Ants that conquered the world

Ants that conquered the world

It's an ant's world

Ants that conquered  the world

You can find big-headed ants in almost every tropical forest. But did you know that these little beings survived some of the major evolutionary changes to be there, reports TS Channesh

Did you know that among all the ant types in the world, about 10 per cent of them are close relatives?

Incidentally, they all belong to just one genus out of 323 – Pheidole. Commonly known as big-headed ants, Pheidole genus is widespread and ecologically dominant. Derived from the ant subfamily of Myrmicinae, Pheidole genus first evolved in America. A conspicuous component of terrestrial biodiversity, these ants are the most diverse group amongst all the groups of social insects. They occupy all major terrestrial habitats except the tundra and the wetlands and exhibit a wide range of social behaviour and work in tandem with other organisms.

History of the genus

The genus Pheidole was first erected by John Obadiah Westwood, a leading 19th
century British entomologist. He based the genus on the species of Atta
providens, from India, which is currently called Pheidole providens. John was the
inaugural holder of the Hope Chair of Entomology at the University of Oxford, when it was established in 1863.

He was a part of the original group of founding members of the then Entomological Society of London in 1833 and was a prolific author in modern insect
classification. He published his work on a large group of insects and even illustrated his own works along with others using his artistic talents.

Pheidole ants fill all the niches in ecosystems, ranging from rainforests to deserts. The family is so diverse that even today, researchers don’t have a global perspective of the number of Pheidole ants spread across the planet.

Due to their global ubiquity, these ants offer ecologists a broad view into a wide range of ecosystems. They serve important roles in soil aeration, nutrient cycling and dispersal of plant seeds.

Undoubtedly, they are our evolutionary teachers. Additionally, their social behaviour interests many researchers.

Recently, scientist Evan Economo and his team at the Biodiversity and
Biocomplexity Unit of University of Michigan compared gene sequences of 300 species of Pheidole from around the world. They then sequenced their DNA to determine the genetic similarities and reconstructed the entire family tree of Pheidole genus.

In a parallel effort, they also scored academic literature, museums and large databases to aggregate data on 1200 species of Pheidole and created a range map for every species. This may seem like a lot of effort for a group of seemingly inconsequential creatures, but in fact, many ecologists use ants to better understand the evolution and the terrestrial ecosystems ants inhabit.

The evolution of this particular ant genus is a successful story, both in terms of ecology and species diversity. Here’s why: the end result of the extensive research published in the Proceedings of the Royal Society, shows that the genus Pheidole evolved the same way twice.

When you compare the Pheidole evolutionary tree with the genus maps, you might get the picture of mass olonisations of varied species across the continents. But if that were the case, the study would find species that are close relatives living in different
continents. Instead, it found that the genus was split into two main groups of evolutionary relatives: one in the New World, or the America, and one in the Old World, or Europe, Asia, Africa, and Australia.

Independent evolution

The study said that the new world and old world are almost independent of each other, with the Pheidole species first evolving in the new world. Then, one of the ants colonised the old world and created a line of species there. The study also deduced the dependence of these ants on the climate. Ants of both the worlds showed dominance in warm and wet climates, suggesting evolution repeated itself and is to some extent, deterministic.

This study also proved that these ants didn’t thrive due to a random chance but they colonised and thrived in huge numbers thanks to their surviving abilities. They possessed unique characteristics that gave them an edge over other animals.

The ant study is an extensive, information-rich resource. From this resource, researchers hope to find out how the ants forage for food, build their nests and thrive in their varied local environments. Knowing these habits would help understand whether Pheidole is the best at surviving, or whether its environment can simply support more ant species.
Many recent studies have also made an attempt to find ways of handling these diverse species of ants. But the astonishing fact remains that these ants have found a space in every corner of the terrestrial ecosystem, surviving all odds and are the perfect representation of the Earth’s ecosystems.

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