Examples Of Sympatric Speciation

Evolution is defined as the change in genetic composition of a population over successive generations (Urry 365). In some cases one part of a population will evolve so completely that it can no longer interbreed with the rest of the population. This reduction of gene flow, the movement of genes between populations, is known as speciation. There are four main types of speciation: allopatric, peripatric, parapatric and sympatric (“Sympatric Speciation” 1). Allopatric, peripatric and parapatric speciation all occur when a certain geographical isolation is put in place, this can be a river, desert, mountain range or a large distance between the populations. This geographic barrier leads to reduced gene flow between different groups within the

This can be preference in habitat, food or mating techniques (Urry 425). An example of this is the apple maggot fly. First these flies exclusively laid their eggs on the leaves of the hawthorn plant. However, when Europeans began to immigrate to America they brought domestic apples on which the flies also began to lay their eggs on. This trend continued because the female flies chose to lay their eggs on the fruit they were born and grew up on. While the male flies searched for a female fly that preferred to mate on the type of fruit they grew up on, either the hawthorn or the apple. This means hawthorn flies began to solely mate with hawthorn flies while apple flies only mated with apple flies. This differentiation between hawthorn flies and apple flies lead to a reduced gene flow between to the two groups. After many years of reduced gene flow, certain genetic evolutions occurred allowing scientist to distinguish between the two species (“Sympatric Speciation” 1). Despite this example, sympatric speciation by behavioral preferences is extremely rare and difficult to achieve and prove to be

Polyploidy is when an organism has more than twice the haploid number of chromosomes. The process of sympatric speciation begins when an offspring is born diploid, meaning it has twice the haploid number of chromosomes. For example, the common fruit fly ordinarily has eight chromosomes, whereas a diploid fruit fly has sixteen chromosomes. These organisms can then have offspring that are tetraploid and so on. It is impossible for organisms with different amount of chromosomes to mate with each other; a diploid organism cannot mate with a tetraploid organism, which creates reproductive isolation and in turn leads to evolution (Coyne 1).Isolation due to polyploidy is more common in plants than animals because plants can reproduce asexually while animals most often cannot. This makes it easier for a diploid to reproduce because instead of finding a polyploidy of the opposite gender to mate with, a polyploidy plant can simply reproduce with itself. Reproductive isolation due to genetic differences leads to reduced gene flow between the different genetic species and therefore sympatric speciation