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Traits conserved across evolutionary time often provide compelling examples of key adaptations for a given taxonomic group. Tetradynamy is the presence of four long stamens plus two short stamens within a flower and is conserved across most of the roughly 4000 species in the mustard family, Brassicaceae. While this differentiation in stamens is hypothesized to play a role in pollination efficiency, very little is known about the potential function of the two stamen types. The present study sheds new light on this mystery using wild radish (Raphanus raphanistrum), a widespread and well-studied tetradynamous plant. We used data collected from slow-motion videos of pollinators visiting wild radish flowers to test three adaptive hypotheses (not mutually exclusive): (H1) short and long stamens are specialized for either feeding or pollinating; (H2) short and long stamens are specialized for different pollinator taxa; and (H3) the presence of short and long stamens increases pollinator movement and thus effectiveness. We find evidence consistent with hypothesis H3, but no evidence for hypotheses H1 or H2. Thus, tetradynamy may be an adaptation for generalized pollination, enabling effective visits by the variety of pollinators visiting most species of Brassicaceae.
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Rapid evolution of a family‐diagnostic trait: artificial selection and correlated responses in wild radish, Raphanus raphanistrum
Summary The mechanisms underlying trait conservation over long evolutionary time scales are poorly known. These mechanisms fall into the two broad and nonmutually exclusive categories of constraint and selection. A variety of factors have been hypothesized to constrain trait evolution. Alternatively, selection can maintain similar trait values across many species if the causes of selection are also relatively conserved, while many sources of constraint may be overcome over longer periods of evolutionary divergence. An example of deep trait conservation is tetradynamy in the large family Brassicaceae, where the four medial stamens are longer than the two lateral stamens. Previous work has found selection to maintain this difference in lengths, which we call anther separation, in wild radish,Raphanus raphanistrum.Here, we test the constraint hypothesis using five generations of artificial selection to reduce anther separation in wild radish.We found a rapid linear response to this selection, with no evidence for depletion of genetic variation and correlated responses to this selection in only four of 15 other traits, suggesting a lack of strong constraint.Taken together, available evidence suggests that tetradynamy is likely to be conserved due to selection, but the function of this trait remains unclear.
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- PAR ID:
- 10443348
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- New Phytologist
- Volume:
- 239
- Issue:
- 6
- ISSN:
- 0028-646X
- Format(s):
- Medium: X Size: p. 2382-2388
- Size(s):
- p. 2382-2388
- Sponsoring Org:
- National Science Foundation
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{"Abstract":["Traits conserved across evolutionary time often provide compelling\n examples of key adaptations for a given taxonomic group. Tetradynamy is\n the presence of four long stamens plus two short stamens within a flower\n and is conserved across most of the roughly 4000 species in the mustard\n family, Brassicaceae. While this differentiation in stamens is\n hypothesized to play a role in pollination efficiency, very little is\n known about the potential function of the two stamen types. The present\n study sheds new light on this mystery using wild radish (Raphanus\n raphanistrum), a widespread and well-studied tetradynamous plant. We used\n data collected from slow-motion videos of pollinators visiting wild radish\n flowers to test three non-mutually exclusive adaptive hypotheses: 1) short\n and long stamens are specialized for either feeding or pollinating, 2)\n short and long stamens are specialized for different pollinator taxa, and\n 3) the presence of short and long stamens increases pollinator movement\n and thus effectiveness. We find evidence consistent with hypothesis three,\n but no evidence for hypotheses one or two. Thus, tetradynamy may be an\n adaptation for generalized pollination, enabling effective visits by the\n variety of pollinators visiting most species of Brassicaceae."],"TechnicalInfo":["# Data from: Testing adaptive hypotheses for an evolutionarily conserved\n trait through slow-motion videos of pollinators The data contained in\n these files was generated from close observation of slow-motion video\n footage by the same experimenter for each variable. ## Description of\n Files ### MainData.csv Data related to slow-motion video analysis,\n including plant information, anther and stigma contact, and number of\n movements Missing data are indicated by "NA" #### Basic Video\n Info in Columns A:F * VideoID: unique individual video identifier *\n PlantID: unique individual plant identifier with the following format -\n "PopulationCode FamilyCode-Replicate" * PopulationCode: BINY =\n natural population, Sep = separation-selected, Exsertion =\n exsertion-selected * FamilyCode: unique 3-5 character code for a given\n maternal seed family * Replicate: individual plant number between 0 and 9,\n where replicate 0 is indicated by the lack of a hyphen and number * Date:\n date of observations * Year: year of observations * Pollinator: taxa of\n visiting pollinator * VideoLength: total length of visit in 1/8 real-time\n seconds #### Feeding Info in Columns G:N * G:K are binary columns in which\n 1 indicates the visit included foraging in the given category, 0 indicates\n lack of foraging, and ? indicates uncertainty ("Short" = short\n stamen anthers, "Long" = long stamen anthers) * L:N summarize\n the info from G:K in different ways * Foraging: whether the visit included\n foraging on nectar, pollen, or both * Feed_All: for visits including\n pollen-foraging, whether foraging was on short stamen anthers, long stamen\n anthers, or both * Feed_Bin: same as Feed_All but groups "Long"\n and "Short" into "One" #### Contact Info in Columns\n O:AM Columns have the following format:\n "ResponseVariable_BodySection_FlowerPart" * ResponseVariable is\n what kind of contact is being recorded and can take three values: * sec:\n duration of contact in 1/8 real-time seconds * bin: binary contact, 1 =\n contacted and 0 = not contacted * n: count of body sections contacted\n (sums binary contact with Legs, Ventral, Side) * BodySection is the part\n of the pollinator body contacted and can take four values: Ventral, Side,\n Legs, or Total (sum of prior 3) * FlowerPart is the part of the flower\n contacted by the pollinator and can take 4 values: S (short stamen\n anthers), L (long stamen anthers), Stigma, or Anthers (both short and long\n stamen anthers) #### Movement Info in Columns AN:AR * Between_Moves: # of\n movements from feeding on one stamen to another * Within_Moves: # of\n movements within stamen types, combining movements from long to long\n stamen ("Long.Long_Moves") and movements from short to short\n stamen ("Short.Short_Moves") * Total_Moves: total # of movements\n from one stamen to another ### DyeSwab.csv Data from small preliminary\n test in which 3 bees were swabbed with gelatin cubes after visiting\n flowers with short and long stamens marked with different colors of\n fluorescent dye. * ID: unique individual bee identifier * BodySection: the\n body section swabbed * NParticles: count of dye particles contained in\n gelatin swab * StamenType: type of stamen matching the color of counted\n particles ### Final_Analysis_Dryad.R R script of all analyses used in the\n paper. * Details provided as comments within script. * The script was run\n in RStudio running R v. 4.4.2."]}more » « less
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