Occurrence patterns of alien freshwater turtles in a large urban pond ‘Archipelago’ (Rome,Italy): Suggesting hypotheses on root causes

The patterns of the occurrence and distribution of alien freshwater turtle species in an urban pond archipelago (Rome, Italy) were analysed, with the aim of exploring the role of a set of factors (type of ponds, landscape context, size area, distance from the nearest road) with a generalized linear model approach. A total of 311 ponds subdivided in three types (fountains, small basins, lakes) embedded in different landscape contexts (public parks, private parks, urban areas) at differing distances from the nearest road were sampled. Six non‐native freshwater turtle species in 31 sites were recorded (9.97%). Lakes exhibited the highest occurrence rates of alien freshwater turtles, compared to small basins and fountains. Freshwater turtle species in urbanized areas were only observed in parks (both public and private). In both the public and private parks, the lakes exhibited the highest percentage of occupied sites, with fountains being the lowest. A direct and significant relationship was observed between pond size and species richness. The distance from the nearest road did not appear to affect species richness. A first interpretation of the data from this study facilitated the postulation of two a posteriori hypotheses that should be tested, as follows: (i) the causal process of turtle release is random, and the rate of extinction (and recapture) is higher in smaller ponds, thus producing the observed pattern; and (ii) the turtle release is not random, and people actively select the ponds they consider more suitable for their pet animals. In this study, it appears the lakes were perceived by those who abandon their pets as the most ecologically suitable habitats among other pond types to accommodate the different species of turtles. Knowledge of people's attitudes in regard to releasing pet animals also might assist managers of public green spaces to develop strategies aimed to preserve local biodiversity, and to educate the public about the conservation issue represented by the alien species.     

异源细胞质对普通小麦花粉育性的影响

本文以中国春小麦细胞核置换到小麦属和山羊草属不同细胞质的同核异质稳定核质杂种为材料,研究了异源细胞质对普通小麦花粉育性及小孢子发育的影响,结果表明;普通小麦中国春的花粉育性不同程度地受到多种异源细胞质的明显影响,其小孢子败育主要发生在四分体时期.     

Conflicts between Perception and Reality in the Management of Alien Species in Forest Ecosystems: A Norwegian Case Study

The vegetation dynamics and landscape management during 20 years of a temperate deciduous forest protected as a nature reserve in western Norway are analysed. Sycamore (Acer pseudoplatanus), an alien species in northern Europe, has become abundant in parts of the forest and the paper discusses how nature management has formulated and interpreted the introduction of sycamore. Scientists and nature managers regard the species as aggressive and a threat to the local natural biodiversity, but in this respect empirical evidence has been replaced by assumption and prejudice, and this is critically reviewed in the paper. The development of the forest has been monitored annually since 1988 and the long-term forest dynamics and behaviour of sycamore are discussed in relation to the attitudes of nature managers. The views held by nature managers are based on their own values and ideas regarding what is valuable nature, and alien species are often assumed to be invasive and aggressive, yet with no reference being made to site ecology and human local history. As an alternative to an a priori understanding of the role of alien species, the paper suggests that proper knowledge of ecosystem dynamics can only be achieved through analysis of ecological variation in space and time. The management of any species should not be according to its status as native or alien, but according to a judgment of its role and long-term behaviour. The values of nature conservationists should not be confused with the intrinsic values of nature.     

Relationship between vegetation of the levee neo‐ecosystems and environmental heterogeneity in the Lower Delta of the Paraná River,Argentina

The relationship between environmental heterogeneity and the vegetation of the levee neo‐ecosystems in the Delta of the Paraná River was studied. These habitat types were considered plant communities of recent origin related to local productive activities. Vegetation coverage was evaluated in 97 plots of three different environmental units (A, B and C), using classification analysis, indirect and direct ordinations. The differential vegetation in different environmental units could be related to a greater fluvial influence of the Paraná River on unit A and a greater tidal influence of the de la Plata River on units B and C. The Lower Delta hydrological regimes only affect a few of edaphic variables particularly pH, organic matter percentage and clay content. To understand the spatial pattern of neo‐ecosystems vegetation, it is also necessary to consider the invasion of alien species that has been taking place for over 50 years.     

Drivers of Plant Invasion at Broad and Fine Scale in Short Temperate Streams

Riparian ecosystems have been described as highly prone to alien plant invasions; thus, disentangling the contributing factors of the invasion process is of utmost importance to conserving and managing these valuable ecosystems. In this study we examined the drivers of riparian plant invasion in 16 Cantabrian river basins (northern Spain) ranging from 100 to ca. 1050 km². A complete flora was determined for five randomly selected sites within those basins. One hundred and thirty alien plant species were found across the 80 sampling sites, representing 21% of the recorded total flora. At site scale, the level of plant invasion, measured as alien richness (AR) and relative alien richness (RAR), was assessed in relation to a set of explanatory variables by means of Generalised Linear Mixed Models. This level of invasion was influenced by environmental variables such as the thermicity index, the average riverbed width and the number of plant communities and by human‐related variables such as the distance to the nearest town and the proportion of surrounding urban land. At basin scale, industrialised river basins were more heavily invaded than non‐industrialised basins, and they both differed in their alien plant composition. Given that some of the alien species occurring in Cantabrian streams are specially abundant (Crocosmia x crocosmiiflora) and/or form very dense stands (Fallopia japonica, Paspalum distichum), future research should focus on the drivers that influence the presence and distribution of these species of special concern. Copyright © 2016 John Wiley & Sons, Ltd.     

北京地区鬼针草属传播机制初探

利用扫描电子显微镜对北京地区7种鬼针草属植物的果实形态进行了对比观察研究,旨在为其系统分类和鉴定提供新的资料和证据。更重要的是,首次对7种鬼针草属植物瘦果的果体、芒刺和倒刺毛的相应特征进行了测量,用软件进行仿真,建立数学模型,并进行果实传播的受力分析,旨在为今后对其进行更有效的防控提供科学依据。果实数学模型和受力分析显示,7种鬼针草属植物中可承受力最大的是三叶鬼针草,最小的是金盏银盘。三叶鬼针草最具有潜在传播性,相关部门应重点对其进行研究防控。     

外来物种入侵的国际法问题探析

生物入侵现已与动植物生境丧失、全球变化并列为影响生物多样性的三大问题。本文在倡导风险预防原则、信息公开和公众参与原则、国际合作的基础上,总结国际法律文件中有关生物入侵的规定,为我国提出了一些有益的立法建议。     

生活中的绿色与环境教育课题

了解环境并对我们熟悉的环境产生兴趣,对于察知环境问题并采取恰当的行动非常重要。本文涉及作者以往参与的几个研究实例,介绍关于身边自然环境和农作物的知识、认知、经验。在对花草游憩活动的调查中表明,人们使用植物进行的活动逐渐减少。对于外来植物的调查显示,许多人无法识别外来植物。在一项父母对于蔬菜的态度和经验的调查中表明,能够自发栽种蔬菜的人并不多,而父母对蔬菜的经验和意识可能会影响他们的孩子。基于上述结果得出,自然体验活动需要成年人提供适当的支持,并且有必要在家庭和社区中增加成年人的参与机会。     

Effects of hydrologic infrastructure on flow regimes of California's Central Valley rivers: Implications for fish populations

Alteration of natural flow regimes is generally acknowledged to have negative effects on native biota; however, methods for defining ecologically appropriate flow regimes in managed river systems are only beginning to be developed. Understanding how past and present water management has affected rivers is an important part of developing such tools. In this paper, we evaluate how existing hydrologic infrastructure and management affect streamflow characteristics of rivers in the Central Valley, California and discuss those characteristics in the context of habitat requirements of native and alien fishes. We evaluated the effects of water management by comparing observed discharges with estimated discharges assuming no water management (‘full natural runoff’). Rivers in the Sacramento River drainage were characterized by reduced winter–spring discharges and augmented discharges in other months. Rivers in the San Joaquin River drainage were characterized by reduced discharges in all months but particularly in winter and spring. Two largely unaltered streams had hydrographs similar to those based on full natural runoff of the regulated rivers. The reduced discharges in the San Joaquin River drainage streams are favourable for spawning of many alien species, which is consistent with observed patterns of fish distribution and abundance in the Central Valley. However, other factors, such as water temperature, are also important to the relative success of native and alien resident fishes. As water management changes in response to climate change and societal demands, interdisciplinary programs of research and monitoring will be essential for anticipating effects on fishes and to avoid unanticipated ecological outcomes. Published in 2009 by John Wiley & Sons, Ltd.