Map of the Periglacial Region in Japan at the Height of the Last Glaciation

<p>The last glaciation peaked about 20,000 years ago. Most of northern Tohoku must have been unvegetated (white shading), so <i>Euhadra</i> probably colonised from the south in the early Holocene. Brown shading shows regions above sea level, blue is sea, and the black outline indicates present-day Japan. The distribution of the periglacial region in earlier epochs is more uncertain. Data compiled from [<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0030282#pbio-0030282-b56" target="_blank">56</a>–<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0030282#pbio-0030282-b58" target="_blank">58</a>].