December 6, 2013
Fossil Evidence Indicates Fig Wasps Were Here Long Before Fig Trees
April Flowers for redOrbit.com - Your Universe Online
Researchers are puzzled by a 115-million-year-old fossilized wasp from northeast Brazil.
The puzzle rests in the wasp's ovipositor, the organ through which it lays its eggs. The fossilized wasp's ovipositor looks a lot like those of present-day wasps that lay their eggs in figs. The researchers say that the problem is that figs arose around 65 million years after this wasp was alive.
The wasp belongs to the Hymenoptera superfamily known as Chalcidoidea, which includes about 22,000 known species and is estimated to contain up to 500,000 species. Chalcidoidea parasitize other insects, spiders and some plants.
"This is a tiny parasitic wasp, it's the smallest fossil wasp found in this particular deposit and it's the oldest representative of its family," said Sam Heads, a paleoentomologist at the Illinois Natural History Survey at the University of Illinois. "More importantly, it's possible that this wasp was fig-associated, which is interesting because it's Early Cretaceous, about 115 to 120 million years old. That's a good 65 million years or so prior to the first occurrence of figs in the fossil record."
Heads collaborated with University of Portsmouth scientists Nathan Barling and David Martill on the study, published in a recent issue of Cretaceous Research.
Heads notes the findings demonstrate the value of studying insect fossils.
"The fossil record of insects is very extensive both geographically and temporally. It goes back 415 to 420 million years and preserves the ancestral forms of a lot of the insects that are alive today," he said. "So it's a great resource for understanding insect evolutionary history and the distribution of insects across the planet in the past."
According to Heads, the presence of a wasp with an ovipositor that looks like those used by modern day fig wasps is not proof that figs existed in the wasp's day—a time of dinosaurs.
"There is no evidence of the existence of figs at this time and the most recent molecular study doesn't place figs that far back," he said. While it is possible that figs are older than current studies indicate, it is also possible that "something like a fig was around and this wasp was parasitizing whatever that was."
The researchers suggest this could be a case of convergent evolution, where separate species independently evolve similar traits, or that the fossil wasp could be the ancestor of the fig wasp. In the latter case, the ovipositor could first have been adapted to a plant or fruit that was around long before the fig and later found figs to be a useable substitute.
New insights into the natural history of insects, the plants they pollinate, and their hosts are gained by comparing insect fossils with living organisms. These studies are significantly different from those dedicated to the fossils of extinct animals.
"When you talk about paleontology to people the first thing they think of is dinosaurs," he said. "And that's great. Dinosaurs are really exciting, wonderful animals. But for the most part, they're extinct. With insects and other arthropods like spiders and scorpions, they're around still. So we have modern forms to compare our fossil forms to, which is incredibly useful."
Image Below: Although it lived roughly 65 million years before the earliest known occurrence of figs, the fossil wasp's ovipositor closely resembles those of today's fig wasps. Credit: Sam Heads