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从1 2S rRNA基因序列探讨8种鳄类的系统学关系 总被引:8,自引:0,他引:8
测得扬子鳄(Alligator sinensis)和暹罗鳄(Crocodylus siamensis),的mtDNA12SrRNA基因片段的部分序列,与GenBank中的2种鳄及文献中4种鳄的12SrRNA基因相应片段,经比对后构建系统树。其结果显示,现存鳄类为单系起源,可划分为3个科,即:鳄科、食鱼鳄科和假食鱼鳄科。食鱼鳄与假食鱼鳄亲缘关系较近,支持将假食鱼鳄作为食鱼鳄科的一个属,与以形态学为基础的研究结果不同。在钝吻鳄科中,扬子鳄与凯门鳄亲缘关系较远,而与密西西比鳄的亲缘关系虽较近,但它们的确存在很多差异。两者12SrRNA基因序列差异达12.12%,碱基的颠换数为9。在基于碱基转换和颠换的NJ系统树及仅基于碱基颠换的NJ系统树中,前者支持扬子鳄与密河鳄间的亲缘关系较近,而后者支持扬子鳄与凯门鳄间的亲缘关系较近,说明扬子鳄与密河鳄间亲缘关系是值得研究的问题。因本文仅根据12SrRNA基因部分序列来进行分析的,尚需进一步研究。 相似文献
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关于扬子鱷研究的补充 总被引:1,自引:0,他引:1
鳄类起源于古生代而兴盛于中生代,距离今天已经有二百万万年,也就是在没有人类之前它已棲息在地球上了。长江下流一带古时称为扬子海峡,因此产生了扬子鳄的名称。世界上现存的鳄类有23种,大都分布在热带与亚热带地区,如南美、北美、南非、北澳、南亚等地,只有两种棲息于温带。扬子鳄在分类学上为鳄目、嚣科、嚣属。本属共有两种,一种产于北美密斯西比河流域,固名密斯西比鳄(Alligator mississpiensis);另一种即扬子鳄(Alligator sinensis Fauuel)。根据文献,汉口、九江、安庆、芜湖、镇江、苏州、上海等地都有记载,其可靠性如何尚待研究。此二种分布上的距离几乎有地球的半圈。 相似文献
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通过两个核基因NT-3基因(约740 bp)和BDNF基因部分序列(约720 bp)的分析,对爬行动物的系统发生关系中鳄类与鸟类和哺乳类系统发生关系、龟类在爬行动物系统发生中的位置以及扬子鳄属的划分等问题进行探讨.结果表明,在NT-3基因序列中,有307个位点存在变异(约为总位点数的47.3%),BDNF基因序列有256个变异位点(约为38.79%);构建的分子系统树显示,NT-3和BDNF基因以及两序列合并数据后所得系统树的拓扑结构均支持鳄类和鸟类聚为一支构成姐妹群,鳄类与蜥蜴类尽管在形态上非常相似,但它们的亲缘关系仍然较远;同时支持把龟鳖类作为鳄类和鸟类支系的姐妹群,支持把蜥蜴类(有鳞类)放在爬行类系统发生树的基部,而不是龟鳖类作为现代爬行类中最基部的1支.对扬子鳄分类地位的研究结果支持在现存的鳄类中扬子鳄与密西西比鳄的亲缘关系较近的结论. 相似文献
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扬子鳄是目前我国现存的唯一特产鳄种,被列为国家Ⅰ级重点保护野生动物,世界自然保护联盟(IUCN)更是将扬子鳄列为全球23种鳄鲁中最濒危的鳄类。 相似文献
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中国科学院发育生物学研究所莫鑫泉采用DNA复性动力学方法和DNA分子钟技术在扬子鳄起源和鳄类分子进化研究中,从分子水平上证实扬子鳄与密西鳄之间确曾有亲缘关系。他们从两者基因组结构的比较研究中,发现两者虽然在DNA序列种类复杂性的拷贝数上有较大差异,但总复杂性还是相似的。他们采用自己建立的DNA分子钟技术,测定了各物种从一个共同的祖先那里分枝以后的时间跨度,证明扬子鳄在3500万年前与泰国鳄有一个共同的祖先,在4500万年前与湾 相似文献
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The SOX genes form a gene family related by homology to the high-mobility-group (HMG) box region of the testis-determining gene, SRY. Using degenerate primer PCR, we have cloned and sequenced the HMG-box motif of CaSox4 gene from genomic DNA of the Chinese alligator, Alligator sinensis, a species closely related to American alligator, Alligator mississippiensis. Sequence comparison showed that CaSox4 gene shared 97% homology at the nucleotide level and complete identity at the amino acid level, respectively, with AES4 gene of Alligator mississippiensis. It indicates that the Sox4 gene has been extremely conserved during evolution. The result obtained in the present study strongly suggests that the Sox4 gene did not diverge during the differentiation of two closely related alligators, which are thought to have originated from a common ancestor and have existed largely unchanged for 200-250 Myr. 相似文献
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试论晚白垩世以来气候、地理等因素的变化对鼍类的进化及地理分布等影响 总被引:1,自引:0,他引:1
现存的鼍属只有两个种:即东亚的扬子鳄及北美的密河鳄。虽然这两个种的性质、纬度分布以及生态环境等都十分相似;但两者的水平分布的距离却几有地球的半圈。本文根据有关鼍类的进化、迁徙等的历史资料,对此进行了初步的探讨。 相似文献
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扬子鳄 (Alligatorsinensis)是中国特有的珍稀物种 ,其遗传资源的保护已受到广泛关注和重视。本文简要介绍了近年来有关扬子鳄在分子系统学、遗传多样性与种群遗传结构、线粒体基因组、个体识别以及性别决定方面的分子遗传学研究状况。 相似文献
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The complete mitochondrial genome of Alligator mississippiensis and the separation between recent archosauria (birds and crocodiles) 总被引:9,自引:0,他引:9
The complete mitochondrial genome of the alligator, Alligator
mississippiensis, was sequenced. The size of the molecule is 16,642
nucleotides. Previously reported rearrangements of tRNAs in crocodile
mitochondrial genomes were confirmed and, relative to mammals, no other
deviations of gene order were observed. The analysis of protein-coding
genes of the alligator showed an evolutionary rate that is roughly the same
as in mammals. Thus, the evolutionary rate in the alligator is faster than
that in birds as well as that in cold-blooded vertebrates. This contradicts
hypotheses of constant body temperatures or high metabolic rate being
correlated with elevated molecular evolutionary rates. It is commonly
acknowledged that birds are the closest living relatives to crocodiles.
Birds and crocodiles represent the only archosaurian survivors of the mass
extinction at the Cretaceous/Tertiary boundary. On the basis of
mitochondrial protein- coding genes, the Haemothermia hypothesis, which
defines birds and mammals as sister groups and thus challenges the
traditional view, could be rejected. Maximum-likelihood branch length data
of amino acid sequences suggest that the divergence between the avian and
crocodilian lineages took place at approximately equal to 254 MYA.
相似文献
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The Sox genes form a gene family related by homology to the high-mobility-group (HMG) box region of the testis-determining gene, SRY.Using degenerate primer PCR, we have cloned and sequenced the HMG-box motif ofCaSox4 gene from genomic DNA of the Chinese alligator,Alligator sinensis, a species closely related to American alligator, Alligator mississippiensis. Sequence comparison showed that CaSox4 gene shared 97% homology at the nucleotide level and complete identity at the amino acid level, respectively, withAES4 gene of A. mississippiensis. It indicates that the Sox4gene has been extremely conserved during evolution. The result obtained in the present study strongly suggests that theSox4 gene did not diverge during the differentiation of two closely related alligators, which are thought to have originated from a common ancestor and have existed largely unchanged for 200–250 Myr. 相似文献
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Yi-Quan Wang Wei-Quan Zhu Lei Huang Kai-Ya Zhou Ren-Ping Wang 《Biodiversity and Conservation》2006,15(9):2945-2955
Chinese alligator (Alligator sinensis) is one of the most critically endangered species among 23 extant crocodiles in the world. To prevent the extinction of the
species, a captive propagation started at early 1980s, and the total number of alligator was brought up to 10 thousands from
dozens of founder in 2000. But several genetic investigations showed those alligators were under an extremely low genetic
diversity status with few detectible polymorphic loci. To get more insight into its genetic diversity for the management of
captive Chinese alligator, AFLP was adopted to characterize variations in the population. Total of 347 bands were generated
from 47 individuals using 3 primer combinations, of which 203 (58.50%) were polymorphic, and 35 AFLP phenotypes were revealed
from those individuals. Comparing the results between RAPD and AFLP analysis on almost same sample set clearly indicated that
AFLP is more efficient in revealing polymorphic loci, especially in those populations with extremely low genetic diversity.
In present three assays, electrophoresis profile also displayed 3 individuals possessing very highly polymorphic AFLP phenotypes
that were never been found by RAPD and mtDNA D-loop sequencing, implicating that we should offer these individuals more breeding
opportunities to maintain the genetic diversity in the population and restrict those carrying few polymorphic loci from reproduction. 相似文献
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《亚洲两栖爬行动物研究(英文版)》2017,(4)
Oviparous female reptiles select nesting sites with optimal ecological factors that contribute to egg development. Chinese alligator(Alligator sinensis), an oviparous reptile, is a critically endangered crocodilian with temperature-dependent sex determination. Research on its nesting behavior may facilitate the protection of this species. In this study, we monitored nesting behavior over eight years. We compared selected frequency of nest sites, distance from nest site to water, height from nest site top to the water surface, distance from nest site to human activity region, and canopy density between nest sites on the island and bank. The results showed that 45 nest sites were used by female alligators over eight years and each site was selected from one to 10 times. The selected frequency of nest site occurrence on the island was higher than that on the bank(P 0.001). We observed that 88% of the individual alligators(15/17) showed different degrees of nest site fidelity. However, Chinese alligators might not always be loyal to only one nest site because of environmental changes or interspecific competition at nest sites. Our findings suggest that female alligators prefer to nest at island, which might be because of the nests on the island had a higher canopy density(P = 0.010) and were further from the human activity region(P 0.001) than those on the bank did. It would be beneficial to reduce human activities during the breeding season and protect the vegetation of Chinese alligator habitats in the future. of the beach(Ali et al., 2005; Kamel and Mrosovsky, 2005; Turkozan et al., 2012). Other species such as snakes and lizards select nest sites with more moist substrates, which significantly increases their body size at hatching(Brown and Shine, 2004; Reedy et al., 2013). Nest site preference may be maintained for one or more breeding seasons(Janzen and Morjan, 2001; Kamel et al., 2006). When female chose the same site or area during different years, it is called nest site fidelity(Switzer, 1993). This nest choice behavior may influence offspring survival(Lindeman, 1992) and nest site fidelity has been documented in numerous species such as birds(Lindberg and Sedinger, 1997), turtles(Mitrus, 2006; Walde et al., 2007), tuatara(Refsnider et al., 2010), and crocodilians(Elsey et al., 2008).Chinese alligator(Alligator sinensis) is a critically endangered freshwater crocodilian endemic to China(Thorbjarnarson and Wang, 1999). Recent investigations show that there are no more than 130 Chinese alligators 相似文献
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Chinese alligator (Alligator sinensis) is a rare and endangered species endemic to China. To better understand genetic details of the Chinese alligator genomic structure, a highly redundant bacterial artificial chromosome (BAC) library was constructed. This library consists of 216,238 clones with an average insert size of about 90kb, indicating that the library contains 6.8-fold genome equivalents. Subsequently, we constructed a 516kb contig map for the Chinese alligator olfactory receptor (OR) genes, which spans nine BAC clones, and subjected the BACs to full sequencing. The sequence analysis revealed that this contig contained 16 OR functional genes and meanwhile demonstrated that the nine BACs, which constituted the contig, overlapped correctly, proving the usability of this genome library. As a result, this BAC library could provide a useful platform for physical mapping, genome sequencing or complex analysis of targeted genomic regions for this rare species. 相似文献