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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 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.

Findings of study

  • 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.

Speciation without geographic barriers - PMF IAS

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.

Ecological disruptive selection

  • 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.

Role of sexual selection

  • 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.

Genetic architecture

  • 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.
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