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171.
Fern gametophytes and young sporophytes often provide too little material for DNA extraction and are particularly difficult to identify to genus. Here we developed an efficient procedure called 'Tissue-direct PCR', in which a slice of fern tissue is mixed with PCR reagents and primers, allowing certain genomic regions to be amplified directly in the thermal cycler. For these diminutive and featureless stages of ferns, Tissue-direct PCR combined with amplifying plant barcodes promises to make the identification of immature ferns easy and rapid. Tissue-direct PCR would also be very helpful for large-scale ecological studies surveying distribution and population structure.  相似文献   
172.
Abstract. A first classification for serpentine annual grasslands distributed throughout northern and central California is proposed. This study has followed the Braun‐Blanquet phyto‐sociological system based on floristical, biogeographical and bioclimatic features of the sampled areas. Numerical analyses of classification and ordination were applied to the floristic relevés. Minimum Variance Clustering grouped relevés into basic classification units that allowed us to define low‐hierarchical syntaxonomical units (associations) and ‘communities’. A Principal Coordinate Analysis was used to extract those ecological parameters related to the axes that separate those classification units from the previous dendrogram. The results showed that differences in species composition was mainly due to a continentality gradient and the shady effect of an overstory vegetation. On the basis of both analyses we propose a first syntaxonomic scheme on ultramafic (mainly serpentine) annual plant communities of the biogeographical Californian Region that comprises four associations, two subassociations and some provisional communities.  相似文献   
173.
John T. Mickel 《Brittonia》2001,53(4):487-489
Elaphoglossum trichomidiatum is described from northeastern Mexico. The new species is a member of theE. petiolatum comples, which is widespread in tropical America, Africa, Southeast Asia, and the Pacific Islands. It is unique in the complex and in sectionLepidoglossa in bearing trichomidia on the abaxial blade surface.  相似文献   
174.
The evolutionary history of phytophagous insects and mites and of their food-plants is traced in the conservative preferences of modern-day insects for plants. Based on UK data in the Phytophagous Insects Data Bank, a correspondence analysis displays 182 insect families and 117 plant families in a bi-variate plot. The overall pattern suggests the expansion of diversity of insects and host plants from Gymnosperms to Dicots. Plots for phytophagous insect orders and major plant clades are described, with families provisionally ranked as evolutionarily basal, intermediate or advanced. There are blurred patterns of evolutionary advancement from basal insect families with more species on conifers and on ferns and Eurosid I trees. Intermediate families are commoner on Malpighiales and Fabales, and advanced insects more frequent on later evolved euasterids II (Asterales and Lamiales), Caryophyllales and Gramineae. Basal Hymenoptera have associations with conifers, basal Lepidoptera to Eurosid I trees, and Diptera are mainly advanced families on commelinids (grasses) and Asteraceae. Blurred traces of similar phylogenetic sequences are described for subfamilies within eight example insect families. Basal families and clades tend to have fewer species than derived advanced clades. Insect communities on plants should be seen in the light of this linked past evolutionary background.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 78 , 51–83.  相似文献   
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Most montane rain forests on the island of Hawaii consist of a closed canopy formed by Cibotium spp. tree ferns beneath an open canopy of emergent Metrosideros polymorpha trees. We used artificial seedlings to assess the extent to which physical disturbance caused by the senescing fronds of tree ferns and the activities of feral pigs might limit tree regeneration. Artificial seedlings were established terrestrially (N= 300) or epiphytically (N = 300) on tree fern stems. Half of the seedlings on each substrate were in an exclosure lacking feral pigs and half were in forest with pigs present. After one year, the percentage of seedlings damaged was significantly greater among terrestrial seedlings (25.7%) than epiphytic seedlings (11.3%). Significantly more terrestrial seedlings were damaged in the presence of pigs (31.3%) than in the absence of pigs (20.0%). Senescing fronds of tree ferns were responsible for 60.3 percent of the damaged seedlings. Physical disturbance is potentially a major cause of seedling mortality and may reduce the expected half‐life of a seedling cohort to less than two years.  相似文献   
179.
The study of abundant permineralized fern remains collected in the Oligocene Rancahué Formation (Neuquén Province, Argentina) allowed the identification of two different taxa. The name Cuyenopteris patagoniensis nov. gen., nov. sp. is proposed for several stems and fronds characterized by the presence of caulinar dictyosteles with root gaps, producing C-shaped leaf traces composed by two hippocampiform bundles flanked by eight to ten small round bundles, half of them diverging from cauline meristeles and the rest from the hippocampiform bundles. The presence of these features, along with frond bases with adaxial grooves and a pair of pneumatophores, suggest affinities with the Blechnaceae or Dryopteridaceae. The second identified taxon is Alsophilocaulis calveloi Menéndez. Based on features observed in these new materials, including characteristics of the mantle of adventitious roots and anatomy of the petiole bases, an emended diagnosis for this latter species is proposed.  相似文献   
180.
Abstract. Succession, changes in the distribution pattern of forest vegetation, and Pinus forest survival following pine wilt disease were clarified based on phytosociological analysis and vegetation maps. Survival of Pinus forests was restricted to the early successional stages, which were located on ridges and the upper part of slopes. Subsequent to pine wilt disease, the succession progressed from early to late substages of Pinus forest, mixed deciduous and evergreen Quercus, to evergreen Quercus forest. Succession occurs in abandoned pine forests which apparently are in a bad state and are vulnerable to attacks by pine wilt disease.  相似文献   
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