昆虫的夏滞育

夏滞育作为昆虫越夏的生态策略 ,已广泛引起昆虫学家的重视。本文就几十年来夏滞育研究的进展进行综述。着重讨论诱导、维持、终止夏滞育的主要环境因子 ,夏滞育的生态特征和它的生态适应意义。     

Multilevel studies on the two phenological forms of Large Blue (Maculinea arion) (Lepidoptera: Lycaenidae)

The main goal of our research was to study comprehensively the differences between the two phenological forms of the socially parasitic and globally threatened Large Blue (Maculinea arion) in the Carpathian Basin using four character sets (mitochondrial sequences, allozymes, male genitalia and wing morphometrics). Comparative analyses of distance matrices, phylogenetic trees and ordination patterns have been applied. The genetic and morphometric patterns revealed by our studies were discordant. While we experienced a significant differentiation between the ‘spring’ and ‘summer type’ of M. arion in both wing and genital traits, the two phenological forms did not show any genetic differentiation on two mitochondrial loci and in allozymes. At the same time, all individuals were infected by Wolbachia. Although certain wing traits may not represent reliable tracers of phylogeny because of the particular adaptive significance, the wing characteristics involved in our research are probably determined genetically. Additionally, the significant differentiation of male genitalia also indicates incipient prezygotic isolation arising from phenological differentiation between the ‘spring and summer arion’. It is possible that all extant differences between the two forms are attributable to (1) different host‐ant use, (2) incipient speciation, (3) cytoplasmatic incompatibility (CI) by Wolbachia or the combination of these factors. In addition, discordant results indicate that the combined use of different approaches and data sets is strictly necessary to clarify systematic and evolutionary relationships.     

Seed dormancy and control of germination in Sisymbrella dentata (L.) O.E. Schulz (Brassicaceae)

• Seed germination responsiveness to environmental cues is crucial for plant species living in changeable habitats and can vary among populations within the same species as a result of adaptation or modulation to local climates. Here, we investigate the germination response to environmental cues of Sisymbrella dentata (L.) O.E. Schulz, an annual endemic to Sicily living in Mediterranean Temporary Ponds (MTP), a vulnerable ecosystem.
• Germination of the only two known populations, Gurrida and Pantano, was assessed over a broad range of conditions to understand the role of temperatures, nitrate, hormones (abscisic acid – ABA and gibberellins – GA) and after‐ripening in dormancy release in this species.
• Seed germination responsiveness varied between the two populations, with seeds from Gurrida germinating under a narrower range of conditions. Overall, this process in S. dentata consisted of testa and endosperm rupture as two sequential events, influenced by ABA and GA biosynthesis. Nitrate addition caused an earlier testa rupture, after‐ripening broadened the thermal conditions that allow germination, and alternating temperatures significantly promoted germination of non‐after‐ripened seeds.
• Primary dormancy in S. dentata seeds likely allows this plant to form a persistent seed bank that is responsive to specific environmental cues characteristic of MTP habitats.

     

Larger temperature response of autumn leaf senescence than spring leaf‐out phenology

Climate warming is substantially shifting the leaf phenological events of plants, and thereby impacting on their individual fitness and also on the structure and functioning of ecosystems. Previous studies have largely focused on the climate impact on spring phenology, and to date the processes underlying leaf senescence and their associated environmental drivers remain poorly understood. In this study, experiments with temperature gradients imposed during the summer and autumn were conducted on saplings of European beech to explore the temperature responses of leaf senescence. An additional warming experiment during winter enabled us to assess the differences in temperature responses of spring leaf‐out and autumn leaf senescence. We found that warming significantly delayed the dates of leaf senescence both during summer and autumn warming, with similar temperature sensitivities (6–8 days delay per °C warming), suggesting that, in the absence of water and nutrient limitation, temperature may be a dominant factor controlling the leaf senescence in European beech. Interestingly, we found a significantly larger temperature response of autumn leaf senescence than of spring leaf‐out. This suggests a possible larger contribution of delays in autumn senescence, than of the advancement in spring leaf‐out, to extending the growing season under future warmer conditions.     

叉头转录因子1基因FOXO1的特征及其在葱蝇夏滞育前期蛹体内糖脂代谢中的作用(英文)

【目的】克隆和鉴定葱蝇Delia antiqua叉头转录因子1基因,探究其在葱蝇夏滞育前期蛹体内糖代谢和脂代谢中的作用。【方法】本研究基于葱蝇转录组数据利用3′RACE法克隆叉头转录因子1基因的全长开放阅读框;利用生物信息学法分析了该基因编码蛋白的序列特征、保守结构域和二级结构,并采用最大似然法对其与其他13种昆虫来源的同源序列进行了聚类分析。通过RNA干扰技术沉默目的基因后,采用实时定量PCR法分析葱蝇夏滞育前期蛹体内目的基因下游脂肪酶brummer基因(DaBmm)和磷酸烯醇式丙酮酸羧化酶基因(DaDepck)的表达规律,并对甘油三脂(TAG)、海藻糖和葡萄糖含量及总脂肪酶的活性变化进行分析。【结果】克隆得到了葱蝇叉头转录因子1基因DaFOXO1 (GenBank登录号: MG813258),其编码蛋白含有619个氨基酸,具有典型的叉头DNA结合域,核定位信号,2个14-3-3结合区和1个富含谷氨酰胺区;DaFOXO1与铜绿蝇Lucilia cuprina FOXO1蛋白的氨基酸序列有87%的一致性,并与其聚为一支。干扰葱蝇夏滞育前期蛹DaFOXO1后,8-20 h间可显著抑制DaBmm基因的表达,12-24 h间可显著影响TAG含量和总脂肪酶的活性,8-20 h(16 h除外)间可显著降低DaPepck的表达,但对葡萄糖和海藻糖的含量没有显著影响。【结论】本研究结果表明海藻糖和葡萄糖的积累在化蛹前已完成;DaFOXO1对DaBmm和DaDepck基因的表达调控可能有利于葱蝇夏滞育前期蛹体内的脂肪积累。同时也表明靶向Bmm依赖性脂类水解过程及其下游因子可为打破昆虫滞育提供一种有效策略。     

Influence of pastoral fallow on plant root growth and soil physical and chemical characteristics in a hill pasture

Pastoral fallowing over a growing season (October–May) has a profound effect on standing biomass and sward structure, and should have an impact on below ground plant growth and soil biological activities. Two field studies were conducted to compare the effects of pastoral fallow with rotational grazing on root growth and soil physical and chemical properties. Root growth and distribution was altered by pastoral fallowing and there was significantly (P < 0.01) less root biomass at 0–50 mm depth of soil in the fallowed sward than the grazed sward. Compared with the grazed treatment, pastoral fallow increased soil air permeability at 500 mm tension by 38%, saturated hydraulic conductivity by 26%, unsaturated hydraulic conductivity at 20 mm tension by 67% and soil moisture by 10–15%, and reduced soil bulk density by 11%. Fallowing had little effect on soil nutrients both at the end of fallowing, except for small reductions in K and Mineral N levels at 0–75 mm soil depth, and two to three years after fallowing.     

休闲期深翻时间对旱地麦田土壤水分特性和小麦产量的影响

通过3个年度田间试验,研究了休闲期深翻时间对小麦播前0～200 cm土壤蓄水、生育期耗水及生长发育的影响.结果表明: 休闲期蓄水量受深翻时间、休闲期降雨量和降雨分布的影响.随休闲期深翻时间的推迟,0～200 cm土壤蓄水量先升高后降低,8月上中旬深翻蓄水效果好,较7月中旬深翻多蓄水23.9～45.8 mm;休闲期降雨多或集中在8—9月有利于增加土壤蓄水.休闲期适时深翻可增加土壤蓄水量,促进小麦对氮、磷的吸收,增加冬前茎数和成穗数,8月中上旬深翻较7月中旬深翻增产3.7%～18.2%.产量与休闲期0～200 cm土壤蓄水量、生育期各层土壤耗水量呈正相关,且受春季小麦生育关键期降雨影响较大,降雨多时相关性低,否则相关性高.深翻时间对生育期60～140 cm土层耗水量影响较大.当前耕作条件下,山西南部丘陵旱地在立秋(8月6日)前发挥留高茬和麦秸覆盖的保墒作用,立秋后至处暑(8月21日)期间深翻可提高土壤渗水特性,纳秋雨多蓄水,增加小麦冬前茎数和成穗数,使产量增加.     

不同栽培模式对冬小麦-夏玉米轮作系统产量、氮素累积和平衡的影响

以河北山前平原区秸秆还田条件下小麦-玉米轮作体系为研究对象,设置农民习惯、高产高效、再高产和再高产高效4个模式,通过定位试验探讨各栽培模式对3个轮作周期作物产量、土壤硝态氮累积量及氮平衡的影响.结果表明: 小麦、玉米产量均以再高产模式最高,高产高效和再高产高效模式次之,均显著高于农民习惯模式;小麦季和玉米季氮肥利用效率(PFP)均以高产高效模式最高,显著高于其他模式;0～400 cm土体硝态氮累积量在 768.4～1133.3 kg·hm^-2之间,其中80%～85%累积在根下90～400 cm土层;4种模式的土壤硝态氮均有明显向下淋移现象,120～150 cm和270～330 cm处均出现了累积峰,以270～330 cm土层硝态氮累积量最大;高产高效模式的土壤硝态氮含量整体水平均低于其他模式,浓度基本维持在30 mg·kg^-1以下,在一定程度上能有效缓解环境压力;冬小麦季0～90 cm土体氮素盈余量均小于夏玉米季,并以高产高效模式的氮素表观损失量最低,显著低于其他模式.综合考虑产量、氮肥利用效率、硝态氮累积和氮平衡,以高产高效模式表现最优,但还有一定的提升空间.