DNA sequencing and fossil records help an Imperial scientist piece together the evolutionary history of that most diverse of creatures: the beetle.
Ed Yong
Beetles are arguably the most successful group of animals on the planet, outliving the dinosaurs and out-diversifying all other animal orders. Alfried Vogler, Professor of Molecular Systematics at Imperial College, recently published the most comprehensive ever evolutionary tree of Coleoptera in the journal Science. Nature Network London talks to him about the keys to the beetle’s success.
Why are you interested in the evolution of beetles?
Well I’m generally very interested in the evolution of biodiversity and the great richness of species on earth. Given that a quarter of them are beetles, that’s a very important portion of that biodiversity. The differences between the beetles show the enormous inventiveness of evolution—that’s what fascinates me about them. I’ve always been interested in bugs. As a teenager, I became interested in collecting insects from around the house, like many entomologists do.
How many species of beetle are alive today?
If we only knew. People usually say about 350,000 but even that’s contentious. One of my colleagues who keeps a tally on this says that it’s more like 410,000. Many of them are described multiple times, many names disappear and there are many species described every year. It’s very dynamic and there could be anywhere between one million and ten million species that we don’t know about yet.
How did you look at the relationships between these species?
We took a selection of major beetle groups that covers about 80% of families. We compared DNA sequences from all the species, about 2,000 in all, and produced a comprehensive phylogenetic analysis for a very large proportion of the major groups.
What makes them so successful?
Beetles are ecologically diverse. The entire range of lifestyles, habitats and ecologies that you see throughout the insects, can also be seen in the beetles alone. They have a high propensity to acquire new habitats or niches and many of these lifestyles have arisen multiple times. So you have lots of lineages in different niches evolving independently, which adds up to a large number in total.
Take aquatic lifestyles—our phylogenetic tree shows 10 different transitions from land to aquatic habitats, which doesn’t happen in other insect groups. Predatory groups arise all over the place. Herbivorous groups arose multiple times and within those, you have great diversification to different parts of the plant. You have beetles living on the leaves, roots and flowers. You have pollen feeders, those that eat the dead wood, and those that eat the live wood. And all of these lifestyles have arisen multiple times.
Does your data refute any other theories?
One of the other major ideas linked their diversity to feeding on plants. Once angiosperms arrived, beetles co-diversified with them so that the more species of plants there were, the more beetle species there were. But now it turns out that most beetle lineages were already in place before the angiosperms arose. Some of them just jumped onto the plants and exploited them.
How old are beetle lineages?
We know from the fossil record and molecular clocks that many of the major lineages were around in the time of the dinosaurs. We know that from the fossil record and molecular clocks. We can work out when these lineages first arose and to our surprise, they were actually quite ancient.
Why are beetles so adaptable?
That’s something we’re struggling with but hopefully genome studies will answer that. The full genome sequence of the flour beetle Trilobium castaneum is coming out soon in Nature. With it, we could see what genes you find in beetles that you don’t in other groups. Or perhaps some genes are unique to particular groups of beetles. There’s a certain adaptability that may already be lain down in their genomes.
Ed Yong blogs at Not Exactly Rocket Science
