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71.
Freeze-protection of overwintering monarch butterflies in Mexico: critical role of the forest as a blanket and an umbrella 总被引:1,自引:0,他引:1
Abstract. 1. At their high-altitude overwintering sites in Mexico, monarch butterflies frequently are subjected to sub-zero°C temperatures during December-March. Although monarchs have moderate supercooling ability, two ecological factors strongly influence their capacity to resist freezing: wetting and exposure to the clear night sky. 2. As shown in Fig. 2, 50% of a population of butterflies with water on their body surfaces freeze at warmer sub-zero temperatures (-4.2°C) compared to butterflies with no water on their bodies (-7.7°C). 100% mortality occurs, respectively, at ?7.7°C and ?15°C. 3. Comparative measurements of rainfall within a large overwintering colony in Mexico indicated that the intact canopy acts as an umbrella that reduces butterfly wetting during winter storms. 4. Variable experimental exposure of butterflies to the clear night sky indicated that openings in the forest canopy increases radiational cooling and causes monarch body temperatures to drop as much as 4°C below ambient air temperature. Monarchs under dense cover had body temperatures approximately the same as the ambient air temperature, but more exposed individuals had body temperatures below ambient in direct proportion to the degree of exposure. Consequently, forest thinning increases the probability that the butterflies will freeze to death. 5. Whereas both wetting and exposure are increased by disturbance of the forest canopy, the interaction of these two factors exacerbates freezing mortality during winter storms: 50% of dry and unexposed butterflies froze at ?8°C, whereas wetted and fully exposed butterflies froze at only ?0.5°C. 6. Butterflies inside and on the bottom of the fir bough clusters are better protected from wetting than those on the outside. This supports the hypothesis that the structure of the butterfly clusters has evolved through individual selection to avoid wetting. 7. The data strongly reinforce previous evidence that forest thinning should be totally prevented within and adjacent to the overwintering sites in order to minimize both wetting and exposure of the butterflies that synergistically increase winter mortality at the overwintering sites in Mexico. 相似文献
72.
To evaluate the suitability of using ice nucleation active (INA) bacteria for the biological control of insect pests, the supercooling point (SCP) of larvae of mulberry pyralid,Glyphodes duplicalis,and silkworm,Bombyx mori,ingesting INA strains ofErwinia(Pantoea)ananasandPseudomonas syringaewas determined. Mean SCP of the guts of silkworm larvae ingesting INA strains ofE. ananasranged from −2.5 to −2.8°C, being 5°C higher than that in control treatments. Similarly, mean SCP of mulberry pyralid larvae ingesting INA strain ofE. ananas,which can grow well in the gut, was −4.7°C at 3 days after treatment, being 6.5°C higher than that in control treatments. On the other hand, mean SCP of the larvae-ingesting INA strain ofP. syringae,which cannot grow in the gut, was −9.0°C at 3 days after treatment, rising by only 2.5°C higher than that in the control treatments. In addition, more than 80% of the larvae of mulberry pyralid ingesting the INA strain ofE. ananasfroze and eventually died when exposed to −6°C for 18 h, while only 36% of the larvae ingesting the INA strain ofP. syringae,or approximately 20% of the control larvae, froze and died. Thus, the gut colonization by INA strains ofE. ananasreduced remarkably the cold hardiness of the insects. These findings suggest that INA strains ofE. ananascould be effective as a potential biological control agent of insect pests. 相似文献
73.
The bruchid beetle, Bruchidius dorsalis Fahraeus (Coleoptera: Bruchidae), has a multivoltine life cycle and shows geographical variation of overwintering stages in Japan. Our previous study found that B. dorsalis enters larval diapause in the final instar under short photoperiods. In cooler areas, we observed that most individuals overwinter in the final larval stage in diapause, whereas beetles at different developmental stages (non‐diapausing young instars, diapausing instars, and adults) were overwintering in warmer areas. In this study, we investigated geographical variation in the photoperiodic response for induction of larval diapause at 20 °C (three populations) and 24 °C (two populations) to clarify the overwintering strategy of B. dorsalis. We observed that (1) diapause incidence at 20 °C changed sharply from ca. 100% to 0% with a change in photoperiod in all the populations, (2) critical photoperiod was longer at 20 °C in populations from cooler areas, and (3) critical photoperiod at 24 °C was shorter than at 20 °C and a fraction of the larvae did not enter diapause, even under short photoperiods. Overwintering stages estimated from these results were consistent with those actually observed in the field. This study indicates that the geographical variation of overwintering stages is likely to reflect adaptive diapause induction in each local environment. 相似文献
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75.
柿绒蚧形态和生物学的进一步研究 总被引:1,自引:1,他引:0
作在初步研究了柿绒蚧Eriococcus kaki Kuwana的生物学特征和防治技术(1992)的基础上,本进一步报道各虫期的外部形态特征,南京地区的生活史,尤其是明确了越冬虫龄及冬后发育与温度的关系。 相似文献
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78.
Jannik Schultner B?rge Moe Olivier Chastel Claus Bech Alexander S. Kitaysky 《Biology letters》2014,10(1)
Changes in telomere length are believed to reflect changes in physiological state and life expectancy in animals. However, much remains unknown about the determinants of telomere dynamics in wild populations, and specifically the influence of conditions during highly mobile life-history stages, for example migration. We tested whether telomere dynamics were associated with migratory behaviour and/or with stress during reproduction in free-living seabirds. We induced short-term stress during reproduction in chick-rearing, black-legged kittiwakes (Rissa tridactyla), tracked winter migration with geolocators and measured telomere length before and after winter migration. We found that time spent at wintering grounds correlated with reduced telomere loss, while stress during reproduction accelerated telomere shortening. Our results suggest that different life-history stages interact to influence telomere length, and that migratory patterns may be important determinants of variation in an individual''s telomere dynamics. 相似文献
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80.
Abstract The aim of this paper was to test the hypothesis that the presence of overwintering Calomys venustus males or females at the beginning of the breeding period reduced the survival of juveniles belonging to the first cohort of each year (C1). The study was carried out in four 0.25‐ha enclosures (two control and two experimental), each situated on natural pasture. This study was conducted between August 1997 and February 1999 and had two parts: removal of overwintering males (ROM) and removal of overwintering females (ROF). For the ROM treatment, overwintering males were removed immediately after C1 juveniles were born, in the ROF treatment overwintering females were removed after the C1 were weaned. Weekly censuses were taken for 3 successive days over 6 weeks. Juvenile survival was examined through a survivorship schedule. The survivorship values were compared by sex and treatment (removal of overwintering males or females) using repeated‐measures anova . Removal of overwintering males and females did not improve the survival of C1 juveniles. This result could be related to the delay in maturation of C1 juvenile males. 相似文献