Phylogeography of the Australian freshwater turtle Chelodina expansa reveals complex relationships among inland and coastal bioregions

We examined range‐wide mitochondrial phylogeographical structure in the riverine freshwater turtle Chelodina expansa to determine whether this species exhibits deep genetic divergence between coastal and inland hydrological provinces, as seen in co‐distributed freshwater taxa. We sequenced two mitochondrial loci, genealogical relationships were assessed using a network approach, and relationships among biogeographical regions were tested using analyses of molecular variance. Population history was evaluated using neutrality tests, indices of demographic expansion, and mismatch analyses. Twenty‐one haplotypes were recovered across two mitochondrial haplogroups separated by approximately 4% nucleotide divergence. The haplogroups have discrete geographical boundaries but only partially support a hypothesis of deep divergence between coastal and inland bioregions. The first haplogroup comprises populations from the inland Murray‐Darling Basin and from coastal catchments south of the Mary River in south‐east Queensland. The second haplogroup comprises populations from coastal catchments north of the Mary River. Cryptic phylogeographical barriers separating adjacent coastal populations are congruent with those demonstrated for other freshwater taxa and may result from the combined influences of the Conondale Range and alluvial deposits at the mouth of the Mary River. The findings of the present study demonstrate that freshwater taxa commonly display genetic differentiation within a biogeographical region where no boundaries have been recognized, highlighting the need to uncover cryptic microbiogeographical regions to aid conservation of freshwater biota. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 789–805.     

RCPs气候情景下珠江三角洲地区城市用地扩展的预测与模拟

随着社会经济的快速发展,中国城市规模和数量不断扩大,城市土地利用系统内部变化错综复杂.本研究以珠江三角洲地区城市群为例,研究了在自然环境条件和社会经济条件共同作用下城市化进程中城市用地动态变化的驱动机制,并设计了规划情景和RCPs气候情景,运用决策树元胞自动机模型对这几种情景下珠江三角洲地区城市用地的动态变化进行预测模拟.结果表明: 非农业人口和社会经济的增长对城市化过程起着决定性的推动作用,交通干线在整个城市化进程中始终起着重要的基础性作用,高程较高和坡度较大的区域制约了该地区的城市化进程.随着时间的推移,无论哪种情景,城市用地扩张的态势不变,但扩张速度到一定时间节点将会减缓,不同情景下减缓的时间点不同;规划情景、MESSAGE模式和AIM模式下的城市用地发展速度依次增加,但MESSAGE气候模式下的城镇发展较符合当前的城镇发展态势;城市用地扩张的区域主要集中在广州、东莞、佛山、珠海、深圳、湛江和潮汕等城市化相对较高的区域.
     

桂林漓江沿岸植物区系特点及其与景观的关系

桂林漓江沿岸原生植被受破坏严重 ,植物区系为次生性质 ,其特点 :( 1 )种类丰富 ,共有野生维管束植物 80 8种 ,隶属于 1 5 6科、483属 ;( 2 )植物区系的地理成份复杂 ,可将 45 4个种子植物属归为 1 4个类型 ,以热带、亚热带类型为主 ,温带类型次之 ,中国特有属 6个 ;( 3 )植物区系岩溶特性明显 ,属于东亚植物区、中国—日本森林植物亚区、岭南山地地区的一个小区。植物景观是桂林漓江沿岸风景的重要组成部分 ,具体表现在各类植物群落的外貌和一些重要植物种类的花、果和叶色的季节性变化上。现存的主要植物群落以次生藤刺灌丛为主 ;少见尚存的喀斯特常绿、落叶阔叶混交林 ;独有的喀斯特硬叶常绿阔叶林 :以乌冈栎为建群种的山顶矮林 ,是我国东部湿润亚热带地区罕见的残遗植被类型 ,在构成景观和科研上均有特殊意义。沿河岸分布的植物是最吸引游人注意的重要景观 ,形状各异的灌丛、杂木林、竹林和农田植被等都是风景的重要组成部分     

Variations in levels of clonality among Populus nigra L. stands of different ages

The evolution of genotypic diversity with population age remains poorly explored in clonal plant populations despite the potential for important shifts to occur through the course of time. Woody sprouting species are particularly under-represented in studies investigating intra-specific variations in levels of clonality from one locality to the next and through time. In this study we sought to determine the incidence and frequency of replicate genotypes in natural Populus nigra L. (Salicaceae) stands of different ages. Ten stands of this woody riparian sprouting species were selected in each of three distinct age groups (young, middle-aged and old) along a 30 km stretch of the River Garonne (south-west France). Leaf samples were collected from 15 neighbouring trees in each stand (450 samples in total) and replicate genotypes were identified using five SSR markers. Replicate genotypes were identified in two-thirds of all stands sampled (i.e. 50 of young stands, 100 of middle-aged stands and 50% of old stands). Young stands had significantly fewer replicated genotypes than middle-aged or old stands, while middle-aged stands had the greatest number of replicated genotypes. Replicate genotypes were most often found to occur as nearest neighbours and formed relatively small, discrete units (i.e. 2–4 trees growing in close proximity to one another). This suggests that asexual regeneration frequently occurs through flood-training in this species, although asexual regeneration from translocated fragments also evidently occurs as evidenced by 11 cases of replicate genotypes occurring in widely separated stands (up to 19 km apart). The results of this study highlight the need for a hierarchical sampling strategy in space and across age groups for an accureate understanding of the genotypic structure of woody sprouting species populations. Conservation and management of effective population sizes will benefit from better insight into not only spatial, but also temporal variations in levels of genotypic diversity.Co-ordinating editor: J. Tuomi     

用硅藻群集指数(DAIpo)和河流污染指数(RPId)评价珠江广州河段的水质状况

用硅藻计于1990年采集珠江广州河段的9个采样点的附着硅藻群落．共得硅藻24个属,170个分类单位,其中,适腐性种8个,广腐性种84个,仍腐性种78个．群落相似性聚类分析表明,位于前、后航道中部的员村（st3）,新造（st8）,沙浴村（si10）三点的硅藻群落结构是为相似,向上,下游相似性逐渐减小．用硅藻群集指数（DAIpo）和河流污染指数（RPId）对各采样断面的水质进行分析表明：大盛（st12）和莲花山（st5）两点受污染最轻,属β-寡污带,黄沙点（st2）污染最严重,属α-中污带．对照点鸦岗（St1）也受到一定的污染,属α-寡污带,其它点的污染程度在α-寡污带与β-中污带之间．DAIpo值与BODS存在着显著的负相关（r＝0．86）．珠江广州河段的前、后航道的污染程度相差不大（RPId=56．42,56.26）,均属中度污染．     

海河流域生态功能区划

从海河流域自身的特征出发,运用RS、GIS技术,采用定性和定量分析相结合的方法,对海河流域生态功能区进行划分.结果表明:海河流域可划分为5个生态区、24个生态亚区和114个生态功能区;以流域尺度上占主导地位的4项生态功能(水源涵养、水土保持、防风固沙和生物多样性保护)为依据,确定了对海河流域具有重要意义的11个重要生态功能区域.该区划结果明确了对海河流域生态安全具有重要意义的区域,可用于指导海河流域自然资源的有序开发利用和产业的合理布局,为海河流域生态环境保护提供了科学依据,对维护海河流域生态安全具有重要意义.     

喀麦隆咯贝河中几种星形丝孢真菌的鉴定

从喀麦隆南部咯贝河入海处鉴定出6种链状分生孢子真菌,分别为灯芯草水枝孢Dendrosporajuncicola, 具缢链趾孢Phalangispora constricta Nawawi, 纳瓦链趾孢 P. nawawii, 具柄旋生孢Speiropsis pedatospora, 形旋生孢S. scopiformis, 连合韦氏孢Wiesneriomyces conjunctosporus。另有2类星形分生孢子归到枝孢属Dendrospora,但未鉴定到种。咯贝河的星形分生孢子真菌与来自马来西亚及其它热带地区的种类相似。     

伊洛河流域外来草本植物分布格局

外来生物入侵及其防治已经成为生态学关注的重点和热点问题.目前的研究主要集中在外来入侵种上,然而入侵种仅占外来种中很少一部分,因此,研究外来种现有分布格局对研究生物入侵及其防治有重要意义.以伊洛河流域草本植物群落中的外来种为对象,沿河从河源地到入黄河口选取典型样地,在调查流域内草本植物群落中物种组成的基础上选取外来种,并对外来种种类组成及其分布格局进行研究.结果表明:流域内有外来草本植物27种,分属于15科,种类较多的科为菊科、苋科和豆科;引入方式以有意引种为主.流域横向不同生境间,河滩地在水流的养分富集、季节性洪水物理干扰及人为活动扰动作用下,呈现出受外来种分布较多,而受人类活动扰动最强且营养丰富的农田分布较小的分布格局;纵向环境梯度下,上游河源山地属于自然植被区,人为干扰较轻,且受外来种影响较小;中游丘陵区从自然生态系统向农业生态系统的过渡区域,人类活动的扰动有所加强;下游平原农业区,人类活动强烈,区域内以人工生态系统为主,群落物种组成简单但受外来种影响最大,受自然环境和人类活动的双重影响.不同物种在不同生境间差异明显,其中,小蓬草、钻叶紫菀和反枝苋广泛分布于3种生境中.总体上,伊洛河外来草本植物分布格局在自然因素的基础上强烈受人为因素的影响,呈现出从上游到下游逐渐增多的趋势.     

基于传统生态智慧的江南水网空间韧性机制及实践启示

传统江南水网空间是一种典型的社会—生态系统,人文社会系统和自然生态系统之间的良性互动对于其韧性构建有着重要的积极作用。基于柯林斯等人提出的压力—冲击动态（PPD）模型,以平江府为典型代表,研究传统江南水网空间如何通过生态系统服务的桥梁搭建水网物质空间与人类社区发展之间的联系,从而厘清社会—生态系统在此过程中如何培育、优化和提升江南水网空间韧性。在此基础上,创新性地从生态系统服务供需关系的角度提出社会—生态韧性构建的生态智慧,并倡导以恢复力、适应力与变革力韧性机制培育为导向的、江南地区构建现代社区实践的若干启示,旨在引导江南水网空间实现具有韧性的社会—生态系统转型发展。