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Alien and native plant life-forms respond differently to human and climate pressures

Authors

  • Lorenzo Marini,

    Corresponding author
    1. Department of Environmental Agronomy and Crop Production, University of Padova, Viale dell'Università 16, 35020 Legnaro, Padova, Italy
      Lorenzo Marini, Department of Environmental Agronomy and Crop Production, University of Padova, Viale dell'Università 16, 35020 Legnaro, Padova, Italy. E-mail: lorenzo.marini@unipd.it
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  • Andrea Battisti,

    1. Department of Environmental Agronomy and Crop Production, University of Padova, Viale dell'Università 16, 35020 Legnaro, Padova, Italy
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  • Enzo Bona,

    1. Centro Studi Naturalistici Bresciani, c/o Museo Civico di Scienze Naturali, via Ozanam 4, 25128 Brescia, Italy
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  • Germano Federici,

    1. F.A.B. Gruppo Flora Alpina Bergamasca Via Crescenzi 82, 24123 Bergamo, Italy
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  • Fabrizio Martini,

    1. Department of Life Sciences, University of Trieste, via L. Giorgieri 10, 34127 Trieste, Italy
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  • Marco Pautasso,

    1. Department of Zoology, Cambridge University, Downing Street, Cambridge CB2 3EJ, UK
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  • Philip E. Hulme

    1. The Bio-Protection Research Centre, PO Box 84, Lincoln University, Canterbury, New Zealand
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Lorenzo Marini, Department of Environmental Agronomy and Crop Production, University of Padova, Viale dell'Università 16, 35020 Legnaro, Padova, Italy. E-mail: lorenzo.marini@unipd.it

ABSTRACT

Aim  To investigate whether differences in the elevational trend in native and alien species richness were dependent on climate or human pressures. Specifically we tested whether life-form and/or alien/native status modifies the response of plant species richness to human population and temperature along: (1) a complete elevational gradient, and (2) within separate elevational bands that, by keeping temperature within a narrow range, elucidate the effects of human pressures more clearly.

Location  Two provinces (c. 7507 km2) on the southern border of the European Alps (Italy), subdivided into 240 contiguous sampling cells (c. 35.7 km2).

Methods  We used an extensive dataset on alien and native species richness across an elevation gradient (20–2900 m a.s.l.). Richness of natives and naturalized aliens were separately related to temperature, human population and Raunkiaer life-form using general linear mixed models. Life-form describes different plant strategies for survival during seasons with adverse cold/arid conditions.

Results  The relationship between species richness and temperature for natives was strongly dependent on life-form, while aliens showed a consistent positive trend. Similar trends across alien and native life-forms were found for the relationship between species richness and human population along the whole gradient and within separate elevational bands.

Main conclusions  The absence of life-form-dependent responses amongst aliens supports the hypothesis that the distribution of alien plant species richness was more related to propagule pressure and availability of novel niches created by human activities than to climatic filtering. While climate change will potentially contribute to relaxing species thermal constraints, the response of alien species to future warming will also be contingent on changes in anthropogenic pressures.

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