Asexual reproduction in Reptiles
by Randy Klabacka
If whiptail lizards could talk, the answer to the question, "mommy, where do babies come from?" would differ depending on the species asking the question. Whiptail lizards, found mostly in the deserts of North America, are a group of over 40 species– 14 of which only contain females. In these 14 species, reproduction happens through a clonal process where hatchlings are genetically identical to their mothers. This phenomenon is known as "asexual reproduction," because it occurs without the need for two parents. While asexual reproduction seems to be the exception in vertebrate animals (of which 99.9% reproduce sexually), multiple groups of lizards and snakes have developed the ability to reproduce asexually.
There are two different types of asexual reproduction. The first type occurs when a female from a species that generally reproduces sexually is able to sometimes have offspring asexually (this is known as facultative parthenogenesis). Zookeepers in the St. Louis Zoo observed this last year when a single female python (who had never been with a male python) laid eggs from which seven healthy little pythons hatched. Facultative parthenogenesis has also been observed in many other reptile species over the past century. The second type of asexual reproduction is when a species reproduces exclusively by asexual reproduction (this is known as obligate parthenogenesis). In these species, all individuals are female. In fact, obligate parthenogenesis was discovered when a researcher in Southeast Asia collected 100 female fox geckos without finding a single male. Since then, multiple instances of obligate parthenogenesis have been discovered in nine families of reptiles.
You may be asking yourself, “Why would a species reproduce asexually instead of sexually?” Or perhaps you are wondering, “Why do so few vertebrate animals reproduce asexually?” Researchers (including me) are seeking for answers to questions such as these.
Concerning the first question, some answers have been presented by theoretical biologists. The most “successful” life on earth is found in organisms that pass their genes onto the next generation. The more genes that an organism can pass on to the next generation, the more likely your genes are to persist over time. Although multiplication of your genes is a good strategy, sexual reproduction is the exact opposite– division! In other words, when a sexual parent has one offspring only ½ of their genetic material is passed onto that offspring (for example, you only have ½ of your mother’s DNA). Contrast this with asexual reproduction, where 100% of a parent’s genetic material is passed on to all of their offspring. Theoretical biologists show that because of this benefit asexual populations can quickly eclipse sexual populations.
Disclaimer: The views and opinions in this work are those of the author and do not necessarily reflect the views of Auburn University.