Sympatric Speciation
Have you ever wondered if new species can emerge without being separated by distance? Well, this is where sympatric speciation comes in. It's a type of speciation that doesn't rely on physical separation., it happens when a population diverges into a new species in the same geographic location. This is different from allopatric speciation, which occurs when populations are separated by a physical barrier. The causes of sympatric speciation can vary, but they often involve changes in behavior or genetics. Some examples of sympatiation include the emergence of different fruit fly species in the same location, or the development of different types of cichlid fish in the same lake.
What Is the Definition of Sympatric Speciation?
Have you ever wondered how new species are formed? Well, it happens when populations of a species evolve into distinct species due to different factors. This process is called speciation, and it involves one lineage splitting into two or more lineages.
Sympatric speciation is a type of speciation that happens when two groups of the same species are living in the same area but they no longer interbreed. This is different from allopatric speciation, which occurs when members of a population are separated by geography. Sympatric speciation is quite controversial, but many scientists believe it can happen due to changes in behavior or genetics. For instance, two different types of birds may evolve in the same area because one group changes its mating behavior, leading to a split in the population.
Allopatric vs. Sympatric Speciation: What Is the Difference?
Allopatric speciation and sympatric speciation are two important processes that lead to the formation of new species.
Sympatric Speciation Specifically Excludes Geographic Isolation
Have you ever wondered how new species are formed? Well, one way is through allopatric speciation. This type of speciation happens when two or more populations of the same species are physically separated from each other, either due to migration or a physical barrier like a mountain range or a river.
When populations are separated, they can no longer share genes, and over time, the differences in their DNA become more pronounced. This is because each group faces different environmental factors like climate, predators, and food sources, leading to changes in their genetic makeup. If the populations remain separated for a long enough time, these genetic differences can become so significant that they can no longer interbreed, resulting in new species. Check out Figure 1 below to see how this process works.
In contrast, sympatric speciation occurs even when populations are not physically separated. It is rarer than allopatric speciation and requires the formation of a reproductive barrier while members of the population are still in contact with each other. This process is illustrated in Figure 2 below.
As opposed to allopatric speciation, sympatric speciation is controversial because there must be enough evidence to show that the descendant species originated from a common ancestral species, that the group formed reproductive isolation, and that speciation was not caused by geographic isolation.
Additionally, allopatric speciation occurs more frequently in animals than in plants, while sympatric speciation occurs more frequently in plants than in animals. Plants can form polyploidy and reproduce asexually, while not many animals can tolerate the anatomical changes accompanying these processes. To reproduce, a tetraploidy animal needs to look for another animal of the same species but of the opposite sex that has also gone through polyploidy at random.
What Are the Causes and Some Examples of Sympatric Speciation?
Sympatric speciation requires the formation of a reproductive barrier that will restrict gene flow. How does a reproductive barrier form when members of the population live in the same geographical area?
The formation of reproductive barriers can be caused by polyploidy, sexual selection, and habitat differentiation. We will discuss these causes and cite an example of each.
Polyploidy
Another cause of sympatric speciation is sexual selection. This occurs when individuals within a population select mates based on specific traits, leading to the formation of distinct subpopulations with different traits. Over time, these subpopulations may become reproductively isolated due to their different traits, leading to the formation of new species.
One example of sexual selection causing sympatric speciation is the case of cichlid fish in African lakes. Male cichlids have a wide range of colors and patterns, and females tend to prefer males with certain. As a result, subpopulations of cichlids with different color patterns have formed within the same lake, with each subpopulation having distinct mating preferences. This has led to reproductive isolation and the formation of new species.
Finally, habitat differentiation can also lead to sympatric speciation. This occurs when subpopulations within a single geographic area adapt to different ecological niches within their habitat. Over time, these subpopulations become reproductively isolated due to their adaptations to different environments, leading to the formation of new species.
An example of sympatric speciation caused by habitat differentiation is the apple maggot fly. Originally, apple maggot flies laid their eggs on hawthorn trees. However, some flies began laying their eggs on domesticated apples, which had only recently been introduced to their geographic area. Over time, these flies adapted to the different environment of the apple tree, leading to reproductive isolation and the formation of a new species.
There are two forms of polyploidy:
Autopolyploidy: an individual has more than two sets of chromosomes that are all derived from a single species. Allopolyploidy: a fertile polyploid is produced from the asexual reproduction (e.g., self-pollination) of a sterile hybrid offspring of two different species.
The piggyback plant (Tolmiea menzisii) and the white sturgeon (Acipenser transmontanum) are natural autopolyploids. In modern agriculture, autopolyploidy--specifically autotriploidy (an autoploid with three copies of chromosomes) is used to produce seedless watermelons and bananas and sterile salmon and trout.
On the other hand, the wheat species Triticum aestivum is an example of an allopolyploid. It has six sets of chromosomes, two sets derived from three different parent species. The first instance of polyploidy–a spontaneous hybrid of a domesticated wheat species and a wild grass species that occurred over 8,000 years ago–eventually led to the emergence of the modern wheat species.
Sexual selection
Another example of sexual selection leading to sympatric speciation is the case of the Hawaiian cricket, Laupala cerasina. Male crickets on different islands have different courtship songs, and females prefer males with songs that are similar to their own. Over time, this has led to reproductive isolation and the formation of new species.
In addition to mate preferences, sexual selection can also be driven by competition between members of the same sex for access to mates. This is known as intrasexual selection. For example, male elephant seals engage in intense physical battles to establish dominance and gain access to females. This has led to the evolution of large body size and other traits that give males an advantage in these battles.
Overall, sexual selection can play a significant role in the formation of new species through sympatric speciation. Mate preferences and competition for mates can act as reproductive barriers that lead to genetic divergence and the emergence of new species over time.
Habitat Differentiation
Another example of habitat differentiation leading to sympatric speciation is the case of the white clover (Trifolium repens) and the yellow clover (Trifolium dubium) in Ireland. Both species can interbreed, but white clovers grow primarily in moist habitats, while yellow clovers grow in dry habitats. Over time, the populations became genetically distinct due to natural selection favoring traits that were better suited to their respective habitats. This eventually led to reproductive isolation and the formation of two separate species.
It is important to note that sympatric speciation is a complex process that can involve multiple factors acting in combination. For example, in some cases, habitat differentiation may be driven by sexual selection or vice versa. The exact mechanisms that lead to sympatric speciation can vary depending on the species and the ecological context in which they live. However, the key takeaway is that sympatric speciation can occur even without geographical isolation, and it can lead to the formation of new species through the restriction of gene flow.
Sympatric Speciation
What is sympatric speciation?
Sympatric speciation is a type of speciation that occurs when two groups of the same species live in the same geographical area, but no longer interbreed.
What is the difference between allopatric and sympatric speciation?
The main difference between allopatricand sympatric speciation is that allopatric speciation requires geographic separation, while sympatric speciation specifically excludes it.
What prevents speciation from occurring in sympatric populations?
The lack of reproductive isolation would prevent speciation from occurring in sympatric populations.
How does sympatric speciation occur?
Sympatric speciation occurs as a result of the formation of a reproductive barrier that will restrict gene flow. This can be caused by factors such as polyploidy, sexual selection, and habitat differentiation.
What is an example of sympatric speciation in plants?
As a reproductive isolation mechanism, polyploidy can lead to sympatric speciation. An estimated 80% of extant plant species descended from ancestors formed through polyploid speciation. An example of a polyploid is the wheat species Triticum aestivum, which has six sets of chromosomes, two sets derived from three different parent species.
