The response of two butterfly species to climatic variation at the edge of their range and the implications for poleward range shifts

To predict changes in species' distributions due to climate change we must understand populations at the poleward edge of species' ranges. Ecologists generally expect range shifts under climate change caused by the expansion of edge populations as peripheral conditions increasingly resemble the range core. We tested whether peripheral populations of two contrasting butterflies, a small-bodied specialist (Erynnis propertius) and a large-bodied generalist (Papilio zelicaon), respond favorably to warmer conditions. Performance of populations related to climate was evaluated in seven peripheral populations spanning 1.2 degrees latitude (160 km) using: (1) population density surveys, an indirect measure of site suitability; and (2) organismal fitness in translocation experiments. There was evidence that population density increased with temperature for P. zelicaon whose population density declined with latitude in 1 of 3 sample years. On the other hand, E. propertius showed a positive relationship of population density with latitude, apparently unrelated to climate or measured habitat variables. Translocation experiments showed increased larval production at increased temperatures for both species, and in P. zelicaon, larval production also increased under drier conditions. These findings suggest that both species may increase at their range edge with warming but the preference for core-like conditions may be stronger in P. zelicaon. Further, populations of E. propertius at the range boundary may be large enough to act as sources of colonists for range expansions, but range expansion in this species may be prevented by a lack of available host plants further north. In total, the species appear to respond differently to climate and other factors that vary latitudinally, factors that will likely affect poleward expansion.     

CO2浓度和温度升高对红桦根际微生物的影响

应用自控、封闭、独立的生长室系统,研究升高的大气CO2浓度(环境CO2浓度 350(±25)μmol.mol-1,EC)和温度(环境温度 2.0(±0.5)℃,ET)及其交互作用(ECT)对不同栽植密度条件下红桦根际土壤可培养微生物数量的影响。结果表明:(1)EC显著增加了高密度条件下根际细菌数量;在整个生长季中,最大的根际细菌数量增加出现在7月份;而EC对低密度处理的根际细菌数量影响不显著。除了5月和6月份,ET在其余月份均显著增加了根际细菌数量,但是与密度处理没有有意义的相关;ECT对高低密度处理的根际细菌数量均未产生有统计意义的影响。(2)EC对低密度条件下的根际放线菌数量有显著增加,而对高密度条件下的根际放线菌数量无显著影响;ET和ECT对高低密度条件下的根际放线菌数量均未产生有统计意义的影响。(3)EC和ET对高低密度条件下的根际真菌数量无显著增加,而ECT显著增加了根际真菌数量。     

The effects of CO2 on sestonic stoichiometry and community structure of crustacean zooplankton in a eutrophic lake: Increased competitive ability of Bosmina

To explore the effects of CO₂ concentration on the sestonic stoichiometric values and the community structure of crustacean zooplankton in a eutrophic lake, in situ microcosm experiments were conducted at the Lake Taihu Ecosystem Station in spring and summer of 2012. The experimental treatments were three concentrations of CO₂, 270, 380 and 750 ppm, which represented preindustrial and present levels and the level predicted for the end of this century, respectively. The elevated atmospheric CO₂ concentration increased the sestonic C:P ratio, particularly in the spring when the C:P ratio was two-fold greater at the high level of CO₂ than at the low level of CO₂. As a result, the contribution of Bosmina to total crustacean zooplankton abundance increased, most likely because of the low phosphorus content and high adaptability to foods with large elemental ratio variation. The other dominant crustacean zooplankton genera, including Daphnia, Ceriodaphnia, Diaphanosoma and Sinocalanus, had no response to the change in pCO₂ during the microcosm experiments. The shift in crustacean zooplankton community structure between two seasons was primarily due to the transition of the phytoplankton community.     

Evidence for divergence of response in Indica,Japonica, and wild rice to high CO2 × temperature interaction

High CO₂ and high temperature have an antagonistic interaction effect on rice yield potential and present a unique challenge to adapting rice to projected future climates. Understanding how the differences in response to these two abiotic variables are partitioned across rice germplasm accessions may be key to identifying potentially useful sources of resilient alleles for adapting rice to climate change. In this study, we evaluated eleven globally diverse rice accessions under controlled conditions at two carbon dioxide concentrations (400 and 600 ppm) and four temperature environments (29 °C day/21 °C night; 29 °C day/21 °C night with additional heat stress at anthesis; 34 °C day/26 °C night; and 34 °C day/26 °C night with additional heat stress at anthesis) for a suite of traits including five yield components, five growth characteristics, one phenological trait, and four photosynthesis‐related measurements. Multivariate analyses of mean trait data from these eight treatments divide our rice panel into two primary groups consistent with the genetic classification of INDICA/INDICA‐like and JAPONICA populations. Overall, we find that the productivity of plants grown under elevated [CO₂] was more sensitive (negative response) to high temperature stress compared with that of plants grown under ambient [CO₂] across this diversity panel. We report differential response to CO₂ × temperature interaction for INDICA/INDICA‐like and JAPONICA rice accessions and find preliminary evidence for the beneficial introduction of exotic alleles into cultivated rice genomic background. Overall, these results support the idea of using wild or currently unadapted gene pools in rice to enhance breeding efforts to secure future climate change adaptation.     

Transgenerational effects of global environmental change: long-term CO2 and nitrogen treatments influence offspring growth response to elevated CO2

Global environmental changes can have immediate impacts on plant growth, physiology, and phenology. Long-term effects that are only observable after one or more generations are also likely to occur. These transgenerational effects can result either from maternal environmental effects or from evolutionary responses to novel selection pressures and are important because they may alter the ultimate ecological impact of the environmental change. Here, we show that transgenerational effects of atmospheric carbon dioxide (CO₂) and soil nitrogen (N) treatments influence the magnitude of plant growth responses to elevated CO₂ (eCO₂). We collected seeds from Lupinus perennis, Poa pratensis, and Schizachyrium scoparium populations that had experienced five growing seasons of ambient CO₂ (aCO₂) or eCO₂ treatments and ambient or increased N deposition and planted these seeds into aCO₂ or eCO₂ environments. We found that the offspring eCO₂ treatments stimulated immediate increases in L. perennis and P. pratensis growth and that the maternal CO₂ environment influenced the magnitude of this growth response for L. perennis: biomass responses of offspring from the eCO₂ maternal treatments were only 54% that of the offspring from the aCO₂ maternal treatments. Similar trends were observed for P. pratensis and S. scoparium. We detected some evidence that long-term N treatments also altered growth responses to eCO₂; offspring reared from seed from maternal N-addition treatments tended to show greater positive growth responses to eCO₂ than offspring from ambient N maternal treatments. However, the effects of long-term N treatments on offspring survival showed the opposite pattern. Combined, our results suggest that transgenerational effects of eCO₂ and N-addition may influence the growth stimulation effects of eCO₂, potentially altering the long-term impacts of eCO₂ on plant populations.     

西伯利亚蝗气门结构及呼吸代谢对高温胁迫的响应

【目的】掌握西伯利亚蝗Gomphocerus sibiricus的气门结构和呼吸代谢应对高温胁迫的响应策略。【方法】运用扫描电镜观察西伯利亚蝗气门超显微结构,多通道昆虫呼吸仪测定18~42℃处理下西伯利亚蝗的O_2吸收率、CO_2释放率、代谢率和呼吸商。【结果】西伯利亚蝗共有10对气门,胸部2对,腹部8对,呈圆形或椭圆形,内侧着生有筛板,呈刺凸状,分布密集。18~42℃范围内,随温度升高,西伯利亚蝗呼吸代谢呈先上升后下降的趋势。18℃时西伯利亚蝗雌雄成虫的O_2吸收率、CO_2释放率和代谢率值显著小于其他温度下的相应值(P<0.05),雌虫分别为0.0022 m L/min、0.0019 m L/min和0.0210 m L/(g·min),雄虫分别为0.0016 m L/min、0.0016 m L/min和0.0236 m L/(g·min);21~27℃范围内,西伯利亚蝗雌雄成虫的呼吸代谢变化平稳,超过30℃呼吸代谢各指标值迅速上升,至36℃时雌雄成虫的O_2吸收率和代谢率值均显著大于其他温度下的相应值(P<0.05);雌虫分别为0.0071 m L/min和0.0592 m L/(g·min),雄虫分别为0.0089 m L/min和0.1108 m L/(g·min),39℃时CO_2释放率显著大于其他温度下的相应值(P<0.05),雌雄成虫分别为0.0074 m L/min和0.0067 m L/min。【结论】依据西伯利亚蝗呼吸代谢随温度变化特征可以判断,随气候持续变暖,西伯利亚蝗仍将是新疆高山、亚高山草原的重要致灾类群。     

Elevated [CO2] and increased N supply reduce leaf disease and related photosynthetic impacts on Solidago rigida

To evaluate whether leaf spot disease and related effects on photosynthesis are influenced by increased nitrogen (N) input and elevated atmospheric CO₂ concentration ([CO₂]), we examined disease incidence and photosynthetic rate of Solidago rigida grown in monoculture under ambient or elevated (560 μmol mol⁻¹) [CO₂] and ambient or elevated (+4 g N m⁻² year⁻¹) N conditions in a field experiment in Minnesota, USA. Disease incidence was lower in plots with either elevated [CO₂] or enriched N (−57 and −37%, respectively) than in plots with ambient conditions. Elevated [CO₂] had no significant effect on total plant biomass, or on photosynthetic rate, but reduced tissue%N by 13%. In contrast, N fertilization increased both biomass and total plant N by 70%, and as a consequence tissue%N was unaffected and photosynthetic rate was lower on N fertilized plants than on unfertilized plants. Regardless of treatment, photosynthetic rate was reduced on leaves with disease symptoms. On average across all treatments, asymptomatic leaf tissue on diseased leaves had 53% lower photosynthetic rate than non-diseased leaves, indicating that the negative effect from the disease extended beyond the visual lesion area. Our results show that, in this instance, indirect effects from elevated [CO₂], i.e., lower disease incidence, had a stronger effect on realized photosynthetic rate than the direct effect of higher [CO₂].     

Effects of CO2-mediated changes in paper birch and white pine chemistry on gypsy moth performance

We examined the effects of CO₂-mediated changes in the foliar chemistry of paper birch (Betula papyrifera) and white pine (Pinus strobus) on performance of the gypsy moth (Lymantria dispar). Trees were grown under ambient or enriched CO₂ conditions, and foliage was subjected to plant chemical assays and insect bioassays. Enriched CO₂ atmospheres reduced foliar nitrogen levels and increased condensed tannin levels in birch but not in pine. Foliar carbohydrate concentrations were not markedly altered by CO₂ environment. Gypsy moth performance was significantly affected by CO₂ level, species, and the CO₂ x species interaction. Under elevated CO₂ conditions, growth was reduced for larvae fed birch, while development was prolonged for larvae fed pine. Although gypsy moths performed better overall on birch than pine, birch-fed larvae were influenced more by CO₂-mediated changes in host quality.     

Orientation response of haematophagous bugs to CO2: the effect of the temporal structure of the stimulus

Carbon dioxide is generally recognized as an important cue used by haematophagous insects to locate a food source. When the mammalian hosts of these insects breathe, they normally emanate considerable amounts of CO₂ at discrete intervals, i.e. with each exhalation. In this work, we analysed the effect of temporally pulsing CO₂ on the host-seeking behaviour of Triatoma infestans. We investigated the ability of T. infestans to follow continuous and intermittent air pulses of 0.25, 0.5 and 1 Hz that included different concentrations of CO₂. We found that insects were attracted to pulsed airstreams of 0.25 and 0.5 Hz transporting 400 ppm of CO₂ above the ambient levels and to continuous streams added with the same amount of CO₂. On the other hand, insects walked away from streams pulsed at rates of 1 Hz regardless of the amount of CO₂ they bear. The walking trajectories displayed by bugs to attractive CO₂-pulsed streams were as rectilinear and accurate as those to CO₂-continuous streams. Our results are discussed in the frame of the interaction between olfactory and mechanoreceptive inputs as affecting the behavioural response of bugs.     

Temperature extremes: geographic patterns,recent changes,and implications for organismal vulnerabilities

Extreme temperatures can injure or kill organisms and can drive evolutionary patterns. Many indices of extremes have been proposed, but few attempts have been made to establish geographic patterns of extremes and to evaluate whether they align with geographic patterns in biological vulnerability and diversity. To examine these issues, we adopt the CLIMDEX indices of thermal extremes. We compute scores for each index on a geographic grid during a baseline period (1961–1990) and separately for the recent period (1991–2010). Heat extremes (temperatures above the 90th percentile during the baseline period) have become substantially more common during the recent period, particularly in the tropics. Importantly, the various indices show weak geographic concordance, implying that organisms in different regions will face different forms of thermal stress. The magnitude of recent shifts in indices is largely uncorrelated with baseline scores in those indices, suggesting that organisms are likely to face novel thermal stresses. Organismal tolerances correlate roughly with absolute metrics (mainly for cold), but poorly with metrics defined relative to local conditions. Regions with high extreme scores do not correlate closely with regions with high species diversity, human population density, or agricultural production. Even though frequency and intensity of extreme temperature events have – and are likely to have – major impacts on organisms, the impacts are likely to be geographically and taxonomically idiosyncratic and difficult to predict.     

The type of competition modulates the ecophysiological response of grassland species to elevated CO2 and drought

The effects of elevated CO₂ and drought on ecophysiological parameters in grassland species have been examined, but few studies have investigated the effect of competition on those parameters under climate change conditions. The objective of this study was to determine the effect of elevated CO₂ and drought on the response of plant water relations, gas exchange, chlorophyll a fluorescence and aboveground biomass in four grassland species, as well as to assess whether the type of competition modulates that response. Elevated CO₂ in well‐watered conditions increased aboveground biomass by augmenting CO₂ assimilation. Drought reduced biomass by reducing CO₂ assimilation rate via stomatal limitation and, when drought was more severe, also non‐stomatal limitation. When plants were grown under the combined conditions of elevated CO₂ and drought, drought limitation observed under ambient CO₂ was reduced, permitting higher CO₂ assimilation and consequently reducing the observed decrease in aboveground biomass. The response to climate change was species‐specific and dependent on the type of competition. Thus, the response to elevated CO₂ in well‐watered grasses was higher in monoculture than in mixture, while it was higher in mixture compared to monoculture for forbs. On the other hand, forbs were more affected than grasses by drought in monoculture, while in mixture the negative effect of drought was higher in grasses than in forbs, due to a lower capacity to acquire water and mineral nutrients. These differences in species‐level growth responses to CO₂ and drought may lead to changes in the composition and biodiversity of the grassland plant community in future climate conditions.     

Anthocyanin, antioxidant activity and stress-induced gene expression in high CO2-treated table grapes stored at low temperature

A pretreatment with 20kPa CO2+20 kPa O2+60 kPa N2 for 3 days proved effective in maintaining the fruit quality and controlling decay in table grapes (Vitis vinifera cv. Cardinal) stored at 0 degrees C. In the present work, we analyzed whether total anthocyanin content, the molecular mechanism implicated in their biosynthesis and antioxidant activity is related to the beneficial effect of this gaseous treatment. We isolated partial cDNAs that codified for enzymes implicated in the anthocyanin biosynthesis such as l-phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS), and an antioxidant enzyme such as ascorbate peroxidase (APX). Low temperatures induced an accumulation of total anthocyanin content in the skin of both treated and non-treated grapes, although levels were lower in CO2-treated fruit. By contrast, antioxidant activity decreased during storage at 0 degrees C in non-treated grapes but did not change in CO2-treated grapes. The up-regulation of anthocyanin biosynthesis gene expression and VcAPX mRNA observed in non-treated grape is not enhanced in CO2-treated grapes, which presented low total decay. These results point out the ability of CO2-treated grapes to prevent the generation of reactive oxygen species rather than their inactivation by means of induction of studied defense systems.     

Allele frequency shifts in response to climate change and physiological consequences of allozyme variation in a montane insect

Rapid changes in climate may impose strong selective pressures on organisms. Evolutionary responses to climate change have been observed in natural populations, yet no example has been documented for a metabolic enzyme locus. Furthermore, few studies have linked physiological responses to stress with allozyme genotypic variation. We quantified changes in allele frequency between 1988 and 1996 at three allozyme loci (isocitrate dehydrogenase, Idh; phosphoglucose isomerase, Pgi; and phosphoglucomutase, Pgm) for the leaf beetle Chrysomela aeneicollis in the Bishop Creek region of the Sierra Nevada of California (2900-3300 m). Beetles often experience high daytime (> 32 degrees C) and extremely low nighttime (< -5 degrees C) temperatures during summer. Bishop Creek weather station data indicated that conditions were unusually dry before 1988, and that conditions were cool and wet during the years preceding the 1996 collection. We found directional changes in allele frequency at Pgi (11% increase in the Pgi-1 allele), but not at Idh or Pgm. We also found that physiological response to thermal extremes depended on Pgi genotype. Pgi 1-1 individuals induced expression of a 70-kD heat shock protein (HSP) at lower temperatures than 1-4 or 4-4 individuals, and 1-1 individuals expressed higher levels of HSP70 after laboratory exposure to temperatures routinely experienced in nature. Survival after nighttime laboratory exposure to subzero temperatures depended on gender, previous exposure to cold, and Pgi genotype. Females expressed higher levels of HSP70 than males after exposure to heat, and recovery by female Pgi 1-1 homozygotes after exposure to cold (-5 degrees C) was significantly better than 1-4 or 4-4 genotypes. These data suggest that the cooler climate of the mid-1990s may have caused an increase in frequency of the Pgi-1 allele, due to a more robust physiological response to cold by Pgi 1-1 and 1-4 genotypes.     

Inoculation with selected indigenous mycorrhizal complex improves Ceratonia siliqua’s growth and response to drought stress

In the current study, we investigated the impact of inoculation with a selected indigenous arbuscular mycorrhizal fungi (AMF) complex on the growth and physiology of carob plants at increasing levels of watering (25, 50, 75 and 100% field capacity). The following growth and stress parameters were monitored in carob seedlings after 6 months of growth and 2 months of applied drought stress: fresh and dry weight, root and shoot lengths, leaf surface area, relative water content, stomatal conductance and membrane stability. Chlorophyll a and b, total soluble sugars, proline and protein contents were also determined along with the activities of stress enzymes: Catalase, Peroxidase and Superoxide dismutase. The obtained results indicate that inoculation with the indigenous AMF complex has a positive impact on the plant’s growth as all the assessed parameters were significantly improved in the mycorrhizal plants. Additionally, our results show that mycorrhization contributes to the minimization of the impact of drought stress on the carob plants and allows a better adaptation to dry conditions.     

Modelling the predicted geographic and economic response of UK cropping systems to climate change scenarios: the case of potatoes

Geographical changes in suitability in England and Wales for the cultivation of potatoes under a climate change scenario were predicted for the years 2023 and 2065 by integrating a climate database (1951-80) with climate-driven crop growth models. Initially, model outputs were produced as point values (meteorological site locations) of predicted potential yields for current crop production. The model outputs were validated statistically using actual crop yield figures collated from bibliographic analysis. The most suitable model was run again incorporating projected temperature and precipitation changes for 2023 and 2065. These outputs were then used to predict possible economic changes to farm profitability and general market trends. Results indicated that, although yields may rise, gross margins for maincrop and especially early potatoes may also rise due to shifts in production, to a fall in overall potato output and to price increases.     

Elevated CO2 concentration and temperature effects on the partitioning of chemical components along juvenile Scots pine stems (Pinus sylvestris L.)

The effects of doubled ambient [CO₂] and different temperature levels on young Pinus sylvestris growing in phytotron chambers were studied. Five chambers were supplied with ~380 (‘ambient air’) and five with ~700 μmol mol⁻¹ CO₂ (‘elevated [CO₂]’). Temperature levels in the chambers ranged in increment steps of 2°C from −4°C to +4°C relative to the long-term monthly (day and night) average air temperature levels in Berlin–Dahlem. Substrate was medium fertile; soil moisture and air humidity were kept constant. After three vegetation periods twigs and stems were harvested, weighed, homogenized, and analyzed chemically. There was no significant temperature effect on wood mass accumulation, clearest positive [CO₂] effect occurred in the youngest twigs. In total, wood mass increased by 28.5% at doubled ambient [CO₂]. N-contents (percentage) decreased at elevated [CO₂] in the uppermost stem sections and not in twig wood causing wider C/N ratios in total. In response to elevated temperature, N-contents decreased slightly in twigs (~0.3%). Traces of free glucose, fructose and sucrose, which decreased from the top to the bottom, were found in stem wood, in contrast to traces of starch that increased from the top to the bottom. In response to elevated [CO₂] only a little more (0.05%) was accumulated in the top shoot and in tendency; glucose, fructose, and sucrose contents were lower at the bottom of stems as compared to the control. There was no obvious response of these non-structural carbohydrates to elevated temperature except for starch that decreased to half of the content from the lowest to the highest temperature level. Among the hemicellulose compounds, rhamnose and arabinose declined from the top shoot to the bottom of stem, whereas 4-O-methyl-d-glucuronic-acid, mannose, and xylose increased. Contents (percentage) of galactose remained approximately stable along the stem. The clearest positive effect of elevated [CO₂] along the whole stem was found for mannose with differences of 0.6–0.3%. In contrast to rhamnose and arabinose that showed a negative response to elevated [CO₂], mannose was reduced towards the uppermost stem sections. The 4-O-methyl-d-glucuronic-acid was slightly lowered at the bottom, and galactose and xylose showed no [CO₂] response. The only hemicellulose compound which reacted to temperature elevation was galactose. It increased slightly (~0.1% per 1°C). Cellulose and lignin (Klason) behaved oppositely: cellulose increased and lignin decreased from the top to the bottom. These structural components behaved reversely also in response to elevated [CO₂]. In stem parts above the bottom section, cellulose content was slightly higher at elevated [CO₂], and lignin content was slightly lower at the bottom. Lignin reacted to temperature elevation by a very slight increase on the average (~0.1% per one 1°C). Cellulose, however, decreased by ~0.2% per 1°C temperature elevation. The importance of persistent sinks of carbon in woody plant parts is discussed in respect to the greenhouse effect.     

Interactive Effects of Elevated CO2 and Growth Temperature on the Tolerance of Photosynthesis to Acute Heat Stress in C3 and C4 Species

Determining effects of elevated CO2 on the tolerance of photosynthesis to acute heat-stress (heat wave) is necessary for predicting plant responses to global warming, as photosynthesis is thermolabile and acute heat-stress and atmospheric CO2 will increase in the future. Few studies have examined this, and past results are variable, which may be due to methodological variation. To address this, we grew two C3 and two C4 species at current or elevated CO2 and three different growth temperatures (GT). We assessed photosynthetic thermotolerance in both unacclimated (basal tolerance) and preheat-stressed (preHS = acclimated) plants. In C3 species, basal thermotolerance of net photosynthesis (Pn) was increased In high CO2, but in C4 species, Pn thermotlerance was decreased by high CO2 (except Zea maya at low GT); CO2 effects in preHS plants were mostly small or absent, though high CO2 was detrimental in one C3 and one C4 species at warmer GT. Though high CO2 generally decreased stomatal conductance, decreases in Pn during heat stress were mostly due to non-stomatal effects. Photosystem II (PSII) efficiency was often decreased by high CO2 during heat stress, especially at high GT; CO2 effects on post-PSll electron transport were variable. Thus, high CO2 often affected photosynthetic theromotolerance, and the effects varied with photosynthetic pathway, growth temperature, and acclimation state. Most importantly, in heat-stressed plants at normal or warmer growth temperatures, high CO2 may often decrease, or not benefit as expected, tolerance of photosynthesis to acute heat stress. Therefore, interactive effects of elevated CO2 and warmer growth temperatures on acute heat tolerance may contribute to future changes in plant productivity, distribution, and diversity.