Examples of Gene Flow in Plants and Animals

Gene flow can occur among plants in a wide variety of ways.

• Pollinators from a population of flowers on one side of a river transport pollen to the flowers on the other side of the river, producing floral offspring.
• Pollen from trees is blown far, far away to a completely separate group of trees and pollinates their flowers, producing trees with genetic characteristics of each population.
• Seeds and pollen from conifers on one side of a gulch are blown high into the air, eventually reaching and pollinating trees on the other side of the gulch.
• Fruit in the cucurbit family (cucumbers and most squash) must be pollinated by bees. If a bee carries pollen from one variety of squash or cucumber to another (within the same species), that will result in hybridization.
• If you save seeds from a squash or cucumber plant and the resulting fruit does not look like the fruit from the original plant, that is the result of gene flow.
• A farmer that wants to produce a particularly gene resistant variety of tomato, corn or other crops will use gene flow to cross plants together based on specific characteristics. This is called hybridization.
• Modern grains, like the durum wheat that is used to make bread, pasta and other flour-based food products, were developed through a hybridization process.
  
• Lager beer yeast (Saccharomyces pastorianus) is the result of gene flow (hybridization) between two other types of yeast, one of which has a higher level of cold tolerance than the other. The hybrid variety is more well-suited to fermentation than the original types.
• When people deliberately bring in plants that are non-native, they can end up starting the gene flow process that allows invasive species to evolve. Gene flow will occur between new plants and existing ones, often strengthening existing plants so they become harder to control or creating hybrids that become invasive.
• As the strongest genes survive and cross, species that are resistant to herbicide can develop. When this occurs, it can be difficult (or impossible) to curb the spread of unwanted plants, such as weeds.
• When the plants that grow back on previously damaged land through secondary succession are different from what was originally there, the change can be a result of gene flow.

There are many gene flow examples in the animal kingdom.

• Blue-eyed people from Sweden move to a small town in Mexico where people all have brown eyes. When they mate, some of their children now have blue eyes.
• Some birds with shorter beaks enter into a population of birds with much longer beaks, resulting in the hatching of birds with medium-sized beaks.
• A Maine coon cat is brought to an island where only wild tabby cats live. After mating with other cats on the island, some of the kittens have bushy tails and tufted ears.
• A bunch of women from West Africa, where malaria is present, mate with a group of Europeans. Their children are less susceptible to contracting malaria due to the presence of antibodies from their West African mothers.
• Rhinos from one herd move to a new area and breed with rhinos of a completely different herd.
  
• A man with very dark skin moves to a remote village in Eastern Europe, where most people have light skin. Their children and grandchildren show evidence of this genetic flow when some are born with dark skin.
  
• Several red foxes move into and mate with a silver fox population.
• Two lion prides meet in the Savannah and end up procreating, introducing genetic diversity to each tribe.
• Red parrots are brought on an expedition to a remote section of the jungle with only blue parrots, introducing color variation into the gene pool of jungle parrots.
• Brown beetles enter into a community consisting solely of green beetles, creating offspring with greater color diversity.
• Interbreeding occurs due to the migration of tall members of an African tribe to an area of South America where people are much shorter, making possible new combinations of genetic traits, including variations of skin color and height.
  
• A population of moths with a high frequency of white alleles enters a population of darker-colored moths. Over time, more and more white moths are born as a result.
• Tigers with enhanced sensitivity in the dark mate with a group of tigers with less sensitive eyes, allowing a greater population of tigers with enhanced eyesight to be born after a few generations.

Gene flow, which can also be described as migration, is a common occurrence with both plants and animals. It occurs when alleles or genes are successfully transferred from one population to another population. It can occur naturally or intentionally. Gene flow can take place in several ways.

• When wind causes the dispersal of plant spores or seeds to a new area, they may cross with other plants already in that area to form new types of plants.
• Gene flow also occurs when bees carry pollen from one plant to another.
• When botanists hybridize plants, they deliberately cross different varieties or species to create a new plant. This is referred to as selective breeding.
• When people move to a new location, meet partners and have children, that is also an example of gene flow.
• The same occurs with non-human animals and their offspring.

Gene flow can shape and change ecosystems and species, which makes it very important to understand both for those who are interested in nature and for those who are interested in science. If you find this topic to be interesting, expand your knowledge of how genetics works by reviewing some examples of genotype and phenotype. From there, you may want to move on to explore some examples of homozygous genes.