Effects of functionally asexual reproduction on quantitative genetic variation in the evening primroses (Oenothera, Onagraceae)

• Published in: American journal of botany Vol. 101; no. 11; pp. 1906 - 1914
• Main Authors: Godfrey, Ryan M, Johnson, Marc T. J
• Format: Journal Article
• Language: English
• Published: United States Botanical Society of America 01-11-2014; Botanical Society of America, Inc
• Subjects: Animals; Apomixis; asexual reproduction; Asexuality; Biological Evolution; Biological variation; Botany; coefficient of genetic variance; evolution; Evolution and Phylogeny; evolution of sex; Evolutionary genetics; evolvability; flowering; Flowers & plants; genetic correlation; Genetic Variation; Genotype & phenotype; herbivores; Herbivory; Heritability; heterozygosity; Heterozygote; leaf area; leaves; Muller's ratchet; Oenothera; Oenothera biennis; Oenothera biennis - genetics; Oenothera biennis - physiology; Onagraceae; Parthenogenesis; Phenotype; Phenotypic traits; phenotypic variation; Plant growth; Plant reproduction; Population characteristics; Population genetics; prediction; Quantitative genetics; Reproduction, Asexual; Sexual intercourse; Sexual reproduction; water content; coefficient of genetic variance; apomixis; evolvability; parthenogenesis; evolution of sex; Muller’s ratchet
• ISSN: 0002-9122; 1537-2197
• DOI: 10.3732/ajb.1400226

• Premise of the study: It has long been predicted that a loss of sexual reproduction leads to decreased heritable variation within populations and increased differentiation between populations. Despite an abundance of theory, there are few empirical tests of how sex affects genetic variation in phenotypic traits, especially for plants. Here we test whether repeated losses of two critical components of sex (recombination and segregation) in the evening primroses (Oenothera L., Onagraceae) affect quantitative genetic variation within and between populations.• Methods: We sampled multiple genetic families from 3–5 populations from each of eight Oenothera species, which represented four independent transitions between sexual reproduction and a functionally asexual genetic system called “permanent translocation heterozygosity.” We used quantitative genetics methods to partition genetic variation within and between populations for eight plant traits related to growth, leaf physiology, flowering, and resistance to herbivores.• Key results: Heritability was, on average, 74% higher in sexual Oenothera populations than in functionally asexual populations, with plant growth rate, specific leaf area, and the percentage of leaf water content showing the strongest differences. By contrast, genetic differentiation among populations was 2.8× higher in functionally asexual vs. sexual Oenothera species. This difference was particularly strong for specific leaf area. Sexual populations tended to exhibit higher genetic correlations among traits, but this difference was weakly supported.• Conclusions: These results support the prediction that sexual reproduction maintains higher genetic variation within populations, which may facilitate adaptive evolution. We also found partial support for the prediction that a loss of sex leads to greater population differentiation, which may elevate speciation rates.