Surprisingly Low Limits of Selection in Plant Domestication

Allaby, Robin G.; Kitchen, James L.; Fuller, Dorian Q.

doi:10.4137/ebo.s33495

Cited by 21 publications

(36 citation statements)

References 73 publications

(168 reference statements)

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“…For the most part it appears likely that grain size increase in annual seed crops evolved gradually through a process of unconscious selection (Fuller 2007;Fuller et al 2014). In addition the level of selection was kept somewhat low by the problem that the cost of selection is additive across all traits under selection and very strong selection increases the risk of population extinction (Allaby et al 2016). By contrast with staples like cereals, stronger selection pressures that risk local crop failure would be more tolerable in non-staple fruits.…”

Section: Comparing Rates Of Domestication and Implications For Selectionmentioning

confidence: 99%

Long and attenuated: comparative trends in the domestication of tree fruits

Fuller

2017

Veget Hist Archaeobot

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This paper asks whether we can identify a recurrent domestication syndrome for tree crops (fruits, nuts) and track archaeologically the evolution of domestication of fruits from woody perennials. While archaeobotany has made major contributions to documenting the domestication process in cereals and other annual grains, long-lived perennials have received less comparative attention. Drawing on examples from across Eurasia, comparisons suggest a tendency for the larger domesticated fruits to contain seeds that are proportionally longer, thinner and with more pointed (acute to attenuated) apices. Therefore, although changes in flavour, such as increased sweetness, are not recoverable, seed metrics and shape provide an archaeological basis for tracking domestication episodes in fruits from woody perennials. Where available, metrical data suggest length increases, as well as size diversification over time, with examples drawn from the Jomon of Japan (Castanea crenata), Neolithic China (Prunus persica) and the later Neolithic of the Near East (Olea europaea, Phoenix dactylifera) to estimate rates of change. More limited data allow us to also compare Mesoamerica avocado (Persea americana) and western Pacific Canarium sp. nuts and Spondias sp. fruits. Data from modern Indian jujube (Ziziphus mauritiana) are also considered in relation to seed length:width trends in relation to fruit contents (flesh proportion, sugar content). Despite the long generation time in tree fruits, rates of change in their seeds are generally comparable to rates of phenotypic evolution in annual grain crops, suggesting that gradual evolution via unconscious selection played a key role in initial processes of tree domestication, and that this had begun in the later Neolithic once annual crops had been domesticated, in both west and east Asia.

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Section: Comparing Rates Of Domestication and Implications For Selectionmentioning

confidence: 99%

Long and attenuated: comparative trends in the domestication of tree fruits

Fuller

2017

Veget Hist Archaeobot

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“…First, there is the notion that the domesticate population is derived from a relatively small subsample of the wild population as proto‐farmers “captured” small populations for cultivation and effectively isolated them from the wild gene pool. Second, the selection pressures involved in the transition to the domesticated form would have further reduced population sizes through the effects of the substitution load (Allaby, Kitchen, & Fuller, ; Haldane, ), originally referred to by Haldane as “the cost of selection.”…”

Section: Introductionmentioning

confidence: 99%

“…Archaeological data show that selection for domestication syndrome traits such as loss of seed shattering and seed size was weak—comparable to that of natural selection (Purugganan & Fuller, ; 2011)—and that the onset of selection likely preceded domesticated forms by over ten thousand years in the case of the cereals of the Near East (Allaby, Stevens, Lucas, Maeda, & Fuller, ). These observations are supported by underlying theory, which suggests that under the constraints of the substitution load, there could only have been relatively few loci of selection and that weak selection would have been involved (Allaby et al., ). Consequently, there are relatively few opportunities for hitchhiking effects that may contribute to the mutation load.…”

Section: Introductionmentioning

confidence: 99%

A re‐evaluation of the domestication bottleneck from archaeogenomic evidence

Allaby

Ware

Kistler

2018

Evolutionary Applications

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Domesticated crops show a reduced level of diversity that is commonly attributed to the “domestication bottleneck”; a drastic reduction in the population size associated with subsampling the wild progenitor species and the imposition of selection pressures associated with the domestication syndrome. A prediction of the domestication bottleneck is a sharp decline in genetic diversity early in the domestication process. Surprisingly, archaeological genomes of three major annual crops do not indicate that such a drop in diversity occurred early in the domestication process. In light of this observation, we revisit the general assumption of the domestication bottleneck concept in our current understanding of the evolutionary process of domestication.

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“…B. Linear regression of the maximum selection load (total amount of selection) carried across loci for different selection coefficients without any population extinction in simulations (fromAllaby et al, 2014).…”

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Archaeogenomic insights into the adaptation of plants to the human environment: pushing plant–hominin co-evolution back to the Pliocene

Allaby

Kistler

Gutaker

et al. 2015

Journal of Human Evolution

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The colonization of the human environment by plants, and the consequent evolution of domesticated forms is increasingly being viewed as a co-evolutionary plant-human process that occurred over a long time period, with evidence for the co-evolutionary relationship between plants and humans reaching ever deeper into the hominin past. This developing view is characterized by a change in emphasis on the drivers of evolution in the case of plants. Rather than individual species being passive recipients of artificial selection pressures and ultimately becoming domesticates, entire plant communities adapted to the human environment. This evolutionary scenario leads to systems level genetic expectations from models that can be explored through ancient DNA and Next Generation Sequencing approaches. Emerging evidence suggests that domesticated genomes fit well with these expectations, with periods of stable complex evolution characterized by large amounts of change associated with relatively small selective value, punctuated by periods in which changes in one-half of the plant-hominin relationship cause rapid, low-complexity adaptation in the other. A corollary of a single plant-hominin co-evolutionary process is that clues about the initiation of the domestication process may well lie deep within the hominin lineage.

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Surprisingly Low Limits of Selection in Plant Domestication

Cited by 21 publications

References 73 publications

Long and attenuated: comparative trends in the domestication of tree fruits

Long and attenuated: comparative trends in the domestication of tree fruits

A re‐evaluation of the domestication bottleneck from archaeogenomic evidence

Archaeogenomic insights into the adaptation of plants to the human environment: pushing plant–hominin co-evolution back to the Pliocene

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