The Evolution of Recombination under Domestication: A Test of Two Hypotheses

Department of Genetics, Life Sciences Building, University of Georgia, Athens, Georgia, 30602, USA.
The American Naturalist (Impact Factor: 3.83). 02/2004; 163(1):105-12. DOI: 10.1086/380606
Source: PubMed


The successful domestication of wild plants has been one of the most important human accomplishments of the last 10,000 yr. Though our empirical knowledge of the genetic mechanisms of plant domestication is still relatively limited, there exists a large body of theory that offers a host of hypotheses on the genetics of domestication. Two of these that have not been addressed concern the role of recombination in the process of domestication. The first predicts an increase in recombination rate through domestication, while the second argues that recombination rate should serve as a preadaptation to domestication. This study makes use of data on chiasma frequencies available from almost a century of plant cytogenetical literature to test these two hypotheses. The results support the hypothesis that domestication selects for an increase in recombination, and in rejecting the preadaptation hypothesis, they suggest directions for future research into the possibility of preadaptation to domestication.

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Available from: Jeffrey Ross-Ibarra, Feb 19, 2014
    • "This can explain the elevated CO rates in Caprinae, as an evolutionary younger taxon. Regarding Caprinae, more CO events were present in goats and sheep than in Barbary sheep, which could be explained by the process of domestication that favors higher recombination rates in these 2 species[Ross-Ibarra, 2004]. However, only 1 specimen of Barbary sheep was available for this study and, considering the individual variability within species, the evidence for the effect of domestication is weak and demands further research. "
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    ABSTRACT: Despite similar genome sizes, a great variability in recombination rates is observed in mammals. We used antibodies against SYCP3, MLH1 and centromeres to compare crossover frequency, position along chromosome arms and the effect of crossover interference in spermatocytes of 4 species from the family Bovidae (Bos taurus, 2n = 60, tribe Bovini; Ovis aries, 2n = 54, Capra hircus, 2n = 60 and Ammotragus lervia, 2n = 58, tribe Caprini). Despite significant individual variability, our results also show significant differences in both recombination rates and the total length of autosomal synaptonemal complexes (SC) between cattle (47.53 MLH1 foci/cell, 244.59 µm) and members of the tribe Caprini (61.83 MLH1 foci, 296.19 µm) which can be explained by the length of time that has passed since their evolutionary divergence. Sheep displayed the highest number of MLH1 foci per cell and recombination density, although they have a lower diploid chromosome number caused by centric fusions corresponding to cattle chromosomes 1;3, 2;8 and 5;11. However, the proportion of MLH1 foci observed on the fused chromosomes in sheep (26.14%) was significantly lower than on the orthologous acrocentrics in cattle (27.6%) and goats (28.2%), and their distribution along the SC arms differed significantly. The reduced recombination rate in metacentrics is probably caused by interference acting across the centromere.
    No preview · Article · Sep 2015 · Cytogenetic and Genome Research
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    • "The authors attributed this difference to the advantage of increased recombination that facilitated to overcome unwanted correlations between characters in the course of selection. Similar conclusions were achieved in comparative analysis of chiasma frequency of domesticated and wild plant species (Ross-Ibarra, 2004). At the stage of primitive selection, recombination was a major factor of genetic variation allowing for a deep and very fast (on the evolutionary scale) reorganization of domesticated organisms. "
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    ABSTRACT: The notion of “recombination“ includes a range of genetic phenomena. Their common dominator is reassociation of pieces of genetic information resulting in new combinations that differ from the parental ones. Systematic recombination studies initiated by T. Morgan developed into one of the most fruitful branches of genetics. The achieved understanding of recombination is a product of combined efforts of cytogenetics, molecular biology, biochemistry, population genetics, and evolutionary biology. The importance of recombination determining the balance between stability and flexibility of genetic organization and the interplay between heredity and environment justifies the interest in this process within the “biodiversity” paradigm.
    Full-text · Chapter · Dec 2013
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    • "Ever since Darwin, investigations of domesticated plants and animals have made key contributions to the study of evolution; for recent examples, see [76]–[81]. "
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    ABSTRACT: Domestication can influence many functional traits in plants, from overall life-history and growth form to wood density and cell wall ultrastructure. Such changes can increase fitness of the domesticate in agricultural environments but may negatively affect survival in the wild. We studied effects of domestication on stem biomechanics in manioc by comparing domesticated and ancestral wild taxa from two different regions of greater Amazonia. We compared mechanical properties, tissue organisation and wood characteristics including microfibril angles in both wild and domesticated plants, each growing in two different habitats (forest or savannah) and varying in growth form (shrub or liana). Wild taxa grew as shrubs in open savannah but as lianas in overgrown and forested habitats. Growth form plasticity was retained in domesticated manioc. However, stems of the domesticate showed brittle failure. Wild plants differed in mechanical architecture between shrub and liana phenotypes, a difference that diminished between shrubs and lianas of the domesticate. Stems of wild plants were generally stiffer, failed at higher bending stresses and were less prone to brittle fracture compared with shrub and liana phenotypes of the domesticate. Biomechanical differences between stems of wild and domesticated plants were mainly due to changes in wood density and cellulose microfibril angle rather than changes in secondary growth or tissue geometry. Domestication did not significantly modify "large-scale" trait development or growth form plasticity, since both wild and domesticated manioc can develop as shrubs or lianas. However, "finer-scale" developmental traits crucial to mechanical stability and thus ecological success of the plant were significantly modified. This profoundly influenced the likelihood of brittle failure, particularly in long climbing stems, thereby also influencing the survival of the domesticate in natural situations vulnerable to mechanical perturbation. We discuss the different selective pressures that could explain evolutionary modifications of stem biomechanical properties under domestication in manioc.
    Full-text · Article · Sep 2013 · PLoS ONE
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