Posts Tagged ‘mammoth hybrids’

The Eurasian Steppe Mammoth (Mammuthus trogontherii) may be the same species as the North American Mammoth (Mammuthus columbi)

February 23, 2016

Eurasian steppe mammoths crossed the Bering Land Bridge early during the Pleistocene (~1.9 million years BP) and colonized North America.  They ecologically replaced stegomastodons over most of the continent but the ranges of both overlapped in Central America until the late Pleistocene.  Mammoths never colonized South America where stegomastodons continued to flourish until human hunters arrived on the scene.  Mammoths were probably better adapted than stegomastodons to the cooler more temperate climates that occurred over most of North America during the Pleistocene. Stegomastodons should not be confused with the American mastodon (Mammut americana) which co-existed with mammoths across most of North America for almost 2 million years.  They were able to co-exist because these 2 species favored different ecological niches.  Mammoths preferred higher drier grasslands, while mastodons were semi-aquatic denizens of wetlands.

Scientists long assumed mammoths that colonized North America evolved into a different species than Eurasian steppe mammoths.  North American mammoths of the late Pleistocene are given the scientific name Mammuthus columbi and Eurasian steppe mammoths are considered M. trogontherii.  However, a recent study of mammoth teeth determined M. columbi and M. trogontherii should be considered the same species.  The authors of this study think teeth of the Columbian mammoth originally used to compare with the teeth of the Eurasian steppe mammoth were from older individuals, thereby misleading scientists into thinking M. columbi was a different species.  The differences could be explained by normal wear and tear that one would expect from older animals.

Two Mammuthus Trogontherii (tundra mammoth) teeth,

2 teeth from a Eurasian steppe mammoth. (On sale for 840 British pounds)

Columbian mammoth tooth.  2 scientists determined from an analysis of teeth that the Columbian mammoth of North America and the Eurasian steppe mammoth were the same species.

Eurasian steppe mammoths evolved into woolly mammoths (M. primigenius) about 370,000 years ago during an harsh Ice Age.  Woolly mammoths also crossed the Bering Land Bridge, and as I mentioned in my previous blog post, hybridized with Columbian mammoths wherever the ranges of the 2 species overlapped.

Reference:

Lister, A. M., and A.V. Scher

“Evolution and Dispersal of Mammoth across the Northern Hemisphere”

Science 2015

The Southern and Northern Range Limits of the Columbian Mammoth (Mammuthus columbi)

February 18, 2016

If the U.S. government exiled me for some reason, I’d consider moving to Canada or Costa Rica.  I’d probably choose the latter because the weather is nicer.  I fantasized about moving to Costa Rica a few months ago and even searched online for a house.  I found a nice home for sale at a price similar to the value of my current residence in Augusta, Georgia.  Monkeys and coati-mundis frequent the backyard there.  Alas, the satellite television service is reportedly poor, so I might not get to watch the Georgia Bulldogs play football.  I suppose, if I made this fantasy come true, I’d have to rename my blog–Costa Rica Before People.

Central America provided a diversity of habitats for many species of megafauna during the late Pleistocene.  During full glacials tropically heated water pooled near the equator and did not circulate into the North Atlantic.  The region stayed warm year round and was covered with various types of tropical forest.  Yet some grasslands must have existed because fossil evidence of the Columbian mammoth, a grazer, has been unearthed at a site in Costa Rica referred to as the Hacienda Silencio (Silent Estate).  (From what I can determine online this site sounds like an upscale resort.)  This is the southernmost known range limit of the Columbian mammoth.  A deep belt of tropical forests, inhospitable to Columbian mammoths, must have prevented this species from moving farther south and colonizing South America.  A specimen identified as a mammoth was found during the 1930s in Guyana, but that specimen has been lost, and it’s likely a misidentification.  Instead, the specimen probably represented another species of proboscidean that did colonize South America.

There were 4 genera of proboscideans living in Central America during the late Pleistocene–the aforementioned Columbian mammoth, as well as mastodon, stegomastodon, and gompothere.  The remains of mastodon and gompothere have never been found together in the same fossil site in this region, leading researchers to believe they occupied different types of habitat.  Mastodons preferred lowland aquatic habitats, while gompotheres lived in higher drier forests.  Columbian mammoths favored savannahs and prairies but could adapt to some wooded environments.  The wide geographic range of the Columbian mammoth is evidence that it was a particularly adaptable species, capable of surviving in many different habitats.

Famous Charles Knight painting of Columbian mammoths.  Most of the google images of this species depict it without fur.  Columbian mammoths probably had fur because they occurred all across North America and could endure all sorts of climatic conditions.

Range maps of Columbian and Woolly mammoths.  Fossil evidence of Columbian mammoths has been found farther south than this map indicates.  Genetic evidence suggests these 2 species occasionally interbred where their ranges overlapped.

Columbian mammoths lived as far north as southern Canada.  Genetic and morphological evidence suggests that it hybridized with woolly mammoths (Mammuthus primigenius) in the northern part of its range where it overlapped with its northern cousin.  Some mammoth specimens found in the Great Lakes region have been given the species name, Mammuthus jeffersonii.  Scientists suspect this purported species is merely a Columbian and woolly mammoth hybrid.  Columbian mammoths were substantially larger than woolly mammoths, so these hybrids were nearly all the result of male Columbian mammoths copulating with female woolly mammoths.  Male Columbian mammoths overpowered male woolly mammoths in battles over mating rights.  The same scenario holds true today in Africa where larger savannah elephants (Loxodonta africanus) occasionally mate with smaller forest elephants (L. cyclotis).  There is also a case of an African elephant successfully mating with an Asiatic elephant (Elephas maximus) in captivity.

Scientists haven’t yet conducted a genetic study to determine when Columbian mammoths diverged from woolly mammoths.  The ability of the 2 species to hybridize suggests this divergence was more recent than the fossil evidence suggests.

References:

Cabrales-Arroyo, Joaquin; et. al.

“The Proboscideans (Mammalia) from Mesoamerica”

Quaternary International July 2007

Enk, Jacob; et. al.

“Complete Columbian Mammoth Metagenome Suggests Interbreeding with Woolly Mammoths”

Genome Biology 2011

Lucas Spencer; Alvarado Guillermo, Edwardo Vega

“The Pleistocene Mammals of Costa Rica”

Journal of Vertebrate Paleontology 1997