Spiders and subsidies: results from the riparian zone of a coastal temperate rainforest

1. Aquatic insects emerging from streams can provide an important energy subsidy to recipient consumers such as riparian web-building spiders. This subsidy has been hypothesized to be of little importance where the primary productivity of the recipient habitat exceeds that of the donor habitat. 2. To test this hypothesis, we manipulated emerging stream insect abundance in a productive riparian rainforest in a replicated design using greenhouse-type exclosures, contrasted with unmanipulated stream reaches (four exclosures on two streams). 3. Experimental exclosures resulted in a 62.9% decrease in aquatic insect abundance in exclusion reaches compared with control reaches. The overall density of riparian spiders was significantly positively correlated with aquatic insect abundances. Horizontal orb weavers (Tetragnathidae) showed a strong response to aquatic insect reduction - abundance at exclosure sites was 57% lower than at control sites. Several spider families that have not been associated with tracking aquatic insect subsidies also showed significantly decreased abundance when aquatic insects were reduced. 4. This result is contrary to predictions of weak subsidy effects where recipient net primary productivity is high. These results suggest that predicting the importance of resource subsidies for food webs requires a focus on the relative abundance of subsidy materials in recipient and donor habitats and not simply on the total flux of energy between systems.     

Tangled webs: reciprocal flows of invertebrate prey link streams and riparian zones

1. Streams and their adjacent riparian zones are closely linked by reciprocal flows of invertebrate prey. We review characteristics of these prey subsidies and their strong direct and indirect effects on consumers and recipient food webs. 2. Fluxes of terrestrial invertebrates to streams can provide up to half the annual energy budget for drift‐feeding fishes such as salmonids, despite the fact that input occurs principally in summer. Inputs appear highest from closed‐canopy riparian zones with deciduous vegetation and vary markedly with invertebrate phenology and weather. Two field experiments that manipulated this prey subsidy showed that it affected both foraging and local abundance of stream fishes. 3. Emergence of adult insects from streams can constitute a substantial export of benthic production to riparian consumers such as birds, bats, lizards, and spiders, and contributes 25–100% of the energy or carbon to such species. Emergence typically peaks in early summer in the temperate zone, but also provides a low‐level flux from autumn to spring in ice‐free streams. This flux varies with in‐stream productivity, and declines exponentially with distance from the stream edge. Some predators aggregate near streams and forage on these prey during periods of peak emergence, whereas others rely on the lower subsidy from autumn through spring when terrestrial prey are scarce. Several field experiments that manipulated this subsidy showed that it affected the short‐term behaviour, growth, and abundance of terrestrial consumers. 4. Reciprocal prey subsidies also have important indirect effects on both stream and riparian food webs. Theory predicts that allochthonous prey should increase density of subsidised predators, thereby increasing predation on in situ prey and causing a negative indirect effect via apparent competition. However, short‐term experiments have produced either positive or negative indirect effects. These contrasting results may be due to characteristics of the subsidies and individual consumers, but could also result from differences in experimental designs. 5. New study approaches are needed to better determine the direct and indirect effects of reciprocal prey subsidies. Experiments coupled with comparative research will be required to measure their effects on individual consumer fitness and population demographics. Future work should investigate whether reciprocal prey fluxes stabilise linked stream–riparian ecosystems, explore how landscape context affects the magnitude and importance of subsidies, and determine how impacts of human disturbance can propagate between streams and riparian zones via these trophic linkages. Study of these reciprocal connections is helping to define a more holistic perspective of catchments, and has the potential to shape new directions for ecology in general.     

角倍蚜性母的羽化和生殖规律

为了深入研究角倍蚜Schlechtendalia chinensis(Bell)性母的羽化和生殖规律,为角倍人工培育技术的改进和产量的提高提供科学依据。本文采用培养皿保湿培养载有角倍越冬若蚜的藓块,收集刚羽化的性母置于培养皿内单头培育,连续观察并记录角倍蚜性母的羽化和生殖过程。结果表明:角倍蚜性母全天均可羽化,19:00的羽化量最大,为羽化总数的42.96%;在18²2℃条件下,羽化过程持续6 d,其中前3 d的羽化量最多,为总羽化量的73.05%,羽化后2 h开始产性蚜,其中24 h内产性蚜最多,为性蚜总数的84.61%。性母一生可产性蚜122℃条件下,羽化过程持续6 d,其中前3 d的羽化量最多,为总羽化量的73.05%,羽化后2 h开始产性蚜,其中24 h内产性蚜最多,为性蚜总数的84.61%。性母一生可产性蚜1⁴次,其中56.67%的性母一生产性蚜2次。性母的产性蚜次数与产蚜量之间呈极显著正相关。60.00%的性母可产雌、雄两种性别的性蚜,36.67%的性母一生只产雄性蚜,仅有3.33%的性母一生只能产雌性蚜;雄性蚜的产出时间平均比雌性蚜早2 h。     

Life Cycle,Production and Survival Rates of Ptychoptera paludosa(Diptera: Ptychopteridae)

Life cycle, survival and production of the univoltine midge Ptychoptera paludosa whose larvae live in fine sandy sediments were studied in a German stream (1989–1990). Growth of the 4th larval instar was linear. Adults emerge from May, for ca 8 weeks (1985–1990); emergence was 0.56 g dry weight m^–2 lentic area (1990). Density decreased strongly only when larvae were young; except after an exceptional spate, numbers emerging were independent of discharge. Larval survival was ca 9%; only 10% of the potential offspring of the survivors actually appeared in the next generation. Secondary production (P) was 2.3 g ash free dry weight (AFDW) m^–2y^–1, mean biomass (B) was 0.6 g AFDW m^–2, i.e., the P/B ratio was 3.8.     

广东顺德生态乐园夏季鸟类资源和保护

报道了顺德生态乐园夏季鸟类资源的调查 ,记录了该乐园鸟类有 55种 ,隶属 6目2 0科 ,其中属国家二级重点保护鸟类 9种。对鸟类的生态作用、种类和组成作了讨论 ,并提出了保护鸟类的重要性和保护措施。     

河岸带生态系统退化机制及其恢复研究进展

恢复和重建自然和人为干扰导致的退化河岸带生态系统是目前恢复生态学、流域生态学等学科研究的重要内容之一．对河岸带生态系统的干扰表现在河流水文特征改变、河岸带直接干扰和流域尺度干扰3个方面,分别具有不同的影响机制．河流水文特征改变通过改变河岸土壤湿度、氧化还原电位、生物生存环境以及沉积物传输规律对河岸带生态系统产生影响;河岸带直接干扰通过人类活动及外来物种入侵而直接影响河岸带植被多样性;流域尺度干扰则主要表现在河道刷深、河道淤积、河岸带地下水位降低和河流冲刷过程改变等．河岸带生态恢复评价对象包括河岸带生态系统各要素,评价指标已从单一的生态指标转向综合性指标．河岸带生态恢复应在景观或者流域尺度上进行考虑,识别对其影响的生物和物理过程以及导致其退化的干扰因子,通过植被重建与水文调控来进行．扩展研究尺度和研究对象及采用多学科的研究方法将是今后相关研究中的重要问题．     

The impacts of climate change on the annual cycles of birds

Organisms living today are descended from ancestors that experienced considerable climate change in the past. However, they are currently presented with many new, man-made challenges, including rapid climate change. Migration and reproduction of many avian species are controlled by endogenous mechanisms that have been under intense selection over time to ensure that arrival to and departure from breeding grounds is synchronized with moderate temperatures, peak food availability and availability of nesting sites. The timing of egg laying is determined, usually by both endogenous clocks and local factors, so that food availability is near optimal for raising young. Climate change is causing mismatches in food supplies, snow cover and other factors that could severely impact successful migration and reproduction of avian populations unless they are able to adjust to new conditions. Resident (non-migratory) birds also face challenges if precipitation and/or temperature patterns vary in ways that result in mismatches of food and breeding. Predictions that many existing climates will disappear and novel climates will appear in the future suggest that communities will be dramatically restructured by extinctions and changes in range distributions. Species that persist into future climates may be able to do so in part owing to the genetic heritage passed down from ancestors who survived climate changes in the past.     

MicroRNA在昆虫变态及生殖过程中的调控作用

MicroRNA（miRNA）是一类广泛存在于真核生物中的小分子非编码RNA,通过抑制靶基因的翻译过程或降解靶基因的mRNA,在转录后水平上调控基因表达。在昆虫中已报道了大量的miRNA,其中部分miRNA的功能得到了解析。在昆虫变态过程中,let-7, miR-100, miR-125, miR-34, miR-14, miR-8, miR-281和 miR-252-3p能够作用于保幼激素或蜕皮激素信号通路,影响昆虫蜕皮、化蛹或翅、足及神经系统的发育。在昆虫生殖阶段,bantam, miR-184和miR-275影响生殖干细胞的分化或卵子发生。本文在介绍miRNA生物合成和作用机制的基础上,重点对昆虫变态与生殖过程中miRNA的最新研究进展进行综述。     

The demography of coarse wood in north temperate lakes

1. Exchange of material across habitat boundaries is a key process in riparian zones. The movement of coarse wood from lakeshore forests to the littoral zone, where it provides habitat for aquatic organisms, is not well understood. In 2003, we resampled coarse wood within the littoral zone of four lakes in Northern Wisconsin (U.S.A.), that had originally been surveyed in 1996, to quantify the spatial arrangement of littoral coarse wood and estimate input, loss and movement rates.
2. All four lakes had a clumped pattern of littoral coarse wood, and the locations of clusters were similar in both census years. Littoral coarse wood was more abundant than expected on moderate to steep slopes, on southern shorelines, and in areas with sparse residential development.
3. All four lakes had a net accumulation of coarse wood; rates of wood input ranged from 0.5 to 1.9 logs km⁻¹ year⁻¹, i.e. there was more wood in 2003 than 1996. Movement rates of tagged logs varied 14-fold among lakes, with a maximum in one lake of 42% of logs recovered in 2003 more than 20 m from their 1996 location. Median distance moved ranged from 22 to 323 m among the four lakes.
4. Areas of persistently high wood density may be keystone habitats whose presence enables the persistence of populations of certain aquatic organisms. Conservation of locations with high wood density may be important to maintain target densities of coarse wood of lakes with human development.