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Global Survey (global + survey)
Selected AbstractsConifers as invasive aliens: a global survey and predictive frameworkDIVERSITY AND DISTRIBUTIONS, Issue 5-6 2004David M. Richardson ABSTRACT We summarize information on naturalized and invasive conifers (class Pinopsida) worldwide (data from 40 countries, some with remote states/territories), and contrast these findings with patterns for other gymnosperms (classes Cycadopsida, Gnetopsida and Ginkgoopsida) and for woody angiosperms. Eighty conifer taxa (79 species and one hybrid; 13% of species) are known to be naturalized, and 36 species (6%) are ,invasive'. This categorization is based on objective and conservative criteria relating to consistency of reproduction, distance of spread from founders, and degree of reliance on propagules from the founder population for persistence in areas well outside the natural range of species. Twenty-eight of the known invasive conifers belong to one family (Pinaceae) and 21 of these are in one genus (Pinus). The Cupressaceae (including Taxodiaceae) has six known invasive species (4%) in four genera, but the other four conifer families have none. There are also no known invasive species in classes Cycadopsida, Gnetopsida or Ginkgoopsida. No angiosperm family comprising predominantly trees and shrubs has proportionally as many invasive species as the Pinaceae. Besides the marked taxonomic bias in favour of Pinaceae, and Pinus in particular, invasiveness in conifers is associated with a syndrome of life-history traits: small seed mass (< 50 mg), short juvenile period (< 10 year), and short intervals between large seed crops. Cryptomeria japonica, Larix decidua, Picea sitchensis, Pinus contorta, Pinus strobus, and Pseudotsuga menziesii exemplify this syndrome. Many rare and endangered conifer species exhibit opposite characters. These results are consistent with earlier predictions made using a discriminant function derived from attributes of invasive and noninvasive Pinus species. Informative exceptions are species with small seeds (< 4 mg, e.g. Chamaecyparis spp., Pinus banksiana, Tsuga spp. , mostly limited to wet/mineral substrates) or otherwise ,non-invasive' characters (e.g. large seeds, fleshy fruits, e.g. Araucaria araucana, Pinus pinea, Taxus baccata that are dependent on vertebrates for seed dispersal). Most conifers do not require coevolved mutualists for pollination and seed dispersal. Also, many species can persist in small populations but have the genetic and reproductive capacity to colonize and increase population size rapidly. The underlying mechanisms mediating conifer invasions are thus easier to discern than is the case for most angiosperms. Further information is needed to determine the extent to which propagule pressure (widespread dissemination, abundant plantings, long history of cultivation) can compensate for low ,inherent invasiveness'. [source] Molecular epidemiology of clinical and environmental isolates of the Cryptococcus neoformans species complex reveals a high genetic diversity and the presence of the molecular type VGII mating type a in ColombiaFEMS YEAST RESEARCH, Issue 4 2006Patricia Escandón Abstract The aim of this study was to investigate the epidemiological relationships of clinical and environmental isolates of the Cryptococcus neoformans species complex in Colombia. The current study reflects data from 1987 to 2004. In Colombia serotypes A and B are most frequently recovered from patients and the environment. Of the 178 clinical isolates studied, 91.1% were of serotype A, 8.4% serotype B and 0.5% serotype C. Of the 247 environmental isolates, 44.2% were of serotype A, 42.6% serotype B and 13.2% serotype C. No serotype D isolates were isolated. Serotype AD has not been recovered in Colombia. PCR fingerprinting with the primers M13, (GACA)4 and (GTG)5 and URA5 gene restriction fragment length polymorphism analysis grouped the majority of clinical serotype A and environmental serotype B isolates into the molecular types VNI (98.1%) and VGII (100%), respectively. Mating type , was determined in 99.3% of serotype A isolates, but 96.6% of serotype B isolates were of mating type a. Similar profiles between clinical and environmental isolates suggest that the patients may have acquired the infection from the environment. The data presented form part of the Colombian contribution to the ongoing global survey of the C. neoformans species complex. [source] Connecting Atmosphere and Wetland: Energy and Water Vapour ExchangeGEOGRAPHY COMPASS (ELECTRONIC), Issue 4 2008Peter M. Lafleur Wetlands are ubiquitous over the globe, comprise a vast array of ecosystem types and are of great ecological and social importance. Their functioning is intimately tied to the atmosphere by the energy and mass exchanges that take place across the wetland,atmosphere boundary. This article examines recent research into these exchanges, with an emphasis on the water vapour exchange. Although broad classes of wetland type, such as fen, bog and marsh, can be defined using ecological or hydrologic metrics, distinct difference in energy exchanges between the classes cannot be found. This arises because there are many factors that control the energy exchanges and interplay of these factors is unique to every wetland ecosystem. Wetlands are more similar in their radiation balances than in the partitioning of this energy into conductive and turbulent heat fluxes. This is especially true of evapotranspiration (ET) rates, which vary considerably among and within wetland classes. A global survey of wetland ET studies shows that location has little to do with ET rates and that variation in rates is largely determined by local climate and wetland characteristics. Recent modelling studies suggest that although wetlands occupy a small portion of the global land surface, their water and energy exchanges may be important in regional and global climates. Although the number of studies of wetland,atmosphere interactions has increased in recent years more research is needed. Five key areas of study are identified: (i) the importance of moss covers, (ii) lack of study in tropical systems, (iii) inclusion of wetlands in global climate models, (iv) importance of microforms in wetlands and their scaling to the whole ecosystem, and (v) the paucity of annual ET measurements. [source] Selective acquisition of novel mating type and vegetative incompatibility genes via interspecies gene transfer in the globally invading eukaryote Ophiostoma novo-ulmiMOLECULAR ECOLOGY, Issue 1 2006MATHIEU PAOLETTI Abstract The Dutch elm disease fungus Ophiostoma novo-ulmi, which has destroyed billions of elm trees worldwide, originally invaded Europe as a series of clonal populations with a single mating type (MAT-2) and a single vegetative incompatibility (vic) type. The populations then rapidly became diverse with the appearance of the MAT-1 type and many vegetative incompatibility types. Here, we have investigated the mechanism using isolates from sites in Portugal at which the rapid evolution of O. novo-ulmi populations from clonality to heterogeneity was well established. We show by genetic mapping of vic and MAT loci with AFLP markers and by sequence analysis of MAT loci that this diversification was due to selective acquisition by O. novo-ulmi of the MAT-1 and vic loci from another species, Ophiostoma ulmi. A global survey showed that interspecies transfer of the MAT-1 locus occurred on many occasions as O. novo-ulmi spread across the world. We discuss the possibility that fixation of the MAT-1 and vic loci occurred in response to spread of deleterious viruses in the originally clonal populations. The process demonstrates the potential of interspecies gene transfer for facilitating rapid adaptation of invasive organisms to a new environment. [source] | ||||||||||