北米の中央大陸のプレイストセンのブラウンベア

Paul Matheus¹, James Burns, Jaco Weinstock

¹Alaska Quaternary Center, University of Alaska Fairbanks, Fairbanks, AK, USA. ffpem1@uaf.edu

Science (New York, N.Y.)

|November 13, 2004

まとめ

アルバータ州で発見された2万6千年前のブラウンベアの化石は,移住モデルに異議を唱えている. 現代の茶色クマは,最後の氷河期最大期に氷床の南側に存在した集団から生まれたと考えられる.

科学分野:

パレオントロジー・パレオントロジー
遺伝学遺伝学とは
バイオジオグラフィーバイオジオグラフィー

背景:

現在のモデルでは,北米へのブラウンベア (Ursus arctos) の移住は10万~50万年前に発生し,南の拡大は12万年前以降,氷のない廊下を通過したことを示唆しています.
これらのモデルには,最後の氷河期最大期中にベリンギアの南にクマがいたという証拠が欠けている.

研究の目的:

ブラウンベアの新世界への移住のタイミングと経路を調査する.
最後の氷河期最大期の間,氷河の縁の南に集団が存続したかどうかを決定する.

主な方法:

色のクマの化石の放射線年代測定.
化石標本のミトコンドリアDNA (mtDNA) 分析.

主要な成果:

ベリンギアよりかなり南にあるアルバータ州中部で2万6000年前のブラウンベアの化石が発見されました.
ミトコンドリアDNA分析により,化石はカナダ南部とアメリカ北部の現代のブラウンベアと同じクラードに属していることが明らかになった.
この発見は,ブラウンベアが最後の氷河期最大期中に氷床の南にある地域に住んでいたことを示唆しています.

結論:

この発見は,ブラウンクマの新世界への移住の確立されたタイムラインに異議を唱えている.
カナダ南部と米国の現代茶色クマの集団は,最後の氷河期最大期中に氷河の縁の南に生き残った集団から起源を持つ可能性が高い.
これは,以前から考えられていたよりも,より複雑で,より早く,新世界におけるブラウンベアの存在を示唆している.

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