Singular patterns of skull shape and brain size change in the domestication of South American camelids

SEGURA V.; SÁNCHEZ-VILLAGRA M.R.; BALCARCEL A.M.; EVIN A.

JOURNAL OF MAMMALOGY

ALLIANCE COMMUNICATIONS GROUP DIVISION ALLEN PRESS

Lugar: Lawrence; Año: 2020 vol. 102 p. 220 - 235

0022-2372

The pattern of selection in SouthAmerican camelids, and their demographic history and hybridization,has made the llama and alpaca singular cases of domestication among large herd animals.Skulls of South American camelids, including the two wild and the correspondingdomestic forms, were studied using D geometric morphometric methods. We describe theform (i.e. shape and size) differences and commonalities among the species, as well as betweenwild and domestic individuals. The four species are very similar morphologically,with few changes correlating with domestication. Nonetheless, these differences arestatistically significant, and include a flatter cranium, an inclined palate,and increasedairorhynchy in the domestics. The nature of the selection pressures on South Americancamelids, in contrast to those on other herded animals, and recent demographic events, likelyinfluenced the morphological patterns we discovered. In high-resolution morphospace,skull size, shape, and form, are all able to discriminate among species, with form having thegreatest success. This is of great import to the field of archaeology, where distinction ofwild and domestic forms has always been challenging. Most morphospace distancemetrics suggest a marginally closer relationship between the alpaca and vicuña,over the guanaco,supporting the hypothesis of the vicuña as the alpaca?s true ancestor. Relative brain sizechange between wild and domestic forms indicate a 15.4% reduction in the llama, and a 6.8%reduction in alpaca. This reduction is lower than previously thought, and the lowest reportedso far among the domesticated Artiodactyla.