Invasive aliens threatened with native extinction: examining best practice for species translocations under climate change

Aim: Translocation remains a controversial strategy in species conservation. Here, we utilise the unusual scenario of invasive alien species (IAS) threatened with extinction in their native range to address key challenges in deciding 9whether9, 9where9, and 9when9 to implement translocation, and how best to approach conservation under seemingly contradictory circumstances. Location: Iberian Peninsula, NW Europe. Methods: Rhododendron ponticum ssp. baeticum was selected as a model IAS for case study analysis. We used species distribution models (SDMs) coupled with dynamic simulations of migration to assess: 1. the extinction risk posed to this species in its native Iberian range under climate change; 2. whether SDMs calibrated on the native range (replicating typical translocation planning) could predict invasive capacity in NW Europe; and 3. the extent to which recommended biogeographical constrains on translocations may limit available options. Insights gained on the above were used to build and test a generic decision framework for translocation, based on robust identification of microrefugia. Results: Our findings suggest a high likelihood of climate-induced extinction for R.p. ssp. baeticum in its native range. Notably, SDMs completely failed to predict invasive capacity in NW Europe. However, application of our framework was successful in identifying sites more proximate to the native range - albeit outside this species9 current biogeographic region - potentially suited to translocation. Main conclusions: The framework here developed can be used to guide translocation of climate-endangered species in a spatially and temporally precise manner. However, we caution that use of SDMs can possess short-comings in failing to capture a full picture of sites suited to translation, and in risk assessment of the capacity of translocated taxa to form invasive species. Strict biogeographic constraints to the selection of translocation sites can evidently help to safeguard against invasions, but may also severely hinder the options available to avert climate-induced extinctions.