Widespread resistance of Mediterranean island ecosystems to the establishment of three alien species |
| |
Authors: | Montserrat Vilà Akis-Stavros D Siamantziouras Giuseppe Brundu Ignazio Camarda Philip Lambdon Frédéric Médail Eva Moragues Carey M Suehs Anna Traveset reas Y Troumbis Philip E Hulme |
| |
Institution: | Estación Biológica de Doñana, Centro Superior de Investigaciones Científicas (EBD-CSIC), Avda/María Luisa s/n, Pabellón del Perú, 41013 Sevilla, Spain,;Biodiversity Conservation Laboratory, Department of Environment, University of the Aegean, GR-811 00 Mytilene, Greece,;Dipartimento di Botanica ed Ecologia vegetale, Universitàdegli Studi di Sassari, Sardinia, Italy,;NERC Centre for Ecology &Hydrology, Banchory, Kincardineshire, AB31 4BW UK,;Institut Méditerranéen d'Ecologie et de Paléoécologie (IMEP, UMR CNRS 6116), UniversitéPaul Cézanne/Aix-Marseille III, Europôle méditerranéen de l'Arbois, BP 80. F-13545 Aix-en-Provence cedex 04, France,;Institut Mediterrani d'Estudis Avançats (CSIC-UIB), University of the Balearic Islands, Miquel Marquès, 21, 07190 Esporles (Mallorca), Spain,;National Centre for Advanced Bio-Protection Technologies, PO Box 84, Lincoln University, Canterbury, New Zealand |
| |
Abstract: | Although some invasive plants are cosmopolitan, not all ecosystems are invaded to the same degree. Yet there is little experimental work on how ecosystem resistance to invasion at the establishment phase differs among ecosystems. We conducted two field sowing experiments in two consecutive years to examine establishment of the deciduous tree Ailanthus altissima, the succulent subshrub Carpobrotus spp. and the annual geophyte Oxalis pes‐caprae in coastal dunes, shrublands and oldfields in more than 200 sites across six Mediterranean Basin islands differing in climatic conditions and local species richness. Establishment success (i.e. percentage of plots with at least one seedling) and rates (i.e. seedling to sown seed ratio) were low, especially for Ailanthus even when accounting for differences in seed viability. Oxalis was capable of producing a new cohort of seedlings the year following planting. By contrast, all Ailanthus seedlings and half the Carpobrotus seedlings died following the first summer. Differences in establishment success and rates among ecosystems were species‐, island‐ and year‐dependent. Differences in precipitation and mean temperature were associated with differences in establishment rates across sites. Establishment rates tended to be positively correlated with cumulative precipitation and negatively with mean Ta. Unexpectedly, native species richness was not a good predictor of seedling establishment, except for higher Oxalis establishment success in species rich habitats. By conducting field sowing tests at multiple sites across a region we found that except for Oxalis, Mediterranean island ecosystems are quite resistant to invader establishment. These results suggest that differences in the degree of invasion between ecosystems and islands might be more dependent upon the influence of invasion event factors (e.g. propagule pressure) or factors acting at a later life‐history stages rather than differences in the resistance imposed by ecosystems to invader recruitment. Moreover, our results support the notion that in Mediterranean ecosystems invasions are highly idiosyncratic events and strongly dependent on water availability conditions. |
| |
Keywords: | Ailanthus altissima biological invasions Carpobrotus spp invasibility Oxalis pes-caprae plant invader species richness |
|
|