Comparing naturalized alien plants and recipient habitats across an east-west gradient in the Mediterranean Basin

Arianoutsou M., Delipetrou P., Celesti-Grapow L., Basnou C., Bazos I., Kokkoris Y., Blasi C., Vilà M. (2010) Comparing naturalized alien plants and recipient habitats across an east-west gradient in the Mediterranean Basin. Journal of Biogeography. 37: 1811-1823.
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Doi: 10.1111/j.1365-2699.2010.02324.x

Resum:

Aim: To investigate alien plant species invasion levels in different habitats and alien species traits by comparing the naturalized flora in different areas of the same biogeographical region. Location: Spain, Italy, Greece and Cyprus. Methods: Comparison of floristic composition, species traits and recipient habitats of naturalized alien neophytes across an east-west gradient comprising four countries in the European Mediterranean basin. Results: A total of 782 naturalized neophytes were recorded; only 30 species were present in all four countries. Although floristic similarity is low, the four alien floras share the same patterns of growth form (mostly herbs), life cycle (mostly perennials) and life form (mostly therophytes, hemicryptophytes and phanerophytes). The majority of the recipient habitats were artificial. Wetlands were the natural habitats, with the highest numbers of naturalized species. Floristic similarity analyses revealed: (1) the highest floristic similarity between Italy and Spain, both of which were more similar to Greece than to Cyprus; (2) two groups of floristic similarity between habitat categories in each country (Greece-Cyprus and Italy-Spain); (3) a higher degree of homogenization in the plant assemblages in different habitats in Greece and Cyprus and a lower degree of homogenization in those in Italy and Spain; and (4) a higher degree of homogenization in artificial and natural fresh-water habitats than in the other natural habitats. Main conclusions: The floristic similarity of naturalized neophytes between the four countries is low, although the overall analysis indicates that the western group (Italy-Spain) is separated from the eastern group (Greece-Cyprus). Similar patterns emerged regarding the life-history traits and recipient habitats. The artificial habitats and the natural wet habitats are those that are invaded most and display the greatest homogenization in all four countries. Coastal habitats display a lower degree of homogenization but a high frequency of aliens. Dry shrubs and rocky habitats display a lower degree of homogenization and a low frequency of aliens. © 2010 Blackwell Publishing Ltd.

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Predicting plant invaders in the Mediterranean through a weed risk assessment system

Gassó N., Basnou C., Vilà M. (2010) Predicting plant invaders in the Mediterranean through a weed risk assessment system. Biological Invasions. 12: 463-476.
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Doi: 10.1007/s10530-009-9451-2

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Risk assessment schemes have been developed to identify potential invasive species, prevent their spread and reduce their damaging effects. One of the most promising tools for detecting plant invaders is the weed risk assessment (WRA) scheme developed for Australia. Our study explores whether the Australian WRA can satisfactorily predict the invasion status of alien plants in the Mediterranean Basin by screening 100 invasive and 97 casual species in Spain. Furthermore, we analysed whether the factors taken into account in the WRA are linked to invasion likelihood (i.e., invasion status) or to impacts. The outcome was that 94% of the invasive species were rejected, 50% of the casual species were rejected and 29% of them required further evaluation. The accuracy for casuals is lower than in other studies that have tested non-invasive (i.e., casuals or non-escaped) alien species. We postulate that low accuracy for casual species could result from: (1) an incorrect "a priori" expert classification of the species status, (2) a high weight of the WRA scores given to potential impacts, and (3) casual species being prone to becoming invasive when reaching a minimum residence time threshold. Therefore, the WRA could be working as a precaution early-warning system to identify casual species with potential to become invasive. © 2009 Springer Science+Business Media B.V.

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How well do we understand the impacts of alien species on ecosystem services? A pan-European, cross-taxa assessment

Vilà M., Basnou C., Pyšek P., Josefsson M., Genovesi P., Gollasch S., Nentwig W., Olenin S., Roques A., Roy D., Hulme P.E. (2010) How well do we understand the impacts of alien species on ecosystem services? A pan-European, cross-taxa assessment. Frontiers in Ecology and the Environment. 8: 135-144.
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Doi: 10.1890/080083

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Recent comprehensive data provided through the DAISIE project (www.europe-aliens.org) have facilitated the development of the first pan-European assessment of the impacts of alien plants, vertebrates, and invertebrates in terrestrial, freshwater, and marine environments - on ecosystem services. There are 1094 species with documented ecological impacts and 1347 with economic impacts. The two taxonomic groups with the most species causing impacts are terrestrial invertebrates and terrestrial plants. The North Sea is the maritime region that suffers the most impacts. Across taxa and regions, ecological and economic impacts are highly correlated. Terrestrial invertebrates create greater economic impacts than ecological impacts, while the reverse is true for terrestrial plants. Alien species from all taxonomie groups affect "supporting", "provisioning", "regulating", and "cultural" services and interfere with human well-being. Terrestrial vertebrates are responsible for the greatest range of impacts, and these are widely distributed across Europe. Here, we present a review of the financial costs, as the first step toward calculating an estimate of the economic consequences of alien species in Europe. © The Ecological Society of America.

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