North America Deer
By: Dr. William E. Schlosser
Speciation occurs when biological populations of the same species become isolated from each other to an extent that prevents or interferes with gene flow. The separated populations develop adaptive responses to their restrictive environments. We look for the examples to prove it!
Sympatric speciation is the evolution of a new species from a surviving ancestral species while both continue to inhabit overlapping geographic regions. In evolutionary biology and biogeography, sympatric and sympatry are terms referring to organisms whose ranges overlap so that they occur together at least in some places.
This is the case with deer species in North America. Whitetail deer, (Odocoileus virginianus) is the native deer species of this continent. Through time and geographic habitat differences, sympatric speciation has given rise to mule deer (Odocoileus hemionus) to fill niche opportunities in higher elevation mountainous regions, steeper river basin habitats, and specialized feeding characteristics common to these lands.
In some western regions of North America, the white-tailed deer (Odocoileus virginianus) range overlaps with those of the mule deer (Odocoileus hemionus). Kamiak Butte supports populations of both species. They intermingle during the same periods of the year and on the same sites. Here these species representatives appeared on wildlife cameras on the south facing aspect within a couple weeks of each other.
White-tailed incursions in the Columbia River basin in southeast Washington and North Central Idaho have witnessed some hybridization evidence. I (Dr. Bill) have witnessed white-tailed deer does about 15 miles southwest of Kamiak Butte, near Almota, Washington, with seemingly-hybrid fawns. These offspring demonstrated difficulty running like a white-tailed deer but, could not stot (also called pronking), with all four feet coming down together like their mule deer genetic contributor either. In a rush, these fawns fell miserably.
Evidence suggests that most male hybrid-offspring are lost invitro, while surviving males are sterile. Female offspring often live to maturity, but most of these are infertile.
Further evidence suggests that fertile does can only breed with 100% pure males of either species, thus making offspring that are 75% one species and 25% of the other. Evidence has not been generated to confirm if embryo males of those unions can survive to maturity, or if they are reproductively fertile.
White-tailed deer (Odocoileus virginianus) and mule deer (Odocoileus hemionus) these species are in the same genus, but not the same species group. Deer of North America are more distantly related from each other than are elk relations within that genus species cadre. This has come as the description of sympatric speciation. It happened with the resultant populations being geographically adjacent and sometimes overlapping.