Ants Tell The Story Of Tropical Biodiversity

Researchers have studied ants to explain why biodiversity is higher in tropical regions compared to areas further away from the equator.

AsianScientist (Jun. 11, 2018) – A team of scientists at the Okinawa Institute of Science and Technology (OIST), Japan, has used ants as a proxy marker for explaining biodiversity in the tropics. Their work is published in Nature Communications.

For centuries, biologists have been confounded by the puzzle of why the Earth’s tropical regions are home to an enormous variety of plant and animal species compared to regions further away from the equator. One possible explanation for this observation is that higher latitudes cannot support high biodiversity because of a lack of sunlight and heat. Another theory is that increased solar radiation in tropical latitudes could result in higher mutation rates which drive greater diversity.

Attempts to study this puzzle of tropical biodiversity have involved comparing the number of species in several plant and animal groups, such as trees, birds and mammals, across distinct regions of the planet. But tallying species from Borneo to Belgium has yet to deliver concrete answers about why regional differences in diversity exist at all.

In the present study, a team led by Professor Evan Economo of OIST set out to address this discrepancy with ants. While most studies up to now have focused on vertebrates like mammals and birds, ants offer a global, closely related group to examine.

“[Ants are] found almost everywhere on the planet. They’re ecologically dominant and well-documented, at least for an insect group,” said Economo. “This makes them a good example of invertebrates to compare with other vertebrate groups.”

The researchers catalogued the global distribution of all 14,912 ant species, poring over more than 9,000 publications, museum databases and online repositories to define which ant species occur in various parts of the world. They also combined all the available genetic data and used computational models to infer a ‘tree of life’ diagram that shows the ancestral relationships between species.

Additional data were gathered from 500 extinct species of ants that had been identified from fossils preserved in amber or compressed in rocks. This allowed the authors to date ancestors of modern tropical and temperate ant species and gain insight into past levels of diversity and the latitudes at which they occurred.

These analyses revealed that the rate at which new species arise is highly variable, but is not higher near the equator. Rather, the researchers suggest that tropical areas have had a much longer time to accumulate the diversity we see today, and given enough time, the same could happen in other parts of the world.

“This new data from ants can help to test theories about large scale patterns in ecology,” said Economo.

The article can be found at: Economo et al. (2018) Macroecology and Macroevolution of the Latitudinal Diversity Gradient in Ants.


Source: Okinawa Institute of Science and Technology Graduate University; Photo: Benoit Guénard/University of Hong Kong.
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