Detecting inter- and intra-island genetic diversity: population structure of the endangered crocodile newt, Echinotriton andersoni, in the Ryukyus

• Published in: Conservation genetics Vol. 21; no. 1; pp. 13 - 26
• Main Authors: Igawa, Takeshi, Sugawara, Hirotaka, Honda, Masanao, Tominaga, Atsushi, Oumi, Shohei, Katsuren, Seiki, Ota, Hidetoshi, Matsui, Masafumi, Sumida, Masayuki
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-02-2020; Springer Nature B.V
• Subjects: Animal Genetics and Genomics; Aquatic reptiles; Archipelagoes; Biodiversity; Biomedical and Life Sciences; Conservation Biology/Ecology; Crocodiles; Echinotriton andersoni; Ecology; Endangered species; Evolutionary Biology; Gene flow; Genetic diversity; Genetic structure; Geographical distribution; Habitat loss; Historical structures; Islands; Land bridges; Life Sciences; Plant Genetics and Genomics; Pleistocene; Population; Population decline; Population genetics; Population number; Population structure; Research Article; Salamandridae; Species extinction; Ryukyu Islands; Microsatellite; Population structure; Island population; Population genetics; Amphibian
• ISSN: 1566-0621; 1572-9737
• DOI: 10.1007/s10592-019-01219-8

The endangered crocodile newt,
Echinotriton andersoni
, is a relatively large species of the family Salamandridae and is distributed on six islands in the central part of the Ryukyu Archipelago, Japan. Because of an originally small distribution range and recent habitat loss, this species has been steadily declining in number. To elucidate fine-scale population structure, which is essential for effective conservation management, we analyzed genetic diversity and gene flow based on nine microsatellite loci. Our results identified three different island groups (Amamioshima, Tokunoshima, and Okinawajima) and multiple genetic assemblages within the Amami and Okinawa island groups. The gross genetic variation within each island was positively correlated with island size. Population structure followed a latitudinal cline and isolation by distance, even among geographically isolated islands. In northern Okinawajima, relatively complex genetic structure was observed. This unexpected population structure seems to reflect historical migration and distribution expansion through the formation of land bridges and shifted coastlines in the Pleistocene. We also found that small islands showed little genetic variation (Ukeshima, Sesokojima, and Tokashikijima). In particular, our findings revealed that the Tokashikijima population is at greater risk for extinction than the other populations because it has the smallest effective population size.