Influence of parthenogenetic reproduction on the genotypic constitution and evolutionary success of populations and species

The life cycle of Daphnia commonly includes parthenogenesis, sexual reproduction, and diapause. Although there are no genotypic transformations during diapause, it separates the 'clonal' and 'pseudopanmictic' states of the population. During parthenogenetic reproduction primarily polymorphic natural populations gradually degenerate into a mixture of a few clones. As resting eggs are usually produced sexually (= by means of sexual reproduction), after the diapause the vast diversity of individual genotypes normal for panmictic populations is observed. It is the competitive interactions between parthenogenetic clones which again eventually decrease the genotypic polymorphism. Forms in which the sexual process and diapause are rare (or species which are represented by parthenogenetic populations in one part of their area and by bisexual ones in another) demonstrate the most significant differences between clonal and panmictic populations. Parthenogenesis, apomixis and other kinds of reproduction without genetic recombination are widely spread in branchiopod crustaceans (Notostraca, Anostraca, 'Conchostraca', 'Cladocera') and in many other animals and plants. Moreover, reproduction without recombination plays an important role in evolution of faunas and floras. It is emphasized that non-recombinating races and species having high heterozygosity but a low level of genetic variation, enjoy short term advantages, but die out after change in the environment.