Figure 4.

Projected principle component analysis (PCA) to identify the source of recent brown rat invasion (Rattus norvegicus) on (a) the Bischofs Islands (n = 21) and (b) Faraday (n = 6) and Murchison Island (n = 10). For all analyses, the parameter space was first defined using only samples from reference populations (triangles), and then, unknown samples were projected onto this space to identify their genetic origin (circles). For (a), n = 28 samples were collected prior to a failed eradication attempt on the Bischof Islands (2011) to evaluate bait failure as a cause of the eradication failure. All analyses were performed using the smartpca function from the software package EIGENSOFT v7.2.1 (Galinsky et al., 2016; Patterson et al., 2006; Price et al., 2006). Probable invasion routes are shown on (c) with solid red arrows, and the dashed arrow indicates potential future invasion