed to develop under field conditions at three different food levels. Food limitation prolonged juvenile development, reduced growth rates and led to smaller adult body size and weight, the most common life‐history response in ectotherms; it also increased the variance among individuals in these traits, demonstrating variance accumulation suggesting divergent growth. Evidence that this resulted from competition among individuals for limited food was equivocal. On the one hand, direct observation of foraging nymphs showed that larger instar individuals were more likely to obtain monopolizable prey items than expected by chance, independent of food level. On the other hand, there was only a trend for the variance in moulting dates to increase when striders were raised in groups as opposed to singly at various temperatures in a controlled laboratory experiment. When food limitation prolongs juvenile development, variance accumulation with age can result from food limitation per se, as well as from random or heritable variation in growth trajectories. Foraging competition may amplify this effect, but not necessarily so. Therefore, it must not be assumed that divergent growth is necessarily caused by food competition.
Movement patterns in the monogamous sleepy lizard (Tiliqua rugosa): effects of gender, drought, time of year and time of day
Authors: Kerr G. D. , Bull C. M. 
Published: September 2010

AbstractTo determine the effect of environment and behaviour on locomotor activity, we explored sex‐based differences in activity patterns before and after mating in the monogamous Australian sleepy lizard Tiliqua rugosa. We obtained continuous records of lizard step counts in the field for two 9‐month activity periods. Lizards moved infrequently in both periods and were active for an average 13.2 (se 0.8)% of the day (07:00–20:00 h). Both sexes significantly reduced activity during drought and outside the spring activity period. Drought in the 2002/2003 period resulted in little reproductive activity, with no sex difference in activity. In early spring of the following period, with normal rainfall and food, males on average took significantly more steps per day, moved significantly faster for longer and covered nearly twice the distance each day as females. Males moved significantly faster in the mornings. Daily activity of both sexes had a unimodal peak around midday in early spring, shifting to distinctly bimodal patterns later in spring and early summer. In the 2‐month pairing period before mating, when resource levels were high, the two sexes adopted different foraging strategies: males switched to a time maximization strategy, whereas females continued with an energy maximization strategy. After mating, females were significantly more active than males, with higher levels of activity in the afternoons. Males may be more active than females before mating because of multiple tasking in males, searching for extra pair matings, defence against rival males or as a signal of vigour by males to females.
A new species of shrew tenrec (Microgale jobihely) from northern Madagascar
Authors: Goodman S. M. , Raxworthy C. J. , Maminirina C. P. , Olson L. E. 
Published: September 2010

AbstractA new species of shrew tenrec in the genus Microgale is described from a series of 12 specimens taken on the south‐western slopes of the Tsaratanana Massif in northern Madagascar and is named Microgale jobihely. This new species is distinguished from other named members of this endemic genus by a variety of mensural and discrete morphological characters. Phylogenetic analysis of the mitochondrial ND2 gene supports its recognition as a distinct species and suggests a sister relationship with the much more widespread Microgale cowani. Microgale jobihely appears to be the only member of this genus that is a very localized endemic, and a biogeographic scenario is presented to explain this observation. It is currently known from a small area of forest, outside of the protected areas system, that is faced with considerable anthropogenic pressure.
Using sparse survey data to investigate the declining abundance of British harbour seals
Authors: Lonergan M. , Duck C. D. , Thompson D. , Mackey B. L. , Cunningham L. , Boyd I. L. 
Published: September 2010

AbstractThis study presents an analysis of changes in the regional abundance of harbour seals Phoca vitulina based on repeated aerial surveys of haulouts, and demonstrates the use of sparse data to deliver advice about population status and management. Generalized linear models with negative binomial errors were used to represent these overdispersed data. The shape parameter of the negative binomial distribution was directly estimated from the data where this was possible. Information from time‐series of counts where there were few gaps in the data was used to improve the estimation of this parameter in areas where fewer surveys had been carried out. The results show that the number of harbour seals in eastern England has not increased since the end of the 2002 phocine distemper epidemic. There is also evidence of a general decline in most of the large harbour seal colonies around Britain. The populations in the Inner Hebrides were an exception, with numbers appearing to be stable or increasing. Between 2001 and 2006, the population in Orkney and Shetland declined by 40% (95% confidence interval: 30–50%), indicating harbour seals in these areas experienced substantially increased mortality or very low recruitment over this period. The widespread declines, ranging from Shetland to The Wash, suggest that the causes may have been present over a large part of the North Sea.
SEEDLINGS
Authors: FENNER M. 
Published: September 2010

SummaryThe factors which cause the death of seedlings were examined and an attempt was made to determine the selective forces to which they are subjected in the field. After briefly dealing with the difficulties of defining a seedling, I examine a few cases from the recent literature in which the causes of seedling mortality are identified and quantified either by monitoring populations under natural conditions or by manipulating the environment experimentally. The special vulnerability of the immediate post‐germination phase is illustrated and the consistent underestimation of seedling loss in many studies is suggested. Some interesting cases of the effects of neighbours on seedling mortality are examined and it is shown that nearest neighbours may affect a seedling's chance of being grazed. It is concluded that since the causes of seedling mortality‐are so varied and unpredictable in most habitats, individual plasticity may provide a better strategy for survival than highly specialized adaptations to specific mortality factors.
POPULATION DYNAMICS – THE INFLUENCE OF HERBIVORY
Authors: VERKAAR H. J. 
Published: September 2010

SummaryNumbers in plant populations often vary widely and, as yet, only a few studies describe adequately how they are determined. The importance of abiotic factors in establishment as well as in determining the carrying capacity of the habitat has been widely recognized. It is also accepted that intraspecific competition for limiting resources may limit numbers in a density‐dependent way. In addition, both herbivores and pathogens may reduce numbers of plants through mechanisms which are either dependent or independent of population density.Herbivory affects plants not only in the vegetative and reproductive phases but also in the pre‐dispersal and post‐dispersal phases of seeds. Because many studies on the population dynamics of plants have been confined to the former phases, the relative importance of herbivores is likely to have been underestimated for the latter. Furthermore, because herbivory often does not result in mortality but in reduced growth and seed production, its effects may be manifested only as reductions in the size of later generations. The effects of herbivory can therefore only be assessed properly if they are studied over several generations.Examples are presented of plant populations in which numbers are determined by competition for limiting resources. However, other situations are recognized in which it is the activity of herbivores which appears to determine numbers. There is a continuing need for studies of population dynamics, but there is an urgent requirement for these studies to be related to a unifying conceptual base.
AN ARCHITECTURAL APPROACH TO THE COMPARATIVE ECOLOGY OF PLANT ROOT SYSTEMS
Authors: FITTER A. H. 
Published: September 2010

SummaryAlthough plants devote a large proportion of their resources to roots, we have a poor understanding of the constraints under which root systems function. Roots are much less variable morphologically than leaves and it is likely that root systems rather than individual roots are the focus of natural selection. In other words, architecture is more important than morphology. Existing classifications of root systems, based on the developmental model, have failed to provide much insight into their functioning and an alternative, topological model is outlined, in which the link is the basic unit of classification. Other components of the architecture of root systems, including link lengths, branching angles and diameters, are considered and the ecological implications of variation in each is discussed.Simulation models of transport and space exploration are discussed and it is shown that resource cost, transport efficiency and exploration efficiency cannot be simultaneously minimized and that optimum form may vary with the mobility of the resource. In general, a ‘herringbone’ structure seems to be the most efficient at exploration of space but the least transport‐efficient and the most expensive.
PHOTOSYNTHESIS AND CARBON ECONOMY OF PLANTS
Authors: OSMOND C. B. 
Published: September 2010

SummaryThe extent to which studies of photosynthesis and carbon economy are, or should be, at the forefront of comparative plant ecology is discussed from the points of view of carbon pathways, water‐use efficiency, irradiance and nutrients, especially nitrogen. The ways in which new integrative and reductionist techniques can be applied to photosynthesis in an ecological control are illustrated and their value assessed. The study of photosynthetic physiology of plants at the edges of their geographical range is urged as a means of understanding both their responses to stress and disturbance, and their competitive interactions.
VARIATION IN GENOMIC FORM IN PLANTS AND ITS ECOLOGICAL IMPLICATIONS
Authors: BENNETT MICHAEL D. 
Published: September 2010

SummaryThe gross form of the nuclear genome varies greatly among plant species in both anatomy and genetic organization. Chromosome number (ft) ranges from 2 to over 600, and ploidy from 1 to over 20. The amount of DNA in the unreplicated haplophase genome (the 1C value) differs by more than 2500‐fold among angiosperms. Although it has been questioned since the 1930s whether such variation is of adaptive significance and whether it is related, perhaps causally, with environmental factors, no direct or causal links have yet been found. However, variation in DNA C‐value has far‐reaching biological consequences and can be of considerable adaptive and hence ecological significance. Strikingly precise interspecific relationships exist between DNA C‐value and many diverse phenotypic characters at the cellular level, and DNA can affect the phenotype in two ways, firstly by expression of its genie content and, secondly, by the biophysical effects of its mass and volume, the latter defined as nucleotypic effects. Nucleotypic variation in DNA C‐value sets absolute limits to both the minimum size and mass of the basic unit of plant anatomy (i.e. the cell) and the minumum time needed to produce a similar cell with newly synthesized organic molecules. Moreover, in complex multicellular vascular plants, such effects at successive cell cycles are additive, so that DNA C‐value influences many characters, including growth rate, seed weight, minimum generation time and type of life‐cycle. Thus, the nucleotype profoundly affects where, when and how plants grow. Selection for a particular genomic form acting on its spatial or temporal consequences may occur at various levels ranging from the cell to the whole organism and may operate throughout the life‐cycle or at just one stage. DNA C‐value is often indirectly related to environmental factors which determine time‐limited environments via selection acting on the temporal phenotypic consequences of nucleotypic variation. However, in the case of radio‐sensitivity, selection for a low DNA C‐value may act directly on the nucleotype itself, as the size of the nuclear DNA target directly affects the ability of the plant to survive.
THE ECOLOGICAL SIGNIFICANCE OF FRUCTAN IN A CONTEMPORARY FLORA
Authors: HENDRY GEORGE 
Published: September 2010

SummaryFrom an extensive literature survey and from analytical data of 130 species from the Sheffield flora, the physiological and molecular attributes, and occurrence of fructan are considered. The exceptionally high concentrations of fructan in many native species and its exclusive vacuolar location are noted. In view of the contention that fructan may function in low temperature tolerance, estimates are given of their maximum vacuolar concentration. For most species examined, this is unlikely to make a significant contribution to low temperature tolerance under the field conditions of the Sheffield flora. The association of high concentrations in the shoots of several species with high nuclear 2C DNA values is recorded. It is this correlation which may be of significance to several early‐season growing species. By maintaining supplies of fructose and sucrose from vacuoles in tissue undergoing expansion at low temperatures (a feature associated with high DNA values), such species obviate the need for transport of carbohydrate over distance as in starch‐storing species. By shortening supply lines at critical cold periods, fructan‐rich species may have a considerable advantage over starch‐storing, small‐celled, transport‐dependent species. However, such an advantage is not commonly exploited by the contemporary Sheffield flora. It is suggested that the ecological significance of fructan may best be seen in floras of the past or in contemporary floras undergoing more severe environmental stresses.
GROWTH AND PARTITIONING
Authors: HUNT RODERICK , LLOYD PHILIP S. 
Published: September 2010

SummaryInnate growth potential and innate patterns of allocation to different plant parts are both subject to physiological limitations. Yet the ways in which these attributes not only vary between species but also exhibit plasticity in response to environmental change are important determinants of ecological behaviour and contribute strands to Plant Strategy Theory. In this paper, we review the evidence for innate variation in growth potential and partitioning and consider the implications of this variation for the development of high‐level ecological syntheses.
INTERSPECIFIC VARIATION IN PLANT ANTI‐HERBIVORE PROPERTIES: THE ROLE OF HABITAT QUALITY AND RATE OF DISTURBANCE
Authors: COLEY PHYLLIS D. 
Published: September 2010

SummaryGeneral patterns of herbivory and plant defence are summarized for a range of tree species studied in a lowland rain forest of Panama. Species growing in comparable micro‐habitats differed by more than three orders of magnitude in the rates of herbivorous damage to mature leaves. Over 70% of this interspecific variation was statistically accounted for by differences in leaf characteristics. Species having tough, fibrous leaves with low nutritional value suffered little herbivory. Concentrations of immobile defences such as tannins and fibre were higher in species with long‐lived leaves. Among species, there was also a significant negative correlation between growth rate and defence, and a positive correlation between growth and herbivory. These results suggest that differences in defence among species are due to interspecific differences in intrinsic growth rates and not to differences in apparency.Theories of plant defence based on interspecific differences in growth rate and apparency are combined in a single general model of plant defence. This model follows Grime's triangular classification of plant strategies and assumes that quality of habitat and rate of disturbance are both important determinants of plant defence. Predictions are made as to the types of defensive properties expected in stress‐tolerant, competitive and ruderal species.
Reconciling the incompatible: N2fixation And O2
Authors: Gallon J. R. 
Published: September 2010

summaryN2fixation is an extremely O2‐sensitive process. N2‐fixing bacteria (diazotrophys) have therefore evolved a variety of strategies by which they maintain an active nitrogenase in the presence of atmospheric O2and, in some cases, of O2generated photosynthetically. In this review, the effects of O2on nitrogenase activity and synthesis are described, as are the mechanisms by which diazotrophs limit O2damage to nitrogenase. These mechanisms are classified as behavioural strategies, physical barriers or physiological and biochemical strategies. Individual diazotrophs frequently empoly a combination of these. In addition, the particular problems faced by the O2‐evolving cyanobacteria are discussed.CONTENTSSummary571I.Introduction571II.N2fixation571III.O2toxicity574IV.Interrelations between O2and N2fixation577V.Strategies for limiting O2damage to nitrogenase581Acknowledgements601References602
Seedlings of black birch (Betula lentaL.) as foragers for nitrogen
Authors: Crabtree R. C. , Bazzaz F. A. 
Published: September 2010

summarySoil nitrogen environments are highly heterogeneous, containing microsites that differ in relative and absolute ammonium and nitrate contents. We investigated whether black birch (Betula lentaL.) seedlings can maximize growth by foraging preferentially for a particular form of nitrogen, and whether supply rate of N and ammonium: nitrate in a patch affects preferences. Seedlings were transplanted into 5 1 split pots with roots partitioned evenly, and assigned to 1 of 4 nitrogen form treatments: nitrate (NO3−) both sides, ammonium (NH4+) both sides, NH4NO3, ‘homogeneous choice, and NO3−one side/NH4+on the other, ‘patchy choice, crossed with two rates of nitrogen supply. Use of15N–labelled nitrate revealed the proportion of seedling N from nitrate. Seedlings offered a patchy choice did not significantly out–perform seedlings in homogeneous ammonium and nitrate treatments, whereas seedlings offered a homogeneous choice did out–perform homogeneous nitrate and patchy choice treatment plants. In choice treatments, approx. 35 % of seedling N came from a nitrate source. This selectivity was unaffected by rate of nitrogen application and ammonium: nitrate ratio. That patchy choice seedlings integrated patches to achieve this ammonium: nitrate uptake suggests that black birch has a preferred balance. The seedlings offered a homogeneous choice were significantly heavier than the seedlings offered a patchy choice, perhaps reflecting an additional cost of foraging for ammonium and nitrate separately.
Effects of nitrogen on the response of loblolly pine to water stress I. Photosynthesis and stomatal conductance
Authors: Green T. H. , Mitchell R. J. 
Published: September 2010

summaryPhotosynthetic and stomatal response of loblolly pine (Pinus taeda L.) to water stress were determined for seedlings grown under 4 different nitrogen levels. Photosynthetic rate of well–watered seedlings was linearly related to foliar N. There was no observed N effect on the relative reduction of photosynthesis due to water stress. N did not influence stomatal conductance before or during the water stress period. Therefore, instantaneous water use efficiency of well–watered seedlings was significantly increased with increased N. Significantly reduced internal CO2 concentration (Ci) associated with increased N in well–watered seedlings may be indicative of greater relative stomatal contribution to overall limitation of photosynthesis. Water stress caused an increase in Ci, the slope of the increase being related to N treatment. Stomatal conductance and photosynthesis correlated strongly within each N treatment, and increased N caused an increase in initial slope of the function. Therefore, stomatal control was uncoupled from photosynthetic capacity by N treatment in loblolly pine. These data fail to support the proposition that improved stomatal response to water stress can explain reported gains in water status of nitrogen–fertilized conifers in the field.
Nutrient status, water uptake and gas exchange for three desert succulents infected with mycorrhizal fungi
Authors: CUI Muyi , NOBEL Park S. 
Published: September 2010

summaryMycorrhizal infection and its consequences were assessed for Agave deserti Engelm., Ferocactus acanthodes (Lem.) Britton & Rose, and Opuntia ficus–indica (L.) Miller. For A. deserti and F. acanthodes in the field, mycorrhizal infection varied from 2 to 11%; the higher infection in May than in March 1991 was probably associated with improved soil water conditions. Using field–collected fungi, mycorrhizal infection for glasshouse–grown A. deserti, F. acanthodes and O. ficus–indica varied from 8 to 64%, with the highest infection occurring for lateral roots of A. deserti. Five months after inoculation, root P was significantly higher (P > 0—‐01) for inoculated A. deserti and shoot P and Zn were significantly higher (P < 002) for inoculated A. deserti and F. acanthodes compared with uninoculated plants. Root hydraulic conductivity (Lp) of lateral roots of A. deserti was 24% higher for inoculated than for uninoculated plants (P 01). The increase in Lp was caused by a higher radial conductivity, which could be due to increased root cell membrane permeability and more hyphal entry points. Daily net CO2 uptake was 19% higher for inoculated than uninoculated A. deserti. Mycorrhizal infection apparently enhances water and nutrient uptake in dry environments for these three desert succulents.
Mycorrhizas and drought resistance of Picea sitchensis (Bong.) Carr.
Authors: LEHTO TARJA 
Published: September 2010

summarySitka spruce [Picea sitchensis (Bong.) Carr.] seedlings either mycorrhizal with Paxillus involutus (Batsch) Fr. or non–mycorrhizal were either subjected to drought or watered adequately. Stomatal conductance, net photosynthetic rate and water potential were higher in well–watered mycorrhizal plants than in non–mycorrhizal plants, and the effect of mycorrhizal infection on photosynthesis was interpreted as both a stomatal effect and an effect on the photosynthetic apparatus. During the drought treatment the mycorrhizal plants dried out their substrate sooner than the non–mycorrhizal plants, which were smaller, but their stomatal conductance, net photosynthetic rate and shoot water potential were similar to the non–mycorrhizal plants. A correlation between P concentration in the shoot and net photosynthetic rate was shown. The improved performance of the mycorrhizal seedlings was probably due to their better P and K nutrition and their more extensive root systems with mycelial strands.