Butterflies, moths arrived before flowering plants

At the start of my species diversity course, I tell students pursuing my university’s Evolution and Ecology degree that we aim to understand how evolution has generated the diversity of life we observe today.

Survival of the fittest; Darwinian processes? Right. Velociraptor dinosaurs, which lived 75 million years ago, shred prey with their teeth and claws. Feathers allowed them to fly.

But it’s not that simple. Therein lies a common misconception about evolution.

Feathers likely first appeared in a group of dinosaur species. Those feathers, modified scales, kept the dinosaurs warm. Flight, made possible by the feathers, came later and before the first birds appeared.

The late evolutionary biologist Stephen Jay Gould termed such traits exaptations: They appeared in response to one selective pressure (staying warm) and then changed in response to another (flight).

This month, Timo van Eldijk and colleagues described a similar situation in the evolution of butterflies and moths. Their work appeared in the journal Science Advances.

Schoolchildren and other gardeners enjoy planting and observing butterfly gardens. Colorful butterflies flutter around and land on equally bright and colorful flowers. The butterflies sip nectar from flowers. They also transfer pollen among flowers.

What’s not to like about this textbook example of nature in harmony?

But how did butterflies and flowering plants get to this point?

Fossil records have suggested that nectarsipping butterflies appeared soon after the first, simple, flowering plants appeared. Flowers became much larger and more colorful once butterflies and other pollinating insects such as bees appeared.

The data of van Eldijk and his colleagues suggest an alternative interpretation.

Painstakingly examining organic debris from a thousand-footdeep core of German soil, van Eldijk and his colleagues discovered 200-million-year-old fossilized butterfly wing scales.

Butterflies and moths comprise the insect order Lepidoptera, literally the “scaled wing” insects.

Butterfly scales — then and now — consist of chitin, the same stuff of insect exoskeletons or “shells.” Chitin fossilizes readily.

The researchers matched their fossilized wing scales to a group of existing butterflies and moths that all have specialized mouth parts used today to sip nectar from flowering plants.

They dated their fossilized butterfly scales to 200 million years ago, 70 million years before flowering plants appear in the fossil record.

That suggests that the sipping mouth parts of butterflies and moths first appeared in response to periods of drought common during the era they arose, when sipping water droplets efficiently provided a selective advantage.

The first flowering plants likely produced sugary — and therefore sticky — nectar to trap windborne pollen grains. Butterflies and moths with specialized water-sipping mouth parts could shift rapidly to this new resource.

Monarch butterflies, one of the most recognized and charismatic native North American species, are just one of the many species descended from these first butterflies with specialized, liquidsipping mouth parts.

Yet, pesticides, land-use changes and human-caused climate change threaten the Eastern and Western populations of monarchs.

I find it sad to think that just as we come to understand better the evolutionary pathways that generated the diversity of life we observe around us, we also are threatening that same diversity.