bluuebunny/crossref_metadata_2025 huggingface dataset:
Landscape and area effects on beetle assemblages in Ontario
Authors: Burke Dawn , Goulet Henri
Published: July 2006

We compared beetles collected from eight forest fragments in a suburban‐agricultural setting and one contiguous forest in south‐central Ontario. Samples were collected by pan traps from the interior of continuous forest and upland deciduous forest fragments ranging in size from 43 to 2350 ha. The pooled sample was composed of 4561 individuals from 117 species. Differences in beetle assemblages was primarily due to variation in patch isolation, although actual fragment size had a significant effect on the abundance of native and forest specializing carabid species, and the amount of forest interior habitat had a significant effect on the total number of beetle species and ground beetle species richness (family Carabidae). Fragments which were less isolated on a local scale (within a 2 km radius) had a species composition most similar to that found in continuous forest, regardless of whether the actual forest area was small or large. Marked differences in abundance and biomass were also attributed to variation in the amount of local forest cover. We suggest that a reduction in patch isolation may be an appropriate conservation strategy to improve beetle diversity and abundance in fragmented landscapes.
Climate and woody plant diversity in southern Africa: relationships at species, genus and family levels
Authors: O'Brien E. M. , Whittaker R. J. , Field R.
Published: July 2006

Woody plant richness across southern Africa was analysed and related to climate–based water–energy dynamics. The analyses, which were based on an equal–area grid system, were undertaken at the genus and family levels and compared with results previously obtained at the species level. In all cases– climate accounts for most of the variation in richness (74–79%,). with richness being a linear function of liquid water and a parabolic function of energy. There is some variation in the particulars of climate's relationship to richness between the three taxonomic levels considered. But, the overall similarity of the outcomes at all three taxonomic levels supports the view that independent and predictable geographic variation in water‐energy dynamics exerts a first‐order control on the realised distributional ranges, and thus richness, of surviving and evolving taxa.
Bark beetle diversity at different spatial scales
Authors: Peltonen Mikko , Heliövaara Kari , Väisänen Rauno , Keronen Jaakko
Published: July 2006

To determine how the scale of observation affects ecological patterns we studied bark beetle (Coleoptera, Scolytidae) diversity in southern Finland. A block covering 160 × 160 m of a forest was delimited in four stands of different site types. Each block was divided into 256 squares (10 × 10 m) in which the occurrence of bark beetle species was recorded. In addition, environmental variables describing site type, trees, and breeding material appropriate for bark beetles were measured. The species presence/absence data were combined at different scales of resolution (10 × 10 m. 20 × 20 m, 40 × 40 m, 80 × 80 m, 160 × 160 m). At the finest scale a recently thinned pine stand showed relatively high diversity compared to other study stands due to a few evenly distributed and abundant species. However, the species diversity increased faster toward larger scales in mature spruce stands with several sporadically distributed species. According to logistic regression analyses, breeding material and site characteristics explained the occurrence of most beetle species. However, these variables did not explain the occurrence of the six most frequent species, probably because the factors regulating their distribution and occurrence operate at larger scales.
Macroecological patterns in British breeding birds: covariation of species’geographical range sizes at differing spatial scales
Authors: Gregory Richard D. , Blackburn Tim M.
Published: July 2006

The availability of high quality data on the distribution and abundance of British birds at the national scale means that this fauna is the basis for a growing body of macroecological study. Nevertheless. questions remain about how representative of wider patterns the distributions and abundances of birds in Britain may be. Here, we use data on the British. European and global breeding distributions of British birds to show that species that are widespread in Britain also tend to be widespread across larger regions. These results hold for both residents and migrants separately, and when controlling for the phylogenetic related ness of species. Species with wide latitudinal spans in Europe also tend to have large British ranges, with the largest British ranges exhibited by species inhabiting mid‐latitudes in Europe. These results demonstrate that the distributions of birds within Britain are not simply idiosyacratic. but do reflect aspects of their broader distributions.
The breeding productivity of dark‐bellied brent geese and curlew sandpipers in relation to changes in the numbers of arctic foxes and lemmings on the Taimyr Peninsula, Siberia —
Authors: Summers Ron W. , Underhill Les G. , Syroechkovski Evgeny E.
Published: July 2006

There were about three‐year cycles in the populations of arctic foxes, and the breeding productivities of brent geese and curlew sandpipers on the Taimyr Peninsula, Russia, The populations of arctic foxes and lemmings changed in synchrony. The breeding productivities of the birds tended to be good when the arctic foxes were increasing in numbers and poor when the arctic foxes were decreasing. There was a negative relationship between arctic fox numbers (or occupied lairs) and the breeding productivity of brent geese in the following year. Although there was evidence of wide‐spread synchrony In the lemming cycle across the Taimyr Peninsula, some localities showed differences, However, such sites would still have been influenced by the general pattern of fox abundance in the typical tundra zone of the Taimyr Peninsula, where most of the arctic foxes breed and from which extensive movements of foxes occur after a decline in lemming numbers. The results support a prey‐switching hypothesis (also known as the alternative prey hypothesis) whereby arctic foxes, and other predators, feed largely on lemmings when these are abundant or increasing, but switch to birds when the lemming population is small or declining. The relationships between arctic foxes, lemmings and brent geese may be further influenced by snowny owls which create fox‐exclusion zones around their nests, thus providing safe nesting areas for the geese.
Parasitism and epibiosis in native and non‐native gammarids in freshwater in Ireland
Authors: Dunn Alison M. , Dick Jaimie T. A.
Published: July 2006

The introduced amphipod crustaceansGammarus pulexandG. tigrinusare displacing the nativeG. ducheni celticusin a number of freshwater sites in Northern Ireland. We investigated parasite and epibiont infection in populations in the Rivet Lagan and Lough Neagh where both native and invading species occur. Prevalence of the four parasites and epibionts observed was higher in the nativeG. d. celticusthan in the invading amphipods at both field sites. In Lough Neagh.G. d. celticusindividuals suffered higher burdens of the rotiferEmbata parasiticaand the protozoanEpistylisin comparison with the invading species. These patterns may reflect host specificity by the parasites or may result from different susceptibilities of the native and invading host species. We consider the influence of parasitism on host invasions and resulting species distributions.
Fluctuating asymmetry inSemibalanus balanoides(Crustacea: Cirripedia) at different heights on the shore
Authors: Sullivan Matthew S.
Published: July 2006

Population level studies of fluctuating asymmetry (FA) need to incorporate clinal variation in FA for proper sampling methodologies to be employed to ensure appropriate comparisons between populations are made. FA of adult acorn barnacles.Semibalanus balanoides, in the intertidal zone offers an excellent model system for looking for such variation. This study looked at the magnitude of FA ofS. balanoidesat each of three vertical heights in the barnacle zone, in two sites on the Isle of Mull, Scotland. Unsigned FA of width of sutures between tergal and scutal plates, after correcting for size and numbers of others touched, showed significant variation across the upper, mid and lower barnacle zone. Specifically, this was a U‐shaped pattern, with individuals in the mid‐Zone being more symmetrical than those at the two extremes. It is proposed that high levels of FA in the upper zone are due to exposure stresses, while biotic factors such as competition impose developmental stress in the lower zone.
Screening for species potentially sensitive to habitat fragmentation
Authors: Dettki Holder , Edman Mattias , Esseen Per‐Anders , Hedenås Henrik , Jonsson Bengt Gunnar , Kruys Nicholas , Moen Jon , Renhorn Karl‐Erik
Published: July 2006

FORUM is a lighter channel of communication between readers and contributors: it aims to stimulate discussion and debate, particularly by presenting new ideas and by suggesting alternative interpretations to the more formal research papers published in ECOGRAPHY and elsewhere. A lighter prose is encouraged and no summary is required. Contributions should be concise and to the point, with a relatively short bibliography. Formal research papers, however short, will not be considered.
Environmental correlates of tree alpha‐diversity in New Zealand primary forests
Authors: Leathwick J. R. , Burns B. R. , Clarkson B. D.
Published: July 2006

Correlations between environment and tree alpha‐diversity in New Zealand's primary forests were examined using an extensive quantitative dataset (14 540 plots). Generalised additive models were used to examine relationships between species richness and temperature, solar radiation, root‐zone moisture deficit, relative humidity, lithology, drainage, and plot size for all trees (112 species), and separately for broadleaved trees (88 species), conifers (17), and the genus Nothofagus (4). Diversity both for all tree species and for broadleaved trees was predicted to be highest on sites with high temperatures, high solar radiation, and high soil and atmospheric moisture, and on sedimentary and basaltic substrates. Highest conifer diversity was predicted on sites with intermediate temperatures, low solar radiation, high root‐zone and atmospheric moisture, and rhyolitic and Quaternary substrates, particularly where drainage was impeded. Highest Nothofagus diversity was predicted for sites combining low temperatures, high solar radiation, high root‐zone moisture but low atmospheric moisture, and on granitic substrates. Differences in diversity between the species groups on different lithologies are interpreted as rejecting both the effects of variation in large‐scale disturbance histories, and the effects of confounding environmental factors associated with particular substrates. There were also significant interactions between species groups: both broadleaved tree and conifer richness were predicted to be lower on sites where one or more Nothofagus spp. — all of which have marked patchiness in their distribution — are present. Although these results are consistent with the hypothesis that tree diversity is highest on sites conducive to high productivity, history is also indicated as an important determinant of tree diversity in New Zealand.
Forest edges and habitat selection in birds: a functional approach
Authors: McCollin Duncan
Published: July 2006

Edge effects encompass a complex panoply of biotic and biotic phenomena across woodlan borders. I identify four main explanations which have been proposed to explain avian habital selection with respect to forest edges: 1) individualistic resource and patch use. 2) biotic interactions: 3) microclimate modification 4) changes in vegetation structure. In relates nest site location in woodlands relative to the edge to the proximity of food resources. It is shown that all other things being equal birds which are wholly dependent on resources found within woodlands will tend to avid forest edges. Woodland species dependent upon resources found in adjacent habitats will tend to be found near to edges to enable their exploitation. 2) identifies competition predation and brood parasitism as factor which have the potential to influence bird habitat selection near edges. 3) identifies microclimate modification as a potential influence which may are directly on nesting success or indirectly through its effects on food supply: 4) relates the activities of birds such as nesting feeding or Research on edge effects of birds in woodland has provided few practical recommendations to conservation managers. Forest edge management needs to take into account the multiple cause and defects which influence habitat selection at the edge and to target species of conservation concern.
Coincidence in the distributions of butterflies and their foodplants
Authors: Quinn Rachel M. , Caston Kevin J. , Roy David B.
Published: July 2006

The relationship between the geographic distribution of consumers and of their hosts (foodplants) is examined using the resident butterfly fauna of Britain. On average, butterfly species that feed on more widely distributed hosts are themselves more widely distributed. However, the relationship is approximately triangular and the upper constraint imposed by the range sizes of hosts is not closely followed; some species have much more restricted ranges than their hosts have. There is no relationship between the proportion of the range of the foodplant that is occupied and the size of the range of the foodplant. Monopbagous butterfly species have smaller range sizes than polyphagous species, probably as a consequence of the greater potential range sizes of the latter. Those plant species that are used as hosts by butterflies have larger range sizes than expected by chance, and individual polyphagous butterfly species tend disproportionately to be found in areas containing larger numbers of their host plant species. In sum, this study reveals a complex relationship between the distribution of butterflies and that of their resources (foodplants).
Variation in resource exploitation along an altitudinal gradient: the willow psyllids (Cacopsylla spp.) on Salix lapponum
Authors: Hill Jane K. , Hamer Keith C. , Hodkinson Ian D.
Published: July 2006

Three congeneric species of Salix‐fedding psyllid Cacospsylla spp. Occur along an altitudinal gradient (988 1222 m. a.s.l.) in southern Norway. The 27‐km transect covered the local altitudinal range of the three species. Each species showed a different characteristic altitudinal distribution: C. propinqua occurred over the entire altitudinal range of the transect C. palmeni was restricted to higher altitude and C brunneipennis occurred manly at lower altitudes. This pattern of local altitudinal distribution mirrored the broader geographical distributions of these psyllids along latitudinal gradients. All three species developed on willow catkins, but also made use of leaves. Species differed in their use of leaves with >10% of sampled individuals of C. brunncipennis or C. Palmeni developing on leaves compared with up to 80% in C. propinqua. The proportion of C. propinqua nymphs developing on catkins increased with altitude and was also related to the temporal and spatial availability of catkins but was not a result of competitive displacement from catkins. Nitrogen concentration of host plants did not affect the proportions of C propinqua on leaves or catkins and was not related to adult size or psyllid density on catkins. Patterns or resource use are discussed in relation to differences in the distribution and abundance of the three species along the transect.
Community structure of crustacean zooplankton in subarctic ponds — effects of altitude and physical heterogeneity
Authors: Rautio Milla
Published: July 2006

Crustacean zooplankton (Cladocera. Copepoda) distribution patterns, community composition and response to altitude, temperature, pH and surface area were studied in 17 fishless subarctic ponds in the Kilpisjärvi area, NW Finnish Lapland. Despite their harshness, the ponds harboured diverse groups of zooplankton Altogether 50 species were found from ice‐out in June‐August 1994. There was both a marked decline in the species number and a change in the composition of pond communities with increasing altitude and decreasing temperature as well as decreasing pH. Pond surface area was least significant in determining the species composition Ponds at low elevations harboured up to 21 species while the fell top ponds usually had > 10 species. Chydoridaen cladocerans were the most dominant group even though their number greatly diminished in ponds above the timber line.
Seasonal use by birds of stream‐side riparian habitat in coniferous forest of northcentral British Columbia
Authors: Wiebe Karen L. , Martin Kathy
Published: July 2006

To determine use of riparian habitats by birds in the northern coniferous forest of British Columbia, we censused birds and vegetation along 500 m transects placed parallel and perpendicular to three second‐order streams. Censuses were conducted during spring, summer, autumn, and winter to investigate how use of riparian habitat changed seasonally. Stream‐side riparian zones were characterized by a dense understorey of deciduous vegetation not found in the upslope forest. Nine bird species preferred the riparian understorey for breeding, six preferred it only during migration. Neotropical migrants (16 of 46 species) were more closely associated with stream‐sides than year‐round residents (11 species). Some breeding birds (five species) were significantly negatively associated with riparian habitats. The density of riparian birds declined with distance upstream but did not decline up to 250 m away from the stream. The more extensive riparian areas downstream supported a greater density of birds in all seasons compared to upstream areas, but more species only in spring and autumn. Species that nested in non‐riparian areas in summer used riparian habitat in autumn, making riparian corridors in the northern coniferous forest important during migration. Maintaining both riparian and upslope habitats is necessary to preserve species diversity al the landscape level.
Dynamics of intestinal coccidia in peak density Microtus agrestis, Microtus oeconomus and Clethrionomus glareolus populations in Finland
Authors: Laakkonen Juha , Oksanen Antti , Soveri Timo , Henttonen Heikki
Published: July 2006

Study of seasonal changes in the occurrence of Eimeria spp. in Microtus agrestis, Clethrionomys glareolus and Microtus oeconomus populations in Finland showed distinct seasonal variation in all three host species: the peaks occurred in both prevalence and density of infection in early autumn. The low prevalence and density of eimerian infections before and during the main crash of vole populations in late winter indicate that these organisms, although potentially pathogenic, do not significantly contribute to the drastic decline in cyclic vole populations.
The influence of climate change on the body mass of woodrats Neotoma in an arid region of New Mexico, USA
Authors: Smith Felisa A. , Browning Hillary , Shepherd Ursula L.
Published: July 2006

Earth system scientists have recently concluded that anthropogenic induced climate change is detectable. Because many aspects of an organism's ecology and evolution are influenced by environmental temperature, this suggests temperature mediated changes may be already occurring in natural ecosystems. Using archived mammal trapping and meteorological data, we investigated local changes in climate over the past 8 yr at the Sevilleta National Wildlife Refuge in an arid region of New Mexico to determine i) if environmental conditions had altered, ii) if mean body mass of woodrats had changed over this time period, and iii) if the answers to i) and ii) were positive, were the results correlated? Body mass was chosen because it is highly sensitive to temperature and many crucial ecological and evolutionary parameters are affected by it. Our results indicate that winter temperature measures (average cold and minimum), and maximum summer temperature have changed significantly over the past 8 yr. Summer and winter temperatures have both increased by ca 2.5 to 3°C. When compared to long‐term means, all years have had significantly warmer than average minimum temperatures. Mean body mass of woodrat populations has also changed significantly over the past 8 yr, and the changes are negatively correlated with both winter and summer temperatures. We predict that additional climatic warming will lead to further decreases in the mean body mass of woodrats at the Sevilleta NWR. Since many important ecological parameters are tightly linked with body mass (e.g. fecundity, dietary strategy, home range, extinction rates, energetic requirements, predation risk, etc.), our results suggest that further climate change may lead to profound alterations in woodrat life history, and indirectly, on the dynamics and Structure of the entire community. This is in addition to any direct effect temperature may have on other plants and animals.
Population variability among three small mammal species in the semiarid Neotropics: the role of density‐dependent and density‐independent factors
Authors: Lima Mauricio , Jaksic Fabian M.
Published: July 2006

We addressed the role of density‐dependent (direct and delayed) and density‐independent (precipitation) factors in shaping the dynamics of fluctuating populations of three small mammal species. Using a stepwise regression procedure, we tested the effects of nonlagged population density (log10 Nt‐1), lagged population density (log10 Nt‐2), and annual precipitation on the per capita rate of population change of Phyllotis darwini, Akodon olivaceus, and Thylamys elegans in two habitat types of a semiarid region of Chile. The most irruptive species (P. darwini) showed direct and delayed density‐dependent effects in equatorial subpopulation, and only direct density‐dependence in polar subpopulation. The per capita rates of population change of A. olivaceus showed direct density‐dependent and precipitation effects in both habitats types, while T. elegans showed direct density‐dependence and precipitation effects in the equatorial subpopulation but only a marginal effect of direct density‐dependence in the polar subpopulation. The presence of delayed density‐dependent strongly suggests the importance of biological interactions in shaping the dramatic irruptions exhibited by P. darwini.
Faunal structures among European butterflies: evolutionary implications of bias for geography, endemism and taxonomic affiliation
Authors: Dennis Roger L. H. , Williams W. Robert , Shreeve Tim G.
Published: July 2006

European butterfly species have been classified, using four multivariate classification techniques, to faunal groups (a collection of species having similar distributions) each group having a unique geography (faunal element). Concordance occurs for 94% of species for at least three of the techniques. The faunal groups are brassed in geography, endemicity and taxonomic affiliation, indicating that they have historical and evolutionary significance. The inference is that a species by belonging to one faunal group, rather than to another, has a higher probability of being an endemic, and if it is not an endemic, then of evolving into one. This probability is influenced by affiliation to higher taxa, such as butterfly families, and thus by phylogenetic constraints. We argue that the fidelity of a species to a faunal element will affect its evolutionary pathway since, by belonging to a faunal element, a species is subject lo the distinctive processes linked to a unique landscape and its environmental conditions. Species have the capacity of switching between faunal groups owing to environmental changes impinging on their geographical ranges and epigenotypes. However, transfer of species across different groups are not of equal likelihood, being greatest between contiguous land elements and least between those restricted to islands. We suggest that conservation biology gives more attention to faunal structures: faunal groups have unique geography, are vulnerable to different macroevolutionary pressures and effectively underpin community assemblages within specific biotopes.
Invasions
Authors: Williamson Mark
Published: July 2006

Because of the damage some do, including threatening biodiversity, invasive species are a current focus of interest, particularly outside Europe. Yet invasion biology is still struggling to become analytic. Progress has been made in quantifying the proportion of invaders that succeed in various ways, and in measuring the degree of that success. Several examples, where the course of invasion has been explained, show the variation in biological processes involved. A detailed analysis, often with experiments and modelling, is necessary for a satisfactory explanation. Prediction is harder than explanation. Attempts at predicting invasions have generally been unsatisfactory. Ten reasons that may contribute to this are discussed. Progress will require defining more precisely what is to be predicted and measuring more quantitatively the ecological properties of species. Even so, predicting the ecological behaviour of a species in a new environment may be effectively impossible.
Correlation between endemism and local ecoclimatic stability documented by comparing Andean bird distributions and remotely sensed land surface data
Authors: Fjeldså Jon , Lambin Eric , Mertens Benoit
Published: July 2006

Fjeldså, J., Lambin, E, and Mertens, B. 1999, Correlation between endemism and local ecoclimatic stability documented by comparing Andean bird distributions and remotely sensed land surface data. ‐ Ecography 22: 63‐78.

Relationships between large‐scale patterns of biodiversity and ecoclimatic variability were examined using distributions of 789 Andean birds, recorded in 15’x 15’grid cells, and interannual differences in Normalized Difference Vegetation Index and Brightness Surface Temperature, calculated month by month and resampled to 15’cells. Following the east Andean treeline from 1°N to 18°S, there is no evidence of a latitudinal gradient in species richness, but a considerable local variation reflecting the habitat complexity in individual cells. The mean endemism (inverse range‐size for all species present in a given cell) shows well marked peaks. Pairwise comparisons of‘peaks’and adjacent‘lows’of endemism provide strong evidence for linking peaks of endemism with local ecoclimatic stability. The most important single factor responsible for this correlation could be orographic moderation of the impacts a south polar winds. Presently manifested as occasional winter freezes in the southern part of the tropical zone, these winds may have been a major determinant of vegetational changes during Pleistocene glacial periods. The correlations suggest that most endemics are relict populations which survived periods of global climatic change in places where these impacts were moderated. It is suggested that, by retaining relict populations, these places play a significant role in the recruitment to the regional species pool. The stable places were also centres of Andean cultures and have dense human populations. The current conservation strategy of reserving areas with few people therefore needs to be supplemented with actions to secure sustainable landuse in certain densely populated areas.
Is there a special conservation biology?
Authors: Noss Reed
Published: July 2006

Conservation biology is special to the extent that it fills useful roles in the scientific and conservation fields that are not being filled by practitioners of other disciplines. The emergence of the “new conservation biology” in the late 1970's and its blossoming in the 1980's and 1990's reflect, to a large degree, a failure of traditional academic ecology and the natural resource disciplines to address modern conservation problems adequately. Yet, to be successful conservation biology, as an interdisciplinary field, must build on the strengths of other disciplines both basic and applied. The new conservation biology grew out of concern over extinction of species, although the field has expanded to include issues about management of several levels of biological organization. I examine four controversial questions of importance to conservation biologists today: 1) are there any robust principles of conservation biology? 2) Is advocacy an appropriate activity of conservation biologists? 3) Are we educating conservation biologists properly? 4) Is conservation biology distinct from other biological and resource management disciplines? I answer three of these questions with a tentative “yes” and one (3) with a regretful “in most cases, no.” I see a need for broader Training for students of conservation biology, more emphasis on collecting basic field data, compelling applications of conservation biology to real problems, increased influence on policy, and expansion of the international scope of the discipline. If all these occur, conservation biology will by truly special.
Effects of intensity and duration of infection by a hemiparasitic plant, Rhinanthus serotinus, on growth and reproduction of a perennial grass, Agrostis capillaris
Authors: Puustinen Susanna , Salonen Veikko
Published: July 2006

Arising from annual variation in parasitic plant population densities, substantial yearly changes may occur in the parasitic load of an individual perennial host. We conducted two two‐year greenhouse pot experiments to examine the effects of varying intensities and duration of infection by an annual root hemiparasitic plant.Rhinanthus serotinus, on the growth and reproduction of its perennial host grass.Agrostis capillaris.In the first experiment, one host plant was growing either alone or under a load of 1 or 3 root hemiparasitic plants for one growing season, and during the next season all hosts continued their life free of hemiparasites. In the second experiment, the host plants either grew alone or were parasitised by 1 or 2 root hemiparasitic plants either during the first growing season only or during two successive seasons (the parasitic load being the same in the two seasons). In both experiments, the root hemiparasites markedly reduced the growth and reproduction of their perennial hosts. In the first experiment, the negative effects of parasites on host performance increased with the increase in intensity of parasitic infection from one to three parasites. The harmful effects of hemiparasitim were carried over to the following season; hosts parasitised during the previous season with one or three parasites produced significantly less biomass than those without parasites. In addition, hosts parasitised by three parasites during the first season produced significantly less panicles in the second season than those parasitised by one parasite and those without parasites. The second experiment showed that the production of biomass ofA. capillarisduring the second season was, but the production of panicles was not affected by the duration of parasitic infection. In addition, in this experiment, the second season biomass ofA. capillarisdepended on the intensity of infection (1 vs 2 parasites), but the production of panicles was unaffected by the number of parasites.
The alternation of mutualistic ant species affects the population growth of their trophobiont mealyhug
Authors: Itioka Takao , Inoue Tamiji
Published: July 2006

Many species of honeydew‐producing Homopteran insects have Tniitualistic relationships with ants which defend them against their natural enemies in return for honeydew. In many cases of this type of mtitualism (trophobiosis), a particular honioplcran can associate with a range of mutualistic ant species. We studied the influence of alternation of two ant species, Lasius niger and Pristomyrmex pungens. both of which are mutualistic partners of the citrus mealybug Pseudococcus citriculus, on population growth of their trophobiont mealybug. The growth rate of the mealybug populaiion was significantly higher with attendance by either ant species than without it throughout the year. However, in the field, the mealybug population was significantly larger on trees where a L. niger colony made its territory than on trees where a P. putigens colony made its territory. When the attending ant species changed from L. niger to P. pungens, the mealybug population significantly decreased compared with the population that L. nigcr continued to attend. In contrast, the mealybug population increased following the reverse shift, from P. pungens to L. niger. These results indicate thai, for the mealybug. L. niger is a more effective mutualistic partner than P. pungctis. This deviation was due to a difference in attack behavior by ihc two ant species. Behavioral responses by attending ants to artificial models of natural enemies were more aggressive in L. niger than in P. pungens. The territories of the two ant species were completely separated, and territory takeovers of one ant species by the other were occasionally observed. These facts suggest that interspecific competition between the two ant species is an important factor in determining the spatial distribution of the two species. Thus, we conclude that interspecific competition between the two ant species indirectly affects the population growth of their common trophobiont mealybug.
Differentiation in adaptive traits between neighbouring bog and mineral soil populations of Scots pine Pinus sylvestris
Authors: Ohlson Mikael
Published: July 2006

I used a reciprocal sowing experiment in the field to reveal differentiation in adaptive traits between two neighbouring northern populations of Scots pine Pinus sylvestris. 1 compared a peat bog population with a mineral soil population. Seedling survival was monitored during seven growing seasons and the plants were then harvested to obtain data on pine traits associated with growth and resource allocation, i.e. height, needle length, total dry weight, relative growth, proportion root and proportion needles. Seeds from the peat bog populations had lower germination capacity and were smaller than those from the mineral soil population. Despite their smaller size, the seeds from the bog population were superior for establishment of pines on the bog. On the mineral soil, the traits were strikingly similar in the two pine populations. In contrast, the traits were more variable and differentiated on the bog. Here, the native bog pines grew faster and had a larger proportion root than those originating from the population on the adjacent mineral soil. It is suggested that the differentiation between peat bog populations and mineral soil populations might represent a major direction of differentiation in northern Scots pine populations.
Grasshopper population dynamics and meteorological parameters ‐ lessons from a case study
Authors: Köhler Günter , Perner Jörg , Schumacher Jens
Published: July 2006

Population dynamics of grasshoppers differing in phenology were analysed on a xerothermic meadow in central Germany, The study was based on standardized annual sweep net samples in relation to meteorological factors |mean and maximum temperature, rainfall, sunshine) from May through September of current and previous year, respectively. Three grasshopper species, the early hatching Euthystira brachyptera, the phenologically intervening Stenohothrtis lineatus. and the late hatching Gomphocerus rufus., were investigated over ten years during three periods: 1971 74, 1983 85, 198789. By means of stepwise linear regression and a cross‐validation procedure a subset of meteorological parameters was extracted which best described the field sampling data of the grasshoppers. This subset of variables was then used in multiple linear regression analyses in order to model the long‐term population dynamics of the grasshoppers from 1971 to 1990, The selected variables for each species revealed different influences of meteorological parameter combinations reflecting the different phenologies. The dynamics of the three gomphocerine species modelled for 20 yr (1971 1990) differed both with maxima and minima in different years and in the fluctuation factors from 29 (E. brachyptera) to 155 (S. lineatus). In comparison with fluctuation trends in populations of other sites within the region some species‐specific and habitat‐specific population dynamics must be assumed. There were no significant correlations between annual aridity (precipitation‐temperature)‐indices and densities of the three populations studied.
El Niño events, precipitation patterns, and rodent outbreaks are statistically associated in semiarid Chile
Authors: Lima Mauricio , Marquet Pablo A. , Jaksic Fabian M.
Published: July 2006

In the last two decades, several researchers have noted rodent population outbreaks in semiarid South America, in association with unusually high precipitation that seemingly concurs with El Niño events. To date, no studies have been conducted to determine the statistical relationships between ENSO (El Niño Southern Oscillation) events, increased precipitation, and rodent irruptions. Here we show that: 1) there is a statistical association between ENSO events and inereased precipitation in the semiarid region of northern Chile: 2) the occurrence of rodent outbreaks in that region is statistically related with the precipitation levels of the same year: 3) the multi‐annual patterns of the total annual precipitation levels and population abundance of those rodents during the summer are positively associated. The putative chain of effects seems to start with unusually high rainfall brought by ENSO to semiarid environments, which thus respond with inereased primary productivity (herbage and seeds), which then fuels the rodent outbreaks.
Building better wildlife‐habitat models
Authors: Beutel T. S. , Beeton R. J. S. , Baxter G. S.
Published: July 2006

Wildlife‐habitat models are an important tool in wildlife management today, and by far the majority of these predict aspects of species distribution (abundance or presence) as a proxy measure of habitat quality. Unfortunately, few are tested on independent data., and of those that are, few show useful predictive skill. We demonstrate that six critical assumptions underlie distribution based wildlife‐habitat models, all of which must be valid for the model to predict habitat quality. We outline these assumptions in a meta‐model, and discuss methods for their validation. Even where all six assumptions show a high level of validity, there is still a strong likelihood that the model will not predict habitat quality. However, the meta‐model does suggest habitat quality can be predicted more accurately if distributional data are ignored, and variables more indicative of habitat quality are modelled instead.
Post‐fledging migration of common murres Uria aalge in the Baltic Sea: management implications
Authors: Olsson Olof , Fransson Thord , Larsson Kjell
Published: July 2006

In this study of common murre Uria aalge chicks, at Slora Karlsö in the Baltic Sea (Sweden), we used two data sets to investigate the post‐fledging migration to learn more on potential threats from human activities. Firstly, we radio tracked 12 chicks on average 5.1 h during their first night at sea, after jumping from the breeding cliffs in early July. Their average speed was 1,9 km h‐’and all chicks swam in a similar direction (SW) with a mean bearing of 235°. By searching an area of ca 400 km2 further off the island between two and six days after the radio tracking, we concluded that they did not stop, even temporarily, within 40 km off the island, but had continued the swimming migration. Our second data set was made up by 400 recoveries of ringed chicks. Only those recovered within eight months after fledging (until February) were included. Two birds recovered at the Polish coast in the beginning of August had moved on average 10.7 and 12.3 km day‐’(i.e. 0.45‐0.51 km h‐). In August, all chicks, except one, were found south of Gotland > 70 km away. The average distance to the recovery sites in. August was 253.5 km (n = 11). The pattern of distribution of birds reported in September. October and during the winter period from November to February was about the same as in August. The average direction from the colony lo the recovery sites was S to SW. Important findings from nature management perspective are: 1) our data suggest that the route of the chicks at least partly coincide with ship routes with at least 42000 passages each year. Hence, there is a potential for a great part of the common murre population to get in contact with oil spillage at this stage, notably in the first half of July. 2) From the 400 reported recoveries of ringed chicks we concluded that the most important over wintering areas are around Bornholm and the Bay of Gdansk. Hence, these are the most likely areas for conflicts with the fishery and oil spillage during the winter.
Changes in community and population responses across a forest‐field gradient
Authors: Meiners Scott J. , Pickett Steward T. A.
Published: July 2006

The ground‐layer vegetation of a forest‐old field edge gradient was sampled to determine the effects of the edge on spatial patterns of plant species and community attributes. Species showed individualistic responses to the forest edge, with peak abundance at different spatial positions relative to the edge. Principal components analysis resulted in three axes which explained a total of 63.2% of the variation within the data set. The first two PCA axes were related to distance to the forest edge. The third separated plots into those that were dominated by Solidago canadensis. and those that were dominated by Solidago juncea. All population and community‐level attributes varied along the edge gradient. Species richness, Shannon‐Wiener diversity, and total percent cover increased from the forest to the edge, with slight declines 60 m from the edge in the field. Among‐plot heterogeneity was higher at the edge than in either the forest or the field. Exotic species had peak abundance within 20 m of the edge inside the forest and are restricted to the edge. Most population and community‐level attributes showed edge responses on both sides of the edge. This emphasizes the need to study edges as gradients that include both disturbed and undisturbed habitats.
Diet, body condition, and reproduction of Eurasian pine martens Mantes martes during cycles in microtine density
Authors: Helldin J.‐O.
Published: July 2006

Winter diet, body condition, growth, reproduction, and age structure of pine martens Martes martes were studied during cycles in microtine density in south‐central Sweden. I analysed 398 scats collected in winters 1988 89 to 1996‐97. and 483 carcasses from martens trapped in winters 1989‐90 to 1992‐93. Microtines were the single most frequent prey category in the winter diet, and the consumption of microtines was correlated with microtine density. In the absence of microtines. pine martens increased the relative consumption of some alternative prey, most notably hares. Among adults, total food consumption, body condition, and reproductive success did not follow microtine density. Among juveniles, there were indications of lower total food consumption, smaller fat deposits, and higher trapping vulnerability, and among juvenile females also of lower body growth, when microtines were scarce. The data were, however, not consistent in this respect. I suggest that pine martens in the southern boreal region do not suffer from food shortage at microtine lows, and accordingly, that the demography of pine martens is independent of microtine cycles.
Latitudinal gradients in species diversity and Rapoport's rule revisited: a review of recent work and what can parasites teach us about the causes of the gradients?
Authors: Rohde Klaus
Published: July 2006

A review is given of recent work on latitudinal gradients in species diversity and their explanations, including Rapoport's rule. Energy input, measured by temperature or potential evapotranspiration. correlates best with the gradients. However, such a correlation does not “explain” them. It merely suggests explanations, which may be either different ceilings to diversity set by different energy levels under equilibrium conditions, recent historical events, or a gradient in effective evolutionary time (determined by speed of evolution directly driven by temperature, and by relative constancy of conditions over evolutionary time) under non‐equilibrium conditions. Marine parasites are used to show that equilibrium conditions are the exception rather than the rule among animals, It is concluded that latitudinal gradients in species diversity result from a gradient in effective evolutionary time modulated by several other factors. Dispersal abilities of many marine invertebrates are likely to be greater at low than at high latitudes, suggesting an opposite Rapppoport effect.

This is an invited Minireview on the occasion of the 50th anniversary of the Nordic Ecological Society Oikos.
Impact of cervid browsing and grazing on the terrestrial gastropod fauna in the boreal forests of Fennoscandia
Authors: Suominen Otso
Published: July 2006

Selective foraging by cervids can affect vegetation, and that in turn can have far‐reaching effects on various components of the boreal forest ecosystem. Since terrestrial gastropods are sensitive to habitat alterations, they can be expected to respond to changes caused by grazing. This study is based on gastropod specimens from two data sets that were collected with pitfall traps in order to study the effects of moose and reindeer on ground‐layer invertebrates. Invertebrates were trapped from 23 pairs of plots, where one plot was open to all animals while the other one was fenced to exclude large mammals. Half of the sites were in Finnish Lapland, where reindeer grazing was the main cause of differences between the plots; the rest were located in central Sweden and southern Finland, where moose was the most important cervid grazer. The composition of the gastropod fauna differed between grazed and ungrazed plots in both areas, and the abundance of gastropods in general and that of many species was higher in ungrazed plots (the number of gastropods caught was 17% lower in grazed than in ungrazed plots in moose sites, and 24% smaller in reindeer sites). Species richness differed significantly between grazed and ungrazed plots in the combined data of both site types, and was 15% higher in ungrazed plots. In moose sites the relative diversity (H′/H′max) of gastropods was 17% higher in grazed plots. In reindeer sites, the means of richness and diversity (H′) were considerably higher in ungrazed plots (35% and 40% respectively) but the differences were only marginally significant. By indirectly modifying the microclimate within the forest, cervids fulfil the criteria for a ‘physical ecosystem engineer’. Since the population density and distribution of terrestrial gastropods depend largely on the physical conditions of the microhabitat, the engineering effects of cervids are the most likely cause of the changes observed in the density and composition of the gastropod fauna in the boreal forest.