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New Phylogeny Sheds Light on Assassin Bug Evolution

Oct 26, 2012 08:51 AM EDT
Assassin bugs
A selection of different assassin bugs representing different evolutionary lineages.
(Photo : W. S. Hwang, Weirauch Lab, UC Riverside.)

Researchers have reconstructed a new phylogeny of assassin bugs, shedding light on their evolutionary history.

Assassin bugs get their name for their habit to lie in ambush for insect prey. With speed and precision, they attack their prey and inject them with an enzyme to liquefy and guzzle their innards. The bugs don't stop with this. They attach the external skeleton of the insect's body to its back and use it as a form of protective armor, according to The Ark in Space.

There are several species of assassin bugs, with 140 species of them being blood suckers. They are also known as kissing bugs that are capable of spreading chagas disease to humans.

Although there are different species of these bugs, it had been a difficult process for experts to understand their evolutionary history. Fossils of some bug species have shed very little light on their evolution.

But now, a team of researchers have reconstructed a new phylogeny that sheds light on the evolutionary history of the assassin bugs. They used molecular, paleontological, behavioral and ecological data to analyze the species and understand their evolution.

They found that several assassin bug species belong to the subfamily Reduviinae, the second largest subfamily of assassin bugs. Earlier phylogenies have listed only some species of bugs as belonging to Reduviinae.

They estimated that the assassin bugs originated during the Middle Jurassic (~178 million years ago) and then diversified in the Late Cretaceous (~97 million years ago) period.

Nearly 90 percent of the existing species diversity is believed to have started during the late Cretaceous period. It is still unclear as to what caused the species to diversify.

Experts also determined the origin of the blood-sucking kissing bugs. They estimated that the kissing bugs originated 27-32 million years ago, while earlier studies calculated their origin to be around 107 million years ago. 

They are more commonly found in Central and South America in diverse environments. These bugs evolved to feed on the blood of lizards, birds and humans.

"The previous estimate of 107 million years ago linked the diversification of kissing bugs with the splitting of South America from Antarctica and provided a longer time-span for kissing bugs to speciate and spread across the continent and adapt," student Wei Song Hwang, who reconstructed the assassin bug phylogeny along with his professor, said in a statement.

"Our research shows that this is not the case.  By including more data and improving estimation methods, our younger estimate of 27-32 million years ago matches the time when the hosts, mainly mammals and birds, were diversifying at a rapid rate in South America, he said.

Using their molecular dataset, experts also found that the blood-feeding kissing bugs either have a single origin or two separate (but close) origins. A single origin could mean that all kissing bugs could share common traits.  

"The possibility that there are two separate lineages implies that there will be shared traits among the lineages, but also slight differences we need to be aware of when developing different preventative strategies," Hwang explained.

Experts suggest that reconstruction of phylogenies can help in understanding the evolution of life and how some specific traits evolved.

The findings of the study, "Evolutionary History of Assassin Bugs (Insecta: Hemiptera: Reduviidae): Insights from Divergence Dating and Ancestral State Reconstruction," are published in the journal PLOS ONE. 

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