贝类壳-体质量比和静水沉降特性的相关性

软体动物贝壳表型是适应性进化的结果,为探究贝壳形态特性与软体动物随水流扩散功能的相关性,实验选取9种具代表性的腹足纲和双壳纲贝类作为研究对象,研究了其成体的壳-体质量比与静水沉降特性及二者的相关性。结果表明：体质量的变异系数（C.V.=1.11）大于壳长（C.V.=0.67）、壳宽（C.V.=0.54）的变异系数;壳-体质量比具较强的种属特异性,种内变异系数小（C.V.=0.20）,而种间差异极显著（P < 0.01）。受试贝类的平均壳-体质量比为0.32±0.13,陆生贝类的壳-体质量比显著小于水生贝类（P < 0.01）,壳-体质量比最大的河蚬（0.54±0.06）是最小的非洲大蜗牛（0.17±0.04）的3倍,福寿螺的壳-体质量比为0.50±0.06。双壳类和螺类的沉降行为差异明显,只有中华园田螺、铜锈环棱螺和河蚬不能在静水中漂浮;沉降速度最大的河蚬（（24.99±4.22）cm/s）是最小的椭圆萝卜螺（（4.13±0.96）cm/s）的6倍,入侵种非洲大蜗牛（（18.30±3.64）cm/s）和福寿螺（（21.77±5.23）cm/s）与土著种铜锈环棱螺（（19.48±3.14）cm/s）和中华园田螺（（21.44±3.92）cm/s）在沉降速度上无显著差异（P < 0.01）。成体贝类的壳-体质量比与沉降速度（R²=0.28）、沉降加速度（R²=0.39）之间存在一定的相关性。在此基础上,贝类沉降特性随生活史变化的研究将进一步揭示贝类进化与种群扩散中的生态水力学作用。     

The influence of periphyton biomass and density on grazing in Physella virgata

We studied how differences in periphyton colonization interval and snail density affected grazing rates in Physella virgata, and whether snails controlled periphyton biomass. Both egestion rates and incorporation rates of ¹⁴C labeled periphyton were estimated in laboratory experiments. Periphyton biomass increased with field colonization interval in all experiments, but did not consistently influence estimates of grazing rate. However, increased periphyton abundance in one of the experiments could still explain higher grazer rates in that year, although larger snail body size is a confounding explanation. Increased snail density also resulted in decreased grazing rates, as observed in earlier studies with this snail species, as well as in studies with other snail grazers. Our results suggest grazing rates and resulting impacts may change seasonally with variation in either periphyton biomass, grazer life-history stage or population density.     

Does Eucalyptus grandis invasion and removal affect soils and vegetation in the Eastern Cape Province,South Africa?

Many invasive alien plants drive changes in native community composition, structure and diversity. They alter soil nutrient regimes of native communities and affect native plant recovery outcomes following their removal. We assessed whether Eucalyptus grandis invasion and removal alters the soil physico‐chemical properties and native vegetation recovery in the Eastern Cape Province, South Africa. We collected samples from topsoil in E. grandis invaded sites (canopy cover > 75%), cleared sites (eight years ago) and native sites (canopy cover > 80%) and quantified soil moisture, concentrations of soil macro elements (N, C and P), pH and exchangeable cations (K, Ca, Mg, Na) as well as measured soil water repellency using the Water Droplet Penetration Time and infiltration. We conducted vegetation surveys in plots measuring 10 × 10 m. Invasion by E. grandis had varying effects on soil physico‐chemical properties, causing increase in soil pH and P, while decreasing total N and C. The removal of E. grandis also showed varying effects on soil physico‐chemical properties, but seems to have further triggered the loss of some soil nutrients (especially soil P). Soil water repellency (a measure of soil compaction) has improved in cleared sites to non‐repellent soils compared to repellent soils in invaded site. Eucalyptus grandis reduced species richness of the invaded sites. The presence of native species on cleared sites indicates a positive trajectory towards vegetation recovery. We conclude that E. grandis invasion and removal trigger varying effects on soil properties (both increases and decreases). For soil and vegetation restoration of cleared sites to be effective, active restoration techniques such as soil transfer, nutrient manipulation and native plant seeding should be considered.     

X-Ray and IR-Studies on the Dehydrated Fish Flesh

Many actinomycetes, newly isolated from soil, converted (?)-carvone to either (?)-trans-carveol or (?)-cis-carveol or to a mixture of both compounds, and known metabolic products, such as (+)-dihydrocarvone, (+)-isodihydrocarvone, (+)-neodihydrocarveol, (?)-dihydrocarveol, (+)-isodihydrocarveol and (+)-neoisodihydrocarveol.

Identification of the metabolic products and the metabolic pathways of (?)-carvone were described in a strain of Streptomyces, A-5–1 and a strain of Nocardia, 1-3-11. A summary shows the reaction mechanism pattern of (?)-carvone conversion by actinomycetes.     

Effects of macrophytes on feeding and life-history traits of the invasive apple snail Pomacea canaliculata

1. Biological invasions have become a serious threat to ecosystems worldwide. Various factors can contribute to the success of biological invasion. We examined how different macrophyte food affected feeding and life‐history traits of the invasive herbivorous snail Pomacea canaliculata, and whether differences in snail life‐history traits could explain its successful infestation of agricultural and non‐agricultural wetlands in Asia. 2. We tested five cultivated and five wild semi‐aquatic macrophytes. Snail daily feeding rate varied substantially with plant species, ranging from 1.3% to 22% of its body mass. Snails fed with four (Amaranthus gangeticus, Apium graveolens dulce, Ipomoea aquatica and Nasturtium officinale) of the five cultivated macrophyte species exhibited high survivorship, fast growth and high fecundity. Snails fed with Colocasia esculenta, however, grew poorly, did not reproduce and eventually died. 3. Of the five wild species (Eichhornia crassipes, Ludwigia adscendens, Murdannia nudiflora, Myriophyllum aquaticum and Polygonum hydropiper), M. nudiflora supported a high snail survival, but snails had slower growth and lower fecundity than those reared on the four palatable cultivated species. Snails fed with L. adscendens grew substantially slower than those fed with M. nudiflora, and produced only a small clutch of eggs. Snails fed with E. crassipes, M. aquaticum and P. hydropiper had very low survivorship, grew very little and did not reproduce. 4. We determined six plant properties and their correlation with the feeding, growth and reproduction of the apple snails. Cultivated macrophytes in general had a higher nutritional value and lower physical and chemical defences. Phenolic content was negatively correlated with snail feeding rate, while plant nitrogen and phosphorus contents were positively correlated with snail egg production and growth, respectively. 5. These results indicate that, due to their higher nutritional value and lower chemical and physical defences, cultivated macrophytes are in general desirable for the apple snail which may partly explain its successful invasion into wet agricultural areas in Asia. This snail may also selectively graze poorly defended wild macrophytes in non‐agricultural wetlands, leading to changes in floral diversity and wetland functioning. Management of this and other apple snails with similar life‐history traits should thus focus on the prevention of their further spread.     

生物入侵及其影响

生物入侵是物种进入其在进化史上未分布过的地域而且能在该地繁衍.生物入侵是一种十分普遍的现象.生物入侵的影响大,危害严重.生物入侵的影响有:①对生物个体的影响;②对遗传的影响; ③对种群动态的影响;④对群落的影响;⑤对生态系统进程的影响.不同的生物入侵造成的影响不一样,应该有区别地分析.     

Patterns of Patchy Spread in Deterministic and Stochastic Models of Biological Invasion and Biological Control

A few spatiotemporal models of population dynamics are considered in relation to biological invasion and biological control. The patterns of spread in one and two spatial dimensions are studied by means of extensive numerical simulations. We show that, in the case that population multiplication is damped by the strong Allee effect (when the population growth rate becomes negative for small population density), in a certain parameter range the spread can take place not via the intuitively expected circular expanding population front but via motion and interaction of separate patches. Alternatively, the patchy spread can take place in a system without Allee effect as a result of strong environmental noise. We then show that the phenomenon of deterministic patchy invasion takes place ‘at the edge of extinction’ so that a small change of controlling parameters either brings the species to extinction or restores the travelling population fronts. Moreover, we show that the regime of patchy invasion in two spatial dimensions actually takes place when the species go extinct in the corresponding 1-D system.     

中国外来入侵物种的分布与传入路径分析

外来物种入侵已成为全球性的环境问题,本文采用文献调研,实地考察与专家咨询相结合的方式,调查了全国陆生,淡水水生生态系统中外来入侵微生物,无脊椎动物,两栖爬行类,鱼类,鸟类,哺乳类,杂草,树木和海洋生态系统中外来入侵物种的种类及分类地位,起源,引入路径和环境影响等内容。查明我国共有283种外来入侵物种,其中外来入侵微生物,水生植物,陆生植物,水生无脊椎动物,陆生无脊椎动物,两栖爬行类,鱼类,哺乳类分别为19种,18种,170种,25种,33种,3种,10种和5种,来源于美洲,欧洲,亚洲,非洲,大洋洲的外来入侵物种分别占55.1%,21.7%,9.9%.8.1%和0.6%。我国对外来物种的引进存在一定程度的盲目性;50.%的外来入侵植物是作为牧草或饲料,观赏植物,纤维植物,药用植物,蔬菜,草坪模特而引进的;25%的外来入侵动物是用于养殖,观赏,生物防治的引种,对外来物种只重引进,疏于管理,也可能导致外来物种逃逸到自然环境中,造成潜在的环境意传入的;76.3%的外来入侵动物是由于检查不严,随贸易物品或运输工具传入我国的。因此,我国既要加强检疫工作,又要对外来物种的有意引进进行严格管理,实行外来物种引进的风险评估制度。     

生物入侵机制研究进展

本文从外来种本身的生物学特性,外来种与新栖息地土著种之间的相互作用,群落生物多样性对入侵种的抵抗能力,新栖息地生态环境变化对入侵种的影响等方面综述了近年来有关生物入侵机制的研究进展,并探讨了研究方法的发展和亟待解决的问题,大量的研究表明生物入侵机制是极为多样的,可能没有一般的,通用的机制,阐明生物入侵的机制,对推动生态学理论的发展和控制有害外来种有重要意义。     

Allometric and trophic effects on shell morphology of Pomacea canaliculata (Caenogastropoda,Ampullariidae) from a geometric morphometrics viewpoint

Pomacea canaliculata, an invasive apple snail native to South America, is a serious pest of aquatic crops in several parts of the world. The origin of inter-population variation in shell shape is thought to be both genetic and environmental but the reaction norms to specific environmental factors are still poorly understood. Our aims were to analyze the existence of direct and indirect (allometric) effects of food availability (FA) on the shape of young adults of P. canaliculata. Full sibling hatchlings were reared under different levels of FA. Nine landmarks and 10 semi-landmarks were determined on photographs of mature shells and analyzed using geometric morphometrics. In both sexes significant allometry was found: a decrease in the spire height in both sexes, and an increase of the aperture size in males and of the last whorl in females. When this allometric component was removed a relationship between size-corrected shape and FA was found only in females, which were more globose and had a larger aperture when grown under high FA. This effect may be explained by the faster growth of the reproductive organs and the thinner shells of the best fed females.     

Control of the invasive weed Ambrosia artemisiifolia with Ophraella communa and Epiblema strenuana

Ambrosia artemisiifolia L. is native to North America, and was unintentionally introduced into China in the 1930s, where it has become invasive. The two insect species Epiblema strenuana and Ophraella communa have been considered as biological control agents of A. artemisiifolia in China. The purpose of this study was to examine the control effect of O. communa + E. strenuana on A. artemisiifolia in the field. The mortality of A. artemisiifolia plants increased with time and increasing initial release densities of O. communa and/or E. strenuana in 2008 and 2009. The treatments of 0.53 O. communa + 0.53 E. strenuana per plant and 12 O. communa + 16 E. strenuana per plant at early (60–70 cm tall) and later (90–100 cm tall) growth stages could subsequently kill all plants prior to seed production in both 2008 and 2009. Thus, the two initial densities of the two insect species may be recommended when they are jointly used for biological control of A. artemisiifolia at the two growth stages. However, all or some plants could survive and bear seeds in any other treatment and in the non-treated control plots. This implies that biological control of A. artemisiifolia with the two biological control agents will be recommended in the areas invaded by A. artemisiifolia in China.