bluuebunny/crossref_metadata_2025 huggingface dataset:
Geographic patterns in the demersal ichthyofauna of the Aleutian Islands
Authors: LOGERWELL E. A. , AYDIN K. , BARBEAUX S. , BROWN E. , CONNERS M. E. , LOWE S. , ORR J. W. , ORTIZ I. , REUTER R. , SPENCER P.
Published: September 2005

The goals of this research were to investigate geographic patterns in the Aleutian Island region's demersal ichthyofauna and to determine whether they reflected the physical and biological oceanographic patterns documented by other authors in this volume. The analyses were structured according to the level of organization: at the community level, patterns in species occurrence and community structure were investigated; at the population level, distribution and abundance were examined; at the individual level, food habits and growth were studied. There were step‐changes in species occurrence, diversity, population distribution and food habits at Samalga Pass and at sites farther west. These longitudinal trends indicated physical and biological variation along the length of the Aleutian Islands chain; however, depth‐related patterns were as common as longitudinal patterns in demersal fish distribution. In addition, high catches of patchily distributed species occurred in areas expected to be biological ‘hot spots’ because of increased productivity and prey availability. These patterns suggest linkages between demersal fish ecology and the biophysical processes described by other authors in this volume and indicate that inter‐disciplinary research is needed to elucidate the underlying mechanisms.
Zooplankton distribution, abundance and biomass relative to water masses in eastern and central Aleutian Island passes
Authors: COYLE KENNETH O.
Published: September 2005

Conductivity–temperature–depth (CTD), acoustic and net samples were taken through a series of passes in the eastern and central Aleutian Island archipelago to document regional differences in the physical and biological conditions. The water column in central passes had elevated salinity and depressed temperatures, indicating upwelling of deep water through the passes. The zooplankton community included the oceanic genera Neocalanus and Eucalanus, and the euphausiid Euphausia pacifica, all oceanic taxa. Eastern passes had significantly lower salinity and elevated temperature relative to the central passes, suggesting a more neritic environment. Calanus marshallae, Pseudocalanus, Acartia and Thysanoessa inermis, common neritic species, were observed in the eastern passes. Canonical correlation indicated that up to 50% of the observed variance in mean zooplankton abundance in the passes could be explained by salinity and temperature. Elevated sound scattering was observed in fronts and eddies in the passes, particularly at the northern ends of the passes, in association with elevated zooplankton abundance and biomass. The central passes were characterized as an oceanic environment, influenced primarily by Alaskan Stream water with its associated interzonal copepod species, while the eastern passes were influenced by the Alaska Coastal Current, which contains a mixture of oceanic and neritic zooplankton species.
Tidal front affects the size of prey used by a top marine predator, the short‐tailed shearwater (Puffinus tenuirostris)
Authors: VLIETSTRA LUCY S. , COYLE KENNETH O. , KACHEL NANCY B. , HUNT GEORGE L.
Published: September 2005

Oceanographic features are known to influence the distribution of marine predators by affecting the abundance and distribution of their prey. We tested the hypothesis that oceanographic features also affect predator distribution by enhancing the profitability of small‐sized prey. During July and August 1999, short‐tailed shearwaters feeding in Akutan Pass, Alaska (Aleutian Islands) fed upon small (11.6 ± 0.2 mm) euphausiids present in high density near the sea surface. Conductivity–temperature–depth (CTD) casts, hydroacoustic surveys, and net tows revealed that high densities of small euphausiids were associated with a tidal front on the north side of Akutan Pass. At most sites elsewhere in the Bering Sea, away from tidal fronts, shearwaters selected larger (14.2–20.1 mm) euphausiids, even when small euphausiids were present. This study provides evidence that, by promoting high densities of easily accessible prey, oceanographic features can broaden the range of prey sizes taken by marine predators.
Corals of the Aleutian Islands
Authors: HEIFETZ JONATHAN , WING BRUCE L. , STONE ROBERT P. , MALECHA PATRICK W. , COURTNEY DEAN L.
Published: September 2005

A unique feature of the benthic habitat in the Aleutian Islands is the presence of a highly diverse and abundant coral and sponge community. These communities likely provide important habitat for a variety of fish and invertebrate species. Summaries of historical data and recent direct observations with a submersible indicate that the Aleutian Islands may harbour the highest diversity and abundance of coldwater corals in the world. There are 69 documented taxa (species and subspecies) of coral in the Aleutians of which 25 are endemic. Within the Aleutian Islands, there is an increase in diversity of corals west of about longitude 169°W. This shift in diversity is consistent with the hypothesis of an ecological boundary in the vicinity of Samalga Pass. Given the endemism and high diversity and abundance of corals in the Aleutians, there is evidence that this region is the evolutionary centre of origin for some taxa of coldwater corals.
Oceanography and ecology of the Aleutian Archipelago: spatial and temporal variation
Authors: HUNT GEORGE L. , STABENO PHYLLIS J.
Published: September 2005

This compilation of new information and summaries of earlier work emphasizes variability within marine waters of the Aleutian Archipelago. From the Alaska Peninsula to Near Strait, net flow through the passes is northward, with four passes (Amukta, Amchitka, Buldir, and Near Strait) contributing most of the flow. East of Samalga Pass (169°W), waters derived from the Alaska Coastal Current predominate, whereas west of Samalga Pass, waters of the Alaskan Stream predominate. The pattern of storm tracks creates a climatological (interannual and long term) transition zone in weather features (e.g. surface air temperature) near 170°W. The marine ecosystem of the Aleutian Archipelago also has a strong discontinuity at Samalga Pass, where cold‐water corals, zooplankton, fish, marine mammals and foraging seabirds show a step change in species composition. Diets of ground fish, Steller sea lions (Eumetopias jubatus) and some seabirds also change there. Lower growth rates of some fish species and stable isotope data indicate that productivity declines westward along the archipelago. The available data demonstrate considerable ecosystem variability over time scales of decades to millennia. Abrupt changes in composition of fish communities at several of the major passes suggest that Samalga Pass may mark only one of several ecological divisions of Aleutian waters. This spatial and temporal heterogeneity provides an important context within which to view recent declines in populations of Steller sea lions and other species, and has important implications for the management of regional marine resources. We conclude that the marine waters of the Aleutian Archipelago are divided into at least two different ecological regions, with potential for a concomitant separation of some fishery resources.
Immature Steller sea lion (Eumetopias jubatus) dive activity in relation to habitat features of the eastern Aleutian Islands
Authors: FADELY BRIAN S. , ROBSON BRUCE W. , STERLING JEREMY T. , GREIG ANGIE , CALL KATHERINE A.
Published: September 2005

Current flow and bathymetry in the Aleutian Islands define unique habitats that influence prey distribution and foraging behaviour of top‐level predators. We explored whether oceanographic features and bathymetry influenced the diving activity of 30 immature sea lions (ages 5–21 months) equipped with satellite‐linked depth recorders in the eastern Aleutian Islands (EAI) during 2000–02. Sea surface temperature (SST) and chlorophyll a concentrations were obtained from remote sensing satellite imagery and associated with locations where sea lion diving was recorded. Most locations associated with diving to >4 m were within 10 nautical miles (nm) of shore and associated with onshelf waters <100 m deep. Use of offshore and deeper waters in the Bering Sea increased during May, as did trip durations. General movements at that time were generally northwesterly from the North Pacific Ocean to the Bering Sea. Diving activity varied coincidently with increases in SST and chlorophyll a concentrations, but also with sea lion age. Associations with habitat features did not consistently explain variability in dive count, time at depth, dive focus or focal depth. Nearshore diving tended to be influenced by distance from shore or seafloor depth, whereas increased SST coincided with activity of sea lions diving >30 nm offshore. Immature sea lions developing into independent foragers in the relatively shallow pass areas of the EAI do so at a time of rapid changes in oceanography and prey availability.
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

A 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

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

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

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

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

Sierra 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

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

Juvenile 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

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

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

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

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

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.
Abundance and flowering success patterns in a short‐term grazed grassland: early evidence of facilitation
Authors: BOSSUYT B. , DE FRÉ B. , HOFFMANN M.
Published: September 2005

Associational resistance is a grazing avoidance mechanism resulting from herbivores being less inclined to eat palatable plant species when these species grow in association with unpalatable species. Such facilitative interactions between plant species may have important consequences for patterns of relative abundance and reproduction in plant communities.

We studied the relationship between abundance and flowering success of palatable species and the cover of three unpalatable species (Senecio jacobaea, Iris pseudacorus and Lysimachia vulgaris) in a grassland where moderately intense grazing (0.17–0.42 grazers ha−1) had been ongoing for 3 years. Plots were selected so that there were no systematic differences in microenvironmental conditions associated with the level of cover of unpalatable species.

Several palatable species had a higher frequency, cover and/or flowering success when they grew in the neighbourhood of an unpalatable species.

Several species (both palatable and unpalatable) were significantly taller in the vicinity of a large unpalatable species, probably due to the combined effects of grazing avoidance and increased light competition.

These facilitative effects, however, have not yet resulted in a higher local species richness or plant community evenness. It is nevertheless likely that more pronounced effects will be seen if grazing is continued, because facilitative interactions between plant species induced by grazing have already led to a shift in patterns of abundance and flowering success.
Regulation of the Pituitary Growth Hormone‐Releasing Hormone Receptor in Ageing Male and Female LOU Rats: New Insights into Healthy Ageing
Authors: Veyrat‐Durebex C. , Alliot J. , Gaudreau P.
Published: September 2005

Ageing is characterised by a decrease of somatotroph functionality, involving growth hormone‐releasing hormone receptor (GHRH‐R). The present study was conducted in LOU/C/jall (LOU) rats, a strain described as a model of healthy ageing, which is characterised by a low adiposity and long life expectancy without developing severe pathologies. Effects of age and diet (chow versus self‐selection), on levels of anterior pituitary GHRH‐R mRNA transcripts, were assessed in male and female LOU rats. The effect of age on pituitary GHRH‐R functionality was examined in the anterior pituitary of both males and females fed chow diet. Moreover, serum insulin‐like growth factor‐I (IGF‐I), T4 and leptin were measured because changes in their concentration could affect GHRH‐R expression. In the pituitary of 18‐month‐old male and female LOU/C/jall rats fed standard chow, the level of 2.5‐kb GHRH‐R mRNA transcript, coding for functional GHRH‐R, was significantly decreased. In 24‐ to 34‐month‐old males and females, it progressively returned to the level of younger animals, suggesting an enrichment of the group with survivors maintaining functional GHRH‐R. In males and females repeatedly submitted to self‐selection, this phenomenon was not observed. Studies with the GHRH‐R agonist, Fluo‐GHRH, revealed that 73% of 16–18‐month‐old male and female rats studied did not show an increase of fluorescence density characteristic of receptor‐mediated internalisation upon incubation at 37 °C. In the other 27%, the increase of fluorescence was identical to that observed in pituitaries of young rats, suggesting the presence of an optimal level of functional GHRH‐R. Serum levels of leptin, free T4 and total IGF‐I decreased more drastically in ageing males and in rats fed a self‐selection diet. A positive correlation was demonstrated between leptin and IGF‐I levels in ageing males and females fed standard chow and ageing females submitted to a self‐selection regimen. In conclusion, healthy ageing in LOU rats fed chow diet appears to be associated with a maintenance of functional pituitary GHRH‐R levels found in younger rats but not necessarily with those of serum leptin, T4 and IGF‐I.
Effect of Rolipram, a Phosphodiesterase IV Inhibitor, on Allergic Footpad Swelling using Various Adjuvants in Mice
Authors: Yamaki K. , Alam A. H. M. K. , Hossain Md. A. , Taneda S. , Yanagisawa R. , Takano H. , Yoshino S.
Published: September 2005

We studied the effect of rolipram, a phosphodiesterase (PDE) IV inhibitor, on allergic footpad swelling in mice. For this study, varying adjuvants including complete Freund's adjuvant (CFA), incomplete Freund's adjuvant (IFA) and Imject Alum (Alum) were used because the extent of antigen‐specifically induced T helper type 1 (Th1) and Th2 responses had been shown to depend on adjuvants used. To induce allergic footpad swelling, we immunized mice with ovalbumin (OVA) emulsified in either CFA or IFA, dissolved in Alum or in phosphate‐buffered saline (PBS) as a control (day 0), followed by subcutaneous injection of the antigen into footpads on day 21. Rolipram was given orally to the animals daily from days 0–20. Results showed that treatment with rolipram was followed by an increase in early swelling at 0.5 h and a decrease in late swelling at 6 and 24 h in the CFA group. In the IFA group, rolipram significantly enhanced swelling at, but not after, 30 min. In the Alum and the PBS groups, the PDE inhibitor failed to affect the OVA‐specific footpad reaction at all times examined. Treatment of the CFA and IFA groups with rolipram significantly inhibited the production of the Th1 antibody anti‐OVA immunoglobulin G2a (IgG2a), and the drug enhanced Th2 cell‐dependent anti‐OVA IgE production. In both groups, rolipram also enhanced the secretion of Th2 cytokines including interleukin‐4 (IL‐4) and IL‐10. These findings suggest that rolipram may facilitate early allergic footpad swelling mediated by Th2 immune responses, while the late phase of swelling associated with Th1 responses may be attenuated by the PDE IV inhibitor.
A Commentary on the Zinkernagel–Hengartner ‘Credo 2004’
Authors: Cohn M.
Published: September 2005

In ‘Credo 2004’, Zinkernagel and Hengartner give us a food‐for‐thought analysis of immune responsiveness based on a ‘pragmatic and empiric point of view.’ The Credo 2004 postulates derived by inductive extrapolation from observation to generalization do not satisfactorily account for immune behaviour because they lack a conceptualization as illustrated here. Nevertheless, Credo 2004 is certainly valuable in a limited framework because it is based on the most likely of assumptions namely that the immune system was evolutionarily selected to protect against infectious agents, and therefore the study of pathogens will most accurately reveal how the immune system responds normally to protect. After reformulating them, the postulates of Credo 2004 are analysed with respect to their generality.
Metabolic engineering of proanthocyanidins by ectopic expression of transcription factors in Arabidopsis thaliana
Authors: Sharma Shashi B. , Dixon Richard A.
Published: September 2005

Genetic transformation of Arabidopsis thaliana with the Arabidopsis TT2 MYB transcription factor resulted in ectopic expression of the BANYULS gene, encoding anthocyanidin reductase, AHA10 encoding a P‐type proton‐pump and TT12 encoding a transporter involved in proanthocyanidin biosynthesis. When coupled with constitutive expression of PAP1, a positive regulator of anthocyanin biosynthesis, TT2 expression in Arabidopsis led to accumulation of proanthocyanidins, but only in a subset of cells in which the BANYULS promoter is naturally expressed. Ectopic expression of the maize Lc MYC transcription factor weakly induced AHA10 but did not induce BANYULS, TT12 or accumulation of proanthocyanidins. However, high‐level combined expression of TT2, PAP1 and Lc resulted in proanthocyanidin synthesis throughout young leaves and cotyledons, followed by death of the plants 1 to 2 weeks after germination. We discuss these results in relation to engineering proanthocyanidins to improve the quality of food and forage plants.
Immediate‐early and delayed cytokinin response genes of Arabidopsis thaliana identified by genome‐wide expression profiling reveal novel cytokinin‐sensitive processes and suggest cytokinin action through transcriptional cascades
Authors: Brenner Wolfram G. , Romanov Georgy A. , Köllmer Ireen , Bürkle Lukas , Schmülling Thomas
Published: September 2005

Cytokinins are hormones that regulate many developmental and physiological processes in plants. Recent work has revealed that the cytokinin signal is transduced by two‐component systems to the nucleus where target genes are activated. Most of the rapid transcriptional responses are unknown. We measured immediate‐early and delayed cytokinin responses through genome‐wide expression profiling with the Affymetrix ATH1 full genome array (Affymetrix Inc., Santa Clara, CA, USA). Fifteen minutes after cytokinin treatment of 5‐day‐old Arabidopsis seedlings, 71 genes were upregulated and 11 genes were downregulated. Immediate‐early cytokinin response genes include a high portion of transcriptional regulators, among them six transcription factors that had previously not been linked to cytokinin. Five plastid transcripts were rapidly regulated as well, indicating a rapid transfer of the signal to plastids or direct perception of the cytokinin signal by plastids. After 2 h of cytokinin treatment genes coding for transcriptional regulators, signaling proteins, developmental and hormonal regulators, primary and secondary metabolism, energy generation and stress reactions were over‐represented. A significant number of the responding genes are known to regulate light (PHYA, PSK1, CIP8, PAT1, APRR), auxin (Aux/IAA), ethylene (ETR2, EIN3, ERFs/EREBPs), gibberellin (GAI, RGA1, GA20 oxidase), nitrate (NTR2, NIA) and sugar (STP1, SUS1) dependent processes, indicating intense crosstalk with environmental cues, other hormones and metabolites. Analysis of cytokinin‐deficient 35S:AtCKX1 transgenic seedlings has revealed additional, long‐lasting cytokinin‐sensitive changes of transcript abundance. Comparative overlay‐analysis with the software tool mapman identified previously unknown cytokinin‐sensitive metabolic genes, for example in the metabolism of trehalose‐6‐phosphate. Taken together, we present a genome‐wide view of changes in cytokinin‐responsive transcript abundance of genes that might be functionally relevant for the many biological processes that are governed by cytokinins.
The tobacco plastid accD gene is essential and is required for leaf development
Authors: Kode Vasumathi , Mudd Elisabeth A. , Iamtham Siriluck , Day Anil
Published: September 2005

Angiosperm plastid genomes typically encode approximately 80 polypeptides, mainly specifying plastid‐localized functions such as photosynthesis and gene expression. Plastid protein synthesis and expression of the plastid clpP1 gene are essential for development in tobacco, indicating the presence of one or more plastid genes whose influence extends beyond the plastid compartment. The plastid accD gene encodes the β‐carboxyl transferase subunit of acetyl‐CoA carboxylase and is present in the plastids of most flowering plants, including non‐photosynthetic parasitic plants. We replaced the wild‐type accD gene with an aadA‐disrupted mutant allele using homologous recombination. Persistent heteroplasmy in the presence of antibiotics indicated that the wild‐type accD allele was essential. The phenotype of the accD knockout was revealed in plastid transformants grown in the absence of antibiotics. Leaves contained pale green sectors and lacked part or all of the leaf lamina due to arrested division or loss of cells. Abnormal structures were present in plastids found in mutant plants, indicating that accD might be required to maintain the plastid compartment. Loss of the plastid compartment would be expected to be lethal. These results provide genetic evidence showing the essential role of plastid ACCase in the pathway leading to the synthesis of products required for the extra‐plastidic processes needed for leaf development.
Oleate desaturase enzymes of soybean: evidence of regulation through differential stability and phosphorylation
Authors: Tang Guo‐Qing , Novitzky William P. , Carol Griffin H. , Huber Steven C. , Dewey Ralph E.
Published: September 2005

The endoplasmic reticulum‐associated oleate desaturase FAD2 (1‐acyl‐2‐oleoyl‐sn‐glycero‐3‐phosphocholine Δ12‐desaturase) is the key enzyme responsible for the production of linoleic acid in non‐photosynthetic tissues of plants. Little is known, however, concerning the post‐transcriptional mechanisms that regulate the activity of this important enzyme. The soybean genome possesses two seed‐specific isoforms of FAD2, designated FAD2‐1A and FAD2‐1B, which differ at only 24 amino acid residues. Expression studies in yeast revealed that the FAD2‐1A isoform is more unstable than FAD2‐1B, particularly when cultures were maintained at elevated growth temperatures. Analysis of chimeric FAD2‐1 constructs led to the identification of two domains that appear to be important in mediating the temperature‐dependent instability of the FAD2‐1A isoform. The enhanced degradation of FAD2‐1A at high growth temperatures was partially abrogated by treating the cultures with the 26S proteasome‐specific inhibitor MG132, and by expressing the FAD2‐1A cDNA in yeast strains devoid of certain ubiquitin‐conjugating activities, suggesting a role for ubiquitination and the 26S proteasome in protein turnover. In addition, phosphorylation state‐specific antipeptide antibodies demonstrated that the Serine‐185 of FAD2‐1 sequences is phosphorylated during soybean seed development. Expression studies of phosphopeptide mimic mutations in yeast suggest that phosphorylation may downregulate enzyme activity. Collectively, the results show that post‐translational regulatory mechanisms are likely to play an important role in modulating FAD2‐1 enzyme activities.
Use of genomic history to improve phylogeny and understanding of births and deaths in a gene family
Authors: Sampedro Javier , Lee Yi , Carey Robert E. , DePamphilis Claude , Cosgrove Daniel J.
Published: September 2005

Polyploidy events have played an important role in the evolution of angiosperm genomes. Here, we demonstrate how genomic histories can increase phylogenetic resolution in a gene family, specifically the expansin superfamily of cell wall proteins. There are 36 expansins in Arabidopsis and 58 in rice. Traditional sequence‐based phylogenetic trees yield poor resolution below the family level. To improve upon these analyses, we searched for gene colinearity (microsynteny) between Arabidopsis and rice genomic segments containing expansin genes. Multiple rounds of genome duplication and extensive gene loss have obscured synteny. However, by simultaneously aligning groups of up to 10 potentially orthologous segments from the two species, we traced the history of 49 out of 63 expansin‐containing segments back to the ancestor of monocots and eudicots. Our results indicate that this ancestor had 15–17 expansin genes, each ancestral to an extant clade. Some clades have strikingly different growth patterns in the rice and Arabidopsis lineages, with more than half of all rice expansins arising from two ancestral genes. Segmental duplications, most of them part of polyploidy events, account for 12 out of 21 new expansin genes in Arabidopsis and 16 out of 44 in rice. Tandem duplications explain most of the rest. We were also able to estimate a minimum of 28 gene deaths in the Arabidopsis lineage and nine in rice. This analysis greatly clarifies expansin evolution since the last common ancestor of monocots and eudicots and the method should be broadly applicable to many other gene families.