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The effect of future climate change is poorly documented in the tropics, especially in mountainous areas. Yet, species living in these environments are predicted to be strongly affected. Newly available high-resolution environmental data and statistical methods enable the development of forecasting models. Nevertheless, the uncertainty related to climate models can be strong, which can lead to ineffective conservation actions. Predicted studies aimed at providing conservation guidelines often account for a range of future climate predictions (climate scenarios and global circulation models). However, very few studies considered potential differences related to baseline climate data and/or did not account for spatial information (overlap) in uncertainty assessments. We modelled the environmental suitability for Phelsuma borbonica, an endangered reptile native to Reunion Island. Using two metrics of species range change (difference in overall suitability and spatial overlap), we quantified the uncertainty related to the modelling technique (n = 10), sample bias correction, climate change scenario, global circulation models (GCM) and baseline climate (CHELSA versus Worldclim). Uncertainty was mainly driven by GCMs when considering overall suitability, while for spatial overlap the uncertainty related to baseline climate became more important than that of GCMs. The uncertainty driven by sample bias correction and variable selection was much higher when assessed based on spatial overlap. The modelling technique was a strong driver of uncertainty in both cases. We eventually provide a consensus ensemble prediction map of the environmental suitability of P. borbonica to identify the areas predicted to be the most suitable in the future with the highest certainty. Predictive studies aimed at identifying priority areas for conservation in the face of climate change need to account for a wide panel of modelling techniques, GCMs and baseline climate data. We recommend the use of multiple approaches, including spatial overlap, when assessing uncertainty in species distribution models.

Le Bulbul orphée Pycnonotus jocosus a été introduit sur l'île de la Réunion au début des années 1970. La complexité du relief et la différence de répartition de la pluviosité sur les deux versants, font de la Réunion un modèle pour l’étude des processus de colonisation. Nos résultats mettent en évidence des vitesses de colonisation différentes des versants, la préférence allant aux milieux chauds et pluvieux qui sont colonisés en premier et où la densité de population est, encore à l’heure actuelle, largement supérieure à celle de l’autre versant On a pu ainsi montrer qu’il existait une corrélation négative entre le nombre d’oiseaux et l’altitude. Les milieux nous apparaissent comme un superindicateur rendant compte de l’hétérogénéité de répartition de l’oiseau. Celui-ci ne se cantonne pas aux milieux anthropisés de basse altitude comme dans les autres pays qu’il a colonisés, ni comme les autres espèces introduites à la Réunion. Il pénètre dans les forêts, y compris dans les formations indigènes.

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