geneticsmegafauna following human arrival in New

Extinctions can dramatically reshape biological communities. As a case in point, ancientmass extinction events apparently facilitated dramatic newevolutionary radiations of surviving lineages. However, scientists have yet to fully under-stand the consequences of more recent biological upheaval, such as the megafaunal extinctions that occurredgloballyover thepast 50 kyr.NewZealand was the world’s last large landmass to be colonized by humans, and its exceptional archaeological recorddocuments avast numberof vertebrate extinc-tions in the immediate aftermath of Polynesian arrival approximately AD 1280. This recently colonized archipelago thus presents an outstanding opportunity to test for rapid biological responses to extinction. Here, we use ancient DNA (aDNA) analysis to show that extinction of an endemic sea lion lineage (Phocarctos spp.) apparently facilitated a subsequent northward range expansion of a previously subantarctic-limited lineage. This finding parallels a similar extinction–replacement event in penguins (Megadyptes spp.). In both cases, an endemic mainland clade was completely eliminated soon after human arrival