Genetic variation of the mitochondrial DNA control region across plains bison herds in USA and Canada.

Once numbering in the tens of millions, bison (Bison bison) have faced a broad range of challenges over the past century, including genetic impacts from the population bottleneck in the 1800s, and significant loss and fragmentation of habitat resulting in little opportunity for population growth on remaining small, geographically isolated reserves. To identify best practices for bison stewardship against this backdrop, managers must understand the genetic composition of existing conservation herds. This study characterized 14 plains bison (Bison bison bison) herds managed by the U.S. Department of Interior and Parks Canada Agency based on complete mtDNA control region sequences. Among 209 bison, we detected 11 major mtDNA control region haplotypes based on nucleotide substitutions and 23 sub-haplotypes where indels are considered. We determined matrilineal relationships between the herds and compared our genetic findings to historic records. The recent common ancestry of modern bison deriving from small, scattered groups combined with gene flow through foundation and translocation events between herds during the last 100 years, is reflected in Fst value (0.21), haplotype (0.48 ± 0.04) and nucleotide (0.004 ± 0.002) diversities, and mean number of pairwise differences (3.38 ± 1.74). Genetic diversity was distributed unevenly among herds, with 21.41% of genetic variation observed between herds. Median joining network, together with trends in the Tajima's D and Fs tests, revealed two patterns in the recent evolution of mtDNA sequences in bison: mutational process has generated diversity with a Hap 1 haplotype epicenter, and missed mtDNA haplotypes exist in the network due to bottleneck, loss through management practices, or incomplete sampling of specimens across conservation herds. This work significantly expands characterization of the genetic diversity among bison conservation herds, providing additional decision support for managers considering restoring gene flow to achieve long-term species viability.

Isotopic paleoecology of Northern Great Plains bison during the Holocene.

Bison (Bison bison) are one of the few terrestrial megafauna to survive the transition into the Holocene and provide a unique opportunity to study a species on a broad spatiotemporal scale. Today, bison are primarily managed in small and isolated herds with little known about their ancestral ecology. We studied the carbon and nitrogen isotopes of Northern Great Plains bison from the terminal Pleistocene and throughout the Holocene to gain insight into their paleoecology. This time span is contemporary with the first population bottleneck experienced by bison at the end of the Pleistocene and includes the second bottleneck which occurred in the late 19th century. Results were compared with modern bison herd isotopic values from Theodore Roosevelt National Park (TRNP). Patterns of isotopic variation found in bison over time indicate significant (δ13C p = 0.0008, δ15N p = 0.002) differences in diet composition and correlate with climate throughout the Holocene. Isotopic relationships described here reveal the plasticity of ancient bison in unrestricted rangelands during periods of climatic fluctuations. Managers at TRNP and elsewhere should pursue opportunities to expand bison range to maximize forage opportunities for the species in the face of future environmental change.