Study shows how new species develop without geographic barriers

The evolution of life on Earth from approximately 3.5 billion years ago to the present day has shaped the planet's biodiversity. It involves the transition from organic molecules to single-celled organisms, to multicellular organisms, and finally, to complex life forms (such as mammals and birds). Still, how new species come into existence remains a mystery!

A new study by scientists at the Indian Institute of Technology Bombay (IIT Bombay), Mumbai, published in NPJ Systems Biology & Applications, has shed light on the process of speciation, meaning the formation of new species, in the absence of geographical barriers. Traditionally, it is believed that speciation occurs largely when populations of a species become separated from each other by geographic barriers such as mountains or water bodies. This is called allopatric species. However, new IIT Bombay research shows that speciation can occur even when populations remain in the same area without geographic barriers. This method of speciation is called sympatric speciation.

“While there is ecological evidence in favour of this (sympatric) hypothesis, there is no experimental evidence. And in the absence of laboratory models to study sympatric speciation, it is difficult to understand it as a process. The motivation of our work is to understand how the environment and underlying genetics can interact to lead to sympatric speciation and to design biologically plausible experiments,” commented Professor Supreet Saini, Professor, Department of Chemical Engineering at IIT Bombay and DBT/Wellcome Trust (India Alliance) Fellow and lead researcher of the study, as the inspiration behind this study.

Researchers use genetic-based models to examine the factors that contribute to the origin of species when populations stay in the same geographic area. This theoretical study focuses on bird populations using simulated data and specifically looks at how three aspects that encourage speciation, namely, disruptive selection, sexual selection and genetic architecture, help drive and maintain sympatric speciation. How to play a role.

disruptive speciation

“In sympatric species, “splits” in populations can be created due to non-uniform resources present in the environment, and geography has no role here. This is called ecological disruptive selection,” said co-author Pavitra Venkatraman, PhD student. and Prime Minister Research Fellow at IIT Bombay, explains.

In other words, disruptive selection is a process by which individuals with extreme characteristics have higher fitness than individuals with intermediate characteristics.

Pavitra further adds, “Disruptive selection is essential for speciation to occur in sympatry because it (a) supports hereditary differences in populations, and (b) ensures that mating of individuals belonging to two different groups The child born does not survive. “These two factors are extremely important for maintaining biodiversity in sympatry.”

In this study, researchers focused on one physical characteristic of birds – beak shape. Birds in the population had to adapt the shape of their beaks to best use two types of food resources, A (e.g., nuts) and B (flower nectar). Birds with shorter beaks will make better use of resource A, while birds with longer beaks will be more efficient at using resource B.

role of sexual selection

Sexual selection, on the other hand, is a type of natural selection driven by competition for mates. This may lead to the development of a wide range of traits that are attractive to potential mates. In this study, researchers looked at how female mating preference, based on the intensity of a male's trait (unique character), may play a role in speciation.

“Sexual selection is thought to be the main, or often, the only driver of sympatric speciation. Essentially, it was thought that some members of a population could develop a 'bias' towards a trait such as feather colour, and differences in this bias Sympathy can lead to speciation. For example, consider a bird population where there are two types of birds – blue and red. If a bias develops among blue birds to mate only with their own species, then sympatric speciation This would happen because the red birds do not mix their genes with the blue ones,” explains Pavitra.

In other words, this could lead to populations with different blue and red traits.

Pavitra questions, “The flaw in this hypothesis is that unless there is a fitness benefit, there is no basis for such a bias to evolve. In other words, a blue bird will mate only with blue birds.” Why sexual intercourse leads to fewer partners is not clear.”

The researchers then included the bird's ability to utilize resources in the environment into their model. Surprisingly, the researchers found that sexual selection based on particular traits did not contribute to sympatry in speciation. Instead, they found that preference for mates based on a relevant trait that helped them better utilize environmental resources (in this case, beak size) was the driving force behind speciation. The study also acknowledged the possibility of lower fitness of offspring due to sexual selection.

Genetic architecture plays an important role

Furthermore, the researchers found that genetic structure, or how genes control a trait under selection, was an important factor in determining the likelihood of sympatric speciation. If the genetic structure allows for change in beak shape, a new species may evolve even with a weak role of disruptive selection.

Professor Saini explained about the limitations of the study, “In our model, we assume that birds from both groups mate without any bias and that this bias does not change over time. This may not be true in natural populations. , where biases based on beak shape are expected to evolve. It is also possible for birds of both groups to have evolved with different markers that help them distinguish their “species” from the other.”

Nevertheless, this study provides valuable information about the conditions and mechanisms that can lead to sympatric speciation. It challenges the traditional view that speciation can only occur in geographic isolation and highlights the importance of genetic architecture and ecological selection in driving the formation of new species.

“A major part of our research effort is to take lessons from theory and design experiments to understand how reproductive barriers evolve between members of a population in sympatry. Towards this end, we work with yeast to demonstrate and establish a laboratory model for studying speciation in sympatry,” says Professor Saini, indicating the way forward.

By unraveling the mysteries of species formation, scientists are gaining a deeper understanding of the incredible diversity of life on our planet and the processes that generate it. By demonstrating how sympatric species formation can occur, even with relatively low levels of disruptive selection, the researchers have provided a framework for future experimental studies on biodiversity. This knowledge can open new avenues for research and help scientists better understand the mechanisms behind biodiversity on Earth. With the imminent threat of climate change, perhaps it can also shed light on the effects of climate change on biodiversity more broadly.

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