I recently stumbled upon a project featuring species with blue coloration and this sent me down a rabbit hole. I wanted to see which organisms were in my favorite color, pink! I’ve noticed an interesting pattern though: It tends to appear alongside yellow. The Primrose, Rosy Maple, Pink Prominent and Pink star moths are all pink and yellow.
There are a lot of pink flowers which don’t feature yellow but they do exist, with Rock Harlequins, Pinkladies and Pink everlastings being some examples.I even managed to find a sea slug, the Pink Sponge Verconia, that’s pink with a white and/or yellow stripe down its side.
Why is this color combination so common, especially in insects?
With how many species there’re, I’m sure there’re combinations of most possible colours (limited to how some colors are structural and not found on as many species).
Moth colour depends on which colours allow species to survive, there’re many flowers and leaves of yellow and red tones, I check The Primrose moth photos and it appears to be really into yellow Oenothora? I would say light pink is one of colours easily misseed when the moth is sitting on bark, it’s not obvious, but it’s quite close to light brown. Deilephila are not as easy to spot as their pink colouration seems to suggest. Pink being close to yellow which is one of the greatest colours to hide probably proves that point, most moths that seem flushy hide in their natural habitat very easily.
Checking I found this blurry, but a good shot that shows it next to the old leaf:
I also think they don’t need pink+yellow flowers, from the distance for birds that eat them they will likely look like part of the flower. Likely for many species those colours are part of disruptive pattern.
These are a wimpy example, look up the taxon for better photos, but Garden Pink-Sorrel (Oxalis latifolia) are pink petaled with yellow at the petal bases.
Purple flowers are easier to explain, in UV they’re very bright and insects see them from a distance, so quite a few spring-blooming plants change their flower colour after pollination, like in Lathyrus vernus where they turn blue from purple.
Same goes for pollen, yellow is what insects see as red.
Flowers with both colours will be high in contrast and attractive to pollinators.
So you might imagine Melampyrum nemorosum must be really bright. When searching found this article with a nice table to think about https://biozoojournals.ro/nwjz/content/v16n1/nwjz_e181102_Sanyi.pdf
The Schinia are very beautiful moths. Why Rosy Maple Moths have this color is odd, as they do not perch on flowers. I have never seen a Rosy Maple during the day to hypothesize why they are pink and yellow. None of their relatives are even close in color.
Rosy Maple Moths are pink and yellow because they blend in with red maple seeds (samaras). See http://jimmccormac.blogspot.com/2019/05/rosy-maple-moth-in-hiding.html?m=1
Common evening-primrose flowers start out yellow but the blossoms fade to pink, so the Primrose Moths blend in with them. I can’t explain some of the other moths though. In addition to the ones listed above, Chickweed Geometers and several Pyrausta moths are also pink and yellow.
Just some educated speculation without supporting research to cite…
Pink and yellow are the colors of many commonly produced secondary metabolites, in plants at least. And both are toward the longer-wavelength end of the (humanly-)visible spectrum. So in situations where displaying longer wavelengths is a selective advantage for an organism (whether for reasons of attraction or camouflage), enhanced production of pink and yellow metabolites is a likely outcome of natural selection over multiple generations.
I was thinking along the same lines and suspect the vast majority of plants already have the enzymes to make yellow and pink pigments as part of their normal life. The yellows (carotenoids) are part of light-harvesting complexes in photosynthetic membranes, and the purple-pinks (anthocyanins) are derivatives of flavonoids, important protective molecules with many functions in stress responses. It would be small steps from there to co-opting the same enzymes to add color to petals and fruits by tinkering a bit with the expression of genes already present in the genome during the co-evolution of flowering plants with animals reacting to those colors.
Well, that answers a question I had. The original wild radish, Raphanus raphanistrum, has yellow or white flowers. The cultivated radish, Raphanus sativus, has pink or white flowers. But R. sativus was derived from R raphanistrum! I was wondering how the cultivated version had acquired a pigment that was not present in its wild progenitor.
@annkatrinrose I followed a suggestion to use ivy leaves for laundry.
I presume saponins?
Why do plants contain ‘soap’?
Is it to deter - who would eat soap?!
Just some educated speculation without supporting research to cite…
Pink and yellow are the colors of many commonly produced secondary metabolites, in plants at least. And both are toward the longer-wavelength end of the (humanly-)visible spectrum. So in situations where displaying longer wavelengths is a selective advantage for an organism (whether for reasons of attraction or camouflage), enhanced production of pink and yellow metabolites is a likely outcome of natural selection over multiple generations.
I was thinking along the same lines and suspect the vast majority of plants already have the enzymes to make yellow and pink pigments as part of their normal life. The yellows (carotenoids) are part of light-harvesting complexes in photosynthetic membranes, and the purple-pinks (anthocyanins) are derivatives of flavonoids, important protective molecules with many functions in stress responses. It would be small steps from there to co-opting the same enzymes to add color to petals and fruits by tinkering a bit with the expression of genes already present in the genome during the co-evolution of flowering plants with animals reacting to those colors.
great explanations!
Another thing to remember is: Plants in comparison to animals are, for the most part, much more constricted in the phylogenetic adaptations they can enact as a response to environmental stressors, especially in large expanses that have since undergone a substantial slowing in the rates of evolution for most taxa. Hence, plants have had to make multiple uses for those metabolites that, if their evolution was sped up, they’d have used for single purposes. A good example are many taxa in Fabaceae found on South Africa’s Cape coast, which exhibit deep pink, purple or even blue petal lobes. The volatile hexylates and cyclicle carbons produced through mutual synthesis pathways ensure that the flowers are protected from harmful fungal attacks, and also give the flowers their bright sheen, together with the base colour of the primary by-product (anthocyanins) of the flower which serves to attract the desired pollinator (mostly Carpenter Bee’s)
These flowers also often contain a yellow-hued center near the base of the petals/ tepals. I might be clutching at straws here but I think that with Carotenoids and Beta-Carotenoids, these metabolites are usually concentrated as waste products from alcohol fermentation around the inner pith at the core of vascular tissues, which plants have brilliantly decided to express phenotypically as nectar guides on the inner flower surface with just miniscule changes to the alelle’s themselves.
So theoretically, you would not just find pink and yellow combinations common in nature, but purple-yellow, blue-yellow, and even black-yellow, although the latter might also contain structural arrangements to produce darker colours like crimsons and navy blue
