Virgin Birth of a Lizard

A central tenet of the Christian faith is that Jesus was born of a virgin mother and at Christmas many celebrate this event. You may think that this would have to be considered miraculous, and it is true that no such thing has ever been scientifically documented in humans. However it is well known that various animals are capable of virgin birth or parthenogeneis and I recently caught one. This is a small lizard, the Indo-Pacific gecko, Hemidactylus garnotii , which is an all-female species (a lizard Amazon !) that occurs in the tropics/sub-tropics and primarily on islands. You can see that being parthenogenetic would be a tremendous advantage for an island-hopping species since theoretically only one individual could colonize a new island. The disadvantages to this method of reproduction are equally obvious in that there is little genetic variation and thus limited potential for adapting to changing conditions of the environment and competition.

Both of these circumstances have been illustrated in my house. When we first purchased in 1994, the Indo-Pacific gecko was the common species and could be often seen inside and outside the house. It lays a remarkable small hard-shelled egg which is placed in various locations up off the ground. It is different from most reptiles and similar to a bird egg in that it does not require moist surroundings to develop. This is a huge advantage not only in rafting from island to island, but in surviving on dry islands with limited fresh water. However sometime during the past ten years the tropical house gecko, Hemidactylus mabouia , appeared on the scene. It is a sexually reproducing species and seems to be a superior competitor to the Indo-Pacific gecko and has eliminated it from our area on southern Manasota Key. Yet just recently I found an Indo-Pacific gecko on Palm/Knight island which is more isolated since there has been no road connection to the mainland for 45 years.

Two other interesting features of the gecko are the unusual eye pupil and the feet. In daylight the pupil is constricted to a series of five openings, instead of the single one we have. The gecko is nocturnal and probably has difficulty in seeing in daytime. It is postulated that the multiple pupil openings focus five images on the retina instead of just one and thus improve visual acuity. The design of the feet illustrates a remarkable adaptation for climbing vertical surfaces including even glass. If the structure of the toes is magnified, it can be seen that there are huge numbers of fine hair-like filaments but it was long a mystery how these could stick to surfaces. Now it is considered that the ends of the tiny filaments bind to surfaces by atomic van der Waals forces, a weak energy but sufficient when added together in very large numbers. This evolutionary technique is being copied by engineers who hope to use it in velcro-like designs to climb surfaces.

I value all types of geckos as natural controls on insects that infest the house. If you resist spraying pesticides, you may allow for natural predators such as geckos and huntsman wall spiders to eat the roaches. You may also place sand around the perimeter of your house which will be colonized by ant lions (the larvae of lace wings) which will eat ants which attempt to cross your threshold. Of course you have to adjust yourself to the presence of these predators, but this is easy in the case of geckos which are actually considered lucky when found inside houses in the Philippines. Adjusting to the wall spiders requires a bit more mental control but just think of how potentially toxic the pesticides are.

When we look closely at the adaptations of the animals that live within our houses in Florida, you may indeed express amazement and wonder. Our domestic domains are a microcosm of the world at large and reveal much about evolutionary processes. So you need not watch TV to be amused when you are at home; just observe your house critters at work and play.

Bill Dunson, Englewood, FL & Galax, VA
wdunson@comcast.net