Why the World Is Inordinately Fond of Beetles

A study attributes the insects' diversity to their evolutionary hardiness.


[T]he great British biologist and atheist JBS Haldane once said, when asked whether studying biology had taught him anything about the Creator: "I'm really not sure, except that He must be inordinately fond of beetles." (The Independent)

It's an understatement to say that beetles come in many varieties. They account for nearly a quarter of all described species. A quarter. Imagine a roll call of living organisms: sunflower, hammerhead, E. coli, beetle. Chestnut tree, carpenter ant, human, another beetle. The atheist Haldane didn't really believe that beetles' incredible diversity could be attributed to the Almighty. But neither could he have offered a thorough scientific explanation.

Now, a study in the journal Science offers an explanation of why we have so many species of these insects, and it rejects a couple of alternative explanations. Evolutionary staying power and a willingness to specialize seem to account for the abundance of beetle species, the new research suggests.

According to one of the now rejected theories, beetles rose to numerical prominence by riding the coattails of another group of organisms. Angiosperms, or flowering plants, greatly multiplied during the Cretaceous period, which began about 145 million years ago. As this theory had it, beetles—which have existed for about 285 million years—were a relatively small group of species until the angiosperms exploded onto the scene, and beetles then diversified by finding numerous ways to feed on the suddenly more numerous plants.

But it turns out that beetle diversity predates the rise of the angiosperms. Alfried P. Vogler of Imperial College London and his colleagues studied genetic differences among 1,880 beetle species and constructed a sprawling family tree that connects all groups of living beetles. They found that more than 100 branches of the tree—branches on which many of today's beetles sit—sprouted from their evolutionary trunk long before the Cretaceous period began.

That finding, the researchers conclude, "suggests that beetle species' richness is due to high survival of lineages and sustained diversification into a variety of niches." In other words, beetles are old, they've successfully exploited new ecological niches at every opportunity during their long history, and they've been evolutionarily hardy enough to keep branches of their family tree from being lost to extinction. That adds up to a lot of beetles.

Footnote: I read this Science study mainly because its title reminded me of the famous "fondness of beetles" quotation, which I was then moved to look up. I did a bit of Googling to find it in the Independent, attributed to Haldane. (The quote also has been attributed by various sources to Charles Darwin, among others.) I'd welcome reader input on the quip's primary source.

A final thought: The study reminded me of another beetle I like (photo courtesy of Amie Hsia).