There are at least four sexual species within what is currently in the books as "Heteronotia binoei", as well as the parthenogenetic form(s).
It's a fairly complicated process, but the short, simple version is something like this:
Long ago there was one species of 'Bynoe's Gecko', which was widespread across Australia. The climate changed and became fairly nasty for these lizards, and a lot of their distribution became uninhabitable. The species became restricted to a few isolated populations, and they remained isolated for quite some time. During this time, they evolved and became somewhat different from one another, sufficiently different to be considered different species, but not different enough to be entirely reproductively incompatible...
Some time later (but still over 100,000 years ago), the climate changed once again and things were a bit nicer for the lizards. Most of Australia was once again quite comfortable for them to live in, and they spread out and recolonised. As they spread out, the previously isolated forms encountered one another, and since they had evolved in isolation, they hadn't developed reproductive isolation mechanisms. The males and females of two of the species of sexuals still recognised each other as potential mates, and attempted to reproduce, which in many cases they did...
The resulting babies appeared to be normal, but when they themselves tried to reproduce things weren't quite right. Because their maternal and paternal chromosomes weren't similar enough, they couldn't undergo meiosis, they chromosomes couldn't assort and separate properly. The males would have had useless diploid sperm (their sperm is supposed to be haploid), so they were functionally sterile (perhaps they could have fertilised enucleated eggs, but those are pretty much absent in the natural world). The females, however, didn't have quite as much of an issue with being forced to dump their entire compliment of DNA into their eggs. The eggs contained a diploid nucleus as soon as they were produced, and due to a convenient lack of a normal biological function which prevents the commencement of development until the egg is fertilised by a sperm, these eggs simply commenced development immediately, and since their DNA was identical to that of their mothers, their daughters (there were no females, as when you clone an individual of a species which determines its sex genetically, the clones will be the same gender) were clones. These clones were able to do the same thing their mothers did... pretty cool, but the story doesn't end there...
These diploid parthenogens were still recognised by the males of each other the (sexual) parental species as potential mates, and the females still recognised the males in the same way (they hadn't evolved not to). Copulation occurred, and haploid sperm superfertilised the diploid eggs, resulting in triploid offspring! These triploids had even more trouble with meisosis (not only were there incompatible chromosomes, but there were sets of three, which are very difficult to put into pairs!). Consequently, the same thing happened as before, all of the mothers' DNA was dumped into their eggs, and triploid clone daughters were the result, which were perfectly capable of producing clones of themselves, which were capable of... yeah, you get the idea.
The eggs were already overloaded with DNA (three sets of chromosomes instead of two), and further superfertilisation seems impossible (at least almost always). So, it seems the evolution pretty much ended back there, over 100,000 years ago. The cloning process has continued to this day, however, and clones of those ancient animals are alive today!
This is very different from facultative parthenogenesis (which apparently is what the Komodo Monitors do). Unlike obligate parthenogens (such as the "Bynoe's"), facultative parthenogens can reproduce either way, and different facultative parthenogens do it in different ways. Facultative parthenogenesis is (at least to me!) a lot less interesting, and unlike obligate parthenogens, the genotypes of the facultatives changes over the generations, so you don't have clones of ancient animals.
Parthenogenesis is quite rare in animals, and the 'higher' the animal, the rarer is becomes. It is effectively absent in mammals (there are some 'sort of' and 'partial' exceptions, including human chimeras), extremely rare in birds (it does occur very, very rarely in Turkeys, in which strangely the offspring are always male), there are some cases of it in reptiles, for example the "Bynoe's Geckoes" and Menetia skinks (the situation with them is extremely messy and not a case of long lines of cloned animals). It occurs in frogs and fish (we have a small number of examples of each in Australia), it is far more common in invertebrates, in some cases, such as stick insects, facultative parthenogenesis is almost the norm. In plants it does exist, although it's usually called apomixis. My honours year revolved around a parthenogenetic grasshopper, which ate parthenogenetic plants (Mulga trees) and themselves were sometimes eaten by parthenogenetic lizards (Menetia skinks). Such a parthenogenetic food chain is extremely unusual!
Sorry for oversimplifying.
I've been wanting to write an article for Reptiles Australia on this topic for years! They'll come around eventually!
