中国瓢虫体型的地理分异及其与环境因子的关系

生物体的外在形态(个体大小及异速生长)不仅是分类学的重要依据, 也是影响生物与环境相互作用的重要功能性状。昆虫体型的地理分异及其机制是昆虫生物地理学的重要基础。本文基于中国省级行政区的瓢虫体型、分布和环境因子数据, 运用相关和回归分析, 探索了中国瓢虫体型(体长、体宽与长宽比)的纬度地带性及其与环境因子的关系。为了确定营养级对瓢虫体型特征的影响, 我们对全部瓢虫、植食性瓢虫和捕食性瓢虫分别进行分析。研究结果表明: (1)瓢虫的体型大小具有显著的纬度地带性, 即纬度越高, 瓢虫的体长或体宽越大, 符合贝格曼法则。与温度相关的环境因子是导致瓢虫体型大小地理分异的主要环境因素, 因为瓢虫以成虫越冬, 体型越大则能量储存越多, 冬眠期间的耐饥力越强; (2)由于食性和食物空间分布的差异, 在各个纬度上, 植食性瓢虫体型总是大于捕食性瓢虫; 捕食性瓢虫的长宽比与纬度呈显著正相关, 即纬度越高, 瓢虫体型越狭长; 而植食性瓢虫的长宽比与纬度没有显著的相关性; 捕食性瓢虫的长宽比与年降水量呈显著负相关, 因为年降水量降低导致植被的斑块化增加, 引起捕食对象分布更为分散, 从而要求瓢虫具有更强的飞行能力, 即更大的长宽比。综上所述, 在省级尺度上, 温度和降水分别主要影响瓢虫的大小和长宽比, 其效应随营养级(食性)的变化而变化。     

干旱胁迫对大豆鼓粒期叶片光合能力和根系生长的影响

以晋大70(抗旱型)和晋豆26(敏感型)2个大豆品种为材料,采用盆栽方法,在鼓粒期设置充分供水、轻度干旱和重度干旱3种水分处理,研究了干旱胁迫对大豆鼓粒期叶片光合能力和根系生长的影响.结果表明： 随着干旱程度加剧,2个品种的叶面积、叶绿素含量、净光合速率、叶片气孔导度、蒸腾速率、胞间CO₂浓度、株质量、株高、籽粒产量和收获指数均降低;根长和根质量在轻度干旱胁迫下增加,在重度干旱胁迫下减少;根冠比随干旱程度加剧而升高.重度干旱胁迫下,抗旱型品种晋大70根冠比的增幅达到135.7%,大于敏感型品种晋豆26根冠比的增幅(116.7%),晋大70的叶面积和叶绿素含量分别为对照的69.3%和85.5%,均优于晋豆26,晋大70的气孔导度和净光合速率分别下降了67.9%和77.9%,降幅均小于晋豆26,晋大70的收获指数的降幅为43.8%,小于晋豆26 (78.8%).不同干旱处理下,2个品种的叶面积、叶绿素含量、净光合速率、气孔导度、蒸腾速率、胞间CO₂浓度两两之间均呈显著正相关;株质量、株高、根长、根质量、籽粒产量、收获指数两两之间均呈显著正相关;根冠比与根质量呈显著正相关,而与其他5个指标呈显著负相关.     

Influence of barley grain particle size and treatment with citric acid on digestibility,ruminal fermentation and microbial protein synthesis in Holstein calves

Chemical and physical treatments of barley grain increase ruminally resistant starch and can improve the rumen fermentation pattern. The objective of the present study was to evaluate the effects of chemical (addition of citric acid, CA) and physical (grinding to two different particle sizes, PS) treatment of barley grain on performance, rumen fermentation, microbial protein yield in the rumen and selected blood metabolites in growing calves. In all, 28 male Holstein calves (172±5.1 kg initial BW) were used in a complete randomised design with a factorial arrangement of 2 barley grain particle sizes×2 levels of citric acid. The diets were as follows: (i) small PS (average 1200 µm) barley grain soaked in water (no CA addition); (ii) small PS barley grain soaked in a CA solution (adding 20 g CA/kg barley); (iii) large PS (average 2400 µm) barley grain soaked in water (no citric acid addition) and (iv) large PS barley grain soaked in a citric acid solution (adding 20 g CA/kg barley). Barley grain was then incorporated at 35% in a total mixed ration and fed to the calves for 11 weeks. Feeding small PS barley decreased feed intake (P=0.02) and average daily weight gain (P=0.01). The addition of CA to barley grain did not affect intake but increased weight gain (P<0.01) and improved feed to gain ratio (P=0.03). Digestibility of organic matter and NDF tended (P<0.10) to increase, whereas faecal scoring was improved (P=0.03) and the presence of undigested grain particles in faeces was reduced (P<0.01) with CA-treated barley grain. Glucose and urea concentrations were increased (P<0.01) in the blood of calves fed the CA-treated barley grain. Ruminal pH tended (P=0.08) to be decreased with more finely ground barley and was increased when barley grain was treated with CA. Total volatile fatty acid concentrations in the rumen did not differ among treatments (P>0.05). However, the molar proportion of propionate was increased (P=0.03) when barley was more finely ground, and that of acetate was increased (P=0.04) when CA was added to barley grain. The ruminal concentration of ammonia nitrogen was increased (P<0.01) and microbial nitrogen synthesis in the rumen tended to decrease by adding CA to barley. Treating barley grain with citric acid increased fibre digestibility of total mixed rations, attenuated the decrease in ruminal pH, and improved weight gain and feed efficiency in male Holstein growing calves fed a high-cereal diet (550 g cereal grain/kg diet).     

Ontogenetic trajectory and allometry of Diplonychus rusticus (Fabricius), an Oriental aquatic bug (Hemiptera: Belostomatidae) from the Western Ghats of India

Despite being one of the dominant groups in freshwater ecosystems, morphological and ontogenetic studies on aquatic Hemiptera have received little attention in the Oriental region. We present the ontogenetic trajectory and allometry of the widespread Oriental belostomatid species, Diplonychus rusticus (Fabricius) for the first time. We have measured nine different morphological variables throughout the growth of the bug using both field captured and laboratory reared specimens. Our results suggest that the developmental instars can be distinguished by the size variables, as seen in the Principal Component Analysis. On the basis of a CHAID (Chi-squared Automatic Interaction Detection) based regression tree, we also show that the characters – total length without head and maximum width – prove to be adequate for effective instar identification. The multivariate allometric growth pattern shows that different body parts exhibit different types of allometry. This is apparent in the allometry exhibited by forelegs and mid and hind legs, which show allometry of opposite polarities. This may be due to the different functions attributed to these body parts. Our results show that the growth pattern in D. rusticus is comparable with the New World genus Belostoma, suggesting a conserved growth pattern in the family Belostomatidae.     

Phytochelatin synthase OsPCS1 plays a crucial role in reducing arsenic levels in rice grains

Reduction of the level of arsenic (As) in rice grains is an important challenge for agriculture. A recent study reported that the OsABCC1 transporter prevents the accumulation of As in grains by sequestering As–phytochelatin complexes into vacuoles in the upper nodes. However, how phytochelatins are provided in response to As remains unclear. Here, we show that the phytochelatin synthase OsPCS1 plays a crucial role in reducing As levels in rice grains. Using a forward genetic approach, we isolated two rice mutants (has1 and has2) in which As levels were much higher in grains but significantly lower in node I compared with the wild type. Map‐based cloning identified the genes responsible as OsABCC1 in has1 and OsPCS1 in has2. The levels of As in grains and node I were similar between the two mutants, suggesting that OsABCC1 preferentially cooperates with OsPCS1 to sequester As, although rice has another phytochelatin synthase, OsPCS2. An in vitro phytochelatin synthesis assay indicated that OsPCS1 was more sensitive to activation by As than by cadmium, whereas OsPCS2 was more weakly activated by As than by cadmium. Transgenic plants highly expressing OsPCS1 showed significantly lower As levels in grains than did wild‐type plants. Our results provide new knowledge of the relative contribution of rice PCS paralogs to As sequestration and suggest a good candidate tool to reduce As levels in rice grains.     

Overexpression of TIFY genes promotes plant growth in rice through jasmonate signaling

Because environmental stress can reduce crop growth and yield, the identification of genes that enhance agronomic traits is increasingly important. Previous screening of full-length cDNA overexpressing (FOX) rice lines revealed that OsTIFY11b, one of 20 TIFY proteins in rice, affects plant size, grain weight, and grain size. Therefore, we analyzed the effect of OsTIFY11b and nine other TIFY genes on the growth and yield of corresponding TIFY-FOX lines. Regardless of temperature, grain weight and culm length were enhanced in lines overexpressing TIFY11 subfamily genes, except OsTIFY11e. The TIFY-FOX plants exhibited increased floret number and reduced days to flowering, as well as reduced spikelet fertility, and OsTIFY10b, in particular, enhanced grain yield by minimizing decreases in fertility. We suggest that the enhanced growth of TIFY-transgenic rice is related to regulation of the jasmonate signaling pathway, as in Arabidopsis. Moreover, we discuss the potential application of TIFY overexpression for improving crop yield.     

High-elevation inter-site differences in Mount Smolikas tree-ring width data

We present the longest high-elevation tree-ring width dataset in the Mediterranean reaching back to the 6th century CE. The network includes 101 living and 92 relict Pinus heldreichii Christ trees from four differently exposed sites in the 2100–2200 m a.s.l. elevation range of Mt. Smolikas in the Pindus Mountains in Greece. Though the sites were all sampled within a distance of <1 km, inter-site correlations are surprisingly low (r_1550–2014 = 0.65–0.87), indicating site exposure might affect tree-ring formation. We here explore the consequence of exposure differences on the climate signals in an eastern Mediterranean treeline ecotone. Temporally stable growth/climate relationships reveal similar seasonal patterns among the four sites, but differences in signal strength. P. heldreichii growth at Mt. Smolikas is significantly controlled by temperature in April (r_1951–2014 = 0.33–0.50) and precipitation in June-July (r_1951–2014 = 0.23–0.42), which emphasizes the overall importance of an early growth onset and subsequent moisture conditions. The association between stem growth and April climate is strongest in the South-facing stand, supporting the significance of higher insolation rates at this thermally privileged site. Strongest summer precipitation signals are found in the NE-facing stand, where trees seem to benefit least from an early growth onset and where reduced meltwater supply may enhance the dependency on early summer precipitation. The significance of spring temperature on tree growth in all four sites constrains the emergence of a distinct summer precipitation signal in the Mt. Smolikas high elevation ecotone. Exploration of the site-specific influences on a new millennium-long tree-ring width dataset is an important step towards an improved understanding of long-term climate variability in the Eastern Mediterranean. Site-related differences in climate sensitivity in the high-elevation tree-ring network at Mt. Smolikas indicate that both temperature and precipitation during different seasons could potentially be reconstructed if distinct site exposures (S versus NE) are considered.     

Sampling grain influences trends in vegetation composition and diversity with time since fire in Australian heathland

Scale‐dependency of pattern and process is well‐understood for many ecological communities; however, the influence of spatial scale (sampling grain) in detecting temporal change in communities is less well‐understood. The temperate lowland heathlands of south‐east Australia are one of the most fire‐prone ecosystems on earth. Despite the extensive literature documenting the effect of time since fire on heathlands, we know little about how sampling grain influences trends in vegetation variables over time, and whether these trends are scale‐dependent. Using 3500 ha of heathland in the Gippsland Lakes Coastal Park, south‐east Australia, we investigated how above‐ground species composition and diversity, and trends in these variables with increasing time since fire, were influenced by sampling grain (1 m², 10 m², 100 m², 900 m², 1 ha, 4 ha). Sampling grain influenced patterns detected in vegetation variables and in some instances, significantly affected their relationship with time since fire. Richness decreased with time since fire, with mean richness decreasing at three of the four grains, while total richness decreased at half of the sampled grains. Evenness (J) decreased with increasing time since fire for all grains except 1 m². The decline in diversity (H) with time since fire appeared to be independent of scale, as all grains decreased significantly with increasing time since fire. Community heterogeneity demonstrated a weak response to time since fire across most grains. Changes in composition among young (0–6 years since fire), intermediate (9–19 years) and old (23–27 years) sites were dependent on sampling grain, with all grains exhibiting significant differences in composition, apart from the 1 m² grain and the 100 m² grain (presence/absence data). Overall, species composition, richness, evenness, diversity and community heterogeneity were dependent on the scale at which the vegetation was sampled. In addition, trends in many of these vegetation variables with increasing time since fire were scale‐dependent. This work provides strong evidence that sampling at multiple grains contributes substantially to understanding pattern and process in heathlands.     

Sex-specific responses of tree-ring growth to climate in the dioecious tree Populus cathayana

Aims Radial growth in response to climate has been reported in many trees, but the sex-specific responses of tree-ring growth associated with altitude in dioecious trees are still poorly known. This study aims to examine whether (i) there are sex-related responses of tree-ring growth to climate in dioecious trees; (ii) these responses could be changed with altitude elevation.