- [Show abstract] [Hide abstract] ABSTRACT: A family of empirically based ecological 'rules', collectively known as temperature-size rules, predicts larger body size in colder environments. This prediction is based on studies demonstrating that a wide range of ectotherms show increased body size, cell size or genome size in low-temperature habitats, or that individuals raised at low temperature become larger than conspecifics raised at higher temperature. There is thus a potential for reduction in size with global warming, affecting all levels from cell volume to body size, community composition and food webs. Increased body size may be obtained either by increasing the size or number of cells. Processes leading to changed cell size are of great interest from an ecological, physiological and evolutionary perspective. Cell size scales with fundamental properties such as genome size, growth rate, protein synthesis rates and metabolic activity, although the causal directions of these correlations are not clear. Changes in genome size will thus, in many cases, not only affect cell or body size, but also life-cycle strategies. Symmetrically, evolutionary drivers of life-history strategies may impact growth rate and thus cell size, genome size and metabolic rates. Although this goes to the core of many ecological processes, it is hard to move from correlations to causations. To the extent that temperature-driven changes in genome size result in significant differences among populations in body size, allometry or life-cycle events such as mating season, it could serve as a fast route to speciation. We offer here a novel perspective on the temperature-size rules from a 'bottom-up' perspective: how temperature may induce changes in genome size, and thus implicitly in cell size and body size of metazoans. Alternatively: how temperature-driven enlargement of cells also dictates genome-size expansion to maintain the genome-size to cell-volume ratio. We then discuss the different evolutionary drivers in aquatic versus terrestrial systems, and whether it is possible to arrive at a unifying theory that also may serve as a predictive tool related to temperature changes. This, we believe, will offer an updated review of a basic concept in ecology, and novel perspectives on the basic biological responses to temperature changes from a genomic perspective.
- [Show abstract] [Hide abstract] ABSTRACT: The Western Cape of South Africa is characterized by the hyperdiverse vegetation of the Fynbos biome. Typical fynbos vegetation is a fire-adapted sclerophyllous Mediterranean-type ecosystem on poor, sandy or stony soils. It is characterized by plants with low nutrient content producing slowly decomposing litter. Fire is recognized as a major factor for carbon and nutrient cycling in this vegetation type. However, knowledge of biological decomposition processes in this biome is limited. We used litter-bags to measure mass loss and changes in chemical composition in litter from three species representing characteristic taxa in fynbos, a Protea exima hybrid, Erica multumbellifera, and Restio multiflorus, during approximately 180 days. In addition, we used a standard litter of a species with high nutrient content, Galenia africana, and a mixture of Protea and Erica. We compare our results with a previous study from renosterveld including the geophyte Watsonia borbonica, which occurs in both vegetation types and occurs commonly in the study area. We found that decomposition rate among the true fynbos plant species P. exima, E. multumbellifera, R. multiflorus and W. borbonica varied almost eight-fold. Litter decomposition was strongly correlated to litter stoichiometry, i.e. C/N and C/P-ratios. Most litters accumulated one or several nutrients during the study period. The mixture of litters decomposed faster than expected from the results of each litter separately. Our study indicates that biological decomposition may be more important for carbon and nutrient cycling in fynbos than previously thought. These results are in accordance with recent studies showing large variation in plant litter quality within vegetation types and biomes. Such large variation in litter quality and decomposition rate suggests that some generalisations about ecosystem processes in the fynbos may need reevaluation.
Article: Springtail diversity in South Africa[Show abstract] [Hide abstract] ABSTRACT: Despite their significance in soil ecosystems and their use for investigations of soil ecosystem functioning and in bioindication elsewhere, springtails (Collembola) have not been well investigated in South Africa. Early recognition of their role in soil systems and sporadic systematic work has essentially characterised knowledge of the southern African fauna for some time. The situation is now changing as a consequence of systematic and ecological work on springtails. To date this research has focused mostly on the Cape Floristic Region and has revealed a much more diverse springtail fauna than previously known (136 identifiable species and an estimated 300 species for the Cape Floristic Region in total), including radiations in genera such as the isotomid Cryptopygus. Quantitative ecological work has shown that alpha diversity can be estimated readily and that the group may be useful for demonstrating land use impacts on soil biodiversity. Moreover, this ecological work has revealed that some disturbed sites, such as those dominated by Galenia africana, may be dominated by invasive springtail species. Investigation of the soil fauna involved in decomposition in Renosterveld and Fynbos has also revealed that biological decomposition has likely been underestimated in these vegetation types, and that the role of fire as the presumed predominant source of nutrient return to the soil may have to be re-examined. Ongoing research on the springtails will provide the information necessary for understanding and conserving soils: one of southern Africa's major natural assets.
- [Show abstract] [Hide abstract] ABSTRACT: Through evolution, nature has optimised structures and materials with a hierarchy from the macro- to the nanoscale. Biological materials are very sophisticated in the way they solve challenges associated with life. Some properties of commercial interest found in nature are self-cleaning, aerodynamic lift, anti-adhesion, water harvesting, water-floating and staying dry. Biomimetics, to learn from nature, has been used for centuries to create new innovative devices. With the use of “nanotools”, it is possible to design hierarchical surface structures with exceptional functional properties. In this paper, an overview of interesting surface properties with biomimetic potential, strategies for nanomanipulation of surfaces, potential industrial applications and the potential of using atomistic modelling to optimise surface structuring are discussed. KeywordsBiomimetics–Bioinspired–Nanotechnology–Surfaces–Superhydrophobicity–Atomistic modelling
- [Show abstract] [Hide abstract] ABSTRACT: Bovine babesiosis is regarded as a limited health problem for Norwegian cows, and the incidence has decreased markedly since the 1930s. Rare cases of babesiosis in splenectomised humans from infection with Babesia divergens and B.venatorum have been described. The objective of this study was to determine whether birds can introduce Babesia-infected ticks. There are between 30 and 85 million passerine birds that migrate to Norway every spring. Passerine birds were examined for ticks at four bird observatories along the southern Norwegian coast during the spring migrations of 2003, 2004 and 2005. The presence of Babesia was detected in the nymphs of Ixodes ricinus by real-time PCR. Positive samples were confirmed using PCR, cloning and phylogenetic analyses. Of 512 ticks examined, real-time PCR revealed five to be positive (1.0%). Of these, four generated products that indicated the presence of Babesia spp.; each of these were confirmed to be from Babesia venatorum (EU1). Two of the four B. venatorum-positive ticks were caught from birds having an eastern migratory route (P< 0.001). Birds transport millions of ticks across the North Sea, the Skagerrak and the Kattegat every year. Thus, even with the low prevalence of Babesia-infected ticks, a substantial number of infected ticks will be transported into Norway each year. Therefore, there is a continuous risk for introduction of new Babesia spp. into areas where I. ricinus can survive.
- [Show abstract] [Hide abstract] ABSTRACT: 1. Temperature and the elemental composition of food are key regulators of consumer growth rate, yet the knowledge on how these factors interact is scarce. In this study, we addressed this issue by using the rotifer Brachionus calyciflorus as a model organism. 2. Rotifers were raised at four different temperatures under a range of C/P and C/N ratios in their food and assessed the responses by analysing somatic RNA/protein ratios as a marker of growth rate. 3. Both N- and P-limited algae restricted the growth rates of rotifers. The interaction between C/P ratio of a given algae and temperature demonstrated that P limitation became intensified with increasing temperature. 4. Animals that were relieved from N limitation increased their RNA/protein ratio, as did animals fed on constant C/N ratio but with P-enriched food. This illustrates a mutual dependency and interaction between N and P in the protein synthesis by up-regulating the biosynthetic machinery, and that even while the effect of N limitation was more pronounced, P limitation was also potentially important in this species. 5. Our results provide evidence that over the tested range of temperature and food qualities, nutrient limitation in these animals was more important than the temperature effect. We also found, however, that increasing temperature can shift from P to N limitation in the consumer.
- [Show abstract] [Hide abstract] ABSTRACT: Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae) causes yearly losses of 1–2 million Euros to the stockfish industry in Lofoten, Norway. To develop an efficient management program, knowledge of its life cycle and phenology in production areas is needed. Cohort studies in a simulated Lofoten climate showed that field abundance peaks of adults in early spring and midsummer can be explained by a cohort originating from stockfish and its subsequent generations. Laboratory simulations with normal, increased, and decreased Lofoten temperatures indicate that C. vicina overwinter as a mix of larvae, pupae, and adults, and a temperature change of ± 2 °C significantly influences reproductive timing, reproductive output, and female mortality. Flies originating from stockfish reproduced during the first summer when temperatures were increased 2 °C above normal. At lower temperatures, the reproductive investment was low or absent during the first summer and the adult flies entered the winter in a diapausing state. Most offspring produced during the first summer and autumn developed continuously without maternally induced diapause, pupated during the winter, and hatched in the early spring to co-occur with their parent generation during stockfish production. Calliphora vicina showed flexibility in reproductive efforts and overwintering strategies. The high proportion of adults overwintering compared with the commonly used larval diapause strategy might be interpreted as an adaptation to exploit the stockfish resource. The majority of female C. vicina that cause damage to stockfish likely developed on fish dried the previous year, and a continuous year-long trapping is recommended to decimate the population.
- [Show abstract] [Hide abstract] ABSTRACT: Birds are capable of transporting ticks and, consequently, tick-borne pathogens over long distances and across geographical barriers such as oceans and deserts. The purpose of this study was to assess the prevalence of Borrelia spp. in ticks transported by birds by using PCR. A total of 9768 northward-migrating passerine birds was examined for ticks at 4 bird observatories along the southern Norwegian coast during their spring migration in 2003-2005. Two of the bird observatories were located on islands where flagging revealed very few or no ticks (Akerøya and Store Færder), while the other 2 were located in areas with established dense tick populations: an island, Jomfruland (>100 ticks per hour of flagging) and a mainland locality, Lista (40 ticks in one hour of flagging). Borrelia spp. were found in 70 (13.6%) of 513 examined Ixodes ricinus nymphs (19 B. afzelii, 38 B. garinii, two B. turdi, and 11 B. valaisiana) and in 14 (8.1%) of 172 examined I. ricinus larvae (ten B. garinii, one B. turdi, and three B. valaisiana). This report is the first to identify B. turdi in Europe. Ticks collected from birds of the genus Turdus (T. merula, T. philomelos, and T. iliacus) had a higher prevalence of Borrelia spp. than ticks from the other passerine genera. Ticks that were cofeeding with a Borrelia-infected tick had an increased probability of being infected with the same Borrelia species. Ticks collected on birds from the south-western locality Lista were less likely to have Borrelia than ticks found on birds from the other, more eastern localities. The Turdus spp. are particularly important, both because they carry many ticks per bird and because ticks carried by these species have a higher prevalence of Borrelia. This higher prevalence may be related to Borrelia infection of the birds or transmission of Borrelia through cofeeding. The prevalence of the different Borrelia species in ticks collected from migratory birds may be related to migration routes.
- [Show abstract] [Hide abstract] ABSTRACT: Survival and reproduction of an arctic population of Ameronothrus lineatus were studied at four constant temperatures (5, 10, 15, and 21 °C). By simulating winters in the laboratory, an adult population was followed through 3 "years". Increasing temperatures reduced adult longevity. Females survived longer than males. A temperature of 15 °C was the most favourable for reproduction, with highest larviposition rate and reproductive output. Lifetime reproductive output was also high at 10 °C, while lower numbers of larvae at 21 °C indicated the beginning of heat stress. Comparison with field data showed that the reproductive performance at 15 °C corresponded to reproduction in a natural population experiencing a mean temperature of 89 °C, suggesting a positive effect of daily temperature fluctuations. A simulated winter with freezing temperatures increased male survival and positively affected all aspects of reproduction the following laboratory summer.
- [Show abstract] [Hide abstract] ABSTRACT: Previous studies in the fynbos biome of the Western Cape, South Africa, have suggested that biological decomposition rates in the fynbos vegetation type, on poor soils, may be so low that fire is the main factor contributing to litter breakdown and nutrient release. However, the fynbos biome also comprises vegetation types on more fertile soils, such as the renosterveld. The latter is defined by the shrub Elytropappus rhinocerotis, while the shrub Galenia africana may become dominant in overgrazed areas. We examined decomposition of litter of these two species and the geophyte Watsonia borbonica in patches of renosterveld in an agricultural landscape. In particular, we sought to understand how plant species identity affects litter decomposition rates, especially through variation in litter stoichiometry. Decomposition (organic matter mass loss) varied greatly among the species, and was related to litter N and P content. G. africana, with highest nutrient content, lost 65% of its original mass after 180 days, while E. rhinocerotis had lost ca. 30%, and the very nutrient poor W. borbonica <10%. Litter placed under G. africana decomposed slightly faster than when placed under E. rhinocerotis. Over the course of the experiment, G. africana and E. rhinocerotis lost N and P, while W. borbonica showed strong accumulation of these elements. Decomposition rates of G. africana and E. rhinocerotis were substantially higher than those previously reported from fynbos vegetation, and variation among the species investigated was considerable. Our results suggest that fire may not always be the main factor contributing to litter breakdown and nutrient release in the fynbos biome. Thus, biological decomposition has likely been underestimated and, along with small-scale variation in ecosystem processes, would repay further study.
- [Show abstract] [Hide abstract] ABSTRACT: How the impacts of climate change on biological invasions will play out at the mechanistic level is not well understood. Two major hypotheses have been proposed: invasive species have a suite of traits that enhance their performance relative to indigenous ones over a reasonably wide set of circumstances; invasive species have greater phenotypic plasticity than their indigenous counterparts and will be better able to retain performance under altered conditions. Thus, two possibly independent, but complementary mechanistic perspectives can be adopted: based on trait means and on reaction norms. Here, to demonstrate how this approach might be applied to understand interactions between climate change and invasion, we investigate variation in the egg development times and their sensitivity to temperature amongst indigenous and introduced springtail species in a cool temperate ecosystem (Marion Island, 46°54′S 37°54′E) that is undergoing significant climate change. Generalized linear model analyses of the linear part of the development rate curves revealed significantly higher mean trait values in the invasive species compared to indigenous species, but no significant interactions were found when comparing the thermal reaction norms. In addition, the invasive species had a higher hatching success than the indigenous species at high temperatures. This work demonstrates the value of explicitly examining variation in trait means and reaction norms among indigenous and invasive species to understand the mechanistic basis of variable responses to climate change among these groups. KeywordsBiological invasions-Climate change-Development rate-Phenotypic plasticity-Soil arthropod
- [Show abstract] [Hide abstract] ABSTRACT: The incidence of bovine babesiosis, caused by Babesia divergens (Apicomplexa: Piroplasmida) has decreased markedly since the 1930 s, but may re-emerge as a consequence of climate change and changes in legislation and pasturing practices. This is a potentially serious disease, with both economical and animal welfare consequences. Therefore, there is a need to survey the distribution of B. divergens. We tested sera from 306 healthy pastured cows from 24 farms along the southern Norwegian coast by using an indirect immunofluorescence IgG antibody test (IFAT). Fractions of seropositive cows were compared by calculating 95% CI. The results of this test showed that 27% of the sera were positive for B. divergens antibodies. The fraction of antibody-positive sera that we detected showed a two-humped distribution, with a high fraction of positives being found in municipalities in the western and eastern parts of the study area, while the municipalities between these areas had few or no positive serum samples. Neither the farmers' observations nor the Norwegian Dairy Herd Recording System give an adequate picture of the distribution of bovine babesiosis. Serological testing of cows by using IFAT is a convenient way of screening for the presence of B. divergens in an area.
- [Show abstract] [Hide abstract] ABSTRACT: A few days of thermal acclimation (to 5 °C versus 15 °C) may strongly affect tolerance to drought stress in Collembola. To better understand this phenomenon, the effect of acclimation on water loss rate and its consequence for survival in the species Pogonognathellus flavescens Tullberg (Tomoceridae) is investigated. Acclimation does not affect the water content of hydrated animals but animals exposed to 15 °C and 76% relative humidity lose water much faster after having been acclimated to 5 °C rather than 15 °C. Tolerance to water loss is not affected; in both treatment groups, animals survive up to 40% loss of the water content recorded when fully hydrated. The percentage water content of hydrated animals decreases with size, which may explain why the proportion of initial water lost appears to be a better predictor for survival than the amount of remaining water. The proportion of initial water lost per unit time is little influenced by size in animals acclimated to 15 °C but increases with decreasing size in the group at 5 °C, indicating that acclimation affects a physiological protection against water loss.
- [Show abstract] [Hide abstract] ABSTRACT: Ticks can be transported over large distances and across geographical barriers by avian hosts. During the spring migrations of 2003 to 2005, 9,768 passerine birds from 4 bird observatories along the southern coastline of Norway were examined for ticks. Altogether, 713 birds carried a total of 517 larvae and 1,440 nymphs. The highest prevalence of tick infestation was observed in thrushes and dunnock (Prunella modularis). The degree of tick infestation varied during each season, between localities, and from year to year. Blackbirds (Turdus merula) caught in localities with many ticks had greater infestation than those from localities with few or no ticks, suggesting local tick recruitment. A similar study performed during 1965–1970 involving 2 of the bird observatories in the present study found ticks on 4.2% of birds, while we found infestation of 6.9% at the same localities (P < 0.001). With the exception of 10 nymphs and 1 larva, the predominant tick was Ixodes ricinus. Seven nymphs of Hyalomma rufipes and 1 larva of Dermacentor sp. were also found. No species of Dermacentor had previously been found in Norway.
- [Show abstract] [Hide abstract] ABSTRACT: Approximately 3000 birds, mainly passerines, caught in mist nets in the northern provinces of South Africa, were examined for ticks. A total of 178 ticks, belonging to 14 species, were recovered from 83 birds of 43 different species. Hyalomma rufipes was the most numerous tick, with 26 larvae and 109 nymphs collected, followed by Amblyomma marmoreum, with 13 larvae and two nymphs. Despite the study being conducted within the distribution range of Amblyomma hebraeum, it was not seen on any passerines, whereas three larger species were infested. The potential for small birds to spread ticks with their associated tick-borne pathogens is discussed.
- [Show abstract] [Hide abstract] ABSTRACT: This investigation examines multiple paternity in Ixodes ricinus (Acari: Ixodidae). Previous studies have shown that multiple mating occurs in this tick, but this is the first evaluation of multiple paternity. Three family groups were examined by a panel of polymorphic microsatellite loci; all ticks were bred from wild-collected engorged females with a copulating male attached. For most larvae, the attached males could be excluded as possible sire, and in the 3 tested families, at least 2 of 3 females mated successfully with more than 1 male. This finding suggests that multiple paternity is a common reproductive strategy in I. ricinus, which may have consequences for the ticks' dispersal success by increasing the genetic diversity in broods from single females colonizing new sites.
- [Show abstract] [Hide abstract] ABSTRACT: Geographic patterns of genie differentiation were compared with differentiation between karyotypes in the intertidal snail Nucella lapillus. Samples from 24 sites covering the species range in Europe and North America were analysed for allozyme variation at 16 soluble enzyme loci. Two homokaryotypes have been identified with diploid numbers 2n = 26 and 2n= 36 (variation is Robertsonian and hybrids have intermediate chromosome numbers) and samples were classified (on the basis of published data) according to karyotype. Group 1 consisted of samples from three English Channel populations of higher chromosome number (on average 2n > 32) and Group 2 consisted of the remaining 21 samples (presumed to be 2n= 26). Karyotype variation accounts for roughly the same amount of the absolute allozyme variance as geographic variation (46.3 °, and 53.7°, respectively). Yet the patterns of differentiation seen between karyotypes and with geographic separation are very different. In samples classified as 2n= 26 (Group 2), while there is a significant amount of heterogeneity (FST per locus averaged 0.128 for 10 polymorphic loci), allozyme variation occurs independently at different loci so mean genetic identity (Nei) is high: 0.972. There is only a slight decline in genetic identity with distance (genetic identity averaged 0.965 for amphi-atlantic comparisons) indicating that passive transport of juveniles or adults may contribute significantly to gene flow. Conversely, allozyme variation between karyotypes was concordant. High chromosome number populations possessed a suite of alleles at four allozyme loci (Esl-3, Lap-2, Mdh-1 and Pep-2) which were absent or rare in Group 2 samples resulting in high FST values for these loci (from 0.294 to 0.472) when karyotypic classes were combined. Consequently the mean genetic identity between these Robertsonian races is low, 0.856, and falls within the range more usually associated with congeneric comparisons than with con-specific comparisons. The mechanisms maintaining this genie difference are unclear. However the distribution of the karyotypes and physiological and morphological differences (in shell shape) between them strongly suggest that karyotypic variation in Nucella is adaptive.
- [Show abstract] [Hide abstract] ABSTRACT: The effect of patch size on the tolerance of the soil microarthropod population to an experimentally induced environmental catastrophe, a thick surface ice layer, was studied at a High Arctic site (78°55′N, 11°53′E). Such an ice layer currently occurs infrequently; however, climate change models suggest that the occurrence of such an ice layer is likely to increase in frequency. The experimental approach was a factorial design with two patch sizes, an icing treatment and controls. A thin layer of natural ice was present even in the controls and this was treated as a covariate in the analysis. The soil microarthropod fauna at the experimental site consisted of five species of Collembola and seven species of oribatid mite. The experimental surface ice layer reduced the total number of the soil microarthropods studied by 50%; however, mortality differed between mites and Collembola and species within the two taxonomic groups. Mites were very resistant and showed no significant change, Collembola more sensitive (the populations of Hypogastrura tullbergi declined by 56% and Folsomia quadrioculata by 54% in the iced treatment plots). The thin annual surface ice layer seemed to have an additional effect on H. tullbergi and the mite Lauroppia translamellata . That such a thin ice layer could reduce survival was unexpected and could play an important role in determining the extreme patchy distribution of arctic soil animals.
Norwegian Institute for Nature Research
Nidaros, Sør-Trøndelag, Norway
- Department of Arctic Ecology
University of Oslo
Kristiania (historical), Oslo County, Norway
- Department of Biosciences