Plants incarnate “chameleons”, are they “forced” by humans?

  In the life-and-death struggle for survival, animals have evolved camouflage skills. So, do plants camouflage?
  150 years ago, scientists’ speculation that plants use camouflage to avoid predators has sporadic, but it has not been confirmed by rigorous experiments. Recent advances in color measurement techniques, animal senses, and other related fields have led to renewed enthusiasm for the classic evolutionary biology topic of biological color. In addition to animal studies, scientists have found evidence that plants may also use various camouflage strategies to defend against natural enemies.
  Plants disguised as “cheating” humans?
  ”Our understanding of biological color’s defense function almost all comes from animals, and the classic concepts written in textbooks, such as camouflage, vigilance, mimicry, etc., are almost always based on animals. However, in recent years, more and more evidences show that, These fascinating concepts are not exclusive to animals,” said Sun Hang, a researcher at the Kunming Institute of Botany, Chinese Academy of Sciences.
  In the animal kingdom, the body color of the birch moth is a textbook case. In the wet woods of England, covered with gray-white lichens, the gray-white birch moth individuals are well camouflaged in such an environment, and thus are more numerous than dark-colored individuals. But during the Industrial Revolution, when their habitat was obscured by black smoke, dark individuals gained better camouflage and their numbers reversed.
  As far as plants are concerned, the most well-known disguiser is the “stone flower” that looks like a stone. In my country’s Qinghai-Tibet Plateau, there are also many cases of plant camouflage, such as Viola serrata, Viola purpurea, and Viola serrata that have been studied by Sun Hang’s team. There are also cases in other parts of the world, such as spearwood in New Zealand and vanilla in North America.
  Since 2012, Sun Hang and Dr. Niu Yang of the Kunming Institute of Botany, Chinese Academy of Sciences, have been paying attention to camouflage plants when they are doing research on the formation and evolution of plant diversity on the Qinghai-Tibet Plateau and the Himalayas. “We started our research with Viola plants in the mountains, and noticed that many local people were digging fritillary, and sometimes they even sold us the bulbs they had just picked up. Of course, we also noticed the camouflage and leaf color of the fritillary. Mutation.” Niu Yang introduced.
  There are more than 100 species of Fritillaria in the world. Among them, Fritillary fritillary grows in the northwest of Yunnan in my country, as well as in western Sichuan, southern Qinghai and the line from Lhasa to Yadong in Tibet. Its bulb contains the plant alkaloid fritillary, which is the source of the medicinal herb fritillary.
  ”In some groups, the fritillary fritillary is a common green color; in other groups, they are integrated with the background, mostly gray-brown, and very hidden.” Dr. Niu Yang introduced, they initially speculated that the Similar to Viola, this camouflage may also be a defensive strategy against herbivores. But after several years of observation in many places, they found no clear evidence of animals feeding on thalassium fritillary.
  ”Because the body is rich in alkaloids, Fritillaria has a strong chemical defense, to a certain extent, it resists animal feeding. Why does the Fritillaria camouflage? This puzzled us.” Niu Yang said, later , they realized that the underground bulbs of Fritillaria fritillary have been excavated in large quantities for a long time, and this excavation itself may generate strong selection pressure. This also means that the camouflage of Fritillaria may be related to humans!
  Camouflage plants have “intelligence”?
  In order to further clarify this conjecture, the research team conducted a more in-depth study. They compared the differences in the evolution of camouflage strategies in animals and plants, and speculated on the factors that affect the evolution of camouflage in plants. This is not only a fascinating topic, but also related to the future relationship and fate of humans and plants.
  ”Fitillary is a commonly used Chinese medicinal material. Humans have used Fritillaria for 2,000 years, and the history of modern large-scale mining is also more than 80 years.” Niu Yang said that in order to assess the mining intensity suffered by each group, they The total amount of dried Fritillaria fritillary in the past 6 years was obtained from the grass-roots drug dealers in Sichuan and Yunnan, and the dry weight of the single-grain bulbs of each group was estimated. They were surprised to find that to get 1,000 grams of dry bulbs meant digging up more than 3,000 fritillary plants. Such selection pressures are not trivial.
  Niu Yang said that they obtained the potential fritillary yield through quadrat statistics and distribution area evaluation, and thus obtained the mining intensity of each group. At the same time, they found that the greater the mining intensity, the better the fritillary camouflage.
  Immediately afterwards, the research on the mystery of the color of the mother-of-pearl came to the fore. Niu Yang and his colleagues came to the alpine rocky beach again to collect the reflectance spectrum data of each group. According to the CIELAB color vision model specially designed for humans, they quantified the spectrum of plants and gravels, and calculated that there is indeed a difference in the body color of the sand fritillary between groups. Significant differences. Using this model, they also calculated how well the fritillary matches the rocky background of the habitat to provide a measure of the degree of camouflage.
  ”Background matching is to use its own color to blend into the background, making it difficult for diggers to find and camouflage.” Sun Hang said, considering that the pressure of digging may have changed in a long history, they also evaluated the degree of camouflage and the difficulty of digging. relation.
  Due to the difference in the landing place, some bulbs take only tens of seconds to dig; some grow in the stone crevices of tens of centimeters deep, and it takes several minutes or even longer to dig a bulb. In terms of value and time cost, digging They tend to give up and suffer less mining pressure. From practical experience, the more difficult it is to collect, the better the camouflage of the plants, and the “integrity” with the surrounding gray-brown stones; the easier it is to excavate the plants, the more they will maintain the green color of the whole body in a “big shape”.
  Is camouflage evolving due to human activity?
  There is a significant correlation between body color and survival of Trixonidum fritillary, and camouflage increases their survival probability. However, the process of “color change” still has many interesting natural mysteries.
  The relationship between light, eyes and objects affects human’s recognition of color. Camouflage is caused by anthocyanins and chlorophyll together, and the pigment variation is relatively simple. However, it remains to be explored how to adjust the proportion of pigments in different groups of Fritillaria, so as to maintain a realistic color tone.
  Although Fritillaria is “smart” enough, driven by interests, no matter how clever the camouflage is, it is difficult to escape the high-intensity search of the human eye. Through simulations, it was found that humans with trichromatic vision searched faster than animals with dichromatic vision.
  ”In addition, the roots of plants cannot move, which means that even with camouflage, its defense effect will be greatly reduced, because natural enemies will have more opportunities to locate these immovable targets through other clues and repeated learning.” Niu Yang introduced, The ability of animals to actively choose the best hiding place is also difficult for plants to master.
  These studies show that humans are influencing the evolution of wildlife in ways that none of us could have foreseen. It remains to be seen in what other areas humans are affecting the environment.