Parents Without Partners:Drosophilaas a Model for Understanding the Mechanisms and Evolution of Parthenogenesis

Abstract

Of 40 Drosophila species screened to date, a majority have shown some ability to at least initiate parthenogenetic development. In one case, Drosophila mangebeirai, natural populations are entirely female, making it the only obligate parthenogenetic species of Drosophila. Only a few of the species that exhibit the ability to undergo early embryonic development of unfertilized eggs successfully respond to selection for parthenogenetic production of adult flies. Laboratory strains of parthenogenetic Drosophila mercatorum have been created by artificial selection on multiple occasions, but the proportion of eggs undergoing development to adulthood has never exceeded 8%. Selection produces gains in the number of unfertilized eggs undergoing early development, but the majority arrest at the embryonic or first larval instar stages. Four components to successful parthenogenesis include (1) a female’s propensity to lay unfertilized eggs, (2) the ability of the eggs to restore diploidy, (3) the ability of the parthenogenetically produced diploid embryo to complete larval development and pupation, and (4) the existence of genetic variability within and among Drosophila species in the frequency of parthenogenesis suggests the existence of multiple steps in its evolution and offers a way to explore the genetics of this unusual reproductive strategy.

The genetics of egg retention and fertilization success inDrosophila: One step closer to understanding the transition from facultative to obligate viviparity

“…As opposed to Drosophila species that are capable of parthenogenetic development (e.g., D. mangebeirai , Carson et al. ; Markow ), the failure to fertilize an egg for D. melanogaster counts as pointless loss of reproductive potential. Although it is known that virgin females naturally lay a negligible amount of unfertilized eggs, this clearly cannot account for the observed low fertilization success.…”

Genetic causes of transitions from sexual reproduction to asexuality in plants and animals

“…Spontaneous production of unreduced gametes is a well‐documented phenomenon in plants and animals that otherwise do not reproduce asexually (e.g. Schwander et al ., ; Brownfield & Köhler, ; Markow, ). Whereas unreduced gamete (egg) formation is certainly a first step towards and prerequisite of asexual reproduction, spontaneous development of this egg cell in the absence of fertilization represents a second factor required for the production of new asexuals.…”

Parthenogenesis and developmental constraints

“…However, it is uncertain whether the drastic changes of meiosis associated with obligate parthenogenesis can be achieved by gradual evolution. For instance, in wild strains of D. parthenogenetica 1.5% of eggs laid by unfertilized females develop into viable adults (Stalker, 1954) and only three viable adults were produced from 50,000 unfertilized eggs of D. mercatorum (Kramer, Templeton, & Miller, 2002), compared to 50% in the obligate parthenogenetic D. mangabeirai (60% of eggs hatches of which 80% survive as adults; Carson, Wheeler, & Heed, 1957;Markow, 2013;Murdy & Carson, 1959;Sprackling, 1960;White, 1973). For instance, in wild strains of D. parthenogenetica 1.5% of eggs laid by unfertilized females develop into viable adults (Stalker, 1954) and only three viable adults were produced from 50,000 unfertilized eggs of D. mercatorum (Kramer, Templeton, & Miller, 2002), compared to 50% in the obligate parthenogenetic D. mangabeirai (60% of eggs hatches of which 80% survive as adults; Carson, Wheeler, & Heed, 1957;Markow, 2013;Murdy & Carson, 1959;Sprackling, 1960;White, 1973).…”

“…Reproductive success in sporadic parthenogenesis is generally extremely low, with hardly any offspring surviving as fertile adults (e.g., Corley & Moore, 1999;Little et al, 2017;Murdy & Carson, 1959;Olsen, 1974;Sprackling, 1960;White, 1973). For instance, in wild strains of D. parthenogenetica 1.5% of eggs laid by unfertilized females develop into viable adults (Stalker, 1954) and only three viable adults were produced from 50,000 unfertilized eggs of D. mercatorum (Kramer, Templeton, & Miller, 2002), compared to 50% in the obligate parthenogenetic D. mangabeirai (60% of eggs hatches of which 80% survive as adults; Carson, Wheeler, & Heed, 1957;Markow, 2013;Murdy & Carson, 1959;Sprackling, 1960;White, 1973). In Drosophila, the low success of sporadic parthenogenesis appears to be mainly due to both a low efficacy in centrosome assembly and poor ploidy restoration (Eisman & Kaufman, 2007;Riparbelli & Callaini, 2003).…”