Climatic Relict

Floral Climatic Relicts

While the number of climatic relict taxa is unknown (estimated to be several hundred species in Eurasia alone), Norwegian mugwort (Artemisia norvegia) is a commonly cited example. Reconstructions of past glacial environments show that the alpine plant was widely found throughout Central Europe during the last glacial maximum. Its extent decreased when the climate warmed and is now restricted to the less forested coastal mountains of Norway, the Ural Mountains, and two isolated communities in the Scottish Highlands where cooler conditions persist.

Climatic relicts do not have to occur exclusively due to climatic warming. For example, the European strawberry tree (Arbutus unedo) is currently found throughout the Iberian Peninsula and around the south and west coastlines of the Mediterranean Sea. However, its range extended farther north during the early-to-mid Holocene, when the climate was warmer than at present. Today, two disjunct populations of the tree remain in Western Ireland, where the North Atlantic Gulf Stream buffers the effects of the colder Irish climate.

Faunal Climatic Relicts

Faunal climatic relicts typically require less time than floral taxa to expand their ranges during periods of optimum climatic conditions. Species such as the musk ox (Ovibos moschatus) are capable of traveling large distances but are limited by the extent of their habitat. Fossil evidence suggests that during phases of Pleistocene glaciation, the musk ox expanded its range into Europe north of the Pyrenees and Alps beginning around 130,000 yrs. (years) ago. This range receded with the glaciers to its current-day relict position around the arctic tundra of Greenland and Canada.

Changes in climate can also affect marine taxa, resulting in climatic relict species such as the stag-horn coral (Acropora cervicornis). The coral is typically found in the warm waters of the Caribbean coinciding with the 18 °C monthly minimum seawater isotherm. However, the range of the staghorn coral was wider during the early-to-mid Holocene, when the Western Atlantic waters were warmer. The cold-sensitive staghorn coral can now only be found, in addition to the Bahamas, to the east of Florida, where the Florida Current helps maintain a relict population of the species.

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