A novel cost framework reveals evidence for competitive selection in the evolution of complex traits during plant domestication

10.1101/2020.10.30.362236 ◽

2020 ◽

Author(s):

Robin G Allaby ◽

Chris J Stevens ◽

Dorian Q Fuller

Keyword(s):

Grain Size ◽

Standard Model ◽

Complex Traits ◽

Selection Intensity ◽

Model Framework ◽

Competitive Selection ◽

The Standard Model ◽

Fundamental Insight ◽

Insight Into ◽

Over Time

AbstractMost models of selection incorporate some notion of an environmental degradation in which the majority of the population becomes less fit with respect to a character resulting in a pressure to adapt. Such models have been variously associated with an adaptation cost, the substitution load. Conversely, adaptative mutations that represent an improvement in fitness in the absence of environmental change have generally been assumed to be associated with negligible cost. However, such adaptations could represent a competitive advantage that diminishes resource availability for others and so induce a cost. This type of adaptation in the form of seedling competition has been suggested as a mechanism for increases in seed size during domestication. Here we present a novel cost framework for competitive selection that demonstrates significant differences in behaviour to environmental based selection in typical initial selection intensity and intensity over time. We show that selection intensity over time in grain size metrics of nine archaeological crops increases in one to several episodes fitting closely to the competitive selection model of single large effect alleles, but surprisingly in direct contrast to the expectations of the standard model of stabilizing selection. While size trait changes ultimately slow down in crops over time as expected from pleiotropic constraints expressed in the standard model, the mechanism outlined here shows possible complexities within the environmental based mode of shifting optimums in the standard model and a fundamental insight into the factors driving domestication.Significance statementWe present here a new model framework for selection based on direct competition between individuals rather than the more conventional approach of individual’s fitness being measured against an environmental gradient. The model explains patterns of increasing selection intensity seen in archaeological grain sizes of nine domesticated crops that otherwise contradict the expectations of shifting stabilising selection of complex traits. We show that grain size increases seen across domesticated crops are consistent with spontaneous competition between seedlings under cultivation for resources and so reveal a fundamental insight into the mechanism of plant adaptation to the human environment.

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New research reveals convergent evolution in plant domestication

Nature Middle East ◽

10.1038/nmiddleeast.2014.136 ◽

2014 ◽

Author(s):

Aisha El-Awady

Keyword(s):

Convergent Evolution ◽

Plant Domestication ◽

New Research

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PROSPECTS FOR THE USE OF REMOTE CROSS IN THE CITRUS CROPS SELECTION

Vestnik of the Russian agricultural science ◽

10.30850/vrsn/2019/4/46-49 ◽

1970 ◽

pp. 46-49 ◽

Cited By ~ 1

Author(s):

R. V. Kulyan

Keyword(s):

Complex Traits ◽

Germplasm Collection ◽

Early Maturity ◽

Russian Research Institute ◽

Citrus Germplasm ◽

The Status ◽

New Varieties ◽

Primary Test ◽

Growing Conditions ◽

Positive Traits

The Russian Research Institute of Floriculture and Subtropical Crops has the citrus germplasm collection, in total over 150 genotypes of various origins including 30 wild and semi-wild relatives. As a result of controlled hybridization in 17 crossings combinations of with the participation of relatives of citrus plants, new 769 hybrid offspring were obtained, which combine the traits of both the maternal and paternal genotypes. Analyzing the populations, promising combinations were highlighted: C. reticulata × Fortunella margarita (47.1%); C. x natsudaidai × 3252 (42.1%) and C. reticulata × C. reticulata ‘Cleopatra’ (40.9%) to create the gene pool of distant hybrids. From the mentioned combinations of crossings the greatest percent of seedlings which phenotypes tend to cultivated varieties was received. This hybrid material is a valuable source for isolating forms that are resistant to extreme environmental factors. According to phenotypic characteristics, hybrids were divided into three categories: I – Cultural, II – Semi-wild and III – Wild. Of the first category, the largest number 87 prospective forms were selected, and can be of interest for further breeding. As a result of the study of interspecific hybrid seedlings, 137 promising forms have been identified, which are carriers the complex traits such as dwarfism, thornless, early maturity and increased winter hardiness. From this set 17 genotypes were selected, which received the status of an elite forms, which successfully pass the primary test, and will be also useful in further breeding work for creating sources with a complex of positive traits and on breeding new varieties of citrus crops resistant to growing conditions.

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