Widespread misperception about a major East Asian biogeographic boundary exposed through bibliographic survey and biogeographic meta-analysis

Aim

The Watase line, a major biogeographic boundary between Palearctic and Oriental realms in East Asia, is generally drawn between Akuseki and Kodakara Islands of the Northern Ryukyu archipelago, Japan. However, no evidence can be found to support the positioning of the boundary between these two tiny volcanic islands. This study aimed to confirm whether and where the biogeographical boundary should be drawn.

Location

East Asia

Taxon 

Land snail, ant, dragonfly, butterfly, amphibian, reptile, bird, plant

Methods

A bibliographic survey was carried out to revisit an original definition of the Watase line and its usage. Biogeographic and meta-analyses were also performed using a Simpson dissimilarity index calculated from published distribution data to test whether and where any biogeographic boundary exists. To ensure the validity of the study design, similar surveys and analyses were conducted in another region of Southern Ryukyu, where a reliable biogeographic boun...