bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimating movement and abundance of Atka mackerel (Pleurogrammus monopterygius) with tag–release–recapture data
Authors: MCDERMOTT SUSANNE F. , FRITZ L. W. , HAIST V. 
Published: September 2005

AbstractA mark–recapture experiment was conducted in Seguam Pass, Alaska, to estimate local Atka mackerel (Pleurogrammus monopterygius) abundance and to evaluate the efficacy of trawl exclusion zones around Steller sea lion (Eumetopias jubatus) rookeries. Atka mackerel were found in dense aggregations near the Aleutian Islands where they are a major prey item of endangered Steller sea lions. In 1999, 1375 tagged fish were released and a biomass of 76 679 metric tonnes (t) was estimated outside a trawl exclusion zone using a simple Petersen model. In 2000, 8773 tagged fish were released and the estimated biomasses were 117 900 t inside and 82 057 t outside the trawl exclusion zones using an integrated tagging model. Movement into the open zone was small after 107 days (0.6%), whereas movement from the open area was potentially large but highly uncertain after 107 days (81%). Our model suggests that trawl exclusion zones in Seguam Pass are effective in separating a large biomass of potential prey for Steller sea lions from the immediate effects of local fisheries. Atka mackerel do not appear to move substantially outside their local aggregations (<70 km), and they show strong habitat preferences within their local home ranges. In one instance, fish released in an area of low Atka mackerel abundance returned to their capture location about 2 miles away. Thus individual Atka mackerel may have an affinity for particular areas within their home range, perhaps resulting from adaptations to local oceanic conditions along the Aleutian Island archipelago.
Specific functional signature in soil macro‐invertebrate biostructures
Authors: HEDDE M. , LAVELLE P. , JOFFRE R. , JIMÉNEZ J. J. , DECAËNS T. 
Published: September 2005

Summary

The aim of this study was to search for specific signatures of biogenic structures (i.e. earthworm casts, termite sheathings and mound material, and ant deposits) made by 15 species of soil engineers in a Colombian savanna. We thus investigated the organic matter (OM) biochemical composition of biostructures using near infrared spectroscopy (NIRS) and its relationship with selected biological (respirometry) and chemical attributes.
We found significant differences in OM quality and potential respiration rate among biostructures. These results were attributed to production patterns of biostructures and invertebrate feeding behaviour. A multiple co‐inertia analysis was performed with NIRS, respirometry and chemical results. It separated (i) carton termite mounds, (ii) earthworm casts and organo‐mineral termite mounds and (iii) termite sheathings and ant deposits.
These results suggest that NIRS spectra might be used as ‘fingerprints’ to identify organisms responsible for soil aggregate production. Moreover, the ordination given by the co‐inertia analysis is proposed as a basis for a functional classification of soil engineers, assuming that different biostructure properties imply different effects on soil functioning.
From ancient genes to modern communities: the cellular stress response and the evolution of plant strategies
Authors: PIERCE S. , VIANELLI A. , CERABOLINI B. 
Published: September 2005

Summary

Two major plant strategy theories attempt to explain how phenotype determines community structure. Crucially, CSR plant strategy theory suggests that stress and sporadic resource availability favour conservative phenotypes, whereas the resource‐ratio hypothesis views the spatial heterogeneity of resources as selecting for optimal foraging in chronically unproductive habitats. Which view is most realistic?
The ecophysiology literature demonstrates that stress is comprised of two processes: (1) limitation of resource supply to metabolism; and (2) damage to biomembranes, proteins and genetic material (chronic stress). Thus stress is defined mechanistically as the suboptimal performance of metabolism.
Adaptations to limitation buffer metabolism against variability in external resource supply; internal storage pools are more consistent. Chronic stress elicits the same ancient cellular stress response in all cellular life: investment in stress metabolites that preserve the integrity and compartmentalization of metabolic components in concert with molecular damage‐repair mechanisms.
The cellular stress response was augmented by morphological innovations during the Silurian–Devonian terrestrial radiation, during which nutrient limitation appears to have been a principal selection pressure (sensu CSR theory).
The modern stress–tolerator syndrome is conservative and supports metabolism in limiting or fluctuating environmental conditions: standing resource pools with high investment/maintenance costs impose high internal diffusion resistances and limit inherent growth rate (sensu CSR theory).
The resource‐ratio hypothesis cannot account for the cellular stress response or the crucial role of ombrotrophy in primary succession. CSR theory agrees with current understanding of the cellular stress response, terrestrial radiation and modern adaptations recorded in chronically unproductive habitats, and is applicable as CSR classification.
Interactive effects of larval host and competition on adult fitness: an experimental test with seed beetles (Coleoptera: Bruchidae)
Authors: VAMOSI S. M. 
Published: September 2005

Summary

Resources and intensity of competition encountered during development can have significant consequences for adult fitness, yet their effects are rarely considered simultaneously. Furthermore, it is often assumed that these factors affect adult fitness only indirectly through their effects on body mass. Here, I examined the direct effects of larval host type and intensity of competition on mass at emergence and fecundity in two species of bruchid beetles (Callosobruchus spp.).
There was no effect of competition treatments on mass at emergence of C. chinensis females reared in Adzuki or Mung Beans. Controlling for body mass, there was a significant effect of competition treatment on number of eggs laid by C. chinensis females that had been reared on Mung Beans, with those reared with a competitor laying significantly fewer eggs than females that had been reared in the absence of competition. Competition had a highly significant effect on mass at emergence of C. maculatus females reared in Mung Beans. In the absence of a significant effect of competition on mean mass at emergence in Adzuki Beans, females reared with two competitors laid significantly fewer eggs than did females reared with either one or no competitors.
For certain combinations of bruchid species and resource type, thus, females laid fewer eggs for a given mass at emergence if they had been subject to competition during their larval phase. These results reveal subtle differences in the responses of closely related species with similar life histories to resources and competition during development, calling into question current generalizations about the direct effects of competition on fitness.
Evolutionarily stable investment in secondary defences
Authors: BROOM M. , SPEED M. P. , RUXTON G. D. 
Published: September 2005

Summary

Previous workers have suggested that the evolutionarily stable strategy (ESS) for investment in antipredator defences, such as toxins, will critically depend on the nature of expression of the defence. Specifically, it has been suggested that if the different levels of a defence are best described as a continuous variable, then this will lead to pure ESSs with all individuals in a population adopting similar defence levels; whereas defences that can only take on discrete levels will lead to mixed ESSs (featuring variation in defence within the population).
Our principal aim is to determine the validity of these viewpoints, and examine how the pure and mixed strategies predicted by the two types of defences can be reconciled with practical and philosophical difficulties in defining any given defence unambiguously as continuous or discrete.
We present the first model of a continuously varying defence that is solved explicitly for evolutionarily stable strategies.
We are able to demonstrate analytically, that the model always has a unique ESS, which is always pure. This strategy may involve all members of the population adopting no defence, or all members of the population making the same non‐zero investment in defence.
We then modify our model to restrict the defence to a number of discrete levels and demonstrate that the unique ESS in this case can be either pure or mixed. We further argue that the mixed ESS can be a combination of no more than two defence levels, and the two levels in a mixed ESS must be nearest neighbour levels in an ordered list of the levels that the defence can take.
This, in turn, means that the mixed ESS will be practically identical to a pure ESS if the discrete defence is fine‐grained.
Natural temperature variation affects larval survival, development and Hsp70 expression in a leaf beetle
Authors: McMILLAN D. M. , FEARNLEY S. L. , RANK N. E. , DAHLHOFF E. P. 
Published: September 2005

SummarySierra Nevada populations of the beetleChrysomela aeneicollisexperience extreme high and low temperatures during summer, which pose special challenges to larvae of limited mobility. In these populations, allele frequency variation at the glycolytic enzyme locus phosphoglucose isomerase (PGI) correlates with differences in temperature between river drainages. PGI allozymes differ in functional properties, and thermal tolerance of adults and larvae depends on PGI genotype.We measured effects of temperature on larval development rate and survival after reciprocal transplantation of populations between drainages. Effects of temperature on growth rate and activity were determined after laboratory acclimation of larvae from Bishop Creek (BC), where PGI alleles 1 and 4 occur in similar frequency. Hsp70 expression levels were measured for free‐living larvae of known body temperature, and for laboratory‐acclimated BC larvae.Larval mortality was greatest in the coldest drainage and was correlated with minimum night‐time air temperature. The frequency of PGI allele 1 declined for BC larvae transplanted to the warmest drainage. Development rate of BC larvae in nature was lowest for experimental groups where PGI‐1 allele frequency was highest. Larval growth and activity varied with acclimation temperature and PGI genotype in the laboratory. Hsp70 expression levels in nature were higher for larvae collected later in the day, and varied consistently among PGI genotypes in nature and in the laboratory.These results suggest that daytime temperatures routinely experienced by larvae cause elevated Hsp70 expression levels indicative of physiological stress. Exposure to subzero night‐time temperatures appears to cause larval mortality. Up‐regulation of Hsp70 may protect larvae from heat and cold stress. Variation in Hsp70 expression among PGI genotypes may result in differential mortality and developmental rates in nature.
How feather colour reflects its melanin content
Authors: McGRAW K. J. , SAFRAN R. J. , WAKAMATSU K. 
Published: September 2005

Summary

Melanin coloration is the most common type of colour in animals. Many species use melanin‐based black, brown, grey or earth‐toned colours as intraspecific signals of quality.
Melanin comes in two main forms in vertebrates – eumelanin and phaeomelanin – and these are said to create different colours, with eumelanin giving a darker black, brown or grey appearance and phaeomelanin a lighter reddish or buff hue.
However, the few studies that have examined the melanin content of animal colours, namely from bird feathers, have shown that both phaeomelanin and eumelanin are present in nearly all melanized patches. These pigment types also have different synthetic origins and may be differentially costly to display.
Thus, to fully understand the costs and benefits of melanic colours, we must first quantitatively determine the relationship between pigment composition and colour characteristics.
We studied melanin content and colour variation in the ventral chestnut‐coloured plumage of male and female Barn Swallows (Hirundo rustica erythrogaster) from North America.
Total melanin concentration explained significant variation in the hue, saturation and brightness of male breast plumage and female breast plumage. Eumelanin is the predominant type in these feathers, constituting over 75% of total melanins. Eumelanin and phaeomelanin concentration were significantly positively correlated in the feathers of females but not males.
In both sexes, levels of both eumelanin and phaeomelanin concentrations were significantly and positively correlated with hue, saturation and brightness. In males but not females, however, the ratio of eumelanin‐to‐phaeomelanin was also an important predictor of colour, with smaller ratios conferring browner hues. Males also deposit more phaeomelanins, but not eumelanins or total melanins, in breast feathers than do females. These results suggest that phaeomelanin plays a unique role in the colouring strategy of male Barn Swallows.
Aggregation in juvenile pike (Esox lucius): interactions between habitat and density in early winter
Authors: HAWKINS L. A. , ARMSTRONG J. D. , MAGURRAN A. E. 
Published: September 2005

SummaryJuvenile pike (Esox lucius), a cannibalistic fish species, aggregates within habitat patches. The advantages to cannibals of aggregating in the absence of other predators and food constraints are not immediately obvious. In this study we explore the basis for this grouping by observing how spatial distributions of juvenile pike are mediated by the presence of conspecifics.Solitary pike preferred shallow‐water (0·17 m depth) habitats. When fish density was increased, the average time spent in alternative deep‐water habitat (0·33 m) increased, consistent with a despotic type of distribution and suggesting that interference was occurring.In pairs of fish, one pike, nominally the dominant individual, showed a habitat use similar to that of single fish. The second individual mostly occupied deep water, again consistent with a despotic distribution and apparently mediated by intimidation interference. However, dominant pike did on occasion enter deep water, at which times the subordinate pike remained with the dominant fish, appearing to aggregate in the pool.We propose that habitat‐specific risk could explain aggregations of pike in deep water. Although remaining in close proximity to dominant individuals in deep water would seemingly put subordinate fish at great risk, the alternative of moving to shallow water may increase risk still further by reducing the capacity to perceive and/or evade attacks.
Advances in molecular ecology: tracking trophic links through predator–prey food‐webs
Authors: SHEPPARD S. K. , HARWOOD J. D. 
Published: September 2005

Summary

It is not always possible to track trophic interactions between predators and prey by direct observation. This is especially true when observing small or elusive animals with cryptic food‐web ecology. Gut and/or faecal analysis can sometimes allow prey remains to be identified visually but is only possible when a component of the diet is resistant to digestion. In some cases there are no solid remains, and when there are it can lead to bias in interpretation of prey choice.
Numerous invasive and non‐invasive methods have been developed to characterize predator–prey interactions but two principal areas dominate ‘molecular’ research. These are reviewed under the headings of monoclonal antibodies and DNA‐based techniques.
Early ‘molecular’ studies of predator–prey food webs were dominated by the development of monoclonal antibodies. These methods continue to be used for mass‐screening of field‐collected arthropods for insect‐specific proteins.
The application of species‐specific primer design, polymerase chain reaction (PCR), restriction fragment length polymorphism analysis (RFLP), DNA cloning and sequencing, comparative sequence analysis (e.g. BLAST; basic local alignment search tool), high‐resolution gel electrophoresis, Temperature/denaturing gradient gel electrophoresis (TGGE/DGGE) and automated fragment analysis with fluorescent probes is reviewed. The development of molecular techniques for use in predator–prey studies is primarily limited by their cost and the development of new procedures and equipment that complement them.
Relative contribution of meristem activities and specific leaf area to shoot relative growth rate in C3 grass species
Authors: SUGIYAMA S. 
Published: September 2005

Summary

Although plant growth depends on a balance between source and sink abilities, few studies have examined how sink activities influence plant shoot growth. This study is an examination of how meristem (sink) activities influence interspecific differences in shoot relative growth rate (RGR) among 16 C3 grass species.
The RGR and specific leaf area (SLA) were measured on plants grown under controlled environments in each species. Meristem activities of the shoot were quantified by the length of leaf meristems, which was obtained by microscopic observation on mesophyll cells, and by leaf meristem density that was estimated from tiller density. There was an inverse relationship between single meristem size and meristem density among the species.
While RGR did not show a significant correlation with total meristem activity, it did show a significant correlation with SLA. These results demonstrate that the interspecific difference in shoot RGR among grass species was determined mainly by the source ability of mature leaves.
However, leaf meristem size and meristem density had a great effect on RGR through their influence on how the variation in SLA was generated. Species with large and few meristems tended to attain a large SLA through low leaf dry matter concentration, while fast‐growing species with more, smaller meristems attained a large SLA through a reduction of leaf thickness.
Developmental basis of interspecific differences in leaf size and specific leaf area among C3 grass species
Authors: SUGIYAMA S. 
Published: September 2005

Summary

Leaf size and specific leaf area (SLA) are major traits in determining a plant's ecological functions. Differences in these leaf traits are characterized by cell division, expansion and maturation processes during leaf development. In this study, 16 C3 grass species were grown under controlled environments, and various cell division and elongation parameters in the leaf growth zone were obtained by a kinematic method to examine cellular mechanisms underlying interspecific differences in leaf length and specific leaf area.
Leaf length showed a threefold difference among species. This difference in leaf length was closely associated with the number of dividing cells in the leaf meristem. Cell division activity in the leaf meristem also influenced mature cell length. Species with high levels of cell division activity had smaller mesophyll cells, mainly caused by a short cell elongation period. The fact that 70% of the variation in mature cell length was explained by cell division activity suggests that cell size determination is more strongly influenced by the developmental processes than by specific genes affecting cell size.
Cell division and elongation activities did not have clear effects on SLA. However, species with high levels of division activity had higher leaf water content and lower leaf dry matter concentration than did species with low levels of division activity.
The results of this study reveal the importance of cell‐cycle regulation in the leaf meristem in determining interspecific differences in leaf size and SLA among grass species.
Hydrochory increases riparian plant species richness: a comparison between a free‐flowing and a regulated river
Authors: JANSSON ROLAND , ZINKO URSULA , MERRITT DAVID M. , NILSSON CHRISTER 
Published: September 2005

Summary

The importance of dispersal for plant community structure is poorly understood. Previous studies have hypothesized that patterns in the distribution and genetic structure of riparian plant communities were caused by hydrochory, i.e. plant dispersal by water. We separated the relative contributions of propagules from hydrochory and other dispersal vectors by comparing colonization in pairs of plots, one subject to flooding and deposition of hydrochores and the other unflooded.
The number of colonizing individuals and the mortality rate of individuals per year did not differ significantly with flooding, but hydrochory increased the number of colonizing species per year and plot by 40–200%. The pool of colonizing species was 36–58% larger per year for flooded than for unflooded plots, indicating that hydrochory increased the diversity by facilitating long‐distance dispersal. Hydrochory resulted in more diverse plant communities after 3 years of succession at both plot and reach scales, despite the fact that flooding caused plant mortality.
We found no evidence that dams reduce the abundance and diversity of water‐dispersed propagules by acting as barriers for plant dispersal. The role of hydrochory for plant colonization was similar between a free‐flowing and a regulated river, although in fragmented rivers propagule sources are likely to be more local (within‐impoundment).
We conclude that plant dispersal by water, as well as fluvial disturbance, is important for enhancing species richness in riparian plant communities. As flowing water may carry buoyant seeds long distances, riparian plant communities may receive a comparatively large proportion of their seeds by long‐distance dispersal.
Inducible responses in the brown seaweed Ecklonia cava: the role of grazer identity and season
Authors: MOLIS MARKUS , KÖRNER JOCHEN , KO YOUNG WOOK , KIM JEONG HA , WAHL MARTIN 
Published: September 2005

Summary

Plants must either tolerate consumption or defend themselves against grazer attacks. Selection for phenotypically plastic antiherbivory responses has been suggested for many plants, including a few species of seaweed, but little is known about its specificity or seasonality.
Multi‐factorial experiments tested the effects of consumer identity (Littorina brevicula vs. Haliotis discus) and season (summer vs. autumn) on the induction of antiherbivory defences in the brown seaweed Ecklonia cava. Following a grazer‐free acclimation phase, algae were incubated with grazers (treatment phase) and, subsequently, without grazers (recovery phase). Feeding preference assays, were used to assess differences in consumption rates between grazer‐exposed and control plants.
In summer, Littorina, but not Haliotis, induced defence in Ecklonia. This defence vanished by the end of the recovery phase. In autumn, neither exposure to direct attack nor to waterborne cues induced defensive responses.
Both consumer identity and season of consumption can influence the ability of a given macroalgal species to induce antiherbivory defences. Tailoring such responses to spatial and temporal variation in grazer pressure could have profound ecological implications, for example changing food webs and community structure.