A recent analysis by Moulton & Cropper (2019) of a global dataset on alien bird population introductions claims to find no evidence that establishment success is a function of the size of the founding population. Here, we re-analyse Moulton & Cropper’s data and show that this conclusion is based on flawed statistical methods—their data in fact confirm a strong positive relationship between founding population size and establishment success. We also refute several non-statistical arguments against the likelihood of such an effect presented by Moulton & Cropper. We conclude that a core tenet of population biology—that small populations are more prone to extinction—applies to alien populations beyond their native geographic range limits as much as to native populations within them.
Blackburn, T. M., Cassey, P., Lockwood, J. L., & Duncan, R. P. (2020). The relationship between propagule pressure and establishment success in alien bird populations: a re-analysis of Moulton & Cropper (2019). PEERJ, 8, 1-12. [e8766]. https://doi.org/10.7717/peerj.8766