The Reordered North American Selection Regime and Late Quaternary Megafaunal Extinctions

Recent advances in genomics and palaeontology have begun to unravel the complex evolutionary history of the gray wolf, Canis lupus . Still, much of their phenotypic variation across time and space remains to be documented. We examined the limb morphology of the fossil and modern North American gray wolves from the late Quaternary (< ca 70 ka) to better understand their postcranial diversity through time. We found that the late-Pleistocene gray wolves were characterized by short-leggedness on both sides of the Cordilleran–Laurentide ice sheets, and that this trait survived well into the Holocene despite the collapse of Pleistocene megafauna and disappearance of the ‘Beringian wolf' from Alaska. By contrast, extant populations in the Midwestern USA and northwestern North America are distinguished by their elongate limbs with long distal segments, which appear to have evolved during the Holocene possibly in response to a new level or type of prey depletion. One of the consequences of recent extirpation of the Plains ( Canis lupus nubilus ) and Mexican wolves ( C. l. baileyi ) from much of the USA is an unprecedented loss of postcranial diversity through removal of short-legged forms. Conservation of these wolves is thus critical to restoration of the ecophenotypic diversity and evolutionary potential of gray wolves in North America.

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Measuring Late Quaternary Ursid Diminution in the Midwest

Quaternary Research ◽

10.1006/qres.1998.1964 ◽

1998 ◽

Vol 49 (3) ◽

pp. 322-329 ◽

Cited By ~ 14

Author(s):

Steve Wolverton ◽

R.Lee Lyman

Keyword(s):

Late Pleistocene ◽

North American ◽

Ursus Americanus ◽

Late Quaternary ◽

Black Bears ◽

American Midwest ◽

The Past ◽

American Black ◽

American Black Bears ◽

Average Size

Paleobiologists generally agree that within the past 10,000 yr North American black bears (Ursus americanus) have decreased in body and tooth size. Some researchers infer that diminution was gradual and continuous; thus, one might infer that a specimen is old if it is larger than an average-size modern bear. Ursid remains recovered in the 1950s from Lawson Cave, Missouri, that are larger than some modern bears have been reported to date to the late Pleistocene, but association with modern taxa, taphonomic considerations, and a radiocarbon date of 200 yr B.P. indicate that they are modern. Modern specimens from Lawson Cave and other parts of the American Midwest are relatively large compared to modern North American black bears from other areas, suggesting that many supposed late Pleistocene bears from the area might be modern also.

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