A permanent snow cover for several months is typical for large parts of Norway, Sweden and Finland. Snow layers thicker than about 20 cm insulate the soil surface and stabilize the ground temperature close to 0°C. Many ground-living invertebrates are active at this temperature in the subnivean air space. From this "base camp", some invertebrates migrate upwards to use the snow as a substrate. The intranivean fauna consists of springtails (Collembola) and mites (Acari) that are small enough to move within the narrow pores between snow crystals. The supranivean fauna consists of various invertebrates that are active on the snow surface. Some of them are Collembola that have migrated through the snow layers. However, most of them are larger insects and spiders which migrate between the subnivean and supranivean habitats following air channels which are naturally created along tree stems, bushes etc. penetrating the snow. Likewise, certain Chironomidae and Plecoptera, hatching from winter-open rivers and brooks, are active on the snow surface. The supranivean arthropod fauna has the following characteristics: 1. It is a weather dependent assemblage of species, coming and going with changes in air temperature, cloud cover, and wind. Below ca. -6°C animals are absent, but at temperatures around or above zero, many groups can be simultaneously active on snow. 2. The snow surface fauna shows phenological changes throughout the winter, as certain species and groups are mainly active during certain months. 3. Some invertebrates are highly specialized and take advantage of the snow surface as an arena in their life cycle. Examples are Hypogastrura socialis (Collembola), and the two wingless insects Chionea sp. (Diptera: Limoniidae) and Boreus sp. (Mecoptera). They use the smooth snow surface for efficient migration. Chionea sp. and Boreus sp. lay their eggs during the snow-covered period, while H. socialis migrates to create new colonies. The cold tolerant spider Bolephthyphantes index is unique in constructing webs in small depressions on the snow, to catch migrating Collembola. Various adaptations for using the snow as a substrate are discussed. Besides physiological and morphological adaptations, snow surface arthropods show special behavioural adaptations. Most conspicuous is the ability of several Collembola species to navigate during migration, using the position of the sun for orientation. Furthermore, in Collembola and Mecoptera, jumping as an original mechanism to escape predators has independently evolved into a migrating mechanism. An evolutionary potential exists for more invertebrate groups to take advantage of snow as a substrate in their life cycle. For instance, several more cold tolerant spiders might evolve the ability to catch migrating Collembola on snow.
Only in the southern part of the Iberian Peninsula the large white butterfly Pieris brassicae was recorded to pass the summer in pupal aestivation, induced by long-day photoperiods. It is not clear why this photoperiodic response is regionally restricted. We investigated whether the change of life history in P. brassicae may affect the infestation by parasites. This was done by testing the coincidence of photoperiodic responses in both the host P. brassicae and in its main parasitoid Cotesia glomerata. While the response under short-day conditions was very similar in both species, no summer dormancy of any type was found in the parasitoid at photophases >= 15h and temperatures of 15°-25°C in contrast to 100% aestivation in the host. We suggest that aestivation is a response which allows the host to desynchronise its life cycle from that of its parasitoid. This is effective because parasitoid wasps cannot pass the temporary absence of suitable host stages by a similar developmental rest. C. glomerata is then forced to switch to less adequate host species which diminishes its reproductive success.
Vegetation on mountains is expected to react in a highly sensitive way to climate change and species losses are predicted in the near future. By means of monitoring studies changes in species diversity can be continuously recorded. In this paper the results of a 7-year study in the Southern Alps are reported. As part of the worldwide network GLORIA (The Global Observation Research Initiative in Alpine Environments) four summits, at altitudes ranging from the treeline to the alpine-subnival ecotone (2199, 2463, 2757 and 2893 m a.s.l.) in the Dolomites (northern Italy) were studied. Sites on the four summits were used to determine the effects of climate warming and observe changes in the numbers of species of vascular plants, frequency and composition. It is hypothesized that ‘thermophilization’ is likely to occur over a period of 7 years (i.e. species from lower altitudes are expected to migrate to the summits due to climate warming). It is also hypothesized that nival, alpine-subnival and endemic species might decrease due to competitive displacement by species from lower altitudes. The summit areas were comprehensively sampled (from the highest point down to the 10 m contour line) in 2001, 2006 and 2008. In addition, 4 × 1 m2 permanent plots located 5 m below the highest summit point on the north, south, east and west sides of each summit were sampled. The results of revisiting the summits indicate that the number of species increased on all four summits, with the greatest gains (15% and 18%) recorded on the two highest summits and moderate gains (4% and 9%) on the two lower summits. Species’ frequencies within the 1 m2 plots also increased during the 2001–2008 period. A thermophilization trend was demonstrated in which species with distribution centres in the montane or tree line zones were found for the first time on three of the summits. On the lowest summit, the vigorous growth of trees and establishment of new saplings indicate an upward migration of the forest boundary. Species that disappeared from the four summits belonged to species with different altitudinal ranges; however, nival and subnival-alpine species remained. One endemic species, Potentilla nitida, disappeared from the highest summit. Further changes and clearer trends are expected in the next decade.
The article deals with the question how EU anti-discrimination law and migration law are inter- related. The concept of fundamental market freedoms and the prohibition of discrimination based on na- tionality have approximated the status of state nationals and Union citizens. General human rights law, on the other hand, has strengthened the legal status of third-country nationals, also in the field of migration law. The combination of both approaches in the light of current anti-discrimination directives and activist human rights jurisprudence may lead to confusion.
Historical data sources on abundance of organisms are valuable for determining responses of those organisms to climate change and coincidence of changes amongst different organisms. We investigate data on the general abundance of Lepidoptera over an 89 year period 1864-1952. We related abundance to monthly mean temperature and precipitation and the winter North Atlantic Oscillation (NAO) index, and to numbers of migrants from an independent source. Abundances of Lepidoptera were significantly positively correlated with current year temperatures for May to September and November and significantly negatively correlated with temperatures in January. Numbers were also negatively correlated with rainfall for April and May and annual total of the current year and with August in the previous year. Abundance of Lepidoptera decreased significantly with an increasing winter NAO index. Increased overall abundance in Lepidoptera coincided significantly with increased numbers of migrants. The climate associations were very similar to those previously reported for butterfly data collected by the British Butterfly Monitoring Scheme; although warm and drier summers were generally beneficial to Lepidoptera populations, wet summers and winters and mild winters were not. We discuss the implications for Lepidoptera biology and populations in regions of Britain in the face of projected climate changes.
Two blacklight traps were operated in a non-agricultural setting in Cary, North Carolina, USA, from spring through fall in 2004 and 2005 and all Coccinellidae collected and identified. More than 1300 lady beetles were collected in each of the two years, with Harmonia axyridis dominant (> 98%) and collected consistently over the course of the trapping period. Although other coccinellid species were observed in the vicinity of the traps during photophase, their appearance in blacklight traps was negligible. Harmonia axyridis exhibited a distinct diel periodicity in appearance at the traps, beginning approximately an hour after sunset and ending about midnight. Sunrise and sunset collections from flight interference and sticky traps in a local alfalfa field suggest that H. axyridis may be more flight active during the scotophase than Coleomegilla maculata, Hippodamia convergens, and Coccinella septempunctata. This study supports the suggestion that blacklight traps give a biased depiction of coccinellid species composition in a given area, and indicates that seasonal and circadian thresholds for flight activity, phototaxis, or both in H. axyridis may diverge from those in most other Coccinellidae., Christine A. Nalepa., and Obsahuje seznam literatury
Daily emigrations of non-native age 0 and age 1 potamodromous (fluvial) rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta
were investigated in two Missouri River tributaries, USA over the period 1998-2002. The patterns of emigration for both age 0 and age 1 fish of both species were highly variable, sometimes showing bimodal (spring and fall) emigrations and other times less well defined patterns. Peak timing of age 0 emigration was also highly variable among years (up to 5 months) and more
variable than the timing of age 1 emigrations (more than two months). Emigrations were preferentially associated with increasing photoperiod before June 22, with water temperatures from 7.5 to 12.5 °C, and often followed sudden increases in stream discharge. More emigrations were associated with the new moon phase as opposed to the full moon phase. In an analysis of models of emigration (2 rivers × 2 species × 2 ages/species
× 31 model combinations for five categorical variables – year, temperature, discharge, moon phase, and photoperiod) using the information-theoretic approach, none of the models were especially effective at explaining emigrations; for the 16 models (i.e. the two with the lowest AIC per river, species and age), no corresponding multiple linear regression model explained more than 41 % of the emigration, and most other models explained considerably less. Results of this study suggest that emigrations of both brown and rainbow trout as part of their fluvial life histories are potentially influenced by a variety of environmental factors, and can be expected to show considerable variation yearly based on the complex, poorly defined genetic origins of the fish and the highly variable climatic conditions associated with the Missouri River Basin.
The article describes the approach and method of Family Housing Pathways. This process of gathering and presenting data makes it possible to include the extended family’s housing resources, the management of these resources, and the transformations of households within a family. Twenty-eight Family Housing Pathways were gathered and collected as part of an assignment given to students as part of an undergraduate course on housing problems. The exercise shed light on recurring themes in the transformation of the housing system in Poland that influence individual and family management of housing resources. Even a sample of relatively privileged families demonstrates that housing is clearly a crucial dimension, especially in times of transition, e.g. in post-communist Poland after 1989. The Family Housing Pathways approach could be a promising tool as well as an approach that combines biographical and historical housing perspectives, without losing sight of concerns of a practical and ethical nature.
The effect of water temperature and flow on the migration of fish was observed using weekly inspections of a fishpass on the lowland section of the River Elbe (Střekov, Czech Republic) from spring to fall 2003 and 2004. The effect was examined separately for immature (up to 2 years old) and adult fish and also the most abundant species (roach Rutilus rutilus, bleak Alburnus alburnus, chub Squalius cephalus, gudgeon Gobio gobio). More than 13 thousand fish from 23 species were recorded in the fishpass during both years. The highest levels of fish occurrence in the fishpass were observed during the spring spawning migrations of adults (April-May) as well as during the late summer and fall migrations of adult and immature fish (September-November). While the total number of both fish age categories was significantly related to the interaction of water temperature and flow, however, responses of individual species and age categories differed from each other. The numbers of adult bleak, chub and gudgeon increased with higher temperature. The maximum numbers of adult bleak migrated at medium values of temperature (15-20 °C) and flow (140-270 m3 s–1). The abundances of adult chub and adult plus immature gudgeon were higher with higher flow. The numbers of immature bleak and chub decreased with increasing flow. The numbers of adult and immature roach were influenced only by water flow with maximal numbers migrating under medium values of flow. Generally, we observed that immature fish and small- and middle-sized species required lower values of water flow than adult fish or large species to facilitate their movement. The exception was gudgeon, which required higher values of flow for its migration, a feature that could be related to its bottom dwelling nature or rheophily.
Molecular markers can be used to infer the demographic history of a given species, but many historic processes simultaneously impact multiple species. Thus, comparative historical demography has the potential to provide insight into drivers of evolution. In this study, we used nuclear DNA (nDNA) sequences to corroborate (or refute) demographic inferences based on earlier mitochondrial DNA (mtDNA) data from 16 species of Hispaniola birds. Our previously published analysis suggested population expansion in five of six migratory species (following glacial retreat in North America), with less evidence of expansion in non-migratory species. Additional molecular markers should reduce locus-specific bias, and so we generated sequence data for several nuclear loci. Test statistics associated with the nDNA provided only equivocal evidence for population expansion in 10 of the 16 species. Discordance between mtDNA and nDNA is not uncommon because the two genomes are exposed to different selective pressures and have different effective population sizes and modes of inheritance. The nDNA analyses reported here cast some doubt on our earlier mtDNA inferences. They also suggest that the signal to noise ratio of demographic statistics is typically low because of the inherent variability in selective regimes and coalescence across loci.