Mapping Loci for Fox Domestication: Deconstruction/Reconstruction of a Behavioral Phenotype

Abstract

During the second part of the 20th century, Belyaev selected tame and aggressive foxes (Vulpes vulpes), in an effort known as the “farm-fox experiment”, to recapitulate the process of animal domestication. Using these tame and aggressive foxes as founders of segregant backcross and intercross populations we have employed interval mapping to identify a locus for tame behavior on fox chromosome VVU12. This locus is orthologous to, and therefore validates, a genomic region recently implicated in canine domestication. The tame versus aggressive behavioral phenotype was characterized as the first principal component (PC) of a PC matrix made up of many distinct behavioral traits (e.g. wags tail; comes to the front of the cage; allows head to be touched; holds observer’s hand with its mouth; etc.). Mean values of this PC for F1, backcross and intercross populations defined a linear gradient of heritable behavior ranging from tame to aggressive. The second PC did not follow such a gradient, but also mapped to VVU12, and distinguished between active and passive behaviors. These data suggest that 1) there are at least two VVU12 loci associated with behavior; 2) expression of these loci is dependent on interactions with other parts of the genome (the genome context) and therefore varies from one crossbred population to another depending on the individual parents that participated in the cross.

Genomic responses to selection for tame/aggressive behaviors in the silver fox (Vulpes vulpes)

“…The 45 heritability of these behavioral traits has been confirmed in multiple experiments (14)(15)(16)(17), 46 making these fox strains a promising model for the identification of the genetic basis of tame and aggressive behaviors. 48 To identify the genetic basis of the behavioral differences between tame and 49 aggressive fox strains we developed the fox meiotic linkage map, experimental cross-50 bred pedigrees, and mapped eight significant and suggestive quantitative trait loci (QTL) 51 for behavioral traits (17)(18)(19)(20). Although QTL mapping is a promising strategy for the 52 identification of genomic regions implicated in complex traits, this approach alone 53 usually does not allow identification of the causative genes and mutations.…”

“…Efforts were made to avoid close inbreeding in these 44 populations, allowing continuous selection for many decades and generations (9)(10)(11). The 45 heritability of these behavioral traits has been confirmed in multiple experiments (14)(15)(16)(17), 46 making these fox strains a promising model for the identification of the genetic basis of tame and aggressive behaviors. 48 To identify the genetic basis of the behavioral differences between tame and 49 aggressive fox strains we developed the fox meiotic linkage map, experimental cross-50 bred pedigrees, and mapped eight significant and suggestive quantitative trait loci (QTL) 51 for behavioral traits (17)(18)(19)(20).…”

Is evolution of domestication driven by tameness? A selective review with focus on chickens

“…For example, one study showed that a chromosomal region associated with increased tameness in Belyaev's foxes is orthologous to a domestication-related region in dogs, implying similar causal grounds in these two species (Kukekova et al, 2010). However, another study failed to find more than occasional similarities in brain gene expression differences between domesticated and wild specimens across a range of species (Albert et al, 2012).…”

Modular genetic control of innate behaviors

“…Long before the discovery of DNA, humans have bred domesticated mammals for desirable behavioral traits such as tameness, herding, and hunting [9]. Scientists are now comparing the genomic sequences of different breeds of dogs as well as recently domesticated wild foxes to narrow down genomic loci associated with specific behavioral traits [9,10]. Likewise, modern day scientists have selectively bred and created strains of mice that differ in burrowing behaviors, and performed genome-wide association studies to dissect how genomic variations contribute to quantifiable behavioral differences [11].…”