Abstract
AbstractAimHere, we aim to: (a) investigate the local effect of environmental and anthropogenic factors on alien plant invasion in sub‐Antarctic islands; and (b) explore whether and how functional traits affect alien species dependence on anthropogenic factors in these environments.LocationPossession Island, Crozet archipelago (French sub‐Antarctic islands).MethodsSingle‐species distribution models were used to explore the effect of high‐resolution topoclimatic and human‐related variables on the occurrence of six alien plants colonizing French sub‐Antarctic islands. Furthermore, plant responses to human‐related variables and the effect of those variables in interaction with plant traits were analysed by means of a multi‐species distribution model. This allowed identifying functional features mediating the influence of human activities on the occurrence probability of alien plant species.ResultsWe observed two main invasion patterns: (a) species predicted to occur close to the introduction sites, whose occurrence probability appeared to be strongly affected by anthropogenic factors; and (b) species predicted to occur nearly everywhere on Possession Island, except in areas featuring particularly harsh climatic conditions. Differences in the influence of human‐related variables on the occurrence of the alien species were mostly related to their life history, plant height and residence time, with perennial and low‐statured species introduced earlier appearing less dependent on human‐induced dispersal and disturbance.ConclusionsWe conclude that both topoclimatic and anthropogenic factors affect plant invasion on sub‐Antarctic islands. Specifically, species predicted to occur close to their introduction sites appear much more dependent on human presence and activity, potentially due to the lack of key functional traits allowing them to spread successfully across Possession Island under the harsh sub‐Antarctic climate. Yet, particularly severe abiotic conditions are a major constraint which equally limits the occurrence of all alien plants, irrespective of their dependence on anthropogenic factors.
Highlights
Sub-Antarctic islands, archipelagos scattered within the 54-48°S latitudinal ring, are extremely remote territories which harbour a unique biodiversity with a high degree of endemism (Shaw, 2013)
We model the distribution of the most relevant alien plant species colonizing Possession Island using a combination of environmental and human-related spatial data derived at an unprecedented high spatial resolution (i.e. 30-m) for these latitudes that we related to long-term monitoring observations of plant occurrences
The occurrence probability of J. bufonius, S. procumbens and C. fontanum peaked at mean temperature values around 4.5 °C, while the presence of P. pratensis and P. annua increased more or less linearly with temperature
Summary
Sub-Antarctic islands, archipelagos scattered within the 54-48°S latitudinal ring, are extremely remote territories which harbour a unique biodiversity with a high degree of endemism (Shaw, 2013). Later on and since the mid-twentieth century, climate warming, strong changes in precipitation regimes and the widespread impacts of non-native vertebrates have progressively favoured the establishment of cold tolerant alien plants on sub-Antarctic islands (Shaw, 2013; Pertierra et al, 2017; Duffy & Lee, 2019) Despite their demonstrated impacts on native biodiversity, little attention has been given to plant invasions compared to animal invasions on these islands (le Roux et al, 2013), leaving a knowledge gap in the mechanisms underpinning plant invasion processes in these unique environments (Greve, Mathakutha, Steyn, & Chown, 2017)
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