How do small birds evolve in response to climate change? Data from the long‐term record at La Brea tar pits     

Katherine L. LONG  Donald R. PROTHERO  Valerie J. P. SYVERSON 《Integrative zoology》2020,15(4):249-261

Biology textbooks describe the small changes in the beaks of the Galápagos finches as exemplars of how birds evolve in response to environmental changes. However, recent studies of the abundant fossil birds at Rancho La Brea find no evidence of evolutionary responses to the dramatic climate changes of the glacial–interglacial cycle over the past 35 000 years: none of the large birds exhibit any change in body size or limb proportions, even during the last glacial maximum approximately 18 000–20 000 years ago, when the southern California chaparral was replaced by snowy coniferous forests. However, these are all large birds with large ranges and broad habitat preferences, capable of living in many different environments. Perhaps the smaller birds at La Brea, which have smaller home ranges and narrower habitats, might respond to climate more like Galápagos finches. The only 3 common small birds at La Brea are the western meadowlark, the yellow‐billed magpie and the raven. In this study, we demonstrate that these birds also show complete stasis over the last glacial–interglacial cycle, with no statistically significant changes between dated pits. Recent research suggests that the small‐scale changes over short timescales seen in the Galápagos finches are merely fluctuations around a stable morphology, and rarely lead to long‐term accumulation of changes or speciation. Instead, the prevalence of stasis supports the view that long‐term directional changes in morphology are quite rare. While directional changes in morphology occur frequently over short (<1 ka) timescales, in the long term such changes only rarely remain stable for long enough to appear in the fossil record.  相似文献   

桥梁建设对蓄滞洪区洪水演进影响的模拟与分析——以濛洼蓄洪区特大桥工程为例     

刘丽红  蒋鹏  温永帅 《水土保持通报》2022,42(2):150-156

[目的]分析涉水建筑物修建前后洪水演进过程的影响,为真实高效计算桥梁工程对蓄滞洪区洪水演进过程以及对蓄洪区防洪工作的有效开展提供科学支持。[方法]选取安徽省阜阳市濛洼蓄洪区为研究区,利用区域地形、水文数据、桥梁工程设计等最新资料,采用MIKE 21的非结构化水动力学模型,将进洪退洪过程作为整体对濛洼蓄洪区洪水演进过程进行实时模拟,分析桥梁工程建设对蓄滞洪区洪水演进分洪时间、流速分布、水位变化等特性的影响。[结果]桥梁工程修建后,桥位附近分洪历时比工程修建前最大滞后45 s,主流区流速分布范围为0.4～0.6 m/s,局部流速变化率最大7.409%,桥墩附近水位最大抬高值为0.006 m,水位最大变化率为-0.22‰。[结论]桥梁的建设延缓了蓄洪区行洪时间,抬高了桥墩附近水位,改变了工程附近流速分布,但对蓄洪区整体的影响较小,基本不影响濛洼蓄洪区的正常运行。  相似文献   

武汉城市圈乡村聚落空间格局演变及影响因素     

金丹  戴林琳 《水土保持研究》2022,29(6):383-390,398

为揭示乡村聚落空间格局演变特征及影响机理,以武汉城市圈为研究对象,综合运用空间韵律指数、平均最邻近指数、核密度分析等方法,从不同尺度定量识别了2009—2017年武汉城市圈乡村聚落的空间分布特征和演变规律,并探讨了乡村聚落空间格局演变的影响因素。结果表明:(1)2009—2017年,聚落总体规模增幅2.82%,平均斑块面积增幅1.45%,斑块形态趋于规则,破碎化程度较低,聚落单体布局形态多样化,规模扩张以点状、带状和块状扩张为主;(2)聚落空间保持集聚分布模式,单位面积乡村聚落消亡斑块较新生斑块核密度平均值低74.51%,聚落增减密度变化呈“北疏南密,向中心城区聚集”的特点,聚落局部以面积增加为主,新增聚落向各中心城区集聚;(3)聚落空间演变主要发生在低海拔、低坡度、降水量丰富、气候温暖、农村人口规模较高、经济发展水平较低的地区,并表现出明显的河流指向、道路指向、经济指向等特点。综上,武汉城市圈乡村聚落空间格局在规模形态和空间分布上均发生了演变,并受自然环境和社会人文等因素的影响。  相似文献   

Isotope implications of groundwater recharge,residence time and hydrogeochemical evolution of the Longdong Loess Basin,Northwest China     

LING Xinying  MA Jinzhu  CHEN Peiyuan  LIU Changjie  Juske HORITA 《干旱区科学》2022,14(1):34-55

Groundwater plays a dominant role in the eco-environmental protection of arid and semi-arid regions.Understanding the sources and mechanisms of groundwater recharge,the interactions between groundwater and surface water and the hydrogeochemical evolution and transport processes of groundwater in the Longdong Loess Basin,Northwest China,is of importance for water resources management in this ecologically sensitive area.In this study,71 groundwater samples(mainly distributed at the Dongzhi Tableland and along the Malian River)and 8 surface water samples from the Malian River were collected,and analysis of the aquifer system and hydrological conditions,together with hydrogeochemical and isotopic techniques were used to investigate groundwater sources,residence time and their associated recharge processes.Results show that the middle and lower reaches of the Malian River receive water mainly from groundwater discharge on both sides of valley,while the source of the Malian River mainly comes from local precipitation.Groundwater of the Dongzhi Tableland is of a HCO3-Ca-Na type with low salinity.The reverse hydrogeochemical simulation suggests that the dissolution of carbonate minerals and cation exchange between Ca²⁺,Mg²⁺and Na+are the main water-rock interactions in the groundwater system of the Dongzhi Tableland.Theδ¹⁸O(from-11.70‰to-8.52‰)andδ2H(from-86.15‰to-65.75‰)values of groundwater are lower than the annual weighted average value of precipitation but closer to summer-autumn precipitation and soil water in the unsaturated zone,suggesting that possible recharge comes from the summer-autumn monsoonal heavy precipitation in the recent past(≤220 a).The corrected 14C ages of groundwater range from 3,000 to 25,000 a old,indicating that groundwater was mainly from precipitation during the humid and cold Late Pleistocene and Holocene periods.Groundwater flows deeper from the groundwater table and from the center to the east,south and west of the Dongzhi Tableland with estimated migration rate of 1.29-1.43 m/a.The oldest groundwater in the Quaternary Loess Aquifer in the Dongzhi Tableland is approximately 32,000 a old with poor renewability.Based on theδ¹⁸O temperature indicator of groundwater,we speculate that temperature of the Last Glacial Maximum in the Longdong Loess Basin was 2.4℃-6.0℃ colder than the present.The results could provide us the valuable information on groundwater recharge and evolution under thick loess layer,which would be significative for the scientific water resources management in semi-arid regions.  相似文献   

果树全基因组测序研究进展   总被引：3，自引：0，他引：3  

乔鑫  李梦  殷豪  李雷廷  吴俊  张绍铃 《园艺学报》2014,41(1):165-169

 回顾了葡萄、番木瓜、苹果、香蕉、梨、甜橙等10 种果树的全基因组测序的发展历程,基 于全基因组测序结果探讨了不同果树的起源进化,并对果树全基因组测序的后续研究进行了概述,进一 步讨论了果树全基因组测序面临的挑战以及今后的研究重点。  相似文献   

Current conservation genetics: building an ecological approach to the synthesis of molecular and quantitative genetic methods   总被引：2，自引：1，他引：2  

P. Moran 《Ecology of Freshwater Fish》2002,11(1):30-55

Abstract Although neutral molecular markers have long been important tools for describing genetic variation in threatened fish species, many of the most critical questions in conservation relate more to quantitative genetic variation than to neutral markers. Quantitative genetic studies are typically expensive and time-consuming to conduct, especially in some of the long-lived vertebrates of conservation concern. The present review of recent literature in fish conservation genetics examines the traditional role of molecular studies in describing conservation units and providing indirect inference about local adaptation and adaptive potential. Of special interest are approaches that use a combination of molecular and quantitative genetic methods. Such studies are likely to provide important new insights into many conservation-related problems. The review also explores how increasing interest in non-neutral molecular markers is contributing to our understanding of the geographic scale and evolutionary importance of local adaptation in threatened populations. It is increasingly clear that advanced genetic technologies for the exploration of neutral and non-neutral molecular variation are leading to a fundamental shift in the way complex phenotypic traits are studied. This new synthesis of methods will have dramatic implications for fish conservation genetics and biology in general.  相似文献   

桃李梅杏四种核果类植物亲缘关系的研究Ⅱ．染色体核型及Giemsa显带的异同点   总被引：2，自引：0，他引：2  

魏文娜  唐前瑞 《湖南农业大学学报(自然科学版)》1996,(3)

桃、李、梅、杏４种核果类植物的染色体核型及Ｇｉｅｍｓａ显带的研究结果表明，上述４种核果类植物，体细胞染色体均为２ｎ＝１６，核型的着丝点也是相似的，但染色体的长度和显带分类的频数表现出差异。分析结果认为，桃为进化型，李为原始型，梅、否之间亲缘关系较近。  相似文献   

布鲁菌进化和分类学研究进展     

钟志军  于爽  徐杰  王玉飞  白耀霞  陈燕芬  付思美  王同坤  汪舟佳  杜昕颖  彭广能  黄克和  陈泽良 《兽医大学学报》2011,(8):1228-1235,1240

布鲁菌属革兰氏阴性兼性胞内寄生菌,能感染多种宿主动物和人。该属可分为6个典型种,包括羊种、牛种、猪种、沙林鼠种、绵羊附睾种以及犬种布鲁菌等。此分类是基于其致病性以及宿主偏好性的差异划分。尽管6个种通过传统表型试验能区分,但布鲁菌种内采用DNA-DNA杂交证明DNA同源性高度一致（相似性大于90%）。因此有人提议布鲁菌由单一种组成,即布鲁菌属中只有羊种布鲁菌,其他种都是羊种菌的生物亚型之一。然而基于其他分子技术的基因分型表明其DNA多态性表现明显,说明目前对这个种的分型还是比较准确。而最近分离的海洋种布鲁氏菌分离株（鳍型和鲸型）采用传统分型标准和一些特异的分子标记也证明这种分型比较正确。本文对目前布鲁菌种属进化和分类学进行综述,希望对研究其进化和分类有所帮助。  相似文献   

Climate change and weed adaptation: can evolution of invasive plants lead to greater range expansion than forecasted?     

D R CLEMENTS  A DITOMMASO 《Weed Research》2011,51(3):227-240

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甘蓝型油菜波里马雄性不育系的选育与研究   总被引：33，自引：5，他引：33  

傅廷栋  杨小牛 《华中农业大学学报》1989,8(3):201-207

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