Watchbird January 2022

Conservation and Education

Kakapo Conservation Helped by Genomics Study

Summary by Janice Boyd, PhD.

New Zealand was one of the last landmasses colo- nized by humans. Following Polynesian coloniza- tion circa 1360 CE and European colonization in the 1800s, and the resulting overhunting and introduc- tion of mammalian predators, New Zealand experi- enced major extinction events of endemic species. The kakapo ( Strigops habroptilus ), an endemic flightless parrot, was widespread before human arri-

remaining kakapo population. A high quality, chro- mosome - level reference genome was sequenced by the Vertebrate Genomes Project (VGP), and an ad- ditional 35 modern genomes were sequenced from the Stewart Island population and 14 genomes from the extinct mainland population (13 historical birds collected between 1847 and 1924). Stewart Island was isolated from the mainland about 10,000 years ago. Surprisingly, the present - day is- land kakapo were found to have a reduced number of harmful alleles (i.e., genes) compared to the (extinct) mainland individuals. Population genetics theory would expect the isolated island population would have experienced increased inbreeding com- pared with the mainland population and the in- creased inbreeding would have concentrated the level of harmful mutations. However, it appears that some of these damaging alleles were purged over the thousands of years by inbreeding and by genetic drift so that a significant fraction were lost in subsequent generations. Those offspring that ex- pressed the harmful mutations died before reproduc- ing (“ genetic purging ”) and some of the mutations simply were not passed on to offspring (“ genetic drift ”). As of 2021, a total of 201 kakapo survive and are managed on island sanctuaries. However, previous


val and likely numbered in the hundreds of thou- sands(!!). By 1995, the species was reduced to 51 birds: 50 kakapo from the isolated Stewart Island and one single male, named Richard Henry, from the extinct mainland population. Richard Henry and 39 Stewart Island birds were the only kakapo to repro- duce and are thus the ancestors of all birds born since 1995. There are now 201 indi- viduals remaining, all of them on the preda- tor - free islands of Whenua Hou (Codfish Island), Anchor, Chalky and Hauturu. This paper reported on the first genome se- quencing and population genomic analysis of the

Baby kakapos Photo by Andrew Digby New Zealand Department of Conservation

24 Volume XLVIX ● January 2022

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