Data from: 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
number of mtDNA haplotypes from 17 to 3. Modeling of demographic history
indicated a recent population bottleneck linked to the period of European
colonization (approximately 5 generations ago) but did not support a major
decline linked to Polynesian settlement. Effective population size
estimates were also larger for historical than contemporary kākāpō. Our
findings inform contemporary kākāpō management by indicating the timeframe
and possible cause of the bottleneck, which has implications for the
management of extant genetic diversity. We demonstrate the broader utility
of a historical perspective in understanding causes of decline and
managing extinction risk in contemporary endangered species.