针对Gradient vector field Snakes模型轮廓线需人工初始化的问题及GVF场强分布不合理所导致的模型效率低下和角点定位精度低的问题,在分析GVF场强分布和模型迭代变形原理的基础上,改进原始GVF Snakes模型:模型以SUSAN算法提取的边缘点...针对Gradient vector field Snakes模型轮廓线需人工初始化的问题及GVF场强分布不合理所导致的模型效率低下和角点定位精度低的问题,在分析GVF场强分布和模型迭代变形原理的基础上,改进原始GVF Snakes模型:模型以SUSAN算法提取的边缘点集构建GVF Snakes模型的初始化轮廓线;并依据图像SUSAN边缘线和模型迭代变形原理局部修正和整体调整GVF场强分布,以符合模型高效迭代变形和对角点、细边缘精确定位的需要。理论分析和实验结果表明,改进GVF的自动Snakes模型提高了模型的计算效率,对细边缘和角点有更高的定位精度。展开更多
Influenced by rapid changes in climate and landscape features since the Miocene,widely distributed species provide suitable models to study the environmental impact on their evolution and current genetic diversity.The...Influenced by rapid changes in climate and landscape features since the Miocene,widely distributed species provide suitable models to study the environmental impact on their evolution and current genetic diversity.The dice snake Natrix tessellata,widely distributed in the Western Palearctic is one such species.We aimed to resolve a detailed phylogeography of N.tessellata with a focus on the Central Asian clade with 4 and the Anatolia clade with 3 mitochondrial lineages,trace their origin,and correlate the environmental changes that affected their distribution through time.The expected time of divergence of both clades began at 3.7 Mya in the Pliocene,reaching lineage differentiation approximately 1 million years later.The genetic diversity in both clades is rich,suggesting different ancestral areas,glacial refugia,demographic changes,and colonization routes.The Caspian lineage is the most widespread lineage in Central Asia,distributed around the Caspian Sea and reaching the foothills of the Hindu Kush Mountains in Afghanistan,and Eastern European lowlands in the west.Its distribution is limited by deserts,moun-tains,and cold steppe environments.Similarly,Kazakhstan and Uzbekistan lineages followed the Amu Darya and the Syr Darya water systems in Central Asia,with ranges delimited by the large Kyzylkum and Karakum deserts.On the western side,there are several lineages within the Anatolia clade that converged in the central part of the peninsula with 2 being endemic to Western Asia.The distribution of both main clades was affected by expansion from their Pleistocene glacial refugia around the Caspian Sea and in the valleys of Central Asia as well as by environmental changes,mostly through aridification.展开更多
The climatic niche is a central concept for understanding species distribution,with current and past climate interpreted as strong drivers of present and historical-geographical ranges.Our aim is to understand whether...The climatic niche is a central concept for understanding species distribution,with current and past climate interpreted as strong drivers of present and historical-geographical ranges.Our aim is to understand whether Atlantic Forest snakes follow the general geographical pattern of increasing species climatic niche breadths with increasing latitude.We also tested if there is a tradeoff between temperature and precipitation niche breadths of species in order to understand if species with larger breadths of one niche dimension have stronger dispersal constraints by the other due to narrower niche breadths.Niche breadths were calculated by the subtraction of maximal and minimal values of temperature and precipitation across species ranges.We implemented Phylogenetic Generalized Least Squares to measure the relationship between temperature and precipitation niche breadths and latitude.We also tested phylogenetic signals by Lambda statistics to analyze the degree of phylogenetic niche conservatism to both niche dimensions.Temperature niche breadths were not related to latitude.Precipitation niche breadths decreased with increasing latitude and presented a high phylogenetic signal,that is,significant phylogenetic niche conservatism.We rejected the tradeoff hypotheses of temperature and precipitation niche breadths.Our results also indicate that precipitation should be an important ecological constraint affecting the geographical distribution of snake lineages across the South American Atlantic Forest.We then provide a general view of how phylogenetic niche conservatism could impact the patterns of latitudinal variation of climatic niches across this biodiversity hotspot.展开更多
基金国家自然科学基金(the National Natural Science Foundation of China under Grant No.60277101No.60301003+2 种基金No.60431020)北京市教委面上项目(No.KM200410005030)北京市基金(No.3052005)资助。
基金supported by the Slovak Research and Development Agency under the contract APVV-19-0076 and by the grant VEGA 1/0242/21 of the Scientific Grant Agency of the Slovak RepublicSH was supported by the German Research Foundation(DFG,grant no.HO 3792/8-1)The work of OK was carried out within the framework of research topics of the state assignments nos.121032300023-7 and 122031100282-2.The research of DJ in Afghanistan has been approved by the National Environmental Protection Agency of the Islamic Emirate of Afghanistan(permits for access to genetic resources nos.12429 and 12455).
文摘Influenced by rapid changes in climate and landscape features since the Miocene,widely distributed species provide suitable models to study the environmental impact on their evolution and current genetic diversity.The dice snake Natrix tessellata,widely distributed in the Western Palearctic is one such species.We aimed to resolve a detailed phylogeography of N.tessellata with a focus on the Central Asian clade with 4 and the Anatolia clade with 3 mitochondrial lineages,trace their origin,and correlate the environmental changes that affected their distribution through time.The expected time of divergence of both clades began at 3.7 Mya in the Pliocene,reaching lineage differentiation approximately 1 million years later.The genetic diversity in both clades is rich,suggesting different ancestral areas,glacial refugia,demographic changes,and colonization routes.The Caspian lineage is the most widespread lineage in Central Asia,distributed around the Caspian Sea and reaching the foothills of the Hindu Kush Mountains in Afghanistan,and Eastern European lowlands in the west.Its distribution is limited by deserts,moun-tains,and cold steppe environments.Similarly,Kazakhstan and Uzbekistan lineages followed the Amu Darya and the Syr Darya water systems in Central Asia,with ranges delimited by the large Kyzylkum and Karakum deserts.On the western side,there are several lineages within the Anatolia clade that converged in the central part of the peninsula with 2 being endemic to Western Asia.The distribution of both main clades was affected by expansion from their Pleistocene glacial refugia around the Caspian Sea and in the valleys of Central Asia as well as by environmental changes,mostly through aridification.
基金Fundação de AmparoàPesquisa do Estado de São Paulo(FAPESP procs.2008/50068-2,2014/23677-9 and 2020/12658-4)Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq,405447/2016-7)RJS thanks CNPq for the research fellowship(312795/2018-1).
文摘The climatic niche is a central concept for understanding species distribution,with current and past climate interpreted as strong drivers of present and historical-geographical ranges.Our aim is to understand whether Atlantic Forest snakes follow the general geographical pattern of increasing species climatic niche breadths with increasing latitude.We also tested if there is a tradeoff between temperature and precipitation niche breadths of species in order to understand if species with larger breadths of one niche dimension have stronger dispersal constraints by the other due to narrower niche breadths.Niche breadths were calculated by the subtraction of maximal and minimal values of temperature and precipitation across species ranges.We implemented Phylogenetic Generalized Least Squares to measure the relationship between temperature and precipitation niche breadths and latitude.We also tested phylogenetic signals by Lambda statistics to analyze the degree of phylogenetic niche conservatism to both niche dimensions.Temperature niche breadths were not related to latitude.Precipitation niche breadths decreased with increasing latitude and presented a high phylogenetic signal,that is,significant phylogenetic niche conservatism.We rejected the tradeoff hypotheses of temperature and precipitation niche breadths.Our results also indicate that precipitation should be an important ecological constraint affecting the geographical distribution of snake lineages across the South American Atlantic Forest.We then provide a general view of how phylogenetic niche conservatism could impact the patterns of latitudinal variation of climatic niches across this biodiversity hotspot.
