bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth dynamics and mortality of the encrusting sponge Crambe crambe (Poecilosclerida) in contrasting habitats: correlation with population structure and investment in defence
Authors: Turon X. , Tarjuelo I. , Uriz M. J. 
Published: March 2003

1. A trade‐off was predicted between investment in defence and growth rate in the encrusting sponge Crambe crambe (Schmidt), while survival rates were expected to correlate positively with the production of defences. Previous studies have demonstrated that this sponge is better defended (chemically and physically) in shaded animal‐dominated habitats than in well‐illuminated habitats, dominated by algae. It was determined whether these habitat‐associated differences in investment correlate with differences in growth, regeneration and mortality rates of small specimens (initial average area less than 100 mm2) of this sponge. 2. In the 2 years of the study the sponge grew slowly (size increased 2·5 times on average), and showed high interindividual variation in growth rates. A seasonal pattern was evident, with marked size increases from May to October. Significantly higher growth rates (on a monthly basis) were found in the well‐illuminated habitat during the second year of study. There was also a negative relationship between monthly growth rate and toxicity (measured in previous studies). No differences were found in sponge regeneration rates between communities. 3. Mortality was significantly higher in individuals from the well‐illuminated habitat, and mainly affected the smallest sponges (< 150 mm2). 4. This sponge was significantly more abundant in the shaded habitat, but the mean size of the sponges was greater in the well‐illuminated habitat. The size distributions in the two communities were also significantly different. Sponges of the smallest size classes were more abundant in the shaded community. 5. It is concluded that sponges in the shaded habitat, in which investment in defence was greatest, featured higher survival but grew more slowly than those in the well‐illuminated habitat. Differential mortality and growth observed in the study were sufficient to explain the patterns of abundance and size distributions of the established sponge populations from these two habitats.
Granivore impact on soil‐seed reserves in the central Monte desert, Argentina
Authors: Marone L. , Rossi B. E. , Lopez DE Casenave J. 
Published: March 2003

1. Mechanisms of grass‐ and forb‐seed input and output in the central Monte desert of Argentina were studied in 1995 to test the hypothesis that seed consumption by autumn–winter granivores, especially birds, has qualitative as well as quantitative effects on soil‐seed reserves. 2. The abundance of perennial grass seeds in late summer soils (≈ 2400 seeds m–2 or 0·36 g m–2) remained unchanged the following early spring (≈ 2700 seeds m–2 or 0·39 g m–2), despite the incorporation of about 3000 seeds m–2 or 0·71 g m–2 newly produced grass seeds during autumn–winter. Grass seeds appeared to be heavily consumed, especially the medium‐sized ones. 3. The annual forb‐seed bank was about the same size in late summer (≈ 5500 seeds m–2 or 1·34 g m–2) as in early spring (≈ 6500 seeds m–2 or 1·53 g m–2). Since forb‐seed production had been relatively low (≈ 400 seeds m–2 or 0·12 g m–2), these seeds apparently suffered negligible postdispersal losses. 4. This pattern of grass‐ and forb‐seed loss coincides with the pattern of seed consumption by granivorous birds – on average, 93% of seed mass in bird stomachs was from grass seeds, while only 7% was from forb seeds. 5. Further evidence of a major impact of bird foraging on seed reserves is that the mass of particular grass seeds that was lost from soils was positively correlated with the mass of such seeds in bird diets, and that the main target of bird consumption, i.e. medium‐sized grass seeds, suffered the highest postdispersal loss. 6. It is concluded that autumn–winter granivores in the central Monte desert, particularly birds, mainly consume newly produced grass seeds and that they might have major qualitative as well as quantitative impacts on soil‐seed reserves.
Variation in energy intake and basal metabolic rate of a bird migrating in a wind tunnel
Authors: LindstrÖM Å. , Klaassen M. , Kvist A. 
Published: March 2003

1. We studied the changes in body mass, metabolizable energy intake rate (ME) and basal metabolic rate (BMR) of a Thrush Nightingale, Luscinia luscinia, following repeated 12‐h migratory flights in a wind tunnel. In total the bird flew for 176 h corresponding to 6300 km. This is the first study where the fuelling phase has been investigated in a bird migrating in captivity. 2. ME was very high, supporting earlier findings that migrating birds have among the highest intake rates known among homeotherms. ME was significantly higher the second day of fuelling, indicating a build‐up of the capacity of the digestive tract during the first day of fuelling. 3. Further indications of an increase in size or activity level of metabolically active structures during fuelling come from the short‐term variation in BMR, which increased over the 2‐day fuelling period with more than 20%, and in almost direct proportion to body mass. However, mass‐specific BMR decreased over the season. 4. The patterns of mass change, ME and BMR of our focal bird following two occasions of 12‐h fasts were the same as after flights, indicating that fast and flight may involve similar physiological processes. 5. The relatively low ME the first day following a flight may be a contributing factor to the well‐known pattern that migrating birds during stopover normally lose mass the first day of fuelling.
Sexually dimorphic growth in the dioecious tropical shrub, Siparuna grandiflora
Authors: Nicotra A. B. 
Published: March 2003

1. To demonstrate evolved sex‐based differences in vegetative traits of dioecious plant species, one must consider both pre‐reproductive and reproductive individuals, as dimorphic patterns commonly arise secondarily from different effects of reproduction on resource balance. 2.
Siparuna grandiflora, a neotropical dioecious shrub in which females allocate significantly more biomass to reproduction than males, was studied for 2 years (three reproductive events) to determine whether sex‐based differences in stem growth, leaf production and allocation pattern could be detected in pre‐reproductive individuals grown from cuttings in field plots or in mature naturally occurring individuals. 3. Among pre‐reproductive individuals, females accumulated more stem and leaves than males, but among mature individuals, no sex‐based growth differences were apparent. In mature individuals, both growth and leaf longevity were positively correlated with reproductive frequency. With regards allocation, pre‐reproductive males had larger leaves than females, and mature females allocated less biomass per unit stem length than males. 4. The capacity of pre‐reproductive females to grow faster than males demonstrates innate differences between the sexes. That mature females achieved equivalent growth to males, despite higher reproductive allocation, indicates that the greater growth capacity of young females is sustained in older females and enables them to compensate for greater reproductive allocation.
HOBOs, Tidbits and lizard models: the utility of electronic devices in field studies of ectotherm thermoregulation
Authors: Vitt L. J. , Sartorius S. S. 
Published: March 2003

1. A replicated experiment tested the null hypothesis that stand‐alone electronic temperature recording devices produce sets of operative temperatures similar to those produced using lizard models. 2. Commercially available electronic temperature recording devices (HOBO XT™ with external probe and Tidbit™) produced sets of operative temperatures nearly identical to models designed to mimic the size, shape, scale architecture and colour of two species of common North American lizards. 3. Tidbits™ performed better than external probes. 4. These results suggest that electronic devices (especially Tidbits™) can be substituted for models in many applications and that size, morphology, scale architecture and colour contribute very little to temperature change in small‐sized life‐like models widely used in field‐based studies on the thermal ecology of vertebrates. 5. Small differences between temperatures recorded by electronic devices and detailed lizard‐shaped models fitted with thermal probes suggest that these models may nevertheless be necessary for certain kinds of studies.
Effects of age and size at metamorphosis on performance and metabolic rates of Southern Toad, Bufo terrestris, metamorphs
Authors: Beck C. W. , Congdon J. D. 
Published: March 2003

Abstract1. Southern Toad, Bufo terrestris, tadpoles were reared at two temperatures and two food levels in a 2 × 2 factorial design. Effects of treatments on age and size at metamorphosis, metabolic rate (MR), sprint speed and endurance of metamorphs were measured.2. Across all treatments, MR, sprint speed and endurance were negatively related to age at metamorphosis and positively related to mass at metamorphosis. Therefore, decreases in larval period duration and increases in mass at metamorphosis may be advantageous in terms of locomotor performance, but disadvantageous because of the cost of increased energy expenditure on maintenance, all else being equal.3. After removing the effects of age and size at metamorphosis, neither of the treatments nor their interaction significantly affected locomotor performance. In contrast, MRs of metamorphs were significantly affected by the interaction between the food and temperature treatments, independent of age and size at metamorphosis. Thus, aspects of the larval environment may affect metamorph physiology, and possibly fitness, via mechanisms other than differences in age and size at metamorphosis.
The metabolic cost of reproduction in an oviparous lizard
Authors: Angilletta M. J. , Sears M. W. 
Published: March 2003

Abstract1. Studies of reproductive effort in ectotherms have focused primarily on the energetic investment in gamete production; much less is known about the indirect energetic costs of reproduction, such as increased metabolic costs of maintenance or activity.2. The metabolic cost of reproduction in the oviparous lizard, Sceloporus undulatus, was investigated by measuring the metabolic rate of females prior to and following oviposition.3. The metabolic rates of gravid females were adjusted for embryonic metabolism by subtracting the metabolic rate of egg clutches, measured immediately after oviposition.4. The metabolic rate of females when gravid was elevated by 122% compared with that when non‐gravid. The difference was not detected until the metabolic rates of gravid females were adjusted for the metabolic rates of the embryos.5. The increment in metabolic rate associated with reproduction was not correlated with clutch mass or body mass, indicating that different components of reproductive effort (i.e. metabolism vs gametic investment) may not covary in a predictable fashion.6. Indirect energetic costs of reproduction constitute a substantial portion of the reproductive effort of female S. undulatus, and should be incorporated into theoretical considerations of life history.
Cross‐species relationships between seedling relative growth rate, nitrogen productivity and root vs leaf function in 28 Australian woody species
Authors: Wright I. J. , Westoby M. 
Published: March 2003

Abstract1. Seedling relative growth rate (RGR) is often decomposed into the product of specific leaf area (leaf area per leaf mass, SLA), net assimilation rate (rate of mass increase per unit leaf area per unit time, NARa) and leaf mass ratio (ratio of leaf to total dry mass, LMR). Commonly, most cross‐species variation in RGR is accounted for by variation in SLA, while no general relationships occur between RGR and either NARa or LMR. NARa can be factored into the product of leaf nitrogen productivity (rate of mass increase per unit leaf nitrogen per unit time, LNP) and leaf nitrogen concentration (area basis, LNCa). In this way the influence on RGR of leaf nitrogen – how it is displayed, and how it is utilized – can be investigated.2. Seedlings of 28 Australian woody dicot species were grown under controlled, favourable conditions. Variation in SLA, LNP, LNCa and LMR explained c. 44%, 22%, 19% and 15% of variation in RGR, respectively. SLA and LNP were positively associated with RGR, while LNCa was negatively associated with RGR. LNP and LNCa were negatively correlated, the counteracting trends between RGR and each of these attributes resulting in no relationship between RGR and NARa. It is argued that this phenomenon may be widespread and may contribute to the inconsistency of reported relationships between NARa and RGR.3. The functional balance between leaves and roots can be described in terms of mass allocation and morphology (static ratios or allometric coefficients) or, alternatively, in terms of leaf ‘activity’ (NAR) and root ‘activity’ (nitrogen uptake rate, NUR). At any given time most species allocated greater mass to leaves than to roots, but species with low RGR tended to be partitioning a greater ongoing proportion of new biomass to the roots rather than to the leaves, resulting in a proportionally greater increase in root surface compared with leaf surface over time. Nitrogen uptake rate was correlated with leaf and whole‐plant nitrogen concentration, but not with other attributes. While it is clear that root and leaf functions must be co‐ordinated (and thus in balance) for growth to occur, there is little evidence that this balance varies systematically with RGR across all species.
Spatial aggregation and temporal migration of free‐living stages of the parasitic nematode Trichostrongylus tenuis
Authors: Saunders L. M. , Tompkins D. M. , Hudson P. J. 
Published: March 2003

Abstract1. Predicting outbreaks of Trichostrongylus tenuis in Red Grouse from larval counts has been hampered because of the poor recovery of the third‐stage infective larvae from heather vegetation. Two possible explanations for this poor recovery were examined: (i) larvae are spatially aggregated; (ii) larvae exhibit temporal variability in abundance and may be missed by sampling at the wrong time.2. Heather vegetation was intensively sampled and infective larvae were found to be spatially aggregated. The temporal distribution of T. tenuis also varied, with greater numbers of larvae present on heather sampled in the afternoon than the morning.3. In a series of laboratory experiments the diurnal availability of T. tenuis larvae were examined on two plant species with differing physical structures: heather and wheat. These trials were tested against infective larvae of Haemonchus contortus, a related nematode known to exhibit diurnal migration patterns. Larvae were exposed to diurnal variations in light and temperature.4. Infective larvae of both species were recovered in greater numbers during periods when the lights were on. Temperature did not have a significant influence on H. contortus larval availability but greater numbers of T. tenuis L3 were recovered at low temperature (10 °C) than at higher temperature (20 °C).5. Both temporal variation in the presence of T. tenuis larvae on vegetation and the spatial variation in larval distribution may account for poor recovery of Trichostrongylus tenuis L3 in the field.
The influence of millipedes on selected soil elements: a microcosm study on three species occurring on coastal sand dunes
Authors: A.‐M. Smit , R. J. Van Aarde 
Published: March 2003

Summary

The effect of mechanical breakdown of detritus by the millipedes Centrobolus fulgidus, Centrobolus richardii and Spinotarsus sp. on selected soil elements was investigated in the laboratory.
Microcosms containing soils, detritus and millipedes from areas undergoing vegetation regeneration were set up in a climate chamber. Short‐term changes in soil concentrations of ammonia (NH4+), nitrates (NO3−), phosphorus (P), calcium (Ca), potassium (K), magnesium (Mg), nitrogen (N) and carbon (C) in the presence and absence of millipedes were determined.
Soil concentrations of the elements investigated were higher in microcosms subjected to millipede activity than in controls. Microcosms containing Spinotarsus sp. and C. richardii were found to have the highest concentrations of Mg, K, N and C.
The results further illustrated no major sex‐specific differences for individual species.
For most elements, rates of change were not affected by millipede biomass. However, the largest effect was in rate of change of Mg and K measured at 5–15 g of millipedes per microcosm.
Compositional effects (species present) were recorded for rates of change in K concentrations.
Influence of species richness on rates of change was only recorded for K and N, with rates for both increasing as the number of species increased. The predictability of rate of change diminished for K with an increase in the number of species.
It is concluded that millipedes influence concentrations of soil elements through species‐specific differential effects. Patterns related to composition and species richness only reflect species‐specific differences. Nevertheless, the rate at which these soil elements increase in the microcosms suggests that millipede activity may accelerate the release of elements in areas undergoing vegetation development on coastal dune forests.
Carbon isotope discrimination by a sequence of Eucalyptus species along a subcontinental rainfall gradient in Australia
Authors: MIller J. M. , Williams R. J. , Farquhar G. D. 
Published: March 2003

Abstract1. The 13C/12C discrimination (Δ) by a series of co‐occurring and replacement Eucalyptus species was measured across an eightfold decrease in rainfall. As Δ is a measure of the stomatal limitation on photosynthesis, it should provide a subcontinental scale measure of water‐limited plant physiological performance.2. Leaf Δ of five of 13 species decreased with decreasing rainfall, seven exhibited no trend, and one increased. Wood Δ decreased in eight species, showed no trend in four, and increased in one species.3. Species replacements were marked by a shift in Δ reflecting greater stomatal limitation on carbon assimilation.4. Wood Δ was less variable than leaf Δ.5. There was a non‐linear response of the multispecies average leaf and wood Δ to decreasing total annual rainfall. This response reflected the spatial pattern of the sensitivities of Δ to decreasing rainfall of the individual species. It was not the result of a proposed emergent behaviour where the trend in the multispecies average differed from that of the individual species.6. Patterns of Δ across the distributions of species (reflecting increasing stomatal limitation on assimilation) did not provide a simple measure of the physiological limits of the distribution of eucalypts in north‐western Australia.
Interspecific carbon exchange and cost of interactions between basidiomycete mycelia in soil and wood
Authors: Wells J. M. , Boddy L. 
Published: March 2003

Summary1. The outcome of interactions between wood decay basidiomycete fungi is affected by the size of territory held by a mycelium. We investigated the outcomes of interactions between the cord‐forming saprotrophs Phanerochaete velutina (DC: Pers.) Parm., Phallus impudicus (L.) Pers. and Hypholoma fasciculare (Huds: Fr) Kumner over 152–155 days, determined as ability to capture or share territory in soil and wood, in terms of decay partitioning and the carbon cost of interactions.2. The outcome of interactions in wood alone differed from those in which the fungi competed for an opponents’ inoculum in soil microcosms. Competitive ability (the ability to capture or co‐occupy an opponent’s inoculum) varied according to species and inoculum age. In wood block pairings in the absence of soil there was evidence that P. velutina opportunistically utilized C previously mobilized within an opponent’s inoculum.3. In soil systems, short‐term (28‐day) respiratory losses of preloaded 14C (supplied as glucose) indicated that interaction could have a substantial C cost, depending on the resource quality of the opponents’ inocula. Phallus impudicus inocula accumulated 14C from opponents’ mycelia during ‘deadlock’ interactions, although reciprocal interspecific 14C transfer was not observed.4. Saprotrophic cord‐forming basidiomycetes are considered to be highly conservative of acquired nutrients, representing a significant nutrient reservoir in woodland ecosytems. Here we demonstrate that a potential major pathway for nutrient mineralization by this group is nutrient loss during competitive interactions in soil.
Desert shrub water relations with respect to soil characteristics and plant functional type
Authors: Sperry J. S. , Hacke U. G. 
Published: March 2003

Summary 1. Soil characteristics influence plant communities in part through water relations. Hypothetically, finer textured soils in arid climates should be associated with more negative plant and soil water potentials during drought, greater resistance of xylem to cavitation, and shallower root systems than coarse soils. 2. These hypotheses were tested by comparing the water relations of Great Basin shrubs growing in sand versus loam soils. The eight study species (Chrysothamnus nauseosus, Chrysothamnus viscidiflorus, Chrysothamnus parryi, Tetradymia glabrata, Atriplex canescens, Atriplex confertifolia, Grayia spinosa and Sarcobatus vermiculatus) varied in typical rooting depth and vegetative phenology. 3. Xylem pressures for a species were, on average, 1·1 MPa more negative in the loam versus the sand site, despite greater precipitation at the loam site. Root xylem at the loam site was, on average, 0·9 MPa more resistant to cavitation than at the sand site for the same species. There was a strong trend for shallower rooting depths at the loam versus the sand site. Within a species, roots were consistently more vulnerable to cavitation than stems, and experienced more cavitation during the growing season. 4. Over most of the summer there was much more cavitation at the loam site than at the sand site. More than 80% loss of xylem conductivity (PLC) was estimated in shallow roots of three species at the loam site by the end of July, with two of the three showing extensive leaf drop and branch mortality. Transpiration rate was negatively correlated with PLC, with a tendency for lower gas‐exchange rates in loam versus sand. 5. At the sand site, cavitation resistance was negatively correlated with estimated rooting depth. Drought‐deciduous species had the shallowest root systems and greatest resistance to cavitation. In contrast, two species with phreatophytic tendencies were summer‐active and were the most vulnerable to cavitation. 6. The cavitation resistance of roots determines the minimum water potential permitting hydraulic contact with soil. Differences in cavitation resistance of roots between desert species may contribute to differences in sensitivity of gas exchange to soil drought, ability to perform hydraulic lift, and response to late summer rain pulses.