Home About us Contact
|
Home About us Contact | ||
|
|
||
Initial Invasion (initial + invasion)
Selected AbstractsCOEVOLUTION DRIVES TEMPORAL CHANGES IN FITNESS AND DIVERSITY ACROSS ENVIRONMENTS IN A BACTERIA,BACTERIOPHAGE INTERACTIONEVOLUTION, Issue 8 2008Samantha E. Forde Coevolutionary interactions are thought to play a crucial role in diversification of hosts and parasitoids. Furthermore, resource availability has been shown to be a fundamental driver of species diversity. Yet, we still do not have a clear understanding of how resource availability mediates the diversity generated by coevolution between hosts and parasitoids over time. We used experiments with bacteria and bacteriophage to test how resources affect variation in the competitive ability of resistant hosts and temporal patterns of diversity in the host and parasitoid as a result of antagonistic coevolution. Bacteria and bacteriophage coevolved for over 150 bacterial generations under high and low-resource conditions. We measured relative competitive ability of the resistant hosts and phenotypic diversity of hosts and parasitoids after the initial invasion of resistant mutants and again at the end of the experiment. Variation in relative competitive ability of the hosts was both time- and environment-dependent. The diversity of resistant hosts, and the abundance of host-range mutants attacking these phenotypes, differed among environments and changed over time, but the direction of these changes differed between the host and parasitoid. Our results demonstrate that patterns of fitness and diversity resulting from coevolutionary interactions can be highly dynamic. [source] Will climate change be beneficial or detrimental to the invasive swede midge in North America?GLOBAL CHANGE BIOLOGY, Issue 8 2008Contrasting predictions using climate projections from different general circulation models Abstract Climate change may dramatically affect the distribution and abundance of organisms. With the world's population size expected to increase significantly during the next 100 years, we need to know how climate change might impact our food production systems. In particular, we need estimates of how future climate might alter the distribution of agricultural pests. We used the climate projections from two general circulation models (GCMs) of global climate, the Canadian Centre for Climate Modelling and Analysis GCM (CGCM2) and the Hadley Centre model (HadCM3), for the A2 and B2 scenarios from the Special Report on Emissions Scenarios in conjunction with a previously published bioclimatic envelope model (BEM) to predict the potential changes in distribution and abundance of the swede midge, Contarinia nasturtii, in North America. The BEM in conjunction with either GCM predicted that C. nasturtii would spread from its current initial invasion in southern Ontario and northwestern New York State into the Canadian prairies, northern Canada, and midwestern United States, but the magnitude of risk depended strongly on the GCM and the scenario used. When the CGCM2 projections were used, the BEM predicted an extensive shift in the location of the midges' climatic envelope through most of Ontario, Quebec, and the maritime and prairie provinces by the 2080s. In the United States, C. nasturtii was predicted to spread to all the Great Lake states, into midwestern states as far south as Colorado, and west into Washington State. When the HadCM3 was applied, southern Ontario, Saskatchewan, and Washington State were not as favourable for C. nasturtii by the 2080s. Indeed, when used with the HadCM3 climate projections, the BEM predicted the virtual disappearance of ,very favourable' regions for C. nasturtii. The CGCM2 projections generally caused the BEM to predict a small increase in the mean number of midge generations throughout the course of the century, whereas, the HadCM3 projections resulted in roughly the same mean number of generations but decreased variance. Predictions of the likely potential of C. nasturtii spatial spread are thus strongly dependent on the source of climate projections. This study illustrates the importance of using multiple GCMs in combination with multiple scenarios when studying the potential for spatial spread of an organism in response to climate change. [source] Expression of plasminogen activator inhibitor-1, urokinase receptor and laminin ,-2 chain is an early coordinated event in incipient oral squamous cell carcinomaINTERNATIONAL JOURNAL OF CANCER, Issue 12 2006Pia Lindberg Abstract Cancer cell invasion is facilitated by extracellular matrix degrading proteases such as plasmin. We have studied the expression of plasminogen activator inhibitor-1 (PAI-1) and urokinase receptor (uPAR) together with the ,2-chain of laminin-5 (lam-,2) by immunohistochemistry in 20 cases with incipient oral squamous cell carcinoma (SCC). PAI-1-positive neoplastic cells located at the tip of the putative invasive front of grade 1 (incipient) carcinoma were seen in 16 of the 20 cases (75%), whereas adjacent normal and dysplastic epithelium was PAI-1-negative. Clusters of putative invasive neoplastic cells located in the lamina propria were PAI-1-positive in areas with grade 2 incipient carcinoma as were invasive cancer cells in areas of grade 3,4 invasive carcinoma. uPAR immunoreactivity was strongly expressed in numerous stromal cells in the carcinoma area in all 20 lesions, while a few uPAR-positive stromal cells were found in areas with normal and dysplastic epithelium. uPAR-positive neoplastic cell islands located at the front of the lesions were seen in 15 of the 20 cases. The expression pattern of lam-,2 was very similar to that of PAI-1; however, lam-,2-positive neoplastic cells were only detected in 11 of the 20 cases (55%) in areas of grade 1 incipient carcinoma. Direct comparison of the 3 components revealed colocalization in neoplastic cell islands in both incipient and invasive SCC. Our results suggest that PAI-1 is a novel potential marker of initial invasion in oral SCC, and that the coordinated expression of PAI-1 with uPAR and lam-,2 sustain the features of the early invasive cancer cells. © 2006 Wiley-Liss, Inc. [source] Gut passage effect of the introduced red-whiskered bulbul (Pycnonotus jocosus) on germination of invasive plant species in MauritiusAUSTRAL ECOLOGY, Issue 3 2009JANNIE F. LINNEBJERG Abstract In Mauritius, many of the worst invasive plant species have fleshy fruits and rely on animals for dispersal. The introduced red-whiskered bulbul (Pycnonotus jocosus) feeds on many fleshy-fruited species, and often moves from invaded and degraded habitats into higher quality native forests, thus potentially acting as a mediator of continued plant invasion into these areas. Furthermore, gut passage may influence seed germination. To investigate this, we fed fleshy fruits of two invasive plant species, Ligustrum robustum and Clidemia hirta, to red-whiskered bulbuls. Gut passage times of seeds were recorded. Gut-passed seeds were sown and their germination rate and germination success compared with that of hand-cleaned seeds, as well as that of seeds in whole fruits. Gut passage and hand-cleaning had significant positive effects on germination of both species. Gut-passed seeds of both C. hirta and L. robustum germinated faster than hand-cleaned seeds. However, for L. robustum, this was only true when compared with hand-cleaned seeds with intact endocarp; when compared with hand-cleaned seeds without endocarp, there was no difference. For overall germination success, there was a positive effect of gut passage for C. hirta, but not for L. robustum. For both C. hirta and L. robustum, no seeds in intact fruits geminated, suggesting that removal of pulp is essential for germination. Our results suggest that, first, the initial invasion of native forests in Mauritius may not have happened so rapidly without efficient avian seed dispersers like the red-whiskered bulbul. Second, the bulbul is likely to be a major factor in the continued re-invasion of C. hirta and L. robustum into weeded and restored conservation management areas. [source] | ||||||||||