Multiple aspects of the selfing syndrome of the morning glory <i>Ipomoea lacunosa</i> evolved in response to selection: A Qst‐Fst comparison

Rifkin, Joanna L.; Liao, Irene T.; Castillo, Allan S.; Rausher, Mark D.

doi:10.1002/ece3.5329

Cited by 17 publications

(38 citation statements)

References 90 publications

(170 reference statements)

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“…The relative involvement of selection and drift in the evolution of ancillary traits contributing to the selfing syndrome has seldom been examined (but see [5][6][7]). One of the objectives of this study was to determine whether selection has contributed to the evolution of loss of pigmentation in a highly selfing species of morning glory, Ipomoea lacunosa.…”

Section: Introductionmentioning

confidence: 99%

Selection favors loss of floral pigmentation in a highly selfing morning glory

Duncan

Rausher

2020

PLoS ONE

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A common evolutionary trend in highly selfing plants is the evolution of the "selfing syndrome", in which traits associated with pollinator attraction are lost or greatly reduced. Limited information is available on whether these trait reductions are favored by natural selection or result from reduced purifying selection coupled with genetic drift. This study attempted to distinguish between these two possibilities for the evolutionary loss of floral pigmentation in the highly selfing species Ipomoea lacunosa. This study also tested the hypothesis that loss of floral pigmentation is caused by downregulation or loss of function in a tissue-specific anthocyanin transcription factor, as has been found in other plants. F2 individuals of a cross between white and pigmented individuals revealed segregation at two epistatically acting loci: one affecting pigmentation in both corolla throat and limbs (Anl1) and one affecting limb pigmentation (Anl2). Individuals that are homozygous for the "white" allele at Anl1 have white throats and limbs regardless of genotype at Anl2. In individuals with pigmented throats, homozygosity of the "white" allele at Anl2 produces white limbs. Flower color variation at Anl1 cosegregates with an R2R3-Myb anthocyanin transcription factor, which is down-regulated in white-flowers but not in pigmented flowers. Differential expression of the two alleles of this gene indicates that down regulation is caused by a cisregulatory change. Finally, allele-frequency differences at Anl1 were substantially and significantly greater than differences in allele frequencies at four microsatellite loci. These results are consistent with the hypotheses that the identified R2R3-Myb gene corresponds to Anl1 and that evolutionary loss of pigmentation in I. lacunosa was caused by selection. They are also consistent with previous studies demonstrating that loss of floral pigmentation is usually caused by down-regulation or functional inactivation of an R2R3-Myb gene.

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Section: Introductionmentioning

confidence: 99%

Selection favors loss of floral pigmentation in a highly selfing morning glory

Duncan

Rausher

2020

PLoS ONE

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“…A second issue that we address is whether reduced nectar production in the selfing I. lacunosa was caused by selection acting directly or indirectly through correlated traits. Rifkin et al (2019b) demonstrated that selection was responsible for reduced nectar production in this species but could not differentiate between direct or indirect selection on this trait. A finding that nectar traits constitute a distinct evolutionary module would imply that much of that selection acted directly on nectar traits.…”

Section: Introductionmentioning

confidence: 83%

“…The repeated evolution of the selfing syndrome (Barrett, 2002;Arunkumar et al, 2015) has fostered studies of its evolution in a wide range of flowering species, including Capsella (Slotte et al, 2012;Sas et al, 2016;Fujikura et al, 2017;Wozniak et al, 2020), Collinsia (Baldwin et al, 2011;Strandh et al, 2017;Frazee et al, 2021), Mimulus (Fenster & Ritland, 1994;Fishman et al, 2002Fishman et al, , 2015, and Ipomoea (Duncan & Rausher, 2013b;Rifkin et al, 2019bRifkin et al, , 2021. Although several studies have identified quantitative trait loci (QTLs) to assess the degree to which the evolution of different syndrome traits have evolved in a correlated fashion, most have focused on herkogamy, floral size, time to flowering, and pollen size and number (Rifkin et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Modularity and selection of nectar traits in the evolution of the selfing syndrome in Ipomoea lacunosa (Convolvulaceae)

Liao

Rifkin

Cao

et al. 2021

Preprint

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Although the evolution of the selfing syndrome often involves reductions in floral size, pollen, and nectar, few studies of selfing syndrome divergence have examined nectar. We investigate whether nectar traits have evolved independently of other floral size traits in the selfing syndrome, whether nectar traits diverged due to drift or selection, and the extent to which quantitative trait locus (QTL) analyses predict genetic correlations. We use F5 recombinant inbred lines (RILs) generated from a cross between Ipomoea cordatotriloba and I. lacunosa. We calculate genetic correlations to identify evolutionary modules, test whether traits have been under selection, identify QTLs, and perform correlation analyses to evaluate how well QTL properties reflect the genetic correlations. Nectar and floral size traits form separate genetic clusters. Directional selection has acted to reduce nectar traits in the selfing I. lacunosa. Calculations from QTL properties are consistent with observed genetic correlations. Floral trait divergence during mating system syndrome evolution reflects independent evolution of at least two evolutionary modules: nectar and floral size traits. This independence implies that adaptive change in these modules requires direct selection on both floral size and nectar traits. Our study also supports the expected mechanistic link between QTL properties and genetic correlations.

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“…1D; Table S1) under common greenhouse conditions (see Rifkin et al. 2019b for details; these are a subset of the plants used for Q ST estimation in that study). Briefly, seeds were scarified and germinated in soil in a growth room under a long‐day cycle (16:8 light:dark) and shifted to a short‐day cycle (12:12 light:dark) after approximately four weeks.…”

Section: Methodsmentioning

confidence: 99%

Morning glory species co-occurrence is associated with asymmetrically decreased and cascading reproductive isolation

et al. 2021

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Hybridization between species can affect the strength of the reproductive barriers that separate those species. Two extensions of this effect are (1) the expectation that asymmetric hybridization or gene flow will have asymmetric effects on reproductive barrier strength and (2) the expectation that local hybridization will affect only local reproductive barrier strength and could therefore alter within‐species compatibility. We tested these hypotheses in a pair of morning glory species that exhibit asymmetric gene flow from highly selfing Ipomoea lacunosa into mixed‐mating Ipomoea cordatotriloba in regions where they co‐occur. Because of the direction of this gene flow, we predicted that reproductive barrier strength would be more strongly affected in I. cordatotriloba than I. lacunosa. We also predicted that changes to reproductive barriers in sympatric I. cordatotriloba populations would affect compatibility with allopatric populations of that species. We tested these predictions by measuring the strength of a reproductive barrier to seed set across the species’ ranges. Consistent with our first prediction, we found that sympatric and allopatric I. lacunosa produce the same number of seeds in crosses with I. cordatotriloba, whereas crosses between sympatric I. cordatotriloba and I. lacunosa are more successful than crosses between allopatric I. cordatotriloba and I. lacunosa. This difference in compatibility appears to reflect an asymmetric decrease in the strength of the barrier to seed set in sympatric I. cordatotriloba, which could be caused by I. lacunosa alleles that have introgressed into I. cordatotriloba. We further demonstrated that changes to sympatric I. cordatotriloba have decreased its ability to produce seeds with allopatric populations of the same species, in line with our second prediction. Thus, in a manner analogous to cascade reinforcement, we suggest that introgression associated with hybridization not only influences between‐species isolation but can also contribute to isolation within a species.

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Multiple aspects of the selfing syndrome of the morning glory Ipomoea lacunosa evolved in response to selection: A Qst‐Fst comparison

Cited by 17 publications

References 90 publications

Selection favors loss of floral pigmentation in a highly selfing morning glory

Selection favors loss of floral pigmentation in a highly selfing morning glory

Modularity and selection of nectar traits in the evolution of the selfing syndrome in Ipomoea lacunosa (Convolvulaceae)

Morning glory species co-occurrence is associated with asymmetrically decreased and cascading reproductive isolation

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