bluuebunny/crossref_metadata_2025_split huggingface dataset:
Does reproductive investment change with age in tsetse flies, Glossina morsitans morsitans (Diptera: Glossinidae)?
Authors: Langley P. A. , Clutton‐Brock T. H. 
Published: March 2003

1. Viviparous insects such as tsetse (Glossina spp.) provide unusual opportunities to compare age‐related changes in the proportion of maternal resources transferred to offspring. 2. In laboratory populations of Glossina morsitans morsitans the survival of females was high for the first 60 days of adult life but declined rapidly thereafter. 3. Average longevity did not differ significantly between mated and unmated females (93·6 and 90 days, respectively). 4. Nutritional state in terms of fat content and residual dry mass did not decline with adult female age. 5. The fecundity of mated females was constant for the first 60 days of adult life and declined only slightly thereafter. 6. Offspring size did not change towards the end of the adult female lifespan and there was no evidence of an increase in the allocation of resources to reproduction in older females. 7. Results contrast with those obtained recently for vertebrates and may indicate that age‐related changes in offspring size in Glossina are not adaptive, or that so few females reach old age under natural conditions that there is no selection for a strategy of terminal investment.
Photosynthetic nitrogen‐use efficiency in leaves of woody and herbaceous species
Authors: Hikosaka K. , Hanba Y. T. , Hirose T. , Terashima I. 
Published: March 2003

1. Photosynthetic characteristics of an annual herb, Chenopodium album, and an evergreen tree, Quercus myrsinaefolia, were compared to clarify causes of the difference in photosynthetic nitrogen‐use efficiency (photosynthetic capacity per unit nitrogen) between leaves of herbaceous and evergreen species. 2. When leaves with the same nitrogen content on an area basis were compared, photosynthetic capacity of C. album was twice as high as that of Q. myrsinaefolia. Gas‐exchange measurements showed higher intercellular CO2 concentration in C. album. Biochemical analyses indicated larger allocation of nitrogen into ribulose‐1,5‐bisphosphate carboxylase, a key enzyme of photosynthesis, and higher specific activity of ribulose‐1,5‐bisphosphate carboxylase in C. album. However, these differences were not large. 3. Compositional deviation of 13C in leaves of the two species suggested that the drop of CO2 level between the intercellular space and the chloroplast was slightly larger in Q. myrsinaefolia when compared between the leaves with the same photosynthetic capacity. 4. It is concluded that the difference in photosynthetic nitrogen‐use efficiency between C. album and Q. myrsinaefolia is not caused by a sole factor that is markedly different between the two species but by several factors each of which is slightly disadvantageous to Q. myrsinaefolia compared with C. album.
Root growth dependence on soil temperature for Opuntia ficus‐indica: influences of air temperature and a doubled CO2 concentration
Authors: Drennan P. M. , Nobel P. S. 
Published: March 2003

1. Root elongation as a function of soil temperature was determined for the CAM succulent Opuntia ficus‐indica, under three different day/night air temperatures (15 °C/5 °C, 25 °C/15 °C and 35 °C/25 °C) and an ambient (360 μmol mol–1) vs a doubled CO2 concentration (720 μmol mol–1) at 25 °C/15 °C, the optimum temperature for net CO2 uptake. 2. Root elongation occurred at soil temperatures from 12 °C (at 15 °C/5 °C) to 43 °C (at 35 °C/25 °C) with optimum temperatures of 27–30 °C, similar to other CAM succulents and consistent with the distribution of this shallow‐rooted species in warm regions. Although a doubled CO2 concentration did not alter the optimum or limiting soil temperatures, increases of up to 5 °C in these temperatures accompanied the 20 °C increase in day/night air temperatures. 3. Root elongation rates at optimum soil temperatures ranged from 5·4 mm day–1 (15 °C/5 °C), through 6·6 mm day–1 (25 °C/15 °C), to 10·4 mm day–1 (35 °C/25 °C) with a 25% increase under a doubled CO2 concentration. Highest root elongation rates at 35 °C/25 °C may reflect changing root vs shoot sink strengths in a species with a highly plastic root system. 4. At limiting soil temperatures, the length of the cell division zone was reduced by an average of 20% and cell length at the mid‐point of the elongation zone by 10%. Increased root elongation rates under a doubled CO2 concentration reflected increased cell elongation. 5. The temperature response for the roots of O. ficus‐indica and stimulation of elongation by a doubled CO2 concentration indicate that root growth for this highly productive species should be enhanced by predicted global climate change.
Effects of elevated temperature on multi‐species interactions: the case of Pedunculate Oak, Winter Moth and Tits
Authors: Buse A. , Dury S. J. , Woodburn R. J. W. , Perrins C. M. , Good J. E. G. 
Published: March 2003

1. The effects of temperature on the Oak–Winter Moth–Tit food chain were studied at Wytham Wood, Oxford, and experimentally in the controlled environment solardomes at the Institute of Terrestrial Ecology, Bangor. 2. Tree cores from Wytham indicated that mature Oaks grew best at high temperatures and rainfall, but with low caterpillar populations. Young trees grew less well at elevated temperature, probably because they lost more water than they gained. Elevated temperatures advanced budburst, reduced foliar nitrogen and increased leaf toughness. 3. Moth eggs laid later or maintained at cooler temperatures than average required fewer heat units to hatch. Caterpillars took up to 50 days to complete growth at field temperatures but did so in only 20 days at a constant 15 °C. 4. The mass of Tit chicks at day 15 (day 1 = egg hatch) was positively correlated with temperature and negatively correlated with rainfall during the growing period. 5. At elevated temperature, budburst and moth egg hatch were synchronized, but earlier. Late feeding larvae and larvae fed on leaves from trees grown at elevated temperature produced smaller pupae. Pupal mass was unaffected when caterpillars and trees were maintained together under the same conditions. 6. Delaying egg hatch in Tits, to simulate conditions at elevated spring temperatures, resulted in reduced chick mass, body size and fledging success. This occurred because the chicks were fed later and prey quality was poorer, because the peak of caterpillar biomass was missed. 7. We predict that moth reproductive output will be retained at elevated temperatures because both leaves and caterpillars develop faster. Brood size in birds may be reduced because they cannot lay early enough to coincide with the narrower peak of food abundance.
Patch depression in grazers: the roles of biomass distribution and residual stems
Authors: Ginnett T. F. , Dankosky J. A. , Deo G. , Demment M. W. 
Published: March 2003

1. In this paper the results are presented of two experiments designed to examine the relationship between sward structure variables and the nature of patch depression experienced by a large grazing herbivore, Bos taurus, grazing from small patches of forage. In experiment 1 the spatial distribution of leaves within patches was varied. In experiment 2 the role of reproductive stems of different lengths as potential intake rate inhibitors was examined. 2. Both experiments were conducted by offering cattle hand‐constructed swards of Orchardgrass (Dactylis glomerata) leaves attached to plywood boards. Each of three experimental animals was allowed to take 10, 20, 30, 45 or 60 bites from a patch and intake was estimated on the basis of pregrazing and postgrazing dry‐matter. All trials were videotaped and the trial length in seconds was determined from playback of the tapes. 3. In both experiments patch depression (reduction in instantaneous intake rate) was due to decreases in bite mass concomitant with patch depletion. Handling time per bite was unaffected by depletion level. In experiment 1, different spatial configurations resulted in markedly different gain functions ranging from linear to sigmoid. In experiment 2, the presence in the sward of long (15 cm) reproductive stems slowed cumulative gains by restricting bite mass and by increasing the per‐bite handling time relative to patches with shorter (5 cm) or no stems. 4. The study of patch depression mechanisms now needs to be generalized over a range of herbivore body sizes and feeding styles.
The effect of predator and prey density on the induced defence of a ciliate
Authors: Wiackowski K. , Starońska A. 
Published: March 2003

1. The level of antipredator defence should be proportional to the actual attack probability to minimize the cost of defence and maximize the net benefit. 2. The hypothesis that the induced antipredator morphology of Euplotes octocarinatus is a graded response to the actual risk of predation by Stylonychia mytilus was tested by manipulating the density of both prey and predator populations. 3. The magnitude of the response was graded according to both predator and prey density. A dense prey population may be protective since a prey is more exposed to a predator's attack as a solitary individual. 4. The results suggest that Euplotes is able to ‘estimate’ the real risk of predation and respond appropriately, without mobilizing more resources than needed. 5. Separation of the prey and predator with a nylon net revealed that the response was not induced by a water‐transmitted factor but that direct cell‐to‐cell contacts were important. This finding departs from those of other studies.
Growth responses of 15 rain‐forest tree species to a light gradient: the relative importance of morphological and physiological traits
Authors: Poorter L. 
Published: March 2003

1. Growth of seedlings of 15 rain‐forest tree species was compared under controlled conditions, at six different light levels (3, 6, 12, 25, 50 and 100% daylight). 2. Most plant variables showed strong ontogenetic changes; they were highly dependent on the biomass of the plant. 3. Growth rate was highest at intermediate light levels (25–50%) above which it declined. Most plant variables showed a curvilinear response to irradiance, with the largest changes at the lowest light levels. 4. There was a consistent ranking in growth between species; species that were fast growing in a low‐light environment were also fast growing in a high‐light environment. 5. At low light, interspecific variation in relative growth rate was determined mainly by differences in a morphological trait, the leaf area ratio (LAR), whereas at high light it was determined mainly by differences in a physiological trait, the net assimilation rate (NAR). 6. NAR became a stronger determinant of growth than LAR in more than 10–15% daylight. As light availability in the forest is generally much lower than this threshold level, it follows that interspecific variation in growth in a forest environment is mainly owing to variation in morphology.
The size–grain hypothesis and interspecific scaling in ants
Authors: Kaspari M. , Weiser M. D. 
Published: March 2003

1. The size–grain hypothesis maintains that as terrestrial walking organisms decrease in size, their environment becomes less planar and more rugose. The benefits of long legs (efficient, speedy movement over a planar environment) may thus decrease with smaller body size, while the costs (larger cross‐sectional area limiting access to the interstitial environment) are enhanced. 2. A prediction from this hypothesis – that leg size should increase proportionately with body mass – is examined. Ants are among the smallest walking animals and extend the size gradient five orders of magnitude beyond the traditional ‘mouse to elephant’ curve. The mass of 135 species of worker ants spans 3·7 orders of magnitude (0·008–53 mg). Larger ants tended to be slimmer and longer legged. Ant subfamilies varied in their scaling relationships, but four out of five showed a positive allometry for hind leg length (b > 0·33). Mammals, in contrast, show isometry for leg length over six orders of magnitude. 3. It is suggested that ants make a transition from living in an interstitial environment when small to a planar environment when large, a habit continued by most terrestrial mammals. Head length and pronotum width are robust estimators of mass in ants.
Mediterranean Fruit Fly leks: factors affecting male location
Authors: Kaspi R. , Yuval B. 
Published: March 2003

1. The mating system of Mediterranean Fruit Flies (Ceratitis capitata, Diptera: Tephritidae) is based on male leks which form within the canopies of certain trees. In this study the following hypotheses are tested: (a) fly location depends on microclimate and illumination and (b) larger and heavier males occupy preferred locations in leks. Accordingly, systematic quantitative observations of diel three‐dimensional (3‐D) locations of lekking C. capitata males were performed in field and field cage studies. 2. Fly locations were found to vary significantly during the activity hours. 3. Medflies were generally found calling from highest and most exterior locations during early morning and late afternoon hours. During the hottest hours (1200–1500) flies occupied lower locations within the tree canopy, and interior locations from 1000 to 1500. 4. Fly location (from 1000 to 1700) was correlated with the azimuth of the sun. However, the mean azimuth range of fly location was limited to 85° (59·45°–143·94°). 5. Both in the field and in the field cage the temperature, relative humidity and light intensity beneath the leaves on which the males perched were closer to the microclimate beneath fully shaded leaves than to microclimates beneath leaves exposed to direct sunlight. 6. It is concluded that male medflies occupy locations which confer suitable microclimates for calling and copulating, and suitable 3‐D locations within the canopy which provide protection from predators, wind, direct sunlight and water loss.
Reverse phenology and dry‐season water uptake byFaidherbia albida(Del.) A. Chev. in an agroforestry parkland of Sudanese west Africa
Authors: Roupsard O. , Ferhi A. , Granier A. , Pallo F. , Depommier D. , Mallet B. , Joly H. I. , Dreyer E. 
Published: March 2003

1.Faidherbia (Acacia) albidais a multipurpose tree widely distributed in semiarid Africa, notably in agroforestry parklands. It is in leaf during the dry season and defoliated during the rainy season, displaying therefore a peculiar reverse phenology. The related water‐use strategy, including leaf water potential, sapflow, hydraulic conductance and depth of uptake, were monitored on adult trees in a Sudanese west‐African parkland.2.Despite a severe drought in the superficial soil layers, the predawn leaf water potential ofF. albidadropped only toca.– 0·5 MPa during the end of the dry season, indicating only a moderate water stress.3.Radial trunk growth ceased before the end of the dry season and could have been affected by the moderate drought stress. However, leafiness remained constant during the dry season. Leaf shedding occurred after the first rains and was probably independent of drought.4.Faidherbia albidadisplayed large transpiration rates under favourable conditions but the ratio of sapflow to Penman evapotranspiration and the soil‐to‐leaf specific hydraulic conductance decreased severely towards the end of the dry season.5.Roots ofF. albidawere distributed through the weathered rock, down to a depth of 7 m, and vanished in the vicinity of a permanent water‐table. The isotopic composition of oxygen in the xylem sap (δ18O) remained very close to the values recorded in the water‐table during the course of the year. Phreatophytism thus explained the maintenance of growth and transpiration during the dry season. Nevertheless, during early rains, δ18O of sap switched towards the composition of the superficial soil layers, indicating facultative phreatophytism.6.Reverse phenology, low density and depth of water uptake ofF. albidaindicated a low competition with annual crops for water; the fraction of annual rainfall used by the trees was estimated to remain below 5%.
Costs of rapid growth: the risk of aggression is higher for fast‐growing salmon
Authors: Nicieza A. G. , Metcalfe N. B. 
Published: March 2003

1. Agonistic behaviour can be an important trait in determining individual success under interference competition, but it also generates energetic and physiological costs. The ensuing trade‐off is expected to be dependent on the individual state. This study tests whether aggression patterns of juvenile Atlantic Salmon Salmo salar are linked to the recent growth history and the developmental pathway adopted by fish (early vs late migrants). 2. By manipulating growth rates over 1 month in the autumn, three groups of fish were produced differing in body size and thereby in the length increment necessary to achieve the threshold size for migration in the following spring. Fish that had experienced reduced rations or abnormally low temperatures during the manipulation period experienced ‘catch‐up’ growth after the resumption of standard growth conditions. 3. Aggression was strongly connected to growth bimodality and the underlying developmental polyphenism. Fast‐growing (upper modal group, UMG) fish (which would migrate in the spring) were more aggressive than slow‐growing (lower modal group, LMG) fish (which would delay migration for another year), but they were also more vulnerable to being attacked by conspecifics. 4. Aggressive acts initiated by UMG fish were strongly biased towards fish of the same category (57–77% of aggressive acts being against other UMG fish). Under illumination conditions simulating overcast nights, UMG individuals sharply reduced their aggressiveness and were not selective in their attacks. The aggression by LMG fish was more evenly distributed between modal groups (44–74% of attacks were against UMG) regardless of light levels. 5. Recent growth history had no consistent effect on aggression rates, although under overcast night conditions the rate of attacks received by non‐manipulated UMG fish was twice as high as that for fish undergoing compensatory growth. 6. These results demonstrate a link between developmental pathways and aggression patterns. They also show that individuals maintaining a fast growth strategy over the winter experience a more aggressive social environment than individuals adjusting feeding rates to ensure safe maintenance levels. The reduced involvement of LMG fish in agonistic encounters conforms to a strategy of avoidance of those energetic and physiological costs that ultimately could compromise overwintering survival.
Trade‐offs in low‐light CO2 exchange: a component of variation in shade tolerance among cold temperate tree seedlings
Authors: Walters M. B. , Reich P. B. 
Published: March 2003

Abstract1. Does enhanced whole‐plant CO2 exchange in moderately low to high light occur at the cost of greater CO2 loss rates at very‐low light levels? We examined this question for first‐year seedlings of intolerant Populus tremuloides and Betula papyrifera, intermediate Betula alleghaniensis, and tolerant Ostrya virginiana and Acer saccharum grown in moderately low (7·3% of open‐sky) and low (2·8%) light. We predicted that, compared with shade‐tolerant species, intolerant species would have characteristics leading to greater whole‐plant CO2 exchange rates in moderately low to high light levels, and to higher CO2 loss rates at very‐low light levels.2. Compared with shade‐tolerant A. saccharum, less‐tolerant species grown in both light treatments had greater mass‐based photosynthetic rates, leaf, stem and root respiration rates, leaf mass:plant mass ratios and leaf area:leaf mass ratios, and similar whole‐plant light compensation points and leaf‐based quantum yields.3. Whole‐plant CO2 exchange responses to light (0·3–600 µmol quanta m−2 s−1) indicated that intolerant species had more positive CO2 exchange rates at all but very‐low light (< 15 µmol quanta m−2 s−1). In contrast, although tolerant A. saccharum had a net CO2 exchange disadvantage at light > 15 µmol quanta m−2 s−1, its lower respiration resulted in lower CO2 losses than other species at light < 15 µmol quanta m−2 s−1.4. Growth scaled closely with whole‐plant CO2 exchange characteristics and especially with integrated whole‐plant photosynthesis (i.e. leaf mass ratio × in situ leaf photosynthesis). In contrast, growth scaled poorly with leaf‐level quantum yield, light compensation point, and light‐saturated photosynthetic rate.5. Collectively these patterns indicated that: (a) no species was able to both minimize CO2 loss at very‐low light (i.e. < 15 µmol quanta m−2 s−1) and maximize CO2 gain at higher light (i.e. > 15 µmol quanta m−2 s−1), because whole‐plant respiration rates were positively associated with whole‐plant photosynthesis at higher light; (b) shade‐intolerant species possess traits that maximize whole‐plant CO2 exchange (and thus growth) in moderately low to high light levels, but these traits may lead to long‐term growth and survival disadvantages in very‐low light (< 2·8%) owing, in part, to high respiration. In contrast, shade‐tolerant species may minimize CO2 losses in very‐low light at the expense of maximizing CO2 gain potential at higher light levels, but to the possible benefit of long‐term survival in low light.
Very early detection of canopy presence by seeds through perception of subtle modifications in red:far red signals
Authors: Batlla D. , Kruk B. C. , Benech‐Arnold R. L. 
Published: March 2003

Abstract1. An early inhibition of germination in seeds of Silene gallica and Brassica campestris which were continuously exposed to the light environment under an establishing wheat canopy, was observed in two different experiments. Inhibition occurred c.15 days after crop emergence, when the canopy leaf area index (LAI) was below one and the red (R):far‐red (FR) ratio recorded under the canopy was well above 0·8.2. This inhibitory effect was either overcome by filtering FR light through a solution of CuSO4 or could be artificially imposed by simulating the canopy with filters yeilding a R:FR ratio of 0·95 and 0·8. These results show that light subtly enriched with FR was the environmental factor regulating germination below the developing canopy.3. Exposure to canopy‐filtered light pulses of 1 h (presumably sufficient to saturate a low fluence response, LFR) did not inhibit seed germination. Moreover, such treatment promotes germination up to an extent similar to that previously observed in the laboratory after a saturating pulse of R light. Instead, prolonged exposures were required to inhibit germination. These results, together with the relatively high R:FR ratios measured below the canopy in early stages of its establishment, suggest that a high irradiance response (HIR) would be involved in such a regulation.4. This capacity to detect small environmental light‐quality modifications when exposed to high irradiances, would allow the seeds from these species to detect the presence of a canopy in the very early stages of its establishment and to stay in ‘safe’ pre‐germination phases when the probability of successful seedling establishment is low.