The Mourning Gecko (Lepidodactylus lugubris) is a small lizard species native to the Indo-Pacific region but is now widespread globally due to its adaptability and unique method of reproduction. These geckos typically measure between 3.5 and 4 inches (8.5 to 10 cm) in total length. They are known for their success as colonizers in diverse tropical and subtropical environments, often found in coastal and urban areas. They are mostly nocturnal and can change their color from light tan to dark brown to blend in with their surroundings.
Reproduction Without Fertilization
The fundamental reason for the lack of male Mourning Geckos lies in the species’ primary reproductive strategy, called parthenogenesis. This form of reproduction is a type of asexuality where offspring develop from unfertilized eggs, meaning a male’s sperm is not required. The eggs laid by the female geckos are essentially self-fertilizing, bypassing the necessity for sexual pairing entirely.
In this process, the female’s egg cell restores the full set of chromosomes needed for a viable embryo. This is often achieved through premeiotic endoreplication, where the chromosomes duplicate before meiosis, ensuring the egg retains the diploid number of chromosomes. The result is that the offspring are genetically identical to the mother, functioning as clones. A single female can lay one or two eggs every four to six weeks, allowing for rapid population growth.
Addressing the Rare Male Occurrence
The question of whether male Mourning Geckos exist is answered with a qualified yes, but their appearance is extremely rare. The vast majority of the population is female, characteristic of a species that reproduces through obligate parthenogenesis. When males do occasionally occur, they are often the result of a genetic anomaly or a cross with a closely related gecko species.
These rare male phenotypes are generally sterile, meaning they are incapable of producing viable offspring. They are not a functional part of the species’ reproductive cycle, which relies on the all-female, asexual method. Their scarcity and lack of reproductive function underscore that the species has abandoned the need for males for survival and geographic spread.
Social Structures in Female-Only Populations
The all-female nature of the Mourning Gecko population has led to unique social and reproductive behaviors. Within their colonies, females will engage in activity that appears to mimic sexual intercourse, known as pseudo-copulation. This female-on-female behavior is not reproductive in function but is believed to be a necessary stimulation to trigger or enhance egg production.
Research suggests that the physical interaction helps regulate the reproductive cycles of the colony, with dominant females often laying more eggs than subordinate individuals. Since the offspring are genetically identical clones of their mothers, the species experiences low genetic diversity. This lack of variability could make the population vulnerable to widespread disease or sudden environmental changes, as a weakness in one individual is a weakness shared by all. Despite this drawback, the ability to colonize new habitats quickly has made the Mourning Gecko a successful and widely distributed reptile.