bluuebunny/crossref_metadata_2025_split huggingface dataset:
The integrated processing response of voles to fibre content of natural diets
Authors: Young Owl M. , Batzli G. O. 
Published: March 2003

1. Two species of voles were fed high fibre (barnyard grass) and low fibre (alfalfa) diets to test the integrated processing response (IPR) hypothesis. This hypothesis states that many herbivores are able to maintain their required intake of digestible nutrients and energy on diets with very different fibre content because of compensatory changes in intake of food, size of gastro‐intestinal (GI) tract, passage rates of fibre and absorptive capacity of the GI tract. 2. As predicted by the IPR hypothesis, each species of vole maintained a similar intake of digestible dry matter on the two different diets. Both species also had greater intake, larger GI size, shorter mean retention times and greater GI mass (an indicator of epithelial mass and absorptive capacity) when fed grass than when fed alfalfa. 3. The two species differed in that meadow voles, the more active species, had greater total intake and obtained a greater amount of digestible dry matter from either diet than did prairie voles. Meadow voles also consume more grass in the field than do prairie voles, and they digested grass better than did prairie voles. Prairie voles, which consume more dicots in the field, digested alfalfa better than did meadow voles. 4. Meadow voles had longer GI tracts, particularly small intestines, than did prairie voles, which may be linked to their greater ability to digest grass. However, meadow voles did not have larger caeca than prairie voles, even though caecal size increased on grass diets for both species. The GI size of prairie voles fed grass increased more than did the GI size of meadow voles, and this may have enabled prairie voles to utilize a grass diet, though they prefer to eat dicots. Greater selection of leaves, which have less fibre than stems, and longer mean retention times of food may account for better digestion of alfalfa by prairie voles.
Host plant effects on the genetic variation and correlations in the individual performance of the Gypsy Moth
Authors: LazareviĆ J. , PeriĆ‐Mataruga V. , IvanoviĆ J. , AndjelkoviĆ M. 
Published: March 2003

1.Quantitative genetic analysis of variation in host‐use ability was performed in an extremely polyphagous species – the Gypsy Moth. Various life‐history traits were investigated by applying a split‐family two‐environment experimental design, where 30 full‐sibling families were reared on oak and Locust Tree leaves.2.Feeding on Locust Tree leaves decreased preadult viability, prolonged development time, decreased pupal mass both in males and females, and decreased reproductive effort in females.3.The majority of broad‐sense heritabilities did not change across host plants.4.Significant expression of genetic variation in diet breadth was observed for development time and pupal mass both in males and females, but not for female reproductive effort traits. The heritabilities of plasticities were, on average, lower than heritabilities of the traits themselves.5.The majority of genetic correlations between the host plants were significantly positive. The only trade‐off was found between reciprocal value of reproductive index and the average mass of a fertilized egg within oak. This means that selection for the decrease in relative reproductive investment (under starvation during gradation) will be followed by laying larger eggs. Given that the Gypsy Moth has a cyclic population dynamics, this negative genetic correlation could have a role in maintaining genetic variability in this species.
Size dependence of reproductive allocation: the influence of resource availability, competition and genetic identity
Authors: Sugiyama S. , Bazzaz F. A. 
Published: March 2003

1.Resource availability, competition and genetic difference are among the main factors causing size variation in plant populations. These factors also have great effects on the variation in reproductive allocation. We examined the effects of soil nutrient availability, competition and genetic identity on the size dependency of reproductive allocation inAbutilon theophrastifamilies grown under different conditions of soil nutrient and conspecific competition.2.Soil nutrients, competition and genetic identity brought about a strong dependency of reproductive allocation on size. However, these factors differed in functional forms and signs of the size dependency.3.An allometric (log–log) regression between seed mass and vegetative mass fit the data better than a linear regression. The slopes of allometric regressions for each nutrient treatment were lower than 1·0. Therefore, there was a negative relationship between plant size and reproductive allocation. However, the slopes calculated over different nutrient treatments were greater than 1·0 (i.e. positive relationship between plant size and reproductive allocation). We suggest that these two reproductive allometries indicate two different biological relationships: the former represents a physiological trade‐off between resource acquisition and reproductive allocation within a plant and the latter represents an allometric response to soil nutrients.4.Genetic identity showed intrinsic effects on size dependency of reproductive allocation owing to trade‐off and not as a result of the allometric response to soil nutrients.5.Nutrient availability changed the slopes of the allometric regressions. An increase in nutrient availability alleviated the negative relationship between plant size and reproductive allocation.6.The slopes of the allometric regressions within nutrient treatments were significantly higher in competition treatments than in competition‐free treatments, although the slopes of the regressions over different nutrient levels did not differ between the two treatments. These results suggest that the effects of competition on reproductive allocation are owing to indirect effects of size difference on the allometric relationship rather than intrinsic effects.
Variation in bark thickness in a tropical forest community of Western Ghats in India
Authors: Hegde V. , Chandran M. D. S. , Gadgil M. 
Published: March 2003

1. We examined the relation between bark thickness and girth in a large sample of trees from evergreen and semi‐evergreen rain forest. 2. There is a significant tendency for bark thickness to increase with tree girth. Removing this tendency, we find a significant trend for species from more disturbed habitats to possess thicker bark. 3. Species from more disturbed habitats also have a greater propensity for secreting gums and resins. 4. Nine of the 29 species occurring in more than one habitat type and with a sample size of at least 11 individuals show a tendency for possession of a thicker bark by individuals in the more disturbed habitats. 5. We conclude that bark thickness and occurrence of gums and resins are physiognomic–structural attributes of value in characterizing tree communities created by different levels of disturbance.
Body temperature and insulation in diving Great Cormorants and European Shags
Authors: GRÉmillet D. , Tuschy I. , Kierspel M. 
Published: March 2003

1. Cormorants are typically considered as wettable diving birds with high thermoregulatory costs and are presumed to exert substantial predatory pressure on fish stocks. 2. The stomach temperatures of seven Great Cormorants and three European Shags were recorded during a total of 108 foraging trips undertaken near the Chausey Islands breeding colony (France). 3. Both species kept a constant body temperature during the dive series which lasted up to 158 min and were conducted in 12°C water. Consequently, assuming that heat loss to the water is equal to heat production in diving Great Cormorants, the minimal insulating plumage air volume was calculated to be 0·371 × 10–3 m3 (corresponding to a 1·62‐mm air layer) in males and 0·347 × 10–3 m3 (corresponding to a 1·90‐mm air layer) in females. 4. Furthermore, it is shown that plumage air volume and dive depth are the major factors influencing heat flux to the water and that the energetics of diving Great Cormorants may also vary substantially according to fat layer thickness, water temperature and body temperature. Swim speed plays only a minor role. 5. Considering these results, it is postulated that Great Cormorants may have optimized plumage air volume so as to minimize both mechanical costs (upthrust) and thermoregulatory costs of swimming in cold, shallow water. 6. Finally, body temperature patterns recorded in different cormorant species while diving are compared.
Ecological factors influencing the occurrence of ‘flash marks’ in wading birds
Authors: DE L. Brooke M. 
Published: March 2003

1. Although the plumage of birds is important for flight and thermoregulation, it is also employed in inter‐ and intraspecific communication. The role in communication of particular plumage features can be studied by experiment or, as here, by correlational analysis. 2. The study was carried out on the 210 species of wading birds, such as plovers, sandpipers, thick‐knees and allies, that are placed within the traditional order Charadriiformes. 3. Species differ in the location and extent of ‘flash marks’, patches of white on the plumage that are typically conspicuous when the bird flies. These patches occur, in various permutations in different species, on the wing (primaries, secondaries, coverts), back, rump and tail. 4. Within a phylogenetic framework, it was asked which of several broad ecological variables (migration, habitat choice, feeding technique, propensity to flock) were correlated with the occurrence of flash marks. Only flocking correlated significantly. In particular, taxa that flock have flashier backs and coverts than their non‐flocking relatives. 5. Three non‐exclusive explanations for this correlation are: (i) individuals that take flight to avoid a predator may benefit from signalling their take‐off to flock mates which themselves then take flight; (ii) flash marks could enhance the confusion effect within flocks, making it more difficult for a predator to single out an individual; and (iii) flash marks may facilitate co‐ordinated flight within flocks.
Effects of floral morphology and display on outcrossing in Blue Columbine, Aquilegia caerulea (Ranunculaceae)
Authors: Brunet J. , Eckert C. G. 
Published: March 2003

1. The effect of variation in floral morphology and display on the level of outcrossing was investigated in a Rocky Mountain population of the self‐compatible, protandrous, perennial herb, Aquilegia caerulea. ANOVA revealed substantial variation among 36 plants in floral traits including herkogamy (CV = 35%), protandry (23%), pollen production (12%), flower size (8%), the daily number of flowers in male phase (58%) and autofertility, seed production in the absence of pollinators (192%). 2. Whether this floral variation affected the outcrossing rates of individual plants was assessed using both a categorical analysis, in which outcrossing rates were estimated separately for groups of plants that differed with respect to floral features, and a correlation analysis involving outcrossing rates estimated for individual plants from large progeny arrays (n≥ 40). Both analyses indicated significant positive correlations between the outcrossing rate and herkogamy (r = + 0·71) and protandry (+ 0·54), negative correlations with the number of flowers in male phase during each day of female phase (– 0·42) and autofertility (– 0·36), but no correlation with flower size or pollen production. 3. Partial correlation indicated that both herkogamy and dichogamy, although weakly intercorrelated, were positively correlated with the outcrossing rate and that these effects were only partly mediated by their negative correlation with autofertility. 4. The extent to which floral features and the outcrossing rate covaried across the flowering sequence within plants was also examined in this study. As expected for a plant with strong protandry and sequential blooming, the number of flowers in male phase decreased strongly with flowering sequence position. However, categorical analysis did not support the prediction that the first flowers to open on an inflorescence outcrossed at a lower rate than later‐opening flowers. 5. These results suggest that self‐fertilization in A. caerulea is the result of all three major modes: autonomous and facilitated autogamy as well as geitonogamy. Although the geitonogamous component of selfing cannot be selected for directly, autogamy may be selected if it provides reproductive assurance.
A field fumigation system for elevated carbon dioxide exposure in chaparral shrubs
Authors: Roberts S. W. , Oechel W. C. , Bryant P. J. , Hastings S. J. , Major J. , Nosov V. 
Published: March 2003

1. Modifications and improvements in the hardware and software of a free‐air CO2 enrichment (FACE) system are described. The modifications were undertaken to minimize the amount of structure required and to improve software control of CO2 set points. 2. A new low‐cost CO2 flow controller which provides increased reliability is described. 3. Analysis of system performance during a 79‐day evaluation period of operation (13 h day–1) showed that for 1 min averages, the system is capable of maintaining a 550 p.p.m. ± 10% CO2 set point during 78% of the operating time and a 550 p.p.m. ± 20% set point during 95% of the operating time. Ten‐minute averages were within ± 10% and 20% during 87% and 96% of the operating time, respectively. 4. Continuous measurements of the spatial variation in CO2 concentration inside the FACE ring over an 18‐day period showed that of the total 16‐m diameter treatment area, the central 11‐m diameter portion remains within the 550 p.p.m. ± 10% set point. 5. Daily course gas‐exchange measurements in matched individuals of the chaparral shrub Adenostoma fasciculatum just prior to and following a 6‐week fumigation period at 550 p.p.m. CO2 in the FACE treatment ring showed the FACE plants with reduced photosynthetic rates and higher (less stressful) water potentials compared with control A. fasciculatum plants measured at the same times and conditions, indicating the responsiveness of this species to elevated CO2 conditions.
Maternal and ambient environmental effects of light on germination in Plantago lanceolata: correlated responses to selection on leaf length
Authors: Van Hinsberg A. 
Published: March 2003

1. Seeds from artificial selection lines were exposed to different maternal and ambient conditions, simulating sunlight and vegetation shade. 2. Lines selected for longer leaves also produced larger seeds, indicating a positive genetic correlation between leaf length and seed size. 3. Light conditions during maturation had no large effect on seed size. 4. Seed germination was reduced by a low ratio of red to far‐red light (R/FR ratio) in the ambient environment. 5. Seeds maturated under simulated vegetation shade germinated less readily and were more inhibited by a low ambient R/FR ratio than seeds maturated under full sunlight or R/FR‐neutral shade. Thus, low R/FR‐ratios in the maternal and ambient environment operated synergistically. 6. Large genotypic variation in the germination responses to both maternal and ambient light conditions was found among and within selection lines, indicating that such responses might have the potential to evolve in response to natural selection. 7. Artificial selection for leaf length had affected seed germination characteristics but correlated responses and thus genetic correlations largely depended on light conditions in the selective environment. Selection for longer leaves under a low R/FR ratio increased seed dormancy and plasticity of germination in response to the R/FR ratio. However, in the opposite selective environment selection for longer leaves reduced seed dormancy and plasticity to the R/FR ratio. It is argued that leaf length and seed germination characteristics are somehow linked by shared physiological mechanisms, which may facilitate concerted changes in shade avoidance responses.
The influence of the nutritional content of the adult male diet on testis mass, body condition and courtship vigour in a Hawaiian Drosophila
Authors: Droney D. C. 
Published: March 2003

1. The effects of the nutritional quality of the adult diet (primarily protein content) on testis mass, body condition and courtship vigour were studied in a Hawaiian Drosophila, D. grimshawi, a lek‐forming species under strong sexual selection. The primary goals of this study were to determine whether there is a trade‐off between investment in reproductive and somatic tissues, and to examine whether this trade‐off is influenced by quality of the adult diet. 2. Quality of the adult diet had a major influence on male body condition, courtship vigour and testis mass, but males varied in their investment patterns even within diet treatment. 3. Body condition, a measure of phenotypic quality, was significantly related to how much males invested in testis and body tissues, but the nature of the relationships differed between males fed high‐ or low‐quality diets. 4. Paragonia volume was significantly smaller for adult males fed low‐quality diets than for males fed high‐quality diets. Nutrient‐deficient diets apparently forced males to trade off investment in testes and body condition, and in body condition and courtship vigour, but nutrient‐rich diets did not result in severe trade‐offs. 5. Collectively, the results suggest that fluctuation in adult diet quality of male D. grimshawi might influence male reproductive quality in ways that might limit female reproductive output and/or be a factor for female choice in this species.
Effects of enhanced UV‐B radiation on production‐related properties of a Sphagnum fuscum dominated subarctic bog
Authors: Gehrke C. 
Published: March 2003

1. The aim of the study was to investigate effects of enhanced UV‐B radiation on the balance between biomass production and decay in an ombrotrophic bog which is dominated by one species of Sphagnum (S. fuscum). This paper concerns production. 2. Enhanced UV‐B radiation (simulating 15% ozone depletion under clear sky conditions) was applied by means of fluorescent tubes during two growing seasons. 3. In S. fuscum, shoot density, mass relations and length increment over time were measured and productivity was estimated. Pigment concentration, rates of dark respiration and maximum net photosynthesis were recorded. 4.
Sphagnum fuscum productivity was not changed by enhanced UV‐B radiation while properties determining production were highly influenced although in opposite directions. 5. Height increment was decreased by 20% in the first growing season and by 31% in the second growing season under enhanced UV‐B radiation. After two growing seasons spatial shoot density was decreased by 8% by enhanced UV‐B radiation. The shoots became stunted as capitulum dry mass and stem dry mass per unit length were increased by 21 and 17%, respectively, under enhanced UV‐B radiation. 6. Dark respiration was significantly decreased by 31% after growth under enhanced UV‐B radiation. 7. The UV‐B induced change in shoot biometry together with the reduced spatial shoot density involve potential long‐term effects on peat structure with possible feedback on productivity, decomposition and the strength of the system as a carbon sink.
Does photosynthetic acclimation to elevated CO2 increase photosynthetic nitrogen‐use efficiency? A study of three native UK grassland species in open‐top chambers
Authors: Davey P. A. , Parsons A. J. , Atkinson L. , Wadge K. , Long S. P. 
Published: March 2003

1. The photosynthetic response to elevated CO2 and nutrient stress was investigated in Agrostis capillaris, Lolium perenne and Trifolium repens grown in an open‐top chamber facility for 2 years under two nutrient regimes. Acclimation was evaluated by measuring the response of light‐saturated photosynthesis to changes in the substomatal CO2 concentration. 2. Growth at elevated CO2 resulted in reductions in apparent Rubisco activity in vivo in all three species, which were associated with reductions of total leaf nitrogen content on a unit area basis for A. capillaris and L. perenne. Despite this acclimation, photosynthesis was significantly higher at elevated CO2 for T. repens and A. capillaris, the latter exhibiting the greatest increase of carbon uptake at the lowest nutrient supply. 3. The photosynthetic nitrogen‐use efficiency (the rate of carbon assimilation per unit leaf nitrogen) increased at elevated CO2, not purely owing to higher values of photosynthesis at elevated CO2, but also as a result of lower leaf nitrogen contents. 4. Contrary to most previous studies, this investigation indicates that elevated CO2 can stimulate photosynthesis under a severely limited nutrient supply. Changes in photosynthetic nitrogen‐use efficiency may be a critical determinant of competition within low nutrient ecosystems and low input agricultural systems.
Sex allocation and larval competition in a superparasitizing solitary egg parasitoid: competing strategies for an optimal sex ratio
Authors: Van Baaren J. , Landry B. L. , Boivin G. 
Published: March 2003

1. Parasitic Hymenoptera reproduce by arrhenotokous parthenogenesis, and females of these species are able to control their progeny sex ratios. In structured populations of parasitic Hymenoptera, primary sex ratios are often highly biased toward females. However, sex ratio can be adjusted to the quality of encountered patches or hosts or be modified by differential developmental mortality. 2. In this paper, the effects were evaluated of the quality of encountered hosts and developmental mortality on the sex ratio in Anaphes victus, a solitary egg parasitoid whose first instar larvae present a sexual dimorphism and where superparasitism is regulated by larval fights between first instar larvae. 3. The results showed that a female‐biased sex ratio is allocated to unparasitized hosts. In the presence of parasitized hosts, the second (superparasitizing) female produced a significantly higher sex ratio than the first female but the tertiary sex ratio (sex ratio at emergence) was not significantly different from the sex ratio produced with unparasitized hosts. The increase in the primary sex ratio produced by the second female was mostly compensated by the higher mortality of male larvae.
Strategic sperm allocation in the Small White butterfly Pieris rapae (Lepidoptera: Pieridae)
Authors: Wedell N. , Cook P. A. 
Published: March 2003

1. In species where females mate multiply, it is important for males to recuperate quickly in order to maximize their fertilization success. Butterflies produce a spermatophore at mating containing accessory secretions and sperm of two types: a large number of non‐fertile ‘apyrene’ sperm and fewer fertile ‘eupyrene’ sperm. Many butterfly species eclose with most nutrients for reproduction already present. Males must therefore decide how to allocate resources to the various spermatophore components at any given mating. 2. Recovery rates of apyrene and eupyrene sperm number and spermatophore size was studied in the polyandrous Small White butterfly Pieris rapae. The mass of the first spermatophore increases with time since eclosion, as does the number of both types of sperm. Similarly, on a male's second mating, both the mass of the spermatophore and the number of sperm increases with time since the first mating. 3. However, the rate of increase in eupyrene sperm numbers is higher after the first mating. The difference in rate of increase may be the result of different probabilities of virgin and non‐virgin males obtaining future matings. 4. Males have a sperm storage organ, the duplex, in which they retain sperm after their first mating. This ensures that high sperm numbers are available for their second mating, even when remating only 1 h later. Thus, males do not ejaculate all available sperm on any given mating, and seem to have different strategies on their first and second matings. 5. It can be argued that Small White butterfly males allocate sperm strategically according to the probability of obtaining subsequent matings, and the level of sperm competition.