Some of these species are so distinct, that we cannot suppose that there has been time since the commencement of the last Glacial period for their migration and subsequent modification to the necessary degree.
Espezieotako batzuk hain ezberdinak direnez, ez dugu uste izaterik azken glaziaraldiaren hasieratik hona behar adina denborarik izan denik espeziook, migratu ondoren, behar bezanbaitean alda zitezen.