TheleafbeetlePhratoravulgatissima（Linnaeus 1758）iscommonlyunivoltine in south-central Sweden but may sometimes initiate a partial second generation. The current study was set out to investigate under what abiotic co...TheleafbeetlePhratoravulgatissima（Linnaeus 1758）iscommonlyunivoltine in south-central Sweden but may sometimes initiate a partial second generation. The current study was set out to investigate under what abiotic conditions the beetles initiate a second generation. Using climate chamber experiments, the beetles were shown to have a facultative reproductive diapause induced by declining day-length. The critical day-length （CDL） for diapause induction was estimated to be 18 h and 10 min. In the field, firstgeneration beetles developing to adulthood before August in 2009 became reproductively active and produced a second generation, but most individuals emerged later and were in reproductive diapause. P vulgatissima overwinter as adults and diapause was shown to be maintained until mid-winter in 2008/2009. The cumulative temperature requirement for oviposition after diapause termination was estimated to be 222 day-degrees with a 5.5℃ temperature threshold. Three different day-degree models that were developed to predict the phenology of female oviposition in the spring were validated by comparing model results with field data on the timing of oviposition in previous years. The study suggests that P vulgatissima may initiate a second generation in Sweden if development of the first generation is completed before August. Warmer spring and summer temperatures due to ongoing climate change may cause advanced insect phenology and faster completion of insect life-cycles at northern latitudes, which will affect the proportion of insects that initiate a second generation.展开更多
Low desiccation resistance of Drosophila ananassae reflects its rarity outside the humid tropics. However, the ability of this sensitive species to evolve under seasonally varying subtropical areas is largely unknown....Low desiccation resistance of Drosophila ananassae reflects its rarity outside the humid tropics. However, the ability of this sensitive species to evolve under seasonally varying subtropical areas is largely unknown. D. ananassae flies are mostly lighter during the rainy season but darker and lighter flies occur in the autumn season in northern India. We tested the hypothesis whether seasonally varying alternative body color phenotypes of D. ananassae vary in their levels of environmental stress tolerances and mating behavior. Thus, we investigated D. ananassae flies collected during rainy and autumn seasons for changes in body melanization and their genetic basis, desiccation-related traits, cold tolerance and mating propensity. On the basis of genetic crosses, we found total body color dimorphism consistent with a single gene model in both sexes olD. ananassae. A significant increase in the frequency of the dark morph was observed during the drier autumn season, and body color phenotypes showed significant deviations from Hardy-Weinberg equilibrium, which suggests climatic selection plays a role. Resistance to desiccation as well as cold stress were two- to three-fold higher in the dark body color strain as compared with the light strain. On the basis of no-choice mating experiments, we observed significantly higher assortative matings between dark morphs under desiccation or cold stress, and between light morphs under hot or higher humidity conditions. To the best of our knowledge, this is the first report on the ecological significance of seasonally varying total body color dimorphism in a tropical species, D. ananassae.展开更多
文摘TheleafbeetlePhratoravulgatissima（Linnaeus 1758）iscommonlyunivoltine in south-central Sweden but may sometimes initiate a partial second generation. The current study was set out to investigate under what abiotic conditions the beetles initiate a second generation. Using climate chamber experiments, the beetles were shown to have a facultative reproductive diapause induced by declining day-length. The critical day-length （CDL） for diapause induction was estimated to be 18 h and 10 min. In the field, firstgeneration beetles developing to adulthood before August in 2009 became reproductively active and produced a second generation, but most individuals emerged later and were in reproductive diapause. P vulgatissima overwinter as adults and diapause was shown to be maintained until mid-winter in 2008/2009. The cumulative temperature requirement for oviposition after diapause termination was estimated to be 222 day-degrees with a 5.5℃ temperature threshold. Three different day-degree models that were developed to predict the phenology of female oviposition in the spring were validated by comparing model results with field data on the timing of oviposition in previous years. The study suggests that P vulgatissima may initiate a second generation in Sweden if development of the first generation is completed before August. Warmer spring and summer temperatures due to ongoing climate change may cause advanced insect phenology and faster completion of insect life-cycles at northern latitudes, which will affect the proportion of insects that initiate a second generation.
文摘Low desiccation resistance of Drosophila ananassae reflects its rarity outside the humid tropics. However, the ability of this sensitive species to evolve under seasonally varying subtropical areas is largely unknown. D. ananassae flies are mostly lighter during the rainy season but darker and lighter flies occur in the autumn season in northern India. We tested the hypothesis whether seasonally varying alternative body color phenotypes of D. ananassae vary in their levels of environmental stress tolerances and mating behavior. Thus, we investigated D. ananassae flies collected during rainy and autumn seasons for changes in body melanization and their genetic basis, desiccation-related traits, cold tolerance and mating propensity. On the basis of genetic crosses, we found total body color dimorphism consistent with a single gene model in both sexes olD. ananassae. A significant increase in the frequency of the dark morph was observed during the drier autumn season, and body color phenotypes showed significant deviations from Hardy-Weinberg equilibrium, which suggests climatic selection plays a role. Resistance to desiccation as well as cold stress were two- to three-fold higher in the dark body color strain as compared with the light strain. On the basis of no-choice mating experiments, we observed significantly higher assortative matings between dark morphs under desiccation or cold stress, and between light morphs under hot or higher humidity conditions. To the best of our knowledge, this is the first report on the ecological significance of seasonally varying total body color dimorphism in a tropical species, D. ananassae.
