Australia Is Teeming With Low-Down, Dirty Liars

Slate’s animal blog.
May 30 2014 10:35 AM

Australian Plants and Animals Are Low-Down, Dirty Liars

journal.pone.0004185.g001
A predatory katydid mimics the wing flick sounds of a sexually receptive female cicada to lure male cicadas, aka lunch.

doi:10.1371/journal.pone.0004185.g001

Normally, when an insect lands on a flower, there’s a fair exchange of goods and services. The bug gets a slurp of delicious, nutritious nectar, and the plant gets the pollen that the bug was carrying or sends off some pollen of its own. If the plant happens to be an Australian tongue orchid, though, the bug gets a raw deal. The orchids lure in lonely males wasps by mimicking the scent, shape, and color of female wasps. There’s no nectar and no lady bug looking for love. The orchid gets pollinated without having to trade anything, and the insect just gets had. “These orchids are so convincing in mimicking female wasps, that the males trying to copulate with the flower actually ejaculate,” says biologist Marie Herberstein of Macquarie University in Sydney.

Nature is full of tricksters like this, and it turns out that Australia may have the trickiest of all. “I have been working on deceptive systems for many years, and it occurred to me I was seeing common patterns across very different organisms,” Herberstein says. Looking at these patterns, she and a team of biologists from down under say that deception and exploitation are not only more prevalent among Australian flora and fauna than among organisms on other continents, but are disproportionate to the amount and diversity of wildlife there.

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Take those tricky orchids, for example. In all of Europe, sexual deception of the kind used by the tongue orchids is practiced by fewer than 300 species in two genera. In Australia, the same tactics have evolved independently several times in at least 11 genera and several hundred species. While Australia is home to only 5 percent of the world’s orchid diversity, it accounts for almost half of the sexually deceptive ones.

Not to be outdone by plants, Australia’s animals put on act, too. In Europe and the Americas, crab spiders sit on flowers, wait for pollinators to come by, and then grab them for a meal. They rely on camouflage that lets them blend in with the flowers and remain undetected until the last possible second, when they ambush their prey. Australian crab spiders, on the other hand, don’t hide. Instead, they try to stand out with a deceptive lure. The spiders reflect a huge amount of UV light that contrasts against the floral background. This draws insects to the flower they’re on so they can pounce. In Australia, there are at least five species that flash UV in this way, but only one in the rest of the world, a lone species in India.

Australia is also home to almost as many parasitic cuckoo birds as Asia and Africa combined—almost a quarter of the world’s total. These birds outsource parental duties by sneaking their eggs into other birds’ nests. Deceptive cuckoos are not only more common than expected in Australia, they also seem to be better at their treachery. They’ve got an arsenal of tricks to fool their hosts, such as laying eggs that mimic the hosts’ egg color, which hatch into chicks that also match the colors of the parasitized species. Aussie cuckoo eggs are generally rejected less by the parasitized parent birds than are eggs of their counterparts elsewhere in the world.

These liars are just the beginning. Oz also has mistletoe with leaves that mimic its host plants (that’s right, the plant you smooch under at Christmas is a parasite); katydids that prey on horny cicadas by faking the wing-flicking sounds that females make when they’re ready to mate; an assassin bug that provokes ants to bite its armored leg so it can stab the distracted attackers in the head; and the lyrebird, which is known for mimicking the sounds of everything from flutes to chainsaws. The place is just crawling with charlatans.

What makes Australian wildlife so wily? The researchers propose in their paper that the continent’s environment provides a perfect setting for the evolution—and discovery—of deception. The dry, wildfire-prone conditions in much of Australia might select for behaviors that reduce the cost of acquiring or producing resources—encouraging species to get by on trickery instead of using honest labor to get food and raise broods.  Meanwhile, long stretches of geological isolation from the rest of the world, punctuated by occasional biological invasions and introductions, may have let deceptive species arriving from elsewhere thrive in Australia because they could easily exploit the “naive” natives.

Australia’s academic environment may get some credit as well. Scientists working there seem to have a knack for finding deceptive species, creating a reporting bias. Behavioral ecology is a booming field in Australia, and its research institutions encourage the pursuit of unconventional question and studies. The research culture there might simply make it more likely that Australian researchers will turn up weird, charismatic, and deceptive wildlife. The Aussies, after all, gave us scientific reports like “Finding fathers in the least faithful bird” and “Sex and Violence in Hermaphrodites.”

Matt Soniak writes about science, history, etymology, and Bruce Springsteen for a variety of outlets. He blogs about animal behavior at mattsoniak.com. Follow him on Twitter

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