Vavilovian Mimicry: Role of Humans and Selection Pressure

Vavilovian Mimicry, Nikolai Vavilov’s theory, has seemed very fascinating to Longjiang Fan since the 1980s.  He learned about Vavilov’s ideas during his graduation.

Vavilov’s inheritance theory, antagonistic to Lamarckism, is in itself was a novel approach, to which Fan ambitions to continue as a priority research. After being appointed as crop scientist at Zhejiang University, Fan started his research continuing Vavilov’s idea.

Vavilovian Mimicry

One of the most festinating ideas among Vavilovian’s theory of inheritance was Vavilovian mimicry. Vavilov has presented this idea after observing domesticated crops, oat and rye, and their wild types phenotypically. He believes that the present-day domesticated crops were evolved from weeds.

According to Vavilov, crops modified themselves with time due to humans and environmental impact. These crops were naturally weeds, but to avoid weeded out by humans during cultivational practices have evolved wheat-like characteristics. These phenotypic characteristics helped them survive agricultural evolution and adaptation to crop domestication.

Vavilovian Mimicry and Advanced Genomics

Now with the advancement in genomics, Fan planned to analyze Vavilov’s mimicry through genetic analysis to understand the transformation mechanism of plants from weeds to cultivatable crops.

Fan chosen a native weed, barnyard grass (E. crus-galli), of China which transformed into a rice-like plant by mimicking its phenotypic characteristics. This was first reported in the early 1980s during its early lifecycle transformation.

Evolutionist Spencer Barrett from the University of Toronto has reported this mimicry, saying that the rice hand weeding has derived the weed plant to grow straight-up instead of spreading out giving it a rice-like appearance instead of weed. This makes the farmers skip them during weeding.

Fan started the research by collecting 328 samples of barnyard grass from rice fields in the Yangtze River Basin, the epi-center of China’s rice. And planted the seeds in the field as well as in the green-house to analyze their seedlings, whether mimic rice phenotype or not.

Along with the phenotypic analysis, scientists also sequenced the genome of each plant to create a phylogenetic tree. A group of researchers concluded that mimic and non-mimic genotypes have diverged about 1,000 years ago, and genomic analysis also showed evolutionary selection evidences in 87 genes, controlling plant architecture.

The research results also consistently supported the concept that by hand weeding, humans exerted selection pressures that stimulate the development of rice-mimicking varieties. Significantly, Vavilov’s predictions from a decade ago fit so well with these scientific analyses, says Evolutionist Manyuan Long at the University of Chicago.

Kenneth Olsen, a plant biologist at Washington University, Fans’s research partner says modern sequencing helped a lot in restudying Barrett’s work. The results were consistent with the previous theories, however, the idea of selection pressure on genes has yet not confirmed that they have a role in plant mimicry or not. Researches now continued their work to determine the effect of mimic genes and their role in plant phenotype.

Weedy Rice

Olsen also studied a rice genotype “weedy rice”, which has adopted several wild weed plant characteristics that are undesirable for farmers, being an aggressive competitor in fields. However, these are not wild species but are adapted once, to our agricultural environments. Therefore, this genotype of rice somehow also supports Vavilovian mimicry.