Selection for Heterozygosity Gives Hope to a Wild Population of Inbred Wolves

Staffan Bensch,Håkan Sand,Bengt Hansson,Olof Liberg,Henrik Andrén,Hans Chr. Pedersen,Douglas Sejberg,Petter Wabakken,Mikael Åkesson,Neil Gemmell

doi:10.1371/journal.pone.0000072

Abstract

Recent analyses have questioned the usefulness of heterozygosity estimates as measures of the inbreeding coefficient (f), a finding that may have dramatic consequences for the management of endangered populations. We confirm that f and heterozygosity is poorly correlated in a wild and highly inbred wolf population. Yet, our data show that for each level of f, it was the most heterozygous wolves that established themselves as breeders, a selection process that seems to have decelerated the loss of heterozygosity in the population despite a steady increase of f. The markers contributing to the positive relationship between heterozygosity and breeding success were found to be located on different chromosomes, but there was a substantial amount of linkage disequilibrium in the population, indicating that the markers are reflecting heterozygosity over relatively wide genomic regions. Following our results we recommend that management programs of endangered populations include estimates of both f and heterozygosity, as they may contribute with complementary information about population viability.

Highlights

Inbreeding is more likely to take place in small populations and may contribute to further decline and eventual extinction [1,2]
Several studies have documented that multilocus heterozygosity (MLH) may correlate with various fitness traits even in situations when f is held constant, suggesting that MLH contributes with complementary information about phenotypic and reproductive deterioration above that revealed by measuring inbreeding from pedigree data [8,9,10,11]
Though still globally distributed in the northern hemisphere, the wolf has in some parts of the world declined to only a fraction of its historical numbers, recently confirmed by genetic analyses of populations in both North America [22] and Europe [23,24]

Summary

Introduction

Inbreeding is more likely to take place in small populations and may contribute to further decline and eventual extinction [1,2]. It has become a key objective for conservation geneticists to monitor genetic variation [3] and to measure the occurrence of inbreeding in threatened populations [4]. Recent analyses have questioned the usefulness of MLH estimates as measures of the inbreeding coefficient ( f ) [5] If this is a general problem, as both simulated [6] and empirical data [7] suggest, it will have dramatic consequences for the interpretations of heterozygosity estimates in conservation of endangered populations. Very few studies to date have simultaneously investigated f and MLH and information is missing to what extent these variables may have separate effects on fitness [11]

Methods

Results

Conclusion