Discussion
Our work has leveraged an extremely rare genetic dataset before, during and after a subdivision event, to demonstrate that in any such event, whether natural or artificial, important genetic changes can occur very rapidly. We also show how to monitor this. In particular, this study revealed several insights about the genetic consequences of habitat fragmentation by linear infrastructure using an extensive pre- and post-construction SNP dataset on koalas. Firstly, we found that evidence for an immediate genetic signal was present but metrics’ dependant. Secondly, we show how the population subdivision as a result of the linear transport infrastructure project, will result in an increased rate of genetic diversity loss over time as a consequence of genetic drift, specifically for the population located above the linear transport infrastructure. This longer-term genetic consequence is an important aspect to consider when managing populations impacted by linear infrastructure projects. Last, using forward dispersal simulations, we show that a minimum of 8 koalas would need to be dispersing per generation from each side of the linear transport infrastructure to maintain genetic differentiation close to zero (e.g. low Fst < 0.05; (Lloydet al. 2013)) while 16 koalas would represent best case scenario given both genetic differentiation and genetic diversity would remain unchanged for both populations of koalas over the next 10 generations (e.g. 60 years).