What sort of sex-determination system would be required for males of a species to only result from parthenogenesis, whereas females only result from fertilization? I am not aware of a system exactly like this on Earth.

  • 2
    $\begingroup$ You know, changing question to invalidate already posted answer is terribly bad manners. $\endgroup$
    – Mołot
    Dec 20, 2016 at 14:01
  • 1
    $\begingroup$ @Mołot: Thanks for the save. I am aware of the haplodiploidy system, hence "fully diploid". $\endgroup$
    – Anonymous
    Dec 20, 2016 at 14:17

3 Answers 3



After wikipedia: Arrhenotoky (from Greek -τόκος -tókos "birth of -" + ἄρρην árrhēn "male person"), also known as arrhenotokous parthenogenesis, is a form of parthenogenesis in which unfertilized eggs develop into males.

Bees are a famous exaple of species reproducing this way. I suggest you visit those pages: Haplodiploidy and Bee, sociality subsection for more comprehensive explanation.

  • Females are XY, producing Y gametes.
  • X gametes generated by a female degenerate
  • Males are XX, producing X gametes.

Under this system males can only be generated as you are asking.


a/α determination system

This sex-determination system is wholly made up. Under this system, there are two types of allosomes: a and α. One sex is heterozygous (a/α), the other sex is homozygous (a/a or α/α).

Unlike other sex-determination systems, but like mating types in algae and fungi, gametes carrying the same allosome cannot fuse due to special incompatibility proteins on the cell surface. Parthenogenesis bypasses incompatibility through chromosome replication within an oocyte, a form of automixis. This will produce a homozygous zygote.

The heterozygous sex could only be produced through sexual reproduction while the homozygous sex could only be produced through parthenogenesis.

  • If the homozygous sex is male and the heterozygous sex is female, then this provides the circumstances desired by the original question. Sons will have only mothers, while daughters will have mothers and fathers, but grandsons may have maternal grandfathers.

  • If the homozygous sex is female and the heterozygous sex is male,
    then this results in an evolutionary dead end because the female
    population will effectively be clones of one another. Daughters will only ever have mothers, never fathers nor grandfathers.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .