The Evolution of Bees

“The evolutionary history of bees in time and space” Current Biology, 27 July. 2023 https://www.cell.com/current-biology/fulltext/S0960-9822(23)00912-0#secsectitle0015

As flower pollinators, bees play a crucial role in multiple biomes (plant and animal communities). However, very little is known about their origin. Up until now, 200,000 species have been discovered over all the continents except Antarctica. The extensive use of molecular data (DNA or protein sequences) to infer relationships among organisms and create evolutionary timelines has helped expand our understanding of the evolution of bees and flowering plants. This study revealed new insights into both the origin of bees and their colonisation of different regions. Based on these results, we can understand the reasons behind the current geographical distribution of bees in the world.

This study discovered that bees originated in Western Gondwana (The southern half of the Pangean supercontinent; Africa and South America today, as seen in the image below) due to the dry environments and temperate climates (warm, moderate-rainfall regions), which were favourable to them. The bee population began to rise in the Early Cretaceous period (145 million to 100.5 million years ago).

180 million years ago, when South America and Africa separated, two important bee families were also split up and ancestors of certain bee species were restricted to South America. This helped to diversify the range of angiosperms (flowering plants) in South America owing to its long-lasting interdependence with bees.

The separation of Gondwanaland and the Indian subcontinent and its subsequent northward drifting significantly sets back our previously inferred arrival time of bees in this region by millions of years. The lack of early bee colonisers in India justifies the limited understanding of angiosperm diversification in this region. Theories suggest that bees did not settle in the Indian subcontinent until the Eocene (55.8 - 33.9 million years ago).

All surviving bee families have diverged from each other and were present in at least one of the three southern continents by the end of the Cretaceous (145 million to 66 million years ago). The northern hemisphere began getting colonised by bees long after, in the late Cretaceous.

The Cretaceous was followed by the Paleocene and Eocene periods, in which the climate was much warmer than the Earth is today. These climatically favourable periods allowed bees to expand their ranges northward from Africa.

After the Cretaceous, India also began to shelter numerous tropical forests, and the arrival of bees during the Eocene helped diversify the local flora and fauna.

Summarised by Saisha Sikka

Works Cited:

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