我国道路对野生动物影响研究的现状与挑战

全球交通基础设施网络的不断扩张导致的栖息地丧失和破碎化已成为生物多样性下降的主要影响因素之一。国外开展了大量的道路对野生动物生存影响的研究, 相对而言, 我国在该领域的研究刚刚起步。本文通过总结截止于2021年国内的144篇案例研究文献以及新浪微博中210条道路交通伤害信息, 将我国道路对野生动物的影响分为栖息地丧失、栖息地破碎化、回避或聚集路边、阻碍或促进迁移、种群隔离、野生动物通道和道路交通伤害等方面, 从研究方法、研究地点、研究物种和研究结果等不同角度进行梳理和总结。近年来, 我国的相关研究呈现不断增长的趋势, 研究地点主要集中在可可西里、长白山和秦岭地区; 研究物种主要为青藏高原有蹄类、大熊猫(Ailuropoda melanoleuca)和亚洲象(Elephas maximus)。未来重点发展方向应包括: (1)道路野生动物基础数据采集平台建设; (2)我国不同动物地理分区的道路野生动物相关研究; (3)深入开展学科交叉与部门合作以及国际交流合作。公众在社交媒体发布的相关信息表明近年来公众对道路交通伤害问题越来越关注, 未来开展基于公民科学收集道路交通伤害数据具有迫切性和可行性。     

A southern California freeway is a physical and social barrier to gene flow in carnivores

Roads present formidable barriers to dispersal. We examine movements of two highly mobile carnivores across the Ventura Freeway near Los Angeles, one of the busiest highways in the United States. The two species, bobcats and coyotes, can disappear from habitats isolated and fragmented by roads, and their ability to disperse across the Ventura Freeway tests the limits of vertebrates to overcome anthropogenic obstacles. We combine radio-telemetry data and genetically based assignments to identify individuals that have crossed the freeway. Although the freeway is a significant barrier to dispersal, we find that carnivores can cross the freeway and that 5-32% of sampled carnivores crossed over a 7-year period. However, despite moderate levels of migration, populations on either side of the freeway are genetically differentiated, and coalescent modelling shows their genetic isolation is consistent with a migration fraction less than 0.5% per generation. These results imply that individuals that cross the freeway rarely reproduce. Highways and development impose artificial home range boundaries on territorial and reproductive individuals and hence decrease genetically effective migration. Further, territory pile-up at freeway boundaries may decrease reproductive opportunities for dispersing individuals that do manage to cross. Consequently, freeways are filters favouring dispersing individuals that add to the migration rate but little to gene flow. Our results demonstrate that freeways can restrict gene flow even in wide-ranging species and suggest that for territorial animals, migration levels across anthropogenic barriers need to be an order of magnitude larger than commonly assumed to counteract genetic differentiation.     

Are wildlife escape ramps needed along Australian highways?

Road escape ramps are structures developed in the USA to enable large mammals that become trapped on the roadside of a wildlife fence to escape the road and avoid vehicle collision. They are now commonly installed in eastern Australia to enable the Koala (Phascolarctos cinereus) and other fauna to escape through a roadside exclusion fence and return to the forest. We investigated the use of seven of 14 escape ramps over three years on the Oxley Highway at Port Macquarie in New South Wales. The Swamp Wallaby (Wallabia bicolor) was the most frequently detected species, traversing the escape ramps on 502 occasions, followed by bandicoots (Isoodon macrourus and Perameles nasuta) on 148 occasions. Various other species were detected but no Koalas. Swamp Wallabies moved through the escape ramps in the reverse direction (i.e. towards the road) in 53% of detections of that species and bandicoots in 14% of their detections. There was no obvious pattern by these species of proportionately higher use of ramps closer to the end of the exclusion fences. The large number of reverse passages through the escape ramps reveals a poor design of these structures. Trials with taller ramps are required to determine how to minimise reverse passages. Concurrent monitoring of three underpasses detected numerous crossings by large mammals including Swamp Wallabies, and some crossings by Koalas. We believe evidence is needed to demonstrate the necessity for escape ramps along Australian highways.     

Freshwater fishes of the Burdekin River, Australia: biogeography, history and spatial variation in community structure

Spatial variation in freshwater fish community structure in a large, structurally monotonous sub-tropical Australian river over 1989–1992 is described. The number of species collected (25) over the period of study, was low, given the large size of the river's catchment. The low diversity of fishes present in the river was suggested to be due to a combination of factors including the imposition of an ancient downstream barrier to fish movement (the Burdekin Falls), substantial volcanic activity during the late Tertiary, past climatic stress and little variation in habitat structure over the range of sites examined. Notwithstanding the low species richness, the Burdekin River's freshwater fish fauna is distinctive, containing elements of the fauna of both eastern and northern Australia, and this was suggested to reflect aspects of ancient landscape evolution. Spatial variation in fish community structure was most strongly influenced by the presence of the Burdekin Falls (the present site of a very large reservoir) and secondarily by minor differences in habitat structure of main channel and tributary streams.     

随机分布条件下种群空斑对点格局分析结果的影响

点格局分析是种群格局研究过程中最重要、最常用的方法。种群空斑是影响点格局分析结果的重要因素;其对点格局分析结果的影响关乎种群格局研究结论的可靠性;因此;探讨空斑如何影响点格局分析结果具有重要意义。以随机分布格局为对象;在5 m×5 m的研究区域内;通过模拟实验设置低、中、高3种密度;选择具有累积效应的K(r)函数和去除累积效应的成对相关函数g(r);在非屏蔽与屏蔽2种情况下;探讨空斑面积的变化如何影响点格局分析结果。结果表明:（1）随着空斑半径的增加;无论K(r)函数还是g(r)函数;在3种密度条件下;空斑达到一定面积时;开始对点格局分析结果产生影响:种群格局由原来的随机分布1种格局类型经过2种格局类型的过渡后转变为3种格局类型共存;（2）空斑对点格局分析结果的影响;K(r)函数和g(r)函数之间存在差异;（3）空斑对点格局分析结果的影响;对于同一分析方法;不同密度条件下;亦存在一定差异;（4）空斑对点格局分析结果的影响;可以通过屏蔽空斑加以规避;且K(r)函数的规避效果比g(r)函数好。     

公路建设的主要生态影响

公路已成为全球景观中一种重要的景观类型,其里程和密度在逐年增加.公路建设项目,尤其是公路网络的形成不仅减少了自然生境的数量,而且严重降低了自然生境的质量.公路建设对生态环境造成的影响主要包括生境损失、生态干扰、公路致死、阻碍作用、廊道效应以及公路网络造成的严重生境破碎化.缓解公路生态影响的措施有避免、消减和补偿3种.     

梭梭种群不同发育阶段的空间格局与关联性分析

运用点格局法中的Ripley'sK(r)函数的变形L(r)函数和g(r)函数,对古尔班通古特沙漠不同生境下不同发育阶段梭梭种群的空间格局及关联性进行了研究。结果表明:L(r)函数显示梭梭种群格局倾向于聚集分布,且集中分布在0-25m尺度范围内,而g(r)函数分析在小于3m的尺度上呈聚集分布,大于3m的尺度后波动较小,最大聚集尺度表现在0-10m范围内;梭梭在不同发育阶段过程中,L(r)和g(r)函数都显示由幼苗、幼树的聚集分布变为成年树的随机分布,甚至在某些尺度上变为均匀分布,同时幼苗幼树向成年树过渡过程中,梭梭的聚集强度呈逐渐减弱趋势。在关联性分析中,L(r)函数分析中正关联维持的尺度范围较g(r)函数大。L(r)函数分析幼苗与幼树、成年树在0-15m尺度内呈现正关联,g(r)函数在0-5m范围内表现为正关联,而幼树与成年树在0-10m尺度内多呈负关联,且两个大小级的形体大小差异越大,它们的正关联关系越弱,甚至表现为负关联或无关联。幼苗幼树的聚集分布和正关联是梭梭种子的传播和密度制约的一个平衡,对梭梭种群的生存和发展是有利的。另外,梭梭种群分布格局的强度在不同地形也存在差异,奎屯平地比五家渠的聚集强度和关联性大,缓坡差异较小,这说明地形对各种资源的再分配间接地影响了梭梭的格局。总体上看,同时应用L(r)和g(r)函数进行梭梭空间格局与关联性分析时结果不尽相同。L(r)函数的最大值可以反映典型的聚集尺度,而g(r)函数中出现的第1个最大值可以表示植株间典型距离。在小尺度下两种函数分析所得空间格局是一致的,而在大尺度上有较大差异。g(r)函数在小尺度范围内的分析结果更接近实际情况,有利于揭示出梭梭空间格局与生态过程有联系的\"关键尺度\",说明梭梭为了适应恶劣环境往往表现为聚集分布,这种聚集生长现象有利于个体的生存与繁衍。因此,联合使用L(r)函数和g(r)函数更有利于揭示植物个体间的关系。     

A spatial analytical approach for selecting reintroduction sites for burbot in English rivers

1. Availability of suitable habitat is a prerequisite for species reintroduction success, and to ensure population persistence, investigations of a species’ habitat utilisation throughout its life history should be conducted as part of a feasibility study. 2. Habitat utilisation models for burbot, Lota lota, developed using data from field studies conducted in France and Germany and information from the literature were used to assess the feasibility of reintroducing burbot into rivers of its former native range in eastern England. 3. Per cent tree roots, aquatic vegetation and flow types were important predictors of adult burbot abundance. Furthermore, the habitat utilisation models were supplemented with information from the literature, which suggested that off‐channel habitat such as wetlands and backwaters is important for spawning and nursery stages. 4. An assessment of the habitat availability in the rivers of the burbot’s former native range using variables related to spawning and nursery and adult life stages showed that although adult habitat was widely distributed, the availability of spawning and nursery habitat was less abundant, potentially limiting successful reestablishment. 5. Potential suitable habitat was concentrated in the central and southern areas of the species’ former English distribution. Overall, rivers of the burbot’s former range potentially afford suitable habitat to sustain a reintroduced population. However, sites should be preferentially selected on the basis of having appropriate spawning and nursery areas.     

Dinuclear nickel(II) and zinc(II) complexes of 2,6-bis[{bis(2-pyridylmethyl)amino}methyl]-4-methylphenol

Reaction of the symmetrical proligand H₂L with metal(II) acetate and a counteranion to promote crystallisation has given the homodinuclear complexes [Zn₂L(OAc)₂](BF₄)]·2MeOH and [Ni₂L(OAc)₂](BF₄)]·2MeOH the crystal structures of which are reported. These show the presence of a triply bridging (μ-cresolato)bis(μ-carboxylato) dimetal core.