Article - All-Female Lizard Species Crosses Its Own Chromosomes

Posted by Alex H.

Today's article is an interesting one, even if it might require a bit of background in genetics.

From grade school, you probably know that in sexually-reproducing species (includes most animals), a combination of male and female DNA (in the form of compressed chromosomes) crosses and creates new combinations of genetic information. This process is very complex from an evolutionary standpoint, but has survived because of the genetic resistance to random change it affords.

Now read this interesting article published via Scientific American.

When it comes to the sexual behavior of lizards, things get weird, but this article describes an interesting scenario where female checkered whiptail lizards (Aspidoscelis tesselata) are capable of carrying two sets of chromosomes and crossing them over to create a new combination of genetic information - without a male individual! This is new research to the field of reproduction without sex (i.e., parthenogenesis). This research subtly suggests that in well-adapted species, parthenogenesis could be carried out for far longer than previously hypothesized.

Why would a species even adopt parthenogenesis as a strategy of life? First off, remember that evolution is blind and without a cause. Then postulate that in environments where finding mates is especially taxing on a species, individuals that are able to create their own offspring would have a significant advantage in passing along their genes. Often, it is the case that parthenogenesis involves female individuals asexually creating clones of herself and occasionally asexually producing male individuals to add genetic diversity to that population via sexual reproduction. Here is a visual representation of this cycle:

The break from this "normal" parthenogenesis is that now female checkered whiptails have been shown capable of crossing their own chromosomes - seemingly eliminating the need for males in a population. Another interesting note is that in some species exhibiting parthenogenesis, courting behaviors are still observed, even when no males are present. I will be researching this oddity at a later date, but I am gathering that these behaviors increase fecundity (reproductive success) by increasing circulating crucial sex-related hormones released during stimulations associated with courtship (e.g., mounting).