全文获取类型
收费全文 | 78篇 |
免费 | 8篇 |
出版年
2021年 | 1篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 6篇 |
2012年 | 5篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2009年 | 6篇 |
2008年 | 3篇 |
2007年 | 1篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1980年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有86条查询结果,搜索用时 31 毫秒
11.
Among temperate cnidarian symbioses, the partnership between the intertidal anemone Anthopleura elegantissima and its dinoflagellate and chlorophyte symbionts is one of the most well characterized. Biogeographic, reciprocal transplant, and physiological studies have convincingly demonstrated a relationship between environmental factors such as temperature and irradiance and the distribution of symbionts from both algal phyla. However, little is known about the fine-scale diversity or biogeographic distribution within symbiont lineages of this anemone. We used sequence information from the mitochondrial cytochrome b and chloroplast 23S ribosomal genes and restriction fragment length polymorphism data from the 18S nuclear ribosomal gene to characterize the Symbiodinium populations in tentacles clipped from 105 anemones at 14 sites along the entire California coast, spanning about 1200 km. Our results show the presence of at least three primary biogeographic regions with breaks around Cape Mendocino and Monterey Bay, each dominated by a different Symbiodinium muscatinei genotype. Sharp clines suggest limited gene flow between adjacent regions. Few sampling locations or individual anemones showed symbiont diversity at either organellar locus within the limits of our detection method, while sequence analysis of cloned nr18S polymerase chain reaction product suggests that nuclear pseudogenes may underlie intra-host diversity observed at that locus. 相似文献
12.
Physiologically distinct lines of dinoflagellate symbionts, Symbiodinium spp., may confer distinct thermal tolerance thresholds on their host corals. Therefore, if a coral can alternately host distinct
symbionts, changes in their Symbiodinium communities might allow corals to better tolerate increasing environmental temperatures. However, researchers are currently
debating how commonly coral species can host different symbiont types. We sequenced chloroplast 23 s rDNA from the Symbiodinium communities of nine reef-building coral species across two thermally distinct lagoon pools separated by ~500 m. The hotter
of these pools reaches 35°C in the summer months, while the other pool’s maximum temperature is 1.5°C cooler. Across 217 samples
from nine species, we found a single haplotype in both Symbiodinium clades A and D, but four haplotypes in Symbiodinium clade C. Eight of nine species hosted a putatively thermally resistant member of clade D Symbiodinium at least once, one of which hosted this clade D symbiont exclusively. Of the remaining seven that hosted multiple Symbiodinium types, six species showed higher proportions of the clade D symbiont in the hotter pool. Average percentage rise in the frequency
of the clade D symbiont from the hotter to cooler pool was 52% across these six species. Even though corals hosted members
of both the genetically divergent clades D and C Symbiodinium, some showed patterns of host–symbiont specificity within clade C. Both Acropora species that hosted clade C exclusively hosted a member of sub-clade C2, while all three Pocillopora species hosted a member of sub-clade C1 (sensu van Oppen et al. 2001). Our results suggest that coral–algal symbioses often conform to particular temperature environments through changes in
the identity of the algal symbiont. 相似文献
13.
Marine speciation on a small planet 总被引:2,自引:0,他引:2
Palumbi SR 《Trends in ecology & evolution》1992,7(4):114-118
The scale of population structure in many marine species is on the order of thousands to tens of thousands of kilometers. How does speciation take place in oceans that are only about this same size? Recent results suggest an important role for transient isolation, gamete ecology and molecular evolution at gamete recognition loci. These factors have long been appreciated by plant biologists, and are likely to be a fruitful area of research for marine biologists as well. 相似文献
14.
Stephen R. Palumbi Gail Grabowsky Thomas Duda Laura Geyer Nicholas Tachino 《Evolution; international journal of organic evolution》1997,51(5):1506-1517
Unlike populations of many terrestrial species, marine populations often are not separated by obvious, permanent barriers to gene flow. When species have high dispersal potential and few barriers to gene flow, allopatric divergence is slow. Nevertheless, many marine species are of recent origin, even in taxa with high dispersal potential. To understand the relationship between genetic structure and recent species formation in high dispersal taxa, we examined population genetic structure among four species of sea urchins in the tropical Indo-West Pacific that have speciated within the past one to three million years. Despite high potential for gene flow, mtDNA sequence variation among 200 individuals of four species in the urchin genus Echinometra shows a signal of strong geographic effects. These effects include (1) substantial population heterogeneity; (2) lower genetic variation in peripheral populations; and (3) isolation by distance. These geographic patterns are especially strong across scales of 5000-10,000 km, and are weaker over scales of 2500-5000 km. As a result, strong geographic patterns would not have been readily visible except over the wide expanse of the tropical Pacific. Surface currents in the Pacific do not explain patterns of gene flow any better than do patterns of simple spatial proximity. Finally, populations of each species tend to group into large mtDNA regions with similar mtDNA haplotypes, but these regional boundaries are not concordant in different species. These results show that all four species have accumulated mtDNA differences over similar spatial and temporal scales but that the precise geographic pattern of genetic differentiation varies for each species. These geographic patterns appear much less deterministic than in other well-known coastal marine systems and may be driven by chance and historical accident. 相似文献
15.
Stephen R. Palumbi Bruce D. Sidell Rebecca Van Beneden Glenn D. Smith Dennis A. Powers 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1980,138(1):49-57
Summary In order to evaluate the role of glucose-phosphate isomerase (GPI) inFundulus heteroclitus, the isozymes and allozymes were purified and some of their physical and kinetic properties determined.Isozymes were purified from both liver (GPI-B) and muscle (GPI-A) tissue (Tables 1, 2). Gel filtration of the native enzyme and SDS-polyacrylamide gel electrophoresis indicated that all forms are dimers of approximately 110,000 Daltons (Figs. 4, 5). Although thermal stability studies revealed no differences between the allozymes, the isozymes were clearly different (Figs. 6, 7). Kinetic analysis showed further differences between isozymes inK
m for substrate andK
I for 6-phosphogluconate (Figs. 8, 9; Table 3). No significant differences were found between the allozymes of the B-locus under the conditions employed in this study.Based on the tissue specificities and the functional differences between isozymes, we propose a possible regulatory role for GPI-B inF. heteroclitus. The sensitivity of this isozyme to 6-phosphogluconate inhibition may allow GPI-B to act as a regulatory enzyme in the partitioning of carbon flow between glycolysis and the hexose monophosphate shunt.Abbreviations me
-mercaptoethanol
-
F6P
fructose-6-phosphate
-
G1P
glucose-1-phosphate
-
G6P
glucose-6-phosphate
-
G6Pase
glucose-6-phosphatase
-
G6PDH
glucose-6-phosphate dehydrogenase
-
GPI
glucosephosphate isomerase
-
HK
hexokinase
-
HMP
hexose monophosphate shunt
-
6PG
6-phosphogluconate
-
PGM
phosphoglucomutase
Supported in part by: NSF grants DEB-76-19877 to D.A.P. and PCM 77-16838 to B.D.S., NIH Biomedical grant 5-50-7RR07-041 and a grant from the National Geographic Society. G.D.S. and R.V.B. are NIH trainees supported by a training grant (No. HD00139) to the Department of Biology, The Johns Hopkins University. This is contribution No. 1052 from the Department of Biology 相似文献
16.
Gabriella Dessole Danila Branca Federica Ferrigno Olaf Kinzel Ester Muraglia Maria Cecilia Palumbi Michael Rowley Sergio Serafini Christian Steinkühler Philip Jones 《Bioorganic & medicinal chemistry letters》2009,19(15):4191-4195
We report the synthesis and biological evaluation of N-[(1-aryl-1H-indazol-5-yl)methyl]amide derivatives as Smoothened antagonists and inhibitors of the Hedgehog pathway. Identification of the lead structure 1 by HTS, followed by SAR study on the amide and aryl portions led to the discovery of antagonists with nanomolar activity. 相似文献
17.
Reproductive character displacement and the genetics of gamete recognition in tropical sea urchins 总被引:8,自引:0,他引:8
Reproductive character displacement occurs when sympatric and allopatric populations of a species differ in traits crucial to reproduction, and it is commonly thought of as a signal of selection acting to limit hybridization. Most documented cases of reproductive character displacement involve characters that are poorly understood at the genetic level, and rejecting alternative hypotheses for biogeographic shifts in reproductive traits is often very difficult. In sea urchins, the gamete recognition protein bindin evolves under positive selection when species are broadly sympatric, suggesting character displacement may be operating in this system. We sampled sympatric and allopatric populations of two species in the sea urchin genus Echinometra for variation in bindin and for the mitochondrial cytochrome oxidase I to examine patterns of population differentiation and molecular evolution at a reproductive gene. We found a major shift in bindin alleles between central Pacific (allopatric) and western Pacific (sympatric) populations of E. oblonga. Allopatric populations of E. oblonga are polyphyletic with E. sp. C at bindin, whereas sympatric populations of the two species are reciprocally monophyletic. There is a strong signal of positive selection (P(N)/P(S) = 4.5) in the variable region of the first exon of bindin, which is associated with alleles found in sympatric populations of E. oblonga. These results indicate that there is a strong pattern of reproductive character displacement between E. oblonga and E. sp. C and that the divergence is driven by selection. There is much higher population structure in sympatric populations at the bindin locus than at the neutral mitochondrial locus, but this difference is not seen in allopatric populations. These data suggest a pattern of speciation driven by selection for local gamete coevolution as a result of interactions between sympatric species. Although this pattern is highly suggestive of speciation by reinforcement, further research into hybrid fitness and egg-sperm interactions is required to address this potential mechanism for character displacement. 相似文献
18.
Testing the utility of internally transcribed spacer sequences in coral phylogenetics 总被引:12,自引:0,他引:12
Reef-building corals often possess high levels of intraindividual and intraspecific ribosomal DNA (rDNA) variation that is largely polyphyletic between closely related species. Polyphyletic rDNA phylogenies coupled with high intraindividual rDNA variation have been taken as evidence of introgressive hybridization in corals. Interpreting the data is problematic because the rDNA cluster evolves in a complex fashion and polyphyletic lineages can be generated by a variety of processes--such as incomplete lineage sorting and slow concerted evolution--in addition to hybridization. Using the genetically characterized Caribbean Acropora hybridization system, we evaluate how well rDNA data perform in revealing patterns of recent introgressive hybridization in contrast to genetic data from four single-copy loci. While the rDNA data are broadly consistent with the unidirectional introgression seen in other loci, we show that the phylogenetic signature of recent introgressive hybridization is obscured in the Caribbean Acropora by ancient shared rDNA lineages that predate the divergence of the species. 相似文献
19.
The phylogenetic relationships of ten strongy-locentrotid sea urchin species were determined using mitochondrial DNA sequences. This phylogeny provides a backdrop for the evolutionary history of one of the most studied groups of sea urchins. Our phylogeny indicates that a major revision of this group is in order. All else remaining unchanged, it supports the inclusion of three additional species into the genus Strongylocentrotus (Hemicentrotus pulcherrimus, Allocentrotus fragilis, and Pseudocentrotus depressus). All were once thought to be closely related to this genus, but subsequent revisions separated them into other taxonomic groupings. Most strongylocentrotid species are the result of a recent burst of speciation in the North Pacific that resulted in an ecological diversification. There has been a steady reduction in the complexity of larval skeletons during the expansion of this group. Gamete attributes like egg size, on the other hand, are not correlated with phylogenetic position. In addition, our results indicate that the rate of replacement substitutions is highly variable among phylogenetic lineages. The branches leading to S. purpuratus and S. franciscanus were three to six times longer than those leading to closely related species. 相似文献
20.
Landry C Geyer LB Arakaki Y Uehara T Palumbi SR 《Proceedings. Biological sciences / The Royal Society》2003,270(1526):1839-1847
The rich species diversity of the marine Indo-West Pacific (IWP) has been explained largely on the basis of historical observation of large-scale diversity gradients. Careful study of divergence among closely related species can reveal important new information about the pace and mechanisms of their formation, and can illuminate the genesis of biogeographic patterns. Young species inhabiting the IWP include urchins of the genus Echinometra, which diverged over the past 1-5 Myr. Here, we report the most recent divergence of two cryptic species of Echinometra inhabiting this region. Mitochondrial cytochrome oxidase 1 (CO1) sequence data show that in Echinometra oblonga, species-level divergence in sperm morphology, gamete recognition proteins and gamete compatibility arose between central and western Pacific populations in the past 250 000 years. Divergence in sperm attachment proteins suggests rapid evolution of the fertilization system. Divergence of sperm morphology may be a common feature of free-spawning animals, and offers opportunities to simultaneously understand genetic divergence, changes in protein expression patterns and morphological evolution in traits directly related to reproductive isolation. 相似文献