Fig. 2

Reticulate biogeographic history: a Geological history of the Northern Hemisphere, showing how northern landmasses joined and split repeatedly over time as barriers (epicontinental seas) and connections (landbridges) arose and fell. b Scheme representing the difficulties to represent such a history into a single pattern of relationships between areas of endemism or “area cladogram.” In the Mesozoic, the northern landmasses were joined into the paleocontinents of Euramerica (EN–WP) and Asiamerica (WN–EP), whereas the present continental configuration between North America (EN–WN) and Eurasia (WP–EP) was attained during Cenozoic times. During some time periods, the four landmasses were isolated. Abbreviations: EN and WN: Eastern and Western North America divided by the Rocky Mountains; EP and WP: Asia and Europe separated by the Ural Mountains. Adapted from Sanmartín et al. (2001) and Sanmartín (2007)