bluuebunny/crossref_metadata_2025_split huggingface dataset:
Partitioning of dry mass and leaf area within plants of three species grown at elevated CO2
Authors: Gunn S. , Bailey S. J. , Farrar J. F. 
Published: March 2003

1. We tested the hypothesis that the net partitioning of dry mass and dry mass:area relationships is unaltered when plants are grown at elevated atmospheric CO2 concentrations. 2. The total dry mass of Dactylis glomerata, Bellis perennis and Trifolium repens was higher for plants in 700 compared to 350 μmol CO2 mol–1 when grown hydroponically in controlled‐environment cabinets. 3. Shoot:root ratios were higher and leaf area ratios and specific leaf areas lower in all species grown at elevated CO2. Leaf mass ratio was higher in plants of B. perennis and D. glomerata grown at elevated CO2. 4. Whilst these data suggest that CO2 alters the net partitioning of dry mass and dry mass:leaf area relationships, allometric comparisons of the components of dry mass and leaf area suggest at most a small effect of CO2. CO2 changed only two of a total of 12 allometric coefficients we calculated for the three species: ν relating shoot to root dry mass was higher in D. glomerata, whilst ν relating leaf area to total dry mass was lower in T. repens. 5. CO2 alone has very little effect on partitioning when the size of the plant is taken into account.
Predicting responses to climate change: the effect of altitude and latitude on the phenology of the Spittlebug Neophilaenus lineatus
Authors: Fielding C. A. , Whittaker J. B. , Butterfield J. E. L. , Coulson J. C. 
Published: March 2003

1. The phenology of Neophilaenus lineatus (Homoptera: Cercopidae) was studied along altitudinal and latitudinal transects in the UK. The response of the life cycle to these existing temperature gradients has been used to predict the likely effects of future climatic warming. 2. The date of spring egg hatch varied by a maximum of 4 weeks across the altitudinal gradient (440 m) and by 2 weeks in different years of the study. Autumn and winter temperatures do not determine hatching date because the eggs are in diapause during this period. It is only when the eggs terminate diapause in early spring that temperature differences between years and altitudes (or as a result of climatic warming) start to affect the date of egg hatch. 3. The delayed egg hatching with increasing altitude meant that the start of nymphal development was later at higher altitudes. The development rate of nymphs at higher altitudes was not significantly different from that at lower altitudes because the altitudinal lag in temperature was partially compensated for by the more advanced state of the season. Annual differences in spring and summer temperatures resulted in variations in nymphal development rate between years, with a 1 °C temperature rise shortening nymphal development by 3·5 days. 4. The appearance of adults was delayed by 5·6 days for every 100 m increase in altitude, largely as a consequence of the later egg hatch at higher altitudes. The later appearance of the adults at higher altitudes and in colder years, reduces the length of the potential oviposition period as females are killed by autumn frosts. Climatic warming would expand the length of the oviposition period and thus increase the upper altitude limits of N. lineatus. 5. A 4·5 ° latitude difference within the UK appeared to have little effect on the timing of development in N. lineatus, possibly as a result of a geographical cline in temperature or photoperiod response. 6. Annual insects, such as N. lineatus, are likely to show a relatively small geographical displacement as a consequence of climatic warming. This is because of the temperature mitigating responses of diapause and the relative stability of the length of the development period over wide altitudinal and latitudinal ranges.
Does immune challenge affect torpor duration?
Authors: BURTON R. S. , REICHMAN O. J. 
Published: March 2003

1. Hibernation may alter the relationship between pathogens and their hosts; low host temperatures can prevent pathogen replication. Therefore, manipulating the timing and duration of torpor bouts could allow animals to gain an advantage over pathogens. 2. Thirty‐two Turkish Hamsters (Mesocricetus brandti) were placed in short‐day, cold conditions. After 10 weeks, 20 animals were challenged with an antigen to simulate a pathogen infection. Ten of these animals were returned to the cold (‘cold‐challenged’). The other 10 animals were placed in warm conditions (‘warm‐challenged’). Twelve animals received saline injections and were returned to the cold (‘cold‐control’). Cold‐challenged animals spent significantly more time in torpor than did cold‐control animals. 3. After 6·5 weeks, all animals were housed in warm conditions and ceased torpor. Both cold‐challenged and warm‐challenged animals received a second injection of antigen. There was no correlation between time spent euthermic and level of secondary humoral response of cold‐challenged animals. The secondary humoral response of the cold‐challenged animals was significantly lower than that of warm‐challenged animals. 4. In this study immune status influenced torpor duration, and torpor caused immunosuppression. Hibernators may manipulate body temperature in order to combat pathogens while their own immune systems are suppressed.
A test of two hypotheses explaining the seasonality of reproduction in temperate mammals
Authors: Fournier F. , Thomas D. W. , Garland T. 
Published: March 2003

1. Two proposed hypotheses about energy allocation were tested to explain the patterns of seasonal reproduction found in temperate mammals. The two hypotheses predict either that total demand for energy is greater during reproduction than during winter (when thermoregulatory costs are high) (Increased Demand Hypothesis) or that total costs during winter are greater than or equal to total costs during reproduction (Reallocation Hypothesis). 2. Data were compiled from the literature on summer (non‐reproducing) and winter metabolic rates of temperate mammals, and were used on litter sizes and a published equation to predict metabolic rates during lactation. 3. All three measures of metabolic rate scaled to body mass with slopes significantly less than one. Metabolic rates during winter averaged ≈ 2 times greater than those of non‐reproducing mammals during summer. On average, predicted metabolic rates during lactation were not significantly greater than during winter, but for some individual species they clearly were. 4. It is suggested that neither the Reallocation nor the Increased Demand Hypothesis can fully explain seasonal reproductive patterns in temperate mammals.
Blood parasites, leucocytes and plumage brightness in the Cirl Bunting,Emberiza cirlus
Authors: Figuerola J. , Muñoz E. , Gutiérrez R. , Ferrer D. 
Published: March 2003

1.Although a female preference for pairing with brightly plumaged males has been reported in many species, the reasons for this choice are not fully understood.2.Parasites have been proposed as playing an important role in shaping these preferences because, by pairing with brightly coloured individuals, females can obtain parasite‐free and/or more healthy mates.3.In this paper one of the predictions of this hypothesis is tested, namely a higher health level in brightly coloured individuals, by analysing the relationships among blood parasites, leucocyte levels and plumage brightness in the Cirl Bunting,Emberiza cirlus.4.Two species of blood parasites were detected. Whereas a lower body condition was detected in individuals infected byLeucocytozoon cambournaci,no such differences were associated withPlasmodium relictuminfections. Infected individuals showed higher total leucocyte counts than non‐infected individuals.5.Colour intensity of carotenoid derived colorations was negatively correlated to the relative proportion of lymphocytes and positively correlated to the relative presence of heterophils. Furthermore, the size of yellow feathered areas was positively correlated with the absolute number of leucocytes and the relative presence of heterophils. Only some of these relationships were found for non‐carotenoid derived traits.6.These results suggest that male plumage yellow coloration in the Cirl Bunting is a reliable indicator of health status and supports the hypothesis that females obtain more parasite‐free mates if they pair with brightly coloured individuals.
The defensive strike of the Eastern Brownsnake, Pseudonaja textilis (Elapidae)
Authors: Whitaker P. B. , Ellis K. , Shine R. 
Published: March 2003

Abstract1. The Eastern Brownsnake, Pseudonaja textilis, is a large (to 2 m), slender‐bodied, highly venomous elapid that causes most snakebite human fatalities in Australia. The response of recently captured snakes to human harassment was quantified. Using high‐speed film, the type of neck display, time taken to strike, strike accuracy, strike speed and effectiveness of bite were recorded.2. The snakes were surprisingly tolerant of harassment, especially at body temperatures similar to those that they exhibit in the field during the activity season. Smaller snakes spent more time trying to escape than did larger snakes. Most snakes gave warning prior to the strike, 58% by full (high) display and 19% by partial (low) display. Some 25% of strikes were bluff.3. Body temperature (over the range 18–36 °C) had little effect on most of the variables measured, including: the frequency of display and bluff, the duration of the strike (mean 0·28 s), the strike distance (mean 0·34 m), the mean overall strike speed (1·1 m s−1, range 0·25–1·80), the mean fastest strike speed (during 1/25 s, = 1·7 m s−1, range 0·3–3·4), or the accuracy of the strike.4. Instead, the type of prestrike display was related to strike speed and accuracy: strikes preceded by a full neck display were slower but more accurate (and more likely to involve venom transfer) than those preceded by minimal display.5. Contrary to popular opinion, Eastern Brownsnakes are reluctant to deliver firm bites in response to human harassment even when continuously provoked. It is estimated that only 15% of the strikes recorded had the potential to cause significant envenomation.
Influence of temperature on hydrodynamic costs of morphological defences in zooplankton: experiments on models of Eubosmina (Cladocera)
Authors: Lagergren R. , Lord H. , Stenson J. A. E. 
Published: March 2003

Abstract1. If swimming speed is correlated to fitness (e.g. by affecting food intake or the chance to evade predators) or considerable energy is expended in swimming, zooplankton wearing protruding structures (as predator defence) that significantly increase drag resistance must pay a cost for the better protection against predators that these traits imply.2. In an experiment with plastic models, the drag and energy consumption of swimming in two species of Eubosmina were examined. Eubosmina longispina has a typical Bosmina morphology with a low carapace and short antennule, whereas E. coregoni gibbera has a very high carapax and long antennule.3. At 5 °C, E. c. gibbera had 32–45% higher drag than E. longispina. At 20 °C, the difference is 20–45%.4. A mathematical model of swimming predicts that these differences in drag should result in 18–20 (at 5 °C) or 14–16 (at 20 °C) percentage lower speed for E. c. gibbera than for E. longispina if they use the same amount of energy in swimming.5. The relative difference in drag or swimming speed between the two species was highest at low Reynolds number (i.e. low speed or low temperature). These results show that hydrodynamic costs of extreme morphology may increase with decreasing temperature.6. The increased cost of morphological antipredator defence at low temperatures may be enlightening with regard to the role of temperature in the induction of cyclomorphic traits in zooplankton. This may be one explanation for why extreme forms of E. c. gibbera and some Daphnia are only found in the summer when water temperature is high.
The evolution of sexual dimorphism in relation to mating patterns, cavity nesting, insularity and sympatry in the Anseriformes
Authors: Figuerola J. , Green A. J. 
Published: March 2003

AbstractIn addition to genetic drift, both natural and sexual selection may be responsible for interspecific differences in male and female size and coloration. Comparative methods were used to analyse the patterns of dimorphism in the Anseriformes (wildfowl) in relation to mating patterns, nest placement, insularity and number of closely related, sympatric species.The following predictions were tested about the evolution of dimorphism: (a) that evolutionary changes are more common in male than in female coloration; (b) that the intensity of sexual selection is correlated with the evolution of bright coloration and sexual dimorphism; (c) that the nature of nest sites influences the evolution of bright coloration in females via its effect on predation risk, and the extent of size dimorphism via the limits to the size of females using cavities; (d) that insular species show more size dimorphism and less colour dimorphism than mainland species; and (e) that sexual dichromatism is more common in species living in sympatry with a larger number of similar species.Evolutionary changes in plumage brightness were found to be more frequent in males than in females. Changes in mating patterns were significantly correlated with changes in plumage brightness in both males and females and in plumage dichromatism, but not with changes in size dimorphism. Evolutionary transitions from open to hole nesting did not affect plumage dichromatism or size dimorphism. A significant association was detected between insularity and the probability of changes in male brightness, but there was no relationship between insularity and size dimorphism. Sexual dichromatism and bright male (but not female) plumage tend to occur in wildfowl sympatric with a high number of species from the same tribe.In conclusion, mating patterns, insularity and sympatry appear to have evolved in correlation with changes in sexual dichromatism and plumage brightness in the Anseriformes, but not with changes in sexual size dimorphism.
Effects of display size and position on individual floral longevity in racemes of Narthecium asiaticum (Liliaceae)
Authors: Ishii H. S. , Sakai S. 
Published: March 2003

Summary

We analysed the longevity of individual flowers and the effect on pollination success with respect to floral display size of racemes (number of flowers open at one time) for the sequentially blooming plant Narthecium asiaticum (Liliaceae). The longevity of lower‐ and middle‐positioned flowers (about 7 days in 1998 and 6 days in 1999) was much greater than the length of time required for the completion of male (about 3 days) and female (within 3 days) functions.
We suggest that such prolonged longevity benefits the plant in terms of pollinator attraction, because prolonged longevity in lower and middle flowers leads to large display sizes of racemes. Increased display size would not have resulted in an increase of geitonogamy in this species, because most pollinators left racemes after probing only one flower. Rather, large displays attracted more pollinators and increased pollen dispersal from individual flowers.
The longevity of upper‐positioned flowers (about 4 days in 1998 and 3 days in 1999) was less than that of lower‐ and middle‐positioned flowers – almost the same as the length of time required for the completion of male and female functions. This difference is possibly because upper flowers open later within racemes: if there were no subsequent flowers, prolonged floral longevity would not benefit the plants and would only consume resources used to maintain the flower.
Floral longevity within inflorescence should be understood in relation to the effects of floral display size and floral positions, in addition to the accrual rates of male and female functions and the maintenance cost of individual flowers.
Moa ghosts exorcised? New Zealand’s divaricate shrubs avoid photoinhibition
Authors: Howell C. J. , Kelly D. , Turnbull M. H. 
Published: March 2003

Summary

An intriguing feature of the New Zealand flora is the high frequency of ‘divaricate’ shrubs and tree juveniles. These plants have numerous interlacing wide‐angled branches with small leaves and no or few leaves in the outer canopy. They comprise 10% of native woody species, and have evolved in 18 different plant families.
We tested the hypothesis that the leaves of divaricate plants are sensitive to cold‐induced photoinhibition, and that self‐shading by outer branches reduces light intensities enough to prevent photodamage. In a field experiment, leaves of three divaricate species (Aristotelia fruticosa A. Cunn., Corokia cotoneaster Raoul and Coprosma propinqua Hook. f.) inside the north (sunny) side of the shrubs were exposed to one of three experimental treatments over winter: (i) control leaves which were not manipulated; (ii) exposed leaves which had their outer screen of branches pruned away leaving them open to full sun; or (iii) shaded leaves which were exposed by pruning, then sheltered from direct sunlight with shade cloth.
Experimental removal of the shielding branches in winter led to rapid (< 20 days), large (23–31%) and persistent (> 3 months) reductions in the maximum photosynthetic capacity (Amax) and photochemical efficiency (dark adapted Fv/Fm) in exposed leaves, but not in shaded leaves. Full recovery of photosynthetic capacity and photochemical efficiency was displayed by Coprosma propinqua, but very little capacity for recovery was displayed by Aristotelia fruticosa or Corokia cotoneaster.
When the effects of self‐shading and photoinhibition were combined, control leaves photosynthesized faster than exposed leaves at all ambient irradiances in A. fruticosa, and in bright light (> 500 µmol m−2 s−1) in C. cotoneaster.
Our data show that by shielding their leaves within an outer screen of branches, the three divaricate species studied reduce photoinhibition of photosynthesis. We contend that this architectural self‐shading in divaricate plants maximizes potential carbon fixation by minimizing photoinhibition.
Forward attack modes of aquatic feeding garter snakes
Authors: Alfaro. M. E 
Published: March 2003

Summary

Previous studies have suggested that piscivorous snakes generally use sideways head sweeping to capture prey in order to minimize drag on the skull and/or to avoid pushing prey items away from the mouth. However, some aquatic species of garter snakes (genus Thamnophis) have been reported to use fast forward strikes to capture fish and amphibians. To characterize fast forward striking as a mode of piscivory in snakes and compare its use among specialist and generalist species, the aquatic specialists Thamnophis couchii and T. rufipunctatus, and a terrestrial generalist, T. sirtalis, were filmed at 250 fps (frames per second) while preying on minnows.
Both T. couchii and T. rufipunctatus oriented visually toward prey items and struck forward rapidly with peak head velocities that approached speeds attained by fast striking booid, colubrid and viperid species on land. In contrast, T. sirtalis did not orient visually toward specific prey items and displayed strikes that were four to six times slower than those of specialist species.
Aquatic specialists used moderate amounts of cranial rotation during jaw opening and achieved maximum gape within 20 ms of jaw opening. In the generalist T. sirtalis, jaw opening took 40–60 ms and was due almost entirely to mandibular rotation.
Significant differences in the prey capture kinematics of the two aquatic specialists are consistent with the hypothesis that T. couchii is an open water hunter, whereas T. rufipunctatus is an ambush predator. Thamnophiine snakes display a diversity of aquatic prey capture styles that reflect different behavioral and mechanical solutions to the problem of feeding in water.
Nest scrape design and clutch heat loss in Pectoral Sandpipers (Calidris melanotos)
Authors: Reid J. M. , Cresswell W. , Holt S. , Mellanby R. J. , Whitfield D. P. , Ruxton G. D. 
Published: March 2003

Summary 1. The reasons why birds construct nest scrapes, and the extent to which scrape designs reflect functional optima, are poorly understood. Working on Pectoral Sandpipers (Calidris melanotos, Vieillot), we investigated whether scrapes function to insulate clutches and are efficiently designed to reduce heat loss rates. 2. Excavating a scrape and using lining material reduced the rate at which an object positioned within a scrape lost heat by 9% and 25%, respectively, suggesting that lined scrapes insulate clutches. 3. The rate of heat loss from an object within a scrape increased with scrape depth and decreased non‐linearly with lining depth. The extent to which wind increased forced convective heat loss decreased with scrape depth. 4. On average, Pectoral Sandpipers used the minimum lining depth that approximately minimized heat loss through the lining. Mean scrape depth approximately minimized convective cooling in windy conditions while minimizing heat loss to the ground. Pectoral Sandpiper scrapes therefore efficiently reduced heat loss given conflicting environmental thermal pressures. 5. Available lining materials differed in insulative quality when both damp and dry. Pectoral Sandpipers used lining materials that insulated relatively well when damp more than expected given random collection of locally available materials. Linings therefore insulated efficiently given the damp nesting environment.
Food pulses increase longevity and induce cyclical egg production in Mediterranean fruit flies
Authors: Carey J. R. , Liedo P. , Harshman L. , Liu X. , Müller H.‐G. , Partridge L. , Wang J.‐L. 
Published: March 2003

Summary 1. Inasmuch as virtually all studies on mortality and reproduction in insects are conducted under conditions in which food availability is constant, little is known about the demographic response of insects to variable food environments. For example, it is not known if and to what extent the life expectancy of insects subjected to shortages of high‐quality food will increase and/or whether this increase is associated with major decreases in lifetime reproduction. 2. Therefore cohorts of 100 individual female medflies were subjected to different sets of conditions of protein availability (interspersed with sugar‐only diets) including ad libitum sugar‐only (no protein), ad libitum protein and full (protein) diet either every 2nd, 4th, 6th, 11th or 21st day, as well as two lag‐treatments (1 day full diet followed by 30 days sugar‐only, followed by one of two cyclical treatments). 3. Both life expectancy and lifetime reproduction were strongly affected by specific treatments. Specifically (i) mortality was inversely related to frequency of protein availability whereas lifetime reproduction was directly related; (ii) distinct cycles in reproduction began to appear when food pulse cycles were as short as every 4 days. However, egg‐laying peaks and troughs were particularly pronounced in the 10‐ and 20‐day food pulse cycles; (iii) the peak and trough levels were inversely related to cycle length; and (iv) the within‐cycle height was independent of cycle length, occurring 4 days after protein food was made available to the cohort whether the cycle length was 5, 10 or 20 days. 4. The results shed new light on the within‐ and between‐cycle and lifetime dynamics of reproduction when insects are subjected to variable food environments and indicate that medfly females track food level very closely.