bluuebunny/crossref_metadata_2025 huggingface dataset:
Inter‐tree variation and yearly fluctuation in the susceptibility of Sakhalin spruce Picea glehnii, to shoot‐boring sawfly Pleroneura piceae
Authors: Masaka Kazuhiko , Hara Hideho
Published: August 2010

This study evaluated the effect of inter‐tree variation in the bud phenology of Picea glehnii on susceptibility to the shoot‐boring sawfly. Pleroneura piceae, and found that individual susceptibility fluctuates from year to year. The mechanism for the fluctuation between 1994 and 1997 is discussed.

Inter‐tree difference in the time of bud swelling is probably genetically based, since most of the trees that began to swell early in 1995 also swelled early in 1997, and those that began to swell late also did so in both years. Damage severity of each tree was evaluated by damage ratio: proportion of the number of damaged current shoots on the previous year's leader shoot. The rank of the bud swelling phenology of a tree was positively correlated to the rank of the damage ratio. This means that genetically based differences in phenology could explain why some trees are subjected to higher levels of herbivory than others.

There was year‐to‐year variation in the damage severity for each tree. Nevertheless, no significant differences were found in the rank of the damage ratio between years. However the standard deviation of the damage ratios of each tree was highest for trees of intermediate rank. The skew of the frequency distribution of damage ratio was negatively correlated to the cumulated daily mean temperature in spring, which means that the spruce is more susceptible to the sawfly in warm springs than in cool springs.

The mean growth rate of the lightly damaged trees increased constantly, while that of the heavily damaged trees seemed to reach a limit and then became lower than that of the lightly damaged trees.
Habitat constraints and spatial bias in seabird colony distributions
Authors: Scott Forbes L. , Jajam Martin , Kaiser Gary W.
Published: August 2010

What governs the size and location of seabird colonies has long intrigued population ecologists. Previous analysis of the distribution of colonies of four European seabirds revealed a spatial bias ‐ large colonies occurred farther apart than expected by chance alone ‐ suggesting that intraspecific competition for food supplies during breeding may regulate colony size. Here we use computer intensive statistics to show that a similar spatial bias exists in three burrow‐nesting seabirds ‐ Cassin's auklet Ptychoramphus aleuticus, rhinoceros auklet Cerorhinca monoccrata, and ancient murrelet Synthliboramphus antiquns‐ nesting off the Pacific coast of Canada. Local habitat constraints explain much of the existing spatial bias: large colonies cannot fit on small islands, and large islands suitable for colonies tended to occur far apart. However, a residual spatial bias still remained for ancient murrelets and Cassin's auklets (but not rhinoceros auklets) after habitat constraints are built into the analysis, for which intraspecific food competition remains a plausible explanation.
Are there saproxylic beetle species characteristic of high dead wood connectivity?
Authors: Schiegg Karin
Published: August 2010

Saproxylic beetles have been shown to be vulnerable to within‐forest fragmentation expressed as large distances between single dead wood pieces (low spatial connectivity of dead wood). From samples of a two‐year study of saproxylic beetles, species that were characteristic of sites with high dead wood connectivity were identified by Canonical Correspondence Analysis, the method of Dufrêne and Legendre (IndVal) and by considering the species occurring exclusively in sites with high dead wood connectivity. These species differed mainly from the other species by their high habitat specificity. Hence, there arc species‐specific responses of saproxylic beetles to the spatial arrangement of dead wood. High dead wood connectivity must be achieved in managed forests to sustain species which are particularly vulnerable to fragmentation.
Longitudinal structure, density and production rates of a neotropical stream fish assemblage: the river Ubatiba in the Serra do Mar, southeast Brazil
Authors: Mazzoni Rosana , Lobón‐Cerviá Javier
Published: August 2010

Spatio‐temporal variations in the structure, density, biomass and production rates of fish were assessed in the neotropical River Ubatiba (Serra do Mar, southeast Brazil). Electrofishing techniques and the length‐frequency method were shown to be reliable for the assessment of (ish numbers and production rates in these running waters of medium conductivity. Eighteen fish species of small size and prolonged spawning period were broadly distributed throughout the river catchment. Over the year, the assemblage structure was persistent along the river. Water column omnivore and algae/detritivore species dominated in density (15086‐70330 ind. ha−1), whereas three omnivores and a piscivorous species accounted for 70% of the production (51.5‐250.4 kg ha−1 yr−1). Comparison of production rates among, tropical, temperate and Mediterranean stream fish assemblages indicate lower rates in tropical streams and an inverse relationship between production and species diversity, lower production rates in high‐diversity tropical streams vs higher rates in low‐diversity Mediterranean streams, with intermediate rates in temperate streams of intermediate diversity.
Ecological significance of litter redistribution by wind and snow in arctic landscapes
Authors: Fahnestock J. T. , Povirk K. L. , Welker J. M.
Published: August 2010

During winter in the Arctic, plant litter is scoured from exposed hills and ridges by wind and snow and is redistributed to other portions of the landscape. The aim of this research was to quantify the physical and biological consequences of this litter redistribution. Litter biomass accumulation was ten times greater in areas of high deposition (e.g. snow drifts) than in areas of low deposition. Spring snow melt was delayed by several days and soils were cooler throughout the growing season and throughout winter in areas of increased litter deposition than areas with no litter. Photosynthetically active radiation (PAR) was reduced to near zero with small accumulations of litter. Annual C and N inputs from allochthonous litter were 143 g Cm‐2 and 14 g Nm in high lilter areas and 3.4 g C m−2and 0.3 g Nm‐2in non‐drift, ambient litter deposition areas. Although PAR and soil temperatures were significantly reduced with increased litter deposition, we did not observe significant delays in key plant phenological events of several species or measure a decrease in gross ecosystem photosynthesis. We did measure a significant increase in ecosystem respiration with increased litter deposition, which resulted in a shift in the net C balance of dry heath tundra from near zero with no litter to a net source of CO2to the atmosphere. Our study indicates that the redistribution of litter by wind and snow during winter is an important mechanism of nutrient transfer across the arctic landscape and that allochthonous litter inputs are of great enough magnitude to alter the carbon balance of some areas of the arctic landscape.
Macroecology of a host‐parasite relationship
Authors: Vaughn Caryn C. , Taylor Christopher M.
Published: August 2010

The larvae of freshwater mussels are obligate ectoparasites on fishes while adults are sedentary and benthic. Dispersal of mussels is dependent on the movement of fish hosts, a regional process, but growth and reproduction should be governed by local processes. Thus, mussel assemblage attributes should be predictable from the regional distribution and abundance of fishes. At a broad spatial scale in the Red River drainage, USA, mussel species richness and fish species richness were positively associated; maximum mussel richness was limited by fish richness, but was variable beneath that constraint. Measured environmental variables and the associated local fish assemblages each significantly accounted for the regional variation in mussel assemblages. Furthermore, mussel assemblages showed strong spatial autocorrelation. Variation partitioning revealed that pure fish effects accounted for 15.4% of the variation in mussel assemblages; pure spatial and environmental effects accounted for 16.1% and 7.8%, respectively. Shared variation among fish, space and environmental variables totaled 40%. Of this shared variation, 36.8% was associated with the fish matrix. Thus, the variation in mussel assemblages that was associated with the distribution and abundance of fishes was substantial (> 50%), indicating that fish community structure is an important determinant of mussel community structure. Although animals commonly disperse plants and, thus, influence the structure of plant communities, our results show a strong macroecological association between two disparate animal groups with one strongly affecting the assemblage structure of the other.
Foraging behavior of an estuarine predator, the blue crab Callinectes sapidus in a patchy environment
Authors: Clark Mary E. , Wolcott Thomas G. , Wolcott Donna L. , Hines Anson H.
Published: August 2010

To define general principles of predator‐prey dynamics in an estuarine subtidal environment, we manipulated predator density (the blue crab, Callinectes sapidus) and prey (the clam, Macoma balthica) patch distribution in large field enclosures in the Rhode River subestuary of the central Chesapeake Bay. The primary objectives were to determine whether predators forage in a way that maximizes prey consumption and to assess how their foraging success is affected by density of conspecifics. We developed a novel ultrasonic telemetry system to observe behavior of individual predators with unprecedented detail.

Behavior of predators was more indicative of optimal than of opportunistic foraging. Predators appeared responsive to the overall quality of prey in their habitat. Rather than remaining on a prey patch until depletion, predators appeared to vary their patch use with quality of the surrounding environment. When multiple (two) prey patches were available, residence time of predators on a prey patch was shorter than when only a single prey patch was available. Predators seemed to move among the prey patches fairly regularly, dividing their foraging time between the patches and consuming prey from each of them at a similar rate. That predators more than doubled their consumption of prey when we doubled the number of prey (by adding the second patch) is consistent with optimizing behaviors ‐ rather than with an opportunistic increase in prey consumption brought about simply by the addition of more prey. Predators at high density, however, appeared to interfere with each other's foraging success, reflected by their lower rates of prey consumption.

Blue crabs appear to forage more successfully (and their prey to experience higher mortality) in prey patches located within 15–20 meters of neighboring patch, than in isolated patches. Our results are likely to apply, at least qualitatively, to other crustacean‐bivalve interactions, including those of commercial interest; their quantitative applicability will depend on the mobility of other predators and the scale of patchiness they perceive.
Host selection by a mycophagous fly and its impact on fly survival
Authors: Pawlitz Rachel J. , Bultman Thomas L.
Published: August 2010

Epichloë fungi interact with Botanophila flies in a co‐evolved mutualism that appears to be analogous to angiosperm pollinator‐parasite systems. Female flies act as vectors of fungal spores as they lay eggs on the fungi which grow within and on grass stems. To understand selective pressures operating on choice of host fungi by flies, we monitored the interaction of two species of Epichloë with Botanophila at two sites in southern England. At one site (Ashurst), the hosts Epichloë clarkii and Epichloë baconii co‐occurred, while at a second site (Farm Gate), only E. clarkii was present. Flies ovipositing on E. baconii showed preferences for large, somewhat isolated fungi occurring within small clumps of grass. Flies ovipositing on E. clarkii at the Ashurst site did not select hosts based on any physical features of fungi that we measured. However, flies ovipositing on E. clarkii at the Farm Gate site tended to prefer large fungi that occurred within small clumps of grass. Fungal characteristics preferred by the flies showed no correlation with egg/larval survivorship. Insect survival on E. clarkii varied between sites and was related to differences in egg dispersion among fungi at the two sites. The absence of an alternate host (E. baconii) was associated with greater aggregation of eggs on E. clarkii at the Farm Gate site and these insects experienced higher levels of mortality at this compared to the other site.
Summer bird abundance and distribution on set‐aside fields on intensive arable farms in England
Authors: Henderson Ian G. , Vickery Juliet A. , Fuller Robert J.
Published: August 2010

The abundance and distribution of breeding birds were compared on paired fields comprising one set‐aside field and one crop field, on 11 intensive arable farms in eastern and western England. A single observer made four visits to all set‐aside and crop fields between April and July and recorded all birds seen during standardised counts and transects.

Rotational and non‐rotational set‐aside supported higher densities and more species of birds than fields of wheat, brassicas, root crops and seed rye. These differences in density, between set‐aside and crops, were evident across a suit of species including waders, gamebirds, pigeons and passerines and were particularly marked on rotational set‐aside. The majority of species recorded in fields away from boundaries would have been feeding rather than nesting there and higher bird densities on set‐aside compared with adjacent arable crops probably reflects greater food abundance in the former.

The study is the first to demonstrate a clear habitat preference for set‐aside by a wide range of bird species throughout the breeding season and it allows a number of recommendations to be made concerning the development of cost‐effective agri‐environment measures. The fact that the majority of birds utilised the outer 5 m, or in some cases 20 m, margin of the field suggests that many of the benefits of whole field set‐aside may be derived from marginal strips. A slight, but not significant preference for rotational over non‐rotational set‐aside suggest such margins should be managed to maintain a patchy, relatively diverse sward of arable plants. A key feature of set‐aside is the scale at which it has been incorporated into the arable landscape. Agri‐enviromental schemes will only provide similar national benefits if they are implemented on a wide scale in such as way as to promote high uptake by farmers.
Are spring staging brent geese evicted by vegetation succession?
Authors: van der Wal René , van Lieshout Suzan , Bos Daan , Drent Rudi H.
Published: August 2010

The number of spring staging brent geese on the salt marshes of the Dutch island of Schiermonnikoog increased from about 1500 individuals in the late 1960s to > 4000 in the late 1970s. Since then, numbers on Schiermonnikoog have levelled off, while the world population continued to increase. Although the extent of salt‐marsh area on the island has dramatically increased over the past 20 yr, the number of brent geese on Schiermonnikoog was rather constant in this period. We hypothesise that the number of geese did not increase because of successional changes in the vegetation.

On the basis of 24 yr of counts, we show that geese had to give up older parts of the marsh. Over time, tall growing species like the shrub Atriplex portulacoides have invaded, making the marsh unsuitable for goose grazing. Newly developed marsh, however, was readily exploited by the geese. The area of older salt marsh lost due to succession was almost exactly compensated for by the development of new feeding grounds. Geese which persistently utilised the older marsh were faced with a high proportion of non‐preferred species, although they still managed to assemble a diet largely composed of preferred plant species. In the older marsh, a significant reduction in the time spent foraging was also observed. We conclude that brent geese are largely excluded as vegetation succession progresses. Numbers on the island as a whole, however, are sustained due to the dynamic nature of the island. If development of new salt marshes were to be prevented, geese would be forced to abandon the salt marsh.
Sex and size related differences in the dry season feeding patterns of elephants in Chobe National Park, Botswana
Authors: Stokke Sigbjørn , du Toit Johan T.
Published: August 2010

Differences in feeding patterns of the African elephant were examined by sex and age during the dry season in a dystrophic savanna‐woodland ecosystem in northern Botswana. Adult males had the least diverse diet in terms of woody plant species, but they consumed more plant parts than family units. The diameter of stems of food plants broken or bitten off was also greater for adult males than for females and subadult males. Adult males spent more time foraging on each woody plant than did females. The number of woody plant species and individuals present were higher at feeding sites of family units than at feeding sites of adult males, indicating that family units positioned themselves at feeding sites with higher species diversity than those of males. We argue that the most likely explanation for these differences is related to the pronounced sexual size dimorphism exhibited by elephants, resulting in sex differences in browsing patterns due to the allometric relationships that govern the tolerance of herbivores for variation in diet quality. From our results this Body Size Hypothesis is accepted rather than the alternative Scramble Competition Hypothesis, which predicts that adult male elephants consume lower quality browse because they are displaced from preferred browse as an outcome of scramble competition with adult females and their offspring. If the feeding patterns of adult male elephants were affected by intersexual scramble competition, we would expect adult males to browse at a higher level in the canopy than the smaller‐bodied females and their offspring. No evidence was found for this, although adult females were found to browse at a higher level in the canopy when feeding in close proximity to subadults and juveniles than when feeding alone. Sex differences in elephant browsing patterns are, we propose, of relevance to understanding and managing elephant impacts on African woodlands.
Periodicity in spatial data and geostatistical models: autocorrelation between patches
Authors: Radeloff Volker C. , Miller Todd F. , He Hong S. , Mladenoff David J.
Published: August 2010

Several recent studies in landscape ecology have found periodicity in correlograms or semi‐variograms calculated, for instance, from spatial data of soils, forests, or animal populations. Some of the studies interpreted this as an indication of regular or periodic landscape patterns. This interpretation is in disagreement with other studies that doubt whether such analysis is valid. The objective of our study was to explore the relationship between periodicity in landscape patterns and geostatistical models. We were especially interested in the validity of the assumption that periodicity in geostatistical models indicates periodicity in landscape pattern, and whether the former can characterize frequency and magnitude of the latter. We created maps containing various periodic spatial patterns, derived correlograms from these, and examined periodicity in the correlograms. We also created non‐regular maps that we suspected would cause periodicity in correlograms. Our results demonstrate that a) various periodic spatial patterns produce periodicity in correlograms derived from them, b) the distance‐lags at which correlograms peak correspond to the average distances between patch centers, c) periodicity is strongest when the diameter of patches is equal to the distance between patch edges, d) periodicity in omni‐directional correlograms of complex spatial patterns (such as checkerboards) are combinations of several waves because inter‐patch distances differ with direction; multiple directional correlograms can decompose such complexity, and e) periodicity in correlograms can also be caused when the number of patches in a study site is small. These results highlight that correlograms can be used to detect and describe regular spatial patterns. However, it is crucial to ensure that the assumption of stationarity is not violated, i.e., that the study area contains a sufficiently large number of patches to avoid incorrect conclusions.
Ecological distribution of four co‐occurring Mediterranean heath species
Authors: Ojeda Fernando , Arroyo Juan , Marañón Teodoro
Published: August 2010

Erica australis, E. scoparia, E. arborea and Calluna vulgaris are the most abundant heath species on acid, sandstone‐derived soils of the Strait of Gibraltar region (southern Spain and northern Morocco). Despite their apparently similar ecological requirements, these four species are somewhat ecologically segregated. Erica australis is abundant only on poor, shallow soils, with a high content in soluble aluminium, generally on mountain ridges and summits. Erica scoparia becomes dominant on deeper sandstone soils with lower aluminium. Calluna vulgaris coexists with these Erica species in communities under low or no tree cover. In the Spanish side of the Strait (Algeciras), Erica arborea tends to be relegated to communities under moderate to dense tree cover, whereas this species is more abundant and widespread in the Moroccan side (Tangier). Tolerance to extreme physical conditions ‐ high aluminium and dense tree cover ‐ and interspecific competition seem to explain the ecological distribution of these four heath species in the Strait of Gibraltar region. The more fragmented pattern of sandstone patches and higher disturbance levels in Tangier might account for the differences in the patterns of ecological distribution of these four heath species between both sides of the Strait of Gibraltar.
Water mite parasitism in damselflies during emergence: two hosts, one pattern
Authors: Rolff J.
Published: August 2010

The infections of emerging damselfly cohorts by ectoparasitic water mitesArrenurus cuspidatorwere followed closely over two years in two populations. In one pondCoenagrion puellawas the single host species, whereas in the second pondC. hastulatumco‐occurred. The prevalences found were close to 100%. The mean daily abundance of mites ranged from I to 45 mites per host with a peak after roughly one third of the emergence period.

The water mites displayed a clumped distribution on their hosts measured by the variance/mean ratio. No differences in parasite abundance due to host sex, head width, or host species could be detected. The abundance of mites was synchronised with host's emergence patterns. This was stronger in the system with two host species. Shaw and Dobson recently showed a generalised relationship of variance/mean of parasite abundance combining data from 269 host parasite systems. The data presented here and some other water mite associations show a significant deviation from this general rule.
Geographical variation in blood parasites in feral pigeons: the role of vectors
Authors: Sol Daniel , Jovani Roger , Torres Jordi
Published: August 2010

Prevalence and intensity of blood parasites are known to vary in space within a same species, yet the causes underlying such variation are poorly known. Theoretically, blood parasites variation can be attributed to differences to exposure to parasite vectors and/or to differences in host susceptibility. Here, we show that prevalence ofHaemoproteus columbaein feral pigeonsColumba liviavaried among five near‐by populations (range 15%‐100%), paralleled by variation in the abundance of its main vector, the louse fliesPseudolynchia canariensis.Geographic variation in intensity of blood parasites did not covary with abundance of vectors. Within populations, older individuals had a higher probability of being parasitized than younger ones, whereas younger birds, when infected, suffered higher intensities. Furthermore, we found no evidence of sex‐related differences neither in prevalence nor in intensity of blood parasite infections. To demonstrate that geographical variation in prevalence was actually due to differences in vector exposure, we conducted two experiments based on translocation of unparasitized pigeons from a vector‐free area to an area where both the parasite and vector were abundant. With the first experiment, we demonstrated that unparasitized pigeons were not resistant to the parasite because when transmission was possible pigeons became parasitized in a few months. With the second experiment, in which half of the pigeons were prevented from contacts with the vector, we ruled out the posibility that pigeons we considered as unparasitized would have suffered from latent infections. Therefore, both observational and experimental evidence supports the view that vector abundance is the major factor influencing the spatial variation in prevalence ofH. columbaein pigeons.
Patch size and colonisation patterns: an experimental analysis using north temperate coprophagous dung beetles
Authors: Finn John A. , Giller Paul S.
Published: August 2010

The relationship between dung pad size and both adult colonisation and larval development was investigated in an assemblage of north temperate dung beetles (Geotrupes. AphodiusandSphaeridium) using both dung pads and baited pitfall traps. Wet weight of 22‐day‐old natural dung pads was found to vary widely in the field (< 100 g – >1000 g). Across all sampling dates in field experiments, dung pad size had a significant influence on dung beetle biomass sampled from pads. Closer examination of experimental dung pads on the second day after deposition, when beetle biomass was at a maximum, revealed not only a general positive relationship between pad size and dung beetle biomass but, more importantly, a positive relationship between dung pad size and dung beetle density (dung beetle biomass per unit dung volume). There was a strong trend forAphodiusspecies richness to increase, and maintain higher values for longer periods of time, in larger pads. Although dung pad and pitfall trap samples could differ in the actual numbers of beetles captured, the relationship between different dung sizes and dung beetle biomass was similar, indicating that the phenomenon is largely related to immigration processes. Pat residence times oiA. rufipesin the laboratory were significantly positively correlated with dung pad size. In two field experiments, positive correlations were found between dung pad size and numbers of larvae in pads of different sizes and in one of these experiments, larval densities (numbers per unit dung volume) were significantly and positively correlated with dung pad size. In one experiment,Aphodiuslarvae in the early stages of development were found to preferentially occupy the basal area of dung pads. We discuss the implications of our findings in the context of resource utilisation by north temperate dung beetles.
Recovery of tall cotton–grass following real and simulated feeding by snow geese
Authors: Hupp J. W. , Robertson D. G. , Schmutz J. A.
Published: August 2010

Lesser snow geese Anser caerulescens caeruteseens from the western Canadian Arctic feed on underground parts of tall cotton–grass Eriophorum angustifolium during autumn staging on the coastal plain of the Beaufort Sea in Canada and Alaska. We studied revegetation of sites where cotton–grass had been removed either by human–imprinted snow geese or by hand to simulate snow goose feeding. Aerial cover of cotton–grass at sites (n = 4) exploited by human–imprinted snow geese averaged 60 and 39 Mi lower than in undisturbed control plots during the first and second year after feeding, respectively. Underground biomass of cotton–grass stembases and rhizomes in hand–treated plots was 80 and 62% less than in control plots 2 and 4 yr after removal, respectively (n = 10 yr‐1). Aerial cover and biomass of common non‐forage species such as Carex aquatilis did not increase on treated areas. Removal of cotton‐grass by geese likely reduces forage availability at exploited sites for at least 2–4 yr after feeding but probably does not affect long‐term community composition. Temporal heterogeneity in forage abundance likely contributes to the large spatial requirement of snow geese during staging.
Nutritional consequences of a change in diet from native to agricultural fruits for the Samoan fruit bat
Authors: Nelson Suzanne L. , Miller Martin A. , Heske Edward J. , Fahey George C.
Published: August 2010

The Samoan fruit bat Pteropus samoensis Peak, an endemic flying fox that inhabits the Samoan archipelago, prefers to forage on native fruit species. This species has recently been subjected to extreme population threats including hunting and severe storms, as well as large‐scale habitat degradation. If habitat destruction continues at its present rate, P. samoensis may be forced to forage more within an agricultural matrix. In this study, we analyzed sixteen species of native fruits and four species of agricultural fruits for five organic components and eight minerals to test whether native fruits provided a higher quality diet or more varied diet than agricultural fruits. Within native fruits, we also focused on four species of figs, because these fruits are often considered an important food item for tropical frugivores. Overall, native fruits provided more variation and had higher average values for several nutrients than agricultural fruits. Native fruits were especially high in biologically important minerals (calcium, iron, and sodium), and provided up to 5 times more calcium, 10.5 times more iron, and 8 times more sodium than agricultural fruits. Figs were found to be an especially rich source of many nutrients, particularly for calcium. Thus. P. samoensis. a sequential specialist, may be better able to adjust its diet to obtain higher levels of minerals when consuming a variety of native fruits than when restricted to the consumption of only agricultural fruits. These findings suggest a need to preserve native habitat and to create parks to sustain the long term health and viability of P. samoensis.
Community composition and size structure of murid rodents in relation to the biogeography of the Japanese archipelago
Authors: Millien‐Parra Virginie , Loreau Michel
Published: August 2010

We investigated the geographical patterns of community composition and size structure of murid rodent assemblages in Japan. Rodent faunal composition showed three biogeograpbic zones in the studied area (Hokkaido, northern Honshu and southern Honshu), which are characterized by endemic species or genera. There was a large discrepancy between distribution patterns of murine species, which are generalist and widespread in Japan, and arvicoline species, which are more specialized and locally restricted. We also found a strong degree of nestedness of the murid rodent fauna, i.e. smaller faunas were subsets of larger ones, which is typical of relict fauna. The structure of murid rodent assemblages was studied using the size and shape of the lower incisor, in order to test for the effect of interspecific competition on community‐wide patterns. We used two different approaches: one tests for regularity in the size structure of the community (Barton and David test), and the other one tests for minimum mean overlap size in the community between species (randomization procedure). There was no congruence between the results of the two tests: we did not find any case of regular size structure, whereas mean size overlaps were minimum or even zero in about half of the cases studied. Thus, the evolution of rodent communities on islands seems to be characterized by minimization of size overlaps, perhaps as a result of interspecific competition. Also, the reduction of island area, which is correlated with a decrease in species richness, is accompanied by an increase in Hutchinsonian size ratios and a decrease in the total size range of the community. These patterns may be linked to the reduced diversity of environmental resources on islands.
Hierarchical habitat selection by woodland caribou: its relationship to limiting factors
Authors: Rettie W. James , Messier François
Published: August 2010

Habitat selection is a hierarchical process that may yield various patterns depending on the scales of investigation. We employed satellite radio‐telemetry to examine patterns of habitat selection by female woodland caribou in central Saskatchewan at both coarse (seasonal range) and fine (daily area) scales. At each scale, we converted spatial data describing compositions of available and used habitat to standardised resource selection indices and examined them with multivariate analyses of variance. Seasonal ranges generally showed preferential inclusion of peatlands and black spruce dominated stands relative to recently disturbed stands and early seral stage forests. In all populations, caribou preferred peatlands and black spruce forests to all other habitat types at the daily area scale, in general, these patterns may reveal the effective avoidance of wolves, the primary factor limiting caribou throughout the boreal forest. In three populations where seasonal ranges showed the selective inclusion of either young jack pine stands or clearcuts along with peatlands and black spruce forests, we found a relative avoidance of the clearcuts and young jack pine stands at the daily area scale. As all caribou populations in the area are thought to be relics of a once more continuous distribution, the seasonal range selection by animals in disturbed areas may better describe historic rather than current habitat selection. We found inter‐annual variation in selection at the coarser spatial scale in one population, and inter‐seasonal variation in selection at the finer spatial scale in three populations, indicating that the relative grains of the spatial and temporal scales coincide. We were better able to explain the seasonal variations in finer scale selection by considering available forage, a factor less likely than predation to limit woodland caribou populations. The data agree with the theory that the spatial and temporal hierarchy of habitat selection reflects the hierarchy of factors potentially limiting individual fitness.
Patch dynamics in arid lands: localized effects of Acacia papyrocarpa on soils and vegetation of open woodlands of south Australia
Authors: Facelli José M. , Brock Daniel J.
Published: August 2010

Although the importance of plant‐created heterogeneity in arid lands has long been recognized, little information is available on the dynamics of these patches. We studied the changes in soil and vegetation associated with the presence of a long‐lived tree. Acacia papyrocarpa, in arid lands of south Australia. The soil under young individuals was not different from the soil in the surrounding open spaces, confirming the assumption that establishment does not occur preferentially in high fertility patches. The amount of organic matter, total N, total S. total and available P, and soil salinity increased with the age of the tree until maturity, and declined as the canopy of the tree became more fragmented. The content of organic mater and total and available P remained higher than that in the matrix soil for at least fifty years after the death of the tree. There were several species almost completely restricted to the canopy environment. Some, but not all of them, have bird dispersed seeds. One of these species (Enchylaena tomentosa) established and grew better in soil collected under tree canopies in a glasshouse experiment, independently of light environment. After the death of the trees the under‐canopy species declined rapidly, and the patches were colonized by invasive annual species, and short lived perennials. Our results suggest that patch dynamics driven by the population dynamics of woody perennial species have paramount importance for the ecosystem, and community dynamics of arid lands.
Occupancy‐abundance relationships and sampling scales
Authors: He Fangliang , Gaston Kevin J.
Published: August 2010

The area of occupancy of a species and its abundance are dependent on the spatial scale at which they are measured. However, it is less obvious how the scale of sampling affects their correlation. This study investigated and modeled the effects of sampling unit size and a real extent on the interspecific occupancy‐abundance relationships for a tropical tree species assemblage at a local scale and a temperate bird species assemblage at a regional scale. The results showed that both sampling unit size and study extent had profound quantitative effects on the occupancy‐abundance relationship, although it remained positive. Several properties of the occupancy‐abundance relationship can result from the effects of scale: 1) the linearity of the relationship decreases with the increase of sampling unit size; 2) for a given abundance, the area of occupancy increases with sampling unit size; and 3) variation in the area of occupancy increases with the increase of both sampling unit size and extent, and if the extent is large enough may be sufficient that no occupancy‐abundance relationship is observed. Although the occupancy‐abundance relationship can be satisfactorily modeled, the parameters depend on the scale used. This suggests that a model derived from one scale cannot be applied to another. In other words, to estimate the rarity or commonness of species using such a model, the estimation must be strictly done using the same sampling scale for all the species.
Patterns of species richness in dry grassland patches in an agricultural landscape
Authors: Bruun Hans Henrik
Published: August 2010

Eighty‐five patches of semi‐natural grassland of varying size scattered in a agricultural landscape were investigated for their flora of vascular plants. Relationships between species richness and patch area, spatial isolation and local habitat conditions including heterogeneity were examined. Differences between single species and among groups of species defined by life‐history traits were also investigated.

Area was shown to be an important determinant of species richness irrespective of habitat heterogeneity. Isolation in space and habitat heterogeneity also play significant roles. These results are consistent with results from a multitude of studies on fragments of ancient deciduous woodland in northern Europe, They are, however, contradictory to results from previous studies in grasslands within the same region. Seed mass and dispersal syndrome were poor predictors of the degree to which the species were affected by isolation of grassland patches. Seed mass deviation from community median could explain a small percentage of the variation in regional abundance. Logistic regression on species occurrences showed that few species are associated with large patches, and less than half seem to avoid isolated patches.
Is there a higher risk for herbivore outhreaks after cold mast years? An analysis of two plant/herbivore series from southern Norway
Authors: Selås Vidar
Published: August 2010

Historical data on two plant‐herbivore interactions from southern Norway were used to test the hypothesis that the degree of herbivore outbreaks in post‐mast years is negatively related to summer temperatures in the mast year, because plants are more depressed after a high seed production if temperatures and thus the photosynthetic activity is low. The plant species were the sessile oak Quercus petraea and the bilberry Vaceinium myrtillus. For the former species post‐mast years were identified from reports given by the local forest authorities for the period 1930–48, and from acorn export curves for the period 1949–98, For the latter species, post‐mast years were identified mainly from bilberry export curves for the period 1920–31, from game reports for the period 1932–78. and from diary notes for the period 1979–87. The herbivore species used were the green oak leaf roller moth Tortrix viridana and the capercaillie Tetrao urogallus. Eight moth outbreaks on oak forests were reported by the forest authorities in the period 1930–98, and they all started in a post‐mast year of the sessile oak. There were however also eleven post‐mast years without moth outbreaks. According to game reports, observations and autumn counts, all increases in the autumn population size of capercaillie during 1920 88 occurred in or after a year with high bilberry production. Among i8 post‐mast years, there were seven with strong increase, seven with slight or moderate increase, and four with no increase. For both herbivore species, post‐mast years with marked population increases had significantly lower summer temperatures in the preceding (mast) year than had post‐mast years with no or slight increases. For moth populations there also was a negative effect of high temperatures in April, possibly because moth eggs tend to hatch too early relative lo budburst if spring temperatures are high. For the capercaillie, high amount of precipitation in June – July seemed to have some negative impact on the autumn population sizes, as also found in previous studies.
Genetic diversity in the Siberian jay Perisoreus infaustus in fragmented old‐growth forests of Fennoscandia
Authors: Uimaniemi Leena , Orell Markku , Mönkkönen Mikko , Huhta Esa , Jokimäki Jukka , Lumme Jaakko
Published: August 2010

The Siberian jay Perisoreus infaustus is a bird inhabiting old‐growth coniferous taiga forests. It has recently declined in numbers in Finland mainly because of habitat fragmentation. Distant mtDNA lineages from Taimyrian Peninsula (subspecies P. i. monjerensis) and middle Yenisei valley (P. i. rogosovi) have diverged from Fennoseandian (P. i. infaustus) lineage ca 610000 yr ago. The estimated time to the most recent common ancestor for Fennoscandian population (78000 yr) coincides with the beginning of the Weichselian ice age. Within Fennoscandia, the observed distribution of pairwise genetic distances followed the expected distribution of an expanding population reflecting the postglacial history rather than the present day situation of the Siberian jay. Mitochondrial control region sequences showed that among 65 Fennoseandian individuals the most common baplotype (40%) was found in all but two populations. Genetic structuring (φST= 0.111) was clear within the Fennoseandian population. This may be attributable to low intrinsic natal dispersal. In an isolate of western Finland, nucleotide diversity was significantly lower than in P. i. infaustus populations of the continuous distribution area. We suggest that isolation by habitat fragmentation in modern landscapes may effectively reduce gene flow below the level occurring in natural conditions. Thus, Siberian jay isolates with limited number of individuals would be highly vulnerable to loss of genetic variation or even to extinction by demographic or environmental stochasticity.
Geographic range structure in North American landbrids: variation with migratory strategy, trophic level, and breeding habitat
Authors: Linder Eric T. , Villard Marc‐André , Maurer Brian A. , Schmidt Elise Vernon
Published: August 2010

We investigated the relationship between abundance and geographic range structure of 258 North American landbirds. For this purpose we used six measures of range structure based upon fractal geometry and geostatistics, and three ecological characteristics that can influence avian distribution. Permanent residents (PRs) that were abundant showed little fragmentation of their abundance surface at the periphery of their breeding range. Conversely, common Neotropical migrants (NTMs) exhibited low fragmentation of their central populations the abundance surface was smoother for PRs than NTMs or short‐distance migrants (SDMs). indicating that changes in abundance occurred more gradually across space for this group. The areas of high abundance for grassland species had little demographic fragmentation, but other populations showed little spatial autocorrelation in abundance. Species that bred in late‐successional forests were relatively rare compared to species breeding in other habitat types. Among carnivores. PRs had a higher average abundance than either NTMs or SDMs. Although carnivores had more distributional gaps within their ranges than other trophic groups, the number of gaps did not differ between rare and abundant species, indicating that increased abundance did not change their presence. absence distribution maps. Knowledge of patterns and variations of geographic range structure among species may provide insights into processes that shape and maintain the biodiversity of a continent.
Selectivity in the exploitation of floral resources by hoverflies (Diptera: Syrphinae)
Authors: Branquart Etienne , Hemptinne Jean‐Louis
Published: August 2010

Adults of the Syrphinae subfamily display no strong flower preferences but exploit pollen and nectar produced by native plants having large inflorescences and flat corollae (e.g. Apiaceae, Asteraceae. Ranunculaceae and Rosaceae). Seven foraging guilds are defined according to the dietary patterns of hoverflies, reflecting mainly a sequential exploitation of flowers at different times of the year and in different habitats.

The majority of species live in forests where they form highly diversified communities. Few Syrphinae colonize successfully open and anthropogenic habitats, such as field margins and fallow areas.Episyrphus balteatus, Melanostoma mellinum, Eupeodes corollae, Sphaerophoria scriptaandPlatycheirusspp. are dominant in the communities of Syrphinae from open habitats, all over western Europe. These species are highly polyphagous and characterized by elongated mouthparts as well as a long and slender body. They have access to pollen and nectar in flowers with small and tubular corollae. It is suggested that their polyphagy is an important asset for colonizing open and ephemeral habitats.
Differential colonization causing non‐random forest plant community structure in a fragmented agricultural landscape
Authors: Butaye Jan , Jacquemyn Hans , Hermy Martin
Published: August 2010

We investigated forest plant community structure of recent forest patches in a highly fragmented agricultural landscape, A nestedness analysis has been performed at The community level and at the individual species level. We tested the hypothesis that plant species composition showed a nested structure and whether this was generated by isolation and differential colonization. Alternative hypotheses formulated in the past, such as nested habitats and patch area dependent species relaxation, are verified. Isolation measures were calculated between clearly defined source and target patches. At the community level target patches are defined as forest patches < 35 yr old while older patches are considered as source patches. At the individual species level we distinguished between actually occupied and potentially suitable target patches based on a habitat space model and only occupied source patches are taken into account.

All results point out that the nested community pattern in recent forest patches is generated primarily by isolation and differential colonization. These findings are confirmed at the species level, since the degree of nestedness of the individual species is highly correlated with their isolation sensitivity.

Logistic regression analyses prove that many forest plant species are sensitive to isolation. The probability of occurrence of the isolation sensitive species drops almost to zero, when the nearest source patch is situated further than 200 m. Probabilities of colonization increase significantly when source patches are situated adjacent to target patches.