Climatic niche conservatism in non‐native plants is largely dependent on their climatic niche breadth in the native range

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Abstract
Confidence in predictions of non‐native species' spread relies on the niche conservatism hypothesis, which poses that climatic niches are preserved over time and space. Because plants introduced through the same introduction pathway (gardening, unintentional) tend to share some features of the introduction process and biological attributes, the extent of niche conservatism might be influenced by how and when species of particular attributes have been introduced. We compared the realized climatic niches between the native (global) and invaded ranges (mainland Spain), through ordination and kernel smoothers. We calculated niche conservatism metrics (i.e. overlap, unfilling, stability, expansion and pioneering), for a set of 158 plant species. Niche conservatism metrics were then related to a plant's introduction pathway, minimum residence time, growth form and native climatic niche breadth. On average, niche stability accounted for 75% of niche occupancy, while around 61% of species showed some degree of niche shift, which were mostly of small magnitude. The climatic niche was most conserved for annual and perennial herbs, plants introduced a long time ago, and those with broad climatic niches in their native range. Introduction pathways had a non‐significant effect. Niche conservatism metrics were neither explained by interactions of minimum residence time with introduction pathways nor with growth form. Native climatic niche breadth was the most important correlate of niche conservatism metrics. Synthesis. Non‐native plants largely occupy similar climatic conditions in their invaded and native range, a pattern that co‐occurred with frequent and mostly small niche shifts. These results largely support the niche conservatism hypothesis. This boosts confidence in predictive models of non‐native plants' spread. This study highlights that niche conservatism is better explained by a plant's ability to cope with broad climatic conditions, rather than by its introduction history or growth form.
Funding Information
  • Ministerio de Ciencia, Innovación y Universidades (CEX‐2018‐000828‐S, EST21/00611, FPU18/05806, PID2021‐122690OB‐I00)
  • Generalitat de Catalunya

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