bluuebunny/crossref_metadata_2025 huggingface dataset:
Habitat selection as a hierarchy: the spatial scales of winter foraging by muskoxen
Authors: Schaefer James A. , Messier François
Published: July 2006

We studied the winter resource selection of muskoxenOvibos moschatusin the High Arctic using a nested hierarchy of spatial scales 1) population range, 2) travel routes, 3) feeding sites (l e clusters of feeding craters), 4) feeding craters, and 5) diet (I e plant species) We found that, generally, patterns of selection remained consistent across all levels At successively smaller scales, muskoxen selected for higher graminoid abundance and particularly for thinner, softer snow cover, although we did not reject the hypothesis of random travel route selection Muskoxen uncovered forages from beneath the snow cover, by cratering, near the flonstic and nival extremes of availability Selection was consistently biased toward use of water sedge,Carex aquatilisAs scale changed, however, muskoxen showed reversals of preference for some other forage species Diet was dominated byC aquatilisand cotton sedge,Eriophorum angustifolium, species characteristic of lowland meadows During spring melt, muskoxen moved to snow‐free uplands to feed Dietary quality, as revealed by fecal nitrogen, increased at this time The consistency of the results across scales implied that these local levels of habitat selection occurred within one scaling domain
Climate and outbreaks of the forest tent caterpillar
Authors: Daniel Colin J. , Myers Judith H.
Published: July 2006

Some have suggested that the periodic outbreaks of the forest tent caterpillar. Malacosoma disstria are triggered by weather the temperature at the time of early larval feeding, and overwintering temperatures To assess the role of these factors, defoliation maps, compiled annually from flight surveys for the province of Ontario. were compared to similarly scaled temperature records An analysis of the year to year variation shows no relationship between the pattern of increases or declines in defoliation and either temperatures during early larval development, or overwintering temperatures Four periods of defoliation by forest tent caterpillars were observed in Ontario over 41 yr. but at individual sites extensive defoliation did not occur for each of the outbreak periods Defoliation was less severe in regions with low overwintering temperatures, but was not related to the average number of degree days m the early spring Outbreaks were most common in areas where deciduous forests were extensive, and the mean overwintering temperatures were above −40°C While these weather variables do not apparently explain the details of population dynamics of forest tent caterpillars, extreme weather conditions might synchronize populations
Population trends in black woodpecker in relation to changes and characteristics of European forests
Authors: Mikusiński Grzegorz
Published: July 2006

During the last century the black woodpecker Drycopus maritus has expanded m range in central and western Europe Habitat changes were the most common explanations of these expansions I compared changes m forest characteristics in countries where different black woodpecker population trends were observed Results showed that countries with positive population trends had significantly higher increase in coniferous forest volume These countries had also significantly higher proportion of young forest stands The importance of coniferous forests, as well as importance of forest structure for the black woodpecker, are discussed
Temporal variation in spatial organization of a rodent community in the southwestern Kyzylkum desert (Middle Asia)
Authors: Shenbrot Georgy I. , Rogovin Konstantin A.
Published: July 2006

The distribution of niches in resource space and the niche patterns of a 14‐species community of Middle Asian desert rodents were studied during two years ‐ at low and high rodent density ‐ using discriminant function analysis Nineteen quantitative environmental parameters (soil structure and vegetation), measured in 550 plots within 22 1 ‐ha grids, were considered The first three canonical axes of resource space account for 72% of the variance The first two axes represent complex environmental gradients the first axis represents a general landscape gradient from sand to clay soils, the second axis reflects a gradient of in creasing productivity The third axis reflects with in‐habitat environmental variation All community parameters, as well as parameters of individual species niches, were unstable between years At the same time, different parameters vary in different extent Position of niche centroids along macro‐habitat axes, as. well as macrohabitat niche breadth, were relatively stable between years, but these parameters for microhabitat axis and values of niche overlap were much more variable A strong correlation between changes m relative between‐habitat niche breadth and differences in average niche overlap with relative changes in species abundances indicate density dependence of these parameters Changes in niche overlap is a consequence of between‐year differences in guild patterns Guild structure was pronounced at high density when the level of niche overlap was intermediate At low density, when the level of niche overlap decreased, guild structure was incon‐spicous Different levels of diversity differed in their sensitivity to density changes α‐diversity was relatively constant as a result of between‐year stability of niche centroid positions However level of ß‐diversity varied significantly between years reflecting changes in the level of niche overlap, because a decrease in niche overlap leads to an increase in the rate of species turnover
Native and alien invasive plants: more of the same?
Authors: Thompson Ken , Hodgson John G. , Rich Tim C. G.
Published: July 2006

We compare the ecological and habitat characteristics of alien and native vascular plants which have recently expanded in range m England, Scotland, the Republic of Ireland and the Netherlands In the great majority of respects, expanding aliens and natives are functionally indistinguishable However, there are a few consistent differences aliens are more likely than natives to be clonal, polycarpic perennials with erect, leafy stems, and to have transient seed banks We discuss these trends m the context of the difficulties faced by aliens in invading mostly closed plant communities in relatively cool, damp climates Our results are consistent with some predictions of the attributes of‘ideal’invaders, but contradict others We argue that the ecological attributes of successful alien invaders are strongly habitat‐dependent
Nest predation patterns in ground‐nesting passerines on the Iberian Peninsula
Authors: Yanes Miguel , Suarez Francisco
Published: July 2006

The idea that ground‐nesting birds have a high risk of predation is widely accepted This paper analyzes the nest predation patterns of ground‐nesting passerines on the Iberian Peninsula The nest predation rates are higher m open land species x= 71%) than m countryside farmland (10%) or forest birds (29%) The latter species have no differences in daily survival between ground and above‐ground nests The higher nest predation in ground‐nesting open land species was similar m peninsular Spain and North America We conclude that it is incorrect to generalize that all ground nesters have high nest predation rates, and we discuss the possible link of the high nest predation rates of open land birds to the decline observed in their population trends in Spain
Effects of small‐scale habitat disturbance on the ecology of breeding birds in a Vermont (USA) hardwood forest
Authors: Lent Richard A. , Capen David E.
Published: July 2006

We studied territory placement and foraging behavior of breeding birds in relation to juxtaposition of forest vegetation and logged patches in southern Vermont, USA Different bird species used disturbed vegetation at differing spatial scales, depending on temtory size Four species Dendroica pensylvamca. Geothlypis trichas, Zonotrichia albicollis, Oporornis Philadelphia showed strong clumping of their small (< 0 5 ha) territories in logged patches and were absent or rare in undisturbed forest Eleven species (e g Seiurus aurocapillus, Vireo ohvaceus) tended to avoid logged areas, especially the centers of cut patches An additional 17 species fell between these two extremes, using a mixture of disturbed and undisturbed forest and showing no tendency to prefer one or the other These 17 species tended to have larger (1 to > 3 ha) territories than disturbance specialists We used ordination and quantitative matrix comparisons to describe and test relationships among 14 of the most common bird species according to their similarities in territory habitat structure, tree species composition, and foraging behavior These analyses did not reveal any strong associations between foraging behavior and use of cut versus uncut forest Habitat use by birds occupying this forest mosaic, with its strong local gradient of vegetation structure, was thus not associated with concurrent variation in foraging behavior The sizes of cut patches of forest (0 7‐1 6 ha) in our study area may be close to the minimum required to attract distinct breeding assemblages of non‐forest birds to otherwise undisturbed forest ecosystems Bird species that use patches of early‐successional vegetation embedded m a forested landscape may adopt a fugitive strategy as they seek nesting habitats in the spring Careful use of forest management techniques may permit both forest‐interior and early‐successional bird species to coexist m the landscape
Habitat‐related dispersal in the rock‐dwelling land snail Chondrina clienta
Authors: Baur Bruno , Baur Anette
Published: July 2006

Habitat type may influence dispersal in a variety of animal species We examined dispersal in the rock‐dwelling land snailChondrina clientam a limestone pavement, on vertical rock walls, a pile of stones and a stone wall on the Baltic island of Oland, Sweden Dispersal was estimated by recording movements of markedC clientain natural populations over 3 yr Dispersal differed significantly between habitat types The largest distances dispersed were recorded in the limestone pavement (264 cm yr1, median distance) and on vertical rock walls (96 cm yr1), simple habitats for travelling snails Dispersal was less in the stone pile (68 cm yr1) and on the stone wall (88 cm yr1) that are more complex habitats with multiple layers of pieces of stones Distances dispersed also varied among vertical rock walls, indicating that other factors such as exposure of the rock surface and size of the habitat may be important in determining snail dispersal The results of two experiments indicated that grassland vegetation may inhibit dispersal in Cclienta, and that isolated stones covered with lichens might serve as stepping stones for dispersing snails in otherwise unsuitable grassland Snail size (age) influenced distances moved, but might only be important in determining daily movements, not dispersal over longer periods Dispersal inC clientais habitat‐specific and cannot be characterized by a single parameter
Population dynamics and regulation in the coypu Myocastor coypus in central Italy
Authors: Reggiani Gabriella , Boitani Luigi , De Stefano Rita
Published: July 2006

A capture‐recapture design was applied between January 1989 and June 1991 in a 37 5 ha area located in the central valley of the Tiber River (Latium), aimed at estimating the demographic parameters of a coypu population in the Mediterranean climate and at preliminarily investigating the factors that regulate its numbers in this region The population fluctuated between 27 and 137 individuals and followed a seasonal pattern It decreased after the winter and increased between summer and winter Density remained almost stable during a particularly mild winter Survival rates remained relatively high over the entire study period, reproductive activity and additions to the population from in situ reproduction, however, showed minimum peaks following colder winters Evidence of immigration was detected during periods of increasing density Key factor and preliminary density dependence analyses showed that pregnancy failure and newborn losses are cumulatively the most important factor contributing to varation in total mortality, and are positively related to coypu numbers in previous periods The failure to realize maximum potential fecundity is inversely related to previous coypu abundance We show that post‐recruitment losses play only a minor role in determining population decline
Habitat selection and offspring survival rate in three paracoprid dung beetles: the influence of soil type and soil moisture
Authors: Sowig Peter
Published: July 2006

Paracoprid dung beetles build brood chambers in the soil beneath a dung pat and provide them with dungOnthophagusspecies lay one egg into each chamber This paper deals with the influence of soil type and soil moisture on micro‐habitat selection and survival of offspring m three middle‐EuropeanOnthophagus‐species(O coenobita, O fracticonisandO vacca)Discrimination between sandy soils with three different loam contents (0%, 20%, 40%) and four different water contents (4%, 8%, 12%, 16%) was tested in the laboratory During the first 24 h of each replicate beetles which colonized one of the patches did not distinguish between different soil conditions Emigration rates, measured as time when 50% of all individuals had left the patch, and numbers of brood chambers proved to be species specific and depended on soil moisture and soil type Survival rates of the larvae in the brood chambers were influenced nearly exclusively by soil moisture The results are discussed in relation to the ecology of the three species and in context with optimal foraging theories
Effects of wintering greylag geese Anser anser on their Scirpus food plants
Authors: Amat Juan A.
Published: July 2006

Herbivory of Scirpus litoralis and 5 mantimus tubers by wintering greylag geese, Anser anser, was studied at the marshes of the Guadalquivir in southwestern Spain Exclosures were constructed to compare plant growth m grazed and in grazed sites Scirpus luoralis tubers are clustered, with clusters being interconnected by rhizomes Scirpus mantimus tubers develop individually, and are connected by rhizomes The geese forage on individual S mantimus tubers but take entire clusters of S litoralis tubers, from which only one tuber is normally consumed The reproductive mode of S mantimus, the main food plant of the wintering geese, was dependent on tuber size The proportion of tubers whose shoots bear inflorescences decreases with increasing tuber size, and the larger tubers reproduce vegetatively The geese feed on the smaller S mantimus tubers and the smaller S litoralis clusters Reasons for this preference may be that these tubers and clusters are easier to extract and also that small tubers require less time to break down in the gizzard The number of shoots of S litoralis and S mantimus in grazed sites was 88% and 32%, respectively, compared with that in ungrazed sites Nevertheless this difference reflects m part a decrease of 5 litoralis inside some exclosures during a five years period The length of shoots of both species was shorter in grazed than in ungrazed sites The size‐related selection of tubers by geese may have a profound effect on the structure and dynamics of these plants populations, and the trade‐off between sexual and asexual reproduction However, due to the clonal nature of the plants, interpretation of plant‐goose interactions from an evolunonary perspective is difficult because of the elusive unit of selection involved
Indirect seed dispersal by the feral cats Felis catus in island ecosystems (Canary Islands)
Authors: Nogales Manuel , Medina Félix M. , Valido Alfredo
Published: July 2006

In this paper we present an unusual incidence of an introduced Camivora Felis catus as indirect seed disperser of plants that produce fleshy fruits in different ecosystems in the Canary Islands. Four hundred and twenty six seeds from at least 8 fleshy fruit plant species have been identified in the analysis of 1047 scat groups, the majority of them being found in the lower habitats (<600 m a.s.l.) of the Canary archipelago. Seeds from two plant species were significantly matched with the presence of lizard prey, and fruits of Juniperus phoenicea, Neochamaelea pulverulenta and Withania aristata were directly consumed by the cats. Passing through the gut of the Gallotia galloti (Lacertidae) and Felis catus apparently does not damage the seeds. At the moment, the phenomenon studied in this paper does not seem to have a great quantitative importance in the natural regeneration of the plants if we compare the direct vs indirect seed dispersal.
Distribution and dynamics of surface‐dwelling spiders across a pasture‐plantation ecotone
Authors: Downie Iain S. , Coulson John C. , Butterfield Jennifer E. L.
Published: July 2006

The influence of the interface between different vegetation types on the surface active spider fauna within a grass pasture‐coniferous plantation ecotone was sampled by pitfall trapping. Species abundance, richness and diversity relative to pitfall traps were measured along a transect across the ecotone. Spider species were classified into six categories based on their habitat preference and the influence of the non‐preferred habitat. The number of individuals trapped progressively decreased from the pasture across the interface to the plantation habitat. Species richness increased by some 72% and diversity by some 141% at the interface. These increases were attributable to both the overlap of pasture and plantation species invading the non‐preferred habitat across the interface, and to the presence of species with a preference for the ecotone. The overlap of pasture and plantation species was found to be the larger part of the spider community at the interface, species classed as ecotone accounting for only 25% of the catch at the interface. Distinct spider species assemblages were found in the pasture and plantation habitats, and the interface species composition was more similar to the plantation than to the pasture. The variation in physical and biological characteristics which the interface induces, and their influence on the spider assemblages found, are discussed in relation to other ecotone studies.
Importance of spruce swamp‐forests for epiphyte diversity and flora on Picea abies in southern and middle boreal Finland
Authors: Kuusinen M.
Published: July 2006

The epiphyte (lichens and bryophytes) species richness, diversity and composition on basal trunks of Picea abies in spruce swamp‐forests were compared to adjacent mesic forests on mineral soil in two southern and two middle boreal sites in old‐growth forest patches in Finland. The sampling was carried out along four line transects parallel to swamp‐forest margin: 1) in the spruce swamp‐forest, 2) at the swamp‐forest margin, 3) on mineral soil c. 10–20 m off the swamp‐forest margin and 4) on mineral soil at least 50 m off the swamp‐forest margin. In the two southern boreal sites there was a decreasing trend in the average species number per tree from the trees in swamp‐forests (21–25 species) to the trees on mineral soil (17–18 species), whereas in the two more humid and virgin middle boreal sites a similar trend was not detected (25–28 species on all trees). There were no major differences in the epiphyte flora between the locations or study sites; the dominant species occurred on nearly all sample trees. The crustose lichens Cliostomum leprosum, Arthonia leucopellaea and Lecanactis abietina were the most common species that were mainly confined to the swamp‐forests in the southern boreal sites, C. leprosum also in the middle boreal sites. In addition, several rare species occurred exclusively on the swamp‐forest trees. Lecanactis abietina extended significantly higher on the swamp‐forest trees than on the trees on mineral soil in the southern boreal sites. The spruce swamp‐forests proved to be one of the most important habitats for maintaining the epiphyte diversity in the boreal forest landscape.
Dispersal and habitat connectivity in complex heterogeneous landscapes: an analysis with a GIS‐based random walk model
Authors: Schippers P. , Verboom J. , Knaapen J. P. , van Apeldoorn R. C.
Published: July 2006

A grid‐based random walk model has been developed to simulate animal dispersal, taking landscape heterogeneity and linear barriers such as roads and rivers into account. The model can be used to estimate connectivity, and has been parameterized for the badger in the central Netherlands. The importance of key parameters was evaluated by means of sensitivity analysis. Results agree with field observations, and give interesting insight into the isolation or populations and potential populations. The model can be applied to obtain knowledge about dispersal processes in complex landscapes.
Weather dependent effects of nest ectoparasites on their bird hosts
Authors: Merino Santiago , Potti Jaime
Published: July 2006

This study reports the relationships between rainfall and ambient temperature with the abundances and prevalences of three species of ectoparasitic arthropods (viz, mites, blowfly larvae, fleas) in pied flycatcherFicedula hypoleucanests in three different breeding seasons. In addition to its effects on the growth of nestling pied flycatchers, weather conditions were found to determine patterns of abundance and prevalence of ectoparasites. Nest ectoparasites had detrimental effects on the fitness (nestling growth and survival until fledgling) of their hosts, although the effects and the identity of harmful ectoparasites varied across the years. Among the three species of nest ectoparasites, mites had the most consistent harmful effects on nestling growth. Fleas were detrimental in the more cold and rainy year, while blowflies caused nestling mortality in the warmer year. Different host‐parasite interactions were present each year, most likely due to the effects or weather on the activity and timing of development of parasite populations.
Plant niches along the water–table gradient on an ombrotrophic mire expanse
Authors: Nordbakken Jern‐Frode
Published: July 2006

The vegetation within an ombrotrophic mire expanse in SE Norway is studied in detail. Presence/absence of species and depth to the water table are recorded for 6 976 plots (4 × 4 cm). The cumulative probability distributions along the water‐table gradient are calculated Tor 24 species, and inter‐transect variability tested. Shifts in realised depth to the water table (niche shifts) are frequent for most species. It is concluded that interactions are of minor importance for species in the field layer. The Sphagnum spp. possess some attributes indicating equilibrium, while others indicate ongoing competition. The patchy distribution of hepatics and lichens depend on chance and successional stage, and coexistence within these guilds depend on creation of new naked peat patches.
Spatial structure of community of darkling beetles (Coleoptera: Tenebrionidae) in the Negev Highlands, Israel
Authors: Krasnov B. , Shenbrot G.
Published: July 2006

The distribution of niches in resource space of darkling beetles of Negev desert, Israel were studied using discriminant analysis. Seventeen environmental variables (substrate structure and vegetation) were measured at 375 plots within 15 grids. The first three discriminant axes account for 77% of the variance and reflect a soil structure gradient from sand to clay (the first axis), a gradient of increasing productivity (the second axis), and a type of vegetation architecture (the third axis). Abundance and biomass of tenebrionids increased linearly along the first, the second and the third axes. Species richness and diversity had a slanting parabola shape along the substrate axis and increased along the productivity axis. There were two distinct spatial guilds of tenebrionid species. One guild was composed by species that preferred sandy‐gravel soils, and another guild consisted of species that preferred clay soils. Niche overlapping of the “sandy‐gravel” species was lower than that of the “clay” species. Niches of the “sandy‐gravel” species were randomly distributed in the resource space. Those of the “clay” species formed a tight cluster with most niches placed in the center of the space, representing the centrifugal type of organization. The conformity of the guild structure with the different types of organization was supported by comparisons between empirical data and stochastic models. The border between these two guilds matches with proposed earlier biogeographical boundary (Ramon‐Zohar line).
Boreal mixedwood forests may have no “representative” areas: some implications for reserve design
Authors: Gumming S. G. , Burton P. J. , Klinkenberg B.
Published: July 2006

We tested the shifting mosaic steady state theory in a ≅73 600 km2 landscape within the boreal mixedwood region of Alberta. Canada. The theory predicts that, at some spatial scale, mean vegetation attributes are temporally stable. It follows that contiguous sub‐regions (stable mosaics) exist whose attributes are similar to regional values. The scale at which this stability occurs may be interpreted as the minimal size for an ecological reserve designed to represent the region. We argue that the appropriate attributes to test the theory in this case are the age and size structures of various forest stand populations. Using forest inventory data, we searched for stable mosaics (“representative areas”) at multiple spatial scales, using two different spatial decompositions of the study area. Areas were compared using 2‐dimensional similarity metrics based on goodness‐of‐fit statistics. We found that the age and size structures of the entire study area could not be replicated at any smaller scale, which disconfirms the theory for the boreal mixedwood. Each of five compositionally distinct populations of forest stands have characteristic age and size structures, and patterns of spatial variability, which we relate to aspects of the regional ecology. Stand age and size structures have independent spatial variability. We observed multi‐scaled heterogeneity in forest composition, which appears to arise partly from infrequent fire episodes when many large fires occur. These episodes are probably not uniform in their effect on forest structure.

We evaluate two methods for constructing reserve systems in non‐equilibrium landscapes, using small collections of disconnected subunits. Small areas can readily be built that more closely match landscape properties than any contiguous area of reasonable size. The degree of representativeness and total size of the constructed areas is sensitive to the size of the constituent pieces; in the mixedwood, there is a natural scale of 1,500 km2 which is near‐optimal. Reserves constructed in this way are unlikely to be temporally stable. We therefore propose a dynamic strategy for maintaining reserve systems over time within a managed landscape. Under this “floating reserve” strategy, portions of the system would be periodically replaced in response to the aging of components, unexpected large scale disturbance, or refinements in conservation objectives.
Genetic structure in the species‐pairSilene vulgarisandS. uniflora(Caryophyllaceae) on the Baltic island of Öland
Authors: Runyeon Helena , Prentice Honor C.
Published: July 2006

Allozyme data were used to assess the genetic structure between 37 sympatric populations of the species‐pairSilene vulgarisandS. uniflorassp.petraea, and to infer levels of intra— and interspecific gene flow in the two species.Silene vulgarisis a geographically widespread weed of disturbed habitats whereasS. uniflorassp.petraeais endemic to the Baltic islands of Öland and Gotland. On Öland,Silene vulgarisforms extensive linear populations along roads whileS. uniflorassp.petraeaoccurs in sparse and spatially‐separated populations in open limestone habitats. Despite the differences in population size and structure between the two species, both species show extremely low levels of between‐population differentiation. Between‐site differences account for <2% of the total allozyme diversity within Öland inS. vulgaris, and <1% inS. uniflorassp.petraea.Indirect estimates of gene flow are high for both species (Nm = 11 and 27, respectively). There is no relationship between genetic distance and geographic distance within either species, and the lack of genetic structure is consistent with the pollination biology of the species — both of which are predominantly moth‐pollinated. The two species hybridize in intermediate habitats, and the geographic distribution of species‐characteristic alleles indicates a potential for spatially extensive interspecific gene flow. Nevertheless, there are significant differences in allele frequencies between the two species and multivariate analyses show no overlap between populations of the two species. The species are ecologically separated by their different habitat preferences and by differences in their flowering phenology. There is no evidence that the endemicS. uniflorassp.petraeais threatened by genetic contamination or assimilation by the widespread weed,S. vulgaris.
Relationships of bird community structure and species distributions to two environmental gradients in the northern boreal forest
Authors: Welsh Daniel A. , Lougheed Stephen C.
Published: July 2006

Few studies have explicitly examined avian community structure in the North American northern boreal forest. Herein we report upon the results of bird surveys in mature stands of boreal forest in the Great Clay Belt, Ontario, Canada. We related trends in avian community structure and individual bird species' abundance to two environmental gradients described in a landbase classification scheme called the Forest Ecosystem Classification — a moisture and a nutrient‐richness gradient. Variation in environmental characteristics is limited in the Ontario Clay Belt and this was reflected in short environmental gradient lengths. However, major trends in avian community structure were strongly associated with the nutrient‐richness gradient axis summarized by this scheme. Analyses of avian community composition indicated a continuum from moist, coniferous habitats to drier aspen‐dominated mixed woodlands with several bird species occurring in varying abundances across the width of both gradients. 48 of the 58 species examined showed statistically significant associations with at least one of the two multivariate gradient axes. A smaller proportion of short‐distance migrant species were associated with these gradients than were species in either the neotropical migrant or resident categories. We used a multivariate variable (“habitat breadth”) to compare degree of habitat specialization across different migratory groups. A large proportion of neotropical migrants showed a high degree of habitat specialization in mature Clay Belt forests, and neotropical species with small habitat breadths were more commonly associated with habitats dominated by broad‐leaved deciduous tree species than either short‐distance or permanent resident species. We discuss our findings in relation to the post‐glacial history of the Clay Belt region.
Spruce forest bryophytes in central Norway and their relationship to environmental factors including modern forestry
Authors: Frisvoll Arne A. , Prestø Tommy
Published: July 2006

In this study of bryophyte diversity in 110 patches of spruce forests of bilberry, small fern, low herb, tall fern and tall herb type in Ser‐Trøndelag, central Norway, each patch (from 0 24 to 9 33 ha) was classified as one main vegetation type and one successional stage or cutting class The bryophytes in each patch were censused in randomly established squares of 10 × 10 m, supplemented by complete sampling in the rest of the patch A number of environmental variables was sampled, and the data sets treated with DCA and CCA Altogether 210 bryophytes (71 liverworts and 139 mosses) were found in the squares, and 285 (96 liverworts and 189 mosses) in the forest patches The average number of liverworts, mosses and bryophytes in forest patches increased gradually from the dry and poor to the moist and rich forest types Several red listed and other interesting spruce forest species had their only or main occurrence in the rich and humid forest, and in old cutting classes
Life history traits and resource utilisation in an assemblage of north temperateAphodiusdung beetles (Coleoptera: Scarabaeidae)
Authors: Gittings Tom , Giller Paul S.
Published: July 2006

To help understand and interpret the structure and function ofAphodiusdung beetle assemblages, life history traits and resource utilisation were studied for the ten species comprising the local assemblage of intensively grazed pastures in southern Ireland Most species were univoltine but one species (A fimetarius) was at least partly bivoltine However, temporal overlap m adult flight periods does not necessarily imply overlap in resource use Three different strategies of ovarian development were distinguished and were related to the preferred oviposition site and successional occurrence of the various species Evidence suggested that absence of mature eggs in a female's ovaries did not necessarily imply that a female was in a non‐reproductive state Two species (A prodromusandA sphacelatus) did not breed in dung, in the laboratory larvae were reared in decaying vegetation One species (A errattcus) developed m brood masses beneath the dung pat Larvae of all the other species developed within the dung pat There were consistent Interspecific differences in the larval development rates, with two species (A rufipesandA rufus) overwintering mainly as prepupae and the other species mainly as adults Previous studies have consideredAphodiusassemblages as single guilds but the detailed natural histories of these species may affect guild designation
Effects of disturbance on the reproductive potential of Lavandula stoechas, a Mediterranean sclerophyllous shrub
Authors: Herrera Javier
Published: July 2006

Studies on the effects of perturbations on Mediterranean shrub vegetation have most often emphasized the role of disturbance by fire Here I report on the effects of a relatively mild (as opposed to burning) disturbance on Lavandula stoechas The study was carried out in two adjacent plots, one in which all shrub aboveground biomass had been eliminated mechanically two years before, the other with an intact layer of shrub Although the study species lacks developed underground organs, root sprouting ensued clearing and average interplant distance at the treated site was indistinguishable from that in the control area Average percent plant mass accounted for by living branches with leaves was significantly higher for rejuvenated, cleared‐plot individuals, which also produced about twice as many flowering heads and seeds per head as their control‐plot counterparts, along with heavier individual seeds Naturally occurring seedlings survived relatively better at the cleared plot, probably as a result of the joint effects of decreased litter cover, increased water availability, and higher growth rates The average fresh mass of one‐year‐old seedlings at the Open was 243 mg, vs 10 mg of shrub‐plot seedlings No seedling survived the first summer drought out of ca 1000 seedlings that emerged from seed sown in a nearby, intact shrub stand It is hypothesized that mild, relatively local disturbance elicits competitive release, which has a major effect on both the fecundity of individuals and the demography of this species
Differences in species composition and diversity among Mediterranean grasslands with different history – the case of California and Spain
Authors: Leiva M. J. , Chapin F. S. , Ales R. Fernandez
Published: July 2006

Species composition and diversity were compared among twenty Mediterranean annual grasslands in northern and central California and central and southern Spain, encompassing climatic gradients and local site variation in topography and soils Geographic proximity was more important than environmental factors such as climate, topography and parent material in predicting the species composition of these grasslands, with Californian and Spanish grasslands sharing only 9% of the species and geographically separated regions within each country sharing only 20‐ 32% of the species This importance of geographic separation in predicting species composition suggests a strong role of dispersal limitation in determining current community composition Mean species diversity was lower in Californian than in Spanish grasslands and was negatively correlated with cover of annual grasses that tended to be greater in California than in Spain However, there were few differences in species diversity among sites within either country and patterns of species diversity were unrelated to soil fertility or productivity We suggest that current grazing regimes contribute to the greater abundance of grasses and lower species diversity of Californian than of Spanish grasslands The apparent importance of dispersal limitation and grazing m explaining differences in species composition and diversity between Californian and Spanish grasslands and within each country suggest that the structure of these grasslands has been and will continue to be sensitive to human influence
The role of foliar microfungi in mountain birch ‐ insect herbivore relationships
Authors: Lappalainen Janne H. , Helander Marjo L.
Published: July 2006

We studied the effects of epiphytic and endophytic phyllosphere fungi and pathogenic birch rust fungus infection of mountain birch Betula pubescens ssp czerepanovit trees on the larval performance of leaf beetle Phratora potaris We assessed the effects of epiphytic fungi by growing larvae on leaves from trees with manipulated fungal densities We also monitored larval perfonnance and endophytic fungal densities among tree groups classified by herbivory or rust fungus densities The differences in expenmentally manipulated epiphytic fungal densities did not affect larval relative growth rates (RGR) of the species, instead we found significant tree effects Phratora polaris RGR was higher on trees with high level of herbivory than on trees with low herbivory, nevertheless, endophyte densities between these groupings did not differ In the rust fungus expenment, P polarts performance was lowest on trees with low infection compared to no and high infection trees We also did not find correlations among tree‐specific endophyte densities and P polaris performance on high and low herbivory trees and trees classified by rust fungus infection Although antagonism among fungi and induction of tree defences cannot be excluded, we suggest that epiphytic and endophytic fungi of mountain birch have negligible effects on P polaris larval performance under natural conditions, probably due to mountain birch variability and a loose ecological connection between mountain birch and its epi‐ and endophytes Mountain birch and pathogenic birch rust have a more tightly linked relationship, which may also affect insect herbivores Still, leaf properties may play an important role and the effects will depend on the relative timing of the rust infection, herbivore development and changes in leaf quality
Mechanisms of interaction between a leguminous shrub and its understorey in a semi‐arid environment
Authors: Moro M. J. , Pugnaire F. I. , Haase P. , Puigdefábregas J.
Published: July 2006

Retama sphaerocarpa shrubs in semi‐and environments often have a dense understorey of annual and perennial herbs forming so‐called “islands of fertility” The effect of the canopy on soil fertility and microclimate and the combined effect of canopy and litter on species diversity and productivity were assessed under Retama spliaerocarpa shrubs in a semi‐and environment in southeast Spain Soil chemical properties differed significantly among three positions under the canopy, particularly between inner and outer positions The potential mineralization rate of organic matter was significantly higher in soils from an intermediate position under the canopy than in soils from either the centre and the edge Soil chemical fertility and estimated soil seed bank were highest also in soil at an intermediate position and lowest in soil from the edge The understorey flora was favoured by the lower temperature and irradiation and increased soil fertility under the shrubs canopies Species emerging from the soil seed bank separated clearly into two groups which occupied inner and outer positions under the canopy Different levels of addition of Retama litter significantly decreased species richness and the number of emerged seedlings In the field, pots placed near the centre, at an intermediate position and at the edge of the canopy of Retama shrubs differed significantly in species richness and biomass production Overall, micro‐climatic conditions combined with increased chemical fertility of the soil and inhibitory effects of litter to produce a large biomass of herbs at intermediate positions between the centre and the edge of the canopy. The high proportion of litter from annual species in that position increases the mineralization rate and hence nutrient dynamics in a process which also could benefit the shrub
Island biogeography of North European parthenogenetic Lumbricidae: I. Clone pool affinities and morphometric differentiation of Åland populations
Authors: Terhivuo Juhani , Saura Anssi
Published: July 2006

Genetic and morphometnc differences between island (Åland) and mainland (Sweden, Finland and Estonia) populations of five parthenogenetic and ecologically different Lumbricidae species were studied by means of enzyme electrophoresis and morphometric analysis Affinities of clones to the mainland populations show that the postglacial rates of clone flow to Åland differ widely among species InOctolasion cyaneum, the only clone found on Åland is not related to any of the studied clones from the nearby mainlands The Åland population evidently originates from one long dispersal jump through human agency The Åland clone pool of the anthropochorousAporrectodea roseais rich As many as 98% of the worms and 82% of the clones belong to genotypes found in the mainland populations Åland is an intergradation zone ofA roseaclones that have arrived from the west (Sweden) and from the east (Finland and Estonia) The more intense cultural connections to Sweden explain the higher clonal affinities thatA roseain Åland shows to the west than to the east There are not manyOctolasion tyrtaeumclones on Åland The few that are present are mainly clones also found on the mainlands On ÅlandEisemella tetraedrahas extensive diversity but low clonal affinities to the mainland populations This also holds true forDendrobaena octaedrabut clonal affinities are on an average higher than inE tetraedraThe Aland clone pool ofD octaedrashows more affinities to Finland than to the other mainlands Probably the main factor that has facilitatedD octaedraclone flow from Finland is a continuous archipelago In most species there are at least some clones that are more abundant on Åland than on the mainlands They may have a wider niche in the island environment The Åland populations ofA rosea, O tyrtaeumandD octaedradiffered particularly in somatic traits from the mainland populations The secondary reproductive traits of the parthenogens on Åland did not differ from the mainland populations We conclude that except forO cyaneumÅland has a role as a stepping stone island in the postglacial dispersal of parthenogenetic earthworms across the Baltic Sea Different rates of flow by immigrant clones from the surrounding mainland populations have resulted in very dissimilar clone pool structures even on the same island The Åland populations also show some morphometric differences to the mainland populations
Reproductive ecology of the lacertid lizard Podarcis bocagei
Authors: Galán Pedro
Published: July 2006

This paper presents data on aspects of the reproductive ecology of a population of Podarcis bocagei in northwestern Spain, as monitored over a two‐year period (1990–1991) Data were obtained principally on the basis of mark‐recapture experiments, but also from laboratory hatching studies Mating took place between the end of March and July During the laying period, from May to July, 8 5% of reproductive females produced three clutches, 52 1% two clutches, and 39 4% one clutch In general, single clutches were produced by small females Only a small proportion of large females produced three clutches Mean clutch size was 4 8 eggs (range 4–7) in May, 4 3 (2–6) in June and 3 9 (2–4) in July There was sigmficant variation in the mean snout‐to‐vent length (SVL) of females laying in each month of the season Both clutch size and mean single‐egg volume increased with mother's SVL There was a significant partial correlation between egg volume and clutch size when both mother's SVL and month of laying were held constant There was no significant between‐year variation in clutch size, breeding females' SVL, egg weight or relative clutch mass A delay in the timing of reproductive events in one year (1991) is attributable to adverse weather conditions during early spring Hatching occurred between July and September Hatch success (as estimated in 1989, 1990 and 1991 from natural nests at the study site) was high, ranging from 83% in 1991 to 91% in 1989 The mean SVL of female hatchlings was greater than that of male hatchlings By contrast, adult females had lower mean SVL than adult males
Species richness covariance in higher taxa: empirical tests of the biodiversity indicator concept
Authors: Prendergast J. R. , Eversham B. C.
Published: July 2006

The distribution of much of the world's biodiversity is poorly known. It is suggested that the species richness of certain Indicator taxa may reflect that of other, poorly studied taxa, making the mapping of individual taxa uneccessary and providing a guide to conservationists. In this paper we examine this proposition at a spatial scale relevant to practical conservation We show that the relationship between the species richnesses of certain higher taxa in Britain is spatially highly variable and unpredictable. Britain may not be representative of other areas of the world but our results indicate that considerable further analysis is required before indicator taxa can be recruited as a reliable short cut to conservation planning
Variation in quality of mountain birch and tea‐leaved willow for mammal and insect herbivores: differences among trees, among sites and between tree species
Authors: Suomela Janne , Suominen Otso , Törvi Marja
Published: July 2006

We evaluated palatability of winter dormant tree twigs to the mountain hare Lepus tunidus and the grey‐sided vote Clethrionomys rufocanus with captive animals We tested differences among trees within sites, among sites, and between two tree species (the mountain birch Betula pubescens ssp czerepanovii and the tea‐leaved willow Salix phylicifolia) In one of the sites, we also measured growth rates of autumnal moth Epirrita autumnata larvae on the same trees that were used m preference trials with the hares and voles The differences m palatability to hares and voles were greatest at the level of tree Species, both hares and voles preferred birches over willows, but with the hare there was some overlap in palatability between the tree species There were also large and significant differences among sites and among trees within sites Within sites, variation in tree palatability seemed to be larger among willows than among birches Hares and voles may select willows at least partly on the same basis, but there was no correlation between palatability of the trees to the mammals and the growth rate of the larvae of the autumnal moth on the same trees Variation in twig palatability to the hares and voles was so large at all levels (among trees within sites, among sites and between tree species) that we suggest it also has implications for food selection of these mammalian herbivores under natural conditions