Genetic tests conducted at the University of Liverpool have proved that all four born to a female called Sungai were conceived by parthenogenesis, a form of asexual reproduction that is known to take place in lizards but never documented in this species before.

Sungai, who has died since her eggs hatched, is also about to be joined as a virgin mother by a second Komodo dragon from Britain. Flora, at Chester Zoo, has laid eight viable eggs that are expected to hatch next month, even though she has never so much as met a male Komodo dragon.

Her status as a virgin mother-to-be has been confirmed by genetic fingerprinting of three eggs that collapsed. Though they are not clones, all their DNA came from Flora.

Parthenogenesis, which is derived from the Greek words for virgin birth, occurs when an egg spontaneously begins dividing as if it were an embryo, without being fertilised by sperm. It is known to have produced live young in about 70 vertebrate species, mostly reptiles and fish, and is thought to be encouraged when females are separated from males.

The stories of Flora and Sungai could have important implications for conservation of the Komodo dragon, Varanus komodoensis.

Most zoos keep only female lizards, with males moving from zoo to zoo for breeding purposes. This practice may need to be changed because it may promote parthenogenesis, which in turn reduces the genetic diversity of the species.

Richard Gibson, curator of herpetology at the Zoological Society of London, said: “I am delighted that the mysterious parentage of our Komodo dragon babies has been solved and that we have discovered something new to science at the same time.

“Knowing that the world’s largest lizard can reproduce like this suggests that many other reptiles may also do this more often than we thought and may lead to changes in the way we manage this and other species in breeding programmes.”

Kevin Buley, the curator of lower vertebrates and invertebrates at Chester Zoo, said: “Although other lizard species are known to self-fertilise, this is the first time this has ever been reported in Komodo dragons. Essentially what we have here is an immaculate conception.”

Flora laid her clutch of eleven eggs in May this year, and eight are still surviving and about to hatch. Sungai, who was on loan to London Zoo, laid her eggs in August 2005, more than two years since she had last lived with a male — Kimaan — at Thoiry zoo in France. It was possible that Sungai had stored the sperm of Kimaan for fertilisation, but this has been ruled out by genetic tests conducted by Phillip Watts, of the University of Liverpool.

The research, published in the journal Nature, suggests a way in which Komodo dragons can survive in very small populations, in the absence of males.

In humans, females have two X chromosomes and males one X and one Y chromosome. Komodo dragons and other species of the Varanus genus have W and Z chromosomes instead, and dissimilar chromosomes always produce a female.

When parthenogenesis takes place, the egg originally carries just one chromosome, either W or Z, which is duplicated. This means that all offspring are male, and able then to breed with their mothers.

“This discovery has very important implications for understanding how reptiles are potentially able to colonise new areas,” Dr Buley said. “Theoretically, a female Komodo dragon in the wild could swim to a new island and then establish an entirely new population of dragons.”

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