European colonization, not Polynesian arrival, impacted population size and genetic diversity in the critically endangered New Zealand Zākāpō

Island endemic species are often vulnerable to decline and extinction following human settlement, and the genetic study of historical museum specimens can be useful in understanding these processes. The kākāpō (Strigops habroptilus) is a critically endangered New Zealand parrot that was formerly widespread and abundant. It is well established that both Polynesian and European colonization of New Zealand impacted the native avifauna, but the timeframe and severity of impacts have differed depending on species. Here, we investigated the relative importance of the 2 waves of human settlement on kākāpō decline, using microsatellites and mitochondrial DNA (mtDNA) to characterize recent kākāpō genetic and demographic history. We analyzed samples from 49 contemporary individuals and 54 museum specimens dating from 1884 to 1985. Genetic diversity decreased significantly between historical and contemporary kākāpō, with a decline in mean number of microsatellite alleles from 6.15 to 3.08 and in n...