Does Reproduction Shorten Telomeres? Towards Integrating Individual Quality with Life‐History Strategies in Telomere Biology

Reproduction, a basic property of biological life, entails costs for an organism, ultimately detectable as reduction in survival prospects. Telomeres are an excellent candidate biomarker for explaining these reproductive costs, because their shortening correlates with increased mortality risk. For similar reasons, telomeres are perceived as biomarkers of individual “quality.” The relationship between reproduction and telomere dynamics is reviewed, emphasizing that cost and quality perspectives, commonly presented in isolation, should be integrated. While a majority of correlative studies have confirmed the relationship between telomere dynamics and various reproductive outputs, only limited experimental support exists showing that reproduction causes telomeres to shorten. A shift of focus to experimental manipulations of reproductive effort/telomere dynamics is crucial. However, the observation of survival reduction in response to these manipulations is essential for establishing telomeres as genuine biomarkers, allowing to unravel trade‐offs related to reproduction.     

The Development of Chloroplast Structure During Leaf Ontogeny

Advances achieved during last fifteen years in the understanding the development of chloroplast ultrastructure during natural leaf ontogeny are summarized. Life span of a typical C3 mesophyll cell chloroplast is outlined and placed into the scheme of cyclic plastid interrelationships. Possible modifications of this development by stresses, environmental factors or experimental treatments are also shown.     

Phenotypic selection on morphology at independence in the Chinstrap penguin Pygoscelis antarctica

Every year, shortly after the emancipation of chicks at our study colony (Deception Island, South Shetlands), hundreds of carcasses of presumably starved Chinstrap penguin Pygoscelis antarctica chicks are washed on the shore. In 1997 we measured the flippers of fresh carcasses and compared their lengths with those of live chicks about to become independent. There was a highly significant difference of 6.5 mm between both distributions, which suggests strong directional phenotypic selection on skeletal size operating through its association with body reserves at independence. Given that heritabilities of flipper length and body weight measured on 36 families are 0.73(± 0.32) and 0.075(± 0.081), and that both characters show a genetic correlation of 0.44(± 0.14), we can expect an evolutionary response to this selection episode. Assuming that the target of selection is weight at emancipation (heavier chicks carry proportionally larger reserves), and that flipper length changes as a consequence of its genetic correlation with weight, we can predict a response of 1.32–2.87 mm or 0.23–0.51 standard deviation units for flipper length. This substantial evolutionary response may be countered by other selective pressures affecting other life stages of these birds. Selection on reserve storage capacity at independence may affect morphological traits also in other species.     

不同温度下斜纹夜蛾的两性生命表

【目的】斜纹夜蛾Spodoptera litura(Fabricius)是一种鳞翅目夜蛾科食叶害虫,在不同的寄主、饲料等条件下表现出不同的生长发育特点。本实验旨在探究温度对斜纹夜蛾生长发育状况和种群参数的影响。【方法】在室内人工气候箱20±1℃,27±1℃和30±1℃(相对湿度和光周期分别为65%±10%和14L∶10D)条件下饲养斜纹夜蛾,观察和组建斜纹夜蛾在3种温度下的年龄-阶段两性生命表。【结果】斜纹夜蛾各个阶段的发育历期随温度升高变短,成虫产卵前期(adult preoviposition period,APOP)和总产卵前期(total preoviposition period,TPOP)同样表现为随温度升高而变短。此外,20±1℃处理的平均产卵量最高(1 810.36粒/雌),27±1℃处理次之(1 623.51粒/雌),30±1℃处理最低(1 084.60粒/雌)。斜纹夜蛾在不同温度条件下内禀增长率(r)、周限增长率(λ)和净增殖率(R0)有显著差异,20±1℃处理的r和λ显著低于27±1℃处理和30±1℃处理;27±1℃处理的R0显著大于20±1℃和30±1℃处理;20±1℃,27±1℃和30±1℃下平均世代周期(T)分别为52.51,30.63和26.87 d,依次减少且相互间差异显著(P0.05)。【结论】斜纹夜蛾在27±1℃和30±1℃温度条件下均表现出很强的增殖能力,该结果可为田间综合防治斜纹夜蛾提供理论依据。     

Maternal warming affects early life stages of an invasive thistle

Maternal environment can influence plant offspring performance. Understanding maternal environmental effects will help to bridge a key gap in the knowledge of plant life cycles, and provide important insights for species’ responses under climate change. Here we show that maternal warming significantly affected the early life stages of an invasive thistle, Carduus nutans. Seeds produced by plants grown in warmed conditions had higher germination percentages and shorter mean germination times than those produced by plants under ambient conditions; this difference was most evident at suboptimal germination temperatures. Subsequent seedling emergence was also faster with maternal warming, with no cost to seedling emergence percentage and seedling growth. Our results suggest that maternal warming may accelerate the life cycle of this species via enhanced early life‐history stages. These maternal effects on offspring performance, together with the positive responses of the maternal generation, may exacerbate invasions of this species under climate change.     

短季棉早熟性的遗传效应及其与环境互作研究

以熟期不同的9个棉花品种为亲本,按部分双列杂交配制46个组合的F1、F2,在3个不同生态环境条件下,研究了7个早熟相关性状的遗传效应及其与环境互作。结果表明:短季棉7个早熟相关性状的遗传均以加性效应为主,同时存在着显性效应,对于播种-现蕾、播种-开花和现蕾-开花还存在着上位性效应;短季棉各早熟性状的遗传效应与环境互作显著。生育期、播种-开花的狭义遗传率均较高,分别为66.1%和49.1%,且与环境互作效应较小,而果枝始节和播种-现蕾的遗传率最低,分别为19.8%和18.8%,且与环境互作达到极显著水平,现蕾-开花、开花-吐絮和株高这3个性状的遗传率及其与环境互作居中。由此说明:早熟性的遗传受环境影响较大,在生态条件差异较大的育种地点,以果枝始节和播种-现蕾作为早熟性指标进行异地选择是不可靠的,而以生育期、开花期为早熟性选择指标是比较可行的。     

Growth and reproduction of three cladoceran species from a small wetland in the south-eastern U.S.A.

SUMMARY 1. Growth, reproduction and life‐history parameters were measured for three cladoceran species from a small south‐eastern wetland, U.S.A. Simocephalus serrulatus, Diaphanosoma brachyurum and Scapholeberis mucronata juveniles were reared at temperatures between 10 and 25 °C on natural food resources. 2. Growth rate increased with temperature and decreased with individual size for all three species. Maximum somatic growth rate was higher for Simocephalus (49–72% day^?1) and Diaphanosoma (21–91% day^?1) than for Scapholeberis (11–45% day^?1). Multiple regression equations were developed which predict temperature‐ and mass‐specific growth rates for each species. 3. Scapholeberis egg production was positively related to temperature; however, maximum egg production occurred at intermediate temperatures for Simocephalus and Diaphanosoma. Mean cumulative egg production was higher for Scapholeberis (28–92 eggs per female) than for Simocephalus (18–25 eggs per female) and Diaphanosoma (1–41 eggs per female), and was related to differences in reproductive strategy and survival. 4. Survival was inversely related to temperature in most cases. For all three cladocerans, the intrinsic rate of increase (r) and net reproductive rate (R₀) increased with temperature, whereas generation time (G) decreased. Greater egg production by Scapholeberis compared with the other two cladocerans was consistent with higher R₀ values for Scapholeberis at any given temperature. Although r was very similar among species, G was typically longer for Scapholeberis than for Simocephalus and Diaphanosoma. 5. This analysis provides basic information about the population parameters of these coexisting wetland species, and the growth rate models can be applied to field data to determine production dynamics.     

Life history buffering in Antarctic mammals and birds against changing patterns of climate and environmental variation

The consequences of warming for Antarctic long‐lived organisms depend on their ability to survive changing patterns of climate and environmental variation. Among birds and mammals of different Antarctic regions, including emperor penguins, snow petrels, southern fulmars, Antarctic fur seals and Weddell seals, we found strong support for selection of life history traits that reduce interannual variation in fitness. These species maximize fitness by keeping a low interannual variance in the survival of adults and in their propensity to breed annually, which are the vital rates that influence most the variability in population growth rate (λ). All these species have been able to buffer these rates against the effects of recent climate‐driven habitat changes except for Antarctic fur seals, in the Southwest Atlantic. In this region of the Southern Ocean, the rapid increase in ecosystem fluctuation, associated with increasing climate variability observed since 1990, has limited and rendered less predictable the main fur seal food supply, Antarctic krill. This has increased the fitness costs of breeding for females, causing significant short‐term changes in population structure through mortality and low breeding output. Changes occur now with a frequency higher than the mean female fur seal generation time, and therefore are likely to limit their adaptive response. Fur seals are more likely to rely on phenotypic plasticity to cope with short‐term changes in order to maximize individual fitness. With more frequent extreme climatic events driving more frequent ecosystem fluctuation, the repercussions for life histories in many Antarctic birds and mammals are likely to increase, particularly at regional scales. In species with less flexible life histories that are more constrained by fluctuation in their critical habitats, like sea‐ice, this may cause demographic changes, population compensation and changes in distribution, as already observed in penguin species living in the Antarctic Peninsula and adjacent islands.     

视蛋白基因LW-opsin突变影响小菜蛾的生长发育和繁殖能力

【目的】小菜蛾Plutella xylostella是世界性的十字花科蔬菜害虫。本研究旨在明确视蛋白基因LW-opsin突变对小菜蛾生长发育和繁殖能力的影响;为开发小菜蛾遗传防控新靶标提供理论依据。【方法】实验室条件下;利用年龄-龄期两性生命表测定小菜蛾野生型品系G88和LW-opsin突变品系LW-13的发育历期、存活率、繁殖力、生命期望值和生命表参数。【结果】LW-opsin突变延长了小菜蛾成虫前历期［G88: (12.45±0.06) d; LW-13: (13.45±0.25) d］和总产卵前期［G88: (12.59±0.08) d; LW-13: (13.57±0.30) d］;缩短了成虫寿命［G88: (6.84±0.02) d; LW-13: (5.73±0.07) d］和产卵期［G88: (6.09±0.10) d; LW-13: (5.14±0.34) d］。LW-opsin突变降低了小菜蛾幼虫、蛹和成虫的存活率。G88品系种群特定年龄存活率从18日龄起开始急剧下降; LW-13品系种群特定年龄存活率则在4日龄时已降至25%。LW-opsin突变降低了种群特定年龄繁殖值、特定年龄-龄期生命期望值、内禀增长率［G88: (0.31±0.01) d^-1; LW-13: (0.15±0.03) d^-1］、周限增长率［G88: (1.36±0.01) d-1; LW-13: (1.16±0.03) d^-1］和净增殖率(G88: 79.79±8.84; LW-13: 10.26±3.84);延长了平均世代周期［G88: (14.20±0.06) d; LW-13: (15.67±0.16) d］。【结论】视蛋白基因LW-opsin突变影响小菜蛾的生长发育;降低其存活率和繁殖能力。     

Influence of the filamentous cyanobacterium Planktothrix agardhii on population growth and reproductive pattern of the rotifer Brachionus calyciflorus

The population dynamics of B. calyciflorus was investigated using a green alga, Monoraphidium minutum, and a blue-green alga Planktothrix agardhii as food sources, separately and as mixtures. Growth rate (r), egg ratio (ER), and juvenile development time (D _j ) were measured in the laboratory and mortality rate and embryonic development time (D _E ) were calculated. With M. minutum, Brachionus showed a typical growth curve (Monod-kinetics) dependent on food concentration. In contrast B. calyciflorus did not grow well on P. agardhii. With all food concentrations the measured growth rates were about r=0. At low food concentrations r was low with both food types, but the ER of B. calyciflorus was significantly higher with P. agardhii as food source. Furthermore the relative egg volume of females carrying one egg was higher with Planktothrix than with Monoraphidium. An addition of P. agardhii to M. minutum led to increasing growth rates. Highest growth rates were found with complementary food sources. High food concentrations of M. minutum shortened the juvenile development (D _J ) time, but D _j was uneffected by different P. agardhii food concentrations. A mixture of both algae did not shorten D _j compared with M. minutum as single food. The calculated D _E was not effected by different food qualities but the calculated mortality was nearly 3 times higher with P. agardhii as food.