Speciation without geographic barriers

Context (TH): Researchers at IIT Bombay discover the role of environmental resources, genes and mating in species in the development of new species in the same area.

Speciation

Speciation is the process of formation and evolution of new species. The study challenges the traditional view of Allopatric speciation.
Allopatric speciation occurs in species isolated from each other by geographical barriers.
It has shed light on speciation in the absence of geographic barriers –> Sympatric speciation.

The researchers used a genetic-based model to investigate the factors that contribute to speciation when populations live in the same geographic area.
This theoretical study focused on a population of birds using simulated data. It focused on a physical trait of the birds – the beak size.

Credits: TH

Adaation in beak size to best utilise two types of food resources: nuts and flower nectar.
Birds with small beaks will be better at utilising resource nuts, while longer beaks are needed for utilising flower nectar as their resource.
It examined three aspects that encourage speciation: disruptive selection, sexual selection, and genetic architecture.

The “divide” can be created by non-uniform environmental resources in sympatric speciation.
Disruptive selection favours heritable differences in the population.
It ensures that the offspring of mating of individuals belonging to two different groups do not survive.

Sexual selection, on the other hand, is a type of natural selection driven by competition for mates.
It can lead to the evolution of elaborate traits that are attractive to potential mates.
A ‘bias’ towards a trait like feather colour can evolve, leading to sympatric speciation.
For example, consider a bird population with two types of feathers—blue and red. If a bias among the blue birds to only mate with their kind evolves, can lead to sympatric speciation in two distinct species.
Surprisingly, the researchers found that sexual selection based on special traits did not contribute to speciation in sympatry.
The study also acknowledges the possibility of lower fitness of the offspring due to sexual selection.

Researchers discovered that genetic architecture, or how genes control the trait under selection, was a crucial factor in sympatric speciation.
However, results are limited by the assumption that birds from the two groups mate without any bias and that this bias does not change with time.