Is xenodontine snake reproduction shaped by ancestry,more than by ecology?

One of the current challenges of evolutionary ecology is to understand the effects of phylogenetic history (PH) and/or ecological factors (EF) on the life‐history traits of the species. Here, the effects of environment and phylogeny are tested for the first time on the reproductive biology of South American xenodontine snakes. We studied 60% of the tribes of this endemic and most representative clade in a temperate region of South America. A comparative method (canonical phylogenetic ordination—CPO) was used to find the relative contributions of EF and PH upon life‐history aspects of snakes, comparing the reproductive mode, mean fecundity, reproductive potential, and frequency of nearly 1,000 specimens. CPO analysis showed that PH or ancestry explained most of the variation in reproduction, whereas EF explained little of this variation. The reproductive traits under study are suggested to have a strong phylogenetic signal in this clade, the ancestry playing a big role in reproduction. The EF also influenced the reproduction of South American xenodontines, although to a lesser extent. Our finding provides new evidence of how the evolutionary history is embodied in the traits of living species.     

Are Diet Preferences Associated to Skulls Shape Diversification in Xenodontine Snakes?

Snakes are a highly successful group of vertebrates, within great diversity in habitat, diet, and morphology. The unique adaptations for the snake skull for ingesting large prey in more primitive macrostomatan snakes have been well documented. However, subsequent diversification in snake cranial shape in relation to dietary specializations has rarely been studied (e.g. piscivory in natricine snakes). Here we examine a large clade of snakes with a broad spectrum of diet preferences to test if diet preferences are correlated to shape variation in snake skulls. Specifically, we studied the Xenodontinae snakes, a speciose clade of South American snakes, which show a broad range of diets including invertebrates, amphibians, snakes, lizards, and small mammals. We characterized the skull morphology of 19 species of xenodontine snakes using geometric morphometric techniques, and used phylogenetic comparative methods to test the association between diet and skull morphology. Using phylogenetic partial least squares analysis (PPLS) we show that skull morphology is highly associated with diet preferences in xenodontine snakes.     

Phylogenetic relationships of thorny catfishes (Siluriformes: Doradidae) inferred from molecular and morphological data

Doradidae is a putatively monophyletic group of South American freshwater catfishes containing 30 extant genera and 72 valid species. Only one study to date has attempted to estimate phylogenetic relationships among doradids. This morphological analysis partitioned species into two basal genera ( Wertheimeria and Francisodoras ) and a crown group of three subfamilies (Platydoradinae, Astrodoradinae and Doradinae) whose relationships were unresolved. No subsequent work has been done to resolve the subfamilial trichotomy or to assess whether postulated intergeneric relationships are accurate. We address this problem with complete sequences (2.5 kilobases, kb) of mitochondrial 12S and 16S rRNA genes and partial (1.3 kb) sequences of the nuclear elongation factor-1 alpha (EF1α) gene from representatives of 23 doradid genera (43 species) and 13 outgroups from additional siluriform families. Phylogenetic analysis of these data yields strong support for the monophyly of Doradidae and Astrodoradinae (as well as other relationships), but otherwise shows significant conflict with morphological results. A partial re-examination of published morphological data indicates that many characters may have been incorrectly polarized and many taxa have incorrect state assignments. Our results provide a framework for ongoing efforts to describe the species-level diversity of this poorly understood neotropical family.  © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society , 2004, 140 , 551–575.     

基于12S,16S和28S rRNA基因序列的中国小毛瓢虫属系统发育分析

【目的】小毛瓢虫属Scymnus Kugelann昆虫主要捕食蚜虫、蚧虫等害虫,是一类经济上重要的天敌昆虫。目前针对小毛瓢虫属的系统发育研究尚属空白,亚属之间的系统演化关系尚不明确,为了建立合理的分类系统,亟需对小毛瓢虫属的亲缘关系进行研究和探讨。【方法】以华南农业大学馆藏的小毛瓢虫属5亚属共44种为研究对象,采用PCR技术对12S, 16S和28S rRNA基因的部分序列进行扩增;运用MEGA 7.0分析了小毛瓢虫属内12S, 16S和28S rRNA基因的碱基组成,基于K2P模型计算了小毛瓢虫属44种的种间遗传距离;采用最大似然法(maximum-likelihood, ML)和贝叶斯推断法(Bayesian-inference, BI)构建该属的系统发育树。【结果】扩增获得小毛瓢虫属44种的12S rRNA基因序列平均长度为356 bp, 16S rRNA基因序列平均长度为351 bp, 28S rRNA基因序列平均长度为315 bp;序列分析表明,12S rRNA基因的A, T, G和C平均含量分别为38.8%, 43.5%, 11.9%和5.8%, 16S rRNA基因的A, T, G和C平均含量分别为37.6%, 40.3%, 14.4%和7.7%, 28S rRNA基因的A, T, G和C平均含量分别为26.7%, 18.3%, 31.4%和23.5%;基于联合序列分析的种间遗传距离为0.004～0.276,平均遗传距离为0.115。系统发育分析结果表明,小毛瓢虫属为单系起源,而小毛瓢虫亚属Scymnus(Scymnus) Kugelann、毛瓢虫亚属Scymnus(Neopullus) Sasaji、小瓢虫亚属Scymnus(Pullus) Mulsant和拟小瓢虫亚属Scymnus(Parapullus) Yang均为并系起源。【结论】基于12S, 16S和28S rRNA基因序列的小毛瓢虫属系统发育分析显示传统的形态学分类体系与基于分子数据分析的结果部分不一致,这表明应该对该属内各亚属的鉴别特征进行全面检视,筛选并确立各亚属的形态指标,同时也表明该属内的亚属分类单元需重新厘定。     

Dissecting the major American snake radiation: A molecular phylogeny of the Dipsadidae Bonaparte (Serpentes,Caenophidia)

The Dipsadidae contains more than 700 extant species belonging to 92 genera and is the largest family of American snakes. In this work, we built a data set including two mitochondrial genes (12S and 16S rRNA) for 125 dipsadid taxa belonging to 59 genera, in order to gain further insights on the phylogenetic relationships of this large group at the subfamilial and generic levels. Among dipsadines, the monotypic genus Nothopsis is the sister-group to Leptodeira. Among xenodontines, the monophyly of seven previously recognized tribes (Alsophiini, Elapomorphini, Hydropsini, Philodryadini, Pseudoboini, Tachymenini and Xenodontini) is confirmed. Among Xenodontini, the genus Liophis is paraphyletic with respect to Erythrolamprus and Umbrivaga and workers should be aware of the inadequacy of the current taxonomy. Finally, the following genera could not confidently be allocated to the above tribes: Caaeteboia, Echinantera and Taeniophallus, Tropidodryas, Manolepis and Pseudalsophis, Xenopholis, Psomophis, Hydrodynastes, Conophis and Crisantophis.     

凤蝶亚科(凤蝶科,鳞翅目)16S rRNA基因的分子系统发生分析

对15种凤蝶亚科蝶类线粒体16S rRNA基因部分序列进行了测定,并结合GenBank中其它相关类群的序列,采用邻接法(NJ)、最大简约法(MP)、最大似然法(ML)和贝叶斯法构建凤蝶亚科的分子系统树,探讨该亚科各类群间的系统发生关系.结果表明,燕凤蝶族构成凤蝶亚科蝶类系统树基部的一个独立分支;燕凤蝶族和裳凤蝶族为单系发生,且裳凤蝶族聚在凤蝶族内部;喙凤蝶族的单系性尚不能确定.综合分子系统学、形态学及寄主植物等相关证据,推测斑凤蝶类为凤蝶族中早期分化的一支;较之裳凤蝶类,斑凤蝶类可能更早从二者最近的共同祖先中分化出来.     

Higher-level snake phylogeny inferred from mitochondrial DNA sequences of 12S rRNA and 16S rRNA genes

Portions of two mitochondrial genes (12S and 16S ribosomal RNA) were sequenced to determine the phylogenetic relationships among the major clades of snakes. Thirty-six species, representing nearly all extant families, were examined and compared with sequences of a tuatara and three families of lizards. Snakes were found to constitute a monophyletic group (confidence probability [CP] = 96%), with the scolecophidians (blind snakes) as the most basal lineages (CP = 99%). This finding supports the hypothesis that snakes underwent a subterranean period early in their evolution. Caenophidians (advanced snakes), excluding Acrochordus, were found to be monophyletic (CP = 99%). Among the caenophidians, viperids were monophyletic (CP = 98%) and formed the sister group to the elapids plus colubrids (CP = 94%). Within the viperids, two monophyletic groups were identified: true vipers (CP = 98%) and pit vipers plus Azemiops (CP = 99%). The elapids plus Atractaspis formed a monophyletic clade (CP = 99%). Within the paraphyletic Colubridae, the largely Holarctic Colubrinae was found to be a monophyletic assemblage (CP = 98%), and the Xenodontinae was found to be polyphyletic (CP = 91%). Monophyly of the henophidians (primitive snakes) was neither supported nor rejected because of the weak resolution of relationships among those taxa, except for the clustering of Calabaria with a uropeltid, Rhinophis (CP = 94%).      

从线粒体基因探讨中国大头蛙群的分类及其属内地位

Partial sequences of the mitochondrial 12S rRNA and 16S rRNA gene were determined for 8 populations of three species of Chinese Limnonectes, and aligned with the published sequences of Limnonectes from other parts of the world. When Nanorana parker, Paa boulengeri, Fejervarya limnocharis and Hoplobatrachus rugulosus was used as outgroup taxa (Accession Nos. AY158705, AY313685, AF206111, AF206491, AY322311). The sequences of the 12S rRNA and 16S rRNA genes totaled 950 nueleotide positions with gaps including 510 variable sites. We reconstructed phylogenetie trees using Clustal X 1.8, Mega 2.1 and PHYLIP 3.5e software, and using the maximum parsimony and maximum likelihood methods, respectively. Our analyses suggest that these fanged frogs from China are another monophyletie group in addition to the four monophyletie groups identified by previous studies. The Chinese Limnonectes were grouped into three elades (BCL 55% ). The first elade contains one species (BCL 100% ), from a population of Limnoneetes fragilis from Hainan Province. The second contains four individuals (BCL 100% ), i. e. two populations of Limnonectes kuhlii from Yunnan Province. The third contains one species (BCL 100% ), i. e. five populations of Limnonectes fujianensis from Fujian Province and 1 from Taiwan Province. The resulted phylogenetie trees indicate L. fragilis is basal to L. kuhlii L. fujianensis 。     

Phylogenetic relationships within the Mysidae (Crustacea, Peracarida, Mysida) based on nuclear 18S ribosomal RNA sequences

Species of the order Mysida (Crustacea, Peracarida) are shrimp-like animals that occur in vast numbers in coastal regions of the world. The order Mysida comprises 1,053 species and 165 genera. The present study covers 25 species of the well-defined Mysidae, the most speciose family within the order Mysida. 18S rRNA sequence analysis confirms that the subfamily Siriellinae is monophyletic. On the other hand the subfamily Gastrosaccinae is paraphyletic and the subfamily Mysinae, represented in this study by the tribes Mysini and Leptomysini, consistently resolves into three independent clades, and hence is clearly not monophyletic. The tribe Mysini is not monophyletic either, and forms two clades of which one appears to be closely related to the Leptomysini. Our results are concordant with a number of morphological differences urging a taxonomic revision of the Mysidae.     

What are the closest relatives of the hot-spring snakes (Colubridae, Thermophis), the relict species endemic to the Tibetan Plateau?

We conducted phylogenetic analyses to identify the closest related living relatives of the Xizang and Sichuan hot-spring snakes (T. baileyi and T. zhaoermii) endemic to the Tibetan Plateau, using mitochondrial DNA sequences (cyt b, ND4) from eight specimens, together with sequences from 95 additional caenophidian and five henophidian genera that were downloaded from GenBank. Phylogenetic trees were obtained using Bayesian Inference and Maximum likelihood methods. Results suggest that hot-spring snakes, which are adapted to high and cold environments, were clustered in the monophyletic Xenodontinae. Xenodontinae is one of the largest subfamilies of colubrid snakes, with about 90 genera and more than 500 species known, and are primarily tropical snakes previously thought to be restricted to the New World. Our data failed to provide any evidence that the New World xenodontines diverged from Thermophis and dispersed into the New World, also failed to suggest a colonization of Asia by New World xenodontines by dispersal from the New World. An alternative plausible scenario may be that Thermophis and the New World xenodontines evolved independently in Asia and America, respectively, after the divergence of their common ancestor. The divergence of the two species in Thermophis was caused by the barrier of the Hengduan Mountains, and the speciation had almost occurred when Tibetan Plateau attained present elevation.     

A Family Level Analysis of Tardigrade Phylogeny

In the present study a character data set suitable for cladistic analysis at the family level was developed. A data matrix consisting of 50 morphological characters from 15 families of tardigrades was analyzed by maximum parsimony. Kinorhynchs, loriciferans, and gastrotrichs were used as outgroups. The results agree with the currently accepted hypothesis that Eutardigrada and Heterotardigrada are distinct monophyletic groups. Among the eutardigrades, Eohypsibiidae was found to be a sister group to Macrobiotidae+Hypsibiidae, while Milnesiidae was the basal eutardigrade family. The basal heterotardigrade family was found to be Oreellidae. Echiniscoideans grouped with some traditional Arthrotardigrada (Renaudarctidae, Coronarctidae+Batillipedidae) suggesting that the arthrotardigrades are not monophyletic. The 18S rRNA gene sequence of Batillipes mirus Richters, 1909 and Calohypsibius schusteri Nelson & McGlothlin, 1996 were obtained and their addition to a previously published dataset supports the monophyly of Heterotardigrada and of Parachela versus Apochela within the Eutardigrada.     

Molecular phylogenetics of the spider infraorder Mygalomorphae using nuclear rRNA genes (18S and 28S): conflict and agreement with the current system of classification

Mygalomorph spiders, which include the tarantulas, trapdoor spiders, and their kin, represent one of three main spider lineages. Mygalomorphs are currently classified into 15 families, comprising roughly 2500 species and 300 genera. The few published phylogenies of mygalomorph relationships are based exclusively on morphological data and reveal areas of both conflict and congruence, suggesting the need for additional phylogenetic research utilizing new character systems. As part of a larger combined evidence study of global mygalomorph relationships, we have gathered approximately 3.7 kb of rRNA data (18S and 28S) for a sample of 80 genera, representing all 15 mygalomorph families. Taxon sampling was particularly intensive across families that are questionable in composition-Cyrtaucheniidae and Nemesiidae. The following primary results are supported by both Bayesian and parsimony analyses of combined matrices representing multiple 28S alignments: (1) the Atypoidea, a clade that includes the families Atypidae, Antrodiaetidae, and Mecicobothriidae, is recovered as a basal lineage sister to all other mygalomorphs, (2) diplurids and hexathelids form a paraphyletic grade at the base of the non-atypoid clade, but neither family is monophyletic in any of our analyses, (3) a clade consisting of all sampled nemesiids, Microstigmata and the cyrtaucheniid genera Kiama, Acontius, and Fufius is consistently recovered, (4) other sampled cyrtaucheniids are fragmented across three separate clades, including a monophyletic North American Euctenizinae and a South African clade, (5) of the Domiothelina, only idiopids are consistently recovered as monophyletic; ctenizids are polyphyletic and migids are only weakly supported. The Domiothelina is not monophyletic. The molecular results we present are consistent with more recent hypotheses of mygalomorph relationship; however, additional work remains before mygalomorph classification can be formally reassessed with confidence-increased taxonomic sampling and the inclusion of additional character systems (more genes and morphology) are required.     

用mtDNA 12S rRNA序列变异检验鲤形目鱼类系统发育关系

通过对鲤形目鱼类5个科的代表类群的完整线粒体12S rRNA进行测序和分析,以检验目前的形态学假说。经序列比对后,有1000个位点,其中467个位点在茎区,533个在环区;有395个位点为变化位点,其中267个为系统发育信息位点。采用邻接法和最大简约法进行了系统发育分析,其结果支持鲤科鱼类成为一个单系群,非鲤科的鲤形目鱼类成为另一个单系群的观点,这与Siebert提出的假说相一致。鲤科鱼类包含3个主要的分支,即鱼丹系、鲤系和雅罗鱼系;但在非鲤科鲤形目鱼类中,其关系不能得到很好的解决,其中鳅科是复系,平鳍鳅科、条鳅亚科和花鳅亚科可能有较近的亲缘关系。     

Evidence for phylogenetic congruence among sulfur-oxidizing chemoautotrophic bacterial endosymbionts and their bivalve hosts

Sulfur-oxidizing chemoautotrophic (thioautotrophic) bacteria are now known to occur as endosymbionts in phylogenetically diverse bivalve hosts found in a wide variety of marine environments. The evolutionary origins of these symbioses, however, have remained obscure. Comparative 16S rRNA sequence analysis was used to investigate whether thioautotrophic endosymbionts are monophyletic or polyphyletic in origin and to assess whether phylogenetic relationships inferred among these symbionts reflect those inferred among their hosts. 16S rRNA gene sequences determined for endosymbionts from nine newly examined bivalve species from three families (Vesicomyidae, Lucinidae, and Solemyidae) were compared with previously published 16S rRNA sequences of thioautotrophic symbionts and free-living bacteria. Distance and parsimony methods were used to infer phylogenetic relationships among these bacteria. All newly examined symbionts fall within the gamma subdivision of the Proteobacteria, in clusters containing previously examined symbiotic thioautotrophs. The closest free-living relatives of these symbionts are bacteria of the genus Thiomicrospira. Symbionts of the bivalve superfamily Lucinacea and the family Vesicomyidae each form distinct monophyletic lineages which are strongly supported by bootstrap analysis, demonstrating that host phylogenies inferred from morphological and fossil evidence are congruent with phylogenies inferred for their respective symbionts by molecular sequence analysis. The observed congruence between host and symbiont phylogenies indicates shared evolutionary history of hosts and symbiont lineages and suggests an ancient origin for these symbioses. Correspondence to: D.L. Distel     

基于28S rRNA D2序列的内茧蜂亚科的分子系统发育

首次利用同源28S rRNA D2基因序列对内茧蜂亚科Rogadinae （昆虫纲Insecta：膜翅目Hymenoptera：茧蜂科Braconidae）进行了分子系统学研究。本研究从95%～100%乙醇浸渍保存的标本中提取基因组DNA并扩增了10种内群种类和5种外群种类的28S rDNA D2片段并测序（GenBank序列号AY167645-AY167659）,利用BLAST搜索相关的同源序列, 采用了GenBank中13个种类的28S rRNA D2同源序列,然后据此进行分子分析。利用3个外群（共8个种类）和3种建树方法 (距离邻近法distance based neighbor joining, NJ; 最大俭约法maximum parsimony, MP; 和最大似然法maximum likelihood, ML)分析了内茧蜂亚科内的分子系统发育关系。结果表明,由分子数据产生的不同的分子系统树均显示内茧蜂亚科是一个单系群。内茧蜂亚科内依据形态和生物学特征的分群（族和亚族）及其系统发育关系得到部分支持。NJ、MP和ML分析结果均表明内茧蜂族Rogadini不是一个单系,而是一个并系,其余3族则得到不同程度的支持。内茧蜂族可分成2个分支：“脊茧蜂属Aleiodes+弓脉茧蜂属Arcaleiodes”和“沟内茧蜂属Canalirogas+锥齿茧蜂属Conspinaria+刺茧蜂属Spinaria+内茧蜂属Rogas”,二者不是姐妹群。脊茧蜂属Aleiodes和弓脉茧蜂属Arcaleiodes始终是姐妹群。脊茧蜂属Aleiodes是一个单系,并可分成2个姐妹分支,这与依据形态和生物学特征的亚属分群相一致。弓脉茧蜂属Arcaleiodes Chen et He,1991是一个独立的属。分支“沟内茧蜂属Canalirogas+锥齿茧蜂属Conspinaria+刺茧蜂属Spinaria+内茧蜂属Rogas”的单系性仅得到部分分子数据的支持;因形态特异（腹部成甲壳状）而列为亚族级的刺茧蜂属Spinaria,分子分析没有证实这一点。横纹茧蜂族Clinocentrini是个单系,并在内茧蜂亚科的系统发育中处于基部（原始）的位置。我们研究结果还表明,阔跗茧蜂属Yelicones和潜蛾茧蜂属Stiropius相对应的阔跗茧蜂族Yeliconini和潜蛾茧蜂族Stiropiini为2个独立的分支, 与形态和生物学的结果一致,但它们在内茧蜂亚科的系统发育的位置不明,有待今后进一步研究。     

The Palaeoptera Problem: Basal Pterygote Phylogeny Inferred from 18S and 28S rDNA Sequences

Monophyly of the pterygote insects is generally accepted, but the relationships among the three basal branches (Odonata, Ephemeroptera and Neoptera) remain controversial. The traditional view, to separate the pterygote insects in Palaeoptera (Odonata + Ephemeroptera) and Neoptera, based on the ability or inability to fold the wings over the abdomen, has been questioned. Various authors have used different sets of morphological characters in support of all three possible arrangements of the basal pterygote branches. We sequenced 18S and 28S rDNA from 18 species of Odonata, 8 species of Ephemeroptera, 2 species of Neoptera, and 1 species of Archaeognatha in our study. The new sequences, in combination with sequences from GenBank, have been used in a parsimony jackknife analysis resulting in strong support for a monophyletic Palaeoptera. Morphological evidence and the phylogenetic implications for understanding the origin of insect flight are discussed.     

Reconstructing the phylogeny of the Sipuncula

Sipunculans are marine spiralian worms with possible close affinities to the Mollusca or Annelida. Currently 147 species, 17 genera, 6 families, 4 orders and 2 classes are recognized. In this paper we review sipunculan morphology, anatomy, paleontological data and historical affiliations. We have conducted cladistic analyses for two data sets to elucidate the phylogenetic relationships among sipunculan species. We first analyzed the relationships among the 45 species of Phascolosomatidea with representatives of the Sipunculidea as outgroups, using 35 morphological characters. The resulting consensus tree has low resolution and branch support is low for most branches. The second analysis was based on DNA sequence data from two nuclear ribosomal genes (18S rRNA and 28S rRNA) and one nuclear protein-coding gene, histone H3. Outgroups were chosen among representative spiralians. In a third analysis, the molecular data were combined with the morphological data. Data were analyzed using parsimony as the optimality criterion and branch support evaluated with jackknifing and Bremer support values. Branch support for outgroup relationships is low but the monophyly of the Sipuncula is well supported. Within Sipuncula, the monophyly of the two major groups, Phascolosomatidea and Sipunculidea is not confirmed. Of the currently recognized families, only Themistidae appears monophyletic. The Aspidosiphonidae, Phascolosomatidae and Golfingiidae would be monophyletic with some adjustments in their definition. The Sipunculidae is clearly polyphyletic, with Sipunculus nudus as the sister group to the remaining Sipuncula, Siphonosoma cumanense the sister group to a clade containing Siphonosoma vastumand the Phascolosomatidea, and Phascolopsis gouldi grouping within the Golfingiiformes, as suggested previously by some authors. Of the genera with multiple representatives, only Phascolosoma and Themiste are monophyletic as currently defined. We are aiming to expand our current dataset with more species in our molecular database and more detailed morphological studies.     

A molecular phylogeny for aplocheiloid fishes (Atherinomorpha, Cyprinodontiformes): the role of vicariance and the origins of annualism

Annual aplocheiloid killifish embryos possess a rare ability among vertebrates to enter stages of developmental arrest (diapause) when subjected to adverse environmental conditions. Previous morphological analyses have presented disparate hypotheses regarding the evolution of the intriguing life history associated with this phenomenon. We present a novel hypothesis of aplocheiloid relationships based on 1,009 bp of sequence data from three mitochondrial genes (cytochrome b, 12S rRNA, and 16S rRNA). Phylogenetic analysis using maximum parsimony, neighbor- joining, and maximum likelihood produce strongly congruent topologies. Our data confirm the monophyly of the Neotropical family Rivulidae, while demonstrating a paraphyletic Old World assemblage. The basal sister group position of Indo-Malaysian and Madagascaran taxa relative to a monophyletic South American/African dichotomy strongly indicates the role of vicariance in the diversification of these fishes in spite of their definition as secondary freshwater fish. The distribution of annualism onto this topology implies a single early origin for this suite of characters, prior to the divergence of South American and African taxa. If so, then annualism has since been lost several times during the evolution of genera now residing in permanent aquatic habitats. Paleoclimatic knowledge complements this scenario based on molecular characters.      

基于叶绿体16S rRNA的绿色裸藻类系统发育及性状进化研究

该研究基于叶绿体16S rRNA基因序列,构建绿色裸藻类的系统发育树,并对绿色裸藻类植物8个形态性状进行祖先重建分析,以明确绿色裸藻类植物的系统演化关系,为研究该类植物的起源提供理论依据。结果表明：(1)贝叶斯法构建的绿色裸藻类系统发育树显示,双鞭藻属与拟双鞭藻属互为姐妹群,扁裸藻属、鳞孔藻属和盘裸藻属亲缘关系较近,而囊裸藻属和陀螺藻属亲缘关系较近,裸藻属、隐裸藻属、柄裸藻属和旋形藻属亲缘关系较近,表明裸藻属不是一个单系类群。(2)基于形态性状的祖先重建结果显示,绿色裸藻类相对原始的7个性状包括：表质柔软易变形,出现螺旋形线纹,细胞后端渐尖或尖尾刺状,无囊壳,叶绿体为片状、盾状或大盘状,具无鞘蛋白核,副淀粉粒为小颗粒状且数量不定,而鞭毛长度不能推断可能的祖先状态。(3)综合8种性状祖先重建结果发现,裸藻属和眼裸藻属植物具有所有原始性状,可能是最先出现的绿色裸藻类的祖先。     

Phylogeny of Thalassinidea (Crustacea, Decapoda) inferred from three rDNA sequences: implications for morphological evolution and superfamily classification

The infraorder Thalassinidea is a group of cryptic marine burrowing decapods of which the higher taxonomy is often contentious. The present analysis attempts to reconstruct phylogenetic relationship among 12 of the 13 currently recognized families using partial nuclear 18S, 28S rDNA and mitochondrial 16S rDNA sequences. The infraorder is divided into two distinct clades, with the first clade consisting of Thalassinidae, Laomediidae, Axianassidae and Upogebiidae, and the second clade including Axiidae, Calocarididae, Eiconaxiidae, Callianassidae, Ctenochelidae, Micheleidae, Strahlaxiidae and Callianideidae. Within the first clade, the Upogebiidae is the basal family. The Axianassidae shows low affinity to other laomediid genera indicating that it is a valid family. The interfamilial relationships are less well resolved in the second clade. The Axiidae is paraphyletic with respect to Calocarididae and Eiconaxiidae. Thus, the status of these two latter families is not supported if the currently defined Axiidae is maintained. All three families appear to be basal in the thalassinidean clade. The Micheleidae is closely related to the Callianideidae and they form a sister group to the Strahlaxiidae. The monophyletic Callianassidae aligns with the Micheleidae + Callianideidae + Strahlaxiidae clade. The relationship among the Axiidae + Calocarididae + Eiconaxiidae clade, Callianassidae + Micheleidae + Callianideidae + Strahlaxiidae clade and the Ctenochelidae cannot be resolved which might be due to a rapid radiation of the three lineages. Our results do not support the generally used classification scheme of Thalassinidea and suggest that the infraorder might be divided into two superfamilies instead of three as suggested based on larval morphology, second pereiopod morphology in adults and gastric mill structure. The two superfamilies are Thalassinoidea (i.e. Thalassinidae, Laomediidae, Upogebiidae and Axianassidae) and Callianassoidea (i.e. Axioidea + Callianassoidea, as defined in Martin and Davis (2001) but excluding Laomediidae and Upogebiidae). It also appears that gill‐cleaning adaptations are important in thalassinidean evolution while the presence of linea thalassinica is a result of parallel evolution.