bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribution, ecology, mode of reproduction and karyology of freshwater planarians (Platyhelminthes; Turbellaria; Tricladida) in the springs of the central Pyrenees
Authors: Roca Josep R. , Ribas Maria , Baguñà Jaume
Published: July 2006

The distribution, reproductive modality and karyology of populations of freshwater planarians were studied together with physico‐chemical variables m 149 springs in the central Pyrenees Diversity was limited to four species (Dugesia (Dugesia) subtentaculata, Polycelis felina. Crenobia alpina and Phagocata vitta), already known from streams and lakes Planarians were found rarely (only a third of springs contain them), m low‐moderate abundance, and any single spring did not harbour more than one species

The distribution of potential predators and preys among the springs sampled was fairly uniform So. we assume that whereas predation is unlikely to influence triclad distribution, the oligotrophic character of these habitats may explain, through food shortage and ensuing interspecific competition, the presence of a single species in each spring Besides interspecific competition, the distribution of each species can also be influenced by particular abiotic parameters Temperature and current velocity appeared to be the dominant factors, the first separating C alpina from the rest of species, and the second favouring the presence of P felina in a large set of springs These factors also seem to determine planarian distribution in streams and rivers Other environmental factors such as calcium bicarbonated water (for D subtentaculata) and preference for karst systems (for Phagocata vitta) are of importance Some peculiarities of distribution, like the scarcity of C alpina in reophile habitats and the thermal tolerance of Phagocata vitta, may be due both to competition from P felina and to historical factors in the former and to morphological (presence of pigment) and ecological (epigean habits) features m the latter, respectively

Karyological analyses demonstrated triploidy in all populations of D subtentaculata. a polyploid origin for C alpina and the finding in Phagocata vitta of a new polyploid series leading to the highest chromosome number in turbellarians (14n = 238) Furthermore, the basic chromosome number of C alpina (n = 21) and Phagocata vitta (n = 17) differs from those found in northern European populations (n = 7 in both, respectively) This suggests that under the specific names C alpina and Phagocata vitta more than one species actually occurs, this being a problem for further studies

Whereas polyploidy has often been related to living in cold, harsh habitats, asexual reproduction has been linked to environments where biotic stress is low The preeminence of asexual reproduction (by fissiparity) and polyploid forms in freshwater planarians inhabiting the unproductive, biotically unsaturated springs of the central Pyrenees adds new evidence to strengthen such links
Demography of persistent juveniles in Fraxinus excelsior
Authors: Tapper Per‐Goran
Published: July 2006

Seedling emergence, survival, growth, and juvenile development of Fraxinus excelsior were followed over 10 yr in permanent plots m a dense Alnus‐Fraxinus woodland in the outer archipelago of Stockholm, Sweden Number of germinated seedlings varied between years, due to variation in total seed crop but was also affected by weather conditions Seedlings and juveniles showed high survivorship 39 2% of the emerged seedlings of the two oldest cohorts were alive in the 9th growth season Mortality was somewhat raised during the first two years, but was age‐independent from the third year The density of the field‐layer and climatic factors were the most important determinants of mortality The juveniles produced 1 2 pairs of leaves per year and had an annual height increment of 7 1 mm, on average, from their second growth season The ontogenetic development, e g the increase m leaf complexity, was correspondingly slow and included regressions to more simple leaves

Fraxinus excelsior shows a regenerative strategy involving persistent juveniles The divergence between this and previous studies may be due to the lack of rabbit grazing
Limitation of similarity and feeding habits in three syntopic species of newts (Triturus, Amphibia)
Authors: Joly Pierre , Giacoma Cristina
Published: July 2006

Differences in body size between both species and sex were observed to be close to Hutchinsonian ratios in an assemblage of three species of newts (Triturus italicus, T alpestris and T carnifex) in southern Italy According to feeding, differences in body size were not related with a strict food niche segregation The diet of larger newt included indeed all the prey eaten by smaller newts but showed new prey types Differences between species were more marked than between sexes of the same species, despite a strong sexual dimorphism in body size Larger newts foraged in a wider range of microhabitats and exhibited a greater diversity of foraging tactics Triturus italicus fed essentially on plankton and chironomids in shallow water at the banks of the pond Triturus alpestris foraged also in deeper water, particularly on lsopods in vegetation Prey fallen on the water surface constituted the main part of T carnifex diet According to recent data on newt evolution, speciation consisted in the reduction of body size Our data show that this process has been related with a specialization of the diet and of habitat use
Muskrat life history: a comparison of a northern and southern population
Authors: Simpson Mark R. , Boutin Stan
Published: July 2006

MuskratsOndatra zibethicuswere studied at Old Crow flats Yukon Territory (68°05′N, 140°05W) and Tiny Marsh, Ontario (44°35′N, 79°52′W) during the summers of 1985 and 1986 Life–history traits of these two populations were compared Litter size was not significantly different between the two sites However average annual productivity was significantly greater at Tiny Marsh where individuals produced more litters per season Growth rates of juvenile and adult muskrats were significantly greater at Tiny Marsh, as was juvenile and adult weight However overwinter survival of juvenile muskrats was significantly greater at Old Crow than at Tiny Marsh We suggest that the shorter growing season and proximate energetic limitations on growth and reproduction favour a conservative reproductive strategy by the northern muskrat population For the southern muskrat population a long growing season and high quality food resources allow for a more productive reproductive strategy
Winter filtering, immigrant selection and species composition of insular mammals of Lake Huron
Authors: Lomolino Mark V.
Published: July 2006

Patterns in species composition of small mammals on islands of northwestern Lake Huron, USA were studied to test the hypothesis that insular community structure was strongly influenced by immigrant selection, l e, selection for the more vagile species Of 17 insectivores and rodents in the mainland pool nine were detected on at least one of the 25 islands studied These species comprised a biased subset of the mainland pool, biased in favor of species with relatively good winter immigration abilities The five true hibernators were absent from all islands studied and the two winter‐inactive species occurred on just two islands Frequency of insular occurrence increased with level of winter activity (hibernator vs winter‐inactive vs winter‐active) and with body size (p < 0.02)

The winter filtering effect remains one of the best documented forms of immigrant selection In general however, insular community structure is influenced by the combined effects of selective extinction as well as selective immigration Common insular species are those which combine relatively high immigration abilities with low resource requirements
The importance of alder to hazel grouse in Fennoscandian boreal forest: evidence from four levels of scale
Authors: Swenson Jon E.
Published: July 2006

Buds and staminate catkins of alder (Alnus spp) form an important winter food for hazel grouse Bonasa bonasia in the Fennoscandian boreal forest Alder was found to be highly preferred over other deciduous trees, particularly alders ≥ 10 m tall and ≤15 m from spruce forest Winter territories were probably feeding territories, as size was correlated negatively with alder density and almost significantly correlated negatively with competitor density All winter territories were found to contain ample winter food resources for hazel grouse However, the distribution of territories was associated significantly with the distribution of alders at two levels of scale, the territory level and the landscape level Moreover, relationships between the abundance of alders and hazel grouse were found at two additional levels of scale the local patch level and the biogeographic region level This agreement of the results from four levels of scale strongly suggested that the abundance and distribution of alder was a major factor limiting hazel grouse winter territories within dense Norway spruce Picea abies forests in the boreal zone of Fennoscandia Alder was relatively uncommon and exhibited a clumped dispersion pattern at the local and landscape scales, being associated with wet and rich soils The close relationship to alder implies that hazel grouse winter habitats, even in natural forests, also should be distributed patchily Hazel grouse may select the catkins and buds of alder because it is a very nutntous food source, and small species, such as the hazel grouse, require more nutritious food than larger species
Predation on rodents in Białowieza primeval forest, Poland
Authors: Jędrzejewski Wlodzimierz , Jędrzejewska Bogumila
Published: July 2006

Autumn and winter predation on bank vole Clethrtonomys glareolus and yellow‐necked mouse Apodemus flavicollis was studied in 1985/86‐88/89 in an 11 2 km2 area of the Bialowieza National Park Rodents regularly increased in numbers from spring to autumn and decreased throughout winter Out of 23 species of predators, the most common were tawny owl Strix aluco (43‐57 adult ind 10 km−2) weasel Mustela ntvahs (17‐27 ind), buzzard Buteo buteo (12‐16) and pine marten Martes martes (5‐8) Voles and mice were the staple food for two specialists the stoat Mustela erminea and the weasel, and two generahsts the tawny owl and the pine marten The generalists exploited different alternative prey when rodents were scarce tawny owl ‐amphibians, marten ‐ small mammals, and the red fox Vulpes vulpes ‐ ungulate carcasses and hares The depth of snow and abundance of voles were two major factors shaping the contribution of voles to tawny owl and marten diets No such relationships were found for mice and generalist predators The predation by 8 species (tawny owl, buzzard, marten, weasel, stoat, polecat Mustela putortus fox, and raccoon dog Nyctereutes procyonoides) from 1 October to 15 April in 1986/87, 87/88, and 88/89 was estimated to be on average 28‐35 voles and 14‐17 mice ha Estimates suggested that three species were responsible for 86‐95% of the total predation impact tawny owl (56‐71%), weasel (11‐21%) and marten (10‐15%) The predation impact was similar to the annual decrease in rodent numbers from autumn till spring voles 35 (SD 111) lnds ha‐1in autumn and 8 (SD 2 6) lnds ha‐1in spring, and mice 24 (SD 16 3) mds ha−1 in autumn and 3 (SD 2 5) in spring Predation, therefore, was regarded as the main agent of rodent mortality throughout autumn and winter
Resource partitioning by three species of newts during their aquatic phase
Authors: Fasola Mauro
Published: July 2006

This paper describes the multidimensional niche of syntopic smooth newts Triturus vulgaris. alpine newts Triturus alpestris. and Italian crested newts Triturus carnifex. which constitute a complex community of eight components (the three species and their larvae, plus juvenile and neotenic alpine newts) All the potentially limiting resources (seasonal time, diel time, habitat and food) are analyzed as single niche dimensions, and then the real multidimensional niche is calculated Resource states are objectively defined, using an algorithm that groups the significant resource categories The larvae were segregated by prey, season, habitat, and water depth, in order of decreasing importance, their overlap was very low when their complete multidimensional niche was considered, and therefore they have few opportunities for present–day competition The adults were largely segregated by season and water depth, and to a lesser degree by habitat and prey, their multidimensional niches overlapped to a certain degree, thus leaving conditions for ongoing competition Considenng all the species and the life stages together, the order of importance for segregation was season, prey, habitat, water depth and diel activity, with a low overlap in the complete niche Differences m prey size were probably due to morphological constraints, differences in diel activity had very little effect on segregation except m separating larvae from the adults, and were likely promoted by need to avoid mutual predation and cannibalism It remains to be tested whether seasonal, habitat, and water depth differences are due to competitive pressures or to ecophysiological constraints
Habitat selection of breeding and migrating icterine warblers Hippolais icterina: a multivariate study
Authors: Moskát Csaba , Báldi András , Waliczky Zoltán
Published: July 2006

Site occupancy of migrating and breeding lcterine warblers was studied with respect to unoccupied randomly chosen sites in a willow and poplar mixed forest along the river Danube in Hungary Multivariate discriminant analysis revealed 4 different zones in the ordination diagram exclusive breeding zone, exclusive migrating zone overlapping zone, and an unused zone They were separated according to foliage cover and tree height Tree species composition mostly affects habitat use through physiognomy There was a partially overlapping, but clear difference in habitat selection between the migrating and the breeding birds
Holocene climate changes and warm man‐made refugia may explain why a sixth of British butterflies possess unnatural early‐successional habitats
Authors: Thomas J. A
Published: July 2006

Analyses of their habitats indicate that 18% of British butterfly species are restricted to the earliest seral stages of ecosystems, whereas the same species occupy later seral stages in central Europe, where spring and summer temperatures are warmer. The microclimates of their British habitats are exceptionally warm, compensating for the cooler climate. Most of these British habitats are also ephemeral, and have long depended on man for their creation and regeneration This poses the question of where these species lived before man created their habitats, roughly 6000 BP, I suggest that they are relics from a period when British summers were warmer than today, and that they avoided extinction when the climate cooled by moving into warm refugia created by prehistoric man within three types of ecosystem If summer temperatures become warmer, these species should return to later seral stages that are commoner and less dependent on man.
Dispersal strategies of Danish seashore plants
Authors: Andersen Ulla Vogt
Published: July 2006

The present research is based on previous surveys of primary succession in Danish seashore communities Dispersal spectra for these communities set up, using diaspore morphology as evidence for mode of dispersal Dispersal spectra of species occurring in different zones and different successional phases are compared, and differences between the dispersal spectra of natural and man‐made communities are investigated

The dispersal of diaspores to Danish seashore communities occurs at random because it is mostly achieved by abiotic agents or human beings Wind is the prevalent dispersal vector, even though wind dispersal is not as common in Danish seashore communities as It IS in open, disturbed, treeless vegetation throughout the world Dispersal by water is most common among seashore plants that occur in the outer zones As the succession progresses, it is found that plants with no special device or censer dispersal are more frequent in the intermediary stages, while dispersal by ants, adhesion, and in the digestive tract of animals increases later in the succession No significant difference between dispersal spectra of the natural and man‐made communities was found
The muskoxen Ovibos moschatus in north and northeast Greenland: population trends and the influence of abiotic parameters on population dynamics
Authors: Forchhammer Mads , Boertmann David
Published: July 2006

This paper presents the first long term (1960–89) data set on both muskox Ovibos moschatus density and weather parameters in north and northeast Greenland The muskoxen appear to have expenenced a 25 yr favourable period from the early 1960 ‘ies to the mid 1980’ ies, in which density increased and reached a maximum level The population minimum around 1960 probably represents a long term minimum, following a long, generally unfavourable period between 1940–60 Variation in the local population trends from the southern parts of the muskox distribution m northeast Greenland to the northeast parts, can be divided into three geographical areas (72°–75°N, 75°–77°30 ‘N, and north of 79°30’ N), where density dependent and density independent factors affecting muskox populations are apparently different Regional population stability does not increase towards the north Two density independent (abiotic) factors seem to be of prime importance in determining the muskox population density and distribution in northeast Greenland 1) the amount of winter precipitation affects the distribution of muskoxen negatively, inducing local migrations, but does not have a direct negative effect on large scale variation in density,11) ablation (i.e melting of the upper snow layer) and concomitant ice crust formation in winter have a highly negative effect on muskox density in the southern range, but not in the northern range The two abiotic factors, which show a considerable variation from north to south, are statistically independent and seem to be triggered by different weather conditions The predictions that follow from a climatic model both with respect to the direct influence of abiotic factors on muskox density and the indirect influence of climatic fluctuation, are not fully supported by the data presented here
Patterns and strategies of winter habitat selection in alpine capercaillie
Authors: Storch Ilse
Published: July 2006

Based on radio telemetry, habitat distribution of 32 individual capercaillie Tetrao urogallus was compared with habitat availability at various levels of scale At forest stand level, capercaillie preferred large patches of late succession stages, and selected for moderate canopy closure and high abundance of feeding trees Hens and cocks selected home ranges with high proportions of old forest, and range size was related to old forest fragmentation Winter survival was high independently of habitat selection In cocks, habitat use was affected by social spacing, home range size and use of old forest were age‐dependent, and habitat composition of winter ranges indirectly related to survival and mating success in spring Topography influenced habitat selection, as the birds preferred gentle slopes At the landscape scale, the distribution of bilberry Vaccinium myrtillus was the key to capercaillie habitat use, indicating that habitat requirements in autumn and spring influenced selection of winter ranges The study confirms that capercaillie in central Europe select habitats according to structural features typical of the boreal forests of the species' main distribution range However, spatio‐temporal variation in resource abundance at the landscape scale sets significant limits to suitability of alpine capercaillie habitats
Synchronous and nonsynchronous population fluctuations of some predators and their prey in central Sweden
Authors: Small Robert J. , Marcström Yidar , Willebrand Tomas
Published: July 2006

To test the alternative prey hypothesis (APH), we examined 29‐yr time series of bank voles (indexed by snap‐trapping) and 6 game species (indexed by bag records) from Gavleborg county, central Sweden, for the occurrence of synchronous population fluctuations Only voles and the 3 grouse species exhibited cyclic fluctuations, grouse fluctuations were highly synchronous, and positively correlated with vole fluctuations Although hares were positively correlated with grouse, they were negatively correlated with voles Fox were positively correlated with voles and grouse, however, a strong negative relationship was observed between fox and hares During a sharp decline in fox numbers during the early 1980's due to sarcoptic mange, both grouse and hares exhibited a strong positive numerical response, but, not in synchrony In addition, grouse exhibited large fluctuations during the fox decrease whereas hares did not Due to the contradictory predator‐prey interactions observed, these results provide only partial support for APH
Benthic macroinvertebrate assemblages in north Swedish streams: environmental relationships
Authors: Malmqvist Björn , Maki Mari
Published: July 2006

An analysis of the relationships between lotic macroinvertebrates and environmental variables was earned out on material from 60 riffle sites in streams in northern Sweden The approach involved the use of TWINSPAN classification and canonical correspondence analysis on presence/absence data from two seasons (spring and autumn) Variables most strongly associated with distribution patterns of assemblages were drainage area, elevation, water quality in terms of alkalinity, colour and phosphate and the presence of macrophytes The significance of affinities of different species to these variables are discussed The eight clusters resulting from the TWINSPAN analysis could biologically be interpreted as classes of taxa related to stream size, chemical conditions and algae A multiple regression analysis for predicting species nchness using three independent variables, viz drainage area amount or organic matter, and discharge was constructed The results of the study could be used as a starting point for further work on the community organization of benthie stream assemblages
Large prey for small cubs ‐ on crucial resources of a boreal red fox population
Authors: Lindstróm Erik R.
Published: July 2006

Many studies of red foxVulpes vulpesdiet have indicated a higher frequency of large prey in the diet of cubs at dens in relation to that of adults From time to time this finding has been questioned as an artifact due to the different types of sampling In this paper I suggest that the observations were correct and reflected optimal behaviour of a central place forager I compared the diet of foxes by analyses of 112 cub scats collected at breeding dens and 168 adult scats collected during the same periods The study was performed in a boreal environment, characterised by cyclically fluctuating vole populations According to theory the diets should converge when voles become plentiful During a year of low, but increasing, vole densities, a significantly higher proportion of large prey was found in the sample from cubs than from adults This was not the case during the peak and the decline year, when the presumably easily available voles appeared frequently in the scats of both cubs and adults I argue that the availability of large prey during the first year of increasing vole densities might determine territory sue and hence also average population density of foxes throughout the whole cycle in boreal foxes
A comparison of biological characteristics and distribution between Swedish threatened and non‐threatened forest vascular plants
Authors: Gustafsson Lena
Published: July 2006

Threatened (n = 59) and non‐threatened (n = 308) Swedish forest vascular plant taxa were compared with regard to a number of variables, including distribution, site factors taxonomy, morphology and flowering time A majority of the threatened taxa occur in the southern deciduous woodlands, which only constitute c 0.5% of the total forested area in Sweden There are considerably more threatened taxa in southern than in northern Sweden, a consequence of the successively higher number of forest vascular plants from the north towards the south Threatened taxa grow in forests with significantly higher soil fertility than non‐threatened taxa Significant differences were also revealed regarding light conditions, soil water conditions and month of flowering Threatened taxa grow on soils with significantly higher pH and also with slightly more available nitrogen than non‐threatened taxa, as measured with Ellenberg indicator values Forest stands on fertile soils are uncommon in Sweden and they are also very species‐rich Soil‐type rarity in combination with high species diversity in these soil types thus partly explain why taxa are included in the Swedish Red data list
The effect of summer feeding on juvenile arctic fox survival ‐ a field experiment
Authors: Tannerfeldt Magnus , Angerbjórn Anders , ArvidSon Bengt
Published: July 2006

The arctic fox Alopex lagopus L population in Sweden is small and its numbers fluctuate widely with food availability, l e rodent populations This fluctuation is mediated through differences in recruitment rates between years The recruitment can be divided into three phases number of litters born, number of cubs per litter and cub survival rates The number of litters and their sizes have been shown to depend on food availability during winter and spring To examine cub survival during the summer and how it relates to food availability, we conducted a feeding experiment m northern Sweden during 1990, a year of low rodent density, involving six occupied arctic fox dens Feeding at dens lowered cub mortality rates However, condition and growth rates of juveniles were not influenced by supplementary feeding at dens, nor were they related to the probability of survival for an individual Thus arctic foxes seem to minimize risks rather than maximize growth The juvenile mortality from weaning and over the next 6 wk was 21%, mostly due to starvation Only 82% survived from weaning to the first breeding season Of the one‐year‐old foxes, 50% survived their second year Supplementary feeding of juveniles had no effect on the final survival rates over these two years However, the immediate, positive effect on cub survival could be used in a long‐term, extensive management programme if combined with winter feeding
Growth and survival strategy of the Antarctic mite Alaskozetes antarcticus
Authors: Convey Peter
Published: July 2006

Growth and mortality rates of three juvenile instars and adults of the oribatid miteAlaskozetes antarcticuswere measured over a twelve month period using field enclosures m Its maritime Antarctic habitat A pattern was found of rapid growth during the short summer period (0 2‐0 4 μg dry weight increment per day) followed by gradual weight loss overwinter Most individuals completed one instar per year, reaching a premoult resting phase by late summer, with the moult being delayed and relatively synchronised early the next summer A small proportion of proto‐ and deutonymphs completed two moults within one summer period After the final moult adults overwintered again before commencing oviposition, suggesting that the life cycle (egg‐egg) will take at least five years Mortality was not biased towards any instar or time of year Highest individual growth rates were obtained at a constant temperature of 7°C in the laboratory However expenmentai increase of mean field temperature from 2 7 to 4 3°C by use of a plastic cloche led to decreased growth, although no change in moulting frequency or mortality rate Laboratory survival was greatest at 2°C and decreased with increasing temperature

Alaskozetes antarcticusmay be descnbed as ‘a’ (adversity) selected, showing an exceptionally long life cycle of five to six years and extensive physiological investment in survival adaptations Moult synchronisation in early summer, involving entering winter in the inactive premoult phase, will increase overwinter survival by reducing the chance of inoculative freezing from gut contents, and may be advantageous in maximising the time available for feeding during the subsequent summer, or ensuring proximity of the sexes after the final moult
Opportunistic use of foraging resources by heron communities in southern Europe
Authors: Fasola Mauro
Published: July 2006

Neither theoretical nor descriptive approaches to the study of feeding resources have established whether throughout their range species exploit resources with particular characteristics, and whether resource use is opportunistic, selective or determined by competition among consumers I studied 7 southern European communities of 3‐6 breeding species of herons Foraging habitats and prey types varied widely among regions for each heron species while prey weights varied less Principal Components Analysis characterized each heron species by its use of a specific key resource, composed of combinations of prey size, foraging habitat and prey type, in order of decreasing importance The largest herons (grey and purple) and the smallest (squacco heron) were characterized by specific prey weights and types, while the intermediate sized herons (little egret and night heron) were characterized by prey types and foraging habitats Similarities among heron species in habitat use. prey types and prey weights were significantly higher than random in only a few species‐pairs, and no value was significantly lower than random Aggressions were infrequent both against conspecifics and heterospecifics When compared with explicit predictions of the hypotheses that resource use is shaped by opportunism, independent selectivity, or inter‐species competition, the patterns observed indicate that heron species, although partially selective for prey size, tend opportunistically to use similar habitats and prey types, presumably the most profitable and locally abundant Little evidence was found for competitively constrained resource use Herons in southern Europe may not be limited by feeding resources during breeding, although some evidence (significant overlaps, exclusion from colonies) indicates ongoing competition between grey and purple herons
Vertical seed dispersal by earthworms: a quantitative approach
Authors: Willems J. H. , Huijsmans K. G. A.
Published: July 2006

Earthworms are supposed to play an important role in the dynamics of the soil seed bank, however, experimental evidence and quantitative data are scarce To evaluate the impact of the earthworm species Lumbricus terrains L on the vertical transport of seeds in the soil, laboratory experiments have been earned out Moreover, the worm casts produced and their seed content have been quantified in two chalk grassland sites during one year

The experiment on seed transport has been earned out in cylinders with controlled numbers of worms and seeds at different depths in stenlized soil Seeds used in this experiment proved to be eaten by the earthworms in preceding palatability tests A significant translocation of the seeds in the cylinders with earthworms was recorded after an eight‐week period In spring earthworm activity was mainly found m the upper soil layers in the cylinders, whereas in summer the activity was spread over a larger vertical distance The amount of worm casts collected on permanently marked plots in two different chalk grasslands was very high a minimal quantity of c 750 g nr2 of worm casts were produced yearly The number of germinative seeds brought to the soil surface by worm casts was at least 60‐100 nr2 each year This means that earthworm activity has a substantial impact on the soil seed bank dynamics and hence on the possibility of plant recruitment in this species‐nch ecosystem
Abundance of breeding farmland birds on arable and set‐aside fields at forest edges
Authors: Berg Åke , Pärt Tomas
Published: July 2006

The aim with this study was to investigate whether abundance of farmland birds on fields at forest edges were associated with (I) type of field (young set‐aside vs arable fields), (n) the length and structure of the field‐forest edge zone, and/or (m) with residual habitats such as habitat islands, ditches, roads etc Twenty‐eight farmland bird species (all nesting and/or foraging on open fields) were censused during the breeding season on 48 plots (open fields with adjoining forest edges) in the central parts of Sweden, covering a total area of 595 ha Skylark Alauda arvensis, linnet Carduelis cannabina, whitethroat Sylvia communis and whinchat Saxicola rubetra were found in significantly higher numbers in set‐aside‐plots than cereal ones However, the most important factor explaining variation in the abundance of most species was the structure of the field‐forest ecotone, with the length of shrubby southern deciduous forest edges being the most important factor in 7 of the species Mixed forest edges seemed to be of some importance for the abundance of 3 species, while associations between abundance and length of the other deciduous and coniferous field‐forest ecotones only were significant for one species each Skylarks, white wagtails Motaalla alba and whinchats were positively associated to ditches and yellowhammers Emberiza citrinella and linnets were significantly associated to habitat islands The observed preferences for set‐asides and shrubby field forest edges are suggested to be results of reduced predation risk and increased food abundance
Predation and competition within an assemblage of larval newts (Triturus)
Authors: Griffiths R. A. , de Wijer P. , May R. T.
Published: July 2006

The impact of crested newts (Triturus cristatus) on the smaller‐bodied palmate and smooth newts (T helveticus and T vulgaris) was studied during the larval stages using a combination of field and laboratory experiments In pond enclosures T cristatus larvae had no effect on the two smaller species over the first four weeks of development By eight weeks, however. T cristatus had achieved a size advantage which enabled it to eliminate T helveticus and severely reduce T vulgaris by predation In laboratory trials under food‐limited conditions, T helveticus and T vulgaris were slightly smaller when raised with T cristatus, suggesting that this predatory effect was complemented by interspecific competition during early development Predation of the smaller species started when T cristatus reached a threshold size of c 27 mm No reciprocal effects on T cristatus growth or survival were observed Although T cristatus may be a significant predator of congeneric species in natural ponds, other factors, such as differences in microhabitat selection, higher‐order predator‐prey interactions and the occasional desiccation of pond habitats may facilitate coexistence between the species
Long term changes in the breeding biology of the woodpigeon Columba palumbus in eastern England
Authors: Inglis I. R. , Isaacson A. J. , Thearle R. J. P.
Published: July 2006

Changes in agricultural practice in eastern England have been shown to have had marked effects upon the winter population size of the woodpigeon Columba palumbus This study examines whether changes in the breeding success of the woodpigeon have also occurred Data were gathered between 1962 and 1983 on the breeding activities of woodpigeons within a wood near Newmarket in eastern England The number of nests monitored each year varied between 16 and 122 with a mean of 45 Agricultural changes resulted in a steep decline in the winter population size in the late 1960's and the breeding population snowed a similar fall Before this decline, productivity was on average 2 8 young per pair, but afterwards it was only 1 8 young per pair This drop in productivity resulted from greater egg predation, which increased steadily over the study period Increased egg predation and variation in seasonal patterns of breeding behaviour are discussed in relation to likely predator numbers and changes in both agricultural and shooting practices In the 1960 s. overwinter starvation was the major limiting factor on the woodpigeon population, but after the mid‐1970's low productivity has increasingly become the most important factor
Ecological effects of the parasitic rust fungus Uromyces lineolatus (Pucciniaceae) on Glaux maritima (Primulaceae)
Authors: Jerling Lenn , Berglund Anita
Published: July 2006

Disease incidence of the parasitic rust fungus Uromvces lineolatus (Pucciniaceae) on Glaux maritima (Primulaceae) was recorded in three transects across a Baltic sea shore meadow The effects of the fungus on growth, flowering, seed production and germinability were investigated No significant differences between healthy and diseased plants were found except for abortion rate, germinability and germination rate Incidence of the disease seems to be correlated with accumulation of litter from the winter host Scirpus mantimus (Cyperaceae)
Increased fluctuations of butterfly populations towards the northern edges of species' ranges
Authors: Thomas J. A. , Moss D. , Pollard E.
Published: July 2006

Data from a national butterfly monitoring scheme were analysed to test the theory that animal populations are more variable towards the edges of species ranges Nine of the 24 species tested fluctuated with significantly greater amplitude nearer their northern limits, providing the first clear evidence of this phenomenon among ectotherms With some species, the pattern of fluctuations also varied across ranges with populations increasing and decreasing more gradually, and perhaps cyclically, over several generations in the north
Forest microenvironments and resting energetics of the American marten Martes Americana
Authors: Taylor Sandra L. , Buskirk Steven W.
Published: July 2006

To determine whether American martensMartes americanabehaviourally thermoregulate in winter, and to estimate the energetic cost of resting in various forest microhabltats, we studied microenvironments used by martens in a coniferous forest in the Medicine Bow Mountains, Wyoming We hypothesized that martens would rest in sites that minimized energetic costs, and that the relative thermal efficiency of sites would vary as a function of snow depth and weather By measuring heat loss from a heated model and calculating operative temperature, we found that equivalent marten metabolic rates were inversely related to operative temperatures Operative temperatures were generally higher outside resting cavities than inside, except when snow was > 15 cm. outside air temperature was ≤−5°C. and wind was ≥0.3 m s−1For the models lying on a snowy substrate, total body conductance was 0 32 W °C−123% higher than with the models lying on dry wood chips The microenvironments of resting sites and the preferences of martens generally are consistent with our hypothesis of behavioural thermoregulation Conductance contributed strongly to total thermal losses and to explaining selection of resting sites We propose a decision tree to predict where American martens should rest under a range of environmental conditions
Spatial modelling of the barn owl Tyto alba habitat using landscape characteristics derived from SPOT data
Authors: Andries A. M. , Gulinck H. , Herremans M.
Published: July 2006

Landscape parameters extracted from classified SPOT satellite imagery are used as independent variables for predicting potential habitat areas of the barn owl Tyto alba in a landscape north‐east of Brussels, Belgium Field data on the nest sites, recorded during 9 yr, are used as the dependent variable A canonical correlation analysis of the landscape characteristics of ‘successful breeding and non‐breeding sites’ selects a set of most significant parameters contributing to the distinction between suitable and unsuitable breeding habitat parameters measuring the spatial configuration and fragmentation of landscape elements, such as deciduous woods and grasslands, in combination with some visual characteristics of the open spaces in the landscape The selected set of parameters formed the basis for the calculation of a habitat model, whereby potential breeding sites could be located throughout the complete study area, at specific levels of confidence The results showed the relevance of this method for landscape ecological research and nature conservation planning
Taxonomic differentiation in species richness gradients among European butterflies (Papilionoidea, Hesperioidea): contribution of macroevolutionary dynamics
Authors: Dennis Roger L. H. , Shreeve Tim G. , Williams W. Robert
Published: July 2006

We examine spatial differences in patterns of species nchness among butterfly families in Europe and North Africa When compared to global proportions for the whole region there is a surplus of Nymphalidae in northern Europe, of Piendae in North Africa and the Mediterranean islands, of Lycaenidae in Iberia and Greece, of Hesperudae in the Algarve, and a deficit of Satyridae outside the mountain areas For the Lycaenidae and Satyridae the spatial bias in numbers of species corresponds with a bias for endemism in southem Europe, regions of refuge and persistence during Pleistocene polyglaciation We argue that regional surpluses of species in at least these two families are governed more by net species production than by species maintenance Differences in species richness between families are related to ecological amplitude and dispersal capacity which determine balances between migration, clade isolation, speciation and extinction Taxa capable of migrating long distances (e g many Nymphalidae) are able to colonize distant locations but are less amenable to clade isolation, speciation or extinction, whereas, specialized taxa with limned capacity for migration (e g most Satyridae) cannot colonize distant habitats but more readily undergo clade furcation, speciation or extinction Yet, only taxa initially able to disperse and extend their ranges can undergo clade furcation Dispersal capacity divides into extnnsic and intrinsic parameters Both are influenced by environmental changes, particularly resource geography, associated with Pleistocene glacial cycles Changes in resource geography, by influencing extrinsic components of dispersal and in turn reinforcing lntrinsic components of dispersal, result in a polanzation in evolutionary dynamics, one extreme is extensive migration, gene flow and gene pool homogeneity, the other is isolation, speciation or extinction At the isolation end of this scale, the balance between clade evolution and extinction depends on the nature of environmental change and landscape structure
Forest fragmentation due to agriculture affects the reproductive success of the ground‐nesting black grouse Tetrao tetrix
Authors: Kurki Sami , Lindén Harto
Published: July 2006

We used data from the Finnish wildlife triangle censuses (1989‐92) to test the prediction that the reproductive success of ground‐nesting bird species is lowered in forest landscapes fragmented by the occurrence of agricultural land, presumably as a consequence of increased densities of generalist predators Our study was based on 201 wildlife triangles located in central Finland (total length 2412 km) As expected, the proportion of black grouse hens with a brood in August decreased relative to the increasing proportion of agricultural land in a landscape (100 km2) However, on a smaller spatial scale (10 8 km2), the probability of an observed hen being with a brood was higher in the vicinity of fields This finding may be explained by differences in habitat selection between hens with a brood and those without a brood We did not find any negative effect of landscape composition on brood size We conclude that increased predation pressure in forest landscapes fragmented by agriculture affects nesting success, but not the survival of black grouse chicks after hatching Our results also emphasize the importance of spatial scale in studies of landscape ecology
Carbon and nutrient mineralization and fungal spore composition of fecal pellets from voles in Minnesota
Authors: Pastor John , Dewey Bradley , Christian Donald P.
Published: July 2006

Numerous investigators have suggested that small mammals may regulate ecosystem processes because they couple producers and decomposers through deposition of fecal materials and by dispersing spores from mycprrhizal symbiotic fungi. We investigated carbon, nitrogen, and phosphorus mineralization rates from feces of two arvicoline rodents,Clethrionomys gapperiandMicrotus pennsylvanicus, common in the forests of the Lake Superior region. We also examined fungal spore composition from these feces. Mineralizable pools of C and N and their decay rates were higher in feces fromC. gapperithan fromM. pennsylvanicus, but there were no differences in sizes of mineralizable pools of phosphorus. Feces ofC gappericontained four times more fungal spores than those ofM. pennsylvanicus.Twenty‐three fungal genera were represented in these feces, and all but one genus have predominantly ectomycorrhizal forms. Fungal species composition also differed significantly between the two arvicoline species. Although the amount of N and P mineralized annually from populations of these two species is small compared with nutrient budgets for the forests as a whole, these species may be important in dispersing spores and labile nutrient pools to microsites of seedling establishment.
The ants (Hymenoptera: Formicidae) of Polynesia revisited: species numbers and the importance of sampling intensity
Authors: Morrison Lloyd W.
Published: July 2006

The ant faunas of three remote Polynesian islands were censused using hand collecting techniques. Known ant species richnesses were increased by factors of 2.3, 3.7, and 4.3, and total species richnesses were estimated with a first‐order jacklcnife estimator. The large increase in species numbers is apparently due to inadequate earlier censuses (which missed localized and cryptic species) rather than recent immigrations. Tests of species associations revealed more positive than negative interactions among species, on both a pairwise and community‐wide basis. There is no evidence that ant species on these islands exclude each other from islands or from communities within islands, with the exception of three very aggressive species. A multiple regression analysis of known ant species richness against sampling effort and area for Polynesian islands which have been differentially censused for ants by various collectors revealed sampling effort was highly significant, while area was not significant, in explaining variation in known ant species numbers. On Pacific islands that have been surveyed relatively thoroughly for ants, multiple regression analyses of known ant species richness on area and distance showed that area was always highly significant, but distance was only marginally significant (depending on the regression model used). Thus remote Polynesian islands appear neither to be as depauperate as previously thought in numbers of ant species present, nor possess an unusual potential for evolutionary increase in species numbers.
Solitary plants do as well as clumped ones in Silene uniflora (Caryophyllaceae)
Authors: Pettersson Mats W.
Published: July 2006

Many studies have been done on seed production as a function of population density in wild plants Most of them show a higher seed‐set per flower of densely growing plants In this study, in a gynodioecious Silene uniflora (Caryophyllaceae) population on the Baltic island of Oland, high plant density did not increase fruit‐set or seed‐set Instead, the total number of seeds set was slightly higher for widely scattered plants as a result of a somewhat lower number of ovules per flower in densely growing plants Individuals had nothing to gain by growing close together, because there was no reproductive parameter which could compensate for the low ovule number per flower of closely growing plants Plant size determined the total seed production of individuals, but did not correlate with any of the fitness components studied per flower basis The different gender morphs showed the same pattern, which is discussed as a comparison with pollen limitation in self‐incompatible and self‐incompatible plants