The effect of infection with male-killing Rickettsia on the demography of female Adalia bipunctata L. (two spot ladybird)

Abstract

Virulence of symbionts is considered to be the evolutionary product of conflicting selection pressures: maintenance of a live host from which to be transmitted, and maximization of the rate of transmission. This conflict is thought to be lessened when the symbiont is vertically transmitted, for here transmission depends on the maintenance of a healthy host. Past studies have confirmed this tenet, and have shown vertical transmission to select for decreased virulence. We here investigate the effects of the maternally inherited male-killing Rickettsia symbiont of Adalia bipunctata, the two spot ladybird, on the demography of the female host. Although no effect of infection on larval demography was observed, infection detrimentally affected the adult host, infected females showing both decreased fecundity and longevity in comparison to uninfected controls. These findings are discussed in relation to both the dynamics of the male-killing Rickettsia and the factors which affect the level of virulence of symbionts. Three hypotheses are put forward to explain why inherited symbionts are not avirulent in their female host.

Expression and Modulation of Embryonic Male-Killing in Drosophila Innubila: Opportunities for Multilevel Selection

“…Similar to D. innubila, some Spiroplasmainfected ladybird beetles (Harmonia axyridis) show egg hatch rates higher than 50%, and egg hatch can vary in this species during the lifetime of an infected female (Majerus 2003). It is also worth noting in many species infection with a malekiller can have direct negative effects on female fitness (reviewed in Majerus 2003), for example through decreased female fecundity (Ikeda 1970;Hurst et al 1994). This suggests the possibility of a bacterial density-host fecundity trade-off, which would strengthen selection on females for an optimal intermediate bacterial density.…”

Natural enemies of the Coccinellidae: Parasites, pathogens, and parasitoids

“…Most studies on bacterial infections of Coccinellidae concern male-killing bacteria (Hurst et al, 1994(Hurst et al, , 1996(Hurst et al, , 1997(Hurst et al, , 1999aMajerus et al, 1998Majerus et al, , 2000bMajerus and Majerus, 2000;Schulenburg et al, 2001;Sokolova et al, 2002;Dyson and Hurst, 2004;Nakamura et al, 2005). Male-killing agents include Rickettsia, Spiroplasma, Wolbachia, Flavobacteria, c-proteobacterium, and some yet to be identified agents (Majerus, 2006).…”

Living with the enemy: parasites and pathogens of the ladybird Harmonia axyridis

“…There is therefore an indirect fitness advantage to females from malekiller infection. Negative fitness effects, beyond the loss of males, have also been documented and include decreased oviposition rates, lower overall fecundity, higher infertility levels, or shorter adult life-span (Hurst et al 1992a(Hurst et al , 1994Majerus et al 2000;ElNagdy et al 2011), as well as reduced genetic variation in the host's mitochondrial and nuclear genomes, which could reduce their adaptive potential (e.g. Randerson et al 2000;Telschow et al 2006;Engelstadter and Hurst 2007).…”