Cold-hardiness in the predatory miteAmblyseius potentillae (Acari: Phytoseiidae)

Cold-hardiness was studied in the predatory miteAmblyseius potentillae (Garman) by determining the mortality after exposure to –5°C. Predators reared under diapause-inducing conditions were more cold-resistant than mites that had been kept under long-day conditions. An acclimatization period at 4°C prior to exposure to sub-zero temperatures had a positive effect on the cold-hardiness of the predator, and was remarkable in diapausing mites.Lower temperatures during diapause induction had a positive effect on cold resistance in this predator; mites in which diapause was induced at 15°C were more cold-resistant than mites that had been subjected to short-day conditions at 18 and 20°C.A day/night temperature rhythm did not increase the cold-hardiness of the mite when grown under long-day conditions. Such a rhythm did increase the cold-hardiness of the diapausing predator when given a short acclimatization period, but this effect disappeared after longer acclimatization periods.     

Cold-hardiness and development of eggs of Rhopalosiphum insertum

Abstract. 1. The eggs of Rhopalosiphum insertum (Walker) showed a seasonal increase in cold-hardiness under field conditions. Their supercooling point fell from -35°C in November to below -40°C in January, then rose to-35°C or above by March.
2. Laboratory experiments demonstrated that both temperature and date affected cold-hardiness of the eggs. The supercooling points of eggs kept at 16 h photoperiod or in darkness did not, however, differ significantly.
3. Eggs brought from the field into warm, long-day conditions would not hatch until after mid-January. After this date, per cent hatch was significantly greater in 16 h photoperiod than in darkness; it did not differ between eggs kept at 5 or 0°C, but was reduced at -5°C.
4. It is concluded that eggs of Rinserturn are in diapause until mid-January, and that hatching rate and cold-hardiness are determined by separate environmental factors.     

Cold-hardiness: a component of the diapause syndrome in pupae of the flesh flies, Sarcophaga crassipalpis and S. bullata

ABSTRACT. Diapausing pupae of Sarcophaga crassipalpis Macquart and S. bullata Parker reared at 20 or 25C readily survive exposure to - 10C for at least 25 days. In contrast, non-diapausing pupae produced by a variety of means are consistently intolerant of the low temperature. Non-diapausing pupae are not immediately killed by exposure to -10C: pupae exposed to the low temperature for up to 3 days proceed with pharate adult development but ultimately die before adult eclosion. Unlike many temperate zone insects, diapausing flesh fly pupae do not require a period of chilling for induction of cold-hardiness, and the attribute of cold-hardiness cannot be separated from other features of the diapause syndrome. Some cold-hardiness is already acquired during the third larval instar: diapause-destined larvae exposed to -10C are more successful in pupariating than non-diapause-destined larvae of the same age.     

松阿扁叶蜂越冬幼虫体内抗寒物质分析

用高效液相色谱法、氨基酸分析法、分光光度法等测定了不同时期松阿扁叶蜂AcantholydaposticalisMatsumura越冬幼虫体内抗寒物质含量,结果显示越冬期较越冬初期小分子碳水化合物、血淋巴丙氨酸、甘油、糖蛋白含量均有明显增加,依次增加了105,95,210和81%;而蛋白质、脂肪含量分别下降了16%,15%。据此认为越冬幼虫的抗寒物质系统为:小分子碳水化合物—丙氨酸—甘油—糖蛋白。     

Mapping of quantitative trait loci controlling adaptive traits in coastal Douglas-fir. IV. Cold-hardiness QTL verification and candidate gene mapping

Quantitative trait locus (QTL) analyses are used by geneticists to characterize the genetic architecture of quantitative traits, provide a foundation for marker-aided-selection (MAS), and provide a framework for positional selection of candidate genes. The most useful QTL for breeding applications are those that have been verified in time, space, and/or genetic background. In this study, spring cold-hardiness of Douglas-fir foliar tissues was evaluated in two clonally replicated (n=170 and 383 clones) full-sib cohorts derived from the same parental cross in two different years (made 5 years apart). The cohorts were established in widely separated forest test sites and tissues were artificially freeze tested using different cold injury assessment methods. Four of six unique QTL detected for spring cold-hardiness in needles of Cohort 1 were tentatively verified in the second cohort. Four additional QTL were detected in Cohort 2, two on linkage groups (LGs) not previously represented in the smaller cohort. In total, 10 unique QTL were identified across both cohorts. Seventeen of twenty-nine putative cold-hardiness candidate genes (Douglas-fir ESTs) placed on the Douglas-fir linkage map locate within the 95% confidence intervals of spring needle cold-hardiness QTL from the two cohorts and thus represent priority targets for initiating association mapping in Douglas-fir.     

Cold-hardiness of the most common soil invertebrates in Northeast Asia. 1. Cold-hardiness and its mechanisms

Cold-hardiness of soil-dwelling invertebrates (37 species of insect and 27 species from other taxa) was studied in the continental parts of Northeast Asia, which represent a region with winter temperatures extreme for the Northern Hemisphere. Insects belonging to 34 species overwinter in the supercooled state, whereby they withstand temperatures of–12...–35°C. Thirteen species (insects, myriapods, slugs, earthworms, and an amphipod) spend winter in the frozen state and survive temperatures from–5 to–45°C. Cryoprotective dehydration is typical of slug eggs, earthworm cocoons, and certain click beetle larvae, which survive temperatures ranging from–20 to–40°C, down to the record value of–196°C. The majority of the studied organisms tolerate cooling to–25...–30°C, which corresponds to average temperature minima in the upper soil horizons of most biotopes in the continental parts of the Asian Northeast.     

ADAPTATIONS TO TEMPERATE CLIMATES AND EVOLUTION OF OVERWINTERING STRATEGIES IN THE DROSOPHILA MELANOGASTER SPECIES GROUP

The Drosophila melanogaster species group is considered to have originated in the tropics and only recently invaded temperate habitats. The temperate species of this group that were studied here may be subdivided into the warm-temperate species (D. lutescens and D. rufa) and the cool-temperate species (species of the auraria complex). The warm-temperate species were more cold-hardy than were their tropical relatives (D. takahashii or D. melanogaster) at the larval and imaginal stages, and the cool-temperate species were more cold-hardy than the warm-temperate species, although only at the imaginal stage. However, these species showed little or no intraspecific variation in cold-hardiness, in spite of great variation in winter temperature within the species' ranges. It is assumed that cold-hardiness is one of the main factors restricting their distributions at high latitudes and that it is the key for evolution of the warm- and cool-temperate species from their subtropical or warm-temperate ancestors. Both warm- and cool-temperate species had photoperiodically controlled reproductive diapause. In the cool-temperate species, the development of cold-hardiness was affected by diapause, but diapause had little or no effect on cold-hardiness in the warm-temperate species. Critical daylengths and the diapause rates varied from species to species according to variation in their overwintering plans and also varied geographically in consequence of their adaptation to local climates. Species showed different responses to temperature in preimaginal and ovarian development. These differences are considered to reflect adaptation to different environmental temperatures.     

Is cold hardiness size-constrained? A comparative approach in land snails

Body water is a major element of the cold-hardiness strategies observed in ectothermic animals, in particular in freezing avoidant species for which body ice formation is lethal. Here, we investigate the relationships, in terrestrial snails, between the temperature of crystallisation (Tc) and body water (water mass and water content), shell shape, geographic and climatic distribution, taking into account phylogenetic inertia. Phylogenetic relationships among 31 species from 13 different families of terrestrial Gastropods were studied using 28S rRNA nuclear and COI mitochondrial sequence data, together with species-specific traits. Our results provide evidence for clear relationships between Tc and absolute/relative body water: smaller species with lower water content tended to be characterized by colder temperatures of crystallisation, although some exceptions were noticeable. Environmental conditions do not appear to affect Tc significantly, as well as shell shape which is however correlated with water content. This study confirmed that supercooling ability in land snails is size-constrained, with consequences on cold-hardiness strategies.     

Is the strategy for cold hardiness in insects determined by their water balance? A study on two closely related families of beetles: Cerambycidae and Chrysomelidae

The strategy for cold-hardiness and water balance features of two closely related families of Coleoptera, Cerambycidae and Chrysomelidae, were investigated. Cerambycids were freeze-avoiding with low supercooling points, whereas chrysomelids froze at high temperatures and were tolerant to freezing. Hence, the two families have adopted different strategies for cold-hardiness. Due to their low trans-cuticular water permeability, the cerambycids have low rates of evaporative water loss. Chrysomelids have much higher trans-cuticular water permeability, but freezing brings their body fluids in vapour pressure equilibrium with ice and prevents evaporative water loss. The differences in cold-hardiness strategies and rates of water loss are likely to reflect the water content of the diets of the two families. Cerambycids feed on dry wood with low water content, causing a restrictive water balance. Chrysomelids feed on leaves with high water content and may use evaporation through the cuticle as a route of water excretion. Haemolymph ice nucleators help chrysomelids to freeze at a high temperature and thus to maximize the period they spend in the water saving frozen state. The diet-related differences in water balance may be the reason why the two families have developed different strategies for cold-hardiness.     

Physiological ecology of overwintering in the hatchling painted turtle: multiple-scale variation in response to environmental stress

We integrated field and laboratory studies in an investigation of water balance, energy use, and mechanisms of cold-hardiness in hatchling painted turtles (Chrysemys picta) indigenous to west-central Nebraska (Chrysemys picta bellii) and northern Indiana (Chrysemys picta marginata) during the winters of 1999-2000 and 2000-2001. We examined 184 nests, 80 of which provided the hatchlings (n=580) and/or samples of soil used in laboratory analyses. Whereas winter 1999-2000 was relatively dry and mild, the following winter was wet and cold; serendipitously, the contrast illuminated a marked plasticity in physiological response to environmental stress. Physiological and cold-hardiness responses of turtles also varied between study locales, largely owing to differences in precipitation and edaphics and the lower prevailing and minimum nest temperatures (to -13.2 degrees C) encountered by Nebraska turtles. In Nebraska, winter mortality occurred within 12.5% (1999-2000) and 42.3% (2000-2001) of the sampled nests; no turtles died in the Indiana nests. Laboratory studies of the mechanisms of cold-hardiness used by hatchling C. picta showed that resistance to inoculative freezing and capacity for freeze tolerance increased as winter approached. However, the level of inoculation resistance strongly depended on the physical characteristics of nest soil, as well as its moisture content, which varied seasonally. Risk of inoculative freezing (and mortality) was greatest in midwinter when nest temperatures were lowest and soil moisture and activity of constituent organic ice nuclei were highest. Water balance in overwintering hatchlings was closely linked to dynamics of precipitation and soil moisture, whereas energy use and the size of the energy reserve available to hatchlings in spring depended on the winter thermal regime. Acute chilling resulted in hyperglycemia and hyperlactemia, which persisted throughout winter; this response may be cryoprotective. Some physiological characteristics and cold-hardiness attributes varied between years, between study sites, among nests at the same site, and among siblings sharing nests. Such variation may reflect adaptive phenotypic plasticity, maternal or paternal influence on an individual's response to environmental challenge, or a combination of these factors. Some evidence suggests that life-history traits, such as clutch size and body size, have been shaped by constraints imposed by the harsh winter environment.     

Cold-hardiness of Dermacentor marginatus (Acari: Ixodidae)

The cold-hardiness of Dermacentor marginatus using laboratory-reared offspring of ticks collected in Germany was characterized. Investigations of unfed stages revealed that adult ticks suffered 50% mortality at –10°C after 4–5 months, but larvae and nymphs suffered mortality within few days, whereas –15°C was lethal for all stages within a very short period. Larval hatch and moulting of engorged larvae and nymphs did not occur at 10°C. Embryonic development of eggs with larval hatch was considerably reduced by exposure of eggs to 10°C. Engorged females did not lay eggs at 10°C, the oviposition capability, however, persisted over 6 months at 10°C, 5 months at 5°C, 3 months at 0°C and 2 months at –10°C without substantial decrease of the oviposition capacity or reduction of viable eggs. These results present evidence that unfed adult ticks are the ecoepidemiologically most effective stages, which are capable to tolerate long and extremely cold winters without substantial impairment of the population density. It is also considered that engorged females interrupt their oviposition at low and subzero temperatures delaying it for months and so contribute in bypassing winter conditions. None of the stages survived supercooling indicating that D. marginatus is freeze intolerant. Mean supercooling point (SCP) ranged between –26°C in eggs and –12, 6°C in engorged females. Compared with eggs, the SCP of the other stages was significantly higher. In conclusion, the SCP is considered to have no predictive value in the context with cold-hardiness.     

Cold-hardiness of the phoretic mites Anoetus myrmicarum (Acariformes,Anoetidae) from the ants Formica lemani (Hymenoptera,Formicidae) in the Kolyma Highland

In the sparse larch forests of the upper Kolyma River, hypopi of the mite Anoetus myrmicarum (Scheucher, 1957) were found in several nests of the ant Formica lemani Bondroit, 1917. These mites were not found in hundreds of nests of the other 10 ant species examined in northeastern Asia. A possible ecological and physiological conditionality of the restricted distribution of phoretic mites was analyzed. For this purpose, coldhardiness of mites and their ant hosts, the biotopic distribution and the structure of nests, and the temperature conditions of overwintering were examined. At the stage of hypopus, the mites overwintered on ants in the overcooled stage; their mean supercooling temperatures (SCP) varied from ?25.8 ± 0.3°C to ?27.7 ± 0.4°C (min ?32.2°C, n = 157). These values were by 0.1 to 7.0°C lower than the mean SCP of the ants from 8 tested nests of F. lemani (?20.7 ± 0.5°C to ?25.7 ± 0.8°C). The soil temperatures at the level of winter chambers varied from ?12°C to ?15°C. Scarcity of findings of Anoetus myrmicarum in the Kolyma Highland is not associated with the limited cold-hardiness of the examined stages, but is most probably determined by interrelations between mites and ants.     

Overwintering ecology of <Emphasis Type="Italic">Philonthus rotundicollis</Emphasis> (Coleoptera,Staphylinidae) in the nest of the carpenter ant <Emphasis Type="Italic">Camponotus herculeanus</Emphasis> on the coast of the Sea of Okhotsk

A widespread rove beetle species, Philonthus rotundicollis, whose distribution range stretches across different climatic zones, including the coldest regions of the Asian northeast, was discovered as an inquiline within the nests of the carpenter ant Camponotus herculeanus on the coast of the Sea of Okhotsk in winter. It remained unclear if the beetles had significant cold-hardiness and whether they overwintered deep in the soil or were confined to particularly warm habitats. To clarify these aspects, the following metrics of cold-hardiness were measured: supercooling point (SCP), freezing point (FP), supercooling capacity (SCP-FP), and temperature minima at the beetles’ overwintering sites. In Ph. rotundicollis, mean SCP was -11.1 ± 0.7°C (ranging from - 7.9 to -18.8°C, n + 15), which was insufficient for successful overwintering even on the coast, since temperature minima in leaf litter during a snow-deficient winter fell to -14°C at the depth of 5 cm and -12°C at 20 cm. The beetles could not burrow deep into stiff soil and made use of crevices in dry peat-like soil layers as well as tunnels of soil- and rootdwelling animals, including carpenter ants. The presence of this rove beetle species in the ant nest was probably due to feeding on ant larvae because, at near-zero temperatures, the activity threshold of the beetles was lower than that of the ants that guarded the larvae.     

Cold-hardiness of the Antarctic winged midge Parochlus steinenii during the active season at King George Island

Summary The Antarctic winged midge Parochlus steinenii (Diptera:Chironomidae) and its immatures were collected from freshwater lakes near Great Wall Station (62°13S,58°58W) on King George Island during January and February in 1990. They were examined for supercooling ability and lower lethal temperature. They were all intolerant to freezing. Supercooling points (spontaneous freezing points) of the larvae, pupae and adults were -7.4° ±1.0°, -16.3°±4.6° and -15.3°±5.6°C, respectively. These values represented the potential limits of cold-hardiness of this species. But the median lower lethal temperatures examined under an aqueous condition were always higher than the corresponding mean supercooling points. Half of the larvae, pupae and adults in the aqueous condition were killed at about -3°, -9° and -7°C, respectively, probably due to inoculative freezing. These temperatures seemed to be the natural lower limits of survival in the immatures and some adults of this species, at least in the active season.     

Physiological adaptations of coccinellidae to supranivean and subnivean hibernacula

The supranivean hibernaculum of Hippodamia convergens allows exposure of this species to fluctuating temperatures and humidities. Correspondingly, H. convergens is resistant to desiccation, maintains cold-hardiness independent of temperature, and responds to warm acclimation with a reduced respiration rate. Beneath the snow, Coleomegilla maculata is maintained at a constant temperature and high humidity. Warm acclimation in this species results in a loss of cold-hardiness and an increase in respiration rate. This response suggests a transition from an energy-conserving metabolic state associated with overwintering to one of energy expenditure as the beetles prepare for summer feeding and reproduction.     

Mapping of quantitative trait loci controlling adaptive traits in coastal Douglas-fir. II. Spring and fall cold-hardiness

Quantitative trait loci (QTLs) affecting fall and spring cold-hardiness were identified in a three-generation outbred pedigree of coastal Douglas-fir [Pseudotsuga meniziesii (Mirb.) Franco var. menziesii]. Eleven QTLs controlling fall cold-hardiness were detected on four linkage groups, and 15 QTLs controlling spring cold-hardiness were detected on four linkage groups. Only one linkage group contained QTLs for both spring and fall cold-hardiness, and these QTLs tended to map in close proximity to one another. Several QTLs were associated with hardiness in all three shoot tissues assayed in the spring, supporting previous reports that there is synchronization of plant tissues during de-acclimatization. For fall cold-hardiness, co-location of QTLs was not observed for the different tissues assayed, which is consistent with previous reports of less synchronization of hardening in the fall. In several cases, QTLs for spring or fall cold-hardiness mapped to the same location as QTLs controlling spring bud flush. QTL estimations, relative magnitudes of heritabilities, and genetic correlations based on clonal data in this single full-sib family, supports conclusions about the genetic control and relationships among cold-hardiness traits observed in population samples of Douglas-fir in previous studies. Received: 20 July 2000 / Accepted: 19 October 2000     

Drought resistance in early and late secondary successional species from a tropical dry forest: the interplay between xylem resistance to embolism,sapwood water storage and leaf shedding

The mechanisms of drought resistance that allow plants to successfully establish at different stages of secondary succession in tropical dry forests are not well understood. We characterized mechanisms of drought resistance in early and late‐successional species and tested whether risk of drought differs across sites at different successional stages, and whether early and late‐successional species differ in resistance to experimentally imposed soil drought. The microenvironment in early successional sites was warmer and drier than in mature forest. Nevertheless, successional groups did not differ in resistance to soil drought. Late‐successional species resisted drought through two independent mechanisms: high resistance of xylem to embolism, or reliance on high stem water storage capacity. High sapwood water reserves delayed the effects of soil drying by transiently decoupling plant and soil water status. Resistance to soil drought resulted from the interplay between variations in xylem vulnerability to embolism, reliance on sapwood water reserves and leaf area reduction, leading to a tradeoff of avoidance against tolerance of soil drought, along which successional groups were not differentiated. Overall, our data suggest that ranking species' performance under soil drought based solely on xylem resistance to embolism may be misleading, especially for species with high sapwood water storage capacity.     

寄主植物对甜菜夜蛾三龄幼虫抗寒力的影响

寄主植物是影响昆虫抗寒性的主要因子之一。研究了不同温度下甜菜夜蛾Spodoptera exigua(Hübner)3龄幼虫取食小白菜、甘蓝、葱和菠菜后,对过冷却能力和体内冷冻保护剂的影响。结果表明,寄主植物对甜菜夜蛾3龄幼虫的过冷却能力有显著性影响,其中以取食甘蓝的幼虫过冷却点最低。温度和寄主植物对其过冷却点、结冰点和虫体含水量有明显的交互作用。寄主植物对其体内的海藻糖含量有显著性影响,而对甘油和糖原含量没有显著性影响。温度和寄主植物仅对海藻糖含量有显著的交互作用。随着温度的升高,取食不同寄主的幼虫体内海藻糖和糖原含量的变化趋势完全相反,认为海藻糖是由糖原转化而来。研究结果提示冬季合适的寄主植物有利于甜菜夜蛾低龄幼虫越冬。     

不同时期毛乌素沙区主要植物种光合作用和蒸腾作用的变化

 采用LI—6000便携式光合分析系统对毛乌素沙区主要植物种油蒿、中间锦鸡儿、旱柳进行了不同时期光合作用,蒸腾作用日进程的测定,并同步测定有效光辐射、空气相对湿度、叶温、气温、胞间CO2浓度、气孔阻力、叶片水势及土壤水势等因子;结果表明：不同时期、不同植物种其光合、蒸腾特征各异;植物的光合、蒸腾与环境因子和植物内部因子之间有密切关系,其中有效光辐射是影响光合作用、蒸腾作用诸因子中的主导因子,而气孔阻力变化则在调节光合和蒸腾中起着重要作用;不同植物种间气孔对环境条件变化的响应程度不同,以中间锦鸡儿最为灵敏;3种植物的水分利用效率表明,中间锦鸡儿的水分利用效率较油蒿、旱柳为高。