#[wasn't able to find many studies on the subject. so i took some liberties.]

[pkmnherpetology]

today i want to talk a little bit about herp pokémon, sex chromosomes, and sex determination.

most of you have probably already been taught about the xy chromosome system; in this system, there are many possible combinations of sex chromosome, and these combinations develop into many different phenotypes. in pokémon, we generally associate an xy set of chromosomes with a "male" phenotype, and an xx set with a "female" phenotype. obviously this is a great simplification, and not really as applicable to humans, but that's the gist of it, right? most pokémon use this system, including many herp pokémon. in these pokémon, if parthenogenesis occurs, all offspring will be female- for example, a salazzle that reproduces parthenogenetically will produce all female offspring.

now, some of you who are a little more bio-savvy might know about the other system pokémon have, which is the zw system. in this system, zz sets often develop a "male" phenotype, while "female" phenotypes generally stem from a zw set. this system is found in bird pokémon, some bug pokémon, and most notably for our purposes, some reptile pokémon (for example, kecleon and the treecko line). in these lines, if parthenogenesis occurs, the offspring will almost certainly be male.

however, some pokémon don't have sex chromosomes at all. crocodilian lines and the tirtouga line rely purely on something called "temperature-dependent sex determination". in this system, genetics don't determine sex whatsoever. rather, the temperature at which eggs are incubated determines the phenotype the hatchlings emerge with.

here's where things get interesting. there may be pokémon that have both sex chromosomes and temperature-dependent sex determination. in the helioptile line, some evidence suggests that heliolisk produce embryos that have sex chromosomes, but develop phenotypically based on temperature. what this means is that there may be heliolisk out there that are genetically zw but present with a "male" phenotype, or vice versa. even more interestingly, these individuals would still be able to breed with zw females, and produce viable offspring. now this is still up in the air- in fact, i know someone studying this exact topic right now, but should it prove to be true, it would definitely change our understanding of sex determination in reptile pokémon as well as our understanding of sex determination in an evolutionary context.