Climate warming decreases the survival of the little auk (Alle alle), a high Arctic avian predator

Delayed maturity, low fecundity, and high adult survival are traits typical for species with a long‐life expectancy. For such species, even a small change in adult survival can strongly affect the population dynamics and viability. We examined the effects of both regional and local climatic variability on adult survival of the little auk, a long‐lived and numerous Arctic seabird species. We conducted a mark‐resighting study for a period of 8 years (2006‐2013) simultaneously at three little auk breeding sites that are influenced by the West Spitsbergen Current, which is the main carrier of warm, Atlantic water into the Arctic. We found that the survival of adult little auks was negatively correlated with both the North Atlantic Oscillation (NAO) index and local summer sea surface temperature (SST), with a time lag of 2 and 1 year, respectively. The effects of NAO and SST were likely mediated through a change in food quality and/or availability: (1) reproduction, growth, and development of Arctic Calanus copepods, the main prey of little auks, are negatively influenced by a reduction in sea ice, reduced ice algal production, and an earlier but shorter lasting spring bloom, all of which result from an increased NAO; (2) a high sea surface temperature shortens the reproductive period of Arctic Calanus, decreasing the number of eggs produced. A synchronous variation in survival rates at the different colonies indicates that climatic forcing was similar throughout the study area. Our findings suggest that a predicted warmer climate in the Arctic will negatively affect the population dynamics of the little auk, a high Arctic avian predator.     

Protected raspberry production alters aphid–plant interactions but not aphid population size

• 1 Aphid population dynamics in crops are often driven by interactions with their host plants, which can be extensively influenced by environmental change. Protective environments (i.e. plastic tunnels) are now frequently used for soft fruit production, which may affect the localized climate and alter such interactions. This two year study on red raspberry (Rubus idaeus) addressed how protected environments affected two aphid species; the large raspberry aphid Amphorophora idaei (LRA) and the small raspberry aphid Aphis idaei (SRA).
• 2 Temperatures were higher (up to 7–10 °C) in tunnels compared with the field. Plants in tunnels grew approximately 1.4 cm/week faster and had lower (approximately 35%) foliar amino acid concentrations than plants in the field.
• 3 Aphids affected plant growth differently depending on growing environment; they promoted plant growth by 18–37% in tunnels, although they had no such effect in the field. Aphids reduced total and essential amino acid concentrations, with SRA causing greatest reductions (approximately 40% and 33%, respectively).
• 4 Aphid population sizes were similar in both environments, although individual LRA were smaller in tunnels (30% smaller in 2007) compared with those in the field. We suggest that faster aphid development rates inside warmer tunnels were not realized as a result of the variable effects of the growing environment on amino acid composition.
• 5 We conclude that the increasing use of protected environments in crop production will not necessarily cause predictable increases in aphid populations, although it may alter aphid–plant interactions in terms of aphid‐induced changes to plant growth.

     

Life-cycle and morph production in the Arctic aphid Acyrthosiphon brevicorne

 The life-cycle of the sub-Arctic, Dryas-feeding aphid, Acyrthosiphon brevicorne, is described and shown to be intermediate between that of the high-Arctic aphid (Acyrthosiphon svalbardicum) and typical holocyclic, monoecious, temperate species. The fundatrix of A. brevicorne can give rise directly to both sexual morphs, a necessary adaptation to the short Arctic summer. Production of males is predetermined; some males are produced by all-viviparous mothers, but at lower frequencies in the birth sequences of the fundatrix than in subsequent generations. By contrast, the production of oviparae is controlled, at least in part, by photoperiod. Received: 19 April 1994/Accepted: 4 August 1995     

Field manipulation of populations of individual staphylinid species in cereals and their impact on aphid populations

Abstract.

• 1 Four species of staphylinids were caged separately on wheat and their effect on the population development of the grain aphid, Sitobion avenae (F.), was investigated over two seasons.
• 2 A novel field cage design was used to exclude all but the staphylinid species under investigation.
• 3 Predator effects were compared with total-exclusion cages in which all predators and parasitoids were kept out.
• 4 During a high-density phase of aphid population development only Philonthus cognutus (Stephens) significantly influenced aphid population numbers.
• 5 At low aphid densities, Tachyporus obtusus (L.), T.chrysomelinus (L.) and P.cognatus reduced aphid population levels.
• 6 The experiments showed that Tachyporus spp. can reduce the numbers of cereal aphids prior to the exponential phase of aphid population increase and that P.cognatus causes some reduction at both the stages of aphid population growth investigated.

     

Effects of temperature elevation on a field population of Acyrthosiphon svalbardicum (Hemiptera: Aphididae) on Spitsbergen

A manipulation experiment was carried out on a field population of the aphid Acyrthosiphon svalbardicum near Ny Ålesund, on the high arctic island of Spitsbergen, using cloches to raise temperature. An average rise in temperature of 2.8 deg. C over the summer season markedly advanced the phenology of both the host plant Dryas octopetala and the aphid. Advanced aphid phenology, with concomitant increases in reproductive output and survival, and successful completion of the life-cycle led to an eleven-fold increase in the number of overwintering eggs. Thermal budget requirements in day degrees above 0°C were calculated for key life-cycle stages of the aphid. Temperature data from Ny Ålesund over the past 23 years were used to calculate thermal budgets for the field site over the same period and these were compared with the requirements of the aphid. Each estimated thermal budget was then adjusted to simulate the effect of a +2, +4, and –2deg. C change in average temperature on aphid performance. This retrospective analysis (i) confirms that the life-cycle of A. svalbardicum is well suited to exploit higher summer temperatures, (ii) indicates that the annual success of local populations are sensitive to small changes in temperature and (iii) suggests that the aphid is living at the limits of its thermal range at Ny Ålesund based on its summer thermal budget requirements.     

Picoeukaryote Plankton Composition off West Spitsbergen at the Entrance to the Arctic Ocean

Investigation of marine eukaryotic picoplankton composition is limited by missing morphological features for appropriate identification. Consequently, molecular methods are required. In this study, we used 454‐pyrosequencing to study picoplankton communities at four stations in the West Spitsbergen Current (WSC; Fram Strait). High abundances of Micromonas pusilla were detected in the station situated closest to Spitsbergen, as seen in surveys of picoplankton assemblages in the Beaufort Sea. At the other three stations, other phylotypes, affiliating with Phaeocystis pouchetii and Syndiniales in the phylogenetic tree, were present in high numbers, dominating most of them. The picoplankton community structures at three of the stations, all with similar salinity and temperature, were alike. At the fourth station, the influence of the East Spitsbergen Current, transporting cold water from the Barents Sea around Spitsbergen, causes different abiotic parameters that result in a significantly different picoeukaryote community composition, which is dominated by M. pusilla. This observation is particularly interesting with regard to ongoing environmental changes in the Arctic. Ongoing warming of the WSC could convey a new picoplankton assemblage into the Arctic Ocean, which may come to affect the dominance of M. pusilla.     

The population dynamics of the stinging nettle aphid, Microlophium carnosum (Bukt.)

• 1 Populations of Microlophium carnosum on patches of perennial stinging nettle, Urtica dioica increased rapidly during April and May to reach their peaks in June. The decline in numbers was equally rapid and very small populations persisted into autumn; parthenogenetic over-wintering was recorded.
• 2 Suboptimal ambient temperature and mortality due to natural enemies contributed mainly to the post-peak development of aphid populations.
• 3 The combined effects of intraspecific competition and a deterioration in the food quality of the host plant appeared to be the major factors determining the temporal pattern of aphid abundance.
• 4 Variation in the size of populations between the three sampled sites was correlated with differences in the food quality of nettles as indicated by aphid mean relative growth rate.
• 5 Each nettle patch has a particular ‘carrying capacity’ for aphids, within which a biennial fluctuation between relatively large and small aphid populations appeared to be emerging at most of the sites investigated. A natural or aphid-induced cycle in host plant quality, or alternatively, the persistent effects of intraspecific competition over several generations, may explain this fluctuation.

     

The biology and feeding ecology of Arctic charr in the Kerguelen Islands

Subsequent to their introduction in the 1950s, Arctic charr Salvelinus alpinus have been able to establish a self-sustaining population that has adapted to the unique conditions of the sub-Antarctic Kerguelen Islands. Here, 48 individuals (198–415 mm) were caught with gillnets and their basic biology and feeding ecology were examined using stable isotope analysis. The Lac des Fougères population split use of littoral and pelagic resources evenly, although larger fish relied more heavily on littoral production and appear to follow the size-dependent life history habitat template seen in many Scandinavian lakes where smaller sized individuals occupy the pelagic zone and larger individuals dominate the littoral habitat. In Kerguelen, Arctic charr mature at the same ages (5.6 years) as Arctic charr in both sub-Arctic and Arctic lakes. Although mortality was average in comparison to comparator sub-Arctic lakes, it was high in comparison to Arctic lakes. Maximal age (>7+) was at the lower end of the range typically seen in sub-Arctic lakes. Although they inhabit a resource-poor environment, Kerguelen Arctic charr showed no evidence of cannibalism. Thus, while Arctic charr can survive and reproduce in the relatively unproductive Kerguelen lake environments, survival and growth nevertheless appear to be traded off against survival and longevity. The uniqueness of the population location and the recency of its introduction suggest that further monitoring of the population has the potential to yield valuable insights into both the adaptability of the species and its likely responses to ongoing large-scale environmental change as represented by climate change.     

Climate change in the Arctic: Testing the poleward expansion of ticks and tick-borne diseases

Climate change is most strongly felt in the polar regions of the world, with significant impacts on the species that live there. The arrival of parasites and pathogens from more temperate areas may become a significant problem for these populations, but current observations of parasite presence often lack a historical reference of prior absence. Observations in the high Arctic of the seabird tick Ixodes uriae suggested that this species expanded poleward in the last two decades in relation to climate change. As this tick can have a direct impact on the breeding success of its seabird hosts and vectors several pathogens, including Lyme disease spirochaetes, understanding its invasion dynamics is essential for predicting its impact on polar seabird populations. Here, we use population genetic data and host serology to test the hypothesis that I. uriae recently expanded into Svalbard. Both black-legged kittiwakes (Rissa tridactyla) and thick-billed murres (Uria lomvia) were sampled for ticks and blood in Kongsfjorden, Spitsbergen. Ticks were genotyped using microsatellite markers and population genetic analyses were performed using data from 14 reference populations from across the tick's northern distribution. In contrast to predictions, the Spitsbergen population showed high genetic diversity and significant differentiation from reference populations, suggesting long-term isolation. Host serology also demonstrated a high exposure rate to Lyme disease spirochaetes (Bbsl). Targeted PCR and sequencing confirmed the presence of Borrelia garinii in a Spitsbergen tick, demonstrating the presence of Lyme disease bacteria in the high Arctic for the first time. Taken together, results contradict the notion that I. uriae has recently expanded into the high Arctic. Rather, this tick has likely been present for some time, maintaining relatively high population sizes and an endemic transmission cycle of Bbsl. Close future observations of population infestation/infection rates will now be necessary to relate epidemiological changes to ongoing climate modifications.     

Molecular diversity and derivations of populations of Silene acaulis and Saxifraga oppositifolia from the high Arctic and more southerly latitudes

A survey of allozyme diversity within and between populations of Silene acaulis from Spitsbergen, Norway, Iceland and Scotland, showed that populations from the high Arctic (Spitsbergen, > 76°N) contained high levels of diversity and were genetically similar to populations from more southern locations. Indirect measures of gene flow (Nm), calculated from Wrigh's F indicated that there had been extensive gene flow between Spitsbergen and some Norwegian populations. A restriction site analysis of chloroplast DNA (cpDNA) in S. acaulis revealed that all populations contained a single identical cpDNA haplotype, except one population from Norway which also contained a second haplotype. In contrast, five different cpDNA haplotypes were distinguished in a more limited survey of cpDNA variation in Saxifraga oppositifolia, with all five haplotypes present in one of two Spitsbergen populations surveyed. The contrasting cpDNA results for the two species suggest that whereas high-Arctic populations of Silene acaulis have most likely been derived from immigrants which arrived from the south after the last glacial period, high-Arctic populations of Saxifraga oppositifolia may be derived, in part, from ancient northern stocks which survived the last glaciation in high-Arctic refugia.     

Two‐year oscillation cycle in abundance of soybean aphid in Indiana

• 1 The present study evaluated the population dynamics of the heteroecious soybean aphid Aphis glycines Matsumura (Hemiptera: Aphididae) during an 8‐year period in Indiana, shortly after its detection in North America. Sampling conducted at multiple locations revealed that A. glycines exhibited a 2‐year oscillation cycle that repeated itself four times between 2001 and 2008: years of low aphid abundance were consistently followed by years of high aphid abundance.
• 2 Similar patterns of abundance of A. glycines and coccinellids (Coleoptera: Coccinellidae) in soybean fields, both within and between‐years, suggest that late season predation by coccinellids plays a role in the oscillatory cycle of aphids. Insidious flower bugs Orius insidiosus (Say) (Hemiptera: Anthocoridae) were numerically more abundant than coccinellids, although the lack of synchrony between aphids and predatory bugs suggests that O. insidiosus has a limited influence on between‐year variations in aphid density.
• 3 The inverse relationship between aphid densities before and after the start of the autumn migratory period changes direction in alternate years. High aphid density on soybean in the summer is associated with a reduced number of alate migrants produced in the autumn. Conversely, years with low density aphids on soybean in the summer are characterized by high numbers of alates that migrate to the primary host in the autumn.
• 4 From a pest management perspective, the 2‐year oscillation cycle of A. glycines is a desirable attribute with respect to population dynamics because it implies that aphids cause significant economic damage only in alternate years (as opposed to every year). Cultural practices enhancing the conservation biological control of Coccinellidae may help to preserve the periodicity of aphid infestation and restrict the pest status of A. glycines.

     

A population dynamics perspective on effect of irrigation regimes and plant densities on greenbug abundance in grain sorghum using regression

• 1 A dataset generated from previous experiments on greenbug Schizaphis graminum (Rondani) (Hemiptera: Aphididae) response to irrigation and plant density in grain sorghum was reanalyzed using a recently‐developed mechanistic ecological model for describing aphid population density curves. The model was used to estimate seven response variables: observed peak aphid abundance, predicted peak aphid abundance, time of peak abundance, per capita birthrate, death rate coefficient, final cumulative density and duration of substantial aphid infestation across three irrigation regimes and five plant densities.
• 2 Using regression, the observed peak aphid abundance, predicted peak aphid abundance, per capita birthrate and final cumulative abundance were shown to decrease significantly, whereas the death rate coefficient and duration of the infestation were shown to increase significantly for each 100 000 plant/ha increase.
• 3 Although significant results were found for a number of variables generated from the specific data set used in the analyses, of perhaps greater importance is the potential use of these equations in future predictions of aphid population dynamics. An example of projecting population curves based on estimated peak and cumulative counts and an example of projecting population curves based on estimated birth and death rate coefficients are provided.

     

Pine pest aphids of the genus Eulachnus (Hemiptera: Aphididae: Lachninae): how far can their range extend?

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Population growth of Rhopalosiphum padi under different thermal regimes: an agent-based model approach

1. Rhopalosiphum padi (Linnaeus, 1758) is abundant and has a broad geographic distribution. It is one of the most important cereal pests. In Brazil, the economic losses associated with this aphid result mainly from the transmission of the barley yellow dwarf viruses.
2. Decision-making for the adoption of management measures must consider the initial population size, the potential for population increase, and the time when this population will reach levels at which the resulting damage is equal to the costs of control measures. Consequently, the establishment of management programmes and decision support systems should be based on models that estimate the potential population growth of this pest species.
3. Temperature is one of the main factors that determine the growth rate of insect populations. Generally, controlled experiments are designed to examine the relationship of temperature at fixed intervals in relation to the development phases of insects. In nature, thermal regimes are not constant, and population growth is the result of a series of combined events.
4. In this work, the effects of different thermal regimes on the population growth of R. padi were compared.
5. An agent-based model was used to estimate population growth, and the parameters defined in controlled regimes were compared with fluctuating temperatures under natural conditions.
6. The temperature-driven model presented here can serve as a tool to predict population growth and decision-making for aphid management.
7. The model structure and the proposed experimental design allow the addition of modules and layers of factors that can progressively affect the populations of aphids to gradually improve the model.

     

Long‐term persistence,density dependence and effects of climate change on rosyside dace (Cyprinidae)

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Methane emission from Arctic tundra

Concerns about a possible feedback effect on global warming following possible increased emissions of methane from tundra environments have lead to series of methane flux studies of northern wetland/tundra environments. Most of these studies have been carried out in boreal sub-Arctic regions using different techniques and means of assessing representativeness of the tundra. Here are reported a time series of CH₄ flux measurements from a true Arctic tundra site. A total of 528 independent observations were made at 22 fixed sites during the summers of 1991 and 1992. The data are fully comparable to the most extensive dataset yet produced on methane emissions from sub-Arctic tundra-like environments. Based on the data presented, from a thaw-season with approximately 55% of normal precipitation, a global tundra CH₄ source of 18–30 Tg CH₄ yr⁻¹ is estimated. This is within the range of 42±26 Tg CH₄ yr⁻¹ found in a similar sub-Arctic tundra environment. No single-parameter relationship between one environmental factor and CH₄ flux covering all sites was found. This is also in line with conclusions drawn in the sub-Arctic. However, inter-season variations in CH₄ flux at dry sites were largely controlled by the position of the water table, while flux from wetter sites seemed mainly to be controlled by soil temperature.     

Defence variation within a guild of aphid-tending ants explains aphid population growth

• Mutualism studies often focus on the service provided by single species, while variation in benefits provided by multiple partners is less understood. Ant-aphid food-for-protection mutualisms are suitable to study the implications of intra-guild service variation because they often involve several ant species with varying levels of aggressiveness.
• We studied an aphid species and its associated ant guild to address whether intra-guild defence variation against aphid natural enemies explains aphid performance on plants (thistles). We surveyed plants with natural abundances of aphids associated with different ant species and estimated aphid population growth. We conducted confrontation experiments between ant species and aphid natural enemies (ladybugs and hoverfly larvae). In plants patrolled by the most aggressive ant species, we determined the ant's probability of expelling aphid natural enemies and tested whether ant exclusion affects the abundance of aphids and their natural enemies.
• The ant Dorymyrmex tener was the most abundant and frequent species on plants and the most aggressive against aphid natural enemies. Aphid populations grew faster on plants patrolled by D. tener compared to plants patrolled by Camponotus distinguendus or D. richteri. Field experiments confirmed that D. tener effectively expels aphid natural enemies from plants. When D. tener was excluded, the density of aphids decreased, while the abundance of aphid natural enemies increased.
• The disruption of aphid predation by aggressive and numerically dominant ant species is a determinant of aphid population dynamics. This study illustrates the importance of considering intra-guild service variation to better understand multi-partner mutualisms.

     

Intraspecific variation in host plant quality: the aphid Cinara cupressi on the Mexican cypress, Cupressus lusitanica

Abstract.

• 1 In Kenya, the aphid Cinara cupressi (Buckton) has an aggregated distribution across individuals of its host plant, the Mexican cypress, Cupressus lusitanica (Mill).
• 2 There are significant differences in host plant quality: C.cupressi nymphs transplanted onto cypress trees with low aphid infestations are significantly less likely to establish than aphids transplanted onto trees with high aphid infestations.
• 3 Given that some transplanted nymphs establish, the previous level of infestation does not influence aphid survival.
• 4 Evidence for local adaptation to individual plants was not found: nymphs transplanted to the trees from which their parents were collected neither established more readily nor showed lower mortality than those transplanted to other trees with similar levels of infestation. Therefore the variation in host plant quality has not led to the development of local adaptation to particular host plants.

     

Plant water stress intensity mediates aphid host choice and feeding behaviour

1. The effects of drought-induced changes in plant quality on aphid performance and population growth is well-studied. The response of aphid behaviour to plant water limitation has received less attention. Water limitation may affect host-plant colonization by altering the attractiveness of plants. Additionally, plant water limitation may inhibit feeding site establishment and phloem ingestion.
2. Our goal was to examine bird cherry-oat aphid (Rhopalosiphum padi L.) host selection and feeding behaviour under water limitation. We assessed aphid response to well-watered, mildly-stressed, and highly-stressed wheat (Triticum aestivum L.) by evaluating (i) host-plant selection through two-choice assays, (ii) feeding behaviour using the electrical penetration graph technique, and (iii) phloem ingestion by quantifying honeydew production.
3. Aphids were less likely to select highly stressed plants than a mildly stressed or well-watered alternative. Aphids did not distinguish between mildly stressed and well-watered plants. Aphid feeding behaviours, including duration of phloem ingestion, were not affected by water availability. However, honeydew production was reduced under both levels of water limitation. These results suggest that the volume of phloem ingested by aphids per unit time declined on stressed plants. The combination of lower colonization and diminished access to food on stressed plants may lead to a reduction in aphid abundance, independent of the direct effects of nutrition on individual aphid performance.
4. This study highlights the potential contribution of herbivore behaviour to documented changes in aphid abundance on stressed plants and underscores the important role of plant water stress intensity in mediating plant-herbivore interactions.

     

Aphids decelerate litter nitrogen mineralisation through changes in litter quality

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