Article

Evolution of plant breeding systems.

Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Ashworth Lab. King's Buildings, West Mains Road, Edinburgh EH9 3JT, UK.
Current Biology (Impact Factor: 9.92). 10/2006; 16(17):R726-35. DOI: 10.1016/j.cub.2006.07.068
Source: PubMed

ABSTRACT Breeding systems are important, and often neglected, aspects of the natural biology of organisms, affecting homozygosity and thus many aspects of their biology, including levels and patterns of genetic diversity and genome evolution. Among the different plant mating systems, it is useful to distinguish two types of systems: 'sex systems', hermaphroditic versus male/female and other situations; and the 'mating systems' of hermaphroditic populations, inbreeding, outcrossing or intermediate. Evolutionary changes in breeding systems occur between closely related species, and some changes occur more often than others. Understanding why such changes occur requires combined genetical and ecological approaches. I review the ideas of some of the most important theoretical models, showing how these are based on individual selection using genetic principles to ask whether alleles affecting plants' outcrossing rates or sex morphs will spread in populations. After discussing how the conclusions are affected by some of the many relevant ecological factors, I relate these theoretical ideas to empirical data from some of the many recent breeding system studies in plant populations.

5 Bookmarks
 · 
253 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The mode of pollination is often neglected regarding the evolution of selfing. Yet the distribution of mating systems seems to depend on the mode of pollination, and pollinators are likely to interfere with selfing evolution, since they can cause strong selective pressures on floral traits. Most selfing species reduce their investment in reproduction, and display smaller flowers, with less nectar and scents (referred to as selfing syndrome). We model the evolution of prior selfing when it affects both the demography of plants and pollinators and the investment of plants in pollination. Including the selfing syndrome in the model allows to predict several outcomes: plants can evolve either towards complete outcrossing, complete selfing, or to a stable mixed-mating system, even when inbreeding depression is high. We predict that the evolution to high prior selfing could lead to evolutionary suicides, highlighting the importance of merging demography and evolution in models. The consequence of the selfing syndrome on plant-pollinator interactions could be a widespread mechanism driving the evolution of selfing in animal-pollinated taxa.This article is protected by copyright. All rights reserved.
    Evolution 10/2014; · 4.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Heterodichogamy is defined as the presence of two flower morphs that exhibit male and female functions at different times among individuals within a population, and is regarded as an adaptation to promote outbreeding through enhanced intermorph pollination. In highly fragmented populations in which the morph frequency is biased, heterodichogamy may hamper population growth by reducing seed sets of the more numerous morph, and enhancing seed sets of the less numerous morph. In such situations, we hypothesize that individual plants experience greater seed sets if the opposite sexual morphs are nearby, and that individuals of a less numerous sexual morph have greater seed sets. After confirming heterodichogamy by observing flowering behavior and phenology, we tested these two hypotheses in a highly fragmented population of Machilus thunbergii, a putative heterodichogamous evergreen laurel tree. Our observations confirmed that M. thunbergii is heterodichogamous, consisting of two types of protogynous and bisexual flowers: a morning female (MF)–afternoon male morph and a morning male (MM)–afternoon female morph at the individual level. Sexual expression of the two morphs was highly synchronized and reciprocal. Investigation of seed-set rates revealed greater rates of both morphs if the opposite morph was nearby. The less numerous sexual morph (MF) showed a greater seed-set rate than the more numerous sexual morph (MM).
    Plant Species Biology 02/2015; · 1.28 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: • Although rewarding orchids are believed to have a high pollination efficiency, pollination success is often low, suggesting that rewarding orchids may be prone to pollen limitation. Assuming that selfing contributes significantly to fruit and seed set (i.e., reproductive assurance) and that the quality of selfed seeds is high (i.e., low inbreeding depression), it can be hypothesized that under these circumstances populations evolve to facultative or even complete self-pollination.• In this study, we performed emasculation and pollen supplementation experiments in the field to assess the extent of outcross pollen limitation and the contribution of autonomous self-pollination to fruit and seed set in the rewarding orchid Epipactis palustris. Hand-pollinations using cross and self-pollen were performed in the greenhouse to investigate the impact of selfing on seed set and seed quality and to assess the magnitude of inbreeding depression.• Fruit set under natural conditions was high: ca. 70% of all flowers set fruit. Percentage fruit set of emasculated plants was 56%, implying that fruit set in about 14% of all flowers was the result of autonomous self-pollination. Pollen supplementation significantly increased fruit and seed set, indicating strong outcross pollen limitation. Hand-pollination with cross pollen resulted in significantly higher seed set and seed quality compared with manual self-pollination, indicating high levels of early inbreeding depression (δ = 0.46 ± 0.08).• Overall, these results indicate that, despite the high pollination efficiency, populations of this rewarding orchid species were strongly pollen limited. Costs of early inbreeding depression, on the other hand, were high, which may prevent rapid evolution of complete selfing. © 2015 Botanical Society of America, Inc.
    American Journal of Botany 01/2015; 102(1):67-72. · 2.46 Impact Factor

Preview

Download
8 Downloads
Available from