Michael's Rediscovery of Nature

Ramblings and observations of a former biologist and a lifelong naturalist, who has recently returned to his roots in east Texas. After a many years of working from coast to coast in an industry far removed from biology, it has been a pleasant change of geography, activity, and attitude. No stressful job decked out in a three piece suit. No city living. Instead there is a rediscovery of the woods, of something scurrying through the leaves, of the clear notes of a bird call, and of reliving the joy that I had when nature was a playground and a classroom.

What Do You Mean They Reproduce Without Males?

While Googling for some information tonight, I got sidetracked and searched for an old "friend".  Well, it is a lizard, but I am sure you know what I mean.  Anyway, I discovered a link to an old paper that I co-authored years ago.

It was fun to see the old paper again and to remember how we traveled to Laredo in the heat of summer to collect some specimen of Laredo Striped Whiptail lizards, Cnemidophorus laredoensis, for the study.  

MFM Paper

Trying to catch these lizards is not easy under any circumstances.  They are extremely fast and evasive and the hotter it is they more fired up they are.  On the day we spent in Laredo collecting them, it was extremely hot and very humid.  

These lizards are usually found in creek beds and are relatively easy to spot.  They are the greenish streak that you usually see as you walk along the dry creek.  

In order to catch them, we had made a drift fence which is a ten foot strip of hardware cloth with a canvas bottom that has a chain sewn into it to hold the fence close to the ground.  When a lizard is spotted, we would spread the fence along an open area and curl each end into a semi-circle.  Then we would walk in a wide circle to get on the other side of the lizard so we could chase it into the drift fence.  When it would hit the fence, it would run to one side or the other until it encountered the partially circled end.  We would rush up, roll the semi-circle end into a full circle, then grab the lizard as it tried to crawl out.  You had to be fast.

We probably had a 50% success rate which is pretty high and is a testament to our experience for we had practiced the technique many times while catching other lizards in other locations.

Some of the specimen were taken to the lab where the karotypic analysis was done.

This is an interesting lizard. It is an all female species which is known as a parthenoform.  That means that they reproduce without fertilization from a male.  This process, parthenogenesis, occurs naturally with many plants, some invertebrate animal species and a few vertebrates.  

With lizards, it seems to be a result of hybridization between two closely related species.  In this case, the study showed that the likely parental species were Cnemidophorus gularis, Spotted Whiptail, and Cnemidophorus sexlineatus, Six-lined Whiptail.   Both of these lizards are found in the same area as the Laredo Whiptail, but inhabit somewhat different habitats.  The Laredo Whiptail is usually only found in habitats that are "disturbed" such as in creek beds.  

Without getting into a long discussion on a definition of species and the evolutionary processes, let me put this in a very basic way.  

Species are normally genetically isolated from one another on a cellular level.  Simply put, even if two different species mate, the genetic material is usually different enough not to allow successful propagation.  With some closely related species, the genetic differences may be slight.  In these cases, successful propagation may occur, but it rarely occurs because the organisms are usually isolated from one another by other factors such as different habitats or different behavior.  In unstable or disturbed habitats, such as creek beds or other areas of habitat turmoil, two species that are normally isolated may encounter one another and mate.  With many organisms, this often results in a hybrid that is usually infertile.  In the case of Cnemidophorus, this may create a hybrid that is a parthenoform.  

I realize this has nothing to do with east Texas nature in a direct manner, but it is an interesting bilogical concept.  I thought it might be worthy of including here.    


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