Parthenogenetic and Bisexual Populations of Ephemerella Notata Eat. in Poland

Abstract

ABSTRACfThe sex ratio (males: females) of final instar nymphs of Ephemerella notata varies from 0.12: 1.00 to 0.92: 1.00 in isolated populations of the Pomeranian Lake District in Poland. These data support the view that facultative parthenogenesis occurs in this species. The incidence of parthenogenesis was inversely related to population density. Parthenogenetic populations were less variable in size (determined by a principal component analysis of a total body-size index) and more synchronous in their development.

Reproductive mode of the geographic parthenogenetic mayfly Ephoron shigae, with findings from some new localities (Insecta: Ephemeroptera, Polymitarcyidae)

“…Obligatory parthenogenesis is known to exist in several mayfly species (Clemens 1922;Froehlich 1969;Gibbs 1977;Bergman and Hilsenhoff 1978;Sweeney and Vannote 1987;Gillies andKnowles 1990), andHumpesch (1980) reported that the rate of hatching among unfertilized eggs was usually greater than 80% in the obligatory parthenogenesis populations. Evidence of geographic parthenogenesis, i.e., unisexual and bisexual populations of the same species existing in the same geographic area, such as Ephoron shigae in this study, has been verified for two ephemerellid mayflies: the eastern North American Eurylophella funeralis (McDunnough) (Sweeney and Vannote 1987) and the east European (e.g., Polish, Czech) Ephemerella notata Eaton (Jazdzewska 1976;Glazaczow 1994Glazaczow , 2001. The hatching success of unfertilized eggs of Eurylophella funeralis was inversely related to the proportion of males in the bisexual populations (Sweeney and Vannote 1987).…”

“…Parthenogenesis is found in most animal groups (Suomalainen 1950(Suomalainen , 1962Glesener and Tilman 1978;Suomalainen et al 1987) and has been reported in some mayflies (Degrange 1960;Huff and McCafferty 1974;Gibbs 1977;Mingo 1978;Humpesch 1980;Sweeney and Vannote 1987;Glazaczow 2001, Ball 2001, 2002. However, in most mayflies parthenogenesis is only facultative, and is occasional or accidental (i.e., tychoparthenogenesis), such as in the North American burrowing mayfly Ephoron album (Say) (Britt 1962;cf.…”

“…Glazaczow (2001) also reported that males of Ephemerella notata decrease and disappear toward the periphery of their distribution. Geographic studies on other invertebrates in temperate regions have shown that unisexual populations generally occur at the periphery of the species range (Glesener and Tilman 1978).…”

“…In general, the percentage of hatching success for parthenogenetic eggs was usually much lower than for fertilized eggs in these cases . Glazaczow (2001) mentioned that only a small percentage of unfertilized eggs hatch and that their development is slower and not well synchronized, and Brittain (1982) argued that parthenogenesis has no importance in population dynamics. Recently, however, Landolt et al (1997) observed that half the unfertilized eggs developed in a Swiss burrowing mayfly, Palingenia longicauda (Olivier), and so parthenogenesis may be very important.…”

Potential for parthenogenesis of virgin females in a bisexual population of the geographically parthenogenetic mayfly Ephoron shigae (Insecta: Ephemeroptera, Polymitarcyidae)

“…E. SHIGAE POPULATIONS Parthenogenesis is found in many animal groups (Suomalainen, 1950(Suomalainen, , 1962Glesener & Tilman, 1978;Suomalainen et al, 1987) and has been reported in some mayflies (Degrange, 1960;Huff & McCafferty, 1974;Gibbs, 1977;Mingo, 1978;Humpesch, 1980;Sweeney & Vannote, 1987;Glazaczow, 2001;Ball, 2001Ball, , 2002. However, in the majority of cases, mayfly parthenogenesis is facultative (termed tychoparthenogenesis or occasional or 'accidental' parthenogenesis).…”