Trade-off between diapause and other life-history traits in the spider mite Tetranychus urticae

1. Diapause is generally believed to entail costs that manifest themselves as decreased survival, rate of development, and/or reproduction after diapause completion. The present study is a first step in investigating such diapause costs in the spider mite Tetranychus urticae.
2. The relationship was assessed between diapause duration and the post-diapause life-history traits of longevity and egg production, under six photoperiods at 19 °C.
3. The relationship between diapause duration and longevity was negative under five out of six treatments; in three cases this negative relationship was significant.
4. Most evident were the negative correlations between diapause duration and rate of oviposition, peak rate of oviposition, and total egg production. These phenotypic correlations suggest that there may be a trade-off between diapause duration and post-diapause reproduction.     

中华通草蛉越冬成虫肠道可培养好氧细菌多样性分析

本研究以昆虫微生态学原理为指导探究中华通草蛉Chrysoperla sinica(Tjeder)的肠道菌群构成,为中华通草蛉的营养生理研究及人工繁殖利用提供理论依据和技术基础。采用无菌解剖及纯培养分离检测技术,从雌、雄成虫肠道环境中分离、纯化、培养,获得10个细菌菌株,对菌体形态、染色反应、培养形状、生理生化反应进行系统研究。结果表明,上述10个菌株分别属于摩根氏菌属(Morganella)、短小芽孢杆菌(Bacillus pumilus)、地杆菌属(Terrabacter)、爱德华氏菌属(Edwardsiella)、色杆菌属(Chromobacterium)、热黄杆菌(Flavobacterium thoupophilum)、放线杆菌属(Actinobacillus)、棍状杆菌属(Clavibacter)、邻单胞菌属(Plesiomonas)、预研菌属(Yokenella);越冬期雌、雄成虫肠道细菌的种类和数量存在较大差异,可能与雌、雄成虫不同的营养和生理需求有关,两者关系还需进一步研究。     

Trade-off between flight and reproduction in the African armyworm moth, Spodoptera exempta

ABSTRACT. The existence of a trade-off between flight and reproduction in the migratory noctuid, Spodoptera exempta (Wlk.), was examined in experiments in which female moths were flown on flight balances and then provided with distilled water or sucrose solution. For individuals flight-tested from the night of eclosion (night 0) through night 1 and fed only distilled water, there was a linear, negative relationship between weight-related fecundity and flight duration. When flight was recorded through night 2, a curvilinear relationship was obtained suggesting that highly active moths suffer a smaller decrease in fecundity than predicted from its rate of decline with increasing flight duration in less persistent fliers. The hypothesis that this reflects an energetically expensive, initial phase of each flight, followed by a less costly, cruising phase is examined. Fecundity was independent of flight duration in females provided with sucrose after flight but was related to moth weight, as it was in all unflown moths. Effects of flight and feeding on longevity and mating frequency are also reported.
There is a clear trade-off between flight and fecundity in S.exempta which is only evident in moths denied access to a source of carbohydrate after flight. The results indicate the importance of nectar sources in the field in allowing restoration of lipid reserves depleted during migratory flight. An important implication of this conclusion is that lipid is the resource limiting to fecundity in this species and not protein as is generally supposed for leaf-feeding insects. This might be expected in highly active species as lipid is the resource for which the energetically expensive functions of flight and reproduction must compete.     

中华通草蛉成虫越冬体色变化与滞育的关系

对自然条件下中华通草蛉成虫越冬体色变化与滞育关系的系统研究表明,成虫在越冬过程中都经历了一个较明显的体色变化过程,主要表现在体躯底色从绿色到土黄色及体背面滞育斑由褐色到红褐色的改变,据此将成虫体色分成5个级别,在越冬过程中约80%个体体色经历了在生殖型体色（1级）和滞育型体色（4,5级）之间的明显变化,约有20%个体体色维持在2、3级,在越冬前,成虫滞育斑出现后其卵巢不再发育或者发育受抑而逐渐停止发育,滞育斑的出现是成虫开始滞育的重要标志;越冬后,随着成虫体色由滞育型向生殖型的转变,当大多数个体体色变为3级以下时,卵巢开始发育,这些结果说明,中华通草蛉越冬成虫体色的变化是其滞育越冬的一个重要形态指标,越冬前后体色的改变,标志着成虫滞育的开始和结束。     

中华通草蛉卵、幼虫和成虫在麦田分布型的研究

研究了中华通草蛉卵、幼虫和成虫在麦田的分布型,均属聚集分布,分析提出适宜的取样调查方法,即双对象线或棋盘式10点,每点调查1m^2麦株。     

光周期和温度对中华通草蛉成虫生殖的影响

研究表明,在25℃和长光周期（L：D＝15：9）条件下饲养至产卵高峰的中华通草蛉成虫,经短光周期（L：D＝9：15）处理后,与长光周期相比,虽然产卵速度有所下降,但产卵期延长,产卵量明显提高;在15℃和短光周期条件下处理后,成虫的生殖受到强烈抑制,产卵速度显下降,部分个体逐渐停止产卵,并进入滞育状态。     

草间钻头蛛、大草蛉和中华通草蛉对茶尺蠖、小绿叶蝉的选择效应

室内研究了草间钻头蛛Hylyphantes graminicola雌蛛对茶尺蠖Ectropis oblique1龄幼虫和小绿叶蝉Em-poesca flavescens成虫、大草蛉Chrysopa pallens和中华通草蛉Chrysoperla sinica的2龄幼虫对茶尺蠖卵、1龄幼虫的选择捕食作用。对试验数据应用Ivelev指数、Jacobs指数和Manly指数及Murdoch作图法进行了比较分析。结果显示,草间钻头蛛对茶尺蠖1龄幼虫和小绿叶蝉成虫的选择性不明显,选择性不因猎物数量的增加而转移。而大草蛉和中华通草蛉对茶尺蠖卵均有明显的正选择效应。     

Trade-off between pre and post-copulatory traits depends on locomotor activity in male Tribolium castaneum beetles

Locomotor performance is an indicator of dynamic exercise; thus, it is a central trait in many animal behaviours. Although higher locomotor endurance may increase male reproductive success (e.g., in mate searching and male–male contests), investment in other male reproductive traits (e.g., male attractiveness and sperm competition) may be decreased through energy consumption due to higher activity levels. Here, I investigated male attractiveness, mating success, and paternity success using males of the red flour beetle Tribolium castaneum selected for higher (H) and lower (L) locomotor endurance. Although there was no difference in male attractiveness between the selection regimes, H males had significantly higher mating success than L males. Conversely, L males had significantly higher paternity success than H males. Therefore, there was a trade-off between mating success and paternity success among the selection regimes, suggesting that locomotor endurance affects male reproduction in T. castaneum, and individual variation of locomotor endurance may be maintained within a population.     

The components of life-history traits variation in Daphnia magna population

The variation of six growth and reproduction traits in the parthenogenetic clones of Daphnia magna and its relationships with the genotypes at 5 isozyme loci were studied under controlled conditions at three food concentrations. A significant genetic component of age at maturity, growth rate and fecundity variation was detected. Nested ANOVA revealed the influences of the genotypes of the isozyme loci, that are more pronounced at the high food concentration. In some cases the genotype-environment interactions were found.The variation of body length at 6 days and total number of offspring includes a significant heterozygosity — environment interaction. The most heterozygous clones show the least differences in life history traits between food conditions.Life-history traits heritability, genotype-environment interactions and different reproductive strategies of the clones are discussed.     

鼠尾藻生长与生殖的权衡

2009年7月初至2009年9月中旬对烟台长岛县望福礁附近水域鼠尾藻(Sargassum thunbergii)进行了生态学调查。实验设立固定采样地点通过随机采样以及现场标记测量的方法观测了鼠尾藻的生长与生殖情况。结果表明:(1)鼠尾藻生殖始于7月初,8月初为高峰期,此间87%的藻体产生生殖托;(2)藻体长度对成熟比例和生殖力均有显著的影响,藻体成熟具有大小依赖性;(3)营养组织生物量大的鼠尾藻群体生殖组织生物量也相对较大,生殖期间营养组织生长和生殖组织生长呈异速关系;(4)成熟藻体在有性生殖高峰期过后,生长率下降,而始终未成熟的藻体则持续生长(生长率0)。以上结果表明,在鼠尾藻的生活史中存在着生长与生殖的权衡。     

Trade-offs between melanisation and life-history traits in Helicoverpa armigera

Abstract.  1. Previously we established a homozygous melanic strain (JBM) with 16 black pupae spontaneously occurring within a laboratory population (JBW) of Helicoverpa armigera and demonstrated that the melanisation is controlled by a single recessive autosomal gene.
2. Data obtained indicate that the melanisation is globally expressed in the pupal and adult stages (except for the body hairs of adults) but not in the egg and larval stages. No differences in body colour can be found between the melanic JBM and the wild-type JBW strains before the metamorphic pupation moult. After pupation, the JBM pupae gradually blacken, whereas the wild-type JBW pupae gradually turn brown, indicating that the biosynthetic steps leading to brown pigments are shut off in the JBM strain. In the adult stage, wings are darker and hairs on the abdomen and tergum are lighter in the melanic moths than in the wild-type individuals.
3. Life-table experiments reveal that the melanism is associated with slower development in all life stages, smaller body weight, lower mating rate and fecundity, less mating time, and accordingly, lower net reproduction rate and population trend index.
4. Single pair inbreeding and reciprocal crosses show that the mating rate is much lower in the inter-strain crosses than in the intra-strain crosses, indicating the presence of mating preference for its own colour morph and the presence to some degree of reproductive isolation between the two colour morphs.     

中华通草蛉自然越冬成虫在两种光周期下滞育解除过程中的生理生化变化

摘要: 光周期在昆虫滞育中起重要作用, 而昆虫光敏感性差异导致了光在昆虫滞育解除过程中作用机制的多样性。为明确光周期在中华通草蛉Chrysoperla sinica (Tjeder)滞育解除过程中的调控机制, 本研究测定了长光周期（15L∶9D）和短光周期（9L∶15D）条件下, 中华通草蛉自然越冬种群成虫在滞育解除过程中的干重、 含水量、 过冷却点（supercooling point, SCP）、 结冰点（freezing point, FP）及蛋白质和糖原含量变化。结果表明： 雌成虫干重在长光照下处理30 d低于短光照下, 其他处理时间的干重均高于短光照下, 但处理间差异不显著（P>0.05）; 雄成虫在长光照下处理5 d的干重高于短光照下, 其余处理时间的干重均低于短光照下, 其中处理30 d 时差异显著（P<0.05）。雌、 雄成虫含水量总体呈上升趋势, 长光照下上升显著（P<0.05）, 短光照下上升不显著（P>0.05）。雌、 雄成虫的SCP、 FP在短光照下处理不同时间均无显著性差异（P>0.05）, 而长光照下表现出先降后升的趋势且处理间差异显著（P<0.05）。成虫蛋白含量在短光照条件下雄虫处理10 d以及雌虫处理15 d均显著低于长光照（P<0.05）, 其他处理之间没有显著性差异。短光照处理成虫体内糖原含量均高于长光照, 且有显著性差异（P<0.05）。多因素方差分析表明, 不同光周期对中华通草蛉成虫滞育解除过程中的SCP、 FP、 糖原变化均有显著性影响（P<0.05）, 而对干重、 含水量及蛋白质含量影响不显著;性别只对成虫FP与糖原有显著影响（P<0.05）; 处理时间对干重、 含水量、 SCP、 FP、 蛋白及糖原含量均有显著影响（P<0.01）。3种因素的交互作用对SCP、 FP、 蛋白及糖原含量均有显著影响, 对干重及含水量影响不显著。初产卵成虫体内物质含量变化测定发现, 长光照（处理10 d）下雌、 雄成虫体内蛋白和糖原含量极显著低于短光照（处理25 d）下（P<0.01）, 雄成虫体内含水量显著高于短光照下（P<0.05）。结果说明, 中华通草蛉自然越冬成虫在长、 短两种光周期下均逐渐解除滞育, 但在滞育解除过程中呈现出不同的生理生化变化。     

Trade-off between egg mass and egg number in brown trout

Individual egg mass and fecundity increased with somatic mass in first time and repeat spawning wild anadromous and freshwater resident brown trout Salmo trutta . The egg mass was larger for similar-sized trout in south (58° N) than mid Norway (63° N), whereas fecundity was higher in mid- than in south Norway, making total gonadal investment similar in the two areas. Repeat spawners had heavier eggs than similar-sized first time spawners. The egg mass of residents was c. 10% larger than that of similar-sized first time spawning anadromous trout. Common garden experiments with offspring of wild anadromous trout showed no significant correlation between egg and somatic mass in first time spawners in two of the three populations studied. In the third population, a slight positive correlation was found. Similar results were found for repeat spawners. In the three populations, fecundity increased significantly with somatic mass in both first time and repeat spawners. Wild and hatchery-reared trout showed negative correlation between egg mass and fecundity when the effect of body size was excluded, indicating a trade-off between the two parameters. In wild trout, this was caused by variation among populations, whereas in hatchery fish, within population variation was observed in egg mass over fecundity. Furthermore, the egg mass of first time and repeat spawners were positively correlated, when adjusted for fish size. Size-specific gonadal investment was significantly higher in wild anadromous than resident trout. There was no significant difference in gonadal investment between first time and repeat spawners in wild anadromous trout. However, in the hatchery-reared trout, gonadal investment was significantly higher at repeat than first time maturation. The hatchery trout did not spawn naturally, but were artificially stripped. Among populations, a part of the variation in egg mass and fecundity is phenotypically plastic, a part appears genetically determined.     

Coevolution between parasite virulence and host life-history traits

Epidemiological models generally explore the evolution of parasite life-history traits, namely, virulence and transmission, against a background of constant host life-history traits. However, life-history models have predicted the evolution of host traits in response to parasitism. The coevolution of host and parasite life-history traits remains largely unexplored. We present an epidemiological model, based on resource allocation theory, that provides an analysis of the coevolution between host reproductive effort and parasite virulence. This model allows for hosts with either a fixed (i.e., genetic) or conditional (i.e., a phenotypically plastic) response to parasitism. It also considers superinfections. We show that parasitism always favors increased allocation to host reproduction, but because of epidemiological feedbacks, the evolutionarily stable host reproductive effort does not always increase with parasite virulence. Superinfection drives the evolution of parasite virulence and acts on the evolution of the host through parasite evolution, generally leading to higher host reproductive effort. Coevolution, as opposed to cases where only one of the antagonists evolves, may generate correlations between host and parasite life-history traits across environmental gradients affecting the fecundity or the survival of the host. Our results provide a theoretical framework against which experimental coevolution outcomes or field observations can be contrasted.     

The life-history trade-off between fertility and child survival

Evolutionary models of human reproduction argue that variation in fertility can be understood as the local optimization of a life-history trade-off between offspring quantity and ‘quality’. Child survival is a fundamental dimension of quality in these models as early-life mortality represents a crucial selective bottleneck in human evolution. This perspective is well-rehearsed, but current literature presents mixed evidence for a trade-off between fertility and child survival, and little empirical ground to evaluate how socioecological and individual characteristics influence the benefits of fertility limitation. By compiling demographic survey data, we demonstrate robust negative relationships between fertility and child survival across 27 sub-Saharan African countries. Our analyses suggest this relationship is primarily accounted for by offspring competition for parental investment, rather than by reverse causal mechanisms. We also find that the trade-off increases in relative magnitude as national mortality declines and maternal somatic (height) and extrasomatic (education) capital increase. This supports the idea that socioeconomic development, and associated reductions in extrinsic child mortality, favour reduced fertility by increasing the relative returns to parental investment. Observed fertility, however, falls considerably short of predicted optima for maximizing total offspring survivorship, strongly suggesting that additional unmeasured costs of reproduction ultimately constrain the evolution of human family size.     

Changes in amino acids in Cucumis melo in relation to life-history traits and flight propensity of Bemisia tabaci

Phloem amino acids in Cucumis melo L. were measured to determine whether changes in nitrogen availability might affect life-history traits and flight activity of Bemisia tabaci Gennadius (Homoptera: Aleyrodidae). During plant development, nineteen of the twenty common amino acids, plus hydroxyproline, citrulline, ornithine and -aminobutyric acid (GABA) were identified. For most essential amino acids, there were two peaks observed: an initial large peak associated with young plants, and a later small peak associated with senescing plants. For histidine, ornithine and citrulline, medium to large peaks in relative abundance were observed in mature plants. Arginine peaked during the first few weeks of development and was no longer detectable after wk 7. Serine and glutamine/glutamic acid were the only amino acids that peaked during plant senescence. Factor analysis was used to create a reduced number of orthogonal factors, which corresponded well with the trends that were observed for the various groups of amino acids. No single or combination of factors explained a significant amount of the variability in oviposition. For both males and females, factor 1 (predominantly essential amino acids) was the single most important predictor of adult weight. As the relative concentrations of essential amino acids decreased, whitefly weights decreased. Factors 1 and 3 (predominantly histidine and ornithine) were the most important predictors of developmental time. As these amino acids decreased in relative concentration, developmental time increased. Percent emergence was positively associated with factor 1 and negatively associated with factor 6 (predominantly aspartic acid). The distributions of flight duration for whiteflies emerging from young, mature and senescing melon plants were compared and they were always skewed towards short flights; however, the frequency of long-duration flights increased when melon plants began to senesce. Whiteflies from all plant-age categories were capable of flying for more than 2 h with fully developed eggs, but the presence of more than four mature eggs was associated with flights of reduced duration.     

马桑结瘤固氮与光合作用的关系

马桑(Coriaria sinica)植株的结瘤量、根瘤固氮活性和固氮能力均与植株叶面积和光合能力呈显著的直线相关关系,叶面积大、光合能力强的植株结瘤量大,根瘤固氮活性高,固氮能力强。马桑根瘤固氮活性呈白天升高夜间降低的昼夜变化特点,昼夜变幅为10～20μmol C2H2/g.h,光合作用是引起固氮活性昼夜变化的主要因素,同时受土壤温湿度的影响,遮阴或光照不足将引起马桑结瘤固氮能力的大幅度降低。