The role of history vs. demography in shaping genetic population structure across an ecotone: chukar partridges (Alectoris chukar) as a case study

Recent advances in molecular ecology allow better assessment of the role of ecological and evolutionary processes in determining the dynamics of genetic diversity in natural populations. The chukar partridge ( Alectoris chukar ) is abundant and continuously distributed in the mesic Mediterranean regions of Israel, becoming scarce and patchily distributed in the arid Negev Desert. This demographic transition occurs across a main environmental transition, the Northern Negev ecotone. Populations of chukars along this gradient have been shown to differ from other populations in morphology, bilateral asymmetry, and in allozyme variation. The aim of this study is to infer whether historical (i.e. secondary contact of formerly vicariant populations) or recurrent demographic events (i.e. restriction to gene flow across the ecotone) have shaped the observed patterns of genetic diversity in chukar populations in Israel. We analysed mtDNA control-region sequences in 216 chukars collected from 28 localities (five distinct geographical regions). Results show that (1) average haplotype diversity is high ( h  = 0.93) while haplotype divergence is low (π= 0.8%), suggesting that extant populations diversified recently; (2) mtDNA gene diversity does not significantly differ across the distribution range; and (3) haplotype distribution differs among the sampling locations ( amova ; P  < 0.00031). Mantel test and autocorrelation analyses indicate that isolation-by-distance may explain the geographical partitioning of genetic diversity. These patterns have likely been produced by complex dynamics between past fragmentation of northern vs. intermediate and southern populations. Late Pleistocene climatic changes, fostering cycles of range contraction and expansion, may have led to genetic differentiation in allopatry, followed by restricted gene flow across secondary contact zones.     

环境因子对大石鸡种群遗传结构的影响

大石鸡是我国特有种 ,仅分布于青海东部 ,甘肃中部 ,宁夏六盘山以西 ,是我国北方干旱和半干旱荒漠环境指示鸟类。研究其遗传多样性与环境变化的关系 ,不仅是生态遗传学的前沿领域 ,而且在进化生物学和保护生物学领域都有重要的理论意义。采用聚合酶链式反应 ( PCR)和直接测序的方法 ,测定了甘肃境内由北向南的 5个大石鸡 ( Alectorismagna)种群 (兰州、榆中、定西、武山和礼县 )的线粒体 DNA( mt DNA)控制区 ( D-loop) 4 5 7～ 4 5 8个碱基长度的基因序列。结果表明兰州、榆中、定西、武山和礼县种群的平均碱基含量中 A( F=0 .30 F0 .0 1( 4 ,32 ) =3.97)、T( F=6 .4 4>F0 .0 1( 4 ,32 ) =3.97)差异极显著。 5个种群的基因变异率分别为 0 .32± 0 .2 7%、0 .4 8± 0 .4 5 %、0 .6 2± 0 .4 3%、0 .4 4± 0 .2 4 %、0 .1 7± 0 .1 4 % ,种群内的平均基因变异率为 0 .4 1± 0 .1 7% ,种群间的平均基因变异率为 0 .4 6± 0 .1 0 % ,种群内和种群间的平均基因变异率差异不明显( F=2 .5 90 .0 5 )和无霜期 ( r=-0 .81 0     

两种邻域分布石鸡间的线粒体DNA渗透

采用聚合酶链式反应(PCR)和mtDNA细胞色素b基因314 bp核苷酸序列测定等方法,证明在大石鸡与山石鸡的异域种群之间存在广泛的差异.然而采自六盘山地区与山石鸡相邻分布的大石鸡种群的样本中却存在山石鸡的mtDNA基因型,这种基因型与其它大石鸡个体的基因型有4.4%核苷酸差异.在与山石鸡相邻分布的大石鸡种群中有25%的个体具有山石鸡的mtDNA基因型,而采自六盘山接触地带以西约200 km处兰州市郊的大石鸡标本中则没有发现这种基因型.此发现支持山石鸡和大石鸡之间存在或曾经有过杂交的假设.作者还提出了一种限制性内切酶分析方法,可以快速地检测这种mtDNA基因型.在此之前还没有过关于山石鸡和大石鸡之间基因流动的报道.     

Digital imaging for colour measurement in ecological research

Traditional methods for colour quantification are complicated by the fact that colours change depending on illumination, and that different observers often perceive colours differently. Here we describe a new affordable method, which improves methods relying on human observers, to quantify patterns and colour variations. The procedure combines customized software with the use of digital cameras and commercial photofinishing software. The computer routines correct unavoidable illumination changes during image capturing, making all images comparable. Colours are quantified in a continuous scale of the conventional colour models developed for the human vision system, such as HSB, RGB, CMYK, or Lab, amenable for statistical analyses. We illustrate the use of this technique showing a previously unknown sexual dimorphism in the red-legged partridge, Alectoris rufa , undetectable with the unaided human eye. We also demonstrate that the digital system provides a finer discrimination than human observers for scoring the plumage of partridges belonging to two different subspecies. This method has potential applications in behavioural ecology, physiology, genetics, evolutionary biology, and taxonomy.     

Harvest of red-legged partridge in central Spain

A basic rule to attain sustainable use of harvested resources is to adjust take to availability. Populations of red-legged partridges in Spain have decreased in recent decades, and releases of farm-bred partridges to improve short-term availability are increasingly common. We used questionnaires and bird surveys to assess whether harvest was related to availability of wild partridges or intensity of farm-bred partridge releases. We studied 50 hunting estates, including 6 administratively labeled as intensive (with few numerical and temporal restrictions to releases). In addition, we considered hunting pressure (number of hunters × hunting days/km²) and habitat as explanatory variables in the analyses. In intensive estates, annual harvest was exclusively related to release intensity, indicating that in these estates hunting is detached from natural resources and approaches an industrial activity based on external inputs. In non-intensive estates, harvest was affected by wild stock availability, walked-up shooting pressure, and habitat (greater harvest in estates with more Mediterranean shrubland). In these estates, releases did not increase annual harvest, and can be considered an inefficient practice. Additionally, the relationship between abundance estimates and harvest disappeared in estates with low partridge abundance estimates, suggesting possibilities for overharvesting in a large proportion of estates. Increasing the abundance of wild red-legged partridge through techniques like habitat management, and improving the adjustment of harvest to availability, may be a good strategy to increase long-term harvest in non-intensive estates. Additionally, Government and managers must create ways to segregate and label the estates where only wild red-legged partridges are managed from those where releases are used, to reduce ecological costs of management decisions. © 2012 The Wildlife Society.