Pollinator‐mediated selection on floral morphology: evidence for transgressive evolution in a derived hybrid lineage

Anton, Kristin A.; Ward, Jennifer Rhode; Cruzan, Mitchell B.

doi:10.1111/jeb.12083

Cited by 19 publications

(19 citation statements)

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“…Piriqueta caroliniana produces actinomorphic flowers most prolifically from May to August, on multiple vegetative branches and nodes per plant (Feldman 2008), and flower morphology does not differ among nodes (J. R. Ward, personal observation). Flowers are open for !6 h/d, regardless of pollination/fertilization status (Anton et al 2013) or environment (field vs. greenhouse; Anton 2008), and are visited by 140 species of insects from at least four orders (Feldman 2008). Although symmetry does not have significant effects on P. caroliniana's rates of insect visitation, increased floral perimeter and area and reduced petal separation are attractive to pollinators (Anton et al 2013).…”

Section: Introductionmentioning

confidence: 96%

“…Flowers are open for !6 h/d, regardless of pollination/fertilization status (Anton et al 2013) or environment (field vs. greenhouse; Anton 2008), and are visited by 140 species of insects from at least four orders (Feldman 2008). Although symmetry does not have significant effects on P. caroliniana's rates of insect visitation, increased floral perimeter and area and reduced petal separation are attractive to pollinators (Anton et al 2013). …”

Section: Introductionmentioning

confidence: 96%

“…Long-morph flowers might devote fewer resources to male function than their short-morph conspecifics (Kohn and Barrett 1992), so we predicted that long flower morphs would produce fewer total pollen grains (but see Valois-Cuesta et al 2012). Finally, we expected herkogamy to differ between hybrid and parental morphotypes but to be stable within and among years, as greenhouse-grown individuals showed little variation in this trait over time (Anton et al 2013). The P. caroliniana study system allowed us to compare sex allocation patterns between two distinct style morphs and among hybrid and parental morphotypes and to draw conclusions about the effects of sex allocation on hybrid zone dynamics.…”

Section: Introductionmentioning

confidence: 99%

“…Previous observations of common gardens showed interannual variation in floral traits, including area and petal separation (Anton et al 2013), so we expected to see differences over time. Since long floral morphs typically produce larger pollen grains than short morphs in distylous plants (Barrett and Cruzan 1994), including Piriqueta (M. B. Cruzan, personal observation), long morphs might experience energetic trade-offs, producing fewer total grains per flower.…”

Section: Introductionmentioning

confidence: 99%

“…Hybrids exhibit heterosis and positive epistasis for vegetative traits and fruit production (Rhode and Cruzan 2005). In common field gardens, H morphotypes produce larger flowers (greater area) with less petal separation (Anton et al 2013) than parental types.…”

Section: Introductionmentioning

confidence: 99%

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Variation in Sex Allocation and Floral Morphology in an Expanding Distylous Plant Hybrid Complex

Ward¹,

Cowart²,

Clifford³

et al. 2014

International Journal of Plant Sciences

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Editor: Susan J. MazerPremise of research. Sex allocation, the relative energy devoted to producing pollen, ovules, and floral displays, can significantly affect reproductive output and population dynamics. In this study, we investigated floral morphology and gamete production in bisexual, distylous plants from a self-incompatible hybrid complex (Piriqueta cistoides ssp. caroliniana Walter [Arbo]; Turneraceae). Sampling focused on two parent types (C, V) and their stable hybrid derivative (H). Since H morphotypes are heterotic for growth and fruit production, we hypothesized that they would produce larger flowers with more gametes. We also anticipated that plants with long styles (long morphs) would produce less pollen than short morphs, since long-morph pollen is larger.Methodology. Over two consecutive summers, flowers were collected from 1465 individual plants in 28 field populations. Floral parameters were measured digitally, and each flower's pollen number, ovule number, and stigma-anther separation was quantified under a dissecting microscope. Gamete production (n p 332) and stigma-anther separation (n p 119) were also quantified for plants from a greenhouse accession.Pivotal results. Floral display differed among morphotypes, with H plants producing the largest flowers and C plants displaying the least petal separation. Hybrid morphotypes produced significantly more pollen than parental morphotypes, and pollen quantity was significantly greater for long morphs. Ovule production, however, was greatest for V flowers. Stigma-anther separation differed between years and style morphs (greater for short morphs) but not among morphotypes or within a single season.Conclusions. Differences in pollen production between morphs were not consistent with trade-offs in pollen size and number or selection for increased male function in short morphs. Greater stigma-anther separation in short morphs supported the hypothesis of selection to reduce pollen interference. Enhanced floral display and pollen production followed other heterotic traits observed in H morphotypes. The superior ability of H morphotypes to attract pollinators and sire seeds might partially explain this hybrid zone's continuing expansion.

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Variation in Sex Allocation and Floral Morphology in an Expanding Distylous Plant Hybrid Complex

Ward¹,

Cowart²,

Clifford³

et al. 2014

International Journal of Plant Sciences

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Floral traits influence the opportunity for selection among male gametophytes: independent and combined effects of style length and petal area

Mazer

Chellew

Peach

2019

American J of Botany

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Premise Strong correlations between traits can obscure their independent effects on components of reproduction. Style length (SL) and petal area (PA) vary within species, for example, but their independent effects on the opportunity for selection among pollen genotypes are poorly understood. Previous work in Clarkia detected a positive effect of SL on pollen receipt, potentially intensifying selection. However, this apparent effect of SL may be influenced by a correlated trait, such as PA. Here, we examine the independent effects of these two traits on pollen receipt and performance. Methods We collected petals and styles from wild populations of two insect‐pollinated Clarkia taxa and estimated the independent and combined effects of SL and PA on pollen receipt and performance. Results In both taxa, SL and PA are positively correlated. In C. unguiculata, both traits positively and independently affect pollen receipt, but in C. xantiana ssp. xantiana, the two traits act only in combination to affect pollen receipt. In both taxa, pollen receipt positively affects the numbers of pollen tubes entering and penetrating the style, as well as pollen tube attrition. Conclusions The effects of SL and PA on pollen receipt and performance are taxon specific. In C. unguiculata, both traits may be independent targets of selection due to their effects on pollen receipt. In C. xantiana ssp. xantiana, by contrast, the combined (but not independent) effects of SL and PA influence pollen receipt. Ecological differences between these taxa require exploration to understand the mechanisms by which these traits affect pollinator behavior.

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Rapid generation of ecologically relevant behavioral novelty in experimental cichlid hybrids

Feller

Selz

McGee

et al. 2020

Ecology and Evolution

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The East African cichlid radiations are characterized by repeated and rapid diversification into many distinct species with different ecological specializations and by a history of hybridization events between nonsister species. Such hybridization might provide important fuel for adaptive radiation. Interspecific hybrids can have extreme trait values or novel trait combinations and such transgressive phenotypes may allow some hybrids to explore ecological niches neither of the parental species could tap into. Here, we investigate the potential of second‐generation (F2) hybrids between two generalist cichlid species from Lake Malawi to exploit a resource neither parental species is specialized on: feeding by sifting sand. Some of the F2 hybrids phenotypically resembled fish of species that are specialized on sand sifting. We combined experimental behavioral and morphometric approaches to test whether the F2 hybrids are transgressive in both morphology and behavior related to sand sifting. We then performed a quantitative trait loci (QTL) analysis using RADseq markers to investigate the genetic architecture of morphological and behavioral traits. We show that transgression is present in several morphological traits, that novel trait combinations occur, and we observe transgressive trait values in sand sifting behavior in some of the F2 hybrids. Moreover, we find QTLs for morphology and for sand sifting behavior, suggesting the existence of some loci with moderate to large effects. We demonstrate that hybridization has the potential to rapidly generate novel and ecologically relevant phenotypes that may be suited to a niche neither of the parental species occupies. Interspecific hybridization may thereby contribute to the rapid generation of ecological diversity in cichlid radiations.

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Pollinator‐mediated selection on floral morphology: evidence for transgressive evolution in a derived hybrid lineage

Cited by 19 publications

References 89 publications

Variation in Sex Allocation and Floral Morphology in an Expanding Distylous Plant Hybrid Complex

Variation in Sex Allocation and Floral Morphology in an Expanding Distylous Plant Hybrid Complex

Floral traits influence the opportunity for selection among male gametophytes: independent and combined effects of style length and petal area

Rapid generation of ecologically relevant behavioral novelty in experimental cichlid hybrids

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