Non-random co-occurrence of native and exotic plant species in Mediterranean grasslands |
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| Institution: | 1. Complutense University of Madrid, Department of Ecology, Madrid, Spain;2. University of Talca, Faculty of Agricultural Sciences, Talca, Chile;3. Agricultural Research Institute INIA-La Cruz, La Cruz, Chile;4. Autónoma University of Madrid, Department of Ecology, Madrid, Spain;1. Laboratorio de Ecologia, CCBS, Universidade Federal do Mato Grosso do Sul, Campo Grande, MS 79070-900, Brazil;2. Departmento de Ecologia, Universidade Federal do Rio Grande do Norte, Natal, RN, 59078-900, Brazil;1. AgResearch Grasslands Research Centre, P.B. 11008, Palmerston North, New Zealand;2. Institute of Agriculture and Environment, Massey University, P.B. 11222, Palmerston North, New Zealand;3. School of Environmental Sciences, University of Guelph, Ontario, Canada N1G 2W1;1. Universidade Estadual da Paraíba – Laboratório de Ecologia de Bentos, Departamento de Biologia, Programa de Pós-Graduação em Ecologia e Conservação, Avenida das Baraúnas, 351, CEP 58429-500, Campina Grande, Brazil;2. MARE – Marine and Environmental Sciences Centre, Faculty of Sciences and Technology, University of Coimbra, 3004-517, Coimbra, Portugal;1. School of Nature Conservation, Beijing Forestry University, Beijing 100083, China;2. Zhejiang Provincial Key Laboratory of Plant Evolutionary Ecology and Conservation, Taizhou University, Taizhou 318000, China |
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| Abstract: | Invasion by exotic species in Mediterranean grasslands has determined assembly patterns of native and introduced species, knowledge of which provides information on the ecological processes underlying these novel communities. We considered grasslands from Spain and Chile. For each country we considered the whole grassland community and we split species into two subsets: in Chile, species were classified as natives or colonizers (i.e. exotics); in Spain, species were classified as exclusives (present in Spain but not in Chile) or colonizers (Spanish natives and exotics into Chile). We used null models and co-occurrence indices calculated in each country for each one of 15 sites distributed along a precipitation gradient and subjected to similar silvopastoral exploitation. We compared values of species co-occurrence between countries and between species subsets (natives/colonizers in Chile; exclusives/colonizers in Spain) within each country and we characterised them according to climatic variables. We hypothesized that: a) the different coexistence time of the species in both regions should give rise to communities presenting a spatial pattern further from random in Spain than in Chile, b) the co-occurrence patterns in the grasslands are affected by mesoclimatic factors in both regions. The patterns of co-occurrence are similar in Spain and Chile, mostly showing a spatial pattern more segregated than expected by random. The colonizer species are more segregated in Spain than in Chile, possibly determined by the longer residence time of the species in the source area than in the invaded one. The segregation of species in Chile is related to water availability, being species less segregated in habitat with greater water deficit; in Spain no relationship with climatic variables was found. After an invasion process, our results suggest that the possible process of alteration of the original Chilean communities has not prevented the assembly between the native and colonizer species together. |
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| Keywords: | Community organization Chile Herbaceous species Null models Spain Transcontinental naturalization |
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