bluuebunny/crossref_metadata_2025 huggingface dataset:
The use of AUSRIVAS predictive models to assess the response of lotic macroinvertebrates to dams in south‐east Australia
Authors: MARCHANT R. , HEHIR G.
Published: March 2003

1. Sites immediately below seven dams in Victoria and 12 in southern New South Wales (NSW) were sampled for macroinvertebrates using rapid bioassessment techniques. Specimens were identified to the lowest taxonomic level. The dams had different operating and discharge regimes and thus potentially different downstream effects on this fauna.

2. The AUStralian RIVer Assessment Scheme (AUSRIVAS) predictive models for macroinvertebrate composition were applied to the families and genera observed at Victorian sites and to the families only at the NSW sites. Lists of predicted taxa, their probabilities of occurrence and ratios of observed to expected taxa (O/E scores) were obtained from these models.

3. The mean O/E score for Victoria was 0.46 at the genus level and 0.63 at the family level; for NSW the mean score at the family level was 0.62. There was no significant difference between family level scores for the two states. Thus about 40% of expected families were missing at all sites. Family level scores were highly correlated (r=0.84–0.86, P < 0.001) with numbers of families or species at a site.

4. There was no correlation between family O/E scores (or family and species richness) and the degree to which current discharge levels below a dam differ from the natural patterns. Thus increased hydrological deviation did not result in greater biological degradation. In addition, there was no association between these biological characteristics and whether dams released surface or bottom water.

5. All the dams seemed to cause much the same disruption to the fauna. Of the families predicted to have widespread occurrence, 9–12 were found at most sites (tolerant taxa), while a larger number (14–24) were missing (intolerant taxa). The limited recolonisation below dams may well be because of the fact that dams act as barriers to drift, the most prominent route for invertebrate colonists.
Ferox Trout (Salmo trutta) as `Russian dolls': complementary gut content and stable isotope analyses of the Loch Ness foodweb
Authors: GREY J. , THACKERAY S. J. , JONES R. I. , SHINE A.
Published: March 2003

1. Conventional collection methods for pelagic fish species (netting, trawling) are impractical or prohibited in Loch Ness, U.K. To investigate trophic relationships at the top of the Loch Ness food web, an alternative strategy, angling, provided samples of the top predator, the purely piscivorous ferox trout (Salmo trutta).

2. The gut contents of these fish provided further samples of prey‐fish, and subsequent examination of prey‐fish guts revealed their dietary intake, analogous to the famous nested `Russian dolls'. Each trophic level separated by gut content analysis provided further complementary samples for stable isotope analysis and thus information on the longer term, assimilated diet.

3. Ferox trout exhibited considerable cannibalism to supplement a diet of Arctic charr (Salvelinus alpinus). However, conspecifics stemmed from a lower isotopic baseline in relation to charr, so ferox trout exhibited a lower trophic level than predicted (4.3) by using the δ15N values. Charr displayed dietary specialisation with increasing length, and isotopic values supported by the gut data placed the charr at a trophic level of 3.5. The isotope data also indicated that charr carbon was primarily autochthonous in origin.
Simple predictions of instream habitat model outputs for target fish populations
Authors: LAMOUROUX NICOLAS , CAPRA HERVÉ
Published: March 2003

1. Bottom‐up approaches based on individual behaviour can help to identify key variables influencing populations at larger scales. Instream habitat models have been developed to predict the consequences, for populations in stream reaches, of fish preferences for particular hydraulic conditions observed at the scale of individuals. Conventional instream habitat models (e.g. PHABSIM) predict habitat values for species or life stages in reaches, and their changes with discharge. Despite their worldwide use, they have been subject to continuing criticism and have been mainly limited to site‐specific case studies.

2. We ran conventional instream habitat models in 58 French stream reaches dominated by brown trout. Using non‐linear mixed effect models, we demonstrated that the outputs of instream habitat models (habitat values for three trout life stages and five other species) are predictable from average characteristics of reaches (discharge, depth, width and bed particle size).

3. Our models closely reflect variations in habitat values within‐reaches (with discharge) and between‐reaches. Within‐reach changes are linked to the Reynolds number of reaches, while between‐reach changes depend mainly on the Froude number at median daily discharge. These two dimensionless variables combine discharge, mean depth and mean width of reaches. Independent model validations showed robust model predictions that are consistent with studies of habitat values for brown trout made in larger streams from western North America.

4. Our results contribute to identifying the main hydraulic variables governing estimates of fish habitat values. They should facilitate habitat studies in multiple streams, at the basin or larger scales, while reducing their cost. They should enhance the biological validation of habitat model predictions, which remains critical.
Global patterns of diversity among the specialist birds of riverine landscapes
Authors: BUCKTON S. T. , ORMEROD S. J.
Published: March 2003

1. Despite the growing view that biodiversity provides a unifying theme in river ecology, global perspectives on richness in riverine landscapes are limited. As a result, there is little theory or quantitative data on features that might have influenced global patterns in riverine richness, nor are there clear indications of which riverine landscapes are important to conservation at the global scale. As conspicuous elements of the vertebrate fauna of riverine landscapes, we mapped the global distributions of all of the world's specialist riverine birds and assessed their richness in relation to latitude, altitude, primary productivity and geomorphological complexity (surface configuration).

2. Specialist riverine birds, typical of high‐energy riverine landscapes and dependent wholly or partly on production from river ecosystems, occur in 16 families. They are represented by an estimated 60 species divided equally between the passerines and non‐passerines. Major radiation has occurred among different families on different continents, indicating that birds have evolved several times into the niches provided by riverine landscapes.

3. Continental richness varies from four species in Europe to 28 in Asia, with richness on the latter continent disproportionately larger than would be expected from a random distribution with respect to land area. Richness is greatest in mountainous regions at latitudes of 20–40°N in the riverine landscapes of the Himalayan mountains, where 13 species overlap in range.

4. Family, genus and species richness in specialist riverine birds all increase significantly with productivity and surface configuration (i.e. relief). However, family richness was the best single predictor of the numbers of species or genera. In keeping with the effect of surface configuration, river‐bird richness peaks globally at 1300–1400 m altitude, and most species occur typically on small, fast rivers where they feed predominantly on invertebrates. Increased lengths of such streams in areas of high relief and rainfall might have been responsible for species–area effects.

5. We propose the hypothesis that the diversity in channel forms and habitats in riverine landscapes, in addition to high temperature and primary productivity, have been prerequisites to the development of global patterns in the richness of specialist riverine organisms. We advocate tests of this hypothesis in other taxonomic groups. We draw attention, however, to the challenges of categorically defining riverine organisms in such tests because (i) rivers grade into many other habitat types across several different ecotones and (ii) `terrestrialisation' processes in riverine landscapes means that they offer habitat for organisms whose evolutionary origins are not exclusively riverine.
Endogenous regulation of environmentally induced sexuality in a rotifer: a multigenerational parental effect induced by fertilisation
Authors: Gilbert John J.
Published: March 2003

SUMMARY1. Sexual reproduction in the heterogonic life cycle of many rotifers occurs when amictic females, which produce diploid eggs developing parthenogenetically into females, are environmentally induced to produce mictic females. Mictic females produce haploid eggs which develop parthenogenetically into males or, if fertilised, into resting eggs – encysted embryos which develop into amictic females after an obligatory diapause.

2. A Florida strain ofBrachionus calycifloruswas used to test the prediction that amictic females hatching from resting eggs (Generation 1), and those from the next few parthenogenetic generations, have a lower propensity to produce mictic daughters in response to crowding than those from later parthenogenetic generations. In 10 replicate clones, populations initiated by amictic females from generations 1, 5, 8, 12 and 18 were exposed to a standardised crowding stimulus, and the proportion of mictic females in the populations was determined. These proportions varied significantly across generations and clones. They were very low in the early generations and gradually increased to a mean of about 0.5 at Generation 12.

3. The mechanism for the transgenerational plasticity in response to crowding is not known. One possibility is that resting eggs contain an agent from their fertilised mictic mother's yolk gland that prevents development into mictic females and is transmitted in increasingly low concentrations through successive parthenogenetic generations of amictic females.

4. This parental effect may contribute to clonal fitness by ensuring that a clone developing from a resting egg will attain a higher population size through female parthenogenesis before maximising its commitment to sexual reproduction, even in the presence of a crowding stimulus from a high population density of other clones. Therefore, the number of resting eggs to which a clone contributes its genes should be maximised.

5. The clonal variation in propensity to produce mictic females in this strain indicates genetic variation in the trade‐off between maximising population growth via female parthenogenesis and increasing the probability of producing at least some resting eggs before local extinction from the plankton.
The effect of small zooplankton on the microbial loop and edible algae during a cyanobacterial bloom
Authors: Ventelä Anne‐Mari , Wiackowski Krzysztof , Moilanen Marianne , Saarikari Vesa , Vuorio Kristiina , Sarvala Jouko
Published: March 2003

SUMMARY 1. We studied the effect of the small crustacean zooplankton on heterotrophic micro‐organisms and edible phytoplankton in a eutrophic lake during a cyanobacterial bloom.

2. Small (15 L) enclosures were filled with natural or screened (100 μm) lake water and incubated for 5 days in the lake. Screening removed crustacean zooplankton but the initial density of rotifers and phytoplankton remained the same in control and removal treatments. Changes in the abundance and biomass of bacteria, autotrophic picoplankton (APP), heterotrophic nanoflagellates (HNF) and ciliates were measured daily.

3. The crustacean zooplankton, dominated by the small cladoceran Chydorus sphaericus, did not affect cyanobacteria, the main phytoplankton group during the experiment.

4. The removal of the crustacean zooplankton induced a higher abundance of ciliates and reduced that of the HNF, indicating the importance of ciliates in controlling HNF in this system.
Genetic structure and dispersal of Macrobrachium australiense (Decapoda: Palaemonidae) in western Queensland, Australia
Authors: Cook Benjamin D. , Bunn Stuart E. , Hughes Jane M.
Published: March 2003

SUMMARY 1. The freshwater prawn, Macrobrachium australiense (Decapoda: Palaemonidae), is an abundant species throughout the rivers of western Queensland, and it is thought to have effective dispersal capabilities. Given the very low topographical relief of the western Queensland landscape and the vast nature of episodic flooding, it was predicted that widespread dispersal in this species would occur within, and possibly between the four major catchments of the region: the Darling, Bulloo, Cooper and Diamantina. We analysed eight polymorphic allozyme systems and a fragment of the cytochrome c oxidase subunit 1 (COI) mitochondrial DNA (mtDNA) gene to determine the extent of recent and historical patterns of dispersal at nested spatial scales, within and between catchments.

2. Large and significant levels of allozyme and mtDNA differentiation were revealed among all catchments, indicating that dispersal of M. australiense does not occur across catchment boundaries, although this species is reportedly capable of overland movement. In contrast, no significant patterns of genetic differentiation were resolved between major subcatchments of the Darling and Cooper, or between sites within these subcatchments, indicating that populations of M. australiense are panmictic within catchments.

3. The MtDNA data resolved two divergent and reciprocally monophyletic clades, with the first representing the Darling catchment, and the second corresponding to the Bulloo, Cooper and Diamantina catchments. We postulate that extreme variation in historical climatic patterns and palaeohydrologic conditions played an important role in shaping the population structure of M. australiense throughout western Queensland during the Quaternary.
Effects of cadmium stress on periphytic diatom communities in indoor artificial streams
Authors: Gold Caroline , Feurtet‐Mazel Agnès , Coste Michel , Boudou Alain
Published: March 2003

SUMMARY 1. Two experiments were performed with periphytic diatoms originating from the River Lot (France) and allowed to grow on clean substrata within indoor artificial streams. Three cadmium (Cd) levels (control, low Cd=10 μg L−1 and high Cd=100 μg L−1) were used to test the effects of Cd on (i) the settlement and development of diatom communities (Experiment 1, 4 weeks Cd exposure) and (ii) predeveloped communities grown over a 2‐week period without contamination (Experiment 2, 2 weeks Cd exposure).

2. Experiment 1 revealed that growth and taxonomic composition of diatom communities clearly differed with Cd exposure. Biofilms were more adpressed to substrata under low Cd concentration, and were thinner and patchy under high Cd concentration.

3. Exposure of developed diatom communities (Experiment 2) to Cd revealed only minor variations in taxonomic composition, possibly linked to the protective role of the developed organic matrix against metal stress.

4. These results support the validity of periphytic diatom communities as indicators of metal pollution, although significant structural changes would take longer within developed communities.
The independent and interactive effects of fine sediment and flow on benthic invertebrate communities characteristic of small upland streams
Authors: Bond Nicholas R. , Downes Barbara J.
Published: March 2003

SUMMARY 1. Floods are an important mechanism of disturbance operating in streams that can markedly influence the abundance and diversity of benthic fauna. In upland streams many studies cite the scouring effects of fine transported sediments as a potential source of disturbance to the biota during spates, but few studies have sought to test this hypothesis critically.

2. Here we used a series of eight artificial streams to test whether high suspended‐sediment concentrations influenced the short‐term response of benthic invertebrate fauna to increases in flow. In an experiment designed to simulate a small spate, flow and sediment loads were each manipulated to examine their independent and interactive effects. Benthic invertebrates were sampled before and after the manipulation, and drift samples were taken at regular intervals during the experiment. The experiment was repeated twice, once at the end of winter (June, 1998), and once in summer (February, 1999).

3. Flow increases caused large increases in the number and diversity of drifting animals, and significant declines in the numbers and diversity of organisms found in benthic samples, but these declines were apparently not affected by the addition of fine sediment. The addition of sediment alone had little effect on the fauna. These results were consistent across both experiments.

4. The results suggest that flow increases alone can disturb benthic fauna, and that neither substrate movement nor suspended sediment increases are necessary for floods and spates to disturb the benthic assemblage. However, as argued elsewhere, the effects of flow increases are likely to be contingent upon the presence or absence of local flow refugia, which can allow animals to escape the shear forces that would otherwise remove them from the surface or interstitial areas of the streambed.
Soil nutrient input effects on seed longevity: a burial experiment with fen‐meadow species
Authors: Bekker R. M. , Knevel I. C. , Tallowin J. B. R. , Troost E. M. L. , Bakker J. P.
Published: March 2003

1. Effects of high nutrient input on the longevity and viability of buried seed are examined. Seeds of 17 fen‐meadow species were buried in nylon mesh bags at four sites in the Netherlands and one site in Great Britain in plots to which N, P, K fertilizers are applied. Prior to burial germination tests were conducted on the seeds of each species. This paper describes the results of the viability tests on the seeds that were exhumed after one and 2 years of burial.

2. The percentage of seeds that germinated after 1 year of burial was significantly lower than the pre‐burial percentage for the majority of the species. After 2 years of burial the germination percentage further decreased. A few species, such as the Carex species, did, however, show an increase in germination percentage indicating that the burial conditions allowed dormancy controls to be broken.

3. Differences in the edaphic conditions between the sites appeared to affect germination percentages after 1 year of burial. A difference in germination response between sites was observed for Carex acutiformis, Filipendula ulmaria and Lychnis flos‐cuculi.

4. A significantly higher germination percentage was found at the Great Britain site for F. ulmaria in the phosphate treatment compared with the potassium treatment and the control after 1 year of burial. In contrast to many literature assessments no significant effects of fertilizer application was found after 2 years.

5. For all sites, except one in the Netherlands, the total number of seeds that germinated was lower in 1996 than in 1995.
Seasonal and annual changes in leaf δ13C in two co‐occurring Mediterranean oaks: relations to leaf growth and drought progression
Authors: Damesin C. , Rambal S. , Joffre R.
Published: March 2003

1. Changes of δ13C and its relation to leaf development, biochemical content and water stress were monitored over a 2 year period in two co‐occurring Mediterranean oak species: the deciduous Quercus pubescens and the evergreen Quercus ilex.

2. The time course of leaf δ13C showed different patterns in the two species. Young Q. pubescens leaves had a high δ13C and a marked decrease occurred during leaf growth. In contrast, leaves at budburst and maturity did not differ significantly in the case of Q. ilex. We suggest that the difference between δ13C of young leaves was linked to differential use of reserves of carbon compounds in the two species.

3.δ13C values of mature leaves were negatively correlated with minimum seasonal values of predawn water potential, suggesting that a functional adjustment to water resources occurred.

4. There was a significant correlation between individual δ13C values for two successive years. This interannual dependence showed that δ13C rankings between trees were constant through time.
In situ responses to elevated CO2 in tropical forest understorey plants
Authors: WÜrth M. K. R. , Winter K. , KÖrner CH.
Published: March 2003

1. Plants growing in deep shade and high temperature, such as in the understorey of humid tropical forests, have been predicted to be particularly sensitive to rising atmospheric CO2. We tested this hypothesis in five species whose microhabitat quantum flux density (QFD) was documented as a covariable. After 7 (tree seedlings of Tachigalia versicolor and Beilschmiedia pendula) and 18 months (shrubs Piper cordulatum and Psychotria limonensis, and grass Pharus latifolius) of elevated CO2 treatment (c. 700 μl litre–1) under mean QFD of less than 11 μmol m–2 s–1, all species produced more biomass (25–76%) under elevated CO2.

2. Total plant biomass tended to increase with microhabitat QFD (daytime means varying from 5 to 11μmol m–2 s–1) but the relative stimulation by elevated CO2 was higher at low QFD except in Pharus.

3. Non‐structural carbohydrate concentrations in leaves increased significantly in Pharus (+ 27%) and Tachigalia (+ 40%).

4. The data support the hypothesis that tropical plants growing near the photosynthetic light compensation point are responsive to elevated CO2. An improved plant carbon balance in deep shade is likely to influence understorey plant recruitment and competition as atmospheric CO2 continues to rise.
Maternal effects and their consequences for offspring fitness in the Yellow Dung Fly
Authors: Jann P. , Ward P. I.
Published: March 2003

1. Maternal adult diet and body size influence the fecundity of a female and possibly the quality and the performance of her offspring via egg size or egg quality. In laboratory experiments, negative effects in the offspring generation have often been obscured by optimal rearing conditions.

2. To estimate these effects in the Yellow Dung Fly, Scathophaga stercoraria, how maternal body size and adult nutritional status affected her fecundity, longevity and egg size were first investigated.

3. Second, it was investigated how female age and adult nutritional experience, mediated through the effects of egg size or egg quality, influenced the performance of offspring at different larval densities.

4. Maternal size was less important than maternal adult feeding in increasing reproductive output. Without food restriction, large females had larger clutch sizes and higher oviposition rates, whereas under food restriction this advantage was reversed in favour of small females.

5. Offspring from mothers reared under nutritional stress experienced reduced fitness in terms of egg mortality and survival to adult emergence. If the offspring from low‐quality eggs survived, the transmitted maternal food deficiency only affected adult male body size under stressful larval environments.

6. Smaller egg sizes due to maternal age only slightly affected the performance of the offspring under all larval conditions.
Reverse flow of sap in tree roots and downward siphoning of water by Grevillea robusta
Authors: SMITH D. M. , JACKSON N. A. , ROBERTS J. M. , ONG C. K.
Published: March 2003

1. Constant‐power heat‐balance sap flow gauges were used to compare sap flow in vertical and lateral roots of Grevillea robusta trees growing without access to ground water at a semiarid site in Kenya.

2. Reversal of sap flow occurred when root systems crossed gradients in soil water potential. Measurement of changes in the direction of flow was possible because of the symmetrical construction of the sap flow gauges; gradients in temperature across the gauges, and thus computed rates of sap flow, changed sign when reverse flow occurred.

3. Reverse flow in roots descending vertically from the base of the tree occurred, while uptake by lateral roots continued, when the top of the soil profile was wetter than the subsoil. The transfer of water downwards by root systems, from high to low soil water potential, was termed ‘downward siphoning’; this is the reverse of hydraulic lift.

4. Downward siphoning was induced by the first rain at the end of the dry season and by irrigation of the soil surface during a dry period.

5. Downward siphoning may be an important component of the soil water balance where there are large gradients in water potential across root systems, from a wet soil surface downwards. By transferring water beyond the reach of shallow‐rooted neighbours, downward siphoning may enhance the competitiveness of deep‐rooted perennials.
Energy budgets of lactating and non‐reproductive Brown Long‐Eared Bats (Plecotus auritus) suggest females use compensation in lactation
Authors: Mclean J. A. , Speakman J. R.
Published: March 2003

1. The energy budgets of lactating and non‐reproductive female Brown Long‐Eared Bats fed primarily on noctuid moths (≈ 27·2 kJ g–1) were constructed and compared in flight enclosures in captivity.

2. The average dry food consumption of non‐reproductive individuals was 1·8 g bat–1 day–1 (gross energy intake = 48 kJ day–1). The average food consumption throughout days 10–35 of lactation was 2·0 g bat–1 day–1 (gross energy intake = 53 kJ day–1). Lactating females obtained six times more energy from increased food consumption than from mobilization of fat stores, compared with non‐reproductive bats.

3. Milk export, calculated using the difference in water turnover between lactating and non‐reproductive bats (measured using 2H turnover) averaged 2·6 ml bat–1 day–1 (22·9 kJ day–1). This was similar to the average milk intake of sucklings estimated from 3H turnover (22·9 kJ day–1).

4. Energy available for respiration from food and mobilization of fat stores was 18·2 kJ day–1 for lactating females compared with 36·8 kJ day–1 for non‐reproductive females. In comparison, respiratory daily energy expenditure (DEE) of lactating and non‐reproductive bats, measured by doubly labelled water (DLW), was 21·3 kJ day–1 and 23·6 kJ day–1, respectively. Hence, there was a discrepancy between respiratory DEE (measured by DLW) and net available energy estimates for non‐reproductive bats but not for lactating bats.

5. Respiratory DEE for lactating bats was equal to or less than that of non‐reproductive females, suggesting they used compensatory mechanisms in their energy budgets in lactation.
The CO2dependence of photosynthesis, plant growth responses to elevated CO2concentrations and their interaction with soil nutrient status, II. Temperate and boreal forest productivity and the combined effects of increasing CO2concentrations and increased nitrogen deposition at a global scale
Authors: Lloyd J.
Published: March 2003

1.Appropriate rates of carbon acquisition by temperate and boreal forests are re‐evaluated. Based on continental‐scale forestry data it is suggested that the productivity of temperate and boreal forests has been overestimated previously.

2.Using these values, a model of the integrated response of ecosystems to carbon dioxide concentration and soil nitrogen availability is presented. The model does not assume constant C/N ratios in plant or soil and considers effects of increases in atmospheric CO2concentrations and nitrogen deposition separately or together.

3.For temperate‐zone forests a co‐occurrence of a CO2increase and nitrogen deposition doubles the increase in net primary productivity and carbon sequestration that would be the case for nitrogen deposition occurring on its own. Considered separately, the effect of the atmospheric CO2increase is less than even moderate rates of anthropogenic N deposition for temperate or boreal forests. By contrast, for tropical forests, the atmospheric CO2increase is sufficient to induce large rates of carbon accumulation in plants and soil.

4.Application of the model at the global scale suggests large localized sinks for CO2in either tropical rain forests or in forested or grassland areas of Europe and North America where appreciable N deposition occurs. Overall, the model suggests a terrestrial sink owing to CO2fertilization and N deposition of about 0·2 Pmol C per year. About half of this is in the mid‐latitudes of the northern hemisphere and about half in the tropics.
On the relationship between the composition, morphology and function of leaves
Authors: Roderick M. L. , Berry S. L. , Saunders A. R. , Noble I. R.
Published: March 2003

1. It is common practice to express measurements of leaf composition and morphology using dry mass as a basis. Relationships established using those measurements are difficult to interpret because the leaves may have different liquid contents or fractional air space.

2. In a previous theoretical investigation, we showed that the liquid content of leaves was important and the following hypotheses were proposed: (1) the mass of nitrogen per unit mass of liquid is relatively constant within leaves and (2) the surface area to volume ratio of leaves is proportional to leaf liquid content. That investigation also proposed that fractional air spaces were important, because they confer plasticity in construction, with apparently minimal cost in terms of CO2 uptake. In this paper we use a set of comprehensive measurements to address the above hypotheses and to assess whether the fractional air space does vary in a consistent manner.

3. We found that the specific gravity of the non‐gaseous fraction in the leaves we measured was within the range ≈ 0·9–3·0 and increased with the fractional air space in a regular manner. Consequently, the specific gravity varied over a much smaller range (≈ 0·9–1·4). The specific gravity at high liquid contents approached unity but at low liquid contents it was variable.

4. The mass of nitrogen (N) per unit mass of liquid was found to be relatively constant (0·01 ± 0·003, n = 76).

5. The surface area to volume ratio was positively correlated with the liquid content (R2 = 0·87, n = 27).

6. The mass of carbon (C) per unit dry mass was relatively constant (0·49 ± 0·04, n = 76). Because N was a constant fraction of the liquid mass but C was a constant fraction of the dry mass, the N:C ratio was positively correlated with the liquid content (R2 = 0·76, n = 27).

7. A comparison with leaf measurements from several external databases confirm that the relationships described above are widely applicable.

8. It is concluded that the composition and morphology of leaves are linked and that leaf function is a consequence of that linkage. Both the liquids and air spaces are integral to leaf function and need to be considered in analysis of experimental results.
Comparing population response to contaminants between laboratory and field: an approach using Daphnia magna ephippial egg banks
Authors: Barata C. , Baird D. J. , Amat F. , Soares A. M. V. M.
Published: March 2003

1. The life‐history responses of one field and two laboratory populations of Daphnia magna were studied under exposure to cadmium and ethyl parathion to assess by how much the response to toxic chemicals of laboratory populations with low genetic diversity differs from the response of genetically diverse field populations.

2. The field population was represented by at least 50 unique clones hatched from resting eggs (ephippia) collected at the beginning of the growing season from a temporary water‐body located in the north‐east Mediterranean Spanish coast. The laboratory populations were clonal lines established from two geographically and genetically distinct genotypes, which differed in their tolerance to cadmium and ethyl parathion. Toxicant effects on the mean and the variance of life‐history responses of the laboratory and the field populations were determined. For the field population, toxicant effects on the components of variance of primary fitness traits were also studied.

3. In addition to lethal effects, exposure to cadmium had strong sub‐lethal effects on clutch size and age at first reproduction whereas ethyl parathion only affected juvenile survival. The results reported for life‐history responses showed that the field population had a similar or greater mean tolerance to cadmium and ethyl parathion than the laboratory populations, but the breadth of its tolerance distribution (measured as the coefficient of variation, CV) was higher. Furthermore in contrast with the field population, laboratory populations did not show increased phenotypic plasticity (measured as CV) under increasing toxicant exposure. A further analysis of the components of variability for life‐history responses of the field population showed that increases in phenotypic plasticity with exposure levels were explained by increased levels of genetic variability.

4. These results support the conclusion that as the tolerance of a field population is strongly influenced by genetic factors, the use of genetically homogeneous laboratory populations has limited relevance in predicting long‐term responses of field populations to toxic chemicals. However, this conclusion must remain tentative until further supporting evidence is obtained from this and other species.
Developmental plasticity in Painted Turtles, Chrysemys picta
Authors: Packard G. C. , Packard M. J.
Published: March 2003

1. The contents of newly constructed nests of Painted Turtles, Chrysemys picta, were manipulated by reciprocal transplant, so that each of several nests received a complement of eggs from each of several females. The eggs were recovered from nests after 8 weeks and allowed to complete incubation under standard conditions in the laboratory.

2. Live mass, dry mass and water content of carcasses, and dry mass of unused yolk, varied significantly among hatchlings from eggs that incubated in different nests. Indeed, hatchlings from different nests sometimes differed as much in size or physiological condition as animals from different clutches.

3. Stepwise linear regression indicated that size of hatchlings and water content of their carcasses were positively correlated with water exchanges by eggs whereas mass of the unused yolk was negatively correlated with water exchanges. Although the statistical procedure is only correlative, the findings accord well with results of laboratory studies documenting a relationship between uptake of water by eggs, metabolism and growth by embryos, and size and condition of hatchlings.

4. Developmental plasticity, coupled with variation in the physical environment within and among nests, probably accounts (minimally) for 19% of the variation in live mass of hatchlings in the field; 24% of the variation in dry mass of carcasses; 11% of the variation in hydration of carcasses; and 26% of the variation in dry mass of unused yolk. Such variation may impact survival by neonatal animals, and needs to be addressed explicitly by models for the evolution of life history in Painted Turtles.
Mortality risk of rapid growth in the spider Nephila clavipes
Authors: L. E. Higgins , M. A. Rankin
Published: March 2003

Female Nephila clavipes from univoltine populations have greatly reduced reproductive success if they grow slowly and reach maturity late in the growing season. Although such fitness costs are expected to select for rapid increases in mass, several authors have presented models and data describing physiological costs of rapidly increasing mass.

 In order to test the hypothesis that there are inherent costs of rapid growth (increasing mass), laboratory‐reared juveniles of the orb‐weaving spider Nephila clavipes were randomly assigned to receive daily feedings ranging from 2·5% to 23% of their initial mass.

 Spiders receiving higher amounts of food were more likely to die at or immediately before the next moulting cycle.

 These results indicate that there may be inherent physiological costs of rapidly increasing mass. In opportunistic feeders such as spiders that tend to gorge when prey are abundant, this could present a real cost to a common foraging strategy.
Phenotypic plasticity in reproductive traits: geographical variation in plasticity in a viviparous snake
Authors: R. A. Seigel , N. B. Ford
Published: March 2003

Previous experiments showed that Checkered Garter Snakes (Thamnophis marcianus) from south Texas, USA (an environment subject to high seasonal and annual variation in environmental conditions), demonstrated marked phenotypic plasticity in clutch size and clutch mass in response to experimental changes in prey availability.

 In this study, the extent of phenotypic plasticity in life‐history traits in Checkered Garter Snakes from south Texas was experimentally compared with a population of the same species from south‐eastern Arizona, where the environment may be more constant.

 Unlike results from south Texas, Checkered Garter Snakes from Arizona showed no significant phenotypic plasticity in clutch size, clutch mass or any other life‐history trait in response to changes in food availability, at least within the boundaries of our experimental conditions.

 The data indicate that the degree of phenotypic plasticity in life‐history traits differs among populations within the same species. However, these differences are subject to both adaptive and non‐adaptive explanations.
Laboratory screening of the juvenile responses of grassland species to warm temperature pulses and water deficits to predict invasiveness
Authors: T. A. White , Campbell B. D. , Kemp P. D.
Published: March 2003

Two laboratory screening experiments tested the juvenile‐phase responses of 14 C3 and 12 C4 grassland species to pulses of warm temperature and water deficits. The first experiment determined germination response in relation to duration of warm temperature exposure (30/20 °C day/night). The second experiment determined the desiccation tolerance of seedlings immediately following germination.

 The C4 species were more dependent on warm temperatures for germination than the C3 species. However, there was considerable variation within C3 and C4 types. In particular, Panicum dichotomiflorum was identified as the C4 species least dependent on warm temperatures, exhibiting > 50% of maximum germination in continuous cold (7 °C).

 The C3 species were generally more desiccation‐tolerant than the C4 species, but there were several exceptions. Trifolium repens (C3) was ranked as the least desiccation‐tolerant whereas Setaria geniculata (C4) was the eighth most tolerant species. Large‐seeded species were more desiccation‐tolerant than small‐seeded species.

 We suggest that poor desiccation tolerance contributes to the observed restriction of C4 grass invasion into productive grasslands of the wetter regions of New Zealand. On the basis of juvenile‐phase attributes, we ranked the C3 species as more invasive of these grasslands than the C4 species, and annuals as more invasive than perennials. Having invasive juvenile‐phase attributes is an advantageous adaptation for species that rely solely on regeneration from seed.
Population divergence in the plasticity of the response of Quercus coccifera to the light environment
Authors: L. Balaguer , Martínez‐Ferri E. , Valladares F. , Pérez‐Corona M. E. , Baquedano F. J. , Castillo F. J. , Manrique E.
Published: March 2003

Quercus coccifera, a slow‐growing, evergreen oak, grows in contrasting environments in the Mediterranean Basin. Habitat‐based selection may have promoted divergence between populations with respect to phenotypic plasticity and genetic variability.

 We tested the hypothesis that populations of the Q. coccifera originating from a rock outcrop, a continental garrigue formation and an oceanic forest would differ in their plastic response to light intensity. Plants from these populations were grown from acorns in a common garden at 100% and 20% full sunlight. Light response analysis was based on photochemical efficiency, xanthophyll pool, nutrient allocation, growth, crown architecture and light absorption.

 Light‐responsive characters ranged from the subcellular to the whole‐plant level. The greatest divergences between sun and shade phenotypes were observed in leaf size, leaf angle and leaf area ratio. However, plasticity in these traits depended on plant provenance.

 Regardless of the level of organization, populations were invariably ranked in the same order of plasticity when averaged over light‐responsive features, with plants originating from the rock outcrop showing the least plasticity and those from the forest the largest. The forest population also had the greatest genetic variability with respect to the isoperoxidase polymorphism.

Among populations, plants originating from the phosphorus‐deficient rock outcrop contained 30% more P per unit dry weight. Plants from the forest population had 5% more photoprotective xanthophylls, 30% larger total leaf area, with less lobed and larger leaves and a differential plasticity in leaf azimuth.

Differences among populations suggested ecotypic differentiation towards less phenotypic plasticity in the most homogeneous light environments. The ecological breadth of the species seemed to be derived not only from its tolerance of Mediterranean conditions but also from the specialization of its populations in contrasting habitats.
Achene mass variation in Ericameria nauseosus (Asteraceae) in relation to dispersal ability and seedling fitness
Authors: Meyer S. E. , Carlson S. L.
Published: March 2003

1.  Ericameria nauseosus (Asteraceae) is a highly variable shrub species of western North America, whose achene mass varies sevenfold among subspecies and populations. We examined trade‐offs between seedling fitness and dispersal ability by asking: does greater achene mass reduce dispersal ability, and is this potential disadvantage to large achenes compensated for by increased pappus investment? Does smaller achene mass reduce seedling fitness, and is this potential disadvantage to small achenes compensated for by increased relative growth rate (RGR)?

2. Dispersal ability was measured as fall rate in still air, while seedling fitness was measured as dry mass at two ages for 21 populations belonging to nine subspecies.

3. Fall rate was positively correlated with achene plume loading−1/2, but because of variation in pappus investment and geometry, both plume loading−1/2 and fall rate were only weakly positively correlated with achene mass. Relative pappus investment did not show a consistent increase with achene mass.

4. Seedling dry mass was strongly positively correlated with achene mass for 2‐week‐old seedlings grown without added nutrients. This correlation was significant but weak with added nutrients at 2 weeks, and by 4 weeks it was no longer significant. Seedling RGR was strongly negatively correlated with achene mass.

5. Achene mass variation was related to both seedling fitness and dispersal ability, but compensation was evident mainly as faster RGR in populations with small achenes.
Relationships between leaf lifespan and structural defences in a low‐nutrient, sclerophyll flora
Authors: Wright I. J. , Cannon K.
Published: March 2003

The spectrum between species with low leaf mass per area (LMA), short‐lived leaves and high photosynthetic rate to those with high LMA, long‐lived leaves and low photosynthetic rate is one of the major spectra of variation between plant species, and is of particular relevance to the ‘carbon‐gain strategy’ of plants.

 In this study the relationship between physical properties of leaves and their lifespan was quantified for 17 sclerophyllous species from a nutrient‐poor woodland in eastern Australia. Fracture properties of leaves (force of fracture, tissue toughness) and other leaf traits [LMA, thickness, dry‐matter content (DMC), leaf area] were measured for each species and evaluated as predictors of leaf lifespan in cross‐species and phylogenetic analyses, and for intercorrelation with one another.

 The LMA, mean force of fracture, leaf thickness and leaf area each explained approximately 30–40% of variation in leaf lifespan. Leaf toughness explained 25% of variation in leaf lifespan, and DMC 12%. Leaf toughness and DMC were correlated with each other, but not with leaf thickness. Leaf thickness and toughness were related closely to LMA, while DMC and LMA were only marginally correlated.

 Nutrients can be withdrawn prior to leaf death and redeployed elsewhere in the canopy when leaf death is initiated by a plant. However, when control is external to the plant these nutrients are lost. There may be advantages to increasing defence to give a high likelihood that the plant has control over the timing of leaf death.
Life‐history traits of Brown Trout vary with the size of small streams
Authors: Jonsson B. , Jonsson N. , Brodtkorb E. , Ingebrigtsen P.‐J.
Published: March 2003

Brown TroutSalmo truttaL. life‐history traits were studied in 17 coastal streams with mean annual water discharges ≤1 m3 s−1, and with anadromous and freshwater resident trout present in all streams.

 Mean smolt length and age were positively correlated with mean annual water discharge and latitude. The variation (CV) in smolt length and age was negatively correlated with water discharge. Mean length and age at maturity were also positively correlated with mean annual water discharge.

 Freshwater resident females were sparse (mean: 3·7%) but males were abundant in all the investigated populations (mean 48·9%). Mean body length at maturity of resident males increased with discharge in parallel to that of the anadromous males. Mean length at maturity increased with smolt length in anadromous males, but not females. Mean sea‐age at maturity in females, but not males, was negatively correlated with smolt age.

 It is concluded that several life‐history traits of Brown Trout are strongly influenced by habitat variables associated with the size of small nursery streams.
Seasonal variations in the net ecosystem CO2 exchange of a mature Amazonian transitional tropical forest (cerradão)
Authors: Vourlitis G. L. , Priante Filho N. , Hayashi M. M. S. , Nogueira J. De S. , Caseiro F. T. , Holanda Campelo J.
Published: March 2003

Tower‐based eddy covariance and measurements of the vertical CO2 concentration gradient within the canopy were used to quantify the seasonal variations in the net ecosystem CO2 exchange (NEE) of a 28–30 m tall transitional tropical forest (cerradão). The study was conducted near the city of Sinop, Mato Grosso, Brazil (11°24·75′ S; 55°19·50′ W), which is located in the ecotone of two major regional ecosystem types of South America (tropical rainforest and savanna).

 The NEE during the dry season (August–September) was in balance, but during the transition period between the dry and wet seasons (October–November) the cerradão stand became a net source of 50–150 mmol m−2 day−1 CO2 to the atmosphere. Measurements during the wet season (February, April) indicate that the forest was a net sink of between −55 and −102 mmol m−2 day−1.

 The NEE of the transitional tropical forest was more similar to that of tropical rainforest during the wet season, but during the dry season the NEE of the transitional forest was more similar to that reported for tropical savanna. The data suggest that seasonal variations in rainfall have important implications for the seasonal pattern of NEE in cerradão.