A
photo of the modern owl butterfly (Caligo Memnon) below a fossilized
Kalligrammatid lacewing (Oregramma illecebrosa) shows some remarkable
similarities. (James Di Loreto/Smithsonian)
Before
butterflies, there were Kalligrammatid lacewings — winged insects that
took butterfly-like form at least 40 million years before the modern
bugs first came on the scene. But the remarkably butterflyesque species Oregramma illecebrosa, described in a study published Wednesday in Proceedings of the Royal Society B, isn't a butterfly ancestor:
Other members of its lineage went on to become entirely different sorts
of insects. Instead, this striking similarity is a case of convergent
evolution — the same shapes, patterns and perhaps even behaviors came
about twice, totally independently.The findings come thanks to some especially well-preserved fossils found in northeastern China, which allowed researchers to study the ancient insects more closely than ever before.
"They've been known for about 100 years, but in the 1960s there were some specimens that made people say, gosh, these really look like butterflies," Smithsonian paleoecologist Conrad Labandeira, lead author on the study, told The Washington Post. "But we knew they were unrelated. That's where it stood for some 55 years."
But once Labandeira and his team — an international collaboration of scientists — got a hold of the Chinese fossils, things got much more interesting. The resemblance is so strong that even experts were fooled at a distance: Labandeira recalls a colleague from the entomology department assuming the fossil on the table was a butterfly from 20 feet away.
"When I told him to come closer, and he looked again, his jaw dropped," Labandeira said.
One of the more remarkable similarities is superficial in nature: The spots seen on the Oregramma illecebrosa fossils are nearly identical to patterns found on owl butterflies today. These so-called eye spots mimic the peepers of a large bird, scaring off predators that might otherwise make a quick snack of a delicate butterfly.
It's thought that Oregramma illecebrosa last shared a common ancestor with modern butterflies more than 320 million years ago. The fact that two quite unrelated insects developed these markings millions of years apart from one another is a perfect example of convergent evolution: Oregramma illecebrosa might not have shared space with owls, but plenty of big-eyed creatures — perhaps even dinosaurs, the prominent predators of the Jurassic period — could have served as inspiration for the markings. An Oregramma illecebrosa would have had a better chance of surviving dino dinnertime if it could pass itself off as a bigger animal, and over time — as faux-eyed insects continued to breed more successfully than those without the markings — the patterns would become more complex.
Then, millions of years later, an unrelated group of insects did the exact same thing. What worked well in the Jurassic still works well today.
But there are signs that these ancient bugs shared behavioral traits with modern butterflies, too: They had modified hairs on their legs for collecting pollen, just as modern butterflies do. And they even had long proboscises, which modern butterflies use to suck nectar from flowers — even though flowering plants didn't exist at the time. Instead, Oregramma illecebrosa and its ilk would have gathered dry and liquid pollen from primitive, non-flowering plants.
This is another case of convergent evolution, Labandeira explained. Other studies have found that multiple groups of insects had these long mouth-parts before flowers existed, so they must have evolved specifically to suck the liquids of plants that have long gone extinct. Then, when flowers became ecologically dominant, the whole system was reinvented.
"It’s kind of like a baseball team," Labandeira said. "The positions are the same, but the players are changed. It was a different world that these insects were evolving in. So they’re serving very similar roles, but they’re completely different."
No comments:
Post a Comment