Parthenogenesis

Parthenogenesis is a form of asexual reproduction in which offspring develop from an unfertilized egg. In animals it can arise through different cellular routes. Apomixis involves egg development without meiosis, producing offspring that are diploid and genetically similar to the mother. Automixis involves meiosis followed by mechanisms that restore diploidy, such as fusion of the egg with a polar nucleus or sister products, or genome duplication. In haplodiploid systems, unfertilized eggs can become haploid males while fertilized eggs produce diploid females.

In nature, parthenogenesis is common in many invertebrates, including aphids, rotifers, nematodes, and various insects such as some bees, wasps, and ants. In vertebrates, it has been documented in several reptiles (notably some whiptail lizards and related species), in certain sharks and other fish, and in a few rare cases in birds and mammals. It can occur as an obligate reproductive strategy or as a facultative response to conditions when mating is limited, as observed in some captive and wild populations.

In plants, a form of parthenogenesis occurs in apomixis, where seeds form without fertilization. While distinct from sexual reproduction, apomixis can produce progeny that are genetically identical to the mother plant.

Parthenogenesis offers advantages such as rapid population growth and colonization when mates are scarce, but it generally reduces genetic diversity and long-term adaptability. It remains an important topic in evolution, ecology, and agriculture.