The wapiti: instant megafauna for America, made in China

@bluewhalenowhead

Several species of mammals occur naturally in coniferous forests in both Eurasia and North America, such as the wolf (https://en.wikipedia.org/wiki/Wolf#/media/File:Canis_lupus_distribution_(IUCN).png), the brown bear (https://en.wikipedia.org/wiki/Brown_bear#/media/File:Ursus_arctos_range_map.svg), the moose (https://en.wikipedia.org/wiki/Moose#/media/File:Moose_distribution.png), and the least weasel (https://en.wikipedia.org/wiki/Least_weasel#/media/File:Least_Weasel_area.png).

This is unsurprising because the two continents - and their coniferous forest biome - were formerly connected across Beringia, the west-east land-bridge now interrupted by the Bering Sea (https://en.wikipedia.org/wiki/Beringia).

What is surprising is that the wapiti (Cervus canadensis) also occurs naturally on both continents (https://en.wikipedia.org/wiki/Elk#/media/File:Wapiti.png).

This is a species of relatively low latitudes. Because it is absent from current Beringia (Alaska and far-eastern Siberia) the break in its distribution is far wider than for any other of the shared species of mammals - making it by far the most disjunctly-distributed ungulate species on Earth.

The wapiti is so similar in Russia/China and Canada that it may not differ even at the level of subspecies.

The wapiti is a Eurasian species which was suddenly drawn across Beringia a mere 15 thousand years ago by the rapid extermination of large herbivores in North America.

Throughout the Pleistocene, a diverse fauna of ungulates of body mass greater than 200 kg was restricted to North America. All these species went extinct abruptly between 15 and eight thousand years ago.

The ecological vacuum thus created allowed the marginal populations of the wapiti in what is now far-eastern Siberia to get across a coniferous forest/tundra mosaic which had until then been a bridge too far for the species - followed by rapid colonisation of the more suitable lands to the south (see https://markgelbart.wordpress.com/2014/10/27/did-elk-cervus-elephus-live-in-north-america-prior-to-15200-bp/).

Metaphorically, the wapiti was sucked through a narrow aperture from its original continent into a new one, on which it thrived as a partial replacement for the extinct fauna. This doubled the distribution of the species 'overnight' in evolutionary time.

The story for bisons is different, because they have long been part of the Pleistocene fauna of North America. All that happened in response to the megafaunal extinction is that a new, relatively small species evolved.

Bison bison is in its own way a recent addition to the North American fauna, but the genus is not new there, and the species arose in situ.

The wapiti is more remarkable, because it is truly Eurasian as both genus and species, and merely expanded into North America - later being cut off from its still-existing original populations by a gap as wide as the distance from California to Korea.

See https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2013.2167

Posted on June 20, 2021 09:22 PM by milewski