bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laboratory screening of the juvenile responses of grassland species to warm temperature pulses and water deficits to predict invasiveness
Authors: T. A. White , Campbell B. D. , Kemp P. D. 
Published: March 2003

Summary

Two laboratory screening experiments tested the juvenile‐phase responses of 14 C3 and 12 C4 grassland species to pulses of warm temperature and water deficits. The first experiment determined germination response in relation to duration of warm temperature exposure (30/20 °C day/night). The second experiment determined the desiccation tolerance of seedlings immediately following germination.
The C4 species were more dependent on warm temperatures for germination than the C3 species. However, there was considerable variation within C3 and C4 types. In particular, Panicum dichotomiflorum was identified as the C4 species least dependent on warm temperatures, exhibiting > 50% of maximum germination in continuous cold (7 °C).
The C3 species were generally more desiccation‐tolerant than the C4 species, but there were several exceptions. Trifolium repens (C3) was ranked as the least desiccation‐tolerant whereas Setaria geniculata (C4) was the eighth most tolerant species. Large‐seeded species were more desiccation‐tolerant than small‐seeded species.
We suggest that poor desiccation tolerance contributes to the observed restriction of C4 grass invasion into productive grasslands of the wetter regions of New Zealand. On the basis of juvenile‐phase attributes, we ranked the C3 species as more invasive of these grasslands than the C4 species, and annuals as more invasive than perennials. Having invasive juvenile‐phase attributes is an advantageous adaptation for species that rely solely on regeneration from seed.
Population divergence in the plasticity of the response of Quercus coccifera to the light environment
Authors: L. Balaguer , Martínez‐Ferri E. , Valladares F. , Pérez‐Corona M. E. , Baquedano F. J. , Castillo F. J. , Manrique E. 
Published: March 2003

Summary

Quercus coccifera, a slow‐growing, evergreen oak, grows in contrasting environments in the Mediterranean Basin. Habitat‐based selection may have promoted divergence between populations with respect to phenotypic plasticity and genetic variability.
We tested the hypothesis that populations of the Q. coccifera originating from a rock outcrop, a continental garrigue formation and an oceanic forest would differ in their plastic response to light intensity. Plants from these populations were grown from acorns in a common garden at 100% and 20% full sunlight. Light response analysis was based on photochemical efficiency, xanthophyll pool, nutrient allocation, growth, crown architecture and light absorption.
Light‐responsive characters ranged from the subcellular to the whole‐plant level. The greatest divergences between sun and shade phenotypes were observed in leaf size, leaf angle and leaf area ratio. However, plasticity in these traits depended on plant provenance.
Regardless of the level of organization, populations were invariably ranked in the same order of plasticity when averaged over light‐responsive features, with plants originating from the rock outcrop showing the least plasticity and those from the forest the largest. The forest population also had the greatest genetic variability with respect to the isoperoxidase polymorphism.
Among populations, plants originating from the phosphorus‐deficient rock outcrop contained 30% more P per unit dry weight. Plants from the forest population had 5% more photoprotective xanthophylls, 30% larger total leaf area, with less lobed and larger leaves and a differential plasticity in leaf azimuth.
Differences among populations suggested ecotypic differentiation towards less phenotypic plasticity in the most homogeneous light environments. The ecological breadth of the species seemed to be derived not only from its tolerance of Mediterranean conditions but also from the specialization of its populations in contrasting habitats.
Achene mass variation in Ericameria nauseosus (Asteraceae) in relation to dispersal ability and seedling fitness
Authors: Meyer S. E. , Carlson S. L. 
Published: March 2003

Abstract1.  Ericameria nauseosus (Asteraceae) is a highly variable shrub species of western North America, whose achene mass varies sevenfold among subspecies and populations. We examined trade‐offs between seedling fitness and dispersal ability by asking: does greater achene mass reduce dispersal ability, and is this potential disadvantage to large achenes compensated for by increased pappus investment? Does smaller achene mass reduce seedling fitness, and is this potential disadvantage to small achenes compensated for by increased relative growth rate (RGR)?2. Dispersal ability was measured as fall rate in still air, while seedling fitness was measured as dry mass at two ages for 21 populations belonging to nine subspecies.3. Fall rate was positively correlated with achene plume loading−1/2, but because of variation in pappus investment and geometry, both plume loading−1/2 and fall rate were only weakly positively correlated with achene mass. Relative pappus investment did not show a consistent increase with achene mass.4. Seedling dry mass was strongly positively correlated with achene mass for 2‐week‐old seedlings grown without added nutrients. This correlation was significant but weak with added nutrients at 2 weeks, and by 4 weeks it was no longer significant. Seedling RGR was strongly negatively correlated with achene mass.5. Achene mass variation was related to both seedling fitness and dispersal ability, but compensation was evident mainly as faster RGR in populations with small achenes.
Relationships between leaf lifespan and structural defences in a low‐nutrient, sclerophyll flora
Authors: Wright I. J. , Cannon K. 
Published: March 2003

Summary The spectrum between species with low leaf mass per area (LMA), short‐lived leaves and high photosynthetic rate to those with high LMA, long‐lived leaves and low photosynthetic rate is one of the major spectra of variation between plant species, and is of particular relevance to the ‘carbon‐gain strategy’ of plants. In this study the relationship between physical properties of leaves and their lifespan was quantified for 17 sclerophyllous species from a nutrient‐poor woodland in eastern Australia. Fracture properties of leaves (force of fracture, tissue toughness) and other leaf traits [LMA, thickness, dry‐matter content (DMC), leaf area] were measured for each species and evaluated as predictors of leaf lifespan in cross‐species and phylogenetic analyses, and for intercorrelation with one another. The LMA, mean force of fracture, leaf thickness and leaf area each explained approximately 30–40% of variation in leaf lifespan. Leaf toughness explained 25% of variation in leaf lifespan, and DMC 12%. Leaf toughness and DMC were correlated with each other, but not with leaf thickness. Leaf thickness and toughness were related closely to LMA, while DMC and LMA were only marginally correlated. Nutrients can be withdrawn prior to leaf death and redeployed elsewhere in the canopy when leaf death is initiated by a plant. However, when control is external to the plant these nutrients are lost. There may be advantages to increasing defence to give a high likelihood that the plant has control over the timing of leaf death.
Life‐history traits of Brown Trout vary with the size of small streams
Authors: Jonsson B. , Jonsson N. , Brodtkorb E. , Ingebrigtsen P.‐J. 
Published: March 2003

Summary Brown TroutSalmo truttaL. life‐history traits were studied in 17 coastal streams with mean annual water discharges ≤1 m3 s−1, and with anadromous and freshwater resident trout present in all streams. Mean smolt length and age were positively correlated with mean annual water discharge and latitude. The variation (CV) in smolt length and age was negatively correlated with water discharge. Mean length and age at maturity were also positively correlated with mean annual water discharge. Freshwater resident females were sparse (mean: 3·7%) but males were abundant in all the investigated populations (mean 48·9%). Mean body length at maturity of resident males increased with discharge in parallel to that of the anadromous males. Mean length at maturity increased with smolt length in anadromous males, but not females. Mean sea‐age at maturity in females, but not males, was negatively correlated with smolt age. It is concluded that several life‐history traits of Brown Trout are strongly influenced by habitat variables associated with the size of small nursery streams.
Seasonal variations in the net ecosystem CO2 exchange of a mature Amazonian transitional tropical forest (cerradão)
Authors: Vourlitis G. L. , Priante Filho N. , Hayashi M. M. S. , Nogueira J. De S. , Caseiro F. T. , Holanda Campelo J. 
Published: March 2003

Summary

Tower‐based eddy covariance and measurements of the vertical CO2 concentration gradient within the canopy were used to quantify the seasonal variations in the net ecosystem CO2 exchange (NEE) of a 28–30 m tall transitional tropical forest (cerradão). The study was conducted near the city of Sinop, Mato Grosso, Brazil (11°24·75′ S; 55°19·50′ W), which is located in the ecotone of two major regional ecosystem types of South America (tropical rainforest and savanna).
The NEE during the dry season (August–September) was in balance, but during the transition period between the dry and wet seasons (October–November) the cerradão stand became a net source of 50–150 mmol m−2 day−1 CO2 to the atmosphere. Measurements during the wet season (February, April) indicate that the forest was a net sink of between −55 and −102 mmol m−2 day−1.
The NEE of the transitional tropical forest was more similar to that of tropical rainforest during the wet season, but during the dry season the NEE of the transitional forest was more similar to that reported for tropical savanna. The data suggest that seasonal variations in rainfall have important implications for the seasonal pattern of NEE in cerradão.
Differences in seed germination responses may promote coexistence of four sympatric Piper species
Authors: Daws M. I. , Burslem D. F. R. P. , Crabtree L. M. , Kirkman P. , Mullins C. E. , Dalling J. W. 
Published: March 2003

Summary

Species‐specific responses to the range of microsites resulting from canopy gap formation may contribute to coexistence in tropical forests. We investigated the effects of four factors affected by canopy gap formation (red : far‐red light, soil nitrate concentrations, soil temperature fluctuations and soil water potential) on the germination response of four pioneer Piper species (P. dilatatum, P. hispidum, P. marginatum and P. peltatum) that are typically found in canopy gaps and clearings.
All four Piper species required light for maximum germination. However, the ratio of red : far‐red light (R : FR) resulting in maximum germination varied between species. Piper peltatum will germinate in simulated understorey light conditions; P. dilatatum and P. hispidum require conditions typically found in small to medium gaps; while P. marginatum requires the conditions appropriate to large gaps.
Only P. marginatum was affected by nitrate concentration: elevated concentrations increased the germination rate. This suggests that this species could detect canopy gaps using a combination of high R : FR and elevated soil nitrate concentrations.
The germination rate of P. marginatum was least sensitive to low water potentials and high daytime temperatures characteristic of large gaps. Piper peltatum was most sensitive to these treatments, while P. dilatatum and P. hispidum were intermediate in response.
A principal components analysis of the ratios of germination in understorey to large gap conditions, for four variables, generated a significant axis that explained 88·5% of the variance in germination response between species. Differential species distribution along this axis, based on species‐specific responses, may allow germination to occur in the most suitable microsite for onward growth of the seedling and contribute to species coexistence by reducing interspecific competition.
Modelling unimodal flowering phenology with exponential sine equations
Authors: Malo J. E. 
Published: March 2003

Summary 1. This paper presents a method for modelling unimodal flowering phenology based on fitting data to an exponential sine function with a minimum number of parameters. 2. Such parameters have the advantage of being direct surrogates for the most relevant features of any phenology (start, duration, intensity, skewness and length of the tails). 3. The use of the proposed function is exemplified using flowering data collected from populations of five Cistaceae species (four from the genus Cistus and one from Halimium). 4. The fitted models account for a large part (> 90%) of the variance in the data, and their parameters are easily interpreted in ecological terms.
Mussel valve discrimination and strategies used in valve discrimination by the Oystercatcher,Haematopus ostralegus
Authors: Nagarajan R. , Lea S. E. G. , Goss‐Custard J. D. 
Published: March 2003

Summary1. In 72% of a sample of common musselsMytilus edulisL. that had been attacked by ventrally hammering Oystercatchers,Haematopus ostralegusL., the mussel had been opened through the right valve rather than the left.2. In a matched sample of unopened shells, 56·5% of mussels were ventrally thinner on the right. Mussel thickness differences were unrelated to overall mussel thickness, so this proportion should apply also to opened shells even though they are on average thinner than unopened shells.3. Since Oystercatchers attack a higher proportion of mussels by the right valve than are actually thinner on the right, their preference cannot depend solely on detecting measurable differences in thickness.4. The pattern of preference can best be explained if Oystercatchers detect and attack the thinner valve in the mussel when the thickness difference between the two valves is more than a threshold of 0·036 mm, and otherwise always attack the right valve. This strategy would save 15·5% of the blows the birds would make if they attacked shells without regard to differences in valve thickness.5. The improvement in the overall net energy intake rate that could be achieved by such a valve thickness discrimination strategy was 3·6%.
A trade‐off between clutch size and incubation efficiency in the Barn Swallow Hirundo rustica
Authors: Engstrand S. M. , Bryant D. M. 
Published: March 2003

Summary

To investigate reproductive costs associated specifically with incubation for a single‐sex intermittent incubator, clutches of the Barn Swallow (Hirundo rustica Linnaeus) were manipulated in successive trios, involving reduced (n − 2), control (n) and enlarged (n + 2) clutch sizes (n is the natural clutch). All manipulated clutches were within the natural range.
Manipulations were made shortly after clutch completion and reversed immediately prior to hatching, so the costs of incubation were examined in isolation while the demands of egg‐laying and nestling rearing were maintained at natural levels.
The efficiency of incubation was dependent on clutch size: the period from laying to hatch was shortest for those incubating reduced (R), and longest for birds incubating enlarged (E) clutches (R: 14·8 ± 0·1 days, n = 28; control (C): 15·3 ± 0·3, n = 24; E: 15·6 ± 0·2 days, n = 28). Also, hatching success was higher amongst R (92%) than either C (85%) or E (81%) clutches.
There was no evidence of an incubation cost due to clutch size in terms of parental body condition, provisioning of nestlings, or in the time interval before a second clutch.
No difference was found in female nest attendance behaviour or in the decline in egg density (which could reflect water loss) according to our clutch manipulations, indicating that other factors probably underlie the effects observed.
It was shown that the number of eggs being incubated affects components of fitness in Barn Swallows, independently of laying and chick‐rearing costs. Intraseasonal costs of incubation included prolonged egg development and reduced hatching success among larger clutches but did not affect nestling growth or interclutch intervals. We suggest that an inability to maintain optimal temperature for egg development is likely to underlie the observed responses to clutch size manipulations.
Influence of venom availability on a spider's prey‐choice behaviour
Authors: Wullschleger B. , Nentwig W. 
Published: March 2003

Summary

A neotropical hunting spider, Cupiennius salei, was studied to test whether spiders optimize venom use.
A prey‐choice experiment was performed with several cockroach species. These easily accepted prey species are especially suitable for such an experiment because the LD50 varies over a range of 40. Cupiennius salei spiders had either full venom glands (control) or their venom glands were experimentally emptied by electrical milking or by allowing them to bite into a series of crickets.
Two pairs of cockroaches were used: Blatta orientalis (LD50: 0·4 nl mg−1) vs Nauphoeta cinerea (LD50: 17·5 nl mg−1) and Periplaneta australasiae (LD50: 0·75 nl mg−1) vs Periplaneta americana (LD50: 10 nl mg−1). These pairs provide a difference of 40‐fold and 10‐fold, respectively, in venom sensitivity. Cupiennius salei preferred B. orientalis significantly over N. cinerea when the venom glands were empty, but not when the full amount of venom was available. No effect was evident for the other pair, indicating that a factor of approximately 10 is too low.
We conclude that the spiders know how much venom is available in their venom glands and that they select prey items that are appropriate for the amount of venom available.
Root longevity and phenology differences between two co‐occurring savanna bunchgrasses with different leaf habits
Authors: West J. B. , Espeleta J. F. , Donovan L. A. 
Published: March 2003

SummaryAristida strictaandSchizachyrium scopariumare C4perennial bunchgrass species native toPinus palustrissavannas in the south‐eastern USA. Species differences in growth rate, tissue nutrient content and distribution suggest thatA. strictais more stress‐tolerant (sensuGrime) thanS. scoparium. In addition,A. strictaretains leaves all year, whereasS. scopariumis winter deciduous. Based on these observations, we wanted to determine (1) whether root longevity was higher forA. strictaas compared toS. scoparium; and (2) whether the leaf habits of these species had consequences for seasonal patterns of root production and death.Usingin siturhizotrons, we recorded root number and length of these species over the course of 2·5 years on flat, transparent 50 × 50 cm windows. Kaplan–Meier (product‐limit) analysis was used to produce survival functions and to estimate median lifespans for the right‐censored root longevity data. These survival functions were compared using log‐rank χ2statistics, and a proportional hazards model was used to examine the effects of season and species on the survival of each cohort. Final demographic variables were analysed usinganova.The median lifespan ofA. strictawas 777 days whereas that ofS. scopariumwas 374 days. This significant difference in median lifespan was consistent between species for all cohorts in both years. Also, coincident with winter leaf senescence, root production nearly stopped forS. scopariumwhereasA. strictaproduced roots all year. This is probably due to the winter photosynthetic capacity ofA. stricta. Root death did not exhibit any seasonal pattern in either species. A pulse of roots produced in apparent response to the 2000 drought was evident forS. scopariumbut not forA. stricta. This cohort, however, rapidly died during the dormant season, probably due to the lack of winter photosynthesis in that species.Aristida strictaandS. scopariumexhibited root production, death and longevity patterns that were predicted on the basis of ecological and leaf habit differences between them. These findings suggest species‐specific differences in performance and element cycling in these nutrient‐poor soils.
Leaf‐size divergence along rainfall and soil‐nutrient gradients: is the method of size reduction common among clades?
Authors: MDonald P. G. , Fonseca C. R. , Overton J. McC. , Westoby M. 
Published: March 2003

Summary

Ecologists have long recognized that plants occurring in areas of low rainfall or soil nutrients tend to have smaller leaves than those in more favourable regions.
Working with a large data set (690 species at 47 sites spread widely through south‐east Australia) for which this reduction has been described previously, we investigated the morphology of leaf size reduction, asking whether any patterns observed were consistent across evolutionary lineages or between environmental gradients.
Leaf length, width and surface areas were measured; leaf traits such as pubescence or lobing were also scored qualitatively. There was no correlation between soil phosphorus and rainfall across sites. Further, there was no evidence that pubescence, lobing or other traits assessed served as alternatives to reduction of leaf size at the low ends of either environmental gradient.
Leaf size reduction occurred through many combinations of change in leaf width and length, even within lineages. Thus consistent patterns in the method of leaf size reduction were not found, although broad similarities between rainfall and soil P gradients were apparent.
Sample size and the estimation of physiological parameters in the field
Authors: McNab B. K. 
Published: March 2003

Summary

Estimates of basal rate of metabolism in fruit pigeons and flying foxes, derived from the mean of individual means, were compared to the mean basal rate obtained by pooling all data into a single estimate.
Pooled estimates of basal rate differ by ≤1% of the basal rates obtained from the mean of individual means in 7 of 10 species of pigeons and 4 of 11 species of flying foxes.
The coefficient of variation of the mean of individual mean basal rates decreased with an increase in the mean number of measurements per individual, which, given that the number of measurements per individual was 8·4 in pigeons and 3·8 in flying foxes, partially accounts for the smaller coefficients in pigeons.
The maximal absolute difference between individual mean basal rates and the mean of individual means within a species decreased with an increase in the number of measurements per individual to 8, beyond which the difference remained constant.
Repeated measurements on a single individual usually gave an estimate of basal rate within 2–8% of the species’ mean when eight or more measurements were made.
. The analysis of limited samples most often occurs in the study of elusive or endangered species, when the availability of individuals for study is greatly limited.