Micropropagation from inflorescence stems of the Spanish endemic plant Centaurea paui Loscos ex Willk. (Compositae)

Tissue culture techniques have been established as a useful approach for ex situ conservation of rare, endemic or threatened plant species. This report describes the micropropagation of Centaurea paui Loscos ex Willk (Compositae), an extremely endangered plant species endemic to the Valencia Community (eastern Spain), as a conservation measure which does not cause damage to the wild plants used as explant source. Inflorescence nodal segments of C. paui were selected as explants for in vitro establishment. The best rate of shoot proliferation was obtained on Murashige and Skoog (MS) mineral medium supplemented with 0.5 mg/l 6-benzyladenine or with 2 mg/l kinetin. Maximum shoot elongation was achieved without growth regulators, and the addition of cytokinins significantly decreased their size. In vitro rooting of shoots was difficult after 6 weeks on rooting media. The combination of 2 mg/l indole-3-acetic acid plus 2 mg/l indole-3-butyric acid on MS medium yielded the best results. In this medium, 40% of shoots rooted before 30 days of culture. About 70% of the rooted plants were successfully transferred to pots and acclimatized to ex vitro conditions. Received: 12 January 1998 / Revision received: 10 October 1998 / Accepted: 28 October 1998     

Global dynamics of a SEIR model with varying total population size

A SEIR model for the transmission of an infectious disease that spreads in a population through direct contact of the hosts is studied. The force of infection is of proportionate mixing type. A threshold sigma is identified which determines the outcome of the disease; if sigma < or = 1, the infected fraction of the population disappears so the disease dies out, while of sigma > 1, the infected fraction persists and a unique endemic equilibrium state is shown, under a mild restriction on the parameters, to be globally asymptotically stable in the interior of the feasible region. Two other threshold parameters sigma' and sigma are also identified; they determine the dynamics of the population sizes in the cases when the disease dies out and when it is endemic, respectively.     

Historical processes and environmental factors as determinants of inter-island differences in endemic faunas: the case of the Balearic Islands

Aim We describe current interisland similarities of endemic faunas, and elucidate the significance of historical factors and environmental ones in determining the pattern found. Location The six major islands of the Balearics (Western Mediterranean). Method An extensive review of all the endemic fauna ranging from platyhelminthes to mammals is made. From 568 presumed endemic species and subspecies, 230 full species with neither taxonomic nor distributional uncertainty are chosen. Inter-island similarities are determined using such a presence-absence matrix. Finally, relationships between the matrix of faunistic similarity and a number of matrices measuring environmental and historical factors are elucidated. Results Endemic fauna similarities depend clearly on historical factors. Dependence on environmental factors is unclear. Moreover, endemic fauna reveals two clear-cut clusters of islands within the Balearics: the Gymnesic Islands, in the NE, and the Pityusic Islands in the SW. Historical factors cluster the Balearic Islands in the same way. Contrasting, environmental variables show smoothed, no significant differences among the Gymnesics and the Pityusics. Main conclusions Pre-human flora (palynology) and fauna (bird and mammal fossil record) suggest that environmental differences among the Gymnesics and the Pityusics have now been reduced in comparison to the environmental differences at the Pleistocene and Holocene boundary. This environmental homogenization is likely related with human invasion. Historical effects of prehuman differences between Gymnesic and Pityusic Islands are still recognizable on endemic fauna. In contrast, there is no historical effects on interisland similarities using currently breeding birds (as an example of organisms well-dispersed and related to vegetation type). We explain the pattern of interisland similarities of endemic fauna as the result of the independent histories among the two islands groups. Contrasting, successive colonizations and extinctions would determine interisland similarities of breeding birds.     

雷州半岛15个阔叶树种混交幼林的生长分析*

通过15个阔叶树种2.5a生幼林在雷州半岛的生长比较,结果表明,树高、胸径和冠幅生长超过所有树种平均值的有水翁(Cleistocalyx operculatus)、盘架子(Winchia catophyua)、麻楝(Chukrasia tabularis)和秋枫(Bischofia javanica);按生长过程变化15个树种可分为3个类型:一是水翁、盘架子、秋枫和阴香(Cinnamomum burmanni),二是山楝(Aphanamixis polystachya)、麻楝、樟树(Cinnamomum camphora)、黎蒴栲(Castanopsis fissa)、火力楠(Michelia macdurei)、人面子(Dracontomelon duperreanum)、扁桃(Mangifera persiciformis)和榄仁树(Temninalia catappa),三是见血封喉(Antiaris toxicaria)、木棉(Bombax malabaricum)和无忧树(Saraca dives),不同类型的树种对生态位有不同要求,营造混交林应注意选择搭配。月平均温度、降雨量和相对湿度与多数种类的早期树高生长量与有较好的相关性,而与胸径和冠幅生长量的相关性则不明显。     

Endemism in the Flora of China—Studies on the Endemic Genera

China, under highly varied ecological conditions resulted from wide latitudinal and altitudinal ranges and from the adequate precipitation, has developed a very rich flora of great diversity. As far as flowering plants are concerned, there are 2980 genera, 214 of which, belonging to 64 families, are endemic. Among these endemic genera, there are 9 genera of taxads and conifers, 19 genera of monocots and others of dicots. Of the approximately 129 herbaceous endemic genera in the Chinese flora as a whole, about 22 (17%) are annual and 107 (83%) are biennial or perennial. In the present paper the ecological distribution, the nature of endemic genera and the centers of endemism are discussed. 1. Three types of endemic genera are distinguished, neoendemics, palaeoendemics and active epibiotics, The endemic genera in the flora of China are, for the most part, considered to be very old ones, and most of them are of temperate nature. 2. the degree of endemism in our 22 floristic regions is shown in Figure 1. The areas richest in endemic genera in the Chinese flora as a whole are the 13, 16 and 17 regions. The poorest are the 2, 4, 9 and 10 regions, and no one in the 1 and 3 regions These results on floristic richness are of general applicability. As shown in table 1, the difference in the degree of endemism among the seven Chinese floristic subkingdoms are most pronounced. 101 endemic genera are known to occur in one subkingdom, 72 to occur in two subkingdoms, and 3 to occur in four subkingdoms, only one genus widely distributed in five subkingdoms. However, there is no genus occurring in seven subkingdoms. The difference in the degree of endemism in each subkingdom reveals that the distribution of endemic genera is not well-distributed in the Chinese flora as a whole. Analysis of the vertical distribution of the 200 endemic genera of the Chinese flora bears out that there is no evident increase in endemism as a whole with altitude. 3. Three centers of endemism are found (Fig. 2). These are as follows: a). Eastern Sichuan-western Hubei center. b). Southeastern Yunnan-western Guangxi center. c). Western Sichuan-northwestern Yunnan center. The degree of endemism andcharacters of endemic genera in each center are discussed.     

Endemic origin and vast anthropogenic dispersal of the West Indian drywood termite

Cryptotermes brevis is a common pest of structural lumber and sheltered wood in much of the non-Asian tropics. Until now, no endemic locality, as confirmed by regenerating outdoor populations, was known. A termite survey of the northern coastal desert of Chile and the vicinity of Lima, Peru, yielded 61 outdoor populations of C. brevis taken from 23 different native and exotic species of host woods at 19 localities. We review the taxonomic and biogeographic history of C. brevis and suggest climatic and biological factors that favor or limit C. brevis distribution. We also propose a scenario implicating a post-Colombian release of C. brevis by shipboard infestations and the movement of infested wood during the early Spanish Empire to the present time.     

De novo assembly and characterization of transcriptome using Illumina sequencing and development of twenty five microsatellite markers for an endemic tree Juglans hopeiensis Hu in China

The Chinese walnut (Juglans hopeiensis Hu) is an endemic temperate tree species and narrowly distributed in China. However, there are still few specific molecular markers for understanding genetic diversity of this walnut. In this study, more than 44 million sequencing reads were generated using Illumina sequencing technology. De novo assembly yielded 93,822 unigenes with an average length of 731 bp. Based on sequence similarity search with known proteins, a total of 39,708 (42.3%) genes were identified. Searching against the Kyoto Encyclopedia of Genes and Genomes Pathway database (KEGG) indicated that 15,903 (17.0%) unigenes. To contribute to its conservation and management, twenty five microsatellite markers were identified in J. hopeiensis were screened for polymorphism across 27 Chinese walnut tree individuals from two locations. The number of alleles ranged from two to nine, observed heterozygosity ranged from 0.016 to 0.933 (mean 0.468), and expected heterozygosity from 0.022 to 0.823 (mean 0.462). The polymorphic information content (PIC) ranged from 0.012 to 0.831 (mean 0.437). The development of these new microsatellite markers will be useful for studying population genetic structure, evolutionary ecology, conservation, and genetic breeding of this endemic walnut tree or other Juglans species.     

Edaphic niches of metallophytes from southeastern Democratic Republic of Congo: Implications for post-mining restoration

In southeastern D. R. Congo, about 550 metallophytes grow on soils with high copper and cobalt concentrations, 57 of which are endemics to these metalliferous environments. About 70% of those endemics are considered threatened by destruction of habitats through mining activities. To provide guidelines for future restoration programs, the edaphic ecological niches of eight endemic metallophytes (i.e. copper endemics) were studied using a pragmatic sampling method adapted for urgent conservation needs. Niches were modelled using violin plot along Cu, Co and C:N gradients representing the two main independent edaphic gradients among nine edaphic variables (C, N, C:N, K, P, pH, Co, Cu, and Mn). Copper endemics presented distinct edaphic niches along the copper and cobalt gradients, but differentiation was lower along the C:N gradient. In addition, edaphic elements presented covariations among them and metalliferous soils had higher nutrient and element content compared to the non-metalliferous soils of the region dominated by the Miombo woodland. The complexity of the soil composition and the edaphic niches of copper endemics revealed an important challenge in the implementation of the species conservation and the habitat restoration strategies of post-mining sites.     

Dispersal and biogeography of silica-scaled chrysophytes

The silica-scaled chrysophytes—here mainly represented by the freshwater genera Mallomonas and Synura—have special problems in dispersal from one habitat to another because they cannot tolerate desiccation. Their dispersal is limited by the fragile construction and aquatic habit. Dispersal from one water body to another involves dangerous changes of the environment, and the ability to avoid desiccation during transport is crucial. So, air-borne and ectozoic dispersal by birds or mammals can only work at short distances. This danger may be avoided by endozoic dispersal of thick-walled cysts; as far as they can tolerate the digestion fluids in the intestine. In spite of these difficulties, Chrysophytes have been dispersed worldwide, but they display various distinct distribution patterns, e.g., cosmopolitan, arctic-northern temperate, bipolar, and tropical. Quite a large proportion may be considered endemic, occurring only within a restricted area. Even if the exact dispersal methods are elusive, the distribution of chrysophytes around the world proves their ability for dispersal. On the other hand, the different degree of distribution shows the varying success of the individual species. The distribution of a species at a given time depends on several factors: dispersal capacity—available vectors—suitable available habitats—and most important: sufficient time for dispersal. It is remarkable that the chrysophytes—in spite of their fragile cell construction and apparently low dispersal capacity—show distribution types comparable to those found in, e.g., blue–greens and desmids, whose cell construction appears much better adapted for dispersal. Special Issue: Protist diversity and geographic distribution. Guest editor: W. Foissner