线粒体ND4-ND4L基因在黑腹果蝇种组中的进化特征

本实验对黑腹果蝇种组(melanogaster species group)中8个种亚组33个样品两个线粒体基因ND4和ND4L进行了测序,并分析了ND4基因的序列差异和碱基替换特点,发现近缘物种中存在很明显的转换倾向,而在远缘物种中由于重复替换导致转换数处于饱和状态,我们的实验数据证实了线粒体基因较核基因有较快的进化速度.最后根据D.melanogaster与D.yakuba的遗传距离推算了8个种亚组的分化时间,ananassae种亚组最先分化,然后依次是montium,melanogaster,ficsphia,eugracilis,elegans,suzukii和takahashii最后分化.     

黑腹果蝇种组的核型与进化研究

观察了国内黑腹果蝇种组34种果蝇的有丝分裂中期核型,其中首次描述了一些新核型。系统地分析了黑腹果蝇种组8个种亚组之间的核型进化关系及种间亲缘关系。结果是:elegans种亚组的核型为A型;eugracilis、melanogaster和ficusphila种亚组的核型为C型;takahashii和suzukii种亚组的核型为C型和D型;montium种亚组的核型为B、C、C’、D、D’、和E型;ananassae种亚组的核型为F、G和H型。从核型分化的角度可以将黑腹果蝇种组分为5个谱系:elegans,eugracilis-melanogaster-ficusphila,takkahashii-suzukii,montium,ananassae。这与2004年Yang等的观点基本一致,正好从核型进化的角度验证了Yang通过DNA序列分析所得到的结果。差别只在于elegans种亚组,作者把它单独列为一支,认为是祖先种亚组。通过选取同一种果蝇的几个不同地域单雌系的核型分析,结果表明:同一种果蝇的核型存在地域差异。这种差异可能是由于不同生境造成,也可能是本身进化程度的差异,或是两种因素相互作用的结果。     

线粒体ND4-ND4L基因在黑腹果蝇种组中的进化特征

本实验对黑腹果蝇种组(melanogaster species group)中8个种亚组33个样品两个线粒体基因ND4和ND4L进行了测序,并分析了ND4基因的序列差异和碱基替换特点,发现近缘物种中存在很明显的转换倾向,而在远缘物种中由于重复替换导致转换数处于饱和状态,我们的实验数据证实了线粒体基因较核基因有较快的进化速度。最后根据D．melanogaster与D．yakuba的遗传距离推算了8个种亚组的分化时间,ananassae种亚组最先分化,然后依次是montium,melanogaster,ficsphila,eugracilis,elegans,suzukii和takahashii最后分化。     

以ND4L和ND4基因为标记探讨黑腹果蝇种组的系统发育关系

多年来的形态学、染色体组学以及DNA序列几个方面的研究均没有很好地阐明黑腹果蝇种组内的系统发育关系。本实验测定了33个样品的ND4和31个样品的ND4L基因序列,以D．obscuroides为外群,用最大简约法和Bayesian法分别构建进化树。结果表明两种方法构建的拓扑结构一致,而且大部分支系的支持率较高。整个黑腹果蝇种组分成三大谱系：1）montium种亚组;2）ananssae种亚组;3）Oriental种亚组（melanogaster、ficsphila、eugracilis、elegans、suzukii、takahashii）。montium是最早分化的种亚组。在第三谱系中,melanogaster分化得最早;然后依次是ficsphila,eugracilis,elegans;suzukii与takahashii为姐妹种亚组,最后分化。     

高桥氏果蝇表型频率变化和胁迫相关性状的分析:季节性适应研究

[目的]昆虫中经常可见体色变化,但是关于其作用价值了解甚少.高桥氏果蝇Drosophila takahashii在遗传上表现出腹部黑化的不连续变化.为了测定生理性状是否可能受黑化的影响,我们调查了3个不同色型个体腹部黑化的变化和胁迫相关性状,检验了季节性环境条件将增强相应的季节性表型的适应性这一假说.[方法]从不同海拔地点采集高桥氏果蝇,对深色和浅色纯育品系的遗传杂交进行的孟德尔分析证实存在一个主要位点,为D等位基因显性.对种群以及3种色型果蝇的生理生态学性状进行了统计分析.[结果]在旱季观察到深色等位基因频率的显著增加,在雨季会出现体色较浅的果蝇,这说明气候选择起着重要作用.不过,在这两个季节中体色居中的果蝇均很多.中间色型的果蝇由于适应而表现出所有性状的F值均显著增加(P ＜0.001),但在深色和浅色纯育品系中未观察到这类适应效果(P≥0.42).[结论]通过不同性状的测定结果我们提出,在干冷胁迫条件下,在深色型中观察到显著更高的生理学耐性;而在湿热条件下,在浅色型中观察到显著更高的生理学耐性.有意思的是,中间表型在这两种条件下均有较强的适应能力.而且,我们发现温湿度的季节性改变给胁迫相关的性状施加了选择压力.     

我国三地区黑腹果蝇中Wolbachia的系统发育关系及其对宿主生殖的影响

【目的】Wolbachia 是广泛存在于节肢动物和丝状线虫体内的一类共生菌, 能够以多种方式对宿主产生影响。精卵细胞质不亲和（CI）是其引起的最普遍的表型, 即感染Wolbachia的雄性宿主与未感染或感染不同品系的雌性宿主交配后, 不能产生后代或后代极少, 而感染同品系Wolbachia的雌雄宿主交配后则能正常产生后代。我们前期研究发现, 湖北武汉、 云南六库和天津3个地区黑腹果蝇Drosophila melanogaster被Wolbachia感染。本研究旨在明确这3个地区黑腹果蝇中Wolbachia的系统发育关系及其对宿主生殖的影响。【方法】利用Clustal X软件对Wolbachia的wsp基因序列进行比对, 利用MEGA软件构建系统发育树。采用多位点序列分型（MLST）的方法对Wolbachia进行分型。通过区内交配和区之间杂交的方式研究不同地区黑腹果蝇体内Wolbachia 的关系及其对果蝇生殖的影响。【结果】湖北武汉、 云南六库和天津3个地区黑腹果蝇中感染的Wolbachia都是属于A大组的Mel亚群。这3个地区果蝇感染的Wolbachia的序列类型（ST）不同, Wolbachia之间存在一定的差异。湖北武汉和天津果蝇中的Wolbachia能引起强烈的CI表型, 而云南六库果蝇中的Wolbachia引起的CI强度相对较弱。武汉果蝇中Wolbachia不能完全挽救天津果蝇中Wolbachia引起的CI表型, 而天津果蝇中Wolbachia也不能完全挽救武汉果蝇中Wolbachia引起的CI表型。【结论】武汉和天津地区黑腹果蝇中的Wolbachia可能距离较远。Wolbachia的长期共生可能对黑腹果蝇的进化产生了一定的影响, 湖北武汉与云南六库的黑腹果蝇中感染的Wolbachia属于不同的序列类型, 这2个地区的黑腹果蝇已发生了一定的分歧, 产生了一定的生殖隔离。     

中国东北地区黑腹果蝇(Drosophila melanogaster)P因子分布和来源

真核生物的转座因子(transposable elements)特别是果蝇P因子在研究生物进化上有重要的意义。以我国东北地区13个地方及毗邻的北京、烟台和呼和浩特三个地方共130个黑腹果蝇(D.melanogaster)单雌系为材料,对P因子序列的ORF2-ORF3区段进行PCR扩增,统计不同地方黑腹果蝇群体的P因子在此区段的缺失频率,再从整个地区来分析P因子缺失的分布规律,以推导东北地区黑腹果蝇中P因子的传递和扩散途径。结果显示P因子缺失频率由边境地区向内地逐渐递减,群体相对隔离的地方也较低,推断我国东北地区黑腹果蝇中P因子由朝鲜和俄罗斯向中国边境入侵后,逐步向中国内地扩散。     

布拉迪小环腹瘿蜂的生物学特性及其寄生对黑腹果蝇生长发育的影响

【目的】调查布拉迪小环腹瘿蜂Leptopilina boulardi的生物学特性,明确该寄生蜂寄生对寄主黑腹果蝇Drosophila melanogaster生长发育的影响。【方法】运用形态成像和统计学的方法,对布拉迪小环腹瘿蜂的发育历期和寄生效率等生物学特性进行研究,同时对布拉迪小环腹瘿蜂寄生后寄主黑腹果蝇发育历期以及蛹期体长和体重的变化进行统计分析。【结果】布拉迪小环腹瘿蜂的卵期平均为0. 98±0. 22 d,幼虫期为10. 22±0. 57 d,雄虫蛹期为8. 09±0. 19 d,雌虫蛹期10. 07±0. 30 d,雌蜂平均比雄蜂约晚2 d羽化。布拉迪小环腹瘿蜂寄生黑腹果蝇2龄幼虫后,黑腹果蝇幼虫出现明显的黑化包囊反应,幼虫发育显著延缓,蛹长和蛹重也显著降低。【结论】布拉迪小环腹瘿蜂是黑腹果蝇的专性寄生蜂。本研究的结果为寄生蜂调控寄主的机制提供了实验依据。     

中国东北地区黑腹果蝇（Drosophila melanogaster）P因子分布和来源

真核生物的转座因子(transposable elements)特别是果蝇P因子在研究生物进化上有重要的意义。以我国东北地区13个地方及毗邻的北京、烟台和呼和浩特三个地方共130个黑腹果蝇(D.melanogaster)单雌系为材料,对P因子序列的ORF2-ORF3区段进行PCR扩增,统计不同地方黑腹果蝇群体的P因子在此区段的缺失频率,再从整个地区来分析P因子缺失的分布规律,以推导东北地区黑腹果蝇中P因子的传递和扩散途径。结果显示P因子缺失频率由边境地区向内地逐渐递减,群体相对隔离的地方也较低,推断我国东北地区黑腹果蝇中P因子由朝鲜和俄罗斯向中国边境入侵后,逐步向中国内地扩散。     

三黄果蝇(Drosophila trilutea)近黄果蝇(D.paralutea)的有丝分裂中期染色体

这两种果蝇隶属果蝇科 Drosophilidae 果蝇属 Drosophila (Sophophora) 黑腹果蝇 D.melanogaster 种组(species group)中的D.takahashii 亚组(subgroup)。Bock和Wheeler(1972)在报道新种的文献中,曾记述其有丝分裂中期染色体的形态结构为2对中着丝粒(V形),1对棒状(R)。其中X染色体为棒状,Y染色体稍短。据此,其二倍体染色体数目推测为2n=6。我们观察的结果则与之显然不同。     

Climate warming mediates range shift of two differentially adapted stenothermal Drosophila species in the Western Himalayas

The average temperature of the earth has increased from 0.3 to 0.6 °C, and warming is facilitating faunal reshuffling. Variable thermal environments warrant mechanisms to adjust the expression of phenotypic values to environmental needs. Ectothermic Drosophilids are profoundly affected by thermal selection (i.e., genetic effects) or through induced effects on phenotypes (i.e., plastic effects). Climatic data for the last fifty years involves a significant change in average temperature (T_ave) of Western Himalayas, which has affected the distribution and boundaries of various Drosophilids in this region. There is a significant decline in the number of D. nepalensis from lower ranges; whereas D. ananassae is reported to be introduced to lower to mid mountainous ranges. Further, a comparison of fecundity, hatchability, and viability at different growth temperatures has shown significant decrease in trait values at 17 °C in D. ananassae and at 25 °C in D. nepalensis. Thus, the recent range changes of these two species involve genetic effects on ecophysiological and plastic effects on life history traits. Our results indicate that thermal plasticity of life history traits can be species-specific; thus climate change may lead to a mismatch of such traits to the changing environment. We suggest that D. nepalensis and D. ananassae could serve as indicator species for analyzing range changes under changing climatic conditions. Evolutionary biologists can provide unique perspective to the examination of how climate change will affect the earth's biota.     

Two reproductive traits show contrasting genetic architectures in Plantago lanceolata

In many species, temperature‐sensitive phenotypic plasticity (i.e., an individual's phenotypic response to temperature) displays a positive correlation with latitude, a pattern presumed to reflect local adaptation. This geographical pattern raises two general questions: (a) Do a few large‐effect genes contribute to latitudinal variation in a trait? (b) Is the thermal plasticity of different traits regulated pleiotropically? To address the questions, we crossed individuals of Plantago lanceolata derived from northern and southern European populations. Individuals naturally exhibited high and low thermal plasticity in floral reflectance and flowering time. We grew parents and offspring in controlled cool‐ and warm‐temperature environments, mimicking what plants would encounter in nature. We obtained genetic markers via genotype‐by‐sequencing, produced the first recombination map for this ecologically important nonmodel species, and performed quantitative trait locus (QTL) mapping of thermal plasticity and single‐environment values for both traits. We identified a large‐effect QTL that largely explained the reflectance plasticity differences between northern and southern populations. We identified multiple smaller‐effect QTLs affecting aspects of flowering time, one of which affected flowering time plasticity. The results indicate that the genetic architecture of thermal plasticity in flowering is more complex than for reflectance. One flowering time QTL showed strong cytonuclear interactions under cool temperatures. Reflectance and flowering plasticity QTLs did not colocalize, suggesting little pleiotropic genetic control and freedom for independent trait evolution. Such genetic information about the architecture of plasticity is environmentally important because it informs us about the potential for plasticity to offset negative effects of climate change.     

Adaptation to different climates results in divergent phenotypic plasticity of wing size and shape in an invasive drosophilid

The phenotypic plasticity of wing size and wing shape of Zaprionus indianus was investigated in relation to growth temperature (17°C to 31°C) in two natural populations living under different climates, equatorial and subtropical. The two populations were clearly distinguished not only by their wing size (the populations from the colder climate being bigger in size), but also by the shape of the response curves to growth temperature i.e., their reaction norms. In this respect, the temperature at which the size of the wing was maximum was about 3°C higher in the equatorial population. Such a difference in size plasticity is already found in two other nonclosely related species, might be a general evolutionary pattern in drosophilids. Wing shape was investigated by calculating an ellipse included into the wing blade, then by considering the ratio of the two axes, and also by analysing the angular position of 10 wing-vein landmarks. For an overall shape index (ratio of the two axes of the ellipse), a regular and almost linear increase was observed with increasing temperature i.e., a more round shape at high temperatures. Wing shape was also analysed by considering the variations of the various angles according to temperature. A diversity of response curves was observed, revealing either a monotonous increase or decrease with increasing temperature, and sometimes a bell shape curve. An interesting conclusion is that, in most cases, a significant difference was observed between the two populations, and the difference was more pronounced at low temperatures. These angular variations are difficult to interpret in an evolutionary context. More comparative studies should be undertaken before reaching some general conclusions.     

Nematode parasitism in a northern European drosophilid community

Many factors may influence the structure of invertebrate communities. Among these is the presence of parasites which attack some or all members of a guild and potentially promote coexistence of competitor species. We assessed the prevalence of nematode (Allantonematidae) parasitism in Dutch woodland drosophilids (Diptera). Nematodes were found in 6 of the 18 drosophilid species sampled (percentage parasitism in parentheses): Drosophila phalerata (16%), D. kuntzei (5.1%), D. immigrans (0.5%), D. testacea (1.2%) and D. transversa (2.8%) were all parasitized by Howardula aoronymphium and D. subobscura (3%) was parasitized by Parazitylenchus diplogenus. This is the first report of nematode parasitism of D. immigrans and D. transversa. There were no important seasonal trends in percentage parasitism. We explored the consequences of nematode parasitism for individual drosophilids. Nematodes did not exert an important influence on the wing length (adult body size) of the drosophilids we sampled, but egg loads (fecundities) of female D. phalerata, D. subobscura and D. kuntzei were reduced by nematode parasitism. Parasitism rates were positively correlated with relative host abundance, in Dutch and other communities, suggesting that species diversity is promoted by a disproportionately high parasitism of more common host species.     

Population differentiation in climate sensitivity of resin duct formation during growth resumption in Pinus pinaster

To counteract the effects of herbivores and pathogens, conifers have developed a sophisticated resin-based defensive system. Since defences are costly, trees must continuously accommodate defensive investment throughout plastic responses to environmental stimuli. However, the extent of such responses can differ at the intra-specific level (i.e. genetic variation in plasticity). Here we examined whether and to what extent year-to-year climate fluctuations, an important source of environmental heterogeneity during the trees' life, drive plasticity in defensive allocation of a widespread pine species. Specifically, we quantified interannual variation in resin duct production along a 31-year-period in 174 Pinus pinaster trees of nine range-wide populations grown in two common gardens in Central Spain. We aimed to explore (i) patterns of interannual variation (i.e., temporal plasticity) in resin duct production among populations and sites, (ii) whether such patterns are linked to plastic responses to interannual variation in climate conditions (i.e., climatic plasticity), and (iii) whether plastic responses to climate differ among populations (i.e., genetic variation in plasticity) and sites. We found large interannual plasticity in resin duct production (22.8 % of total variance), with temporal patterns differing among sites and populations. Climate conditions during the early growth period significantly affected the annual differentiation of resin ducts. Particularly, April precipitation had a positive overall effect on resin duct production. Inversely, warmer conditions in April had a negative effect but only in certain populations, which demonstrates genetic variation in climate sensitivity of resin duct formation. Despite significant effects of certain climate variables on annual resin duct production, climate only accounted for a small proportion of the total interannual variation (up to 3.8 % of interannual variation explained by climate factors). This suggests that alternative factors such as trade-offs with growth and temporal variation in biotic and non-climatic abiotic conditions likely contribute to explain interannual fluctuations in defensive investment.     

Diversity and host associations of parasitoids attacking mycophagous drosophilids (Diptera: Drosophilidae) in northern and central Japan

The diversity and host associations of parasitoids attacking mycophagous drosophilids were studied in Tokyo (a warm‐temperate region) and Sapporo (a cool‐temperate region) in Japan. Field collections were carried out using traps baited with mushrooms in May, June, September and October 2009 in Tokyo and in July and August 2010 in Sapporo. The major drosophilid species that emerged from mushroom baits was Drosophila bizonata in Tokyo and D. orientacea in Sapporo. In total, 13 parasitoid species emerged from drosophilids occurring in mushroom baits, and 11 of them were larval parasitoids belonging to Braconidae and Figitidae. Among the 11 larval parasitoids, 10 were collected in Tokyo, while only two were collected in Sapporo. It is not known why their diversity differed so much between these two regions. Four of the 11 larval parasitoids have also been recorded from drosophilid larvae occurring in fruit (banana). The use of these two habitats (mushrooms and fruit) by these four species seems to reflect the occurrence (i.e. resource use) of their suitable hosts. On the other hand, most larval parasitoids from Tokyo attacked D. bizonata, and two larval parasitoids from Sapporo attacked D. orientacea, suggesting that the abundance of potential hosts is one of the important factors affecting their host use.     

Different mechanisms underlie phenotypic plasticity and interspecific variation for a reproductive character in drosophilids (Insecta: Diptera)

The insect ovary is a modular structure, the functional unit of which is the ovariole. Ovariole number is positively correlated with potential reproductive output. Among drosophilids (Insecta: Diptera), ovariole number shows both phenotypic plasticity and substantial interspecific and interpopulational variation. Here we examine the mechanistic connection between phenotypic plasticity and genetically fixed variation in ovariole number within the melanogaster species group. When a laboratory population of Drosophila melanogaster was reared under reduced food conditions, differences in ovariole number were entirely due to alterations in cell differentiation during the wandering stage at the very end of larval development. Cell growth and cell death were not affected. When these same flies were reared under a variety of temperatures, ovariole number differences arose during the latter half of the third (final) larval instar. Cell differentiation was affected, although cell number was not, and ovariole number differences were established before metamorphosis. In contrast, genetically fixed, interspecific and interpopulational variability in ovariole number was caused by alterations in the dynamics of cell differentiation and by cell number differences. Furthermore, the stages affected were different in different species and populations in the melanogaster species group, ranging from the first (D. sechellia) through the middle of the third (D. simulans and D. mauritiana) larval stage. Therefore, the mechanistic bases for plasticity-based variability are largely distinct from the mechanistic bases for interspecific and interpopulational variability. Our results suggest that phenotypic plasticity indicates evolutionary flexibility in underlying ontogenetic processes.     

Basal cold but not heat tolerance constrains plasticity among Drosophila species (Diptera: Drosophilidae)

Thermal tolerance and its plasticity are important for understanding ectotherm responses to climate change. However, it is unclear whether plasticity is traded‐off at the expense of basal thermal tolerance and whether plasticity is subject to phylogenetic constraints. Here, we investigated associations between basal thermal tolerance and acute plasticity thereof in laboratory‐reared adult males of eighteen Drosophila species at low and high temperatures. We determined the high and low temperatures where 90% of flies are killed (ULT₉₀ and LLT₉₀, respectively) and also the magnitude of plasticity of acute thermal pretreatments (i.e. rapid cold‐ and heat‐hardening) using a standardized, species‐specific approach for the induction of hardening responses. Regression analyses of survival variation were conducted in ordinary and phylogenetically informed approaches. Low‐temperature pretreatments significantly improved LLT₉₀ in all species tested except for D. pseudoobscura, D. mojavensis and D. borealis. High‐temperature pretreatment only significantly increased ULT₉₀ in D. melanogaster, D. simulans, D. pseudoobscura and D. persimilis. LLT₉₀ was negatively correlated with low‐temperature plasticity even after phylogeny was accounted for. No correlations were found between ULT₉₀ and LLT₉₀ or between ULT₉₀ and rapid heat‐hardening (RHH) in ordinary regression approaches. However, after phylogenetic adjustment, there was a positive correlation between ULT₉₀ and RHH. These results suggest a trade‐off between basal low‐temperature tolerance and acute low‐temperature plasticity, but at high temperatures, increased basal tolerance was accompanied by increased plasticity. Furthermore, high‐ and low‐temperature tolerances and their plasticity are clearly decoupled. These results are of broad significance to understanding how organisms respond to changes in habitat temperature and the degree to which they can adjust thermal sensitivity.     

Taxonomic survey of Drosophilidae (Diptera) from mangrove forests of Santa Catarina Island, Southern Brazil

Assemblages of drosophilids have been characterised in several environments of the Brazilian territory, like the Atlantic Rain Forest, urban areas, cerrados, the Amazon Forest, and others. The present survey is the first attempt to characterise the fauna of Drosophilidae in mangrove forests, an environment typical of tropical coasts worldwide. Twenty-eight samples were collected from the three main mangrove forests of Santa Catarina Island, southern Brazil, using banana-baited traps hung in trees. Samples were taken in January (summer), April (autumn), July (winter) and October (spring) between July 2002 and July 2005. In total, 82,942 specimens of drosophilids were caught, belonging to 69 species of six genera - Amiota Loew, Drosophila Fallén, Leucophenga Mik, Scaptodrosophila Duda, Zaprionus Coquillett and Zygothrica Wiedemann. The high abundance of D. simulans Sturtevant was remarkable, with some notable peaks of D. malerkotliana Parshad & Paika in autumn samples. Other common species were Zaprionus indianus Gupta, D. mediostriata Duda and D. willistoni Sturtevant. We also collected 45,826 flies of family Curtonotidae, the sister-group of Drosophilidae virtually absent in other environments. The assemblages of drosophilids were very similar in the three mangrove forests surveyed, despite the different surrounding environments. In general, the species sampled in the mangroves were the same as those observed in the surrounding environments, but in varying abundances. This suggests that drosophilids are differently affected by environmental pressures operating in mangroves.     

Evidence for "diminishing returns" from the scaling of stem diameter and specific leaf area

Research indicates that increases in total leaf area (A(T)) may fail to keep pace with increases in total leaf mass (M(L)) across plants differing in size (e.g., as measured by stem diameter, D). This "diminishing returns" hypothesis predicts that the scaling exponent for A(T) vs. M(L) will be less than one and that the exponent for specific leaf mass (i.e., A(T) / M(L)) vs. D will be negative. These predictions were examined using data from 46 plants ranging between 0.125 cm ≤ D ≤ 0.485 m across 25 woody dicot species. Standardized major axis slopes were used to quantify scaling exponents and random effects models were used to quantify species and size effects on the numerical values of exponents. The exponents for A(T) vs. M(L) and A(T) / M(L) vs. D differed among species and different species groupings. In general, the exponent for A(T) vs. M(L) was less than one and the exponent for A(T) / M(L) vs. D was negative, as predicted. However, random effects models indicated that species effects overshadowed size effects, although size effects were statistically significant. The diminishing returns hypothesis therefore receives statistical support, i.e., although the numerical values of exponents are "species-dependent," they are less than unity, as predicted by theory.