In fact, researchers say the study explains the diversity not only of beetles, but of the many insects that have evolved to chew, suck and otherwise devour flowering plants. Plants and the insects that eat them are two groups whose diversity demands explanation, because together they make up more than half of all known species. Here was this huge, underexploited resource, the flowering plants. Insects that were able to evolve to make the shift to eat them, enjoyed the fruits, so to speak. In fact, it may be no coincidence that the flowering plants are themselves so diverse, because the beetles and other insects attacking them might have provided pressure for the evolution of new, better-defended plant species.
More plants spawn more beetles.
More beetles may spawn more plants, as well as more parasites on beetles or more predators, which in turn spawn creatures that eat those predators and on and on. This is one of the best pieces of data we have to show that what we all believe really is so. The magnitude of the work is astonishing. Farrell constructed an evolutionary tree including more than 100 species representing the many kinds of beetles that eat plants. He used DNA sequence data and data on the shapes of beetle species to determine which species are most closely related and which are not.