连香树科及其近缘植物matK序列分析和系统学意义

测定和分析了连香树科(Cercidiphyllaeeae)、交让木科(Daplmiphyllaceac)、金缕梅科(Hamamelidaceae)代表植物的叶绿体marK序列(5′端31bps除外),以木兰属作为外类群,应用邻接法构建分子系统树,结果表明：连香树科与水青树科的亲缘关系较远。连香树科、交让木科和金缕梅科形成了一个自展数据支持率(bootstrap)为100％的单系类群,其中金缕梅科枫香属(Liquidambar)、红花荷属(Rhodoleia)和金缕梅属(Hamamelis)虽构成了一个单系类群,但自展数据支持率仅为68％;连香树科与交让木科构成的单系分支自展数据支持率仅为53％。由于连香树科、交让木科、金缕梅科之间的进化距离相当短,表明这3个科之间亲缘关系密切,内部分支的自展数据支持率不高,表明它们之间准确的亲缘关系有待进一步研究。本研究结果与rbcL、aptB、18S rDNA序列分析结果相似,但自展数据支持率更高,表明marK序列分析可应用于较高等级分类群系统发育关系的研究。     

中国丝盖伞属裂盖组的三个新种

丝盖伞属裂盖组Inocybe sect. Rimosae sensu lato是一个分类难度较大的类群,组内的一些种类被认为是复合种。分子系统发育分析表明该组并非单系群,该组成员隶属于丝盖伞科下的2个属级分支,Inosperma分支和Pseudosperma分支。本文结合形态学特征和分子序列分析,对我国丝盖伞属裂盖组进行了分类学研究,发现3个新种：长白丝盖伞Inocybe changbaiensis、新茶褐丝盖伞I. neoumbrinella和云南丝盖伞I. yunnanensis。长白丝盖伞和新茶褐丝盖伞产自中国东北,前者生于针阔混交林下,后者生于柳树林下;云南丝盖伞产自云南省昆明市,生于阔叶树下。基于LSU序列的系统发育分析结果显示,长白丝盖伞隶属于Inosperma分支,新茶褐丝盖伞和云南丝盖伞隶属于Pseudosperma分支。本文对此进行了形态描述和特征图示,并讨论了新种与近缘种之间的异同。编制了中国丝盖伞属裂盖组已知种类的分种检索表。     

根据DNA的序列资料探讨翅子树族的系统位置

采用DNA分子测序技术对梧桐科5个族30个代表种的rbcL基因及核糖体DNA的内转录间隔区ITS序列(包括ITS1、ITS2和5．8srRNA基因)进行了序列分析。使用PAUP4．0b10软件对序列进行统计和分支分析。用启发式搜索方法寻找最简约树。从严格一致性树来看,梧桐科的全部代表类群主要被分为4支,一支仅为Sterculieae所构成;一支包括Helictereae的全部代表种;一支由Byttnerieae代表种所构成;最后一支由Dombeyeae和单属族翅子树族Pterospermeae所构成。rbcL和ITS系统树的不同仅表现在族内个别代表类群的位置和族的分支方式上。分析结果表明,与Helictereae相比,翅子树属,Pterospermum与Dombeyeae有更近的亲缘关系。然而,在外部形态、内部解剖和胚胎学方面,二者之间又存在诸多差异．故支持将Pterospermum另立为Ptcrospermeae的观点。     

从18S rDNA序列初探散胞盘菌亚科属间亲缘关系

散胞盘菌亚科Encoelioideae建于1932年,为盘菌纲Discomycetes锤舌菌目Leotiales锤舌菌科（广义）Leotiaceae的成员,它包括腐生、植物寄生、真菌上生的盘状子囊菌,现含18属,其中若干为单种属。传统分类从形态学角度将外囊盘表层细胞松散结合或者表面覆盖短的菌丝延伸物视为此亚科的主要特征,宏观上,其成员的共性表现为外囊盘被表面糠皮状、鳞屑状或霜状。迄今,学者们从未对散孢盘菌亚科这一性状是否反映属间亲缘关系进行过任何探讨,国际基因库中亦无此亚科的可利用序列。为了探明此性状在系统演化过程中的作用以及散胞盘菌亚科的属间亲缘关系,我们对此亚科中绿散胞盘菌Chlorencoelia、复柄盘菌属Cordierites、散胞盘菌属Encoelia、霍氏盘菌属Holwaya、拟爪毛盘菌属 Unguiculariopsis、以及丝绒盘菌属Velutarina代表种的18SrDNA片段进行了序列测定,受实验材料所限,每属只获得了一个种的18SrDNA序列。为了分析和比较,还对同一科内锤舌菌亚科Leotioideae中绿杯菌属Chlorociboria一个种的相关序列进行了测定。在构建系统树的过程中,核盘菌科的核盘菌Sclerotiniasclerotiorum被选为外群;从基因库中调入属于同一个目的地舌菌科和锤舌菌亚科几个属的代表即胶鼓菌属Bulgaria、锤舌菌属Leotia、小舌菌属Microglossum、新胶鼓菌属Neobulgaria和地勺菌属Spathularia的序列;利用ClustalW和TreeView软件,构建出Neighbour-joining系统进化树。初步的研究结果表明,散孢盘菌亚科不是单源的,该亚科的成员与其他亚科或者其他科的物种一起形成四个系统演化分支。散胞盘菌亚科的Holwaya与另一亚科的Bulgaria（Leotiaceae,Leotioideae）聚在一起,具有95%的序列相似性和97.4%支持率（bootstrapvalue）;此二属与Leotia（Leotiaceae,Leotioideae）和Microglossum（Geoglossaceae）组成姐妹群。散胞盘菌亚科Cordierites和Encoelia接近,支持率为93.6%;它们是Leotioideae中Chlorociboria和Neobulgaria两属的姐妹群。散胞盘菌亚科的Unguiculariopsis与Velutarina在一起,独立成为一个分支,支持率高达99.3%。Chlorencoelia与本研究所涉及的散胞盘菌亚科其他成员的关系都比较远。以上研究结果表明,散胞盘菌亚科很可能是多源的;但是,由于该亚科大多数属缺乏分子生物学证据,本研究结果只能作为推断。     

座囊菌目及相关类群属间关系的系统学初探

本研究对座囊菌纲部分类群的18S和28SnrDNA部分序列片段进行分析,探讨它们属间的系统学关系。邻接法和简约法分析结果显示,座囊菌纲供试类群为单起源,形成三个独立的分支并获得较强的支持率,分别代表座囊菌目、葡萄座腔菌目和格孢腔菌目。结果还显示,座囊菌纲中分类地位不确定的属Macrovalsaria与Botryosphaeria的关系相对接近,应该归于葡萄座腔菌目;历史上分类地位有疑问的Neopeckia和Dothidotthia两个属处于不同的目中,前者属于座囊菌目,后者为葡萄座腔菌目的成员;座囊菌目的Plowrightia属并非单系群,该属成员分别与Dothidea、Neopeckia和Sydowia三个属聚类在一起;现行的Botryosphaeria属也非单系群,其属的概念有待澄清。格孢腔菌目参试的7个属形成一个单系群,但属间的支持率非常低,表明它们应该在较高的分类等级上予以区分;序列分析的结果支持了基于形态学特征将Phragmogibbera纳入格孢腔菌目的分类观点。     

小孢盘菌属种间关系初探（英文）

3个编码蛋白的基因RPB1、RPB2和TEF1以及1个非编码序列28S rD NA的联合分析结果表明,小孢盘菌属位于系统树的上端,形成一个单系群,其中长春小孢盘菌和北京小孢盘菌为姐妹群,它们进一步与该属另3个种(包括该属的模式种)聚类在一起。序列分析结果支持将子囊孢子大小作为小孢盘菌属区分物种的依据,还表明火丝菌科可能不是一个单系群。在参试属中,小孢盘菌属与侧盘菌属的关系较为密切,它们具有极其相似的薄壁子囊,这表明在属的等级上子囊形态可能携带系统发育方面的信息。     

极小种群濒危植物广西火桐、丹霞梧桐的叶绿体基因组特征

广西火桐(Firmiana kwangsiensis)和丹霞梧桐(F. danxiaensis)是我国南方特有物种, 其分布范围狭窄, 种群数量少。为了解其叶绿体基因组结构及系统发生关系, 本文通过高通量测序方法获得广西火桐和丹霞梧桐的浅层基因组数据, 通过生物信息学方法对叶绿体全基因组进行组装, 并对其结构特征进行分析。结果表明: 广西火桐和丹霞梧桐的叶绿体基因组大小分别为160,836 bp和161,253 bp, 具有典型被子植物叶绿体基因组环状四分体结构, 包含长度分别为89,700 bp、90,142 bp的大单拷贝区(large single copy, LSC), 长度分别为19,970 bp、20,067 bp的小单拷贝区(small single copy, SSC)及长度分别为25,583 bp、25,522 bp的2个反向重复序列区(inverted repeat sequence, IR)。两个物种的叶绿体基因组共注释得到131个基因, 包括86个蛋白编码基因、37个tRNA基因和8个rRNA基因。广西火桐的叶绿体基因组中共检测出26个正向重复序列、2个反向重复序列、21个回文重复序列、21个串联重复序列和98个简单重复序列; 丹霞梧桐叶绿体基因组中共检测出23个正向重复序列、5个反向重复序列、21个回文重复序列、30个串联重复序列和107个简单重复序列。系统发生分析结果表明5种梧桐属(Firmiana)植物构成两个强烈支持的分支(支持率100%), 一个分支为广西火桐、美丽火桐(F. pulcherrima)和火桐(F. colorata), 其中广西火桐与美丽火桐构成姐妹群; 另一分支是互为姐妹群的丹霞梧桐和云南梧桐(F. major)。综上所述, 广西火桐和丹霞梧桐的叶绿体基因组结构、基因排列及重复序列具有较高的相似性, 系统进化树将5种梧桐属物种分为两个分支, 其中广西火桐和美丽火桐最近; 而丹霞梧桐与云南梧桐关系最近。本研究鉴定的SSR位点可为梧桐属物种系统发生、进化关系的研究提供遗传信息。     

基于rDNA ITS序列对绒泡菌目黏菌系统发育的探讨

绒泡菌目Physarida是黏菌纲Myxogastria最大的一个目,对其系统发育关系的研究一直是根据形态特征。为了从分子水平探讨绒泡菌目乃至黏菌纲的系统发育关系,以黏菌r DNA ITS通用引物对绒泡菌目5属8种黏菌的r DNA ITS进行扩增和测序,结合Gen Bank中已有的黏菌r DNA ITS序列,利用贝叶斯推断法(Bayesian inference,BI)和最大似然法(Maximum likelihood,ML)构建系统发育树。结果表明:绒泡菌目不同物种的r DNA ITS区在碱基组成和长度上差异明显,长度为777–1 445bp,G+C mol%在53.4%–61.9%之间。绒泡菌目与发网菌目Stemonitida聚类为两个明显的分支,在绒泡菌目分支上,绒泡菌科Physaraceae和钙皮菌科Didymiaceae各聚为一支,支持了形态学上以孢丝是否具有石灰质为依据区分这两个科的观点。由多份不同地理来源的鳞钙皮菌Didymium squamulosum材料组成的钙皮菌科又形成3个分支,证实了这个形态种是由地域来源广泛、繁殖亲和性各异和遗传变异较大的不同生物种组成的复合体。     

基于形态特征和ITS序列对7个鹅膏菌属菌株的分类鉴定

以采自浙江省丽水地区的7个鹅膏菌属菌株作为研究材料,在基于形态特征进行初步鉴定的基础上,对7种鹅膏菌的rDNAITS区段进行克隆测序和序列特征比较分析。进一步对ITS序列进行核酸序列数据库GenBank同源性检索比对,将从GenBank检索获得的9个最相似物种的ITS序列连同7种鹅膏菌的ITS序列一起作系统发育分析。结果表明:基于ITS序列对f6、f9和f493个菌株的分子鉴定支持了基于形态特征的鉴定结果,对f5的分子鉴定不支持形态鉴定的结果,f8为鹅膏菌属内某种,f66为鹅膏菌属内某种,并与Amanitafulva,A.atrofusca,A.orientifulva3种鹅膏菌的亲缘关系较近,f7与另外6种鹅膏菌的亲缘关系相差甚远。研究结果提示基于分子水平上的ITS序列分析不能单方面作为大型真菌分类鉴定的可靠依据,可以作为基于传统形态学分类鉴定的辅助参考依据。     

石鲈科鱼类的系统发育分析兼论髭鲷属的分类地位

通过线粒体16S rRNA基因部分序列分子标记,分析了石鲈科7属15种鱼的分子系统发育关系,并通过对部分种类16S rRNA基因片段的RNA二级结构的分析,对髭鲷属分类地位进行了探讨.结果表明:15种石鲈科鱼类分为3个类群,石鲈属Haemulon、Xenistius和Anisotremus属组成类群1,矶鲈属和胡椒鲷属组成类群2,髭鲷属组成类群3;在亲缘关系上类群1和类群2较近,它们与类群3相对较远;在遗传差异上,髭鲷属与其它6个属的遗传差异接近甚至超过其与外类群笛鲷科、鲷科和隆头鱼科种类的遗传差异.在NJ和MP系统发育树中,髭鲷属与外类群笛鲷科、鲷科和隆头鱼科种类聚集在一起,石鲈科鱼类未能构成单一分支类群;同时,横带髭鲷为代表的髭鲷属鱼类16S rRNA基因长度74bp的基因片段的RNA二级结构与其余石鲈科种类存在明显的结构差异.因此,研究结果支持将髭鲷属从石鲈科中独立出来形成髭鲷科Haplogeniidae的观点.     

Systematics of the Pezizomycetes--the operculate discomycetes

The Pezizomycetes (order Pezizales) is an early diverging lineage within the Pezizomycotina. A shared derived character, the operculate ascus, supports the Pezizales as monophyletic, although functional opercula have been lost in certain taxa. Phylogenetic relationships within Pezizales were studied using parsimony and Bayesian analyses of partial SSU and LSU rDNA sequences from 100 taxa representing 82 genera and 13 of the 15 families currently recognized. Three primary lineages are identified that more or less correspond to the A, B and C lineages resolved in previous analyses using SSU rDNA: (A) Ascobolaceae and Pezizaceae; (B) Discinaceae-Morchellaceae and Helvellaceae-Tuberaceae; (C) Ascodesmidaceae, Glaziellaceae, Pyronemataceae, Sarcoscyphaceae and Sarcosomataceae. In contrast the monotypic Rhizinaceae and Caloscyphaceae are resolved as two independent lineages. Bayesian analyses support a relationship among Rhizina and two species of Psilopezia (Pyronemataceae). Only lineage C is highly supported. The B and C lineages form a strongly supported monophyletic group. None of these lineages corresponds to earlier proposed suborders. The A and B lineages are supported by certain morphological features (e.g. ascus bluing reaction in iodine, cytology of spores and paraphyses, septal pore structures and excipulum structure); these characters have been subject to homoplasy. Lineage C is the largest and most heterogeneous, and no unifying morphological features support its recognition. The Pyronemataceae, in which almost half of the species in the order are found, is not monophyletic because the Ascodesmidaceae and Glaziellaceae are nested within it. The relationships among all families in the C lineage remain uncertain. The origin of various forms of ascomata, including hypogeous forms (truffles and truffle-like), epigeous cleistothecia, simple reduced apothecia and highly elaborate, stipitate forms (helvelloid and morchelloid), are discussed.     

Towards a subordinal classification of the Pezizales (Ascomycota): phylogenetic analyses of SSU rDNA sequences.

Phylogenetic analyses of partial SSU rDNA sequences from representatives of 36 pezizales associated genera are presented, including new sequences from 28 species: Aleuria aurantiaca, Ascodesmis sphaerospora, Boudiera acanthospora, Caloscypha fulgens, Cheilymenia stercorea, Cookeina sulcipes, Desmazierella acicola, Geopyxis carbonaria, Hydnotrya tulasnei, Iodophanus carneus, Microstoma protracta, Otidea leporina, Paurocotylis pila, Peziza succosa and P vesiculosa (the type species of the family Pezizaceae and the order Pezizales), Pyronema domesticum, Pulvinula archeri, Saccobolus sp., Sarcoscypha austriaca, Sarcosoma globosum, Sarcosphaera coronaria, Scutellinia scutellata and S. torrentis, Sphaerosporella brunnea, Tarzetta catinus, Thelebolus crustaceus, Trichophaea hybrida, Trichophaeopsis bicuspis, and Wilcoxina mikolae. Two taxon and character matrices were subjected to maximum parsimony, maximum likelihood, and neighbor-joining analyses. The first matrix included 28 taxa and a full character set of 1600 bp, and the second matrix 37 taxa and a restricted set of 1053 characters. The analyses using the restricted character set generally yielded the same topology as the full character set but the resolution was reduced. Three main evolutionary lineages were detected within the order: (1) Pezizaceae and Ascobolaceae, (2) Helvellaceae, Morchellaceae, Tuberaceae, and Caloscypha (Otideaceae), and (3) Sarcoscyphaceae, Sarcosomataceae, Ascodes-midaceae, Glaziellaceae, Otideaceae and Pyronemataceae. The inferred subordinal grouping is compared to extant classification schemes of the Pezizales. Sarcosomataceae and Sarcoscyphaceae are recognized as separate monophyletic groups. The analyses did not support recognition of Pyronemataceae, Ascodesmida-ceae, and Glaziellaceae as separate from the Otideaceae. Thelebolus (Thelebolaceae) clusters with extra-pezizalean genera and does not belong to the order.     

Hylid frog phylogeny and sampling strategies for speciose clades

How should characters and taxa be sampled to resolve efficiently the phylogeny of ancient and highly speciose groups? We addressed this question empirically in the treefrog family Hylidae, which contains > 800 species and may be nonmonophyletic with respect to other anuran families. We sampled 81 species (54 hylids and 27 outgroups) for two mitochondrial genes (12S, ND1), two nuclear genes (POMC, c-myc), and morphology (144 characters) in an attempt to resolve higher-level relationships. We then added 117 taxa to the combined data set, many of which were sampled for only one gene (12S). Despite the relative incompleteness of the majority of taxa, the resulting trees placed all taxa in the expected higher-level clades with strong support, despite some taxa being > 90% incomplete. Furthermore, we found no relationship between the completeness of a taxon and the support (parsimony bootstrap or Bayesian posterior probabilities) for its localized placement on the tree. Separate analysis of the data set with the most taxa (12S) gives a somewhat problematic estimate of higher-level relationships, suggesting that data sets scored only for some taxa (ND1, nuclear genes, morphology) are important in determining the outcome of the combined analysis. The results show that hemiphractine hylids are not closely related to other hylids and should be recognized as a distinct family. They also show that the speciose genus Hyla is polyphyletic, but that its species can be arranged into three monophyletic genera. A new classification of hylid frogs is proposed. Several potentially misleading signals in the morphological data are discussed.     

Further revisions of the Sabellidae subfamilies and cladistic relationships among the Fabriciinae (Annelida: Polychaeta)

Cladistic relationships of the sabellid subfamilies Fabriciinae and Sabellinae are examined in light of recent revisions of fabriciin taxa. The potential placement of Caobangia in the Sabellinae is suggested from an initial analysis of selected fabriciin species and genera. Subsequent cladistic analyses at the family level produced over 1800 cladograms, among which Caobangia is the most plesiomorphic taxon of either the Fabriciinae or Sabellinae. Successive approximations weighting reduced this ambiguity, consistently placing Caobangia in the Sabellinae. Subfamilies are emended on the basis of these results. Cladistic relationships of fabriciin taxa, exclusive of Caobangia , display topological instability among some genera and species. Genera are, however, monophyletic in all topologies. Incorporating ontogenetic data for branching ventral filamentous appendages in Augeneriella reduces ambiguity among genera and suggests alternative transformation series for ventral filamentous appendages.     

木灵藓科分类与系统学研究：历史、问题和展望

木灵藓科(Orthotrichaceae)是藓类植物中的第3大科。该科不仅种类多, 生态类型特殊, 而且是世界公认的多样化程度高、分类难度大、系统关系复杂的类群。当代木灵藓科植物分类系统学研究主要集中在该科的地区志编写和专属分类修订。目前, 除了热带美洲、热带非洲的变齿藓属(Zygodon)和火藓属(Schlotheimia)部分类群外, 木灵藓科主要类群的分类修订工作已基本完成, 但是有关亚科和属的划分和地位以及各属之间的关系等方面仍存在众多争议。木灵藓科分支系统学研究也不够系统全面, 有的仅应用了单个基因片段, 或者只涉及少数类群。因此, 需要基于更多的分子和形态学性状, 进一步开展世界木灵藓科植物的系统发育研究, 建立一个更趋自然的木灵藓科分类系统。     

The Ajellomycetaceae, a new family of vertebrate-associated Onygenales

Phylogenies inferred from the analysis of DNA sequence data have shown that the Onygenales contains clades that do not correspond with previously described families. One lineage identified in recent molecular phylogenetic studies includes the dimorphic pathogens belonging to the genera Ajellomyces, Emmonsia and Paracoccidioides. To evaluate the degree of support for this lineage and determine whether it includes additional taxa, we examined relationships among the members of this clade and selected saprobic onygenalean taxa based on maximum-parsimony analyses of partial nuclear large RNA subunit (LSU) and internal transcribed spacer (ITS) sequences. A clade distinct from the Onygenaceae was found to encompass Ajellomyces (including the anamorph genera Blastomyces, Emmonsia and Histoplasma) and Paracoccidioides brasiliensis. The members of this lineage are saprobic and pathogenic vertebrate-associated taxa distinguished by their globose ascomata with coiled appendages, muricate globose or oblate ascospores, and lack of keratinolytic activity. Anamorphs are solitary aleurioconidia or irregular alternate arthroconidia. Based on molecular data and on morphological and physiological similarities among these taxa, we propose the new family, Ajellomycetaceae.     

Testing morphology-based hypotheses of phylogenetic relationships in Parmeliaceae (Ascomycota) using three ribosomal markers and the nuclear RPB1 gene

Parmeliaceae is the largest family of lichen-forming fungi with more than 2000 species and includes taxa with different growth forms. Morphology was widely employed to distinguish groups within this large, cosmopolitan family. In this study we test these morphology-based groupings using DNA sequence data from three nuclear and one mitochondrial marker from 120 taxa that include 59 genera and represent the morphological and chemical diversity in this lineage. Parmeliaceae is strongly supported as monophyletic and six well-supported main clades can be distinguished within the family. The relationships among them remain unresolved. The clades largely agree with the morphology-based groupings and only the placement of four of the genera studied is rejected by molecular data, while four other genera belong to clades previously unrecognised. The classification of these previously misplaced genera, however, has already been questioned by some authors based on morphological evidence. These results support morphological characters as important for the identification of monophyletic clades within Parmeliaceae.     

A molecular phylogeny of Planorboidea (Gastropoda, Pulmonata): insights from enhanced taxon sampling

Planorbid gastropods are the most diverse group of limnic pulmonates, with both discoidal and highspired taxa. Phylogenetic relationships among these genera are confused and controversial. In particular, the monophyly of the limpet‐like taxa (traditionally Ancylidae) is disputed. Even recent molecular studies have concluded that substantially more work is necessary to solve the remaining issues concerning intergeneric phylogenetic relationships and higher taxa systematics. Planorbid snails are of great significance for humans as several members of this group are intermediate hosts of blood flukes (schistosomes) causing a chronic disease, schistosomiasis. We used the two independent molecular markers COI and 18S (concatenated dataset of 2837 nucleotide bp) to infer phylogenetic relationships of 26 genera (27 species) of Planorboidea, represented mostly by type species from mainly topotypical populations. With the majority of the taxa discussed not having been studied previously, this study attempted to test several hypotheses on planorbid phylogenetic relationships using Bayesian inference techniques. The monophyly of Planorboidea (= ‘Ancyloplanorbidae’) is strongly suggested on the basis of our extensive molecular analysis. Besides a distinct Burnupia clade, two major clades were recovered that correspond to family level taxa (traditional Bulinidae and Planorbidae). Considerable rearrangements of suprageneric taxa are evident from the phylogeny inferred. Therefore, the only clades recognized by current classifications and supported by our analysis are Planorbini and Segmentinini. The present study found that Ancylidae as traditionally understood, i.e. covering most freshwater limpet gastropods, is paraphyletic, as the genera of Burnupia and Protancylus have been shown to lie phylogenetically outside the Ancylini. Chromosome numbers and levels of polyploidy are discussed in the light of the new phylogeny. An earlier theory of shell shape evolution, i.e. that of patelliform taxa being most advanced, was not supported by this study; a limpet‐shaped taxon is most basal within Planorboidea. Although many taxa still remain to be studied, our results will hopefully contribute towards a better understanding of this very important group of freshwater organisms. Some taxonomic implications are discussed.     

Molecular genetics and speciation in Elliptio and its relationships to other taxa of North American Unionidae (Bivalvia)

The genetic relationships among 30 populations of 11 species and five genera of North American Unionidae were assessed by using standard allozyme procedures. Emphasis was on relationships among populations and species of Elliptio and Fusconaia. Multi-dimensional scaling based on a matrix of Nei's (1972) genetic distances substantiated the immunoelectrophoretic results of Davis&Fuller 1981, which demonstrated the distinct and divergent taxonomic groups Anodontinae, Margaritiferinae, and Ambleminae, plus die close relationship of Elliptio and Fusconaia , which justifies their inclusion within the same tribe. Genetic distance appears to increase regularly with time since divergence of taxa. The E. complanata species group is an apparently recent radiation and probably is actively radiating today. The I values among species of this group range from 0.90 to 0.99. Considerable heterozygosity, numerous polymorphic loci, and much interpopuladon phenotypic diversity was also recorded for this group. Some taxa mat have been considered synonyms are demonstrated to be valid species. Reasons for the low genetic distances among unionid taxa are discussed. Standard allozyme analyses are shown to be of great value for assessing relationships among unionid taxa.     

Evolutionary diversification of spiny rats (genus Trinomys, Rodentia: Echimyidae) in the Atlantic Forest of Brazil

Phylogenetic and phylogeographic relationships within and among species of the Atlantic Forest spiny rat Trinomys (family Echimyidae) were examined using cytochrome b sequence data. Levels of sequence divergence among species of Trinomys are as high as those found among taxa of echimyids that are recognized as different genera. Trinomys contains three distinct monophyletic clades that show a striking concordance with vegetational distribution. Haplotypes of clade 1 are distributed along the coastal margins of southeastern Brazil, following the moist tropical forest. Members of clade 2 are found in the semi-deciduous tropical forest. T. albispinus represents clade 3 and is found in a more xeric vegetation. Estimates of divergence times separating the three clades are very deep and range from 1.6 to 7.4 millions of years, predating the climatic fluctuations of the Pleistocene. Therefore, the proposed Late Pleistocene refugia in the Atlantic Forest cannot account for the divergence of the clades of Trinomys , but most likely shaped the modern distribution of species. The current taxonomy of this group does not reflect the diversity and phylogenetic relationships of the named species. However, morphological characters are congruent with the phylogeny uncovered by the molecular data. An extensive taxonomic rearrangement is suggested, reflecting phylogenetic relationships of monophyletic entities within the genus Trinomys , degree of sequence differences, and morphological diagnosability.