The first bedbug infestations may have occurred in the beds of Cretaceous critters.
Scientists previously assumed the bloodsuckers’ first hosts were bats. But a new genetic analysis of 34 bedbug species reveals that bedbugs appeared 30 million to 50 million years before the nocturnal mammals, says Michael Siva-Jothy, an evolutionary biologist at the University of Sheffield in England, and his colleagues.
The analysis, published online May 16 in Current Biology, pegs the emergence of ancient bedbugs at more than 100 million years ago. It also fleshes out more of the pests’ history. For instance, two bedbug species that humans are most familiar with didn’t evolve just to plague us. The common bedbug (Cimex lectularius) and the tropical bedbug (C. hemipterus) emerged around 47 million years ago, long before early human ancestors meandered into bedbug-infested caves, the team found (SN Online: 4/10/17).
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The new study “puts the Cimicidae family on the map in terms of understanding its diversity, understanding its evolutionary history in a way that no other previous studies had,” says Zach Adelman, a molecular geneticist at Texas A&M University in College Station, who was not involved in the study.
To build a collection of bedbug specimens, a global network of scientists plucked insects from damp caves and dusty museum exhibits over 15 years. For each species, researchers looked at four genes known to mutate at a constant rate, like an evolutionary timekeeper. The team then calibrated that data with the known fossil records from two insects — an ancient species of bedbug and a closely related insect species — to create its timeline.
The genetic analysis can’t say what Cretaceous critters ancient bedbugs snacked on. But a computer simulation and modern-day behavior — bedbugs prefer hosts that sleep for long periods in one place — suggest that the insects probably fed on small mammals and birds.
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Using the feeding habits of modern bedbugs, the team also mapped the likeliest hosts their ancestors would have preyed on. It found that bedbugs were initially picky eaters that preyed on only one type of mammal or bird. Some bedbug lineages continue to dine on a single host. But over time, some swapped furry for feathered prey, and a few even broadened their palate to include a variety of hosts, including humans.