PubMed · 10287041
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J P Rutledge. 1988. Interior design: creativity within functional limits.. https://pubmed.ncbi.nlm.nih.gov/10287041/
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The orchid Dactylorhiza sambucina shows a stable and dramatic flower-color polymorphism, with both yellow- and purple-flowered individuals present in natural populations throughout the range of the species in Europe. The evolutionary significance of flower-color polymorphisms found in many rewardless orchid species has been discussed at length, but the mechanisms responsible for their maintenance remain unclear. Laboratory experiments have suggested that behavioral responses by pollinators to lack of reward availability might result in a reproductive advantage for rare-color morphs. Consequently, we performed an experiment varying the relative frequency of the two color morphs of D. sambucina to test whether rare morph advantage acted in the natural habitat of the species. We show here clear evidence from this manipulative experiment that rare-color morphs have reproductive advantage through male and female components. This is the first demonstration, to our knowledge, that negative frequency-dependent selection through pollinator preference for rare morphs can cause the maintenance of a flower-color polymorphism.
A novel application of image analysis technology to the semiquantitative determination of the strong metal-binding phases of hydrous ferric oxides and acid-volatile sulfides in muddy estuarine sediments is presented. Sediment cores were split in the laboratory, photographed in cross-section, and subsampled for solid-phase analyses. The images were processed using commercially available software packages. Concentrations of FeOOH and AVS were found to be linearly related to elementary color parameters (saturation and intensity, respectively) at corresponding points on the images. Spatially resolved information on metal-binding capacity can thereby be estimated from such images; selected depth profiles are generated as examples.