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1.
Application of phylogenetic species recognition to morphologically recognized species in the genera Cystoseira Agardh and Halidrys Lyngbye on North American west coasts revealed little genetic variation despite a remarkable degree of morphological variation currently used to recognize and delineate species. Whereas morphological characteristics allow recognition of two genera, four morphological species and three informal forms, maximum genetic variation among them was similar to that characteristic of the intraspecific level in European congeners and other Fucales. Among morphological species and forms, nucleotide variation in a combined 26S (large subunit (LSU)) and internal transcribed spacer (ITS) ribosomal DNA analysis was below 3% while it was 1% or less for the RUBISCO spacer of the chloroplast DNA. Comparison of the LSU data to available data for European congeners showed that the genera Cystoseira and Halidrys are not monophyletic and that the previously recognized Cystoseiraceae should be included within the family Sargassaceae. These observations suggest that the current taxonomy for the Sargassaceae fails to reflect evolutionary history because Atlantic and Pacific Cystoseira and Halidrys appear to have arrived at similar morphologies independently. Our results indicate a comparatively recent establishment on the west coast of North America of a sargassacean progenitor whose descendant taxa have experienced limited genetic divergence and are characterized by a high capacity for phenotypic variation despite their overall genetic similarity. 相似文献
2.
Eleven strains of Epidermophyton floccosum were compared with 5 Microsporum and 5 Trichophyton species with respect to the restriction fragment length polymorphism (RFLP) of the mitochondrial DNA to reveal their phylogenetic relationships. The phylogeny of 11 species showed that the three dermatophyte genera could not be separated from each other and could be considered to be congeneric. This result is not inconsistent with the results from ribosomal RNA sequences. 相似文献
3.
Plantaginaceae tribe Antirrhineae as revised by Sutton (1988) comprises about 30 genera that have undergone significant taxonomic changes in recent years, many of which have yet to be assessed by detailed phylogenetic analyses, including Kickxia, Nanorrhinum and Chaenorhinum. To examine the monophyly, relationships and rank of Kickxia, Nanorrhinum and Chaenorhinum, we conducted a phylogenetic analyses of the nuclear ribosomal DNA internal transcribed spacer region (ITS) and chloroplast DNA ( rpl32‐trnL) sequence data, with special focus on the Flora Iranica region. We sampled 22 species of Kickxia s.l. (16 of Kickxia s.s. and 6 of Nanorrhinum), 2 species of Anarrhinum, 12 species of Chaenorhinum, 19 representatives of nine additional genera of Antirrhineae, and several outgroup taxa representing other genera of Plantaginaceae. Parsimony and Bayesian analyses of the two datasets produced almost congruent trees, although taxon sampling differed. Our results indicate that Chaenorhinum can be subdivided into two highly supported groups of species, partially matching two of the currently recognized sections of the genus. Albraunia and Holzneria are nested within the Chaenorhinum clade and should not be recognized as distinct genera. Two clades corresponding to Kickxia sect. Kickxia and Kickxia sect. Valvatae were also highly supported. Our data, whn combined with all other available evidence, support recognition of the clade comprising Kickxia sect. Valvatae at the genus level, as Nanorrhinum. Based on this result, six names are here transferred to Nanorrhinum. A diagnostic key to the seven genera of tribe Antirrhineae known from the Flora Iranica region is also provided. 相似文献
4.
The taxonomic positions of the marine genera Alteromonas, Pseudoalteromonas, Idiomarina, and Colwellia within the gamma subclass of the class Proteobacteria were specified on the basis of their phenotypic, genotypic, and phylogenetic characteristics. Gram-negative aerobic bacteria of the genera Alteromonas, Pseudoalteromonas, and Idiomarina and facultatively anaerobic bacteria of the genus Colwellia were found to form a phylogenetic cluster with a 16S rRNA sequence homology of 90% or higher. The characteristics of these genera presented in this paper allow their reliable taxonomic identification. Based on the analysis of our experimental data and analyses available in the literature, we propose to combine the genera Alteromonas, Pseudoalteromonas, Idiomarina, and Colwellia into a new family, Alteromonadaceae fam. nov., with the type genus Alteromonas. 相似文献
5.
The internal transcribed spacer (ITS) region of the 18 S–25 S nuclear ribosomal DNA repeat was sequenced from 19 populations of the tribe Lactuceae, including all species of dwarf dandelion ( Krigia) and five outgroup genera. The incidence of length changes and base substitutions was at least two times higher for ITS 1 than ITS 2. Interspecific sequence divergence within Krigia averaged 9.62% (1.61%–15.19%) and 4.26% (0%–6.64%) in ITS 1 and ITS 2, respectively. Intergeneric sequence divergence ranged from 15.6% to 44.5% in ITS 1 and from 8.0% to 28.6% in ITS 2. High sequence divergence and homoplasy among genera of tribe Lactuceae suggest that the phylogenetic utility of ITS sequence data is limited to interspecific studies or comparisons among closely related genera. Trees generated from ITS sequences are essentially identical to those from restriction site comparisons of the entire nuclear ribosomal (nr) DNA region. The degree of tree resolution differed depending on how gaps were treated in phylogenetic analyses. The ITS trees were congruent with the chloroplast DNA and morphological phylogenies in three major ways: 1) the sister group relationship between Krigia and Pyrrhopappus; 2) the recognition of two monophyletic sections, Krigia and Cymbia, in genus Krigia; and 3) the monophyly of the K. occidentalis-K. cespitosa clade in sect. Cymbia. However, the two nrDNA-based trees are not congruent with morphology/chloroplast DNA-based trees for the interspecific relationships in sect. Krigia. An average of 22.5% incongruence was observed among four Krigia data sets. The relatively high degree of incongruence among data sets is due primarily to conflict between trees based on nrDNA and morphological/cpDNA data. The incongruence is probably due to the concerted evolution of nrDNA repeating units. The results from Krigia and the Lactuceae suggest that nrDNA data may have limited utility in phylogenetic studies of plants, especially in groups which exhibit high levels of sequence divergence. Our combined phylogenetic analysis as a total evidence shows the least conflict to each of the individual data sets. 相似文献
6.
The gross brain morphology, brain proportions, and position of cranial nerves in all four genera ( Potamotrygon, Plesiotrygon, Paratrygon, and Heliotrygon) and 11 of the species of the Neotropical stingray family Potamotrygonidae were studied to provide new characters that may have a bearing on internal potamotrygonid systematics. The brain was also studied in four other stingray (Myliobatiformes) genera ( Hexatrygon, Taeniura, Dasyatis, and Gymnura) to provide a more inclusive phylogenetic context for the interpretation of features of the brain in potamotrygonids. Our results indicate, based on neuroanatomical characters, that the genera Paratrygon and Heliotrygon are sister groups, as are the genera Potamotrygon and Plesiotrygon, agreeing with previous morphological and molecular phylogenetic studies. Both groups of genera share distinct conditions of the olfactory tracts, telencephalon and its central nuclei, hypophysis and infundibulum, morphology and orientation of the metencephalic corpus cerebelli, orientation of the glossopharyngeal nerve, and overall encephalic proportions. The corpus cerebelli of Paratrygon and Heliotrygon is interpreted as being more similar to the general batoid condition and, given their phylogenetic position highly nested within stingrays, is considered secondarily derived, not plesiomorphically retained. Our observations of the corpus cerebelli of stingrays, including Hexatrygon, corroborate that the general stingray pattern previously advanced by Northcutt is derived among batoids. The morphology of the brain is shown to be a useful source of phylogenetically informative characters at lower hierarchical levels, such as between genera and species, and thus, has significant potential in phylogenetic studies of elasmobranchs. J. Morphol. 277:252–263, 2016. © 2015 Wiley Periodicals, Inc. 相似文献
7.
Threadfin breams and relatives of the family Nemipteridae comprise 69 currently recognized species in five genera. They are found in the tropical and subtropical Indo‐West Pacific and most are commercially important. Using recently developed molecule‐based approaches exploiting DNA sequence variation among species/specimens, this study reconstructed a comprehensive phylogeny of the Nemipteridae, examined the validity of species and explored the cryptic diversity of the family, and tested previous phylogenetic hypotheses. A combined data set (105 taxa from 41 morphospecies) with newly determined sequences from two nuclear genes ( RAG1 and RH) and one mitochondrial gene ( COI), and a data set with only COI gene sequences (329 newly obtained plus 328 from public databases from a total of 53 morphospecies) were used in the phylogenetic analysis. The latter was further used for species delimitation analyses with two different tools to explore species diversity. Our phylogenetic results showed that all the currently recognized genera were monophyletic. The monotypic genus Scaevius is the sister group of Pentapodus and they together are sister to Nemipterus. These three genera combined to form the sister group of the clade comprising Parascolopsis and Scolopsis. The validity of most of the examined species was confirmed except in some cases. The combined evidence from the results of different analyses revealed a gap in our existing knowledge of species diversity in the Nemipteridae. We found several currently recognized species contain multiple separately evolving metapopulation lineages within species; some lineages should be considered as new species for further assignment. Finally, some problematic sequences deposited in public databases (probably due to misidentification) were also revised in this study to improve the accuracy for prospective DNA barcoding work on nemipterid fishes. 相似文献
8.
The Proterodiplostomidae Dubois, 1936 is a relatively small family of diplostomoidean digeneans parasitising the intestines of reptilian hosts associated with freshwater environments in tropical and subtropical regions. The greatest diversity of proterodiplostomids is found in crocodilians, although some parasitise snakes and turtles. According to the most recent revision, the Proterodiplostomidae included 17 genera within 5 subfamilies. Despite the complex taxonomic structure of the family, availability of testable morphology-based phylogenetic hypotheses and ancient hosts, molecular phylogenetic analyses of the group were practically lacking. Herein, we use novel DNA sequence data of the nuclear lsrRNA gene and mitochondrial cox1 gene from a broad range of proterodiplostomid taxa obtained from crocodilian, fish, and snake hosts on four continents to test the monophyly of the family and evaluate the present morphology-based classification system of the Proterodiplostomidae in comparison with the molecular phylogeny. This first detailed phylogeny for the Proterodiplostomidae challenges the current systematic framework. Combination of molecular phylogenetic data with examination of freshly collected quality specimens and re-evaluation of morphological criteria resulted in a number of systematic and nomenclatural changes along with a new phylogeny-based classification of the Proterodiplostomidae. As the result of our molecular and morphological analyses: (i) the current subfamily structure of the Proterodiplostomidae is abolished; (ii) three new genera, Paraproterodiplostomum n. g., Neocrocodilicola n. g. and Proteroduboisia n. g., are described and Pseudoneodiplostomoides Yamaguti, 1954 is restored and elevated from subgenus to genus level; (iii) two new species, Paraproterodiplostomum currani n. g., n. sp. and Archaeodiplostomum overstreeti n. sp., are described from the American alligator in Mississippi, USA. Comparison of the structure of terminal ducts of the reproductive system in all proterodiplostomid genera did not support the use of these structures for differentiation among subfamilies (or major clades) within the family, although they proved to be useful for distinguishing among genera and species. Our study includes the first report of proterodiplostomids from Australia and the first evidence of a snake acting as a paratenic host for a proterodiplostomid. A key to proterodiplostomid genera is provided. Questions of proterodiplostomid-host associations parasitic in crocodilians are discussed in connection with their historical biogeography. Our molecular phylogeny of the Proterodiplostomidae closely matches the current molecular phylogeny of crocodilians. Directions for future studies of the Proterodiplostomidae are outlined. 相似文献
9.
The flora of Western Europe is rich in endemic species of Apiaceae, many of which have been poorly investigated and whose phylogenetic relationships are poorly known. To investigate relationships among three endemic European genera ( Dethawia, Meum, and Rivasmartinezia gen. nov.) and to ascertain their higher-level phylogenetic placements within the subfamily Apioideae, we examined nuclear ribosomal DNA ITS sequences and the plastid trnL-trnF region. Phylogenies estimated using parsimony and Bayesian inference reveal that (1) the historically known “ Conioselinum chinense” Clade ( Conioselinum chinense; C. scopulorum; Ligusticum canadense; L. porteri; Meum athamanticum; Mutellina purpurea; and Trochiscanthes nodiflora) comprise a strongly supported monophyletic group (100% BS); (2) the genera Dethawia and Meum comprise a strongly supported monophyletic group also included in the “ Conioselinum chinense” Clade; and finally (3) a new genus ( Rivasmartinezia) with one species ( R. vazquezii) from the Northwestern of the Iberian Peninsula, and placed in the basal position in the “ Conioselinum chinense” Clade, is described for the family Apiaceae subfamily Apioideae. 相似文献
10.
Three orchid genera, Paphiopedilum, Cymbidium, and Dendrobium, are among the most heavily traded ornamental plants in Thailand. In this study, 27 isolates of Rhizoctonia-like fungi were isolated from root sections of mature orchids in the three orchid genera, collected from diverse horticultural
settings in Chiang Mai and Chiang Rai provinces of Thailand. Fungal identification was done by the morphological characterization,
the comparison of the internal transcribed spacer and 5.8S ribosomal DNA sequences, and the phylogenetic analysis. Epulorhiza repens was found to be the most common species found in the roots of various species of all three orchid genera, whereas Epulorhiza calendulina-like isolates were strictly found in the roots of Paphiopedilum species. We have also isolated and described an anamorph of Tulasnella irregularis, four new anamorphic species in the genus Tulasnella, and a new anamorphic species in the family Tulasnellaceae. Our study provides information on diversity of root-associated
fungi of the orchid genera and at the sampling sites that were rarely addressed in the previous studies. 相似文献
11.
Aim Our aim was to investigate the historical biogeography of the three genera of the Leucocroton alliance (i.e. Garciadelia Jestrow & Jiménez Rodr., Lasiocroton Griseb., and Leucocroton Griseb., Euphorbiaceae). Location The alliance is restricted to the Bahamas, Cuba, Hispaniola and Jamaica. Methods Members of the Leucocroton alliance, along with representatives from tribe Adelieae ( Adelia L. and Philyra Klotzsch.), were included in a molecular phylogenetic analysis based upon nucleotide sequences of the internal transcribed spacer region of the nuclear ribosomal DNA and the non‐coding chloroplast regions psbM– trnD and ycf6 –pcbM. The program s‐diva was used to calculate ancestral areas based on the phylogenetic trees and present species distributions. Results Phylogenetic analyses support the monophyly of the three genera. The ancestral area of the Leucocroton alliance is eastern Cuba and Hispaniola. Ancestral forms of Leucocroton arose on eastern Cuba and underwent two migrations across the island. The ancestor of Lasiocroton also originated on eastern Cuba followed by later dispersal to and speciation events on the other islands. Our study also suggests that ancestral forms of the Leucocroton alliance probably occurred on limestone soils. Main conclusions Our study concurs with previous hypotheses suggesting that the flora of serpentinite regions of the Caribbean derives from other types of soils. The serpentine endemics of the Leucocroton alliance have a single origin and represent one of the most extraordinary examples of speciation in this unique environment of the New World. The high colonization success achieved by the members of Leucocroton on serpentine soils was not attained by the other genera of the alliance, which occur on limestone areas. 相似文献
12.
The Larreoideae subfamily is the major representative of the family Zygophyllaceae in South America, where several of its members are common to dominant in arid regions of the Southern Cone. However, there are currently no phylogenetic analyses of the subfamily that may help to understand its origin and diversification. Additionally, there are taxonomic discrepancies around Bulnesia Gay (1845), one of its more important genera. Accordingly, we performed a phylogenetic analysis combining chloroplast ( rbcL and trnL-F) and nuclear (ITS) DNA sequences. Bayesian and Parsimony analyses were performed to highlight the intergeneric relationships within Larreoideae. All genera with the exception of Bulnesia are monophyletic and we propose to redefine Bulnesia, dividing it in two genera. Furthermore, other taxonomic issues of the remaining genera are solved. This study represents the first approximation to clarify the phylogenetic relationships amongst all Larreoideae genera, producing a phylogenetic framework that can be used in future macro-ecological studies. 相似文献
13.
We conducted phylogenetic analyses using two DNA sequence data sets derived from matK, the maturase-coding gene located in an intron of the plastid gene trnK, and the internal transcribed spacer region of 18S–26S nuclear ribosomal DNA to examine relationships in subtribe Aeridinae (Orchidaceae). Specifically, we investigated (1) phylogenetic relationships among genera in the subtribe, (2) the congruence between previous classifications of the subtribe and the phylogenetic relationships inferred from the molecular data, and (3) evolutionary trends of taxonomically important characters of the subtribe, such as pollinia, a spurred lip, and a column foot. In all, 75 species representing 62 genera in subtribe Aeridinae were examined. Our analyses provided the following insights: (1) monophyly of subtribe Aeridinae was tentatively supported in which 14 subclades reflecting phylogenetic relationships can be recognized, (2) results are inconsistent with previous classifications of the subtribe, and (3) repeated evolution of previously emphasized characters such as pollinia number and apertures, length of spur, and column foot was confirmed. It was found that the inconsistencies are mainly caused by homoplasy of these characters. At the genus level, Phalaenopsis, Cleisostoma, and Sarcochilus are shown to be non-monophyletic. 相似文献
14.
We inferred secondary structure models of the internal transcribed spacers (ITS) 1 and 2 of bush crickets using a combined comparative and thermodynamic approach. The inferred secondary structure models were used to account for interdependency of interacting nucleotides in a phylogenetic analysis of the bush cricket genus Poecilimon. Our analysis indicates that the two previously reported conformational structures (i.e., hairpin and ring) of ITS2 are likely to fold in bush crickets as well and that both predicted structures are similar to those proposed for other eukaryotes. Comparing predicted ITS1 secondary structure models proved to be difficult because of substantial variation in their nucleotide sequence length. Our study revealed that the phylogenetic signal of ITS1 and ITS2 is largely congruent with that preserved in the mitochondrial genes 16S rRNA, tRNA‐Val and 12S rRNA. The phylogenetic signal in both the nuclear and the mitochondrial genome question the monophyly of the genus Poecilimon: species of the genera Poecilimonella, Parapoecilimon, Polysarcus and Phonochorion consistently cluster within Poecilimon. 相似文献
15.
Identification of rodents is very difficult mainly due to high similarities in morphology and controversial taxonomy. In this study, mitochondrial cytochrome oxidase subunit I (COI) was used as DNA barcode to identify the Murinae and Arvicolinae species distributed in China and to facilitate the systematics studies of Rodentia. In total, 242 sequences (31 species, 11 genera) from Murinae and 130 sequences (23 species, 6 genera) from Arvicolinae were investigated, of which 90 individuals were novel. Genetic distance, threshold method, tree‐based method, online BLAST and BLOG were employed to analyse the data sets. There was no obvious barcode gap. The average K2P distance within species and genera was 2.10% and 12.61% in Murinae, and 2.86% and 11.80% in Arvicolinae, respectively. The optimal threshold was 5.62% for Murinae and 3.34% for Arvicolinae. All phylogenetic trees exhibited similar topology and could distinguish 90.32% of surveyed species in Murinae and 82.60% in Arvicolinae with high support values. BLAST analyses yielded similar results with identification success rates of 92.15% and 93.85% for Murinae and Arvicolinae, respectively. BLOG successfully authenticated 100% of detected species except Leopoldamys edwardsi based on the latest taxonomic revision. Our results support the species status of recently recognized Micromys erythrotis, Eothenomys tarquinius and E. hintoni and confirm the important roles of comprehensive taxonomy and accurate morphological identification in DNA barcoding studies. We believe that, when proper analytic methods are applied or combined, DNA barcoding could serve as an accurate and effective species identification approach for Murinae and Arvicolinae based on a proper taxonomic framework. 相似文献
16.
We used sequences from both internal transcribed spacers (ITS) and a small portion of the 5.8S gene of nuclear ribosomal DNA (nrDNA) for phylogenetic reconstruction of 19 genera of Maloideae and four potential outgroups from the Rosaceae. Parsimony analyses indicate that Maloideae are not monophyletic; Vauquelinia, which is traditionally placed in Spiraeoideae, and two genera of the Maloideae, Eriobotrya and Rhaphiolepis, form a well-supported clade that is the sister to the remainder of the subfamily. Although our ITS phylogenetic hypothesis is highly resolved, there is considerable homoplasy, and support, as indicated by bootstrap values and decay indices, is relatively weak for all groups except four: Eriobotrya-Rhaphiolepis-Vauquelinia, Crataegus-Mespilus, Amelanchier-Peraphyllum-Malacomeles, and Cydonia-Pseudocydonia. Our DNA sequence data do not support a broad interpretation of Sorbus. Intergeneric hybridization, which is prevalent in Maloideae, occurs between genera that are far removed from one another on our most-parsimonious trees. We infer an overall phylogeny from separate analyses of ITS DNA sequences and recently published morphological and wood anatomical studies of Maloideae and from analyses after pooling these data sets. The four most strongly supported clades of the ITS phylogeny appear in the phylogeny based on pooled data. 相似文献
17.
Gracilariaceae are mostly pantropical red algae and include ~230 species in seven genera. Infrafamilial classification of the group has long been based on reproductive characters, but previous phylogenies have shown that traditionally circumscribed groups are not monophyletic. We performed phylogenetic analyses using two plastid (universal plastid amplicon and rbcL) and one mitochondrial ( cox1) loci from a greatly expanded number of taxa to better assess generic relationships and understand patterns of character distributions. Our analyses produce the most well‐supported phylogeny of the family to date, and indicate that key characteristics of spermatangia and cystocarp type do not delineate genera as commonly suggested. Our results further indicate that Hydropuntia is not monophyletic. Given their morphological overlap with closely related members of Gracilaria, we propose that Hydropuntia be synonymized with the former. Our results additionally expand the known ranges of several Gracilariaceae species to include Brazil. Lastly, we demonstrate that the recently described Gracilaria yoneshigueana should be synonymized as G. domingensis based on morphological and molecular characters. These results demonstrate the utility of DNA barcoding for understanding poorly known and fragmentary materials of cryptic red algae. 相似文献
18.
The interrelationships within ant subfamilies remain elusive, despite the recent establishment of the phylogeny of the major ant lineages. The tribe Myrmicini belongs to the subfamily Myrmicinae, and groups morphologically unspecialized genera. Previous research has struggled with defining Myrmicini, leading to considerable taxonomic instability. Earlier molecular phylogenetic studies have suggested the nonmonophyly of Myrmicini, but were based on limited taxon sampling. We investigated the composition of Myrmicini with phylogenetic analyses of an enlarged set of taxa, using DNA sequences of eight gene fragments taken from 37 representatives of six of the seven genera ( Eutetramorium, Huberia, Hylomyrma, Manica, Myrmica, and Pogonomyrmex), and eight outgroups. Our results demonstrate the invalidity of Myrmicini as currently defined. We recovered sister‐group relationships between the genera Myrmica and Manica, and between Pogonomyrmex and Hylomyrma. This study illustrates that to understand the phylogeny of over 6000 myrmicine species, comprehensive taxon sampling and DNA sequencing are an absolute requisite. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 482–495. 相似文献
19.
We conducted the first ever survey of xeniid octocorals in the Indonesian Archipelago, centre of the highly biodiverse Coral Triangle region of the Indo-Pacific. Among 48 xeniid specimens collected from Lembeh Strait, North Sulawesi, we identified 26 morphospecies belonging to six genera based on assessment of the morphological characters traditionally used for xeniid taxonomy. Multilocus DNA barcodes obtained from 23 morphospecies clustered into 21 molecular operational taxonomic units (MOTUs) separated by average genetic distance values >0.3%. The overall concordance between morphospecies and MOTUs was 91%; just one pair and one trio of morphospecies were not distinguished by the DNA barcodes. A molecular phylogenetic reconstruction of family Xeniidae based on four loci ( COI, mtMutS, ND2, 28S rDNA) supported the distinction of Anthelia and Cespitularia+Efflatounaria from all other xeniid genera. Although the remaining genera for which molecular data were available ( Asterospicularia, Heteroxenia, Ovabunda, Sansibia, Sarcothelia, Sympodium, Xenia) belonged to a single, well-supported clade, the phylogenetic relationships among them were poorly resolved. Species of Xenia were distributed among three different sub-clades within which they were paraphyletic with Ovabunda (clade X1), Heteroxenia (clade X2) and Sansibia plus Sarcothelia (clade X3). No morphological characters have yet been identified that differentiate these three phylogenetically distinct clades of Xenia. Use of molecular barcodes to discriminate species will facilitate future ecological studies of Xeniidae, a group that has been shown to opportunistically monopolize disturbed reef habitat. 相似文献
20.
Tandemly repeated sequences are a common feature of vertebrate mitochondrial DNA control regions. However, questions still
remain about their mode of evolution, function, and phylogenetic distribution. We report phylogenetic and geographic patterns
of variation of control region repeat sequence and number in a nonparasitic lamprey, Lampetra aepyptera. A survey of populations from throughout the species’ range revealed remarkably low repeat sequence polymorphism but some
interpopulation variation in repeat number. The high sequence similarity extended to repeats observed in other species in
the genus Lampetra and other lamprey genera. The very low levels of variation suggest a high copy turnover. Our data are consistent with the
illegitimate elongation model of repeat gain and loss and further suggest that repeat change occurs at internal copies. However,
the limited variation across some species of lamprey suggests that functional constraints may further limit variation. 相似文献
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