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

Balcarcel, Ana; Sánchez‐Villagra, Marcelo R.; Segura, Valentina; Evin, Allowen

doi:10.1093/jmammal/gyaa135

Cited by 17 publications

(30 citation statements)

References 66 publications

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“…A classic example of the effect of hybridization on morphological traits are the Darwin finches in Galapagos, where most hybrid individuals have intermediate body size and beak shape compared with the parental species [ 186 ]. Several studies in this review reported intermediate phenotypes, e.g., in cetaceans [ 187 ], mustelids [ 188 ], camelids [ 189 ] and primates [ 181 ]. The presence of admixed individuals with intermediate phenotypes may impede species identification in the field.…”

Section: Discussionmentioning

confidence: 99%

Consequences of Hybridization in Mammals: A Systematic Review

Adavoudi¹,

Pilot²

2021

Genes

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Hybridization, defined as breeding between two distinct taxonomic units, can have an important effect on the evolutionary patterns in cross-breeding taxa. Although interspecific hybridization has frequently been considered as a maladaptive process, which threatens species genetic integrity and survival via genetic swamping and outbreeding depression, in some cases hybridization can introduce novel adaptive variation and increase fitness. Most studies to date focused on documenting hybridization events and analyzing their causes, while relatively little is known about the consequences of hybridization and its impact on the parental species. To address this knowledge gap, we conducted a systematic review of studies on hybridization in mammals published in 2010–2021, and identified 115 relevant studies. Of 13 categories of hybridization consequences described in these studies, the most common negative consequence (21% of studies) was genetic swamping and the most common positive consequence (8%) was the gain of novel adaptive variation. The total frequency of negative consequences (49%) was higher than positive (13%) and neutral (38%) consequences. These frequencies are biased by the detection possibilities of microsatellite loci, the most common genetic markers used in the papers assessed. As negative outcomes are typically easier to demonstrate than positive ones (e.g., extinction vs hybrid speciation), they may be over-represented in publications. Transition towards genomic studies involving both neutral and adaptive variation will provide a better insight into the real impacts of hybridization.

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Section: Discussionmentioning

confidence: 99%

Consequences of Hybridization in Mammals: A Systematic Review

Adavoudi¹,

Pilot²

2021

Genes

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“…Cranial illustrations modified after Balcarcel et al. (2021). Not all landmarks illustrated could be recorded for all species due to species‐specific cranial morphology.…”

Section: Figurementioning

confidence: 99%

Modularity patterns in mammalian domestication: Assessing developmental hypotheses for diversification

et al. 2021

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The neural crest hypothesis posits that selection for tameness resulted in mild alterations to neural crest cells during embryonic development, which directly or indirectly caused the appearance of traits associated with the “domestication syndrome” (DS). Although representing an appealing unitary explanation for the generation of domestic phenotypes, support for this hypothesis from morphological data and for the validity of the DS remains a topic of debate. This study used the frameworks of morphological integration and modularity to assess patterns that concern the embryonic origin of the skull and issues around the neural crest hypothesis. Geometric morphometric landmarks were used to quantify cranial trait interactions between six pairs of wild and domestic mammals, comprising representatives that express between five and 17 of the traits included in the DS, and examples from each of the pathways by which animals entered into relationships with humans. We predicted the presence of neural crest vs mesoderm modular structure to the cranium, and that elements in the neural crest module would show lower magnitudes of integration and higher disparity in domestic forms compared to wild forms. Our findings support modular structuring based on tissue origin (neural crest, mesoderm) modules, along with low module integration magnitudes for neural crest cell derived cranial elements, suggesting differential capacity for evolutionary response among those elements. Covariation between the neural crest and mesoderm modules accounted for major components of shape variation for most domestic/wild pairs. Contra to our predictions, however, we find domesticates share similar integration magnitudes to their wild progenitors, indicating that higher disparity in domesticates is not associated with magnitude changes to integration among either neural crest or mesoderm derived elements. Differences in integration magnitude among neural crest and mesoderm elements across species suggest that developmental evolution preserves a framework that promotes flexibility under the selection regimes of domestication.

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“…Nearly all domestic animals have been shown to have smaller brains than their wild counterparts [1][2][3][4][5][6][7]. Those that are most important to humans, mostly for consumption or companionship, display the greatest amount of reduction.…”

Section: Introductionmentioning

confidence: 99%

“…29%) [3] and cats (approx. 24%) [3], whose brains reduce more than twice as much as those of other domestics [6,[9][10][11][12]. Quantifying these changes has significant implications for assessing differences in information-processing [13,14] and the speed and mode of brain evolution [15][16][17][18], particularly since different sensory systems are variably affected in different domestic taxa [7].…”

Section: Introductionmentioning

confidence: 99%

Intensive human contact correlates with smaller brains: differential brain size reduction in cattle types

et al. 2021

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Cattle are one of the most intensively bred domestic animals, providing humans with a multitude of products and uses. Using data from the fossil record, we test if their domestication, as for other taxa, has resulted in a reduction of their brain size. We not only conclude that Bos taurus (domestic cattle) have smaller brains than their wild ancestor, Bos primigenius (aurochs), but that brain size varies significantly by breed, with some having much smaller brains than others. Differences in husbandry practices between several breed categories align with a range of human engagement, which also aligns with the degree of selection for docility. Sampling 317 domestics from 71 breeds, we investigate if differences in brain size correlate with the intensity of human contact. A clear pattern emerges whereby a brain reduction gradient parallels a gradient in behavioural selection. Bullfighting cattle, which are bred for fighting and aggressive temperament, have much larger brains than dairy breeds, which are intensively selected for docility. Our results add to a fundamental aspect of animal domestication theory: the interplay between basic features of the domestic environment—selection for docility, absence of predators and human provision of resources—seems to explain differences in brain size.

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

Cited by 17 publications

References 66 publications

Consequences of Hybridization in Mammals: A Systematic Review

Consequences of Hybridization in Mammals: A Systematic Review

Modularity patterns in mammalian domestication: Assessing developmental hypotheses for diversification

Intensive human contact correlates with smaller brains: differential brain size reduction in cattle types

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