Why are Biennials so Few?

Hart, Robin

doi:10.1086/283209

Cited by 96 publications

(51 citation statements)

References 19 publications

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“…An association between predominantly selfing mating systems and annuality is well documented (Stebbins, 1950;Barrett et al, 1996). Accordingly, the incidence of annual or biennial species in our list (43%) was substantially higher than their overall frequency in North America (21%, Hart, 1977), though we are not aware of a worldwide estimate. A related pattern is the predominance of herbaceous species in studies reporting delayed selfing; only 12% of our surveyed species were woody compared to a recent global estimate of 45% (FitzJohn et al, 2014).…”

Section: Patterns and Distribution Of Delayed Selfing In Angiospermsmentioning

confidence: 62%

The best of both worlds? A review of delayed selfing in flowering plants

Goodwillie

Weber

2018

American J of Botany

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In a series of seminal papers, David G. Lloyd (1979;Lloyd and Schoen, 1992) provided new insight into plant mating-system evolution by recognizing that the selective consequences of selfand cross-pollination and fertilization depend on the specifics of how and when they occur. In phenotypic models, Lloyd showed that the conditions that select for self-fertilization (selfing) facilitated by pollinators differ from those for selfing that occurs autonomously. Further, the selective consequences of autonomous selfing were shown to depend on its timing in anthesis in relation to cross-fertilization (outcrossing). The theory predicts that selfing that occurs after opportunities for outcrossing have passed (delayed selfing) should be selected under the broadest range of conditions.In general, selection of selfing is expected to be opposed by inbreeding depression, the reduced fitness of selfed progeny that results primarily from the expression of deleterious recessive alleles Charlesworth, 1987, Charlesworth andWillis, 2009). Counteracting the cost of inbreeding depression is the 50% genetic transmission advantage of selfing, which occurs because INVITED SPECIAL ARTICLE The best of both worlds? A review of delayed selfing in flowering plantsCarol Goodwillie 1,3 and Jennifer J. Weber PREMISE OF STUDY:In a seminal body of theory, Lloyd showed that the fitness consequences of selfing will depend on its timing in anthesis. Selfing that occurs after opportunities for outcrossing or pollen dispersal can provide reproductive assurance when pollinators are limited and is expected to incur little cost, even when inbreeding depression is high. As a result, delayed selfing is often interpreted as a "best-of-both-worlds" mating system that combines the advantages of selfing and outcrossing. METHODS:We surveyed 65 empirical studies of delayed selfing, recording floral mechanisms and examining information on inbreeding depression, autofertility, and other parameters to test the support for delayed selfing as a best-of-both-worlds strategy.KEY RESULTS: Phylogenetic distribution of the diverse floral mechanisms suggests that some basic floral structures may predispose plant taxa to evolve delayed selfing. Delayed selfing appears to serve as a best-of-both-worlds strategy in some but not all species. While the capacity for autonomous selfing is often high, it is lower, in some cases, than in related species with earlier modes of selfing. In other delayed-selfers, low inbreeding depression and reduced investment in corollas and pollen suggest limited benefits from outcrossing.CONCLUSIONS: Despite a growing literature on the subject, experimental evidence for delayed selfing is limited and major gaps in knowledge remain, particularly with respect to the stability of delayed selfing and the conditions that may favor transitions between delayed and earlier selfing. Finally, we suggest a potential role of delayed selfing in facilitating transitions from self-incompatibility to selfing.

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Section: Patterns and Distribution Of Delayed Selfing In Angiospermsmentioning

confidence: 62%

The best of both worlds? A review of delayed selfing in flowering plants

Goodwillie

Weber

2018

American J of Botany

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“…Such changes from annual to biennial strategies may evolve under distinct environmental conditions affecting juvenile survival. Annuals may evolve if survival to reproduction is low, in contrast, biennials are more likely to evolve if survival is higher (Cole 1954, Charnov and Schaffer 1973, Hart 1977, Klinkhamer et al 1997, Metcalf et al 2003. The regional variation in the year of flowering in European diploids may most probably reflect adaptation to increasing temperatures and accompanying decreasing levels of competition from EU-1 toward EU-3.…”

Section: Regional Differentiation In the Three Geo-cytotypesmentioning

confidence: 99%

“…For example, reduced adult plant survival has been suggested to favor monocarpy over polycarpy (Cole 1954, Charnov and Schaffer 1973, Hart 1977, Klinkhamer et al 1997, Metcalf et al 2003. Therefore, differences in responses to herbivores among geo-cytotypes from different regions may elucidate differences in plantherbivore coevolutionary histories.…”

Section: Responses To Herbivoresmentioning

confidence: 99%

Cytotype differences modulate eco‐geographical differentiation in the widespread plant Centaurea stoebe

Hahn

2013

Ecology

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Abstract. The evolution of optimal life history strategies is central for the fitness of organisms in a given environment. Besides divergent selection, other factors may determine regional patterns of differentiation and contribute to life history evolution. In a commongarden environment over three years, we examined life history differentiation across different eco-geographical regions and effects of a specialist root-insect herbivore in the widespread European plant Centaurea stoebe, spotted knapweed. This plant occurs as two cytotypes with contrasting life cycles: monocarpic diploids and polycarpic tetraploids. In addition, the tetraploid cytotype has more recently become invasive in North America. We found significant regional differentiation in traits related to the timing of reproduction and reproductive allocation, but contrasting patterns in diploids and tetraploids. In diploids the degree of regional differentiation was higher compared to native tetraploids, and in the latter compared to invasive tetraploids. Furthermore, a pronounced shift in environmental conditions between the native and introduced range could have contributed to the differentiation between native and invasive tetraploids. The study also revealed the potential of the root-mining insect herbivore Agapeta zoegana, used as a biological control organism, to increase plant performance (presumably through overcompensatory growth), especially in the polycarpic tetraploids, and more so in the introduced populations. These findings suggest that patterns of regional differentiation in C. stoebe may be partly determined by divergent selection, but also strongly modulated by life cycle differences among geo-cytotypes. Furthermore, our study highlights the importance in applying a comprehensive and long-term approach when studying regional differentiation in plants.

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“…When comparing the life histories of biennials with those of annuals and perennials, the Malthusian fitness is often used as a geometric growth rate (e.g. Hart 1977). Although valuable in the course of model development, the realism of this classical approach is limited by the assumption of a constant environment in which density-independent processes occur and a seed bank is absent.…”

Section: Models On Biennial Plantsmentioning

confidence: 99%

The realism of models in plant demography

Blom

1988

Acta Botanica Neerlandica

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Why are Biennials so Few?

Cited by 96 publications

References 19 publications

The best of both worlds? A review of delayed selfing in flowering plants

The best of both worlds? A review of delayed selfing in flowering plants

Cytotype differences modulate eco‐geographical differentiation in the widespread plant Centaurea stoebe

The realism of models in plant demography

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