Transcript Mager_CARMAposter09

Genetic differentiation of caribou herds and reindeer in Northern Alaska
Karen H. Mager, Kevin E. Colson, and Kris J. Hundertmark
Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA ([email protected])
Introduction
Four herds of caribou on Alaska’s North Slope constitute management
units, yet the extent to which the herd concept approximates the genetic
population structure is unknown. Caribou need to be managed at the
population level and an understanding of herd connectivity is important given
the changing North Slope landscape.
Historical interactions between caribou and domestic reindeer have led
many to question the potential for introgression of reindeer genes into the
North Slope herds. In particular, some have speculated that Teshekpuk herd
animals descended from escaped domestic reindeer in the 1940s, and that the
herd may be unique.
Results
Microsatellite variability
All 18 loci were polymorphic (5–25 alleles/locus; mean 16.2). Allelic richness adjusted for sample size was similar
across all caribou herds (10.11–10.48) but lower in reindeer (7.78).
Herd differentiation
Fst estimates between caribou herds
were not significant except for PCH-WAH. Fst
estimates between reindeer and each caribou
herd were highly significant (Table 1).
Research Questions
1. Can the North Slope herds be genetically delineated?
2. What is the population structure of North Slope caribou and
to what extent does it resemble the four-herd concept?
3. Is there evidence for introgression of reindeer genes into
caribou herds or vice versa?
Western Arctic
(WAH)
n = 48
Teshekpuk
(TCH)
n = 52
Central Arctic
(CAH)
n = 19
Porcupine
(PCH)
n = 53
Wales Reindeer
(RD)
n = 34
Figure 1. Number of samples per herd (n) from herds sampled
Genetic structure
The most likely number of population clusters inferred from STRUCTURE was two. These clusters appear to correspond
closely to subspecies (Alaskan caribou and domestic reindeer) based on the proportion of each herd’s membership in the two
clusters (Table 2). Each individual was assigned primarily to its own subspecies with three exceptions—one RD individual’s
genotype was assigned almost entirely to the caribou cluster, and two individuals (1 RD and 1 CAH) appeared to have 30%
and 40%, respectively, of their genotype assigned to the opposite cluster (Figure 2).
Figure 2. STRUCTURE analysis of Alaskan caribou and reindeer under a two-population scenario. Each vertical line
represents an individual whose genotype is partitioned into one or two colors indicating the individual’s assigned
membership in the reindeer (gray) or caribou (red) genetic population. Herds of sampling origin are separated by
vertical black lines.
(Map from: Alaska Department of Fish and Game. 2001. Caribou management report of surveyinventory activities 1 July 1988 - 30 June 2000. C. Healy, editor. Project 3.0. Juneau, Alaska.)
Methods
Blood samples were collected from caribou of the four North Slope
Alaskan herds and from reindeer in Wales, Alaska (Figure 1). DNA was
amplified at 18 microsatellite loci. Allelic diversity, allelic richness and Fst
were calculated for each population and overall. North Slope population
structure—determining the most likely number of population clusters and
assignment of individuals to clusters—was inferred using program STRUCTURE.
Conclusions
• Caribou and reindeer could be clearly differentiated using traditional and individual-based statistics.
• If reindeer and caribou did interbreed in the recent past, those reindeer genes have largely disappeared from herds.
• Gene flow among herds is sufficiently high enough to homogenize them, though weak differentiation of WAH and PCH
suggest that distance may reduce gene flow.
ACKNOWLEDGEMENTS
This research was funded by National Fish and Wildlife Foundation grant #1499, and benefited from pilot research supported
by an early-career award to Dr. Hundertmark from Alaska EPSCoR (NSF award #EPS-0701898). K. Mager was supported by fellowships
from the UAF Resilience and Adaptation IGERT (NSF award 0654441) and Alaska EPSCoR. Biologists from Alaska Dept. of Fish and
Game, U.S. Fish and Wildlife Service, and the Yukon government provided samples—many are members of the CARMA network. The
Ongtowasruk reindeer herd owners allowed me to collect samples from their animals, with help from the UAF reindeer research program.
Thanks to CARMA for funding my travel to this year’s meeting.