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1.
Recently discovered coccospheres with combinations of coccoliths normally considered to belong to different taxa are presented here. By analogy with other coccolithophorids especially Coccolithus pelagicus we can hypothesize that these associations probably represent moments of phase change in a complex, possibly haplo-diplontic, life-cycle. Seven of these associations are composed of heterococcoliths with holococcoliths; five of them are presented here for the first time: Helicosphaera carteri with Syracolithus catilliferus, Syracosphaera pulchra with Calyptrosphaera oblonga, Syracosphaera anthos with Periphyllophora mirabilis, Acanthoica quattrospina with holococcolithophorid sp. and Syracosphaera sp. with Corisphaera sp. type A (see Kleijne, A., 1991. Holococcolithophorids from the Indian Ocean, Red Sea, Mediterranean Sea and North Atlantic Ocean. Mar. Micropaleontol. 17, 1–76); the other two are Coronosphaera mediterranea with Calyptrolithina wettsteinii, found previously by Kamptner (Kamptner, E., 1941. Die Coccolithineen der Südwestküste von Istrien. Naturhistorischen Museum in Wien. Annalen 51, 54–149), and Syracosphaera nana with undescribed holococcoliths, figured previously by Kleijne (1991) as Syracosphaera sp. type A. In addition the association of Neosphaera coccolithomorpha and Ceratolithus cristatus, recently presented by Alcober and Jordan (Alcober, J., Jordan, R.W., 1997. An interesting association between Neosphaera coccolithomorpha and Ceratolithus cristatus (Haptophyta). Eur. J. Phycol. 32, 91–93) is verified by discovery of a further example. A further five combinations of heterococcoliths and holococcoliths are shown, these probably mostly represent life-cycle combinations but the evidence in each case is insufficient to consider these as definite associations although in these collapsed coccospheres the association of different species is less certain. Two examples of holococcolith–holococcolith associations are presented: S. catilliferus with Syracolithus confusus, and Zygosphaera bannockii with Corisphaera sp. type A. These are probably examples of intra-specific variation.A new species, Syracosphaera delicata sp. nov., is described.  相似文献   

2.
We have isolated sequences belonging to Tyl-copia group retrotransposons from the genomes of an amphibian (Pyxicephalus adspersa) and three reptiles (Conolophus subscristatus, Amblyrynchus cristatus and Pytas mucosus). Two different seqences were found in the amphibian (Tpa1 and Tpa2). Each is present in several copies per genome and absent from the genomes of two other amphibian species. The C. subcristatus sequence Tcs1 is present in multiple copies in both its host genome (Galapagos land iguana) and the genome of the related Galapagos marine iguana (A. cristatus). There is little or no polymorphism in Tcs1 insertions between different individual animals, suggesting that this sequence is not transposing rapidly in either iguana genome. The P. mucosus sequence Tpm1 shows a discontinuous distribution in snake species, suggesting that it has either been lost from many lineages during vertical germline transmission or has been transferred horizontally in some snake species. Phylogenetic comparisons of all these sequences with each other and with other members of this retrotransposon group from other animals and plants show that sequences within a particular vertebrate species are most closely related to each other, consistent with a vertical transmission model for their evolution.  相似文献   

3.
蒋天翼  陈志钊  陈曌  郑永利  陈昕  邓云飞 《广西植物》2023,43(10):1814-1827
为澄清映山红亚属(Rhododendron subg. Tsutsusi)内的系统关系问题,该研究选择杜鹃花属映山红亚属37种植物作为对象,其中29种为首次报道,通过扫描电镜观察其叶表皮显微特征。结果表明:(1)气孔器均为无规则型且均在远轴面。(2)根据叶片微形态特征将映山红亚属的种类分为杜鹃型(R. simisii-type)、岭南杜鹃型(R. mariae-type)、皋月杜鹃型(R. indicum-type)、崖壁杜鹃型(R. saxatile-type)及丁香杜鹃型(R. farrerae-type)5种类型。(3)杜鹃型植物的气孔器周边无或具间断的条形突起。(4)岭南杜鹃型植物的气孔器周围有多层条形突起环绕,保卫细胞两极不具T型加厚。(5)皋月杜鹃型植物的叶表皮保卫细胞两极具有T型加厚,与叶状苞亚属(Subg. Therorhodion)叶状苞杜鹃(R. redowskianum)的气孔器特征相似,推测其与叶状苞亚属具有一定的亲缘关系。(6)崖壁杜鹃型植物的叶表皮毛单一,多呈卷曲状,与其他类型有所不同且未见腺体。(7)丁香杜鹃型植物的叶表皮仅有腺体。(8)依据叶表皮微形态特征讨论了一些近缘种类的关系,如倾向于将背绒杜鹃(R. hypoblematosum)和千针叶杜鹃(R. polyraphidoideum)处理为独立的种,支持保留紫薇春(R. naamkwanense var. cryptonerve)作为南昆杜鹃(R. naamkwanense)的变种地位,不支持将腺花杜鹃(R. adenanthum)并入细瘦杜鹃(R. tenue)作异名处理等。该研究结果表明叶表皮显微特征在映山红亚属内物种划分上具有重要价值。  相似文献   

4.
Two hybridizing species of newts, Triturus cristatus and T. marmoratus, with overlapping distributions show a parapatric distribution when surveyed in detail. The factors that govern the distribution of cristatus vs. marmoratus in the département (province) of Mayenne in western France are identified as forestation and relief. The parapatric hybrid zone running through Mayenne is narrow but widens to approximately 20 km in an area with mixed habitat. In this area most breeding sites are shared and F1 hybrids form about 4% of the total population. Analysis of survey data collected about 30 years previously also shows an essentially parapatric distribution. Comparison of past and present distribution maps reveals that cristatus has superseded marmoratus over large areas in the south of Mayenne. An area where marmoratus replaced cristatus also exists, but it is more limited in size. Gene flow between cristatus and marmoratus is analyzed using 10 diagnostic genetic markers [9 protein loci and mitochondrial (mt) DNA]. In syntopic populations nuclear gene flow is bidirectional with a mean frequency of introgressed alleles (f) of 0.3%. In allotopic populations of cristatus and marmoratus gene flow is present in areas of species replacement (f = 0.3%), while gene flow appears to be absent in those areas that have been continuously occupied by a single species. At the biogeographic level, the presence or absence of introgression is paralleled by the persistence or absence, respectively, of pockets of cristatus–marmoratus syntopy. All F1 hybrids possess the cristatus type mtDNA. This may be due to asymmetric interspecific mate choice and would explain the observed absence of introgression of the maternally inherited mtDNA genome in areas where cristatus replaced marmoratus. The cristatus–marmoratus hybrid zone bears characteristics of both the clinal (parapatric) hybrid zone model and the mosaic hybrid zone model. Such a mixed model—for which we propose the term “reticulate hybrid zone”—can be appreciated only if studied over a two-dimensional geographic area and also through time.  相似文献   

5.
6.
Although interspecific differences in the relative development of molar occlusal features have been documented for most primate species, wear-related changes in these features are only beginning to be understood. In the present study, the notch between the metaconid and entoconid of M2 was examined in a skeletal sample of Macaca fascicularis, Presbytis cristatus, and Presbytis rubicunda from the Museum of Comparative Zoology at Harvard University. Photogrammetric analyses yielded X, Y, and Z coordinates that were used to compute three angular measurements and two length measurements at the lingual notch. Statistical analyses of measurements from unworn dentitions indicated that the mesial slope of the entoconid is steeper than the distal slope of the metaconid in all three species. In addition, interspecific comparisons demonstrated that P. cristatus has the steepest lingual notch bordered by the largest molar shearing crests, while P. rubicunda and M. fascicularis have molar shearing crests of similar size, with P. rubicunda merely having higher cusps that are closer together than those of M. fascicularis. Fanally, P. cristatus shows a smaller decrease in lingual cusp relief with wear than M. fascicularis, while P. cristatus and P. rubicunda probably show similar decreases in lingual cusp relief with wear. The differences in wear-related changes in lingual cusp relief between M. fascicularis and P. cristatus may well be related to the frugivorous/folivorous dietary differences between these species.  相似文献   

7.
It has been suggested that two groups ofEscherichia coli genes, theccm genes located in the 47-min region and thenrfEFG genes in the 92-min region of the chromosome, are involved in cytochromec biosynthesis during anaerobic growth. The involvement of the products of these genes in cytochromec synthesis, assembly and secretion has now been investigated. Despite their similarity to other bacterial cytochromec assembly proteins, NrfE, F and G were found not to be required for the biosynthesis of any of thec-type cytochromes inE. coli. Furthermore, these proteins were not required for the secretion of the periplasmic cytochromes, cytochromec 550 and cytochromec 552, or for the correct targeting of the NapC and NrfB cytochromes to the cytoplasmic membrane. NrfE and NrfG are required for formate-dependent nitrite reduction (the Nrf pathway), which involves at least twoc-type cytochromes, cytochromec 552 and NrfB, but NrfF is not essential for this pathway. Genes similar tonrfE, nrfF andnrfG are present in theE. coli nap-ccm locus at minute 47. CcmF is similar to NrfE, the N-terminal region of CcmH is similar to NrfF and the C-terminal portion of CcmH is similar to NrfG. In contrast to NrfF, the N-terminal, NrfF-like portion of CcmH is essential for the synthesis of allc-type cytochromes. Conversely, the NrfG-like C-terminal region of CcmH is not essential for cytochromec biosynthesis. The data are consistent with proposals from this and other laboratories that CcmF and CcmH form part of a haem lyase complex required to attach haemc to C-X-X-C-H haem-binding domains. In contrast, NrfE and NrfG are proposed to fulfill a more specialised role in the assembly of the formate-dependent nitrite reductase.  相似文献   

8.
A 32–33 bp highly repeated DNA sequence, TkS1, has been isolated from genomic DNA of the newt Triturus karelini digested with the restriction endonucleases HaeIII or AluI. TkS1 is known to be localised in the centromeric heterochromatin of all the chromosomes in T. karelini and the related species T. cristatus TkS1 has been shown to be present in varying amounts in the genomic DNA of a range of species of Triturus, including representatives of the two main subgenera Triturus and Palaeotriton. A programme of sequencing of monomers, dimers and trimers of TkS1 was carried out in order to determine the level of conservation of the sequence within and between species of Triturus. Altogether 204 monomer (32/33 bp) clones were made of TkS1 from three individuals of T. karelini, and one individual each of T. cristatus, T. carnifex, T. dobrogicus and T. marmoratus, all members of the subgenus Triturus and the cristatus species group. A number of dimer (64 bp) and trimer (96 bp) clones were also made from DNA of a single specimen of T. karelini digested with HaeIII or AluI. Three distinct types of TkS1 were identified in all species examined, except for T. marmoratus where only two of the types were found. The types were distinguished on the basis of certain recurring divergent patterns in monomers sequenced from T. karelini. Type 1 is mainly characterised by the presence of an AluI site at positions 24–27 and type 3 mainly by the presence of an additional base (C) at position 14. Type 2 normally lacks the AluI site and the C at position 14, as well as having a number of other distinguishing features. TkS1 and its three types have remained remarkably constant in sequence since before the divergence of T. marmoratus from other species in the cristatus species group, about 10 million years ago. Examination of all 204 monomer clones and comparison with consensus sequences for the three types shows less than 5% divergence at any one position in the sequence. There is good evidence from examination of dimer and trimer clones of TkS1 that the different types are intermingled with each other, and all three types are likely to be present on all chromosomes. Dimeric (64 bp) TkS1 clones constructed from AluI fragments of T. karelini DNA show evidence of a trimeric (96 bp) supertype with the pattern type 1-type 3-type 1 that is much more common than would be expected on a random basis. The properties of TkS1 are discussed in relation to models for the involvement of highly repeated satellite DNA in chromosomal growth and evolution.W. Hennig  相似文献   

9.
Fomitiporia punicata sp. nov., collected from Shaanxi Province, northern China, and so far exclusively on Punica granatum (Punicaceae), is described and illustrated, and its preliminary phylogenetic relationships are inferred based on sequence data from the ribosomal ITS-5.8S regions. Fomitiporia punicata belongs to the F. robustaF. punctata complex, but is characterized by an effused–reflexed to pileate basidioma with triquetrous to ungulate pilei, pale yellowish brown to cinnamon brown pore surface, moderately thick-walled skeletal hyphae in the context, which are partly collapsed on drying, lack of setae, presence of fusoid to subulate cystidioles, and growth on Punica. It also forms a distinct clade within Fomitiporia, and is related to some species from the temperate or Mediterranean zone of the northern hemisphere. An identification key to the species of Fomitiporia recorded in China is provided. Fomitiporia tibetica is transferred to Pseudoinonotus.  相似文献   

10.
A new combination coccosphere of the heterococcolithophore Helicosphaera wallichii ( Lohman 1902 ) Okada and McIntyre 1977 and holococcolithophore Syracolithus ponticuliferus ( Kamptner 1941 ) Kleijne and Jordan 1990 is documented. This combination coccosphere was observed within a rich and diverse assemblage collected during late summer at a 20 m water depth from the NW Mediterranean Sea.  相似文献   

11.
Family characteristics of the Rhabdosphaeraceae are revised to limit the genera to those having cyrtoliths; genera with placoliths are removed from the family. Rhabdoliths, cyrtoliths bearing a process in the central area, are present in all genera. Coccospheres having monomorphic coccoliths, all being rhabdoliths, form one group within the family, whereas genera with dimorphic coccoliths in the coccosphere comprise a second group. Cyrtoliths without processes in the latter group may be intermixed with rhabdoliths in some genera, whereas other genera have rhabdoliths located only in polar regions of the coccosphere. Two generic nomenclatural changes are proposed, Algirosphaera being the name applied to species previously placed in Anthosphaera, an invalid generic name, and Palusphaera is recognized as a valid monotypic genus, P. vandeli being the name applied to the species that has been named Rhabdosphaera longistylis in recent literature. A new combination is made, Rhabdosphaera xiphos (Deflandre et Fert) comb. nov., recognizing a species formerly known only in sediments as extant. Rhabdosphaera, Acanthoica and Algirosphaera are genera with dimorphic coccoliths in the coccospheres; Discosphaera, Palusphaera and Anacanthoica are genera having monomorphic coccoliths in the coccosphere.  相似文献   

12.
A nonplanar distortion of the heme ofc-type cytochromes is conserved in the proteins isolated from diverse species based upon a comprehensive analysis of available highresolution X-ray crystal structures. This distortion is induced through the cysteine thioether linkages between the porphyrin pyrrole groups and the polypeptide and results in an asymmetric pyrrole distortion. This asymmetry in the heme distortion is also conserved. For other heme proteins which lack these covalent bonds, nearly planar porphyrins are observed. Resonance Raman evidence indicates that nonplanar distortion of porphyrins containing metals, like iron, with large core sizes (2.00 Å) is energetically unfavorable and can occur only in the presence of significant environmental perturbations. Further, energy minimization and dynamics calculations on the ferric form of yeast iso-1-cytochromec, starting from the crystallographic coordinates and using a molecular mechanics force field which accurately reproduces nonplanar distortions in metalloporphyrins, suggest that this distortion is indeed maintained by the protein tertiary structure. It is proposed that this protein-linked heme distortion modulates electron transfer function through modification of redox potentials of the porphyrin ring and the protein binding properties ofc-type cytochromes.  相似文献   

13.
The hypothesis that similar conidial morphologies in aquatic hyphomycetes are a result of convergent evolution was tested using molecular sequence data. Cladistic analyses were performed on partial sequences of 28S rDNA of seven species of Lemonniera, one species of Margaritispora and one species of Goniopila. Lemonniera has tetraradiate conidia with long arms, whereas Margaritispora and Goniopila have typically globose (isodiametric) conidia, with short conical protuberances in a stellate or quadrangular arrangement. Lemonniera and Margaritispora have phialidic conidiogenesis and both produce dark, minute sclerotia in culture whereas Goniopila has holoblastic conidiogenesis and does not produce sclerotia in culture. Goniopila produces a microconidial phialidic synanamorph in culture. All three genera have schizolytic conidial secession. Molecular analyses demonstrate that Lemonniera species are placed in two distinct clades: one within Leotiomycetes; the other within Pleosporales, Dothideomycetes. Margaritispora is placed with Lemonniera species within Leotiomycetes. Goniopila and Lemonniera pseudofloscula are placed within Dothideomycetes. No morphological character was entirely congruent with the molecular derived phylogeny. This suggests that for the group of species studied, conidial shape is not a reliable indicator of phylogeny but more likely the result of convergent evolution in response to the aquatic environment.  相似文献   

14.
The development of microsatellite loci has become more efficient using next‐generation sequencing (NGS) approaches, and many studies imply that the amount of applicable loci is large. However, few studies have sought to quantify the number of loci that are retained for use out of the thousands of sequence reads initially obtained. We analyzed the success rate of microsatellite loci development for three amphibian species using a 454 NGS approach on tetra‐nucleotide motif‐enriched species‐specific libraries. The number of sequence reads obtained differed strongly between species and ranged from 19,562 for Triturus cristatus to 55,626 for Lissotriton helveticus, with 52,075 reads obtained for Calotriton asper. PHOBOS was used to identify sequences with tetra‐nucleotide repeat motifs with a minimum repeat number of ten and high quality primer binding sites. Of 107 sequences for T. cristatus, 316 for C. asper and 319 for L. helveticus, we tested the amplification success, polymorphism, and degree of heterozygosity for 41 primer combinations each for C. asper and T. cristatus, and 22 for L. helveticus. We found 11 polymorphic loci for T. cristatus, 20 loci for C. asper, and 15 loci for L. helveticus. Extrapolated, the number of potentially amplifiable loci (PALs) resulted in estimated species‐specific success rates of 0.15% (T. cristatus), 0.30% (C. asper), and 0.39% (L. helveticus). Compared with representative Illumina NGS approaches, our applied 454‐sequencing approach on specifically enriched sublibraries proved to be quite competitive in terms of success rates and number of finally applicable loci.  相似文献   

15.
Reproductive isolation barriers maintain the integrity of species by preventing interspecific gene flow. They involve temporal, habitat or behavioral isolation acting before fertilization, and postzygotic isolation manifested as hybrid mortality or sterility. One of the approaches of how to study reproductive isolation barriers is through the analysis of hybrid zones. In this paper, we describe the structure of a hybrid zone between two crested newt species (Triturus cristatus and T. carnifex) in the southern part of the Czech Republic using morphological, microsatellite, and mitochondrial (mtDNA) markers. Specifically, we tested the hypothesis that the structure of the hybrid zone is maintained by species‐specific habitat preferences. Comparing the genetic structure of populations with geographical and ecological parameters, we found that the hybrid zone was structured primarily geographically, with T. cristatus‐like populations occurring in the northeast and T. carnifex‐like populations in the southwest. Despite T. cristatus tending to occur in deeper ponds and T. carnifex on localities with more shading, the effect of both ecological parameters on the structure of the zone was minimal. Next, we corroborated that T. carnifex individuals and some hybrids possess mtDNA of T. dobrogicus, whose nuclear background was not detected in the studied hybrid zone. Hybridization between T. carnifex and T. dobrogicus (resulting in unidirectional mtDNA introgression) had to predate subsequent formation of the hybrid zone between T. cristatus and T. carnifex. Populations of crested newts in the southern part of the Czech Republic thus represent a genetic mosaic of nuclear and mitochondrial genomes of three species.  相似文献   

16.
A spherical coccosphere and two collapsed coccospheres composed of monomorphic rhombic coccoliths were encountered in 2005 in the Java upwelling system of the SE Indian Ocean, while a further two specimens with elongate coccospheres were recently found in the Gulf of Mexico. All of the specimens were collected from the lower photic zone (75–160 m). The coccoliths possess a proximal flange, a slightly flared wall with a serrated distal margin, and a relatively plain central area structure comprised only of overlapping laths. The taxon appears to be an undescribed species of the Syracosphaera nodosa group, so we describe it herein as Syracosphaera rhombica sp. nov.  相似文献   

17.
The morphology of three remarkable genera of coccolithophores, Ophiaster, Michaelsarsia, and Calciopappus, is reviewed based on new images using field emission scanning electron microscopy. Each of these genera characteristically forms coccospheres with long appendages formed of highly modified coccoliths, which radiate from either the circum‐flagellar pole of the coccosphere (Calciopappus and Michaelsarsia) or the antapical pole (Ophiaster). For each genus, it is shown that the appendage coccoliths can also occur in an alternative orientation appressed to the main coccosphere. It is hypothesized that the appendage coccoliths are initially deployed in the appressed orientation and that extension of the appendages is a dynamic response to environmental stress. The observations suggest that coccoliths are more sophisticatedly adapted to specific functions than has been assumed and that the cytoskeleton plays more active roles in coccolith morphogenesis and deployment than has previously been inferred.  相似文献   

18.
Environmental DNA (eDNA) analysis is a rapid, cost‐effective, non‐invasive biodiversity monitoring tool which utilises DNA left behind in the environment by organisms for species detection. The method is used as a species‐specific survey tool for rare or invasive species across a broad range of ecosystems. Recently, eDNA and “metabarcoding” have been combined to describe whole communities rather than focusing on single target species. However, whether metabarcoding is as sensitive as targeted approaches for rare species detection remains to be evaluated. The great crested newt Triturus cristatus is a flagship pond species of international conservation concern and the first UK species to be routinely monitored using eDNA. We evaluate whether eDNA metabarcoding has comparable sensitivity to targeted real‐time quantitative PCR (qPCR) for T. cristatus detection. Extracted eDNA samples (N = 532) were screened for T. cristatus by qPCR and analysed for all vertebrate species using high‐throughput sequencing technology. With qPCR and a detection threshold of 1 of 12 positive qPCR replicates, newts were detected in 50% of ponds. Detection decreased to 32% when the threshold was increased to 4 of 12 positive qPCR replicates. With metabarcoding, newts were detected in 34% of ponds without a detection threshold, and in 28% of ponds when a threshold (0.028%) was applied. Therefore, qPCR provided greater detection than metabarcoding but metabarcoding detection with no threshold was equivalent to qPCR with a stringent detection threshold. The proportion of T. cristatus sequences in each sample was positively associated with the number of positive qPCR replicates (qPCR score) suggesting eDNA metabarcoding may be indicative of eDNA concentration. eDNA metabarcoding holds enormous potential for holistic biodiversity assessment and routine freshwater monitoring. We advocate this community approach to freshwater monitoring to guide management and conservation, whereby entire communities can be initially surveyed to best inform use of funding and time for species‐specific surveys.  相似文献   

19.
When related species meet upon postglacial range expansion, hybrid zones are frequently formed. Theory predicts that such zones may move over the landscape until equilibrium conditions are reached. One hybrid zone observed to be moving in historical times (1950–1979) is that of the pond‐breeding salamanders Triturus cristatus and Triturus marmoratus in western France. We identified the ecological correlates of the species hybrid zone as elevation, forestation, and hedgerows favoring the more terrestrial T. marmoratus and pond density favoring the more aquatic T. cristatus. The past movement of the zone of ca. 30 km over three decades has probably been driven by the drastic postwar reduction of the “bocage” hedgerow landscape, favoring T. cristatus over T. marmoratus. No further hybrid zone movement was observed from 1979 to the present. To explain the changing dynamics of the hybrid zone, we propose that it stalled, either because an equilibrium was found at an altitude of ca. 140 m a.s.l. or due to pond loss and decreased population densities. While we cannot rule out the former explanation, we found support for the latter. Under agricultural intensification, ponds in the study area are lost at an unprecedented rate of 5.5% per year, so that remaining Triturus populations are increasingly isolated, hampering dispersal and further hybrid zone movement.  相似文献   

20.
We report on the expression of a VEGF-like protein encoded by Parapoxvirus ovis in the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe. We show that a lysine residue at amino acid position 2 (K2) is an important determinant for the stability of this protein in S. cerevisiae. Replacement of K2 by an arginine results in stabilization of the protein. This observation suggests that this lysine may be a target for ubiquitinylation, which is a prerequisite for proteasome-mediated protein degradation. Interestingly, in S. pombe the lysine (K2) has no influence on the stability of the protein. This result indicates that the two yeast species exhibit significant differences in their protein degradation pathways.  相似文献   

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