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Secrets of Migrants: How does just one immigrant in a generation change an entire population?
In the process of gene flow among organisms, the role of migrants undoubtedly plays a crucial role. Gene flow, the movement of genes from one population to another, can have profound effects on the overall gene pool. Whether it is the evolution of nature or the impact of humans on the ecosystem, gene flow plays an indispensable role.
High levels of gene flow help reduce the genetic differences between groups and make them more similar, so that they can be considered a single effective group.
In some cases, the influx of genes from just one immigrant can change the genetic makeup of an entire population. For example, studies have shown that the influx of genes from just "one immigrant per generation" can prevent ethnic groups from diverging due to population drift. Of course, such changes not only involve the transfer of genetic material, but also include various external environmental factors.
Factors affecting gene flow
The rate of gene flow between different populations is affected by many factors. First, species mobility is key. Generally speaking, organisms with high mobility are better able to disperse between different environments. For example, animals are generally considered to have higher migratory abilities than plants. However, wind, water, or other media can also help plant pollen and seeds travel greater distances.
However, where gene flow is impeded, populations may be at risk of inbreeding, as measured by the inbreeding coefficient (F). In isolated island populations, such as Australia's black-footed rock wallabies, the rate of gene flow is low due to geographic isolation and their small population size, followed by high rates of inbreeding.
Gene flow, as an important mechanism for the distribution of biological genetic diversity, is of great significance to the survival and evolution of species.
Measuring gene flow
Scientists often measure gene flow indirectly using comparisons of gene frequencies that encode samples. In this case, the greater the genetic differences between the two populations, the lower the predicted gene flow rate. Using the island model's effective population size (Ne) and net migration rate per generation (m), scientists can measure the impact of gene flow.
The use of these formulas helps us understand that if there is only one immigrant per generation in a population, the inbreeding coefficient (FST) can be said to be 0.2. But in the absence of migration, this value quickly soars to 1, leading to fixation and complete differentiation.
The impact of external obstacles on gene flow
Hinders to gene flow may also come from various physical barriers. When gene flow encounters geographical or artificial barriers, geographical isolation occurs, leading to the formation of allogeneic species. The Great Wall, for example, has acted as a barrier to gene flow among vegetation in China, causing plants growing on different sides to develop genetic differences.
However, barriers to gene flow are not necessarily actual geographic barriers. In some cases, even species within the same range may have reproductive barriers that limit gene flow. These barriers may arise from different flowering times, the presence of dedicated pollinators, or even the social structure of humans.
Human intervention, such as ecosystem reconstruction and species relocation, may bring opportunities for genetic rescue for some endangered species.
The double-edged sword of gene flow
Gene flow may promote the adaptability of a population, or it may cause some negative effects. When gene flow improves the fitness of a population and introduces beneficial traits, this is undoubtedly a good thing for the survival of the species. However, adverse effects can occur when a species loses its uniqueness through the introduction of allogeneic genes.
For example, in urban areas, gene flow may allow species to win more resources, but at the same time cause ecosystem chaos. These phenomena tell us that gene flow is more complex than generally imagined.
In short, why can just one immigrant change the fate of an entire ethnic group? Does this mean that in the process of evolution, the impact of every immigrant cannot be underestimated?
