bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ciliate populations in temporary freshwater ponds: seasonal dynamics and influential factors
Authors: Andrushchyshyn Oksana , Magnusson A. Katarina , Williams D. Dudley 
Published: March 2003

SUMMARY 1. The ciliate populations of two temporary ponds in southern Ontario were studied throughout their aquatic phases in 2001. Pond I (∼1 ha) held water for 98 days, whereas Pond II (∼0.25 ha) held water for 34 days. Populations were assessed both within the ponds themselves and within a series of enclosures in which invertebrate predator pressure was manipulated.2. In the natural pond water, total ciliate abundance in Pond II rose rapidly from day 1 increasing two orders of magnitude by day 7. In contrast, total abundance in Pond I began at the same level as in Pond II but increased much more slowly, reached a plateau of around 500 individuals L−1, and increased again late in the hydroperiod.3. Despite being only 500 m apart, the two ponds were fairly dissimilar in terms of their species richness and species composition. Pond I contained 50 species compared with 70 species for Pond II, with only 24 species shared. Additional species occurred within the enclosures raising the total species richness to 145 species; 88 from Pond I, 104 from Pond II, with 47 species (30%) in common. Pond II contained more mid‐sized ciliates (50–200 μm), whereas Pond I was dominated by smaller ciliates, especially in mid‐May and early June. In Pond I, cumulative species richness throughout the hydroperiod was highest in the predator addition enclosures (65 ± 4 species), followed by the partial‐predator exclusion enclosures (50 ± 4). Lowest species richness was found in the control enclosures (39 ± 2) and in the pondwater controls (39 ± 0). Differences between the ciliates in the natural pond water and the enclosures appeared to be related to a greater concentration of phytoplankton within the enclosures (perhaps resulting from extensive growth of duckweed, Lemna, outside), and higher densities of zooplankters in the pond.4. The physicochemical environment influenced species richness, total abundance and the number of rare species (27 in Pond II versus 13 in Pond I). Variation in ciliate abundance in Pond I could be explained by the number of days after filling (39%) and enclosure treatment (23%). These two parameters also explained 72% of the variation in species richness in Pond I (46 and 26%, respectively). Sixty‐five per cent of the variation in abundance in Pond II could be explained by the measured parameters: number of days after filling 27%, pH 19%, and nitrate levels 12%. Fifty‐two per cent of the variation in species richness was explained by the environmental parameters, of which pH was the most influential. Species succession was a strong feature of both ponds and its relationship to environmental variables and the presence of other organisms is discussed.5. Addition of invertebrate predators resulted in higher abundance and higher species richness for a limited time period in one of the ponds – suggesting that differences in foodweb dynamics may influence ciliate community composition.
Effects of a fertility‐reducing baculovirus on sperm numbers and sizes in the Indian Meal Moth, Plodia interpunctella
Authors: Sait S. M. , Gage M. J. G. , Cook P. A. 
Published: March 2003

1. A dose‐dependent decrease in male fertility occurs in the Indian Meal Moth, Plodia interpunctella, when sub‐lethally infected with granulovirus during the larval stage. 2. Here, the causes for this decline are investigated by examining eupyrene and apyrene sperm numbers and sizes produced by males across four levels of viral challenge. 3. The results could not explain how reduced male fertility is caused in this host–pathogen interaction. While a reduction in both eupyrene and apyrene sperm numbers from all virus‐treated males was found, this was not significant and neither was there a difference in sperm lengths across the four treatments. There were also no differences in the variances of sperm numbers or lengths between the doses, and no associations between sperm numbers or lengths and body size were found. 4. A significant correlation between eupyrene and apyrene numbers was found, but this was independent of dose. Significant between‐male variance in apyrene sperm lengths was found, indicating that individual males differ in the range of apyrene sperm sizes they produce. 5. It is suggested that further intracellular and behavioural study is needed to identify the causes of the granulovirus‐induced reduction in fertility of P. interpunctella.
The significance of differences in the mechanisms of photosynthetic acclimation to light, nitrogen and CO2 for return on investment in leaves
Authors: Sims D. A. , Seemann J. R. , Luo Y. 
Published: March 2003

1. We report changes in photosynthetic capacity of leaves developed in varying photon flux density (PFD), nitrogen supply and CO2 concentration. We determined the relative effect of these environmental factors on photosynthetic capacity per unit leaf volume as well as the volume of tissue per unit leaf area. We calculated resource‐use efficiencies from the photosynthetic capacities and measurements of leaf dry mass, carbohydrates and nitrogen content. 2. There were clear differences between the mechanisms of photosynthetic acclimation to PFD, nitrogen supply and CO2. PFD primarily affected volume of tissue per unit area whereas nitrogen supply primarily affected photosynthetic capacity per unit volume. CO2 concentration affected both of these parameters and interacted strongly with the PFD and nitrogen treatments. 3. Photosynthetic capacity per unit carbon invested in leaves increased in the low PFD, high nitrogen and low CO2 treatments. Photosynthetic capacity per unit nitrogen was significantly affected only by nitrogen supply. 4. The responses to low PFD and low nitrogen appear to function to increase the efficiency of utilization of the limiting resource. However, the responses to elevated CO2 in the high PFD and high nitrogen treatments suggest that high CO2 can result in a situation where growth is not limited by either carbon or nitrogen supply. Limitation of growth at elevated CO2 appears to result from internal plant factors that limit utilization of carbohydrates at sinks and/or transport of carbohydrates to sinks.
Responses to elevated temperature and CO2 in the perennial grass Agrostis curtisii in relation to population origin
Authors: Norton L. R. , Firbank L. G. , Gray A. J. , Watkinson A. R. 
Published: March 2003

1. Evolutionary responses to climate change will depend on the presence of heritable variation within species populations for traits that increase fitness under the changing conditions. Patterns of ecotypic differentiation in relation to latitude in some species suggest that such variation exists in relation to temperature responses. Response to elevated CO2, whether heritable or not, is not expected to be related to latitudinal or climatic differences within temperate regions. 2. To test these ideas, seeds were collected from 10 populations of the outbreeding perennial grass Agrostis curtisii across its range in Europe from south Wales to Portugal. Plants were grown under ambient and elevated temperature and CO2 conditions, in a factorial design, in solardomes; two half sibs from each population were planted in separate pots in each of the two replicate domes with each combination of treatments. One half sib was harvested at the end of the first summer, the second at the end of the second summer. 3. Survival was uniformly high and flowering uniformly low across treatments and populations. 4. Responses to temperature and CO2 treatments varied over time for almost all populations. Treatment effects were not significant on plants harvested in year 1, although there was a trend towards higher shoot biomass under the elevated temperature and CO2 treatment. In year 2 shoot biomass was significantly higher under the elevated temperature treatment across all populations and there was a strong trend towards decreased biomass under elevated CO2. 5. There were no significant correlations of plant response to either CO2 or temperature with climate at origin. 6. These results warn of the dangers of extrapolating evolutionary plant responses to CO2 from short‐term experiments.
Aerobic performance does not affect social rank in female Red Jungle Fowl
Authors: CHAPPELL M. A. , ZUK M. , JOHNSEN T. S. 
Published: March 2003

1. Exercise capacity ultimately constrains behaviour, and therefore may influence social interactions. The hypothesis was tested that individual differences in maximal rates of oxygen consumption (V·O2max) – a primary determinant of sustainable exercise capacity – affect dominance hierarchies in experimental all‐female flocks of the highly social Red Jungle Fowl (Gallus gallus). It was also examined whether social rank could in turn influence V·O2max (which is quite plastic in most vertebrates), and whether these relationships were influenced by a common and relatively benign parasite, the intestinal nematode Ascaridia galli. 2. Substantial between‐individual variation was found in V·O2max that was significantly repeatable over time, but there was no indication that V·O2max was affected by A. galli infection. Stable social hierarchies were quickly established in 26 of 28 experimental flocks (each contained three females previously isolated from each other). Infection status affected social rank, but there was no consistent pattern between rank and infection. 3. No indication was found that individual differences in V·O2max either predicted the social rank in newly formed flocks, or were affected by social status in established flocks.
Seedling survival of Mediterranean shrubland species in relation to root:shoot ratio, seed size and water and nitrogen use
Authors: LLORET F. , CASANOVAS C. , PEÑUELAS J. 
Published: March 2003

1. We hypothesized that in Mediterranean plant communities seedling survival of different species during the drought period would be related to their ability to use below‐ground resources, particularly water and nitrogen. 2. For 5 years we studied under field conditions the summer seedling survival of 11 dominant species of a Spanish Mediterranean shrubland. We related seedling survival of the different species to their seed size and root allocation estimated as the slope of the function root biomass vs log shoot biomass. We used δ13C for the estimation of water‐use efficiency and δ15N and nitrogen concentration to determine the sources of nitrogen utilized. We correlated these variables with root allocation. 3. Seedling survival of the different species was positively correlated with root allocation and seed size. Root allocation was also positively correlated with seed size. δ15N and nitrogen concentration were also positively correlated with root allocation, but δ13C was not. 4. Under the relatively moist conditions occurring during summer 1996, higher root allocation was associated with the use of nitrogen from more nitrogen saturated microsites.
Photosynthesis and stomatal conductance of mature canopy Oak (Quercus robur) and Sycamore (Acer pseudoplatanus) trees throughout the growing season
Authors: Morecroft M. D. , Roberts J. M. 
Published: March 2003

1. Gas exchange is strongly seasonal in temperate deciduous forests; however, virtually no studies have described measurements made at the leaf scale through the whole growing season. This level of detail is important to understanding processes as substantial differences may occur within the canopy between species and between sun and shade leaves. 2. Gas exchange was measured weekly throughout the growing season in leaves of Oak (Quercus robur) and Sycamore (Acer pseudoplatanus) trees at Wytham Woods, UK. In Q. robur sun, shade and intermediate leaves were sampled on each occasion. 3.
Acer pseudoplatanus came into leaf before Q. robur and commenced net assimilation (A) earlier. Maximum irradiance saturated photosynthetic rates (Amax) in Q. robur were reached approximately 50 days after budburst and were maintained until approximately 20 days before abscission. Acer pseudoplatanus lost its leaves before Q. robur in the autumn and showed no seasonal trend in Amax. The lag between budburst and attainment of maximum photosynthetic rate in Q. robur was substantial and represented a quarter of the potential growing season. 4.
A
max of A. pseudoplatanus (3·5 μmol m–2 s–1) sun leaves was substantially lower than that of Q. robur (10·4 μmol m–2 s–1) despite A. pseudoplatanus being a fast‐growing species. The earlier flushing of A. pseudoplatanus leaves in the spring could not completely compensate for this. It is likely that other variables, such as total leaf area, are responsible for the high growth rate of A. pseudoplatanus, rather than high photosynthetic rates. 5. Shade leaves of Q. robur had lower Amax and mean A than sun leaves; their quantum efficiency was also lower. Consistent with this, sun leaves had a higher nitrogen content per unit area, resulting from a lower specific leaf area (SLA). 6. Week to week variations in solar radiation influenced A; this could be described by a non‐rectangular hyperbola. Stomatal conductance (gs) decreased in conditions of high vapour pressure deficit (VPD). However, this did not decrease A as high VPD was associated with high solar radiation and the stimulation of photosynthesis caused by high photosynthetic photon flux density (PPFD) more than compensated for the reduction by VPD.
The functional relationship between peak spring floods and survival and growth of juvenile Atlantic Salmon (Salmo salar) and Brown Trout (Salmo trutta)
Authors: Jensen A. J. , Johnsen B. O. 
Published: March 2003

1.The effects of high spring floods on survival and growth of juvenile Atlantic Salmon,Salmo salar,and Brown Trout,Salmo trutta, are explored, using data from a long‐term study in the River Saltdalselv, northern Norway. The flow regime in this river is typical for northern rivers.2.There was considerable variation in year class strength of both species.3.Mortality of Atlantic Salmon increased significantly in years with high discharge during the alevin stage as well as the first week after emergence. High discharge during the egg stage and more than 1 week after emergence seemed to be of minor importance. Water temperature at emergence was rather high (average 10·5 °C) and did not significantly affect year class strength.4.Brown Trout emerged earlier than Atlantic Salmon at an average water temperature of 8·2 °C. Highest mortality was observed in years with low water temperatures at emergence as well as high discharge during the alevin stage.5.For 1‐year‐old fish or older, the size of the spring peak flood did not influence mortality significantly.6.Growth of Atlantic Salmon parr was diminished in years with a high peak spring flood. A similar effect on Brown Trout was not detected.
Influence of leaf chemistry of Lotus corniculatus (Fabaceae) on larval development of Polyommatus icarus (Lepidoptera, Lycaenidae): effects of elevated CO2 and plant genotype
Authors: Goverde M. , Bazin A. , Shykoff J. A. , Erhardt A. 
Published: March 2003

1. Four Lotus corniculatus genotypes differing in cyanoglycoside and condensed tannin concentrations were grown in either low (350 ppm) or high (700 ppm) atmospheric CO2 environments. Larval performance, consumption and conversion efficiency of Polyommatus icarus feeding on this plant material were measured. 2. Plants grown under elevated CO2 contained less cyanoglycosides, more condensed tannins and more starch than control plants. However, water concentration, nitrogen and protein as well as nitrogen concentration in relation to carbon concentration did not differ between CO2 treatments. 3. The four genotypes differed significantly in condensed tannins, cyanoglucoside, leaf water and leaf nitrogen but no genotype–CO2 interaction was detected, except for total phenolics and condensed tannins in which two plant genotypes showed stronger increases under elevated CO2 than the other two. 4. Larvae of P. icarus consumed more plant material and used and converted it more efficiently from plants grown at high atmospheric CO2. 5. Larvae developed significantly faster and were significantly heavier when fed plant material grown under elevated CO2. The observed difference in mass disappeared in the pupal and adult stages. However, lipid concentration of adults from the elevated CO2 treatment was marginally significantly higher than of controls. 6. It is concluded that the higher carbohydrate concentration of L. corniculatus plants grown at elevated CO2 renders leaves more suitable and better digestible to P. icarus. Furthermore, differences in allelochemicals might influence the palatability of L. corniculatus leaves for this specialist on Fabaceae.
Partitioning variance in a physiological trait: desiccation resistance in keratin beetles (Coleoptera, Trogidae)
Authors: Chown S. L. , Le Lagadec M. D. , Scholtz C. H. 
Published: March 2003

1.Although variation in physiological traits forms the substance of evolutionary physiology, the way that this variation is partitioned among different hierarchical levels (e.g. population, species, genus) is not well known.2.In this study variance partitioning is examined in body size, water content, lipid content, rate of water loss, maximum tolerable water loss and survival time at four levels (individual, population, species, genus) in southern African keratin beetles.3.It is found that most variance in body size, and the physiological traits that are strongly influenced by body size (water and lipid content, maximum tolerable water loss, rate of water loss), is partitioned at the generic level (50–70%), then at the species level (20–50%) and finally at the population (1–9%) and individual (2–18%) levels.4.On the other hand, variance in survival time, and variance in rate of maximum water loss once the effects of body size have been taken into account, are partitioned mostly at the species level (40–70%), whereas maximum tolerable water loss and lipid and water content show greatest variance at the individual level (63–75%). This is largely a consequence of differences in the extent of scaling of these traits.5.The results suggest that where possible the effects of phylogeny should be controlled for when examining desiccation resistance in insects using comparative methods, but that confidence in conclusions from previous studies, which have used mass‐specific data, is not unwarranted.
Flight muscle atrophy and predation risk in breeding birds
Authors: Veasey J. S. , Houston D. C. , Metcalfe N. B. 
Published: March 2003

Abstract1. The speed with which small birds can get airborne is critical to the effectiveness of their escape response when attacked by a predator. However, take‐off ability is likely to be affected by physiological changes occurring as a result of egg formation.2. To investigate whether reduced take‐off velocity is a cost of reproduction, the physiological costs of egg production in the Zebra Finch (Taeniopygia guttata) were experimentally manipulated by varying both the number of eggs a female laid and the quality of her prelaying diet. The effect of changes in postlaying flight muscle condition and body mass upon alarmed flight take‐off velocity (a measure of escape‐ability in birds) was subsequently measured.3. Changes in muscle condition were found to correlate positively with changes in various measures of flight velocity: treatments that caused the greatest declines in muscle condition during egg‐laying were associated with the greatest declines in flight performance over this period. In contrast, breeding attempts that caused the smallest declines in muscle condition were associated with improvements in flight performance (i.e. birds flew faster at the end of laying than at the start).4. These effects were independent of changes in body mass, and occurred postlaying, suggesting that the cost of egg production lies primarily in the formation of the eggs, rather than in carrying them as other studies had suggested. The observed trade‐off between muscle loss resulting from egg production and escape ability could have important implications for the evolution of optimal clutch size in birds.
Biological diversity and probability of local extinction of ecosystems
Authors: Nijs I. , Impens I. 
Published: March 2003

Abstract1. With a mathematical model, we demonstrate that two principle components of biological diversity have antagonistic effects on the probability of ecosystem functioning (i.e. on ecosystem reliability, sensuNaeem 1998). Increasing the number of functionally analogous species in the system is shown to enhance reliability, while increasing the number of functions or processes which these species support (functional diversity) has a negative influence.2. Probability of functioning was calculated from the likelihood that essential ecosystem functions are lost, which was based on the probability of local extinction of the species that support these functions.3. A third component of diversity, heterogeneity among extinction probabilities of different species, enhanced probability of ecosystem functioning for species belonging to the same functional group, but only in species‐poor systems. In contrast, heterogeneity among species of different functional groups drastically reduced probability of ecosystem functioning and this reduction was more pronounced when more groups were present.4. The model further predicts an asymptotic relationship between number of functionally analogous species and probability of functioning, rather than a linear or complex one. In case the species are very prone to extinction, saturation occurs at higher species numbers, which indicates there is less species redundancy in vulnerable systems.
Immune defence reaction in bumble‐bee workers after a previous challenge and parasitic coinfection
Authors: Allander K. , Schmid‐Hempel P. 
Published: March 2003

Abstract

A successful immune response requires the functioning of a range of physiological mechanisms and is therefore supposed to be costly in terms of limited resources that could be used otherwise, such as energy or nutrients. Because immunity is costly, immune defence should be reduced if appropriate multiple immunogenic challenges are present.
The working hypothesis that multiple challenges will reduce the immune system’s capacity to respond is adopted. An existing infection by yet another parasite could also further reduce the strength of the immune response, since limited resources have to be divided among the different challenges.
The bumble‐bee, Bombus terrestris L., and its parasites are used as a model system to study (1) whether the melanization response towards an antigen is reduced or increased after a preceding challenge (‘depletion/stimulation’); (2) if depletion occurs, how long it takes to mount a full defence response against the second challenge; and (3) whether the coinfection by another parasite reduces or increases the immune defence system’s capacity to respond. A standard technique was used where two novel antigens (nylon filaments of different sizes and time intervals) were implanted into the haemocoel of individual workers. Controls were individuals implanted with a single fixed sized implant. A gut parasite, the trypanosome Crithidia bombi, was used for coinfections.
Size of the implant had no effect on the melanization response as well as time between primary and secondary implant. Primary and secondary implants differed from the controls. In particular, the primary implant was melanized more intensively than the controls and secondary, respectively. Furthermore, a coinfection by C. bombi had no effect on the encapsulation response.
The results suggest that no general depletion of the encapsulation system occurs under the conditions of our experiment and that a similar immune response (melanization) independent on the magnitude of the challenge, occurs. However, there seems to be a depletion effect on the secondary implant. Furthermore, the dynamics of two different parasites seem to run independently as far as within‐host interactions are concerned.