March 27, 2009

Study shows how glaciers affected deer evolution

Gene Rhodes, Purdue University professor of forestry and natural resources, said DNA analysis of more than 1,700 deer throughout North America shows how the movement of glaciers segregated certain groups of deer and how that affected their genetic makeup. Glacial movement about 18,000 years ago isolated mule deer and black-tailed deer to areas that were suitable for their survival, sometimes cutting them off from each other. Those groups -- located in Alaska and Canada, and south along the U.S. West Coast to Mexico -- evolved genetically to deal with those conditions, creating several subspecies.

"From a conservation standpoint, it's important to know if you have unique or rare subspecies," Rhodes said. "We uncovered a tremendous diversity of unique groups of mule deer that could need management attention. You can't protect them if you don't know they are there."

Rhodes worked with Jim Heffelfinger, a regional game specialist with the Arizona Game and Fish Department who coordinated the collection of DNA samples, and Emily Latch, an assistant professor at the University of Wisconsin-Milwaukee, who was a post-doctoral researcher under Rhodes. Their work was published in the early online version of Molecular Ecology this past week.

The DNA database created through the project is one of the most extensive for any wildlife species in North America, Rhodes said.

Conservation officials can use the information to protect deer in specific areas and conserve genetic diversity contained in unique subspecies. Heffelfinger said conservation officials also could use the data to ensure there isn't too much co-mingling between subspecies.

"We can identify black-tailed and mule deer hybrid zones and areas where they are interbreeding and figure out what it is about that area that is bringing them together," Heffelfinger said. "Maybe there are things we can do with the habitat to maintain the integrity of the species."

Rhodes' research shows how mule deer and black-tailed deer reintegrated into some areas around the Rocky Mountains and, in some cases, interbred. He said that information could be valuable to hunting organizations that keep records of trophy deer to ensure a black-tailed deer isn't actually a hybrid of a black-tail with a mule deer, which could look like a very large black-tail.

"They want a way to confirm that a particular animal is what they think it is," Rhodes said. "By mapping these deer, we're taking the first step in helping clarify their records and achievements."

Several wildlife non-governmental groups funded Rhodes' research. His next step is to get a better understanding of where black-tailed and mule deer interact and find ways to better manage rare subspecies.

Writer: Brian Wallheimer, (765) 496-2050, bwallhei@purdue.edu

Source: Gene Rhodes, (765) 494-3601, rhodeso@purdue.edu

Ag Communications: (765) 494-8415;
Steve Leer, sleer@purdue.edu
Agriculture News Page

Quaternary climatic oscillations greatly influenced the present-day population genetic structure of animals and plants. For species with high dispersal and reproductive potential, phylogeographic patterns resulting from historical processes can be cryptic, overshadowed by contemporary processes. Here we report a study of the phylogeography of Odocoileus hemionus, a large, vagile ungulate common throughout western North America. We examined sequence variation of mitochondrial DNA (control region and cytochrome b) within and among 70 natural populations across the entire range of the species. Among the 1,766 individual animals surveyed, we recovered 496 haplotypes. Although fine-scale phylogenetic structure was weakly resolved using phylogenetic methods, network analysis clearly revealed the presence of 12 distinct haplogroups. The spatial distribution of haplogroups showed a strong genetic discontinuity between the two morphological types of O. hemionus, mule deer and black-tailed deer, east and west of the Cascade Mountains in the Pacific Northwest. Within the mule deer lineage, we identified several haplogroups that expanded before or during the Last Glacial Maximum, suggesting that mule deer persisted in multiple refugia south of the ice sheets. Patterns of genetic diversity within the black-tailed deer lineage suggest a single refugium along the Pacific Northwest coast, and refute the hypothesis that black-tailed deer persisted in one or more northern refugia. Our data suggest that black-tailed deer recolonized areas in accordance with the pattern of glacial retreat, with initial recolonization northward along a coastal route and secondary recolonization inland.

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