What is sympatric speciation, and how does it occur?

Sympatric speciation is the process where a new species evolves from a single ancestral species while inhabiting the same geographic region.

In more detail, sympatric speciation is a type of speciation that occurs without physical barriers. The word 'sympatric' is derived from the Greek words 'sym' meaning 'together' and 'patra' meaning 'fatherland'. This is in contrast to allopatric speciation, where geographic isolation leads to the formation of new species.

Sympatric speciation can occur through several mechanisms. One of the most common is through disruptive selection, where certain genotypes have a selective advantage over others. This can lead to the formation of 'microhabitats', where members of the same species occupy different niches within the same area. Over time, these populations may diverge so much that they become different species.

Another mechanism is through polyploidy, which is particularly common in plants. Polyploidy is a condition where an organism has more than two sets of chromosomes. This can occur spontaneously or as a result of hybridisation. Polyploid organisms are often unable to breed with their diploid ancestors, leading to instant reproductive isolation and hence, speciation.

Sympatric speciation can also occur through behavioural isolation, where differences in behaviour lead to reproductive isolation. For example, if members of a species have different mating calls, those with similar calls may preferentially mate with each other, leading to reproductive isolation and eventually, speciation.

Sympatric speciation is a complex process and is still a topic of ongoing research. It challenges the traditional view of speciation as a process driven by geographic isolation, and highlights the importance of other factors such as genetic variation and selection pressures. Despite this, it is widely accepted as a key mechanism of evolution and biodiversity.