evolutionary arms races
edyong | January 28, 2010
When our lives are in danger, some humans go on the run, seeking refuge in other countries far away from the threats of home. Animals too migrate to escape danger but one group - the pond-living bdelloid rotifers - have taken this game of hide-and-seek to an extreme.
If they are threatened by parasitic fungi, they completely remove any trace of water in their bodies, drying themselves out to a degree that their parasites can't stand. In this desiccated state, they ride the wind to safety, seeking fresh pastures where they can establish new populations free of any parasites.
This…
edyong | January 21, 2010
The partnerships between flowering plants and the animals that pollinate them are some of the most familiar in the natural world. The active nature of animals typically casts the plants as the passive partners in this alliance, but in reality, they're just as involved. That becomes particularly apparent when the animals renege on their partnership.
Nicotinia attenuata, a type of wild US tobacco, is usually pollinated by hawkmoths. To lure them in, it opens its flowers at night and releases alluring chemicals. But pollinating hawkmoths often lay their eggs on the plants they visit and the…
edyong | September 10, 2009The drawers of the world's museums are full of pinned, preserved and catalogued insects. These collections are more than just graveyards - they are a record of evolutionary battles waged between animals and their parasites. Today, these long-dead specimens act as "silent witnesses of evolutionary change", willing to tell their story to any biologist who knows the right question to ask.
This time round, the biologist was Emily Hornett, currently at UCL, and her question was "How have the ratios of male butterflies to female ones changed over time?" You would think that the sex ratios of…
edyong | August 21, 2009Viruses and bacteria often act as parasites, infecting a host, reproducing at its expense and causing disease and death. But not always - sometimes, their infections are positively beneficial and on rare occasions, they can actually defend their hosts from parasitism rather than playing the role themselves.
In the body of one species of aphid, a bacterium and a virus have formed a unlikely partnership to defend their host from a lethal wasp called Aphidius ervi. The wasp turns aphids into living larders for its larvae, laying eggs inside unfortunate animals that are eventually eaten from…
edyong | August 3, 2009Swine flu has made the world all too aware of the possibility of diseases making the leap from animal hosts to human ones. Now, we know that another disease made a similar transition from chimpanzees to humans, several thousand years ago. This particular infection is caused by a parasite, and a very familiar and dangerous one - Plasmodium falciparum, the agent responsible for malaria.
Transmitted by the bite of mosquitoes, P.falciparum infects over 500 million people every year. Its closest relative is a related parasite, Plasmodium reichenowi, which infects chimpanzees. Leading an…
edyong | July 24, 2009In Lake Alexandrina, New Zealand, a population of snails is under threat from a parasitic flatworm, a fluke aptly known as Microphallus. The fluke chemically castrates its snail host and uses its body as a living incubator for its larvae. But the snails have a weapon against these body-snatching foes - sex.
The New Zealand mud snail Potamopyrgus antipodarum is found throughout island's freshwater habitats. They breed either sexually or asexually through cloning, and the two strategies vary in prevalence throughout the lake. In the shallower waters round its margins, sex is the name of the…
edyong | April 28, 2009The courtship rituals of the spider Harpactea sadistica start innocently enough, with a dance and a hug. The male spider taps the female gently with his front legs and embraces her. But from that point onwards, things for the female go rapidly downhill. The male bites her and she becomes passive, allowing him to manoeuvre her into position. Like all spiders, his genitals are found next to his head, on a pair of appendages called the pedipalps. But unusually, his penis ends in a needle-sharp tip called an embolus.
The embolus sits at the end of a loop called the conductor. The male hooks one…
edyong | April 1, 2009Humans aren't the only species that have had to deal with the issue of slavery. Some species of ants also abduct the young of others, forcing them into labouring for their new masters. These slave-making ants, like Protomagnathus americanus conduct violent raids on the nests of other species, killing all the adults and larva-napping the brood.
When these youngsters mature, they take on the odour of their abductors and become the servants of the enslaving queen. They take over the jobs of maintaining the colony and caring for its larvae even though they are from another species; they even…
edyong | February 28, 2009Conspiracy theories, TV thrillers and airport novels are full of the idea that the world is secretly run by a hidden society. We have come up with many names for this shadowy cabal of puppet-masters - the Illuminati, the Freemasons, and more. But a better name would be 'parasites'.
Every animal and plant is afflicted by parasites. The vast majority are simple, degenerate creatures, small in size and limited in intelligence. They affect our health and development, and even our behaviour and culture. And by pulling the strings of key species, parasites can change the face of entire habitats.In…
edyong | February 11, 2009This is the fifth of eight posts on evolutionary research to celebrate Darwin's bicentennial.
Life can sometimes be a futile contest. Throughout the natural world, pairs of species are locked in an evolutionary arms race where both competitors must continuously evolve new adaptations just to avoid ceding ground. Any advantage is temporary as every adaptive move from a predator or parasite is quickly neutralised by a counter-move from its prey or host. Coerced onward by the indifferent force of natural selection, neither side can withdraw from the stalemate.
These patterns of evolution are…
edyong | February 10, 2009This is the fourth of eight posts on evolutionary research to celebrate Darwin's bicentennial.
Charles Darwin was a visionary in more ways than one. In 1862, Darwin was studying a Malagasy orchid called Angraecum sesquipedale, whose nectar stores lie inaccessibly at the bottom of a 30cm long spur (tube). Darwin predicted that the flower was pollinated by a moth with tongue long enough to raid the spur.
Few people believed him, but in 1903, zoologists discovered Darwin's predicted moth, Xanthopan morgani praedicta, and it did indeed have a very long tongue. Darwin accurately predicted the…
edyong | February 9, 2009This is the third of eight posts on evolutionary research to celebrate Darwin's bicentennial.
In our world, there is (roughly) one man for every woman. Despite various social differences, our gender ratio remains steadfastly equal, so much so that we tend to take it for granted. Elsewhere in the nature, things are not quite so balanced.
Take the blue moon butterfly (Hypolimnas bolina). In 2001, Emily Dyson and Greg Hurst were studying this stunningly beautiful insect on the Samoan islands of Savaii and Upolu when they noticed something strange - almost all the butterflies were females. In…
edyong | January 17, 2009
Bee hives, with their regularly arranged honeycombs and permanently busy workers may seem like the picture of order. But look closer, and hives are often abuzz with secret codes, eavesdropping spies and deadly alliances.
African honeybees are victimised by the parasitic small hive beetle. The beetles move through beehives eating combs, stealing honey and generally making a mess. But at worst, they are a minor pest, for the bees have a way of dealing with them.
They imprison the intruders in the bowels of the hive and carefully remove any eggs they find. In turn, the beetle sometimes fools…
edyong | March 10, 2008
The story of evolution is filled with antagonists, be they predators and prey, hosts and parasites, or males and females. These conflicts of interest provide the fuel for 'evolutionary arms races' - cycles of adaptation and counter-adaptation where any advantage gained by one side is rapidly neutralised by a counter-measure from the other. As the Red Queen of Lewis Carroll's Through the Looking Glass said to Alice, "It takes all the running you can do, to keep in the same place."
The Red Queen analogy paints a picture of natural foes, wielding perfectly balanced armaments and caught in a…