Genetic structure of the critically endangered Red‐headed Wood Pigeon Columba janthina nitens and its implications for the management of threatened island populations

Abstract

The Red-headed Wood Pigeon Columba janthina nitens is endemic to the Ogasawara Islands, an oceanic island chain located 1000 km south of the main islands of Japan. The subspecies is at high risk of extinction because of its small population size and restricted habitat range. We undertook genetic analyses of this pigeon using sequences of a portion of the mitochondrial control region and five microsatellite markers to estimate the genetic characteristics of two wild populations from the Bonin and Volcano Islands, as well as one captive breeding population. The genetic diversity of the wild individuals was exceptionally low in both the mitochondria (nucleotide diversity = 0.00105) and at the microsatellite (3.2 alleles per locus and H E = 0.12) loci. Higher numbers of microsatellite genotypes were observed in the Volcano Islands population than in the Bonin Islands population, which may be because of the relatively low impact of human disturbance. The most common mitochondrial haplotypes and microsatellite alleles observed in the two wild populations were completely fixed in the captive population. Our results suggest that the genetic diversity of the captive population needs to be increased. However, introduction of a wild individual into a captive population can lead to a decreased genetic diversity in the wild population and therefore should be done with caution. The genetic differentiation between the Bonin and the Volcano island groups was low, and the populations of the two island groups should be regarded as a single evolutionarily significant unit. However, special consideration is required for habitat conservation in the Volcano Islands, which may be functioning as a sanctuary for the Red-headed Wood Pigeon. For the long-term conservation of threatened bird species that live on remote oceanic islands, determination of management units considering gene flow caused by their flying capacity and maintenance of genetically suitable wild and captive populations are essential.

Genetic diversity, structure, and demography of Pandanus boninensis (Pandanaceae) with sea drifted seeds, endemic to the Ogasawara Islands of Japan: Comparison between young and old islands

“…Due to clear geological and ecological differences between these island groups, the genetic divergence and diversity of plants is expected to differ between them. However, population genetic studies in the Volcano Islands are limited (Ando et al, 2014; Sugai et al, 2013), largely due to the inaccessibility of the region.…”

Genetic and ecological conservation issues for oceanic island birds, revealed by a combination of the latest molecular techniques and conventional field work

“…Between two subspecies of Blue Chaffinch Fringilla teydea endemic to the Canary Islands, the declining population of F. t. polatzeki showed a lower genetic diversity than the stable population of F. t. teydea , and its captive population was suspected to suffer from inbreeding depression by lower sperm motility (Garcia‐del‐Rey et al, ). The endemic subspecies of the Japanese wood pigeon on the Ogasawara Islands showed much lower genetic diversity than other Columbiformes (Seki et al, ; Swinnerton et al, ; Young & Allard, ) and island endemics (Evans & Sheldon, ; Jamieson et al, ; Tarr & Fleischer, ) in wild populations (Ando et al, , ). Its ex situ population showed a further loss of genetic diversity and inbreeding depression, where the mitochondrial haplotype and microsatellite genotype were fixed as single types due to its establishment by only three individuals (Ando et al, ).…”

“…The endemic subspecies of the Japanese wood pigeon on the Ogasawara Islands showed much lower genetic diversity than other Columbiformes (Seki et al, ; Swinnerton et al, ; Young & Allard, ) and island endemics (Evans & Sheldon, ; Jamieson et al, ; Tarr & Fleischer, ) in wild populations (Ando et al, , ). Its ex situ population showed a further loss of genetic diversity and inbreeding depression, where the mitochondrial haplotype and microsatellite genotype were fixed as single types due to its establishment by only three individuals (Ando et al, ). Ex situ populations are often expected to be used as sources of reintroduction or conservation introduction into protected habitats or as supplementation of wild populations.…”

“…Such evolutionary processes are a high conservation priority for island endemics. Thus, special consideration is required to determine appropriate ESUs based on genetic structure, which have been suggested for several island bird species (Ando et al, ; Bollmer et al, ; Kawakami, Harada, et al, ; Petren et al, ) (details are shown in the next section). Habitat management and some artificial treatments to recover genetic diversity should be conducted within each ESU.…”

“…In ex situ conservation, management of genetic diversity is important to keep the ex situ population stable by capturing founders with sufficient genetic diversity in a captive breeding program to avoid inbreeding and the introduction of a new genetic variant from wild populations (Frankham et al, ). The genetic diversity of several island endemic bird species has been studied within and outside of their habitats (Ando et al, ; Frankham et al, ; Garcia‐del‐Rey et al, ; Swinnerton et al, ). Because of small population sizes in the wild, several case studies showed difficulty in establishing ex situ populations with an appropriate number of founders to maintain the genetic diversity of ex situ populations.…”