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1.
John C. Semple 《Brittonia》1978,30(4):492-495
Analysis of the type collections ofChrysopsis hyssopifolia Nutt. (Compositae),C. gigantea Small andC. mixta Dress indicates that all three are conspecific. On the other hand, plants identified by all authors asC. hyssopifolia were found not to be conspecific. A new name is here proposed for these plants,C. Iinearifolia Semple. Two subspecies are recognized, subsp.linearifolia confined to west Florida and subsp.dressii Semple, primarily confined to central peninsular Florida.  相似文献   

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Three taxa of Caulerpa racemosa that differ morphologically and genetically have been reported in the Mediterranean Sea. The ‘invasive variety’ was recorded for the first time in the early 1990s in Libya. In less than 10 years, it was found in almost all parts of the Mediterranean. The first record of C. racemosa in the Croatian part of the Adriatic Sea was in 2000 and as many as 35 different localities were established by the end of 2004. In terms of morphology, the specimens from the Adriatic Sea resemble the ‘invasive variety’. To confirm this, we analysed populations from two different localities (the island of Mljet and the peninsula of Pelje?ac) using the ITS1-5.8S-ITS2 region of 18S-5.8S-26S rDNA unit as a molecular marker. The ITS1-5.8S-ITS2 region from nine individual plants was amplified by PCR, cloned in a pCR 2.1 vector and sequenced. Phylogenetic comparison of sequences from specimens found in the Adriatic Sea with specimens of the same and similar taxa, found both inside and outside the Mediterranean, provided genetic evidence that C. racemosa populating the Adriatic Sea corresponds to the Mediterranean C. racemosa var. cylindracea (Sonder) Verlaque, Huisman?&?Boudouresque, i.e. to the ‘invasive variety’.  相似文献   

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Scopelophila cataractae, one of the so-called copper mosses, has a broad geographic distribution that includes North, Central, and South America, Europe, and Asia, but is rare throughout its range. A genetic analysis of 32 populations from the United States, Europe, and Asia based on 15 putative allozyme loci indicates that levels of genetic diversity vary among geographic regions. Six European populations are fixed for the same alleles at all 15 loci, consistent with the hypothesis thatS. cataractae is a recent immigrant in that region. The species is more diverse in the U.S., where it appears to be native. Five populations collected on copper-enriched soils around shrines and temples in Tokyo are genetically monomorphic, but Asian populations from another Japanese site, India, and Nepal are exceptionally diverse in terms of numbers of alleles and multilocus haplotypes, total gene diversity (HT), and in the degree of differentiation among populations (measured as Nei'sI andD). Long-distance dispersal has probably played an important role in the geographic history ofS. cataractae, but the species appears to be native in both the New and Old Worlds. Gene flow between plants disjunct on different continents is insufficient to explain the lack of geographically correlated morphological and genetic differentiation inS. cataractae.  相似文献   

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Thecamoeba astrologa n. sp. was isolated from a plant litter sample. This species has a complex locomotive morphology, to a certain extent intermediate between the striate and the rugose morphotype. The shape of the actively moving cell is similar to that of striate thecamoebians, such as T. quadrilineata. However, in a slow movement, they can be easily confused with rugose species, like T. similis. Thecamoeba astrologa normally has peripheral asterisk-like nucleoli, which are unique among known thecamoebids. However, the structure of the nucleus is unusually variable during the growth of the culture and in some cases may become almost a vesicular one. The phylogenetic analysis based on the 18S rRNA gene sequence shows that this species belongs to the clade of thecamoebids, consisting of species possessing vesicular nuclei. This finding indicates that the structure of the nucleus derived from a single or few observations (as it usually happens in faunistic or ecological studies) may not be a reliable character of a thecamoebid amoeba. In some species nuclei may be highly polymorphic and dominating nuclear structure may depend on the age of the culture. Nuclei with constantly or temporarily peripheral nucleoli are now known in both major phylogenetic branches of the genus Thecamoeba.  相似文献   

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There is overwhelming empirical evidence for the influence of genetic factors in the etiology of schizophrenic psychoses. An appreciable and still increasing number of exogenous factors have been known for decades that are capable of inducing psychoses that present as "schizophrenia" or are more or less similar to it. In this article, genetic disorders--chromosomal abnormalities and Mendelian diseases--are summarized that may be associated with such psychoses. These disorders frequently but not necessarily exhibit additional physical symptoms. Although the majority of schizophrenic psychoses can so far not be explained by exogenous factors or well-defined genetic disorders, the proportion of these etiologies among all cases may be higher than presumed so far, because they evade detection. Data from the literature are discussed in the light of Karl Bonhoeffer's early concept of exogenous reaction types and modern medical genetics.  相似文献   

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Euptelea pleiospermum is an ??old rare?? tree species distributed along the high-elevation streamsides in Burma, China, and India. Deforestation and construction of roads for timber transport have highly fragmented the natural habitats of this species in the Shennongjia Forestry District. In this study, we used this fragmentation to test the hypothesis that ??old rare?? tree species are insusceptible to the genetic consequences of habitat fragmentation. Using eight microsatellite loci, we estimated allelic richness (A R), observed heterozygosity (H O), expected heterozygosity (H E), Wright??s inbreeding coefficient (F IS), and genetic differentiation (F ST and D EST) between pre- and post-fragmentation cohorts. We found no significant differences in either genetic diversity or genetic differentiation between the two cohorts. The limited genetic effects of fragmentation may result from too few fragmented generations, because the time between the start of fragmentation (year 1970) and our study (year 2008) was less than one generation of this tree species. It should be mentioned that clonal reproduction by sprouting, a common phenomenon in many ??old rare?? tree species, can help E. pleiospermum buffer the genetic impacts of fragmentation by delaying the time between generations. Therefore, we conclude that this ??old rare?? tree species show limited genetic impacts from recent habitat fragmentation. However, the elimination of rare alleles and increase of inbreeding coefficient in the post-fragmentation cohort are early warnings of deleterious genetic consequences of fragmentation. Our results provide valuable information to formulate conservation and restoration guidelines for E. pleiospermum.  相似文献   

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Alona brandorffi sp. n, related to A. verrucosa Sars, 1901 is described from Boa Vista, Brazil. Parthenogenetic females and males of A. brandorffi were studied. Examination of trunk limbs of A. brandorffi reveals several unusual modifications in structure, unique for the genus, such as very short setae on endites 2 and 3 of limb I, peculiar IDL setae, limb II with scrapers 7–8 with reduced distal part and only six, instead of seven setae in the filter plate, limb IV with only three, instead of four, setae on the inner lobe. The relationships and place of A. brandorffi within the genus Alona are discussed.  相似文献   

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Seven new species of Hypselostomatidae are described from the Chinese province Guangxi: Angustopila dominikae Páll-Gergely & Hunyadi, sp. n., Angustopila fabella Páll-Gergely & Hunyadi, sp. n., Angustopila subelevata Páll-Gergely & Hunyadi, sp. n., Angustopila szekeresi Páll-Gergely & Hunyadi, sp. n., Hypselostoma socialis Páll-Gergely & Hunyadi, sp. n., Hypselostoma lacrima Páll-Gergely & Hunyadi, sp. n. and Krobylos sinensis Páll-Gergely & Hunyadi, sp. n. The latter species is reported from three localities. All other new species are known only from the type locality. Specimens nearly identical to the type specimens of Angustopila huoyani Jochum, Slapnik & Páll-Gergely, 2014 were found in a cave in northern Guangxi, 500 km from the type locality. Adult individuals of Angustopila subelevata sp. n. (shell height = 0.83–0.91 mm, mean = 0.87 mm) and Angustopila dominikae sp. n. (shell height of the holotype = 0.86 mm) represent the smallest known members of the Hypselostomatidae, and thus are amongst the smallest land snails ever reported. We note that Pyramidula laosensis Saurin, 1953 might also belong to Krobylos. Paraboysidia neglecta van Benthem Jutting, 1961, which was previously included in Angustopila, is classified in Hypselostoma.  相似文献   

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In eight natural European populations of four closely related taxa of pines (Pinus sylvestris, P. mugo, P. uncinata, andP. uliginosa) starch-gel electrophoreses revealed altogether 58 alleles at 15 loci from nine enzyme systems. With Nei's genetic distance (D) the largest mean genetic distance (D = 0.171) was found betweenP. sylvestris andP. mugo, a distance corresponding to that between other closely related pine species. Mean genetic distances between the other taxa were less than half that value and characteristic for subspecies or varieties rather than for species. On the basis of our results we suggest that both,P. uliginosa andP. uncinata, could be the result of the ancient hybridization betweenP. sylvestris andP. mugo.  相似文献   

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Demographic data of genetic interest were studied in presently living population in comparison with preseding generations of Nganasans. Decrease of sex ratio in the whole population has been revealed along with the reduction of reproductive and, possibly, effective size. The number and variance of livebirths per female were 7.29 and 9.86 respectively. Crow' index of the opportunity for selection (I) and its components (Im and If) were estimated. I was found to be 1.17, whereas Im and If--1.56 and 0.18 respectively. Linear pattern of settling in the past as well as the type of migration between adjoining subpopulations depended on culture and economy of arctic reindeer hunters as well as landscape character.  相似文献   

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Media reporters often announce that we are on the verge of bringing back the woolly mammoth, even while there is growing consensus among scientists that resurrecting the mammoth is unlikely. In fact, current “de-extinction” efforts are not designed to bring back a mammoth, but rather adaptations of the mammoth using close relatives. For example, Harvard scientists are working on creating an Asian elephant with the thick coat of a mammoth by merging mammoth and elephant DNA. But how should such creatures be classified? Are they elephants, mammoths, or both? Answering these questions requires getting clear about the concept of reproduction. What I hope to show is that with an appropriate notion of reproduction—one for which I will argue—resurrecting a member of Mammuthus primigenius is a genuine possibility.  相似文献   

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By means of mitochondrial 12S rRNA sequencing of putative “yeti”, “bigfoot”, and other “anomalous primate” hair samples, a recent study concluded that two samples, presented as from the Himalayas, do not belong to an “anomalous primate”, but to an unknown, anomalous type of ursid. That is, that they match 12S rRNA sequences of a fossil Polar Bear (Ursus maritimus), but neither of modern Polar Bears, nor of Brown Bears (Ursus arctos), the closest relative of Polar Bears, and one that occurs today in the Himalayas. We have undertaken direct comparison of sequences; replication of the original comparative study; inference of phylogenetic relationships of the two samples with respect to those from all extant species of Ursidae (except for the Giant Panda, Ailuropoda melanoleuca) and two extinct Pleistocene species; and application of a non-tree-based population aggregation approach for species diagnosis and identification. Our results demonstrate that the very short fragment of the 12S rRNA gene sequenced by Sykes et al. is not sufficiently informative to support the hypotheses provided by these authors with respect to the taxonomic identity of the individuals from which these sequences were obtained. We have concluded that there is no reason to believe that the two samples came from anything other than Brown Bears. These analyses afforded an opportunity to test the monophyly of morphologically defined species and to comment on both their phylogenetic relationships and future efforts necessary to advance our understanding of ursid systematics.  相似文献   

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An analysis of the 524 nucleotide long segment in the 16SrDNA mitochondrial gene of Maurolicus japonicus revealed that there are two major haplotypes (E and H) and two minor haplotypes (I and J), which comprise 63·6, 27·2, 4·6 and 4·6% of the population, respectively. The nucleotide sequence of the major haplotype E is identical to that of the most common haplotype in Maurolicus walvisensis (63·6% of the population). The other haplotypes of M. japonicus are almost identical to that of the haplotype E with only a single (haplotypes I and J) or three nucleotide differences (haplotype H). Phylogenetic trees of all the 16SrDNA haplotypes found thus far in the Maurolicus taxa show that the relationships among the haplotypes of M. japonicus and M. walvisensis are indistinguishable but that they are clearly distinctive from those of Maurolicus muelleri . Examination of the morphometric characteristics of specimens reveals similarities among the individuals of different haplotypes of M. japonicus and also between M. japonicus and M. walvisensis in almost all characteristics. The results suggest that despite the current ocean-wide allopatric distribution between M. japonicus and M. walvisensis , the two taxa are conspecific as M. japonicus .  相似文献   

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