Kin selection and the evolution of monogamy

A two-locus genetic model is studied in which one locus controls the tendency of individuals to act altruistically toward siblings and the other locus controls the mating habits of females. It is demonstrated that genetic variation at the altruism locus is often sufficient to induce an increase in the frequency of genes that cause females to produce all of their offspring with a single mate. This occurs because of nonrandom associations that develop between genes that cause altruism and those that affect female mating behavior. The results provide a new explanation for the evolution of monogamy, and they suggest a previously unexplored mechanism for the evolution of a variety of other behavioral traits as well.     

Natural selection and developmental constraints in the evolution of allometries

In animals, scaling relationships between appendages and body size exhibit high interspecific variation but low intraspecific variation. This pattern could result from natural selection for specific allometries or from developmental constraints on patterns of differential growth. We performed artificial selection on the allometry between forewing area and body size in a butterfly to test for developmental constraints, and then used the resultant increased range of phenotypic variation to quantify natural selection on the scaling relationship. Our results show that the short-term evolution of allometries is not limited by developmental constraints. Instead, scaling relationships are shaped by strong natural selection.     

Directional selection and the evolution of breeding date in birds

In many bird species, those pairs that breed earlier in the season have higher reproductive success than those that breed later. Since breeding date is known to be heritable, it is unclear why it does not evolve to an earlier time. Under assumptions outlined by Fisher, a model is developed that shows how breeding date may have considerable additive genetic variance, appear to be under directional selection, and yet not evolve. These results provide a general explanation for a persistent correlation of fitness with a variety of traits in natural populations.     

Ecological context influences epidemic size and parasite-driven evolution

The occurrence and magnitude of disease outbreaks can strongly influence host evolution. In particular, when hosts face a resistance-fecundity trade-off, they might evolve increased resistance to infection during larger epidemics but increased susceptibility during smaller ones. We tested this theoretical prediction by using a zooplankton-yeast host-parasite system in which ecological factors determine epidemic size. Lakes with high productivity and low predation pressure had large yeast epidemics; during these outbreaks, hosts became more resistant to infection. However, with low productivity and high predation, epidemics remained small and hosts evolved increased susceptibility. Thus, by modulating disease outbreaks, ecological context (productivity and predation) shaped host evolution during epidemics. Consequently, anthropogenic alteration of productivity and predation might strongly influence both ecological and evolutionary outcomes of disease.     

Ancestral monogamy shows kin selection is key to the evolution of eusociality

Close relatedness has long been considered crucial to the evolution of eusociality. However, it has recently been suggested that close relatedness may be a consequence, rather than a cause, of eusociality. We tested this idea with a comparative analysis of female mating frequencies in 267 species of eusocial bees, wasps, and ants. We found that mating with a single male, which maximizes relatedness, is ancestral for all eight independent eusocial lineages that we investigated. Mating with multiple males is always derived. Furthermore, we found that high polyandry (>2 effective mates) occurs only in lineages whose workers have lost reproductive totipotency. These results provide the first evidence that monogamy was critical in the evolution of eusociality, strongly supporting the prediction of inclusive fitness theory.     

酶定向进化文库的筛选方法

酶工程作为生物技术的主体之一,对农产品加工等的发展具有广泛作用。自然界中的酶往往不能满足 实际生产,因此需要通过模拟自然界中的蛋白质进化,对酶进行改造和突变文库筛选,最终得到符合实际生产的酶。 目前,改造酶的途径主要有定点突变和定向突变两种。突变体文库的建立方法较为成熟,并且建立起的文库库容也 能够达到研究者的要求,但是突变体文库的筛选受现有技术等所局限,成为了定向进化技术的瓶颈。介绍了几种常 用的突变体文库的筛选方法,对它们的原理及特点进行阐述,并对未来的发展方向及趋势进行了总结。     

Plant chemistry and the evolution of host specificity: new evidence from heliconius and passiflora

Larval growth rates of Heliconius butterflies do not closely parallel host plant choice, an indication that factors other than host plant chemistry are important in evolving host specificity. High growth rate in one species is correlated with reduction in number of palatable host species. This suggests a mechanism by which ecologically restricted species become progressively biochemically specialized.     

气候变化背景下舟山沿岸上升流区夏季水动力演变机制

全球变暖会对舟山沿岸上升流的驱动机制产生深远影响,继而作用于海域内的生态环境及渔业资源发生的变迁。使用三维海洋数值模型FVCOM,模拟研究了热通量、风场等气候环境因子变化下舟山沿岸上升流区夏季水动力及环境因子的分布特征。通过引入跃变检验方法来评估全球变暖对过去三十多年来舟山及其邻近海域的夏季海表温度的影响,发现在2016年前后发生了明显的跃变,跃变后海表温度相对于跃变前升高了约1 °C;热通量分析结果显示春季云量减小,短波辐射增加导致的海水热含量增加是夏季海水升温的重要原因;风速的时空变化表明舟山海域7月风速在近几十年有减弱的趋势。通过构建气候环境因子变化的敏感性数值模型实验探究了舟山沿岸上升流水动力的演变机制,结果表明海气热通量增加导致的表层海水吸热及平流热输运增加引起的海水层化加强会使得底层海水不易抬升;夏季风应力的减弱削弱了长江冲淡水低盐水舌的离岸扩展,导致上升流区上层海水的层化减弱,从而加强中下层海水向岸爬升,增加沿岸上升流的强度。     

桃蚜的抗性选育及其两种解毒酶活性研究

于室内对桃蚜进行高效氯氰菊酯抗药性筛选，选育至10代后抗性倍数增长到49．86倍。生化分析表明，抗性品系酯酶(Est)、谷胱甘肽S-转移酶(GSTs)活性均显著高于敏感品系。比较两个品系酯酶与谷胱甘肽-S-转移酶活性个体频率分布发现，抗性品系的桃蚜有更多的个体向酶活性高的区域分布。酶动力学测定结果显示，抗性桃蚜酯酶对底物α-NA的Km和Vmax都显著大于敏感品系；而谷胱甘肽S-转移酶对底物DTNB的Km则显著小于敏感品系，但两个品系的Vmax差异不显著。酯酶同工酶电泳表明，与敏感品系相比，抗性品系缺失E3酶带，但其酯酶同工酶染色较深。     

Mate selection and the evolution of highly polymorphic self/nonself recognition genes

Multicellular organisms use the products of highly polymorphic genes to distinguish self from conspecific nonself cells or tissues. These allorecognition polymorphisms may regulate somatic interactions between hosts and pathogens or between competitors (to avoid various forms of parasitism), as well as reproductive interactions between mates or between gametes (to avoid inbreeding). In both cases, rare alleles may be advantageous, but it remains unclear which mechanism maintains the genetic polymorphism for specificity in self/nonself recognition. Contrary to earlier reports, we show that mate selection cannot be a strong force maintaining allorecognition polymorphism in two colonial marine invertebrates. Instead, the regulation of intraspecific competitive interactions appears to promote the evolution of polymorphisms in these species.     

番石榴实蝇对阿维菌素的抗性选育及解毒酶活力变化

为了解阿维菌素对番石榴实蝇[Bactrocera correcta(Bezzi)]解毒酶及抗性的变化,在室内测定了不同增效剂对阿维菌素的影响及解毒酶活性。结果表明:药剂连续选育15代后,种群抗性倍数达到8.17。3种增效剂对敏感、抗性种群均有一定的增效作用,其中抗性种群中增效醚(PBO)、磷酸三苯酯(TPP)的增效作用显著,增效倍数分别为2.34、1.94。3种解毒酶的测定表明阿维菌素对多功能氧化酶(MFO)、羧酸酯酶(CarE)有显著提升作用,说明MFO、CarE的增强可能是番石榴实蝇对阿维菌素产生抗性的主要原因。     

Comment on "Positive selection of tyrosine loss in metazoan evolution"

Tan et al. (Reports, 25 September 2009, p. 1686) argued that loss of tyrosine residues from proteins in metazoans was driven by positive selection to remove potentially deleterious phosphorylation sites. We challenge this hypothesis, providing evidence that the high guanine-cytosine (GC) content of metazoan genomes was the primary driver in the loss of tyrosine residues.     

生计转型背景下蒙古族生态移民非农生计策略选择及困境分析

利用内蒙古包头市7个牧区生态移民安置区的移民调查数据,采用生态移民认知和统计描述等方法实证分析牧区生态移民非农生计策略选择及困境问题。研究表明:生态移民以从事临时性无手艺打工为主要非农生计策略,而女性以及以小学和初中文化程度为主的生态移民选择失业的比重比较高;生态移民非农生计策略选择重点依赖于自己;在非农生计策略选择中往往会遇到工资少、缺技术、打工机会、知识缺乏、资金短缺、社会关系缺乏、语言沟通困难、缺乏带头人以及缺乏企业等困难。笔者认为,为提高生态移民在非自愿迁移背景下非农生计策略的转型能力,应该建立移民非农就业机构,根据生态移民性别、教育程度以及劳动能力,采取适合的产业选择、二三产业就业培训、安置区内外转移相结合方式以及当地特色农畜产品加工产业链条延长等措施,实现生计转型背景下的生态移民可持续发展。     

现代农业三大体系建设背景下上海农业产业体系演变动因研究

在乡村振兴与构建现代农业产业体系、生产体系和经营体系三大体系的背景下,对上海农业产业体系演变动因进行研究,旨在指导上海都市现代农业产业体系的构建,帮助中国其他地区构建现代农业产业体系。首先研究了农业产业体系演变动因机制,得出农业产业体系的演变动因包括制度引导、需求拉动、资源诱导和科技推动4个方面;其次研究了上海农业产业体系的演变,将其演变划分为乡村型农业产业体系、城郊型农业产业体系、都市型农业产业体系和都市现代农业产业体系4个时期,利用1995—2017年第一产业增加值占生产总值比例、上海农村居民人均可支配收入、粮经产量比和种养产量比4项指标的面板数据,采用LSD法对阶段划定进行异质性检验,检验结果具有统计学意义;最后分析了上海农业产业体系各个阶段的演变动因,揭示了上海农业产业体系的演变历程。研究发现,上海农业产业体系演变动因和上海的城市定位对农业的功能诉求有极大关系,不同阶段的农业产业体系实现不同的农业主导功能,现阶段上海构建都市现代农业产业体系应以实现农业的生态功能为目标。     

情景语境在英语词汇教学中的运用

情景语境制约词语意义的理解,情景语境的差异必然导致词汇特定内涵的不同。英语词汇教学必须和一定的情景语境结合起来,充分考虑特定词背后能影响词义的各种情景因素,使该词在一定语境中的确切含义得以定位。