共查询到4条相似文献,搜索用时 0 毫秒
1.
Alexandrium catenella (Whedon et Kof.) Balech, A. tamarense (M. Lebour) Balech, and A. fundyense Balech comprise the A. tamarense complex, dinoflagellates responsible for paralytic shellfish poisoning worldwide. The relationships among these morphologically defined species are poorly understood, as are the reasons for increases in range and bloom occurrence observed over several decades. This study combines existing data with new ribosomal DNA sequences from strains originating from the six temperate continents to reconstruct the biogeography of the complex and explore the origins of new populations. The morphospecies are examined under the criteria of phylogenetic, biological, and morphological species concepts and do not to satisfy the requirements of any definition. It is recommended that use of the morphospecies appellations within this complex be discontinued as they imply erroneous relationships among morphological variants. Instead, five groups (probably cryptic species) are identified within the complex that are supported on the basis of large genetic distances, 100% bootstrap values, toxicity, and mating compatibility. Every isolate of three of the groups that has been tested is nontoxic, whereas every isolate of the remaining two groups is toxic. These phylogenetic groups were previously identified within the A. tamarense complex and given geographic designations that reflected the origins of known isolates. For at least two groups, the geographically based names are not indicative of the range occupied by members of each group. Therefore, we recommend a simple group‐numbering scheme for use until the taxonomy of this group is reevaluated and new species are proposed. 相似文献
2.
Utility of Amplified Fragment Length Polymorphisms (AFLP) to analyse genetic structures within the Alexandrium tamarense species complex 总被引:3,自引:0,他引:3
Phylogenetic analyses of the Alexandrium tamarense species complex using ribosomal RNA sequences show a differentiation of ribotypes/clades into geographic areas and not into the three morphotypes/species A. tamarense, A. fundyense and A. catenella. Different parts of the rRNA operon have proven informative in revealing the existence and the relationships of these geographic clades, whereas even internal transcribed spacer (ITS) regions lack the resolution required to gain a deeper insight into the population structure of the species complex. Here, the utility of the DNA fingerprinting technique Amplified Fragment Length Polymorphism (AFLP) as a possible tool for such purposes was tested. A mixed sampling strategy was used in order to assess the amount of variation of AFLP banding patterns at the level of populations and geographic clades. We also describe optimized methods to achieve a good reproducibility. Our results suggest that AFLPs can provide useful information at the population level using clonal samples from a certain bloom, whereas the amount of variation that we found is too high to allow for meaningful comparisons of a few strains collected from different localities at different time points even though they belong to one geographic clade. 相似文献
3.
Seven new species of the genus Haploniscus from the deep Scotia and Weddell Seas are presented, combining morphological and molecular data (mitochondrial 16S rDNA and nuclear 18S rDNA). Haploniscus cassilatus sp. nov. , H. cucullus sp. nov. , H. weddellensis sp. nov. , H. procerus sp. nov. and H. kyrbasia sp. nov. are characterized by a prominent rostral process, the size and shape of which vary among species. The rostrum of H. microkorys sp. nov. is distinctly smaller than that of the former species, while H. nudifrons sp. nov. does not possess a rostrum. The status of the latter as separate species is obvious, owing to the stronger morphological differences. DNA was sequenced from three of the other five species. Genetic distances together with the more subtle morphological variation justify the erection of separate species. Overall morphological variations between these species are small yet noticeable and include, among others, the rostrum, the shape of the pleotelson and setation of pereopods. Our molecular data sets reveal detailed phylogenetic insights within the Haploniscus cucullus complex, supporting the monophyly of all species. We found p -distances of at least 0.0732 (16S rDNA) and 0.0140 (complete 18S rDNA) between pairs of species and show that both genes can be used as a marker for DNA taxonomy. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society , 2008, 152 , 655–706. 相似文献
4.