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1.
中国东北温带针阔混交林是暖温带植被与寒温带植被的交错区,是研究第四纪气候变化对遗传格局影响的关键区域。古植被重建研究显示,在末次冰盛期时,针阔混交林向南退缩至25°–30°N之间。然而,谱系地理研究则表明针阔混交林植物在末次冰盛期时可在35°N以北的一个或多个避难所中原地存活。长白山和朝鲜半岛是针阔混交林植物最重要的两个避难所,在其他区域还可能存在多个避难所,最北可达小兴安岭和俄罗斯远东地区。在避难所种群间冰期或冰期后发生扩张的过程中,形成了复杂的遗传多样性分布模式。单个避难所向北扩张的种群历史并不一定导致种群内遗传多样性随纬度升高而显著降低。在多个避难所模式下,种群内遗传多样性一般呈均匀分布。以往研究揭示了第四纪,尤其是末次冰盛期对针阔混交林植物进化历史的影响,但仍主要是乔木成分,且集中于单一物种。因此,东北和南方地区近缘种或姊妹种的适应性进化比较及针阔混交林的群落构建机制检验是未来研究的两个发展趋势。  相似文献   

2.
广布物种的地理分布范围涉及欧亚大陆地区,主要分为4种模式:全球分布模式、全北区分布模式、欧亚大陆中高纬度分布模式以及欧亚大陆中低纬度分布模式.通过比较近年来欧亚大陆广布种的谱系地理学的研究结果,总结得出三种谱系地理格局:(ⅰ)"单一组分"格局;(ⅱ)"东-西组分"格局;(ⅲ)"边域组分"格局.本研究分析了欧亚大陆广布种的谱系地理格局形成的成因,主要包括以下三个方面:(ⅰ)物种本身较强的环境耐受力和扩散能力,以及受到人类的贸易、运输、驯养活动的影响;(ⅱ)东-西相异的更新世冰期气候和内陆干旱带来的影响:欧洲在冰期期间大部分区域被冰盖覆盖,物种退到避难所,间冰期物种从避难所向适宜生存的区域扩张,扩张时间大致在末次冰盛期后;亚洲大部分地区的冰期气候相对较为温和,尤其是亚洲东部并没有被大范围冰川覆盖,冰期对这些地区生物的分布格局影响相对较小;此外,由于更新世青藏高原的快速隆升及亚洲夏季风的增强,促进了欧亚大陆内陆干旱带的形成,从而起到长期生态隔离的作用;(ⅲ)边域种化的影响:种群扩散至分布边缘新环境,由于地理或新环境隔离,遗传漂变在小的隔离种群中固定下来,种群间产生遗传分化.通过分析欧亚大陆广布物种在相同地理、地质历史事件下的应对机制的独特性与一致性规律,有助于深入了解广布种在欧亚大陆的地理种群演化及种系发生的形成机制,能够更好地总结、完善整个欧亚大陆生物物种的谱系地理格局的多样性和普遍规律.最后,从大规模核基因组标记的应用和基于物种的生活史特征的预测谱系地理学两个方面对欧亚大陆广布物种的谱系地理学研究提出了展望.  相似文献   

3.
通过分析比较近年来东亚第三纪孑遗植物的种群遗传学与亲缘地理学的研究结果,总结了它们的谱系地理格局式样,分析了其形成的共同地史或气候成因,并对未来的研究提出了展望。东亚孑遗植物的谱系地理式样主要表现为以下4个方面:(1)中新世中期至晚期的气候变冷变干驱使孑遗植物发生了近期的物种形成,而上新世末以及更新世的气候变化则促进了它们的种内谱系分化、遗传多样性形成以及种群的收缩与扩张,种群的收缩与扩张导致部分类群形成地理谱系"缝合带"。(2)由于不同的植物类群具有不同的生态位需求以及生物学特点,更新世冰期暴露的东海陆桥对中国–日本间断分布的孑遗植物具有不同的"过滤"与"廊道"效应,从而导致其呈现不同的遗传隔离式样。(3)上新世末青藏高原的快速隆升以及上新世末/更新世初东亚季风气候的加强可能是多个亚热带地区分布的孑遗植物沿四川盆地附近发生东西谱系分化的根本原因,也是西北干旱带分布的孑遗植物发生东西谱系分化的驱动因素。(4)自晚中新世以来的全球气候变冷变干驱使部分第三纪孑遗植物在更新世以前就已经从中国大陆或日本本岛迁入台湾,并发生隔离分化,形成了新的物种或地理谱系。总之,历史与当代的地理以及环境共同影响了东亚第三纪孑遗植物的地理分布、遗传多样性、谱系分化以及物种形成。最后,我们强调了目前由单位点的简单分子钟模型的运用造成的研究不足,并对未来的研究提出了展望,即基因组数据和生物地理模型的使用以及群落水平的整合亲缘地理学研究是未来的研究方向。  相似文献   

4.
以线粒体cyt b基因为分子标记,对长江上游干流及汉江等9条支流13个地理种群的大鳞马口鱼Opsariichthys macrolepis Yang et Huang进行遗传多样性及种群历史动态分析,并探讨其谱系生物地理学过程。结果显示,414尾大鳞马口鱼样本中共检测到79个单倍型,整体的单倍型多样性(h=0.930 1)和核苷酸多样性(π=0.129 421)均较高。基于单倍型构建的最大似然树和贝叶斯树显示,所有单倍型分为2个谱系(A和B),谱系A分布于中游支流汉江、清江,谱系B分布于长江上游干支流及沅江,表现出东-西方向的空间差异。分子钟估算显示,2个谱系于早更新世(~1.34 Ma)分化。不同地理种群间的遗传分化指数为-0.016 24~0.998 27,除个别种群外,多数地理种群呈现高度分化,说明种群间存在显著的遗传隔离。空间分子方差分析显示,大鳞马口鱼种群具有一定的遗传结构,特别是老鹤河、任河、清江地理种群分化显著。贝叶斯天际线分析显示,大鳞马口鱼各地理种群的扩张和收缩时间为0.01~0.04 Ma,可能与冰期-间冰期旋回有一定关联。推测青藏高原的隆升以及更新世冰期的更迭对长江中上游大鳞马口鱼的遗传分化以及种群动态产生了重大影响。  相似文献   

5.
黑鳍鳈(Sarcocheilichthys nigripinnis)为广泛分布于东亚地区的小型淡水鱼类,是生物地理学研究的良好材料。该研究以线粒体细胞色素b(Cyt b)基因序列为分子标记,对中国8个水系20个采样点的黑鳍鳈共142尾个体进行遗传变异及生物地理学过程分析。遗传多样性分析结果表明,142条Cyt b基因序列共检测出56个单倍型,总体单倍型多样性较高(h=0.971),而核苷酸多样性较低(π=0.0212),平均遗传距离较小(2.2%)。分子系统发育树结果表明,黑鳍鳈种群分为7个谱系,以秦岭为界可分为南、北两大支系,北方支系分化时间较早(谱系Ⅰ)而南方支系分化程度较高(谱系Ⅱ~Ⅶ)。该研究结果进一步揭示了克氏鳈(S.czerskii)的物种形成过程,估算其祖先在较晚近时期(~1.03 Ma)由黄河水系的黑鳍鳈分化而来。谱系生物地理学分析显示,黑鳍鳈的各地理种群表现为由北向南逐渐演化的趋势,地理隔离可能是限制该物种扩散和基因交流的主要原因。分子钟分析显示,分化时间发生于0.95~3.92 Ma。种群历史动态结果则推测黑鳍鳈经历过种群扩张,且该过程可能与更新世冰期与间冰期的更迭相关。  相似文献   

6.
青藏高原及其周边地区是世界上高山植物最丰富的地区,通过谱系地理学研究可以探讨高山植物演化历史与高原隆升和第四纪冰期的关系。根据对已经报道的36种高山植物的谱系地理分析,其谱系地理模式主要表现为:一、冰期退却到高原边缘的避难所,冰后期回迁到高原面;二、地理隔离造成冰期存在多处避难所(含微型避难所),冰后期发生局域性扩张。青藏高原在晚第三纪的快速隆升促进了物种的分化和成种,而第四纪冰期更是加剧了物种的快速分化,高原隆升和第四纪周期性气候波动是形成青藏高原高山植物现代谱系地理格局的主要原因。横断山脉地区作为第四纪冰期高山植物的主要避难所,在进化生物学和保护生物学方面具有重要启示。最后在物种选择、采样策略、基因片段选择和研究方法等4个方面提出青藏高原地区谱系地理学的研究方向。  相似文献   

7.
植物亲缘地理学的研究现状与发展趋势   总被引:2,自引:0,他引:2  
新生代以来剧烈的地质和气候变化,特别是第四纪冰期和间冰期的反复交错对温带植物类群的地理分布格局、种群结构和物种分化造成了深刻影响。近20年来,随着分子标记技术的发展和分析方法的成熟,植物亲缘地理学利用基因谱系关系和在种群中的时空分布来追溯种群的进化历史,在探讨植物类群对地质气候变迁的响应以及种群分化的历史成因等方面开展了大量工作,取得了一些重要进展。在取得这些成绩的同时,作者也注意到了被研究者所忽略的一些问题。试图对这些问题进行初步的总结,着重于分析方法和几个常用软件的使用,并对今后的发展趋势进行了展望。  相似文献   

8.
本文通过对黑斑蛙 8个地方种群 2 5 7个标本的线粒体基因组Cytb基因片段的序列分析 ,探讨了其种群遗传多样性的现代分布格局及其生物地理演化过程。对所检测出的 79个单倍型的分析表明 :黑斑蛙在我国分布区内中部地区的种群遗传多样性高于南北边缘种群。种群间基因流同地理隔离距离呈显著负相关 ,种群遗传分化符合距离隔离或脚踏石模型。线粒体单倍型以广西和四川种群的个体的遗传分化为最深 ,反映出西部山区的屏障隔离效应。单倍型歧点分布分析表明 ,约 10 3- 2 2 6万年前 ,即在末次间冰期 ,黑斑蛙在其分布范围内经历过一次大规模的种群扩张事件。单倍型的分布格局和共享情况显示黑斑蛙种群在冰期后的重新扩张过程主要表现为由南往北的递进式扩散形式。第四纪冰期气候的反复波动导致了黑斑蛙适宜生境在纬度方向上的平移 ,进而导致黑斑蛙种群随生境变化而进行扩张或收缩 ,使黑斑蛙种群的遗传多样性能始终保持在分布区中间高而南北两端低 ,并形成了现代的分布格局  相似文献   

9.
中国-日本植物区系极高的物种多样性是由多样的地形和气候条件、复杂的地质气候历史和海平面变化共同作用形成的。在揭示物种多样性形成和分化的驱动力时,谱系地理学是一个有效的手段。以往的谱系地理研究表明谱系地理间断,即不同基因谱系间的间断普遍存在。由西向东,7个普遍存在的谱系地理间断位置位于湄公河-怒江分水岭、田中-楷永线、四川盆地、105°E附近、第二三阶梯分界线、华北地区以及东海和朝鲜海峡。这些谱系地理间断的形成可归因于历史因素和生态因素,往往由地理隔离和环境隔离共同起作用。历史因素是地质事件和气候变化,主要包括青藏高原隆起,亚洲季风和内陆干旱的形成与增强,干旱带的重新增强以及第四纪的气候波动和海平面变化。生态因素是适应性分化,即不同环境中不同选择压力下形成的分化,适应性分化可阻碍不同种群间的基因流,形成谱系地理间断。不过,同一谱系地理间断并不是在所有植物中共享,因为不同植物有不同的生物学特性,主要是扩散能力不同。最后,该文从分化时间的准确估计、地理隔离和环境隔离的相对贡献率以及比较谱系地理学的应用3个方面对未来谱系地理间断研究的发展趋势进行了展望。  相似文献   

10.
探讨古气候波动(如更新世末期冰期)对典型生物的时空分布和有效种群大小变动的影响是生物地理学和进化遗传学的重要研究课题.本文利用线粒体cox2-3序列和RAPD两种分子标记,对分布于加拿大-西北大西洋地区8个地点(共138个个体)的掌形藻(Palmaria palmata)进行谱系地理学研究,试图阐明当更新世冰期来临时掌形藻如何衍生出适应性的进化机制,并形成当前的地理分布格局.结果表明,线粒体cox2-3间区序列共检测出11个单倍型,其中1个单倍型(C3)在所有种群中都有分布,并位于星状基因谱系的中心位置,可认为是祖先单倍型.St.Lawrence湾内北部的两个种群多样性最高,与其他地理种群分化最明显,这与基于RAPD数据的STRUCTURE聚类分析结果相一致.根据掌形藻遗传多样性及其单倍型谱系结构特征,推测掌形藻在加拿大-西北大西洋沿岸存在多个冰期避难所.分子多态性分析(AMOVA)显示掌形藻的遗传变异主要来自种群内,而St.Lawrence湾和Fundy湾群组间的遗传变异较小.cox2-3序列的Bayesian skyline plots分析结果反映出掌形藻种群在加拿大-西北大西洋沿岸经历了轻微的种群扩张,时间大概在0.18-0.13百万年前.St.Lawrence湾和Fundy湾群组间的K2P遗传距离为0.2%,相应的分化时间大约在0.36百万年前.由此推测,更新世末期的冰期及间冰期是影响掌形藻种群结构及变动的重要古气候环境因子.  相似文献   

11.
Recent empirical work on cloud forest‐adapted species supports the role of both old divergences across major geographical areas and more recent divergences attributed to Pleistocene climate changes. The shrub Moussonia deppeana is distributed in northern Mesoamerica, with geographically disjunct populations. Based on sampling throughout the species range and employing plastid and nuclear markers, we (i) test whether the fragmented distribution is correlated with main evolutionary lineages, (ii) reconstruct its phylogeographical history to infer the history of cloud forest in northern Mesoamerica and (iii) evaluate a set of refugia/vicariance scenarios for the region and demographic patterns of the populations whose ranges expanded and tracked cloud forest conditions during the Last Glacial Maximum. We found a deep evolutionary split in M. deppeana about 6–3 Ma, which could be consistent with a Pliocene divergence. Comparison of variation in plastid and nuclear markers revealed several lineages mostly congruent with their isolated geographical distribution and restricted gene flow among groups. Results of species distribution modelling and coalescent simulations fit a model of multiple refugia diverging during interglacial cycles. The demographic history of M. deppeana is not consistent with an expanding–contracting cloud forest archipelago model during the Last Glacial Maximum. Instead, our data suggest that populations persisted across the geographical range throughout the glacial cycles, and experienced isolation and divergence during interglacial periods.  相似文献   

12.
In response to climate changes that have occurred during Pleistocene glacial cycles, taxa associated to steppe vegetation might have followed a pattern of historical evolution in which isolation and fragmentation of populations occurred during the short interglacials and expansion events occurred during the long glacial periods, in contrast to the pattern described for temperate species. Here, we use molecular genetic data to evaluate this idea in a steppe bird with Palaearctic distribution, the little bustard (Tetrax tetrax). Overall, extremely low genetic diversity and differentiation was observed among eight little bustard populations distributed in Spain and France. Mismatch distribution analyses showed that most little bustard populations expanded during cooling periods previous to, and just after, the last interglacial period (127,000-111,000 years before present), when steppe habitats were widespread across Europe. Coalescent-based methods suggested that glacial expansions have resulted in substantial admixture in Western Europe due to the existence of different interglacial refugia. Our results are consistent with a model of evolution and genetic consequences of Pleistocene cycles with low between-population genetic differentiation as a result of short-term isolation periods during interglacials and long-term exchange during glacial periods.  相似文献   

13.
In the last few years, improved analytical tools and the integration of genetic data with multiple sources of information have shown that temperate species exhibited more complex responses to ice ages than previously thought. In this study, we investigated how Pleistocene climatic changes affected the current distribution and genetic diversity of European populations of the tick Ixodes ricinus, an ectoparasite with high ecological plasticity. We first used mitochondrial and nuclear genetic markers to investigate the phylogeographic structure of the species and its Pleistocene history using coalescent‐based methods; then we used species distribution modelling to infer the climatic niche of the species at last glacial maximum; finally, we reviewed the literature on the I. ricinus hosts to identify the locations of their glacial refugia. Our results support the scenario that during the last glacial phase, I. ricinus never experienced a prolonged allopatric divergence in separate glacial refugia, but persisted with interconnected populations across Southern and Central Europe. The generalist behaviour in host choice of I. ricinus would have played a major role in maintaining connections between its populations. Although most of the hosts persisted in separate refugia, from the point of view of I. ricinus, they represented a continuity of ‘bridges’ among populations. Our study highlights the importance of species‐specific ecology in affecting responses to Pleistocene glacial–interglacial cycles. Together with other cases in Europe and elsewhere, it contributes to setting new hypotheses on how species with wide ecological plasticity coped with Pleistocene climatic changes.  相似文献   

14.
Aim East Africa is one of the most biologically diverse regions, especially in terms of endemism and species richness. Hypotheses put forward to explain this high diversity invoke a role for forest refugia through: (1) accumulation of new species due to radiation within refugial habitats, or (2) retention of older palaeoendemic species in stable refugia. We tested these alternative hypotheses using data for a diverse genus of East African forest chameleons, Kinyongia. Location East Africa. Methods We constructed a dated phylogeny for Kinyongia using one nuclear and two mitochondrial markers. We identified areas of high phylogenetic diversity (PD) and evolutionary diversity (ED), and mapped ancestral areas to ascertain whether lineage diversification could best be explained by vicariance or dispersal. Results Vicariance best explains the present biogeographic patterns, with divergence between three major Kinyongia clades (Albertine Rift, southern Eastern Arc, northern Eastern Arc) in the early Miocene/Oligocene (> 20 Ma). Lineage diversification within these clades pre‐dates the Pliocene (> 6 Ma). These dates are much older than the Plio‐Pleistocene climatic shifts associated with cladogenesis in other East African taxa (e.g. birds), and instead point to a scenario whereby palaeoendemics are retained in refugia, rather than more recent radiations within refugia. Estimates of PD show that diversity was highest in the Uluguru, Nguru and East Usambara Mountains and several lineages (from Mount Kenya, South Pare and the Uluguru Mountains) stand out as being evolutionarily distinct as a result of isolation in forest refugia. PD was lower than expected by chance, suggesting that the phylogenetic signal is influenced by an unusually low number of extant lineages with long branch lengths, which is probably due to the retention of palaeoendemic lineages. Main conclusions The biogeographic patterns associated with Kinyongia are the result of long evolutionary histories in isolation. The phylogeny is dominated by ancient lineages whose origins date back to the early Miocene/Oligocene as a result of continental wide forest fragmentation and contraction due to long term climatic changes in Africa. The maintenance of palaeoendemic lineages in refugia has contributed substantially to the remarkably high biodiversity of East Africa.  相似文献   

15.
In East Asia, temperate forests are predicted to have retracted southward to c. 30° N during the last glacial maximum (LGM) based on fossil pollen data, whereas phylogeographic studies have often suggested glacial in situ survival of cool‐temperate deciduous trees in their modern northern ranges. Here we report a study of the genetic diversity and structure of 29 natural Mongolian oak (Quercus mongolica) populations using 19 nuclear simple sequence repeat (nSSR) loci and four chloroplast DNA fragments. Bayesian clustering analysis with nSSRs revealed five groups, which were inferred by approximate Bayesian computation (ABC) to have diverged in multiple refugia through multiple glacial–interglacial cycles. Analysis of chloroplast DNA variation revealed four lineages that were largely but incompletely geographically disjunct. Ecological niche modelling (ENMs) indicated a southward range shift of the oak's distribution at the LGM, although high suitability scores were also evident in the Changbai Mts. (Northeast China), the Korean Peninsula, areas surrounding the Bohai Sea, and along the coast of the Russian Far East. In addition, endemic chloroplast DNA haplotypes and nuclear lineages occurred in high‐latitude northern areas where the ENM predicted no suitable habitat. The combined evidence from nuclear and chloroplast DNA, and the results of the ENM clearly demonstrate that multiple northern refugia, including cryptic ones, were maintained across the current distributional range of the Mongolian oak during the LGM or earlier glacial periods. Though spatially limited, postglacial expansions from these refugia have led to a pattern of decreased genetic diversity with increasing latitude.  相似文献   

16.
Avian diversification in oceanic archipelagos is largely attributed to isolation across marine barriers. During glacial maxima, lowered sea levels resulted in repeated land connections between islands joined by shallow seas. Consequently, such islands are not expected to show endemism. However, if climate fluctuations simultaneously caused shifts in suitable environmental conditions, limiting populations to refugia, then occurrence on and dispersal across periodic land bridges are not tenable. To assess the degree to which paleoclimate barriers, rather than marine barriers, drove avian diversification in the Philippine Archipelago, we produced ecological niche models for current‐day, glacial maxima, and interglacial climate scenarios to infer potential Pleistocene distributions and paleoclimate barriers. We then tested marine and paleoclimate barriers for correspondence to geographic patterns of population divergence, inferred from DNA sequences from eight codistributed bird species. In all species, deep‐water channels corresponded to zones of genetic differentiation, but six species exhibited deeper divergence associated with a periodic land bridge in the southern Philippines. Ecological niche models for these species identified a common paleoclimate barrier that coincided with deep genetic structure among populations. Although dry land connections joined southern Philippine islands during low sea level stands, unfavorable environmental conditions limited populations within landmasses, resulting in long‐term isolation and genetic differentiation. These results highlight the complex nature of diversification in archipelagos: marine barriers, changes in connectivity due to sea level change, and climate‐induced refugia acted in concert to produce great species diversity and endemism in the Philippines.  相似文献   

17.
Hewitt GM 《Genetica》2011,139(5):617-638
The older history of hybrid zones is explored through consideration of recent advances in climatology, paleontology and phylogeography in the Late Cenozoic, particularly the Quaternary Period with its major climatic cycles. The fossil record shows that these ice ages and their nested millennial oscillations caused substantial changes in species distributions and with genetic evidence allows deduction of refugia and colonization routes in arctic, temperate, desert and tropical regions. The age of divergence between hybridizing lineages varies from the Late Pleistocene to the Late Miocene, implying much range change and varying selection on sister lineages. Hybridizing lineages in the Tropical and Temperate regions range in age from young to old, but those studied in the Arctic are no more than a few ice ages old and their refugial roots are not clear. Mid to low latitude regions often show parapatric patchworks of lineages and multiple refugia stable through many climatic oscillations. Particular hybrid zones may have formed more than once; while some expansions were not the same, producing reticulation and introgression in previous glacial cycles. Hybrid-zone roots are complex and deep, and considerations of their complexity can reveal evolutionary pathways of species. They are indeed windows on evolution.  相似文献   

18.
During the Late Pleistocene, glaciers sundered many species into multiple glacial refugia where populations diverged in allopatry. Although deeply divergent mitochondrial DNA (mtDNA) lineages often reflect the number of refugia occupied, it is unlikely that populations that split during the recent Wisconsin glaciations will have reached reciprocal monophyly. We examined mtDNA control region sequences from eastern and western populations of wood ducks (Aix sponsa) to determine whether their current, disjunct distribution is consistent with the occupancy of two glacial refugia. We used the 'isolation with migration' coalescent method (im) to simultaneously estimate effective population sizes, maternal gene flow, and time since divergence. We found 24 unique haplotypes, none of which were shared between the eastern and western populations, but we did not find diagnostic monophyletic lineages suggestive of long-term isolation in multiple glacial refugia. However, a high Phi ST (0.31) indicates that eastern and western populations are well differentiated in mtDNA, and results from im suggest that these populations have been diverging, without extensive gene flow, for 10,000 to 124,000 years. Results from im further suggest that these populations most likely split about 34,000 years ago, and this time of divergence is consistent with the occupancy of multiple glacial refugia during the Late Wisconsin glaciation. Eastern wood ducks are characterized by high genetic diversity, a large effective population size, and a recent population expansion, while western wood ducks have much less genetic diversity, a smaller population size, and have not undergone a recent population expansion.  相似文献   

19.
The historic processes which have led to the present-day patterns of genetic structure in the marine coastal fauna of the Northeast Atlantic are still poorly understood. While tectonic uplifts and changes in sea level may have caused large-scale vicariance, warmer conditions during glacial maxima may have allowed pockets of diversity to persist to a much wider extent than in the Northwestern Atlantic. The large-scale geographic distribution of deeply divergent lineages of the coastal polychaete tubeworms Pectinaria koreni (two clades) and Owenia fusiformis (three clades) were compared using a fragment of the mitochondrial cytochrome oxidase I gene (mtCOI). All lineages were present along the biogeographic transition zone on the north coast of Brittany (France) and we found evidence pointing towards congruence in the timing of cladogenic events between Pectinaria sp. (P. auricoma/P. belgica and P. koreni) and Owenia sp., suggesting a shared history of vicariant events. More conserved 16SrRNA sequences obtained from four species of Pectinariidae together with mtCOI sequences of P. koreni seem consistent with an initial establishment of pectinariids in the north, and a southward colonization of the Northeast Atlantic. Phylogeographic patterns in O. fusiformis were also consistent with a north/south pattern of lineage splitting and congruent levels of divergence were detected between lineages of both species. We observed signatures of both persistence in small northern glacial refugia, and of northwards range expansion from regions situated closer to the Mediterranean. However, whether the recolonization of the Northeast Atlantic by both species actually reflects separate interglacial periods is unclear with regards to the lack of molecular clock calibration in coastal polychaete species.  相似文献   

20.
Although the high‐latitude range margins in Europe and North America are intensively studied, attention is gradually turned towards the taxa/populations inhabiting glacial refugia. Here, we evaluate the genealogical history of the cold‐adapted Anatolio‐Balkan genus Anterastes especially to test the possible effects of intrarefugial vertical range shifts during climatic oscillations of the Quaternary. Using concatenated data from sequences of COI+16S and ITS1–5.8S–ITS2, intrageneric relationships and the time of speciation events were estimated. Thirteen different demographic analyses were performed using a data set produced from sequences of 16S. Different phylogenetic analyses recovered similar lineages with high resolution. The molecular chronogram estimated speciation events in a period ranging from 5.60 to 1.22 Myr. Demographic analyses applied to 13 populations and five lineages suggested constant population size. Genetic diversity is significantly reduced in a few populations, while not in others. Fixation indices suggested extremely diverged populations. In the light of these data, the following main conclusions were raised: (i) although glacial refugia are the biodiversity hotspots, species level radiation of the cold‐adapted lineages is mainly prior to the Mid‐Pleistocene transition; (ii) heterogeneous topography provides refugial habitats and allows populations to survive through vertical range shifts during climatic fluctuations; (iii) prolonged isolation of refugial populations do not always result in reduced intrapopulation diversity, but in high level of genetic differentiation; (iv) the cold‐adapted lineages with low dispersal ability might have not colonised the area out of Anatolian refugium during interglacial periods; and (v) populations of invertebrates may have restricted ranges, but this does not mean that they have small effective population size.  相似文献   

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