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Multiple Invasions (multiple + invasion)
Selected AbstractsMultiple invasions of Errantivirus in the genus DrosophilaINSECT MOLECULAR BIOLOGY, Issue 2 2008A. Ludwig Abstract Aiming to contribute to the knowledge of the evolutionary history of Errantivirus, a phylogenetic analysis of the env gene sequences of Errantivirus gypsy, gtwin, gypsy2, gypsy3, gypsy4 and gypsy6 was carried out in 33 Drosophilidae species. Most sequences were obtained from in silico searches in the Drosophila genomes. The complex evolutionary pattern reported by other authors for the gypsy retroelement was also observed in the present study, including vertical transmission, ancestral polymorphism, stochastic loss and horizontal transfer. Moreover, the elements gypsy2, gypsy3, gypsy4 and gypsy6 were shown to have followed an evolutionary model that is similar to gypsy. Fifteen new possible cases of horizontal transfer were suggested. The infectious potential of these elements may help elucidate the evolutionary scenario described in the present study. [source] BIOGEOGRAPHY OF MARINE RED ALGAE: MYTHS AND REALITIESJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Hommersand, M. H. Department of Biology, Coker Hall, University of North Carolina, Chapel Hill, NC 27599-3280 USA Theories about the geographical distribution of marine algae fall roughly into two categories: (1) a concept of biogeographical regions in which algal distribution is determined primarily by growth, reproductive and lethal temperature boundaries (Setchell, van den Hoek, Breeman, Lüning) and (2) an historical perspective in which distribution is determined primarily by patterns of dispersal and the establishment of barriers to dispersal (vicariance biogeography) (Svedelius, Garbary, Lindstrom, Hommersand). Setchell proposed the 5° isotherm rule in 1920, and in 1924 Svedelius advocated a worldwide distribution for tropical and subtropical groups followed by discontinuous distribution upon closure of the connection between the Indian Ocean and Mediterranean Sea and, later, between North and South America (Wegener's theory). Transarctic dispersal routes have received special attention in recent years (Lindstrom, Lüning, van Oppen, Olsen, Stam), as have special relationships between Australasia, South Africa and South America (Hommersand). Less well understood are the climatic changes that have taken place in the Cenozoic which are strategic to an understanding vicariant biogeography. The advent of molecular methods combined with the tools of phylogenetic systematics now make it possible to identify ancestral taxa, test the consistency of tree topologies, and calculate mean branch lengths between sister lineages diverging from an interior node of a tree. With such methods it may be possible to infer ancestral areas, identify dispersal pathways, determine the chronology of isolating events, assess the impact of multiple invasions, and generally relate dispersal and vicariance models to phylogenetic hypotheses for red, brown and green algal taxa. [source] Contrasting patterns in genetic diversity following multiple invasions of fresh and brackish watersMOLECULAR ECOLOGY, Issue 12 2006DAVID W. KELLY Abstract Biological invasions may combine the genetic effects of population bottlenecks and selection and thus provide valuable insight into the role of such processes during novel environmental colonizations. However, these processes are also influenced by multiple invasions, the number of individuals introduced and the degree of similarity between source and receiving habitats. The amphipod Gammarus tigrinus provides a useful model to assess these factors, as its invasion history has involved major environmental transitions. This species is native to the northwest Atlantic Ocean, although it invaded both brackish and freshwater habitats in the British Isles after introduction more than 65 years ago. It has also spread to similar habitats in Western Europe and, most recently, to Eastern Europe, the Baltic Sea, and the Laurentian Great Lakes. To examine sources of invasion and patterns of genetic change, we sampled populations from 13 native estuaries and 19 invaded sites and sequenced 542 bp of the mitochondrial COI gene. Strong native phylogeographical structure allowed us to unambiguously identify three allopatrically evolved clades (2.3,3.1% divergent) in invading populations, indicative of multiple introductions. The most divergent clades occurred in the British Isles and mainland Europe and were sourced from the St Lawrence and Chesapeake/Delaware Bay estuaries. A third clade was found in the Great Lakes and sourced to the Hudson River estuary. Despite extensive sampling, G. tigrinus did not occur in freshwater at putative source sites. Some European populations showed reduced genetic diversity consistent with bottlenecks, although selection effects cannot be excluded. The habitat distribution of clades in Europe was congruent with the known invasion history of secondary spread from the British Isles. Differences in salinity tolerance among lineages were suggested by patterns of habitat colonization by different native COI clades. Populations consisting of admixtures of the two invading clades were found principally at recently invaded fresh and brackish water sites in Eastern Europe, and were characterized by higher genetic diversity than putative source populations. Further studies are required to determine if these represent novel genotypes. Our results confirm that biological invasions need not result in diminished genetic diversity, particularly if multiple source populations, each with distinctive genetic composition, contribute to the founding populations. [source] Incidence of cereal and pasture viruses in New Zealand's native grassesANNALS OF APPLIED BIOLOGY, Issue 1 2010C. Delmiglio This study provides evidence for frequent and multiple invasions of New Zealand's native grasses by exotic cereal and pasture viruses. Fifteen native and three exotic grasses from 29 North Island and six South Island sites were surveyed for the presence of viruses using enzyme-linked immunosorbent assay (ELISA). Barley yellow dwarf virus and Cereal yellow dwarf virus (BYDV, CYDV: Luteoviridae) and Cocksfoot mottle virus (CoMV, Sobemovirus) are widespread throughout New Zealand. CoMV, previously considered to have a natural host range restricted to Dactylis and Triticum, was detected in Poa anceps, P. cita, Festuca novae-zelandiae, and Chionochloa rubra. New virus host reports include BYDV-PAV in Microlaena stipoides and Dichelachne crinita; BYDV-MAV in P. cita, F. novae-zelandiae and Hierochloe redolens; and CYDV-RPV in P. cita and M. stipoides. Nominal logistic regression analyses showed a correlation between the presence of exotic grass species and virus incidence. Host range experiments for BYDV-PAV and CoMV were performed with selected native and exotic grasses, and the results are discussed in context of the field-survey findings. [source] | ||||||||||