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1.
 Intrageneric phylogeny among ten representative Ceanothus species was investigated using DNA sequences of the chloroplast encoded ndhF and rbcL genes. Parsimony analysis of the ndhF sequences identified two main clades corresponding to two subgenera Ceanothus and Cerastes. The phylogenetic results suggest that three monophyletic clades within the subgenus Ceanothus can be delimited on the basis of (1) evergreen or (2) deciduous leaves and (3) thorn presence within the evergreen clade. The estimated divergence time based on rbcL sequences suggests that the two subgenera diverged 18–39 million years ago whereas species within each subgenus diverged more recently. Taken together, the results support the division of Ceanothus into two monophyletic subgenera and are consistent with the postulated recent divergence of many species within each subgenus. Received: 25 September 1996/Accepted: 8 November 1996  相似文献   

2.
The mitochondrial DNA (mtDNA) phylogeny of Japanese Pandaka species (Perciformes: Gobiidae) was inferred from partial nucleotide sequences of the mitochondrial 12S and 16S rRNA genes (1083bp). The resultant mtDNA tree showed two major clades (clade I and clade II), which were inconsistent with the present taxonomic classification. One of the major clades was further divided into two geographical groups, distributed on the Japanese Major Islands (clade I-A) and from Amami-oshima Island to Iriomote Island (clade I-B). The mtDNA haplotypes in clade II were found only on Iriomote Island. The mtDNA divergences in clade I indicated that the Japanese Major Island (clade I-A) and Ryukyu (clade I-B) groups have been geographically isolated from each other for millions of years, based on the putative molecular divergence rate. The geographical distributions of mtDNA haplotypes in clade I-A and clade I-B also suggested that Pandaka gobies had not dispersed to distant offshore islands, indicating that their geographical differentiation may be closely associated with the geological history of the Japanese and Ryukyu Archipelagos.This revised version was published online in January 2005 with corrections to the repetition of the 1st authors name.  相似文献   

3.
Bumble bees ( Bombus Latreille) occupy a wide diversity of habitats, from alpine meadows to lowland tropical forest, yet they appear to be similar in morphology throughout their range, suggesting that behavioural adaptations play a more important role in colonizing diverse habitats. Notwithstanding their structural homogeneity, bumble bees exhibit striking inter- and intraspecific variation in colour pattern, purportedly the outcome of mimetic evolution. A robust phylogeny of Bombus would provide the framework for elucidating the history of their wide biogeographical distribution and the evolution of behavioural and morphological adaptations, including colour pattern. However, morphological studies of bumble bees have discovered too few phylogenetically informative characters to reconstruct a robust phylogeny. Using DNA sequence data, we report the first nearly complete species phylogeny of bumble bees, including most of the 250 known species from the 38 currently recognized subgenera. Bayesian analysis of nuclear (opsin, EF-1α, arginine kinase, PEPCK) and mitochondrial (16S) sequences results in a highly resolved and strongly supported phylogeny from base to tips, with clear-cut support for monophyly of most of the conventional morphology-based subgenera. Most subgenera fall into two distinct clades ( short-faced and long-faced ) associated broadly with differences in head morphology. Within the short-faced clade is a diverse New World clade, which includes nearly one-quarter of the currently recognized subgenera, many of which are restricted to higher elevations of Central and South America. The comprehensive phylogeny provides a firm foundation for reclassification and for evaluating character evolution in the bumble bees.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 161–188.  相似文献   

4.
Investigations of opsin evolution outside of vertebrate systems have long been focused on insect visual pigments, whereas other groups have received little attention. Furthermore, few studies have explicitly investigated the selective influences across all the currently characterized arthropod opsins. In this study, we contribute to the knowledge of crustacean opsins by sequencing 1 opsin gene each from 6 previously uncharacterized crustacean species (Euphausia superba, Homarus gammarus, Archaeomysis grebnitzkii, Holmesimysis costata, Mysis diluviana, and Neomysis americana). Visual pigment spectral absorbances were measured using microspectrophotometry for species not previously characterized (A. grebnitzkii=496 nm, H. costata=512 nm, M. diluviana=501 nm, and N. americana=520 nm). These novel crustacean opsin sequences were included in a phylogenetic analysis with previously characterized arthropod opsin sequences to determine the evolutionary placement relative to the well-established insect spectral clades (long-/middle-/short-wavelength sensitive). Phylogenetic analyses indicate these novel crustacean opsins form a monophyletic clade with previously characterized crayfish opsin sequences and form a sister group to insect middle-/long-wavelength-sensitive opsins. The reconstructed opsin phylogeny and the corresponding spectral data for each sequence were used to investigate selective influences within arthropod, and mainly "pancrustacean," opsin evolution using standard dN/dS ratio methods and more sensitive techniques investigating the amino acid property changes resulting from nonsynonymous replacements in a historical (i.e., phylogenetic) context. Although the conservative dN/dS methods did not detect any selection, 4 amino acid properties (coil tendencies, compressibility, power to be at the middle of an alpha-helix, and refractive index) were found to be influenced by destabilizing positive selection. Ten amino acid sites relating to these properties were found to face the binding pocket, within 4 A of the chromophore and thus have the potential to affect spectral tuning.  相似文献   

5.
Symbiotic dinoflagellates belonging to the genus Symbiodinium (Freudenthal) are found worldwide in association with shallow‐water tropical and subtropical marine invertebrates. Most phylogenetic studies of Symbiodinium have used nuclear rRNA (nrDNA) genes to infer relationships among members of the genus. In this report, we present the first phylogeny of Symbiodinium based on DNA sequences from a mitochondrial protein‐coding gene (cytochrome oxidase subunit I [cox1]). Two principal groups, one comprised of Symbiodinium clade A and the second encompassing Symbiodinium clades B/C/D/E/F, are strongly supported in the cox1 phylogeny. Relationships within Symbiodinium clades B/C/D/E/F, however, are less well resolved compared with phylogenies inferred from nrDNA and chloroplast large subunit (cp23S)‐rDNA genes. Statistical tests between alternative tree topologies verified, with an exception being the position of one controversial member of Symbiodinium clade D, that relationships inferred from cox1 are congruent with those inferred from nrDNA and cp23S‐rDNA. Taken together, the relationships between the major Symbiodinium clades are robust, and there appears to be no evidence of hybridization or differential introgression of nuclear and plastid genomes between clades.  相似文献   

6.
The genus Gephyromantis is a clade within the Malagasy-Comoroan family Mantellidae composed of rainforest frogs that live and breed to varying degrees independently from water. Based on DNA sequences of five mitochondrial and five nuclear genes we inferred the phylogeny of these frogs with full taxon coverage at the species level. Our preferred consensus tree from a partitioned Bayesian analysis of 5843 base pairs of 51 nominal and candidate species supports various major clades within the genus although the basal relationships among these remain unresolved. The data provide strong evidence for the monophyly of the subgenera Gephyromantis (after exclusion of Gephyromantis klemmeri), Laurentomantis, Vatomantis, and Phylacomantis. Species assigned to the subgenus Duboimantis belong to two strongly supported clades of uncertain relationships. G. klemmeri, previously in the subgenus Gephyromantis, was placed with high support sister to the Laurentomantis clade, and the Laurentomantis + G. klemmeri clade was sister to Vatomantis. A reconstruction of ancestral distribution areas indicates a diversification of several subgenera in the northern biogeographic regions of Madagascar and the dispersal out of northern Madagascar for several clades.  相似文献   

7.
Peintner U  Moncalvo JM  Vilgalys R 《Mycologia》2004,96(5):1042-1058
Research on the molecular systematics of Cortinarius, a species-rich mushroom genus with nearly global distribution, is just beginning. The present study explores infrageneric relationships using rDNA ITS and LSU sequence data. One large dataset of 132 rDNA ITS sequences and one combined da-taset with 54 rDNA ITS and LSU sequences were generated. Hebeloma was used as outgroup. Bayesian analyses and maximum-likelihood (ML) analyses were carried out. Bayesian phylogenetic inference performed equally well or better than ML, especially in large datasets. The phylogenetic analysis of the combined dataset with species representing all currently recognized subgenera recovered seven well-supported clades (Bayesian posterior probabilities BPP > 90%). These major clades are: /Myxacium s.l., /subg. Cortinarius, the /phlegmacioid clade (including the subclades /Phlegmacium and /Delibuti), the /calochroid clade (/Calochroi, /Ochroleuci and /Allutus), the /telamonioid clade (/Telamonia, /Orellani, /Anomali), /Dermocybe s.l. and /Myxotelamonia. Our results show that Cortinarius consists of many lineages, but the relationships among these clades could not be elucidated. On one hand, the low divergence in rDNA sequences can be held responsible for this; on the other hand, taxon sampling is problematic in Cortinarius phylogeny. Because of the incredibly high diversity (~2000 Cortinarius species), our sampling included <5% of the known species. By choosing type species of subgenera and sections, our sampling is strongly biased toward Northern Hemisphere taxa. More extensive taxon sampling, especially of species from the Southern Hemisphere, is essential to resolve the phylogeny of this important genus of ectomycorrhizal fungi.  相似文献   

8.
The genus Fritillaria embraces up to 165 taxa in the family Liliaceae, most of which are of high medicinal and ornamental value and importance. In this study, 44 specimens of the genus representing 9 species were collected from their natural habitats located in 10 provinces of Iran. Phylogenetic analysis was performed based on DNA sequences of the internal transcribed spacer (ITS) of the nuclear ribosomal cistron and the trnL-trnF regions. The phylogeny was constructed using the neighbor joining inference method. Results indicate that the examined samples were evidently diverged into 2 distinct clades. Members of the subgenera Fritillaria and Rhinopetalum formed one clade while the other clade contained the subgenera Theresia and Petilium. There can be seen a high degree of similarity between the only yellow-colored crown imperial specimen and the red-colored specimens. The endemic species of Fritillaria straussii, Fritillaria zagrica and Fritillaria kotschyana which their status within the subgenera known in the genus Fritillaria has been remained undefined, fell into the subgenus Fritillaria. The clades also had relatively reasonable distribution patterns based on the genetic structure, geographical conditions and climate specifications. This study revealed the feasibility of the ITS and trnL-trnF DNA sequence for phylogeny of the genus Fritillaria. This is the first phylogenetic analysis of Fritillaria spp. in Iran.  相似文献   

9.
Bovine genes encoding T-cell receptor, CD3, and CD8 molecules have been mapped to syntetic groups using bovine × rodent hybrid somatic cells. T-cell receptor and chains were assigned to bovine syntenic group U5, and the and genes were syntenic with each other and with markers on U13. CD3E and CD3D genes were syntenic with each other and located to bovine syntenic group U19. CD8 was most concordant with markers of syntenic group U16, although the concordancy was only 85% and the assignment must be regarded as tentative. The comparative gene maps of human chromosome 7, bovine syntenic group U13, and mouse chromosomes 6 and 13 suggest extensive evolutionary conservation.  相似文献   

10.
To gain insights into the phylogeny of the Euglenales, we analyzed the plastid LSU rDNA sequences from 101 strains of the photosynthetic euglenoids belonging to nine ingroup genera (Euglena, Trachelomonas, Strombomonas, Monomorphina, Cryptoglena, Colacium, Discoplastis, Phacus, and Lepocinclis) and two outgroup genera (Eutreptia and Eutreptiella). Bayesian and maximum‐likelihood (ML) analyses resulted in trees of similar topologies and four major clades: a Phacus and Lepocinclis clade; a Colacium clade; a Trachelomonas, Strombomonas, Monomorphina, and Cryptoglena clade; and a Euglena clade. The Phacus and Lepocinclis clade was the sister group of all other euglenalian genera, followed by Discoplastis spathirhyncha (Skuja) Triemer and the Colacium clade, respectively, which was inconsistent with their placement based on nuclear rDNA genes. The Trachelomonas, Strombomonas, Monomorphina, and Cryptoglena clade was sister to the Euglena clade. The loricate genera, Trachelomonas and Strombomonas, were closely related to each other, while Monomorphina and Cryptoglena also grouped together. The Euglena clade formed a monophyletic lineage comprising most species from taxa formerly allocated to the subgenera Calliglena and Euglena. However, within this genus, none of the subgenera was monophyletic.  相似文献   

11.
Drosophila is the genus responsible for the birth of experimental genetics, but the taxonomy of drosophilids is difficult because of the overwhelming diversity of the group. In this study, we assembled sequences for 358 species (14 genera, eight subgenera, 57 species groups, and 65 subgroups) to generate a maximum‐likelihood topology and a Bayesian timescale. In addition to sampling an unprecedented diversity of Drosophila lineages, our analyses incorporated a geographical perspective because of the high levels of endemism. In our topology, Drosophila funebris (Fabricius, 1787) (the type species of Drosophila) is tightly clustered with the pinicola subgroup in a North American clade within subgenus Drosophila. The type species of other drosophilid genera fall within the Drosophila radiation, presenting interesting prospects for the phylogenetic taxonomy of the group. Our timescale suggests that a few drosophilid lineages survived the Cretaceous–Palaeogene (K‐Pg) extinction. The drosophilid diversification began during the Palaeocene in Eurasia, but peaked during the Miocene, an epoch of drastic climatic changes. The most recent common ancestor of the clades corresponding to subgenera Sophophora and Drosophila lived approximately 56 Mya. Additionally, Hawaiian drosophilids diverged from an East Asian lineage approximately 26 Mya, which is similar to the age of the oldest emerging atoll in the Hawaiian–Emperor Chain. Interestingly, the time estimates for major geographical splits (New World versus Asia and Africa versus Asia) were highly similar for independent lineages. These results suggest that vicariance played a significant role in the radiation of fruit flies. © 2013 The Linnean Society of London  相似文献   

12.
Recent analysis of the complete mosquito Anopheles gambiae genome has revealed a far higher number of opsin genes than for either the Drosophila melanogaster genome or any other known insect. In particular, the analysis revealed an extraordinary opsin gene content expansion, whereby half are long wavelength-sensitive (LW) opsin gene duplicates. We analyzed this genomic data in relationship to other known insect opsins to estimate the relative timing of the LW opsin gene duplications and to identify "missing" paralogs in extant species. The inferred branching patterns of the LW opsin gene family phylogeny indicate at least one early gene duplication within insects before the emergence of the orders Orthoptera, Mantodea, Hymenoptera, Lepidoptera, and Diptera. These data predict the existence of one more LW opsin gene than is currently known from most insects. We tested this prediction by using a degenerate PCR strategy to screen the hymenopteran genome for novel LW opsin genes. We isolated two LW opsin gene sequences from each of five bee species, Bombus impatiens, B. terrestris, Diadasia afflicta, D. rinconis, and Osmia rufa, including 1.1 to 1.2 kb from a known (LW Rh1) and 1 kb from a new opsin gene (LW Rh2). Phylogenetic analysis suggests that the novel hymenopteran gene is orthologous to A. gambiae GPRop7, a gene that is apparently missing from D. melanogaster. Relative rate tests show that LW Rh2 is evolving at a slower rate than LW Rh1 and, therefore, may be a useful marker for higher-level hymenopteran systematics. Site-specific rate tests indicate the presence of several amino acid sites between LW Rh1 and LW Rh2 that have undergone shifts in selective constraints after duplication. These sites and others are discussed in relationship to putative structural and functional differences between the two genes.  相似文献   

13.
We have sequenced most of the coding region of the gene Dopa decarboxylase (Ddc) in 24 fruitfly species. The Ddc gene is quite informative about Drosophila phylogeny. Several outstanding issues in Drosophila phylogeny are resolved by analysis of the Ddc sequences alone or in combination with three other genes, Sod, Adh, and Gpdh. The three species groups, melanogaster, obscura, and willistoni, are each monophyletic and all three combined form a monophyletic group, which corresponds to the subgenus Sophophora. The Sophophora subgenus is the sister group to all other Drosophila subgenera (including some named genera, previously considered outside the Drosophila genus, namely, Scaptomyza and Zaprionus, which are therefore downgraded to the category of subgenus). The Hawaiian Drosophila and Scaptomyza are a monophyletic group, which is the sister clade to the virilis and repleta groups of the subgenus Drosophila. The subgenus Drosophila appears to be paraphyletic, although this is not definitely resolved. The two genera Scaptodrosophila and Chymomyza are older than the genus Drosophila. The data favor the hypothesis that Chymomyza is older than Scaptodrosophila, although this issue is not definitely resolved. Molecular evolution is erratic. The rates of nucleotide substitution in 3rd codon position relative to positions 1 + 2 vary from one species lineage to another and from gene to gene. Received: 2 June 1998 / Accepted: 3 September 1998  相似文献   

14.
Molecular sequences now overwhelm morphology in phylogenetic inference. Nonetheless, most molecular studies are conducted on a limited number of taxa, as DNA rarely can be analysed from old museum types or fossils. During the last 20 years, more than 150 molecular studies have challenged the current phylogenetic classification of the family Drosophilidae Rondani based on morphological characters. Most studies concerned a single genus, Drosophila Fallén, and included only few representative species from 17 out of the 78 genera of the family. Therefore, these molecular studies were unable to provide an alternative classification scheme. A supermatrix analysis of seven nuclear and one mitochondrial genes (8248 bp) for 33 genera was conducted using outgroups from one calyptrate and four ephydroid families. The Bayesian phylogeny was consistent with previous molecular studies including whole genome sequences and divided the Drosophilidae into four monophyletic clades. Morphological characters, mostly male genitalia, then were compared thoroughly between the four clades and homologous character states were identified. These states were then checked for 70 genera and a revised phylogenetic, family‐group classification for the Drosophilidae is proposed. Two genera –Cladochaeta Coquillett and Diathoneura Duda – of the tribe Cladochaetini Grimaldi are transferred to the family Ephydridae. The Drosophilidae is divided into two subfamilies: Steganinae Hendel (30 genera) and Drosophilinae Rondani (43 genera). A further two genera, Apacrochaeta Duda and Sphyrnoceps de Meijere, are incertae sedis, and Palmophila Grimaldi, is synonymized with Drosophila syn.n. The Drosophilinae is subdivided into two tribes: the re‐elevated Colocasiomyini Okada (nine genera) and Drosophilini Okada. The paraphyly of the genus Drosophila was not resolved to avoid affecting the binomina of important laboratory model species; however, its subgeneric classification was revised in light of molecular and morphological data. Three subgenera, namely Chusqueophila Brncic, Phloridosa Sturtevant and Psilodorha Okada, were synonymized with the subgenus Drosophila (Drosophila) Fallén syns.n. Among the 45 species groups and 5 species complexes of Drosophila (Drosophila), 22 groups and 1 complex were transferred to the subgenus Drosophila (Siphlodora) Patterson & Mainland and 6 groups, 2 species subgroups and 3 complexes are considered incertae sedis within the genus Drosophila. Different morphological characters provide different signals at different phylogenetic scales: thoracic characters (wing venation and presternal shape) discriminate families; grasping and erection‐related characters discriminate subfamilies to tribes; whereas phallic paraphyses, i.e. auxiliary intromittent organs, discriminate genera and Drosophila subgenera. The study shows the necessity of analysing morphological characters within a molecular phylogenetic framework to translate molecular phylogenies into taxonomically‐comprehensive classifications.  相似文献   

15.
Until recently, Histoplasma capsulatum was believed to harbour three varieties, var. capsulatum (chiefly a New World human pathogen), var. duboisii (an African human pathogen) and var. farciminosum (an Old World horse pathogen), which varied in clinical manifestations and geographical distribution. We analysed the phylogenetic relationships of 137 individuals representing the three varieties from six continents using DNA sequence variation in four independent protein‐coding genes. At least eight clades were idengified: (i) North American class 1 clade; (ii) North American class 2 clade; (iii) Latin American group A clade; (iv) Latin American group B clade; (v) Australian clade; (vi) Netherlands (Indonesian?) clade; (vii) Eurasian clade and (viii) African clade. Seven of eight clades represented genetically isolated groups that may be recognized as phylogenetic species. The sole exception was the Eurasian clade which originated from within the Latin American group A clade. The phylogenetic relationships among the clades made a star phylogeny. Histoplasma capsulatum var. capsulatum individuals were found in all eight clades. The African clade included all of the H. capsulatum var. duboisii individuals as well as individuals of the other two varieties. The 13 individuals of var. farciminosum were distributed among three phylogenetic species. These findings suggest that the three varieties of Histoplasma are phylogenetically meaningless. Instead we have to recognize the existence of genetically distinct geographical populations or phylogenetic species. Combining DNA substitution rates of protein‐coding genes with the phylogeny suggests that the radiation of Histoplasma started between 3 and 13 million years ago in Latin America.  相似文献   

16.
Summary We have performed DNA-DNA hybridization experiments among several species of Drosophila using the evolutionarily conserved portion of the genome representing sequences coding for amino acids of proteins. This was done by using as tracer, radioactively labeled complementary DNA that was reverse transcribed from adult mRNA. We show that this procedure extends phylogenetically the distance over which the technique can be applied to fast-evolving groups such as Drosophila. The major phylogenetic conclusions are (1) the subgenus Sophophora is a monophyletic lineage; (2) within Sophophora the melanogaster subgroup is closer to the obscura group than either group is to the willistoni group; (3) the subgenus Drosophila is complex with most major lineages originating deep in the phylogeny; the subgenus may not be monophyletic; (4) as with most groups classically placed in Drosophila, the Hawaiian Drosophila originate early, supporting the notion that this lineage is older than the extant islands; and (5) the virilis/repleta lineage is monophyletic within Drosophila.On leave from the Dipartimento di Biologia, II Università di Roma Tor Vergata, Rome, Italy  相似文献   

17.
 The phylogeny of the genus Gunnera is investigated for the first time. Twelve species representing the six currently recognised subgenera are analysed. Two chloroplast DNA regions, the rbcL gene and the rps16 intron, together provide 46 informative characters out of 2335. A combined analysis of both genes gives four most parsimonious trees, firmly establishing the east South American G. herteri as sister group to the rest of the genus. The African G. perpensa is sister group to two well-supported clades, one including the South American subgenera Misandra and Panke, the other the Australian/New Zealand/Malayan species of subgenera Milligania and Pseudogunnera. Thus, South America is a composite area for Gunnera, showing up at two different levels in the cladogram. Our analysis supports a close biogeographic relationship between Australia and New Zealand. The evolution of some morphological characters is discussed. Lastly, the unusual structure of some of the rbcL sequences is reported. Received July 6, 2000 Accepted October 24, 2000  相似文献   

18.
Jeon, M.‐J., Song, J.‐H. & Ahn, K.‐J. (2012). Molecular phylogeny of the marine littoral genus Cafius (Coleoptera: Staphylinidae: Staphylininae) and implications for classification. —Zoologica Scripta, 41, 150–159. A phylogenetic analysis of the marine littoral genus Cafius Stephens is presented based on molecular characters. The data set comprised partial mitochondrial COI (910 bp), COII (369 bp), 12S rDNA (351–354 bp), 16S rDNA (505–509 bp) and nearly complete sequences of 18S rDNA (1814–1830 bp) for 37 species. Twenty‐seven Cafius species, representing five of six subgenera, two Remus Holme species, three Phucobius Sharp species, monotypic Thinocafius Steel and four outgroups were included. The sequences were analysed simultaneously by parsimony analysis in Tree Analysis Using New Technology (TNT) with traditional manual alignment, direct optimization (DO) in the program POY4 under a variety of gap costs and partitioned Bayesian analysis for the combined data. The genus Cafius and nearly all of its subgenera were not supported as being monophyletic. Instead, all analyses (parsimony trees, DO tree under equal weighting and Bayesian tree) showed monophyly of Cafius + Phucobius + Remus + Thinocafius (clade Z) and all seven nested clades (A–G). However, the phylogenetic relationships among clades A–G differed among the analyses. The genus Phucobius was recovered as a monophyletic group within Cafius. The genus Remus was not monophyletic but formed a clade with C. rufescens Sharp and C. rufifrons Bierig within Cafius. The genus Thinocafius formed a clade with C. caviceps Broun, C. litoreus (Broun) and C. quadriimpressus (White) within Cafius. We propose new concepts for the genus Cafius and its related genera, and the seven nested clades.  相似文献   

19.
Summary We have studied the evolutionary changes occurring in the noncoding regions around the developmentally important fushi tarazu (ftz) gene in a total of 11 species in the genus Drosophila. Previous molecular developmental studies have identified DNA elements both 3 and 5 to the coding region which are important in proper regulation of expression of the Drosophila melanogaster ftz gene. We show here that these same elements are the most evolutionarily conserved regions in the vicinity of the gene homologs. Parts of some control elements are more conserved than exonic sequences. Not only is there sequence conservation, but the relative position, orientation, and distances among the control elements remain conserved. One quite significant difference does exist between the two major subgenera studied, Sophophora and Drosophila: namely, an inversion of the ftz unit with respect to other genes in the Antennapedia complex, ANT-C. As a comparison, we applied similar analysis to a housekeeping gene-rosy (ry), or Xdh. In contrast, DNA sequences 5 to the ry coding region revealed little evolutionary conservation. These studies bear out the proposition that functionally important DNA sequences remain more conserved through evolutionary time than do less functionally important sequences. This proposition could be tested in the present case because we could predict a priori from the developmental studies which DNA regions should be most conserved.  相似文献   

20.
It has been hypothesized that the UV-, blue-, and green-sensitive visual pigments of insects were present in the common ancestor of crustaceans and insects, whereas red-sensitive visual pigments evolved later as a result of convergent evolution. This hypothesis is examined with respect to the placement of six opsins from the swallowtail butterfly Papilio glaucus (PglRh1–6) in relationship to 46 other insect, crustacean, and chelicerate opsin sequences. All basal relationships established with maximum parsimony analysis except two are present in the distance and maximum likelihood analyses. In all analyses, the six P. glaucus opsins fall into three well-supported clades, comprised, respectively, of ultraviolet (UV), blue, and long-wavelength (LW) pigments, which appear to predate the radiation of the insects. Lepidopteran green- and red-sensitive visual pigments form a monophyletic clade, which lends support to the hypothesis from comparative physiological studies that red-sensitive visual pigments in insects have paralogous origins. Polymorphic amino acid sites (180, 197, 277, 285, 308), which are essential for generating the spectral diversity among the vertebrate red- and green-sensitive pigments are notably invariant in the Papilio red- and green-sensitive pigments. Other major tuning sites must be sought to explain the spectral diversification among these and other insect visual pigments. Received: 6 December 1999 / Accepted: 3 April 2000  相似文献   

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