Sexual Dimorphism in Flowers and Inflorescences

Eckhart, Vincent M.

doi:10.1007/978-3-662-03908-3_5

Cited by 128 publications

(111 citation statements)

References 159 publications

(186 reference statements)

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“…Tapetal degeneration and pollen abortion, a characteristic of CMS in crop systems (Hanson and Bentolila, 2004) is prevented by pentatricopeptide (PPR) restorers, such as those identified in this Mimulus system (Barr and Fishman, 2010). This provides a simple mechanism for effects of restorer segregation (in a CMS background) on floral morphology in our hybrids, and may also contribute to the common observation that male-sterile (female) flowers are smaller in many gynodioecious taxa (Baker, 1948;Delph et al, 1996;Eckhart, 1999). Our results are also consistent with observations in crop CMS hybrids, in which cytoplasmic type has a variety of effects on floral morphology in addition to fertility (Zubko et al, 2003;Hanson and Bentolila, 2004).…”

Section: Discussionmentioning

confidence: 75%

“…The causes behind this relationship are not understood fully, though there is some support for the idea of selection for greater perianth size in females to protect ovaries (Delph et al, 1996). In contrast, in gynodioecious species with separate male-sterile (female) and male-fertile (hermaphrodite) plants in natural populations, female corollas are almost always smaller than those of hermaphrodites (Baker, 1948;Delph et al, 1996;Eckhart, 1999;Shykoff et al, 2003). Two hypotheses have been proposed for this relationship.…”

Section: Introductionmentioning

confidence: 99%

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Cytoplasmic male sterility in Mimulus hybrids has pleiotropic effects on corolla and pistil traits

Barr

Fishman

2011

Heredity

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The mechanisms underlying genetic associations have important consequences for evolutionary outcomes, but distinguishing linkage from pleiotropy is often difficult. Here, we use a fine mapping approach to determine the genetic basis of association between cytonuclear male sterility and other floral traits in Mimulus hybrids. Previous work has shown that male sterility in hybrids between Mimulus guttatus and Mimulus nasutus is due to interactions between a mitochondrial gene from M. guttatus and two tightly linked nuclear restorer alleles on Linkage Group 7, and that male sterility is associated with reduced corolla size. In the present study, we generated a set of nearly isogenic lines segregating for the restorer region and male sterility, but with unique flanking introgressions. Male-sterile flowers had significantly smaller corollas, longer styles and greater stigmatic exsertion than fertile flowers. Because these effects were significant regardless of the genotypic composition of introgressions flanking the restorer region, they suggest that these floral differences are a direct byproduct of the genetic incompatibility causing anther abortion. In addition, we found a non-significant but intriguing trend for male-sterile plants to produce more seeds per flower than fertile siblings after supplemental pollination. Such pleiotropic effects may underlie the corolla dimorphism frequently observed in gynodioecious taxa and may affect selection on cytoplasmic male sterility genes when they initially arise.

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Section: Discussionmentioning

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Cytoplasmic male sterility in Mimulus hybrids has pleiotropic effects on corolla and pistil traits

Barr

Fishman

2011

Heredity

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“…Males disperse their pollen from erect peduncles that are held above the plant, whereas hermaphrodites and females release their pollen from subsessile inflorescences in the leaf axils (Durand, 1963;Pannell, 1997c). We might therefore expect that pollen grains dispersed from specialized peduncles have a better chance of reaching stigmas on other plants than those dispersed from the leaf axil (Eckhart, 1999), which the recent study in M. annua confirms (Eppley and Pannell, 2007a). The corollary of this is that hermaphrodites effectively disperse less pollen than they produce, compared with males, so that o p is smaller than a linear trade-off would predict.…”

Section: Sm Eppley and Jr Pannellmentioning

confidence: 99%

Inbreeding depression in dioecious populations of the plant Mercurialis annua: comparisons between outcrossed progeny and the progeny of self-fertilized feminized males

Eppley

Pannell

2009

Heredity

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Inbreeding depression is a key factor in the maintenance of separate sexes in plants through selection for the avoidance of self-fertilization. However, very little is known about the levels of inbreeding depression in dioecious species, obviously because it is difficult to self-fertilize males or females. We overcame this problem by clonally propagating males from lineages in a dioecious metapopulation of the European annual plant Mercurialis annua, feminizing some of them and crossing the feminized with the unfeminized clones. Using this method, we compared the fitness of selfed vs outcrossed progeny under field conditions in Spain, where this species grows naturally. Multiplicative inbreeding depression (based on seed germination, early and late survival, seed mass and pollen viability) ranged from À0.69 to 0.82, with a mean close to zero. We consider possible explanations for both the low mean and high variance in inbreeding depression in M. annua, and we discuss the implications of our results for the maintenance of dioecy over hermaphroditism.

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“…containing both the female and male sexual function within the same flower) but plant breeding systems with separate female and male functions in different individuals have evolved several times13. Numerous studies have shown that female flowers have lower rewards than hermaphrodites in gynodioecious species14. Similarly, in species with dichogamy, nectar quantity is typically highest during the males phase12.…”

mentioning

confidence: 99%

“…Most have been examined in isolation (e.g. comparing colour morphs19; or genders, reviewed in14), which does not adequately represent the complex factors impacting nectar quality. In the present study, we use the gynodioecious plant, Geranium sylvaticum (wood cranesbill), as a model species to examine the combined effect of abiotic and floral-specific traits on nectar’s sugar content and production.…”

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confidence: 99%

Sexually-trimorphic interactions with colour polymorphism determine nectar quality in a herbaceous perennial

Varga

Soulsbury

2017

Sci Rep

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Amongst gynodioecious plant breeding systems, there can exist intermediate morphs with a reduction in their male function (i.e. reduced number of functional anthers). Along with this sexual trimorphism, plants can also show floral colour polymorphism. Such intricate mixtures of phenotypes within a species may have complex effects on floral rewards. Floral rewards are known to vary between sexually dimorphic species and to a lesser extent between colour morphs. However, the interactive effect of sexual trimorphism and colour polymorphism is unexplored. We measured nectar’s sugar content in the sexually trimorphic Geranium sylvaticum, a gynodioecious plant with a light/dark floral polymorphism. We found that nectar reward differed across genders and colour morphs. Results were not however consistent within the three genders; dark female and hermaphrodite flowers had higher sugar content than light morphs, whereas intermediate flowers did not. As expected, females and hermaphrodites had different nectar reward, with intermediate morphs being midway between the other genders. In intermediates, the sugar content was not related to the number of functional stamens. We show for the first time the existence of sex-specific differences between flower gender and colour morphs in nectar rewards. Our results demonstrate the importance of considering multiple and conflicting selection pressures to explain rewards.

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Sexual Dimorphism in Flowers and Inflorescences

Cited by 128 publications

References 159 publications

Cytoplasmic male sterility in Mimulus hybrids has pleiotropic effects on corolla and pistil traits

Cytoplasmic male sterility in Mimulus hybrids has pleiotropic effects on corolla and pistil traits

Inbreeding depression in dioecious populations of the plant Mercurialis annua: comparisons between outcrossed progeny and the progeny of self-fertilized feminized males

Sexually-trimorphic interactions with colour polymorphism determine nectar quality in a herbaceous perennial

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