Low flower-size variation in bilaterally symmetrical flowers: Support for the pollination precision hypothesis

Mating system shifts recurrently drive specific changes in organ dimensions. The shift in mating system from out-breeding to selfing is one of the most frequent evolutionary transitions in flowering plants and is often associated with an organ-specific reduction in flower size. However, the evolutionary paths along which polygenic traits, such as size, evolve are poorly understood. In particular, it is unclear how natural selection can specifically modulate the size of one organ despite the pleiotropic action of most known growth regulators. Here, we demonstrate that allelic variation in the intron of a general growth regulator contributed to the specific reduction of petal size after the transition to selfing in the genusCapsella. Variation within this intron affects an organ-specific enhancer that regulates the level of STERILE APETALA (SAP) protein in the developing petals. The resulting decrease inSAPactivity leads to a shortening of the cell proliferation period and reduced number of petal cells. The absence of private polymorphisms at the causal region in the selfing species suggests that the small-petal allele was captured from standing genetic variation in the ancestral out-crossing population. Petal-size variation in the current out-crossing population indicates that several small-effect mutations have contributed to reduce petal-size. These data demonstrate how tissue-specific regulatory elements in pleiotropic genes contribute to organ-specific evolution. In addition, they provide a plausible evolutionary explanation for the rapid evolution of flower size after the out-breeding-to-selfing transition based on additive effects of segregating alleles.

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Flower size variation in Danhatchia (Orchidaceae)

Telopea ◽

10.7751/telopea14437 ◽

2020 ◽

Vol 23 ◽

pp. 155-162

Author(s):

Matthew Renner ◽

Keyword(s):

New Zealand ◽

Size Variation ◽

Distinct Species ◽

Flower Size ◽

Morphological Evidence ◽

Herbarium Specimens ◽

Flower Opening ◽

Petal Length ◽

Lower Limits ◽

Range Of Variation

Danhatchia novaehollandiae D.L.Jones & M.A.Clem. and D. australis (Hatch) Garay & Christenson were separated at species rank due to differences in petal length and flower opening, with the Australian species having smaller, tardily opening flowers. From this, flower lengths for Australia and New Zealand are expected to be bi-modally distributed with peaks at c. 3 mm and c. 5 mm respectively. Flowers on all available herbarium specimens in AK, CANB, and NSW were measured, and flower length was found to be unimodal, with nearly identical ranges in Australian and New Zealand plants. Flower size variation in Australian and New Zealand Danhatchia specimens has two significant contributing components, inter-individual variation, and ontogenetic variation where flowers increase in size as they age. Dimensions previously recorded for the two species reflect upper and lower limits on the range of variation in flower size present in both New Zealand and Australia, respectively. Within herbarium material, 20% of flowers on New Zealand specimens, and 40% of flowers on Australian specimens exhibited signs of opening. There was no correlation between flower size and opening, as might be expected if the two species were both present in Australia and/or New Zealand. Neither the biogeographic context, pollination system, nor morphological evidence support Danhatchia australis and D. novaehollandiae as distinct species.

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‘Junk’ DNA and phenotypic evolution in Silene section Siphonomorpha

Genetics Research ◽

10.1017/s001667230700897x ◽

2008 ◽

Vol 90 (1) ◽

pp. 111-118 ◽

Cited By ~ 2

Author(s):

THOMAS R. MEAGHER ◽

DENISE E. COSTICH

Keyword(s):

Negative Correlation ◽

Sex Chromosomes ◽

Dna Content ◽

Nuclear Dna ◽

Size Variation ◽

Nuclear Dna Content ◽

Flower Size ◽

Phenotypic Evolution ◽

Genomic Evolution ◽

Dioecious Species

SummaryOne of the long-standing mysteries in genomic evolution is the observation that much of the genome is composed of repetitive DNA, resulting in inter- and intraspecific variation in nuclear DNA content. Our discovery of a negative correlation between nuclear DNA content and flower size in Silene latifolia has been supported by our subsequent investigation of changes in DNA content as a correlated response to selection on flower size. Moreover, we have observed a similar trend across a range of related dioecious species in Silene sect. Elisanthe. Given the presence of sex chromosomes in dioecious Silene species, and the tendency of sex chromosomes to accumulate repetitive DNA, it seems plausible that dioecious species undergo genomic evolution in ways that differ from what one might expect in hermaphroditic species. Specifically, we query whether the observed relationship between nuclear DNA content and flower size observed in dioecious Silene is a peculiarity of sex chromosome evolution. In the present study we investigated nuclear DNA content and flower size variation in hermaphroditic species of Silene sect. Siphonomorpha, as close relatives of the dioecious species studied previously. Although the nuclear DNA contents of these species were lower than those for species in sect. Elisanthe, there was still significant intra- as well as interspecific variation in nuclear DNA content. Flower size variation was found among species of sect. Siphonomorpha for petal claw and petal limb lengths, but not for calyx diameter. This last trait varies extensively in sect. Elisanthe, in part due to sex-specific selection. A negative correlation with nuclear DNA content was found across populations for petal limb length, but not for other floral dimensions. We conclude that impacts of nuclear DNA content on phenotypic evolution do manifest themselves in hermaphroditic species, so that the effects observed in sect. Elisanthe, and particularly in S. latifolia, while perhaps amplified by the genomic impacts of sex chromosomes, are not limited to dioecious taxa.

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Flower Size Variation in Rosmarinus officinalis: Individuals, Populations and Habitats

Annals of Botany ◽

10.1093/aob/mci041 ◽

2004 ◽

Vol 95 (3) ◽

pp. 431-437 ◽

Cited By ~ 59

Author(s):

J. HERRERA

Keyword(s):

Size Variation ◽

Rosmarinus Officinalis ◽

Flower Size

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Ovule and seed production patterns in relation to flower size variations in actinomorphic and zygomorphic flower species

AoB Plants ◽

10.1093/aobpla/plz061 ◽

2019 ◽

Vol 11 (5) ◽

Author(s):

Jun Mochizuki ◽

Tomoyuki Itagaki ◽

Yuta Aoyagi Blue ◽

Masaya Ito ◽

Satoki Sakai

Keyword(s):

Natural Selection ◽

Seed Production ◽

Size Variation ◽

Flower Size ◽

Symmetry Type ◽

Floral Symmetry ◽

Increase With Increase ◽

Ovule Number ◽

Ovule Production

Abstract Zygomorphic flower species tend to show lower flower size variation than actinomorphic flower species. Have these differences also brought an association in ovule and seed production that has arisen due to natural selection in these species? Flowers were collected from 29 actinomorphic and 20 zygomorphic flower species, and fruits were collected from 21 actinomorphic and 14 zygomorphic flower species in Miyagi and Aomori prefectures, in Japan. The coefficient of variations (CVs) of flower sizes, mean ovule sizes of flowers, ovule numbers of flowers and mean seed sizes of fruits were calculated. The CV of flower sizes was marginally different between the floral symmetry types; tending to be lower in the zygomorphic flower species than in the actinomorphic flower species. The CVs of mean ovule sizes and ovule numbers of flowers increased with increase in the CV of flower sizes in the actinomorphic flower species but not in the zygomorphic flower species. Mean ovule number of flowers tends to increase with increase in mean flower size in the actinomorphic flower species but not in the zygomorphic flower species. The degrees in variations in ovule size and number of flowers were influenced by the interaction of floral symmetry type and flower size variation, suggesting that floral symmetry also has brought an evolutionary association in ovule production by flowers.

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The Size of it: Scant Evidence That Flower Size Variation Affects Deception in Intersexual Floral Mimicry

Frontiers in Ecology and Evolution ◽

10.3389/fevo.2021.724712 ◽

2021 ◽

Vol 9 ◽

Author(s):

Avery L. Russell ◽

Stephanie R. Sanders ◽

Liam A. Wilson ◽

Daniel R. Papaj

Keyword(s):

Phenotypic Variability ◽

Size Variation ◽

Response Speed ◽

Flower Size ◽

Floral Mimicry ◽

Male Gametes ◽

Male Flowers ◽

Artificial Flowers ◽

Plant Pollinator ◽

Female Flowers

Mutualisms involve cooperation, but also frequently involve conflict. Plant-pollinator mutualisms are no exception. To facilitate animal pollination, flowering plants often offer pollen (their male gametes) as a food reward. Since plants benefit by maximizing pollen export to conspecific flowers, we might expect plants to cheat on pollen rewards. In intersexual floral mimicry, rewarding pollen-bearing male flowers (models) are mimicked by rewardless female flowers (mimics) on the same plant. Pollinators should therefore learn to avoid the unrewarding mimics. Plants might impede such learning by producing phenotypically variable flowers that cause bees to generalize among models and mimics during learning. In this laboratory study, we used partially artificial flowers (artificial petals, live reproductive parts) modeled after Begonia odorata to test whether variation in the size of rewarding male flowers (models) and unrewarding female flowers (mimics) affected how quickly bees learned both to recognize models and to reject mimics. Live unrewarding female flowers have 33% longer petals and have 31% greater surface area than live rewarding male flowers, which bees should easily discriminate. Yet while bees rapidly learned to reduce foraging effort on mimics, learning was not significantly affected by the degree to which flower size varied. Additionally, we found scant evidence that this was a result of bees altering response speed to maintain decision accuracy. Our study failed to provide evidence that flower size variation in intersexual floral mimicry systems exploits pollinator cognition, though we cannot rule out that other floral traits that are variable may be important. Furthermore, we propose that contrary to expectation, phenotypic variability in a Batesian mimicry system may not necessarily have significant effects on whether receivers effectively learn to discriminate models and mimics.

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