16 Jun Hybrid Smith Aspens: An Ice Age Relic 

During my time learning about the Niobrara, I learned about the ecosystem and the variety of plants and animals that inhabit the area. Something that has really struck me as interesting since I have been here are the hybrid aspen trees that can only be found along the Niobrara River Valley. These hybrid aspens, known as Smith Aspens, are the progeny of the Quaking Aspen and the Bigtooth Aspen. While hybridization in plants is not uncommon, it is quite rare to find hybrid plants so far outside of the range of the parent plants. This is what has been observed in the hybrid Smith Aspen trees; neither parent species can be found within hundreds of miles of its hybrid offspring. How can this be? During the Pleistocene, Quaking and Bigtooth Aspen stands were quite common in the Great Plains, with their ranges overlapping in the Niobrara River Valley. This is when these two species hybridized to create the Smith Aspens. The ranges of the parent species went locally extinct while their hybrid progeny remained in the area. Interestingly, all of the hybrid trees are males. So how can they reproduce? They reproduce vegetatively by rhizomes, rather than by flowers and seeds. Because these trees do not reproduce sexually, hence not mixing genetic information, all of the hybrid Aspens in the Niobrara River Valley are of the first generation of their parent species. This makes the hybrid Smith Aspens true relics of the Ice Age. 

Photo Credit | Top Left: Quaking Aspen (Becca MacDonald, Sault College, Bugwood.Org); Top Right: Bigtooth Aspen (Paul Wray, Iowa State University, Bugwood.Org); Bottom: Hybrid Smith Aspen