Portside

In case you were wondering, at last count 1,659,420 species of animals have been described by scientists. Nearly 80% of those are arthropods, or insects and their crunchy relatives.

Our Planet of the Arthropods is dominated by insects, and when and how insects took over the earth is a question that’s puzzled naturalists for centuries. In an incredible international effort, 100 scientists combined their molecular, computational biology, statistics, paleontology, and taxonomic expertise to uncover some surprising conclusions about when major groups of insects evolved:

B. Misof, et al. 2014. Phylogenomics resolves the timing and pattern of insect evolution. Science 346 (6210): 763-767.

How do you solve a problem like the insects?

The back story of this research is almost as interesting as the results. Making sense of the diversity of insects in collections has traditionally been a task for a lone expert, usually specializing in just one subset of a group. They become so identified with their study organisms, they may be introduced as “The Ant Man” or “The Wasp Woman.” (No taxonomists I know wear spandex tights and capes to work, for which I am profoundly grateful.) With over a million described species, it’s not hard to see how someone might spend an entire life trying to make order out of biodiversity chaos.

Taxonomy has a history of conflict and eccentricity, and the entry of new molecular technologies into the world of tiny pins and museum specimens hasn’t always been smooth.  When sequencing was expensive and time consuming, the question was “which species should we do next?”  Competition for funding and lab space was brisk.

With advances in both computing and Next-Generation sequencing, the speed and cost of  sequencing dropped enough that scientists can band together and ask bigger questions. Brian Wiegmann of North Carolina State University (Author #74) put this elegantly: “It’s not enough to just catalog the books in the library; we want to understand their contents.”

Bernhard Misof from the Zoological Research Museum Alexander Koenig, Germany (Author #1), Xin Zhou from the China National GeneBank, BGI-Shenzhen, China (Author #100), and Karl Kjer from Rutgers University, USA (Author #99), came up with an ambitious plan. They formed 1KITE; the acronym stands for 1K Insect Transcriptome Evolution. A global crew of experts was recruited to help create an open-access inventory of transcriptomes (all expressed genes in an organism) for 1,000 insect species.  This database will be used to answer questions about how insects evolved into the amazing diversity of forms we see today, and also has applications in medicine, agriculture, and conservation ecology.

The paper released this week deals mostly with the timing of insect evolution, based on a subset of 144 species. The researchers are looking for answers to some very big questions: When did insects evolve flight? When did the amazing diversity of insects develop?

Clocks and Rocks

The problem with fossils is they are rare. When you have tiny squishy animals involved, they are even less common.  This new research uses time estimates based on geological evidence from fossils in combination with estimated times of divergence based on molecular evidence. This is sometimes called a molecular clock, since it uses accumulated changes in DNA to tell how much time has passed.

Looking at all the RNA in thousands of insect samples in hundreds of species of insects is a LOT of data.  The biggest problem for the project was dealing with the massive amount of sequence information generated.  The possible combinations were in the quadrillions. The computing capacity to crunch all that data…doesn’t exist.

This is where computer scientist and bioinformatics expert Alexandros Stamatatakis (Author #60) and his team came into play. His research group came up with a mathematical method to exclude highly unlikely combinations, and focus on likely ones. The Heidelberg Institute for Theoretical Studies Supercomputer group, which usually works on astrophysics problems, was used to crunch the data.

Dinosaurs did not have lice, and other revelations

So what did this tremendous amount of work find? The conclusion I think will stir up the most public attention is that lice are a recent group of insects, appearing only about 53 million years ago; the time that modern birds and mammals showed up.

This date makes lice “younger” than primates. There may be a bit of a kerfuffle as previous lousy estimates based on fossils are revised. Everyone loves a good taxonomic throwdown.

But that is really a secondary finding. Other major findings of note:

• Insect ancestors (Hexapoda) likely originated during the Early Ordovician Period, about 479 million years ago.
• Insect flight emerged around 406 million years ago, around the same time plants began to really diversify on land and grow upward into forests.
• The explosive diversification of insects into most of the major orders we see today happened before the emergence of Angiosperms (flowering plants).

Just how very fast insects diversified is remarkable. The earth is ~4.5 billion years old. In just the last 10% of earth’s history, plants colonized the land. In a span of 80 million years insects formed most of the major groups still alive today and took over the skies, where they reigned supreme for millennia.

Jessica Ware of Rutgers University (Author #8) said “it was a rapid and extreme radiation in a very short period of time. It made our job really hard as scientists–that’s been one of the traditional stumbling blocks for classifying insects.  With this huge amount of data we now have excellent resolution, and we can actually say something about age ranges.”

What Does It All Mean?

The best part of this research is yet to come, but where we are headed is clear. The Insect tree of life has been pruned and re-arranged constantly in the last century. It sometimes feels like taxonomists have been participating in an FBI witness-protection program, the names have been changed so often.

That will certainly continue — understanding how each group of beetles, for example, is related is a very fine level of detail. But the bigger picture is finally coming into focus. We now are on track to a real phylogeny, or map of what came first, and what relationship groups have with each other. This group is a parent, this group is a sister.

As more of the research from this group is published, we are getting closer to a phylogeny of insects that is more than just a story that we pieced together from wing patterns and bug genitals. We are truly beginning to realize what a great beetle collector once said:

“From so simple a beginning, endless forms most beautiful and most wonderful have been, and are being, evolved.” Charles Darwin.

Golden Wasp  Dr. Oliver Niehuis, ZFMK, Bonn