Maclear's Rat Recreated?

Maclear's rat (Rattus macleari) is also known as Christmas Island rat. It is an extinct large rat only endemic on the remote Christmas Island in the Indian Ocean. The rat is named after Captain John Maclear (1838–1907) of the British survey-ship HMS Flying-Fish, who collected the specimen from Christmas Island in 1886.

Once abundant and unfamiliar with (and seemingly unafraid) of humans, large numbers of the creatures emerged and foraged in all directions at night. Maclear's rat might have been responsible for keeping the population of the Christmas Island red crab in check, as recent numbers of the crab are greater than in the past.

According to a study, introduced black rats (Rattus rattus) possibly carried a pathogen that exterminated both Maclear's Rat and the bulldog rat (Rattus nativitatis)[1]. The last recorded sighting was in 1903, although it is possible that Maclear's rats hybridized with black rats.

A DNA study found Maclear's rat to be the sister species of Hainald's rat (Rattus hainaldi) native only to the Indonesian island of Flores[2].

Now, scientists have revealed plans to bring back the extinct Christmas Island rat[3].

For the study, the researchers extracted and sequenced ancient DNA from two dry preserved skin samples of the Christmas Island rat, originally collected between 1900 and 1902 and held as part of the Oxford University Museum of Natural History collections. Their analyses show that even when the extremely high-quality Norway brown rat (Rattus norvegicus) is used as a reference, 4.85 per cent of the genome sequence is unrecoverable, with 1,661 genes recovered at lower than 90 per cent completeness, and 26 completely absent.

The question is: Why bother with the brown rat and not use the closely related Hainald's rat?

[1] Wyatt et al: Historical mammal extinction on Christmas Island (Indian Ocean) correlates with introduced infectious disease in PLoS One - 2008
[2] Thomson et al: A perspective for resolving the systematics of Rattus, the vertebrates with the most influence on human welfare in Zootaxa -2008
[3] Lin et al: Probing the genomic limits of de-extinction in the Christmas Island rat in Current Biology – 2022. See here.