Morphology does not covary with predicted behavioral correlations of the domestication syndrome in dogs.

Christopher W Wheat,Christina Hansen Wheat,Wouter Van Der Bijl

doi:10.1002/evl3.168

Christopher W Wheat, Christina Hansen Wheat + Show 1 more

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https://doi.org/10.1002/evl3.168

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Abstract

Domesticated animals display suites of altered morphological, behavioral, and physiological traits compared to their wild ancestors, a phenomenon known as the domestication syndrome (DS). Because these alterations are observed to co‐occur across a wide range of present day domesticates, the traits within the DS are assumed to covary within species and a single developmental mechanism has been hypothesized to cause the observed co‐occurrence. However, due to the lack of formal testing it is currently not well‐resolved if the traits within DS actually covary. Here, we test the hypothesis that the presence of the classic morphological domestication traits white pigmentation, floppy ears, and curly tails predict the strength of behavioral correlations in support of the DS in 78 dog breeds. Contrary to the expectations of covariation among DS traits, we found that morphological traits did not covary among themselves, nor did they predict the strength of behavioral correlations among dog breeds. Further, the number of morphological traits in a breed did not predict the strength of behavioral correlations. Our results thus contrast with the hypothesis that the DS arises due to a shared underlying mechanism, but more importantly, questions if the morphological traits embedded in the DS are actual domestication traits or postdomestication improvement traits. For dogs, it seems highly likely that strong selection for breed specific morphological traits only happened recently and in relation to breed formation. Present day dogs therefore have limited bearing of the initial selection pressures applied during domestication and we should reevaluate our expectations of the DS accordingly.

Highlights

Domesticated animals display suites of altered morphological, behavioral, and physiological traits compared to their wild ancestors, a phenomenon known as the domestication syndrome (DS)
We found that morphological traits did not covary among themselves, nor did they predict the strength of behavioral correlations among dog breeds
We tested whether the presence of three traits referred to as the morphological markers of domestication predicted the strength of behavioral correlations within the DS

Summary

Introduction

Domesticated animals display suites of altered morphological, behavioral, and physiological traits compared to their wild ancestors, a phenomenon known as the domestication syndrome (DS). Classic morphological “domestication traits” are white pigmentation, floppy ears, and curly tails and reduced aggression and increased sociability are among the expected behavioral changes caused by domestication Because these alterations are observed to co-occur across a wide range of present day domesticates, the traits within the DS are assumed to covary within species and a single developmental mechanism has been suggested to cause the DS. The mechanistic origin of the DS is currently unresolved, these findings have nurtured the hypothesis that the convergent patterns seen across domesticated species arise via a singular developmental mechanism such as altered neuroendocrine control of ontogenesis (Belyaev 1979), or neural crest deficit during embryogenesis (Wilkins et al 2014) Both of these influential studies have led to the general assumption that morphological changes, such as white pigmentation, floppy ears, and curly tails, have arisen as by-products of the physiological alterations caused by selection upon behavior (Wilkins et al 2014). It is generally assumed that DS traits covary, possibly due to a single developmental mechanism, further quantitative testing of this hypothesis is warranted

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