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Search: L773:0307 6946 OR L773:1365 2311 > (2010-2014)

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1.
  • Brattström, Oskar, et al. (author)
  • AFLP reveals cryptic population structure in migratory European red admirals (Vanessa atalanta)
  • 2010
  • In: Ecological Entomology. - : Wiley. - 1365-2311 .- 0307-6946. ; 35:2, s. 248-252
  • Journal article (peer-reviewed)abstract
    • 2. Using the software STRUCTURE 2.2, we found two distinct genotype clusters present in different frequencies at all study sites. The frequencies of these genotypic clusters varied significantly between years within the same site. Remarkably few individuals were of mixed ancestry, indicating that some isolating mechanisms are present. Twenty-seven mtDNA haplotypes were identified but they showed no geographic structure, nor were they related to either of the two genotype clusters identified in the AFLP data. 3. Most field observations of migrating red admirals suggest a regular north-south migration pattern in Europe. Our data indicate both long-distance migration and a more variable pattern in orientation, since the composition of the two genotypic clusters shows dramatic variation between sites and years in the northern part of the distribution range.
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2.
  • Ammunét, Tea (author)
  • Invading and resident defoliators in a changing climate: cold tolerance and predictions concerning extreme winter cold as a range-limiting factor
  • 2012
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 37, s. 212-220
  • Journal article (peer-reviewed)abstract
    • 1. Winter temperatures in northern latitudes are predicted to increase markedly as a result of ongoing climate change, thus making the invasion of new insect defoliators possible. The establishment of new outbreak pest species may have major effects on northern ecosystems that are particularly sensitive to disturbances. 2. Effects of winter minimum temperatures under field and laboratory conditions were examined and limitations by minimum temperatures on future range expansion were investigated for invasive [Operophtera brumata (Lepidoptera: Geometridae)] and potentially invasive [Agriopis aurantiaria (Lepidoptera: Geometridae)] birch-feeding forest pests. The results for the studied invasive and potentially invasive moths were compared with the parameters of the resident moth species Epirrita autumnata (Lepidoptera: Geometridae). 3. The results showed tolerated critical temperatures of the invader (O. brumata) and the resident (E. autumnata) were more similar (differing only by 1 degrees C), whereas the potential invader (A. aurantiaria) was much less tolerant of cold temperatures. Although describing different stages of overwintering, results were consistent between laboratory and field studies except for those at one field location, at which other abiotic conditions are suggested to have significant influence on moth egg survival. 4. Based on the present results and expected changes in winter temperatures over the next 30 years, the range expansion of an established invasive species may be predicted. No limitations were found regarding the possible future invasion of a new pest species to northern Fennoscandia. The importance of studying a species' whole overwintering period is highlighted and further studies devoted to the effects of other abiotic factors in addition to the effects of temperature are suggested.
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3.
  • Andersson, Petter, et al. (author)
  • What shapes local density? : The importance of migration rates and local growth for density-patch size relationships in two Cionus weevils
  • 2012
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 37:1, s. 90-98
  • Journal article (peer-reviewed)abstract
    • 1. The relative effect of migration and local growth on the spatio-temporal density-distribution of two co-existing herbivorous weevils, Cionus scrophulariae L. and C. tuberculosus Scop., in 32 host plant Scrophularia nodosa L. patches of varying sizes was investigated. 2. Predictions of the temporal development of the slope in the density-patch size relationships were derived from a basic population model with scale-dependent migration rates. The model indicated that the slopes in the density-patch size relationships during the early season should be reflected by the net scaling of immigration and emigration rates, whereas the slopes during the later season should increase as a result of local growth. 3. Emigration rates of the weevils were estimated in a field experiment, were the weevils coexisted in space and time. These results were then combined with a previous estimate of immigration rates in order to determine the net scaling of migration rates. 4. The emigration rate differed between species, caused by different movement rates in small patches, which could explain differences in the general slope of the density-patch size relationships of the weevils in the natural figwort patches throughout the summer. The slopes in the relationships in the early season were largely predicted by the net scaling of migration rates. The slope also increased in the later season for C. tuberculosus, whereas the slope decreased for C. scrophulariae. 5. It was concluded that the understanding of both inter- and intra-specific variations in density-patch size relationships of insect herbivores can be improved using population models incorporating scale-dependent migration and local growth.
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4.
  • Betzholtz, Per-Eric, et al. (author)
  • Mobility is related to species traits in noctuid moths
  • 2011
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 36, s. 369-376
  • Journal article (peer-reviewed)abstract
    • Abstract. 1. Mobility is important for the understanding of how species survive infragmented landscapes and cope with increasing rates of habitat and climate change.However, mobility is a difficult trait to explore and is poorly known in most taxa.Species traits have been studied in relation to range shifts, extinction risks, andresponses to habitat area and isolation, and have also been suggested as good estimatorsof mobility. Here we explore the relation between mobility and species traits in noctuidmoths.2. We sampled noctuid moths by an automatic light-trap on an island far out in theBaltic Sea. We compared traits of the non-resident species on the island with traits ofa species pool of assumed potential migrants from the Swedish mainland.3. Mobility was significantly related to adult activity period, length of flightperiod, and the interaction between host-plant specificity and distribution area. Widelydistributed host-plant generalists were more mobile than host-plant specialists withmore restricted distribution, and species with an adult activity period in August toSeptember moved to the island to a higher extent than species with an adult activityperiod in May to July. Our results remained qualitatively robust in additional analyses,after controlling for phylogeny and including all species recorded on the island, exceptfor the trait ‘length of flight period’.4. Our results highlight the importance of the relation between mobility and speciestraits. Noctuid moths with certain traits move over longer distances than earlier known.This finding is important to include when predicting range dynamics in fragmentedand changing landscapes, and when conservation measures of species are devised.
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5.
  • Dalin, Peter, et al. (author)
  • Host-plant quality adaptively affects the diapause threshold : evidence from leaf beetles in willow plantations
  • 2012
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 37:6, s. 490-499
  • Journal article (peer-reviewed)abstract
    • 1. Voltinism of herbivorous insects can vary depending on environmental conditions. The leaf beetle Phratora vulgatissima L. is univoltine in Sweden but will sometimes initiate a second generation in short-rotation coppice (SRC) willow plantations. 2. The study investigated whether increased voltinism by P. vulgatissima in plantations can be explained by (i) rapid life-cycle development allowing two generations, or (ii) postponed diapause induction on coppiced willows. 3. In the field, no difference was found in the phenology or development of first-generation broods between plantations (S. viminalis) and natural willow habitats (S. cinerea). However, the induction of diapause occurred 12 weeks later in SRC willow plantations. 4. Laboratory experiments indicated no genetic difference in the critical day-length for diapause induction between beetles originating from plantations and natural habitats. Development time was unaffected by host-plant quality but critical day-length was prolonged by almost an hour when the beetles were reared on a non-preferred willow species (S. phylicifolia). When reared on new leaves from re-sprouting shoots of recently coppiced willow plants, diapause incidence was significantly less than when the beetles were reared on mature leaves from uncoppiced plants. 5. The study suggests that P. vulgatissima has a plastic diapause threshold influenced by host-plant quality. The use of host-plant quality as a diapause-inducing stimulus is likely to be adaptive in cases where food resources are unpredictable, such as when new host-plant tissue is produced after a disturbance. SRC willows may allow two beetle generations due to longer growing seasons of coppiced plants that grow vigorously.
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6.
  • Hamback, Peter A., et al. (author)
  • Patch size effects are more important than genetic diversity for plant-herbivore interactions in Brassica crops
  • 2010
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 35:3, s. 299-306
  • Journal article (peer-reviewed)abstract
    • 2. This paper examines the effect of intraspecific genetic diversity within Brassica fields on two Brassica specialists, cabbage root fly, and diamondback moth, and on a parasitoid attacking diamondback moths. Genetic diversity was manipulated both in a replacement and an additive design. 3. Both herbivore densities and parasitism rates were higher in smaller plots, with limited responses to increased within-plot diversity. All species showed variable densities across genotypes, and preference hierarchies were species specific. 4. Responses to plot size in root flies scaled with the diameter-to-area ratio, suggesting that patch detectability affected local density, whereas responses by diamondback moths and parasitoids deviated from this ratio. These species differences could be traced to differences in the residence time within patches, where diamondback moths typically spend longer and more variable time periods in patches than root flies. 5. The lack of response to genetic diversity by both herbivores suggests that egg-laying rates are affected by decisions on the plant and not by attraction from a distance, neither to the plant itself nor the patch. Patterns of differential attack may then be due to different acceptability for studied genotypes. 6. Future theories on insect responses to spatial heterogeneity should focus on species traits and how traits interact with information landscapes in the field.
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7.
  • Johansen, Aleksandra I., 1980-, et al. (author)
  • Adaptive change in protective coloration in adultstriated shieldbugs Graphosoma lineatum (Heteroptera:Pentatomidae) : test of detectability of two colour formsby avian predators
  • 2010
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 35:5, s. 602-610
  • Journal article (peer-reviewed)abstract
    • 1. Protective coloration in insects may be aposematic or cryptic, and some species change defensive strategy between instars. In Sweden, the adult striated shieldbugs Graphosoma lineatum (Heteroptera: Pentatomidae) undergo a seasonal colour change from pale brown and black striation in the pre-hibernating adults, to red and black striation in the same post-hibernating individuals. To the human eye the pre-hibernating adults appear cryptic against the withered late summer vegetation, whereas the red and black post-hibernating adults appear aposematic. This suggests a possibility of a functional colour change. However, what is cryptic to the human eye is not necessarily cryptic to a potential predator. 2. Therefore we tested the effect of coloration in adult G. lineatum on their detectability for avian predators. Great tits (Parus major) were trained to eat sunflower seeds hidden inside the emptied exoskeletons of pale or red G. lineatum. Then the detection time for both colour forms was measured in a dry vegetation environment. 3. The birds required a longer time to find the pale form of G. lineatum than the red one. The pale form appears more cryptic on withered late summer vegetation than the red form, not only to the human eye but also to avian predators. The result supports the idea that the adult individuals of G. lineatum undergo a functional change from a cryptic protective coloration to an aposematic one.
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8.
  • Klapwijk, Maartje (author)
  • Spatial ecology of multiple parasitoids of a patchily-distributed host: implications for species coexistence
  • 2011
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 36, s. 212-220
  • Journal article (peer-reviewed)abstract
    • 1. The coexistence of multiple species sharing similar but spatially fragmented resources (e.g. parasitoids sharing a host species) may depend on their relative competitive and dispersal abilities, or on fine-scale resource partitioning. Four generalist and one specialist parasitoid species associated with the holly leaf miner, Phytomyza ilicis, in a woodland network of 127 holly trees were investigated. 2. To understand coexistence and persistence of these potential competitors, patterns of occurrence in relation to patch size and isolation, vertical stratum within patches, and incidence and abundance of potential competitors were documented. Field experiments creating empty habitat patches suggested that dispersal rather than local demographic processes determines abundance and incidence. 3. Parasitoids showed species-specific responses to patch properties, with the incidence of species determined mostly by patch size. Parasitism rates were less clearly related to patch characteristics, but parasitism rates for most species were lower in patches where the numerically dominant parasitoid species, Chrysocharis gemma, was present. No evidence of vertical stratification was found in species composition or abundance within patches, making it unlikely that coexistence is enhanced by fine-scale resource division. 4. Overall, the patterns detected may be attributed to the distribution of C. gemma and differences in species’ ecology other than dispersal ability. The life history of C. gemma may allow it to pre-emptively exploit a large fraction of the available hosts, avoiding direct competition with other parasitoids. In contrast, direct competition is more likely among the pupal parasitoids Cyrtogaster vulgaris, Chrysocharis pubicornis, and Sphegigaster flavicornis which have a similar biology and phenology. For these species, coexistence may be facilitated by contrasting incidence in relation to patch size and isolation
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9.
  • Ronnås, Cecilia, et al. (author)
  • Effects of colony size on larval performance in a processionary moth
  • 2010
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 35, s. 436-445
  • Journal article (peer-reviewed)abstract
    • 1. Some lepidopteran species have larvae that live gregariously, especially in early instars. Colony-living species may benefit from improved protection from predators, thermoregulation, and feeding facilitation, for example.2. While many studies have compared solitary and gregarious life styles, few data exist as to the relationship between size of the larval colony and larval performance in gregarious species. The present study was aimed at understanding the importance of colony size for growth and survival of the northern pine processionary moth (Thaumetopoea pinivora) larvae.3. Field studies, comparing three different sizes of colonies of T. pinivora larvae, showed that individuals in larger colonies had a higher survival rate compared with those living in smaller colonies and also a faster growth rate.4. The higher survival rate of large colonies was attributed to improved protection from predacious arthropods.5. In early spring, the young larvae bask in the sun to increase their body temperature. In field experiments the thermal gain was higher in large colonies, and individuals in such colonies also grew faster. As growth rate was not affected by colony size when the ability to bask was experimentally removed in a laboratory experiment, the higher growth rate of the larger colonies was probably due to improved thermoregulation rather than feeding facilitation.6. The size of larval colonies of gregarious insects depends on natural mortality events as well as on female oviposition strategy. Our results show that decreasing colony size can lead to a reduction in growth rate and survival. It is therefore important to understand whether or not small colonies will benefit equally from the gregarious behaviour.
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10.
  • Slove, Jessica, 1980-, et al. (author)
  • Phylogenetic analysis of the latitude-niche breadth hypothesis in the butterfly subfamily Nymphalinae
  • 2010
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 35:6, s. 768-774
  • Journal article (peer-reviewed)abstract
    • One possible explanation for the latitudinal gradient in species richness often demonstrated is a related gradient in niche breadth, which may allow for denser species packing in the more stable environments at low latitudes. The evidence for such a gradient is, however, ambiguous, and the results have varied as much as the methods. Several studies have considered the non-independence of species, but few have performed explicit phylogenetic analyses. In the present study, we tested for a correlation between diet breadth and latitude of distribution in Nymphalinae butterflies using generalised estimating equations (GEE) and accounting for phylogenetic independence. Using a simple model with only latitude of distribution as a predictor variable revealed a significant positive relationship with diet breadth. Previous studies, however, have shown that diet breadth is also correlated with butterfly range size, and in turn, that range size may be correlated with latitude of distribution. Including geographical range size in the model also turned out to have a profound effect on the results – to the extent that the relationship between latitude of distribution and diet breadth was effectively reversed. We conclude that, at least for this group of butterflies, there is no evidence for a positive correlation between latitude of species distribution and diet breadth when controlling for range size, and that the effect may actually even be reversed.
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11.
  • Sniegula, Szymon, et al. (author)
  • Photoperiod affects compensating developmental rate across latitudes in the damselfly Lestes sponsa
  • 2010
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 35:2, s. 149-157
  • Journal article (peer-reviewed)abstract
    • 1. Although there is a great deal of theoretical and empirical data about the life history responses of time constraints in organisms, little is known about the latitude-compensating mechanism that enables northern populations' developmental rates to compensate for latitude. To investigate the importance of photoperiod on development, offspring of the obligatory univoltine damselfly Lestes sponsa from two populations at different latitudes (53°N and 63°N) were raised in a common laboratory environment at both northern and southern photoperiods that corresponded to the sites of collection. 2. Egg development time was shorter under northern photoperiod regimes for both populations. However, the northern latitude population showed a higher phenotypic plasticity response to photoperiod compared with the southern latitude population, suggesting a genetic difference in egg development time in response to photoperiod. 3. Larvae from both latitudes expressed shorter larval development time and faster growth rates under northern photoperiod regimes. There was no difference in phenotypic plastic response between northern and southern latitude populations with regard to development time. 4. Data on field collected adults showed that adult sizes decreased with an increase in latitude. This adult size difference was a genetically fixed trait, as the same size difference between populations was also found when larvae were reared in the laboratory. 5. The results suggest phenotypic plasticity responses in life history traits to photoperiod, but also genetic differences between north and south latitude populations in response to photoperiod, which indicates the presence of a latitudinal compensating mechanism that is triggered by a photoperiod.
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12.
  • Solbreck, Christer, et al. (author)
  • Very long diapause and extreme resistance to population disturbance in a galling insect
  • 2012
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 37, s. 51-55
  • Journal article (peer-reviewed)abstract
    • 1. Some insects have a prolonged diapause – a dormancy that extends over more than 1 year. In most species prolonged diapause involves one or a few extra years, but in extreme cases diapause may surpass 10 years. Few cases of very long diapause have been described, and very little is known about the population consequences of the temporal refuge formed by the diapausing individuals.  2. The gall midgeContarinia vincetoxiciKieffer galls the flowers of a long-lived herbVincetoxicum hirundinariaMed. After completing development, larvae leave the galls for the ground where they enter diapause. Extending an earlier published inoculation experiment, we show that the diapause may last up to at least 13 years, with a median duration of at least 6 years.  3. The gall midge is attacked by two parasitoid species. Dissections of gall midge larvae for presence of parasitoids revealed thatOmphale salicisHaliday had a maximum 2 year diapause andSynopeas acuminatusKieffer a maximum 4 years. The very long diapause of the gall midge may thus provide a temporal refuge from these enemies.  4. In a 15-year field experiment all galls were removed every year from six isolated habitat patches. Density changes in experimental populations were not statistically different from control populations for over a decade. After 14–15 years a modest decline could be observed. This slow response illustrates that prolonged diapause inC. vincetoxiciprovides a very strong population buffer against mortality during the galling stage.
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13.
  • Stenberg, Johan A, et al. (author)
  • Host-plant genotype mediates supply and demand of animal food in an omnivorous insect
  • 2011
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 36, s. 442-449
  • Journal article (peer-reviewed)abstract
    • 1. Omnivorous predators can protect plants from herbivores, but may also consume plant material themselves. Omnivores and their purely herbivorous prey have previously been thought to respond similarly to host-plant quality. However, different responses of omnivores and herbivores to their shared host plants may influence the fitness, trophic identity, and population dynamics of the omnivores. 2. The aim of the present study was to show that an omnivorous heteropteran (Anthocoris nemorum L.) and two strictly herbivorous prey species respond differently to different genotypes of their shared host plant, Salix. Some plant genotypes were sub-optimal for the omnivore, although suitable for the herbivores, and vice versa. 3. The contrasting patterns of plant suitability for the omnivore and the herbivores highlight an interaction between plant genotype and omnivores' access to animal food. Plant genotypes that were sub-optimal for the omnivore when herbivores were experimentally excluded became the best host plants when herbivores were present, as in the latter situation additional prey became available. By contrast, the quality of plant genotypes that were intrinsically suitable for omnivores, did not improve when herbivores were present as these plant genotypes were intrinsically sub-optimal for herbivores, thus providing omnivores with almost no additional animal food. 4. The differential responses of omnivores and their prey to the same host-plant genotypes should allow omnivores to colonise sub-optimal host plants in their capacity as predators, and to colonise more suitable host plants in their capacity as herbivores. It may thus be difficult for Salix to escape herbivory entirely, as it will rarely be unsuitable for both omnivores and pure herbivores at the same time
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14.
  • Victorsson, Jonas (author)
  • Semi-field experiments investigating facilitation : arrival order decides the interrelationship between two saproxylic beetle species
  • 2012
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 37:5, s. 395-401
  • Journal article (peer-reviewed)abstract
    • 1. Acanthocinus aedilis (Linnaeus) and Rhagium inquisitor (Linnaeus) both colonise the cambial layer in newly dead Scots pine Pinus sylvestris L. and thus are potential competitors. 2. Species interactions and in particular priority effects were investigated in an experiment with a replacement series design. Four pairs of adult beetles were released on each of 91 caged pine bolts (0.35 m long, 13 replicates). To test for priority effects, a 2-week interval was used to separate the species. 3. The interrelationship in simultaneous coexistence was positive for A. aedilis and negative for R. inquisitor (+,-). Acanthocinus aedilis produced 161% more offspring per female in coexistence than alone. Rhagium inquisitor had lower offspring quality in coexistence where its larvae weighed 39% less than in one-species bolts. 4. The interrelationship depended on arrival order. When A. aedilis had priority the interaction was again advantageous to A. aedilis (+,-) but when R. inquisitor had priority no species interaction occurred (0,0). Both species therefore fared better when having priority. 5. Facilitation in cerambycids is novel and the facilitative effect on A. aedilis could be oviposition incitement or resource enhancement by R. inquisitor.
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15.
  • Abbott, Jessica (author)
  • Self-medication in insects: current evidence and future perspectives
  • 2014
  • In: Ecological Entomology. - : Wiley. - 1365-2311 .- 0307-6946. ; 39:3, s. 273-280
  • Journal article (peer-reviewed)abstract
    • 1. Self-medication is an ability to consume or otherwise contact biologically active organic compounds specifically for the purpose of helping to clear a (parasitic) infection or reduce its symptoms. Consumption of these compounds may either take place before the infection is contracted (prophylactic consumption) or after the infection is contracted (therapeutic consumption). 2. An important insight is that self-medication is a form of adaptive plasticity, and as such, consumption of the medicinal substance when uninfected must impose a fitness cost (otherwise the substance would be universally consumed). This distinguishes self-medication from several closely related phenomena such as microbiome effects or compensatory diet choice. 3. A number of recent studies have convincingly demonstrated self-medication within several different, distantly-related, insect taxa. Here I review evidence of self-medication in the wooly bear caterpillar Grammia incorrupta Edwards, the armyworm Spodoptera Guenee, the fruit fly Drosophila melanogaster Meigen, the monarch butterfly Danaus plexippus Kluk, and the honey bee Apis mellifera Linnaeus. 4. These studies show not only that self-medication is possible, but that the target of the medication behaviour may in some cases be kin rather than self. They also reveal very few general patterns. I therefore end by discussing future prospects within the field of insect self-medication.
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16.
  • Eilers, Silke, et al. (author)
  • Micro-climate determines oviposition site selection and abundance in the butterfly Pyrgus armoricanus at its northern range margin
  • 2013
  • In: Ecological Entomology. - : Wiley. - 1365-2311 .- 0307-6946. ; 38:2, s. 183-192
  • Journal article (peer-reviewed)abstract
    • 1. Knowledge about species habitat requirements is important when designing conservation strategies as well as for predicting species distributions. For herbivorous insects, insights in oviposition preferences can provide important information on their habitat requirements. 2. The oviposition preferences of Oberthür's Grizzled Skipper butterfly Pyrgus armoricanus Oberthür at its northern range boundary in southern Sweden were studied and it was also tested to what extent oviposition preferences can predict variation in population size among monitored sites. 3. Oviposition behaviour was observed and analysed using a two-step approach. First the characteristics of host plant ramets that female butterflies inspected for oviposition (including both ramets that were rejected and ramets used for oviposition) were compared with with control ramets. Second, ramets on which female butterflies oviposited were compared with ramets that butterflies inspected but rejected. 4. The preferred plant species for oviposition was Filipendula vulgaris Moench. Filipendula vulgaris ramets inspected for oviposition by P. armoricanus females were situated in warm microclimates, primarily on south facing slopes, surrounded by lower vegetation and a higher percentage cover of bare ground compared with random control ramets. 5. Among the inspected ramets, females chose to oviposit those situated in the warmest micro-climates and those surrounded by the largest percentage cover of bare ground. 6. Together with habitat patch area, oviposition preferences explained 65% of the variation in butterfly population size. 7. These results reveal the importance of a microclimate as a component of habitat quality for insect populations at the margins of their geographical range.
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17.
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18.
  • Höglund, Solveig (author)
  • Timing of growth determines fitness and performance of a galling insect on willow
  • 2014
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 39, s. 159-167
  • Journal article (peer-reviewed)abstract
    • Characteristics that determine a plant's quality as herbivore food exhibit within-plant heterogeneity. Most models suggest negative effects from secondary chemicals. Less work has focused on plant growth dynamics that might also be important in creating heterogeneity in the distribution of food resources among leaves within the plant. Gall-forming insects are sessile during their feeding stage and are therefore of particular interest when assessing the relative importance of growth and non-growth processes in plants. Galls act as sinks for photoassimilates, and successful redirection of these resources requires that gall formation takes place in plant modules that are in an active growth phase. The gall midge Dasineura marginemtorquens infests leaves of the fast-growing Salix viminalis. Several young leaves per shoot are used as oviposition sites during any single egg-laying occasion. This study investigates the extent to which growth in leaves that are apparently suitable for gall initiation varies along shoots of S. viminalis, and tests whether or not such variation affects the fitness and performance of D. marginemtorquens. The relative position of the galled leaves along a shoot was found to determine the success of the gall midge in terms of larval survival, larval developmental time, and adult size. Leaf growth dynamics, but not leaf size, was associated with the variation in insect fitness and performance. Thus, when considering habitat quality for a sessile insect like D. marginemtorquens, the length of time that the galling site acts as a photoassimilate sink is more important than the final size of the plant module.
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19.
  • Kollberg, Ida, et al. (author)
  • Multiple effects of temperature, photoperiod and food quality on the performance of a pine sawfly
  • 2013
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 38, s. 201-208
  • Journal article (peer-reviewed)abstract
    • Many entomologists strive to understand what consequences climate change will have on insect performance. Such understanding is important, not least, when trying to predict the future impact of pest insects. In this study, it was reported how the multiple effects of temperature, photoperiod, and food quality affected the survival, development, and the final weight of the European pine sawfly (Neodiprion sertifer Geoffr.), an herbivorous outbreak species in boreal pine (Pinus spp.) forests. Sawfly larvae were reared in two different temperatures (15 and 20 degrees C) and under two different light regimes (20 and 18 h light). The larvae were fed pine needles either low or high in diterpene content. A 5 degrees C higher temperature did not affect the survival of the larvae, but reduced the development time by 3741%. The final weight was reduced by 22% in the warmer temperature, but only in combination with a short day length. A high content of diterpenes in the needles reduced the susceptibility to the virus by 31%, but did not otherwise affect the performance of the larvae. This study shows that the larval development could be shortened in a warmer climate and thereby decreasing the risk of predation. This per se may increase the risk for insect outbreaks, but the interactive effects of warmer temperatures with other abiotic and biotic factors such as day length and food quality (indicated in this study), and potential better performance of natural enemies and pathogens, illustrate the possibility for complex outcomes in a climate change perspective.
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20.
  • Larsson, Stig (author)
  • Solar radiation directly affects larval performance of a forest insect
  • 2013
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 38, s. 553-559
  • Journal article (peer-reviewed)abstract
    • Solar radiation can affect the performance of insect herbivores directly by increasing body temperature, or indirectly through alteration of either host plant quality or natural enemy activity. To test for the direct effect of solar radiation on larval performance, young Pinus sylvestris trees growing on the island of Gotland (Sweden) were assigned to one of four shading treatments for the whole duration of the first larval instar of the northern pine processionary moth Thaumetopoea pinivora. There was a strong, linear relationship between shading and the temperature of the first-instar colonies of T. pinivora, resulting in higher growth of the larvae exposed to full sunlight, but there were no effects on developmental rate or larval mortality. Putative negative effects of UV radiation on the larvae are not consistent with higher growth in full sunlight, but it is possible that UV effects might have modulated the response.Thaumetopoea pinivora has a strong preference for light and open pine stands, i.e. habitats with frequent intense incoming solar radiation. The data in the present study suggest that the opportunity for young larvae to bask in the sun during cold spring weather is an important determinant of the spatial distribution of T. pinivora.
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21.
  • Outomuro, David, et al. (author)
  • Does allometry of a sexually selected ornamental trait vary with sexual selection intensity? : A multi-species test in damselflies
  • 2014
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 39:3, s. 399-403
  • Journal article (peer-reviewed)abstract
    • Ornaments may show hyperallometry in certain taxa, i.e. large individuals have proportionally larger ornaments than small ones. One hypothesis suggests that higher sexual selection intensity leads to steeper hyperallometric patterns. This study tested whether an ornamental trait subject to both intra- and intersexual selection showed steeper allometric slopes than when subject solely to intrasexual selection. The study employed the sexually selected male wing pigmentation of 14 calopterygid species (damselflies) that differ in sexual selection intensity (intrasexual selection versus intra- and intersexual selection). Hyperallometry was not a uniform pattern in the study species. Furthermore, the allometric slopes did not differ between sexual selection intensities. The allometry of ornamental traits is therefore highly variable even among related species. Other selection pressures-probably species-specific and at a local scale-acting on wing pigmentation might explain the diversity of allometric patterns.
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22.
  • Ronnås, Cecilia, et al. (author)
  • Evergreen foliage allows early hatching in a pine processionary moth and escape from predation
  • 2014
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 39, s. 445-452
  • Journal article (peer-reviewed)abstract
    • 1. Seasonal variation in leaf quality and climate conditions often imposesconstraints on the temporal occurrence of tree-feeding insect larvae, but the seasonaleffects of predation have received limited attention. In temperate climate zones, both theabundance and activity of predators can be expected to vary over time.2. The study reported herein examined the impact of temporal variation in predatoractivity levels on the life history of an herbivorous insect feeding on a constant foodsource: previous-year needles of Scots pine (Pinus sylvestrisL.). In field experiments,the survival and growth rates of colonies ofThaumetopoea pinivoraTreitschke larvaethat had been manipulated to hatch at three different dates were compared. Eggs ofT. pinivorausually hatch by mid-April in southern Sweden, which is earlier than mostother herbivorous insects that overwinter as eggs in this region.3. Predator exclusion experiments indicated that larvae which hatched later than Aprilexperienced a higher level of predator activity, mainly by ants. The final larval size andthe timing of pupation were not affected by hatching date. First instar larvae were moreextensively preyed on than second instars.4. The life history of herbivore species can be affected by seasonal variation inpredation pressures. This study suggests that early hatching in a lepidopteran speciescan allow a temporal escape from predation during the vulnerable early life stages.
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23.
  • Sniegula, Szymon, et al. (author)
  • Photoperiod and variation in life history traits in core and peripheral populations in the damselfly Lestes sponsa
  • 2014
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 39:2, s. 137-148
  • Journal article (peer-reviewed)abstract
    • In order to predict evolutionary responses to environmental changes one needs to identify the evolutionary potential in terms of genetic variation of traits and of the traits' plasticity. We studied genetic variance in life history traits and their reaction norms in response to manipulated photoperiods in central, northern, and northernmost peripheral populations of the damselfly Lestes sponsa (Hansemann). After the central-marginal hypothesis, it is predicted that central populations will express the highest genetic variance. Northern and northernmost populations showed the highest development and growth rates. All populations expressed shorter development and accelerated growth when raised in a northern compared with a central latitude photoperiod. The slopes of reaction norms differed between regions resulting in a region-by-photoperiod interaction. There was genetic variation in development time; however, it did not differ across regions. There was no genetic variation in growth rate or in the plasticity of development time and growth rate to photoperiod. Results did not support the central-marginal hypothesis. However, evidence was found that the development time has the potential to evolve at similar rates across study regions. In contrast, the growth rate seems to be genetically constrained for further evolution, probably because of a strong past directional selection on this trait. The presence of low genetic variation in the slope of the reaction norms could be a result of stabilising selection imposed by seasonality.
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24.
  • Tegelaar, Karolina, et al. (author)
  • Alate production in an aphid in relation to ant tending and alarm pheromone
  • 2014
  • In: Ecological Entomology. - : Wiley. - 0307-6946 .- 1365-2311. ; 39:5, s. 664-666
  • Journal article (peer-reviewed)abstract
    • 1. Winged dispersal is vital for aphids as predation pressure and host plant conditions fluctuate. 2. Ant-tended aphids also need to disperse, but this may represent a cost for the ants, resulting in an evolutionary conflict of interest over aphid dispersal. 3. The combined effects of aphid alarm pheromone, indicating predation risk, and ant attendance on the production of winged aphids were examined in an experiment with Aphis fabae (Homoptera: Aphididae) (Scopoli 1763) aphids and Lasius niger (Formicidae: Formicinae) (Linne, 1758) ants. 4. This study is the first to investigate the joint effects of alarm pheromone and ant attendance, and also the first to detect an influence of alarm pheromone on the production of winged morphs in A. fabae. 5. After a period of 2 weeks, it was found that aphid colonies exposed to intermittent doses of alarm pheromone produced more winged individuals, whereas ant tending had the opposite effect. The effects were additive on a log scale, and ant attendance had a greater proportional influence than exposure to alarm pheromone. A tentative conclusion is that ants have gained the upper hand in an evolutionary conflict about aphid dispersal.
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