Inbreeding depression in brown bear Ursus arctos

Laikre, Linda; Andrén, Robert; Larsson, Hans-Ove; Ryman, Nils

doi:10.1016/0006-3207(95)00084-4

Cited by 75 publications

(32 citation statements)

References 25 publications

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“…However, B was 0.62 in the South China tiger population, much higher than that in the Sumatran tiger and leopard but lower than at of other species. These results agree with Laikre et al (1996) that mammalian carnivores do suffer deleterious effects on viability from inbreeding, but the magnitude of inbreeding depression may be small relative to other mammals (Ralls et al 1988).…”

Section: Inbreeding Depressionsupporting

confidence: 90%

“…Therefore, we believe husbandry was probably not a key factor influencing the fertility of tigers. We observed no evidence that litter size was associated with the inbreeding coefficient of either kittens or their dams; in at least one carnivore, the brown bear (Ursus arctos) litter sized is affected by inbreeding (Laikre et al 1996).…”

Section: Inbreeding Depressionmentioning

confidence: 49%

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Sustainability of the South China tiger: implications of inbreeding depression and introgression

Fang²,

Li³

2007

Conserv Genet

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The South China tiger (Panther tigris amoyensis) is critically endangered with 73 remaining individuals living in captivity, all derived from six wild founders since 1963. The population shows a low level of juvenile survivorship and reproductive difficulties, and faces a huge conservation challenge. In this study, inbreeding depression and genetic diversity decline were examined by using pedigree data and 17 microsatellites. The constant B, which is related to the number of lethal equivalents, was estimated to be 0 for the offspring of noninbred parents, but was >0 for the offspring of inbred parents and for all offspring. Percentage of successfully breeding tigers inversely correlated with inbreeding level (r = -0.626, a = 0.05). Taken together, these findings suggest the population is suffering from inbreeding depression in juvenile survivorship and fecundity. No significant correlation was detectable for the mean litter size with f of either dams (r = -0.305, a = 0.46) or kittens (r = 0.105, a = 0.71), indicating litter size was not strongly subject to inbreeding depression. The average number of alleles per locus was 4.24 ± 1.03 (SE), but effective number of alleles was only 2.53 ± 0.91. Twenty-one alleles carried by early breeders at 13 loci were absent in the present breeders and potential breeders. Multilocus heterozygosity was inversely correlated with inbreeding levels (r = -0.601, a = 0.004). These findings suggest rapid allelic diversity loss is occurring in this small captive population and that heterozygosity is being lost as it becomes more inbred. Our phylogenetic analysis supports past work indicating introgression from northern Indochinese tigers in the population. As no wild representatives of the South China tiger can be added to the captive population, we may consider the alternate scenario of further introgression in the interest of countering inbreeding depression and declining genetic diversity.

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Section: Inbreeding Depressionsupporting

confidence: 90%

Section: Inbreeding Depressionmentioning

confidence: 49%

Sustainability of the South China tiger: implications of inbreeding depression and introgression

Fang²,

Li³

2007

Conserv Genet

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“…In small populations, inbreeding may become unavoidable and result in inbreeding depression. Inbreeding depression has been shown in both captive and wild mammalian populations (Laikre and Ryman 1991;Hedrick 1995;Laikre et al 1996;Roldan et al 1998;Slate et al 2000;Cassinello 2005). In 38 of 40 mammalian populations held in captivity, the average mortality was 33% higher in inbred animals than in offspring of unrelated parents (Ralls et al 1988).…”

Section: Introductionmentioning

confidence: 97%

The impact of founder events and introductions on genetic variation in the muskox Ovibos moschatus in Sweden

et al. 2011

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The muskox Ovibos moschatus (Zimmerman 1780) is a specialised arctic mammal with a highly fragmented circumpolar distribution, with native populations in Canada and east Greenland and introduced populations in west Greenland, Alaska, Siberia and Eurasia. In 1971, five O. moschatus individuals from an introduced population in Norway migrated to Sweden. After a peak population of 36 individuals in the mid-1980s, the Swedish population now numbers seven individuals, making it vulnerable to both demographic and genetic stochasticity (i.e. inbreeding). Here, we analyse genetic variation among native and introduced populations of O. moschatus to evaluate the genetic effect of sequential founder events in this species. Our results show that genetic variation among native and introduced O. moschatus populations do not conform entirely to the expectations from sequential founder events, most likely because of random processes associated with introduction. In the Swedish population, a calf resulting from the mating of a wild cow and a captive Greenlandic bull contributes significantly to the current genetic variation. Thus, even a single outbreeding event may, at least momentarily, increase the genetic variation and potentially prevent inbreeding depression. Our results should aid the long-term preservation of O. moschatus in Sweden and Europe.

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“…Second, Picton et al (19) found evidence of fluctuating asymmetry, a potential indicator of inbreeding depression, in post-dump closure YE bears. Third, inbreeding depression has been documented in captive brown bears (20), captive mammals (21), and wild mammal populations (22). Fourth, inbreeding and͞or a loss of variability can increase a population's probability of going extinct (3)(4)(5)(6).…”

mentioning

confidence: 99%

The history of effective population size and genetic diversity in the Yellowstone grizzly ( Ursus arctos ): Implications for conservation

Miller

Waits²

2003

Proc. Natl. Acad. Sci. U.S.A.

156

133

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Protein, mtDNA, and nuclear microsatellite DNA analyses have demonstrated that the Yellowstone grizzly bear has low levels of genetic variability compared with other Ursus arctos populations. Researchers have attributed this difference to inbreeding during a century of anthropogenic isolation and population size reduction. We test this hypothesis and assess the seriousness of genetic threats by generating microsatellite data for 110 museum specimens collected between 1912 and 1981. A loss of variability is detected, but it is much less severe than hypothesized. Variance in allele frequencies over time is used to estimate an effective population size of Ϸ80 across the 20th century and >100 currently. The viability of the population is unlikely to be substantially reduced by genetic factors in the next several generations. However, gene flow from outside populations will be beneficial in avoiding inbreeding and the erosion of genetic diversity in the future. Managers of threatened populations face the challenge of balancing genetic and demographic concerns. The importance of genetic forces in determining the fate of small populations is a topic of extended debate (1-3). Recent studies demonstrate that inbreeding depression can affect demographic rates and thereby increase extinction probability (4-6). In many cases, however, the shifts in demographic rates that drive population decline have nongenetic origins such as habitat degradation or human-caused mortality (1). Genetic factors may simply hasten the extinction process once the population is small. To evaluate the relative importance of genetic factors, managers need to know the current and historical effective population size (N e ). By measuring the amount of the gene pool passed on to the next generation, N e determines the rate that diversity declines and the degree of inbreeding (7). Unfortunately, estimating current N e is difficult (8) and few estimates of historical N e exist (e.g., refs. 9 and 10). Here we demonstrate how molecular genetic analysis of museum specimens can be combined with demographic data to estimate historical and current N e and address genetic concerns for the Yellowstone grizzly bear.Since 1800, grizzly bears (a regional name for brown bears) have been extirpated from Ͼ99% of their historic range south of the Canadian border (11), which prompted their listing under the U.S. Endangered Species Act in 1975. Substantial numbers persist only in the Yellowstone Ecosystem (YE) population and the Northern Continental Divide Ecosystem (NCDE) population along with small numbers in several mountain ranges that extend south from Canada (ref. 12; Fig. 1). Unlike other grizzly populations in the lower 48 states, the one in the YE is and has been isolated for approximately a century. In the early 1990s the U.S. Fish and Wildlife Service began exploring options for addressing genetic concerns in the population. The importance of genetics was again highlighted in 1995 when a federal judge ruled that the U.S. Fish and Wildlife Service had failed t...

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Inbreeding depression in brown bear Ursus arctos

Cited by 75 publications

References 25 publications

Sustainability of the South China tiger: implications of inbreeding depression and introgression

Sustainability of the South China tiger: implications of inbreeding depression and introgression

The impact of founder events and introductions on genetic variation in the muskox Ovibos moschatus in Sweden

The history of effective population size and genetic diversity in the Yellowstone grizzly ( Ursus arctos ): Implications for conservation

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