云南泸沽湖及周边山地表层孢粉与植被关系研究

本文对云南泸沽湖周边山地不同植被类型下采集的32个表土样品和36个泸沽湖湖泊表层样品进行了孢粉分析,探讨了不同植被类型内的表土孢粉散布特征,对比分析了山地表土与湖泊表层孢粉分布特征的差异。结果表明,不同山地植被类型的孢粉组合具有不同的代表性成分与变化特征,能够较好地反映相应的植被类型。湖泊表层孢粉研究表明,湖泊内不同位置的孢粉组合差异较小,说明湖泊表层孢粉反映的是区域植被的平均分布状况。对比分析泸沽湖周边山地表土与湖泊表层样品的孢粉组合,两者存在一定的差异,表现为:湖泊表层的孢粉组合中乔木花粉(主要是松属)平均含量比表土高,但波动范围要小;草本花粉平均含量要低,且波动范围也小。这可能是由于乔木植物植株较高,而且有些乔木植物花粉具有气囊,更易借助风力将花粉传播到比较远的湖泊中的原因造成的。冷杉和铁杉花粉在所有样品中含量都相对较低,分别不高于6.5%和3.6%;桦属、桤木属、常绿栎类花粉的最高值出现在有这些母体植物生长的表土样品中,在其他样品中则明显较低。在表土孢粉样品中经常可以见到冷杉的气孔器,但在湖泊表层样品中却没有见到,说明气孔器不易到达湖泊中。该研究是对中国西南表层孢粉研究的有益补充,同时为泸沽湖新生代特别是第四纪化石孢粉解释提供了可靠的参考和依据。     

内蒙古东胜中侏罗世延安组孢粉组合

研究了内蒙古东胜罕台川、碾盘梁沟和柳沟3个剖面中侏罗世孢子花粉化石34属63种, 包括2个新种. 基于10个样品中发现的3 863粒孢子花粉化石的鉴定和统计, 建立东胜地区延安组孢粉组合.该组合中蕨类植物孢子有19属37种, 含量占46%～49%, 最低为39%.裸子植物花粉略占优势, 有15属26种,含量为51%～54%, 最高达61%.与国内外相关资料对比结果表明该孢粉组合的地质时代应属中侏罗世巴柔期.孢粉植物群反映研究区在中侏罗世早期为暖温带或亚热带的暖湿气候.     

巢湖地区现代花粉—植被—人类活动关系研究

巢湖地区的孢粉研究多集中于化石孢粉, 相对缺少现代孢粉研究的支持。选取巢湖地区苔藓表土样品及湖泊表层底泥样品共49个进行孢粉分析, 探讨现代花粉与植被分布及人类活动的关系。结果表明: 花粉组合与当地植被有着很好的对应关系, 可以反映出当地的植被状况, 松属、栗属、落叶栎类、榆科、朴属、柳属、枫杨属、蔷薇科、十字花科、蒿属、紫菀属、禾本科(≤37 μm)、藜科和眼子菜属为花粉主要类型。现代花粉和钻孔花粉的匹配度较高, 可以为反演古植被古气候提供科学依据。花粉图谱和聚类分析将所有的采样点划分为4个土地利用类型。主成分分析相对划分出3个不同程度的人类活动影响区域: (1) 农田区—人类活动影响最强烈的区域; (2) 公园绿地区—人类活动影响较强的区域; (3) 次生林和湖心区—人类活动影响较弱的区域。巢湖地区十字花科花粉含量的变化在一定程度上可以区分人类活动的强弱, 有较强的指示作用。此外, 由于大规模开发、人工栽培以及次生林生长等因素均可能对花粉含量产生较大影响, 结合钻孔孢粉分析推测近1000年来巢湖地区松属、十字花科和谷物类禾本科花粉大量增加的主要影响因素极有可能是人为因素而非自然因素。     

四川螺髻山表土和化石孢粉揭示的环境生态意义

通过四川螺髻山（1984、2017年）表土和化石孢粉与植被的关系分析发现：孢粉组合中木本植物含量（91.0%）占绝对优势,松属、冷杉属、青冈属、常绿栎类、落叶栎类、桤木属、杜鹃花科、禾本科和蒿属为主要花粉类型;人工次生林花粉组合能很好地反映母体植被的群落特征,并可指示优势种的存在和人类活动痕迹;针阔混交林花粉组合能较好地反映群落整体特征,花粉类型能与母体植被中优势种较好地对应;常绿阔叶林、针叶林和灌丛草甸的花粉组合难以反映母体植被的群落特征。DCA表明,花粉谱的百分含量,能较好地区分人工扰动植被和天然植被,但人工次生林、常绿阔叶林和针阔混交林之间以及针叶林和灌丛草甸之间未能区分。30年前后表土孢粉组合变化明显,1984年样品以松属、青冈属和桤木属等花粉为主,而2017年采样分析中松属、桤木属花粉占绝对优势。随着人类活动的加强,部分地区松树和桤木大面积飞播或种植,表土孢粉组合对当地植被指示意义与扰动强度呈负相关关系。现生植被与表土孢粉组合的差异能为恢复古植被和古环境提供参考,但原生植被已经被破坏地区的孢粉图谱,就很难作为重建历史时期植被的根据。本研究可以为亚热带山地利用孢粉学恢复第四纪时期植被与气候,探讨人类活动与环境的关系提供理论依据和实践参考。     

内蒙古东胜中侏罗世延安组孢粉组合

研究了内蒙古东胜罕台川、碾盘梁沟和柳沟 3个剖面中侏罗世孢子花粉化石 34属 6 3种 ,包括 2个新种。基于 10个样品中发现的 386 3粒孢子花粉化石的鉴定和统计 ,建立东胜地区延安组孢粉组合。该组合中蕨类植物孢子有 19属 37种 ,含量占 46 %～ 49% ,最低为 39%。裸子植物花粉略占优势 ,有 15属 2 6种 ,含量为 5 1%～ 5 4% ,最高达 6 1%。与国内外相关资料对比结果表明该孢粉组合的地质时代应属中侏罗世巴柔期。孢粉植物群反映研究区在中侏罗世早期为暖温带或亚热带的暖湿气候     

重庆喀斯特地区现代花粉组合与植被的关系

重庆喀斯特地区4种不同地貌单元的81份表土和苔藓样品的孢粉分析结果表明:(1)研究区植物孢粉组合共由109科属组成。除金佛山外,其他植被退化严重地区样点均以草本和蕨类植物占据优势(剔除石漠化治理大量引种的马尾松、柳杉和侧柏等乔木花粉),其次是乔木植物花粉(主要为马尾松),灌木植物花粉含量很低,显示该区植被退化严重;(2)孢粉组合的PCA分析能够很好地将研究区的现代孢粉组合区分开来,较好地反映了重庆喀斯特地区不同地貌单元的植被特征,特别是石漠化区植被退化严重的孢粉组合特征。生态保护较好、自然植被发育的金佛山地区具有106科属的乔木、灌木与草本孢粉类型,以及高含量的乔木花粉,而喀斯特石漠化地区的鸡公山(46科属)、青木关镇(56科属)和南平镇(50科属)则表现为乔灌木孢粉类型较少;(3)银杉作为金佛山特有的孑遗植物,其花粉含量明显低于松属花粉,说明其花粉不利于远距离传播;(4)随着土地利用强度的增加,现代孢粉组合中乔灌木花粉含量和种类越少,草本和蕨类植物孢粉含量越多,且以耕地杂草为主。因此,土地利用方式的变化是喀斯特石漠化区次生植被及其现代孢粉组合变化的主要影响因素。研究可为重庆喀斯特地区土地利用策略的制定,重庆及其周边地区第四纪古植被、古气候和古环境重建研究,以及中国孢粉数据库建设提供基本数据和科学依据。     

山东平邑盆地古新世孢粉组合及其古气候意义

本文对山东平邑盆地卞桥镇国泰庄西ZK101井卞桥组二段的21块井壁岩芯样品进行分析,在其中5块样品中发现了大量保存较好的孢粉和一些淡水藻类化石,总计60属2亚属63种及部分未定种。据此建立了一个孢粉组合,即Pterisisporites-Ephedripites-Ulmaceae组合。该组合以凤尾蕨科和麻黄科花粉占优势,榆科有一定含量为其主要特征,并通过对一些重要分子的地质时代分布及与邻区相关孢粉组合进行对比,确定了其时代为古新世,同时讨论了该孢粉植物群所反映的古气候特点。     

新疆吐哈盆地北缘黄山街组孢粉组合

新疆鄯照壁山沟口和柯柯亚剖面黄山街组的孢粉化石,经研究,共有52属77种。命名为Dictyophylli-dites-Aratrisporites-Parataeniaesporites组合（简称DAP组合）。根据组合主要分子的已知时代分布、含量高低变化,以及与有关已知时代孢粉组合进行对比,鉴定其地质时代为晚三叠世早中期。根据孢粉组合恢复古植被,反映当时的气候为温暖潮湿的温带类型。     

西藏普兰涕松上新世孢粉植物群

前言中国科学院的西藏高原综合科学考察队,于1976年夏季,首次在西藏阿里地区进行多学科考察.南京大学地理系王富葆,在喜马拉雅山脉西段北坡孔雀河流域的涕松褐煤露头剖面,采集了15块孢粉样品,赠给笔者研究.经过分析,其中7块样品获得孢粉化石,种类繁多,含量丰富,地质时代属于上新世早、中期.这一孢粉植物群对探讨西藏高原的古植被、古气候和古地理的演变,以及喜马拉雅山脉的上升问题,提供了重要资料.孢粉样品的处理由黄凤宝分析,照片由毛继良拍摄,插图由徐宝瑞绘制.孢粉属种承我院植物研究所张金谈鉴定,文稿承王富葆提出宝贵意见,均在此表示感谢.     

东北长白山垂直林带下现代表土花粉与植被关系

在长白山北坡5个垂直植被带的林下采集29个表土(苔藓)样品进行孢粉分析,同时将其结果作对应分析.结果表明,除个别样品,在长白山垂直植被带的孢粉组合中乔木花粉占优势,其中以松属和桦木属最多,在各植被带均有分布.松属花粉最高含量出现在以红松为主的针阔混交林带的孢粉组合中;桦木属花粉则大量见于亚高山岳桦林带和以栎桦为主的阔叶落叶林带,但前者伴有耐寒、早的小灌丛杜鹃花属花粉,而在后者中则见有大量蕨类孢子.阔叶落叶林带的孢粉组合是以类型多、百分含量高的落叶乔木花粉和大量蕨类孢子为特征.亚高山针叶林带的孢粉组合中出现数量众多的云杉属花粉.在高山苔原带孢粉组合中虽然乔木花粉略占优势,但极少或不见蕨类孢子,与其他植被带比较,草本植物和小灌丛花粉明鲜较多,其中杜鹃属花粉含量在草本中占优势,其中出现苔原带的指示花粉--仙女木属.     

Multivariate analysis of neognath skeletal measurements: implications for body mass estimation in Mesozoic birds

The abundant fossils of avian stem taxa unearthed during the last years make it necessary to review and improve the models for estimating body mass used in palaeoecological studies. In this article, single and multiple regression functions based on osteological measurements were obtained from a large data set of extant flying birds for estimating the body mass of 42 Mesozoic specimens from stem taxa Archaeopterygidae, Jeholornithidae, Sapeornithidae, Confuciusornithidae, and Enantiornithes, and basal members of Ornithuromorpha. Traditionally, body mass has been estimated in fossil vertebrates using univariate scaling functions. In contrast, multiple regression functions have been used less frequently. Both predictive methods can be affected by different sources of error from statistics, phylogenetic relationships, ecological adaptations, and bone preservation; however, although some studies have addressed these biases, few have tested them within the context of a single data set. In our data set, we find that the models with greater predictive strength and applicability for new specimens, especially for stem taxa, are those derived from multiple regression analyses. For this reason, we suggest that multiple regression analyses may provide improved predictive strength for stem group specimens. Moreover, the methodology used for selecting variables allowed us to obtain specific sets of predictors for each fossil stem group that presumably minimized the variation resulting from historical contingency (i.e. differences in skeletal morphology arising from phylogeny), locomotor adaptations, and diagenetic compaction. The loss of generalizability in the multiple regression models resulting from collinearity effects was negligible on the body mass estimates derived from our data set. Therefore, the body mass values obtained for Mesozoic specimens are accurate and can be used in future studies in a number of palaeobiological and evolutionary aspects of extinct birds, particularly the first stages of avian flight. © 2015 The Linnean Society of London     

POTENTIAL PITFALLS OF RECONSTRUCTING DEEP TIME EVOLUTIONARY HISTORY WITH ONLY EXTANT DATA,A CASE STUDY USING THE CANIDAE (MAMMALIA,CARNIVORA)

Reconstructing evolutionary patterns and their underlying processes is a central goal in biology. Yet many analyses of deep evolutionary histories assume that data from the fossil record is too incomplete to include, and rely solely on databases of extant taxa. Excluding fossil taxa assumes that character state distributions across living taxa are faithful representations of a clade's entire evolutionary history. Many factors can make this assumption problematic. Fossil taxa do not simply lead‐up to extant taxa; they represent now‐extinct lineages that can substantially impact interpretations of character evolution for extant groups. Here, we analyze body mass data for extant and fossil canids (dogs, foxes, and relatives) for changes in mean and variance through time. AIC‐based model selection recovered distinct models for each of eight canid subgroups. We compared model fit of parameter estimates for (1) extant data alone and (2) extant and fossil data, demonstrating that the latter performs significantly better. Moreover, extant‐only analyses result in unrealistically low estimates of ancestral mass. Although fossil data are not always available, reconstructions of deep‐time organismal evolution in the absence of deep‐time data can be highly inaccurate, and we argue that every effort should be made to include fossil data in macroevolutionary studies.     

Fossils impact as hard as living taxa in parsimony analyses of morphology

Systematists disagree whether data from fossils should be included in parsimony analyses. In a handful of well-documented cases, the addition of fossil data radically overturns a hypothesis of relationships based on extant taxa alone. Fossils can break up long branches and preserve character combinations closer in time to deep splitting events. However, fossils usually require more interpretation than extant taxa, introducing greater potential for spurious codings. Moreover, because fossils often have more "missing" codings, they are frequently accused of increasing numbers of MPTs, frustrating resolution and reducing support. Despite the controversy, remarkably little is known about the effects of fossils more generally. Here we provide the first systematic study, investigating empirically the behavior of fossil and extant taxa in 45 published morphological data sets. First-order jackknifing is used to determine the effects that each terminal has on inferred relationships, on the number of MPTs, and on CI' and RI as measures of homoplasy. Bootstrap leaf stabilities provide a proxy for the contribution of individual taxa to the branch support in the rest of the tree. There is no significant difference in the impact of fossil versus extant taxa on relationships, numbers of MPTs, and CI' or RI. However, adding individual fossil taxa is more likely to reduce the total branch support of the tree than adding extant taxa. This must be weighed against the superior taxon sampling afforded by including judiciously coded fossils, providing data from otherwise unsampled regions of the tree. We therefore recommend that investigators should include fossils, in the absence of compelling and case specific reasons for their exclusion.     

Combining phylogenomics and fossils in higher-level squamate reptile phylogeny: molecular data change the placement of fossil taxa

Molecular data offer great potential to resolve the phylogeny of living taxa but can molecular data improve our understanding of relationships of fossil taxa? Simulations suggest that this is possible, but few empirical examples have demonstrated the ability of molecular data to change the placement of fossil taxa. We offer such an example here. We analyze the placement of snakes among squamate reptiles, combining published morphological data (363 characters) and new DNA sequence data (15,794 characters, 22 nuclear loci) for 45 living and 19 fossil taxa. We find several intriguing results. First, some fossil taxa undergo major changes in their phylogenetic position when molecular data are added. Second, most fossil taxa are placed with strong support in the expected clades by the combined data Bayesian analyses, despite each having >98% missing cells and despite recent suggestions that extensive missing data are problematic for Bayesian phylogenetics. Third, morphological data can change the placement of living taxa in combined analyses, even when there is an overwhelming majority of molecular characters. Finally, we find strong but apparently misleading signal in the morphological data, seemingly associated with a burrowing lifestyle in snakes, amphisbaenians, and dibamids. Overall, our results suggest promise for an integrated and comprehensive Tree of Life by combining molecular and morphological data for living and fossil taxa.     

Numerical experiments with model monophyletic and paraphyletic taxa

The problem of how accurately paraphyletic taxa versus monophyletic (i.e., holophyletic) groups (clades) capture underlying species patterns of diversity and extinction is explored with Monte Carlo simulations. Phylogenies are modeled as stochastic trees. Paraphyletic taxa are defined in an arbitrary manner by randomly choosing progenitors and clustering all descendants not belonging to other taxa. These taxa are then examined to determine which are clades, and the remaining paraphyletic groups are dissected to discover monophyletic subgroups. Comparisons of diversity patterns and extinction rates between modeled taxa and lineages indicate that paraphyletic groups can adequately capture lineage information under a variety of conditions of diversification and mass extinction. This suggests that these groups constitute more than mere "taxonomic noise" in this context. But, strictly monophyletic groups perform somewhat better, especially with regard to mass extinctions. However, when low levels of paleontologic sampling are simulated, the veracity of clades deteriorates, especially with respect to diversity, and modeled paraphyletic taxa often capture more information about underlying lineages. Thus, for studies of diversity and taxic evolution in the fossil record, traditional paleontologic genera and families need not be rejected in favor of cladistically-defined taxa.     

Timing in the evolution of derived floral characters: upper cretaceous (turonian) taxa with tricolpate and tricolpate-derived pollen

Various hypotheses that seek to explain the rich species diversity of angiosperms relative to other seed plants are briefly mentioned or reviewed. Of these, the subset that relates angiosperm diversity in some way to the relationship between angiosperms and insects, particularly anthophilous insects, is here the object of attention. Specifically, I address and reject the possibility that the relationship between angiosperm diversification and insects, particularly those demonstrating a preference for flowers with derived floral characteristics associated with insect pollination, may be ruled out because of asynchronous patterns of diversification in the fossil record. New data on floral structure from the Turonian of the Atlantic Coastal Plain reveal a surprising diversity of floral characters in taxa bearing tricolpate and tricolporate-derived pollen. The characters and taxa that appear in these Turonian sediments suggest that rather specific modes of insect pollination, perhaps involving highly derived insect pollinators, already existed at 90 Ma. Given the observed rate of diversification of angiosperms during that time and the pattern of evolution in insects, including what can be inferred about the history of the Apidae, these new floral data suggest that hypotheses relating angiosperm diversity to highly specific pollinators are still valid in the context of fossil evidence. Even so, consistency with fossil evidence is not necessarily proof of these relationships. In any case, there may well be multiple causes of relatively high angiosperm species diversity and understanding the relative importance of each of these requires neontological as well as paleontological investigations. One promising approach is to work within the context of phylogenetic patterns with more fossil data.     

Perikymata spacing and distribution on hominid anterior teeth

We documented the spacing and distribution of perikymata on the buccal enamel surface of fossil hominin anterior teeth with reference to a sample of modern human and modern great ape teeth. A sample of 27 anterior teeth attributed to Australopithecus (5 to A. afarensis, 22 to A. africanus) and of 33 attributed to Paranthropus (6 to P. boisei, and 27 to P. robustus) were replicated and sputter-coated with gold to enable reflected light microscopy of their surface topography. Anterior teeth were then divided into 10 equal divisions of buccal crown height. The total perikymata count in each division of crown height was recorded using a binocular microscope fitted with a vernier micrometer eyepiece. Then the mean number of perikymata per millimeter was calculated for each division. Similar comparative data for a modern sample of 115 unworn human anterior teeth and 30 African great ape anterior teeth were collected from ground sections. Perikymata counts in each taxon (together with either known or presumed periodicities of perikymata) were then used to estimate enamel formation times in each division of crown height, for all anterior tooth types combined. The distributions of these estimates of time taken to form each division of crown height follow the same trends as the actual perikymata counts and differ between taxa in the same basic way. The distinction between modern African great apes and fossil hominins is particularly clear. Finally, we calculated crown formation times for each anterior tooth type by summing cuspal and lateral enamel formation times. Estimates of average crown formation times in australopiths are shorter than those calculated for both modern human and African great ape anterior teeth. The data presented here provide a better basis for exploring differences in perikymata spacing and distribution among fossil hominins, and provide the first opportunity to describe four specimens attributed to Homo in this context. Preliminary data indicate that differences may exist among the species attributed to early Homo, especially between Homo ergaster and Homo rudolfensis on the one hand, and Homo habilis sensu strico on the other.