Climatic niche shift of an invasive shrub (Ulex europaeus): a global scale comparison in native and introduced regions

Abstract

Aims Invasive species, which recently expanded, may help understand how climatic niche can shift at the time scale of the current global change. Here, we address the climatic niche shift of an invasive shrub (common gorse, Ulex europaeus) at the world and regional scales to assess how it could contribute to increasing invasibility. Methods Based on a 28 187 occurrences database, we used a combination of 9 species distribution models (SDM) to assess regional climatic niche from both the native range (Western Europe) and the introduced range in different parts of the world (North-West America, South America, North Europe, Australia and New Zealand). Important Findings Despite being restricted to annual mean temperature between 4°C and 22°C, as well as annual precipitation higher than 300 mm/year, the range of bioclimatic conditions suitable for gorse was very large. Based on a native versus introduced SDM comparison, we highlighted a niche expansion in North-West America, South America and to a lesser degree in Australia, while a niche displacement was assessed in North Europe. These niche changes induced an increase in potential occupied areas by gorse by 49, 111, 202 and 283% in Australia, North Europe, North-West America and South America, respectively. On the contrary, we found no evidence of niche change in New Zealand, which presents similar climatic condition to the native environment (Western Europe). This study highlights how niche expansion and displacement of gorse might increase invasibility at regional scale. The change in gorse niche toward new climatic conditions may result from adaptive plasticity or genetic evolution and may explain why it has such a high level of invasibility. Taking into account the possibility of a niche shift is crucial to improve invasive plants management and control.

The Invasive Niche, a Multidisciplinary Concept Illustrated by Gorse (<em>Ulex Europaeus</em>)

“…Hernández-Lambraño et al, 2016) and has shown that gorse is far from having filled its potential niche, confirming that its geographical expansion capacity is still important (Hill et al, 2008). We have extended this analysis of the bio-climatic niche to the global level, which allows us to estimate the level of adequacy of the local climate of all regions of the world with the ecological needs of gorse (Christina et al, 2019).…”

The Invasive Niche, a Multidisciplinary Concept Illustrated by Gorse (Ulex Europaeus)

“…To analyze the factors that may explain the value of this indicator, we identified and estimated a set of explanatory variables. The choice of the explanatory variables tested was based on our previous work on gorse, in biology [36,40], history [32,41], and sociology [29]. These variables had to be both relevant and available in a standardized way for all the countries studied.…”

“…At large geographical scales, climate is considered to act as the main filter of invasive species distribution [42,43]. To estimate the proportion of the country where the climate fulfills the requirements of gorse, we used the results of the global Species Distribution Model (SDM) of the bioclimatic niche of gorse designed by our team [36]. According to the literature, we retained the presence probability threshold calculated using the maximum likelihood [44].…”

“…A geographical variable, the latitude. We have retained this variable because in high latitudes (equatorial and tropical zones), gorse is present in mountains, while in temperate zones it is present at sea level [36,40]. Latitude is therefore a proxy for the kind of environment occupied by gorse (mountain or sea level).…”

“…As a consequence, a great deal of data is available not only in the scientific literature but also on a variety of other documents and websites. Its worldwide distribution, compiled from various sources, is available in Open Access [35], and its global bio-climatic niche was assessed by SDM modelling [36].…”