白腰雪雀分类地位的商榷

自腰雪雀Onychostruthus taczanowskii(Przewalski)的分类地位比较混乱.在早期的分类系统中,它被归属于雪雀属Montifringilla下.后期由于生态习性与行为特征的不同,被划分至地雀属Pyrgilauda下;又有将它划分为独立属--高原雀属Onychostruthus的观点.本文结合身体量衡度数值特征、外部形态特征以及遗传差异上的研究,综合探讨白腰雪雀的分类地位.对量衡度特征的因子分析发现:白腰雪雀与地雀属种类在体长、体重、翅长、尾长、嘴长与跗蹠长上明显不同,其体形明显偏大.形态特征的聚类分析显示:白腰雪雀与地雀属种类的平均特征差异为0.3902～0.5122,而这些种类间平均特征差异为0.1281～0.2195.比较属间差异发现:石雀Petronia petronia与地雀属种类为0.4878～0.5385,树麻雀Passer montanus与地雀属种类为0.4872～0.5610.麻雀属与石雀属为0.3415,这些结果显示自腰雪雀与地雀属种类的差异已经达到石雀属、麻雀属与地雀属属间的差异.通过比较白腰雪雀与石雀的遗传差异(0.2578),地雀属种类与石雀的遗传差异(0.2386～0.3193),发现白腰雪雀与地雀属种类具有较大的遗传差异(0.2267～0.3143),几近于地雀属与石雀属间的差异.综合量衡度、形态以及遗传等特征的分析结果,作者认为白腰雪雀与地雀属种类有较大的差异,两者间的差异已经达到了它们与近缘属石雀属和麻雀属间的差异,以及近缘属之间的差异,因此,建议白腰雪雀应作为一个独立的属,高原雀属Onychostruthus.     

Multivariate analyses of morphological characters of Leptolaena Thouars s.l. subgenera Mediusella and Xerochlamys (Sarcolaenaceae)

Leptolaena Thouars is one of the first described genera within Sarcolaenaceae, but represents the last great species-level taxonomic challenge in this endemic Malagasy plant family. As currently circumscribed, this genus comprises three subgenera, two of which, Mediusella Cavaco and Xerochlamys (Baker) Cavaco, exhibit patterns of morphological variation that have been understood differently and have led to an unstable taxonomy, such that a consensus on the delimitation of species has yet to be reached. Principal component analysis of morphological characters was performed on 211 herbarium specimens in order to evaluate the morphological variation within the two subgenera and to clarify historically problematical species boundaries. The results showed that ten entities could be distinguished on the basis of vegetative, floral, and fruit characters, and that they provide a robust basis for proposing a new species-level taxonomic framework.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 559–574.     

Phylogenetic study of the species within the family Streptomycetaceae

Species of the genus Streptomyces, which constitute the vast majority of taxa within the family Streptomycetaceae, are a predominant component of the microbial population in soils throughout the world and have been the subject of extensive isolation and screening efforts over the years because they are a major source of commercially and medically important secondary metabolites. Taxonomic characterization of Streptomyces strains has been a challenge due to the large number of described species, greater than any other microbial genus, resulting from academic and industrial activities. The methods used for characterization have evolved through several phases over the years from those based largely on morphological observations, to subsequent classifications based on numerical taxonomic analyses of standardized sets of phenotypic characters and, most recently, to the use of molecular phylogenetic analyses of gene sequences. The present phylogenetic study examines almost all described species (615 taxa) within the family Streptomycetaceae based on 16S rRNA gene sequences and illustrates the species diversity within this family, which is observed to contain 130 statistically supported clades, as well as many unsupported and single member clusters. Many of the observed clades are consistent with earlier morphological and numerical taxonomic studies, but it is apparent that insufficient variation is present in the 16S rRNA gene sequence within the species of this family to permit bootstrap-supported resolution of relationships between many of the individual clusters.     

Numerical taxonomic analysis of imperfect yeast species in Candida and Torulopsis shows no basis for generic separation

A numerical taxonomic analysis was performed on 79 phenotypic characters of 147 imperfect yeast species currently assigned to the genus Candida. The characters used were drawn from two monographs on yeast taxonomy. The analysis revealed 10 clusters of three or more species that were similar at the level of 75% or more, and seven clusters containing only one or two species. None of the 10 major clusters contained exclusively species that were traditionally assigned to the genus Torulopsis, while the 12 Candida species of basidiomycetous affinity fell into three clusters with only one species of ascomycetous affinity included. Statistical determination of the five most important differential characters for each cluster failed to show the property of pseudomycelium/mycelium formation as significant for any cluster. The study provides no evidence to support a distinction between taxa that were formerly divided between the genera Candida and Torulopsis and supports previous proposals that these genera should be fused.     

Transoceanic dispersal and subsequent diversification on separate continents shaped diversity of the Xanthoparmelia pulla group (Ascomycota)

In traditional morphology-based concepts many species of lichenized fungi have world-wide distributions. Molecular data have revolutionized the species delimitation in lichens and have demonstrated that we underestimated the diversity of these organisms. The aim of this study is to explore the phylogeography and the evolutionary patterns of the Xanthoparmelia pulla group, a widespread group of one of largest genera of macrolichens. We used a dated phylogeny based on nuITS and nuLSU rDNA sequences and performed an ancestral range reconstruction to understand the processes and explain their current distribution, dating the divergence of the major lineages in the group. An inferred age of radiation of parmelioid lichens and the age of a Parmelia fossil were used as the calibration points for the phylogeny. The results show that many species of the X. pulla group as currently delimited are polyphyletic and five major lineages correlate with their geographical distribution and the biosynthetic pathways of secondary metabolites. South Africa is the area where the X. pulla group radiated during the Miocene times, and currently is the region with the highest genetic, morphological and chemical diversity. From this center of radiation the different lineages migrated by long-distance dispersal to others areas, where secondary radiations developed. The ancestral range reconstruction also detected that a secondary lineage migrated from Australia to South America via long-distance dispersal and subsequent continental radiation.     

Lichen chemistry is concordant with multilocus gene genealogy in the genus Cetrelia (Parmeliaceae,Ascomycota)

The lichen genus Cetrelia represents a taxonomically interesting case where morphologically almost uniform populations differ considerably from each other chemically. Similar variation is not uncommon among lichenized fungi, but it is disputable whether such populations should be considered entities at the species level. Species boundaries in Cetrelia are traditionally delimited either as solely based on morphology or as combinations of morpho- and chemotypes. A dataset of four nuclear markers (ITS, IGS, Mcm7, RPB1) from 62 specimens, representing ten Cetrelia species, was analysed within Bayesian and maximum likelihood frameworks. Analyses recovered a well-resolved phylogeny where the traditional species generally were monophyletic, with the exception of Cetrelia chicitae and Cetrelia pseudolivetorum. Species delimitation analyses supported the distinction of 15 groups within the studied Cetrelia taxa, dividing three traditionally identified species into some species candidates. Chemotypes, distinguished according to the major medullary substance, clearly correlated with clades recovered within Cetrelia, while samples with the same reproductive mode were dispersed throughout the phylogenetic tree. Consequently, delimiting Cetrelia species based only on reproductive morphology is not supported phylogenetically. Character analyses suggest that chemical characters have been more consistent compared to reproductive mode and indicate that metabolite evolution in Cetrelia towards more complex substances is probable.     

18S rDNA phylogeny of lamproderma and allied genera (Stemonitales, Myxomycetes, Amoebozoa)

The phylogenetic position of the slime-mould genus Lamproderma (Myxomycetes, Amoebozoa) challenges traditional taxonomy: although it displays the typical characters of the order Stemonitales, it appears to be sister to Physarales. This study provides a small subunit (18S or SSU) ribosomal RNA gene-based phylogeny of Lamproderma and its allies, with new sequences from 49 specimens in 12 genera. We found that the order Stemonitales and Lamproderma were both ancestral to Physarales and that Lamproderma constitutes several clades intermingled with species of Diacheopsis, Colloderma and Elaeomyxa. We suggest that these genera may have evolved from Lamproderma by multiple losses of fruiting body stalks and that many taxonomic revisions are needed. We found such high genetic diversity within three Lamproderma species that they probably consist of clusters of sibling species. We discuss the contrasts between genetic and morphological divergence and implications for the morphospecies concept, highlighting the phylogenetically most reliable morphological characters and pointing to others that have been overestimated. In addition, we showed that the first part (~600 bases) of the SSU rDNA gene is a valuable tool for phylogeny in Myxomycetes, since it displayed sufficient variability to distinguish closely related taxa and never failed to cluster together specimens considered of the same species.     

Hidden diversity and cryptic speciation refute cosmopolitan distribution in Caprella penantis (Crustacea: Amphipoda: Caprellidae)

Caprella penantis is considered a cosmopolitan species and one of the most challenging caprellids in taxonomic terms because of its remarkable intraspecific morphological variation. This study examined DNA sequences from mitochondrial (COI) and nuclear (18S) markers together with morphological data from 25 localities of C. penantis, and closely related species Caprella dilatata and Caprella andreae, all traditionally considered part of the old ‘acutifrons’ complex. The large genetic divergence and reciprocally allopatric distributions point to the existence of a species complex of at least four species, of which one is reported as a cryptic species. This study provides the first evidence of cryptic speciation in the family Caprellidae, and questions the validity of some traditional morphological characters used to delimit species in the genus Caprella. Our results are consistent with the idea that main factors were probably isolation by distance and ecological traits, promoting diversification in C. penantis. The strong genetic structure reported for this species in the Iberian Peninsula and Moroccan coasts also suggests restriction to dispersal as well as the presence of refugial areas. These results highlight the utility of the COI and 18S genes in combination with morphological characters for shedding light on systematic questions in caprellids, and patterns of genetic connectivity.     

Phylogeny and taxonomy of the round-eared sengis or elephant-shrews, genus Macroscelides (Mammalia, Afrotheria, Macroscelidea)

The round-eared sengis or elephant-shrews (genus Macroscelides) exhibit striking pelage variation throughout their ranges. Over ten taxonomic names have been proposed to describe this variation, but currently only two taxa are recognized (M. proboscideus proboscideus and M. p. flavicaudatus). Here, we review the taxonomic history of Macroscelides, and we use data on the geographic distribution, morphology, and mitochondrial DNA sequence to evaluate the current taxonomy. Our data support only two taxa that correspond to the currently recognized subspecies M. p. proboscideus and M. p. flavicaudatus. Mitochondrial haplotypes of these two taxa are reciprocally monophyletic with over 13% uncorrected sequence divergence between them. PCA analysis of 14 morphological characters (mostly cranial) grouped the two taxa into non-overlapping clusters, and body mass alone is a relatively reliable distinguishing character throughout much of Macroscelides range. Although fieldworkers were unable to find sympatric populations, the two taxa were found within 50 km of each other, and genetic analysis showed no evidence of gene flow. Based upon corroborating genetic data, morphological data, near sympatry with no evidence of gene flow, and differences in habitat use, we elevate these two forms to full species.     

Evolutionary mode, tempo, and phylogenetic association of continuous morphological traits in the aquatic moss genus Amblystegium

Evolutionary significance of morphological characters that have traditionally been used for species delineation in the aquatic moss genus Amblystegium was tested by partitioning the environmentally and genetically induced morphological variation and focusing on morphological evolution using comparative methods. Cultivation experiments under controlled condition showed that most of the morphological variation in nature resulted from plasticity. Information regarding genetically fixed morphological variation and genetic similarity derived from polymorphic inter-simple sequence repeat markers was combined into an explicit model of morphological evolution. Maximum likelihood estimates of the model parameters indicated that evolution of most characters tended to accelerate in the most recent taxa and was often independent from the phylogeny. Constraining the different characters to be independent from each other most often produced a less likely result than when the characters were free to evolve in a correlated fashion. Thus, the morphological characters that have traditionally been used to circumscribe different Amblystegium species lack the independence, diagnostic value for specific lineages, and stability that would be required for distinguishing different species.