October 26, 2012
Filling In Evolution Of Assassin Bugs
Brett Smith for redOrbit.com - Your Universe Online
Despite their proximity and notoriety among humans, the bugs´ known evolutionary history is rather erratic–with few historical fossils and incomplete data.
Using molecular, paleontological, behavioral and ecological analyses, two entomologists at the University of California at Riverside (UCR) have filled in some of the holes in the evolutionary story of assassin bugs. Their work has allowed them to rewrite the phylogeny, or relationships among, assassin bug species, according to the researchers´ report in the open access journal PLoS ONE.
"We can now zoom in on specific groups within the phylogeny to examine specific aspects of the evolution of that group," said co-author Christiane Weirauch, an associate professor of entomology at UCR, in a press release. “Our phylogeny significantly improves our knowledge about relationships within assassin bugs and will guide future research work in understanding how some of the interesting prey specialization behaviors and prey capture techniques have evolved."
"One significant improvement is the addition of several assassin bug species from the subfamily Reduviinae*, the second largest subfamily of assassin bugs," said the study´s other author Wei Song Hwang, a graduate student at UCR. "Previous phylogenies have a very limited representation of Reduviinae, which means the overall interpretation of the phylogeny is of limited value."
According to the report, assassin bugs originated about 180 million years ago, during the Middle Jurassic Period. They diversified significantly 100 million years ago due to an unknown cause. This massive Late Cretaceous expansion of species occurred to the point where 90 percent of modern species diversified from this time onwards.
Determining the origins of the kissing bug subset provided the researchers with the biggest surprise. They calculated that the blood-sucking bugs originated 27 to 32 million years ago, a much different result than previous estimates that had placed the origin at 107 million years ago.
"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," Hwang said. "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."
This latest study of assassin bugs is part of a greater effort in the scientific community to reconstruct the entire “Tree of Life”– a potential way to show how all organisms are related and can be traced back throughout the evolutionary history of Earth.
"Reconstructing a phylogeny, a framework from which we can infer the evolutionary history of any group of organisms, is thus the first step towards understanding how life evolved, how different species relate to one another, how specific traits evolved over time, and why biodiversity occurs the way it does today," Weirauch concluded.
*Reduviinae subfamily links to Reduviidae family.