Female fertility in Hippodamia convergens (Coleoptera: Coccinellidae) is maximized by polyandry, but reduced by continued male presence

Mohamed H Bayoumy,J.P Michaud

doi:10.14411/eje.2014.067

Abstract

Many species of lady beetles are highly promiscuous and females mate repeatedly even when not sperm-limited. We quanti- fi ed female reproductive success and progeny development in Hippodamia convergens using a laboratory experiment designed to test whether (1) male novelty (different males), (2) male mating status (virgin, non-virgin) or (3) opportunities for female mate choice, would increase female fi tness compared to a similar number of matings with the same male. Daily access to novel males, regardless of their mating status, increased the egg fertility of females, but not their fecundity. Opportunities for mate choice did not improve any measure of female reproductive success compared to arbitrary assignment of males, but slightly increased reproductive rate, as measured by the number of days to produce 15 clutches. The eggs of monogamous females had the fastest eclosion times, but larval development was fastest for progeny of females polyandrous with non-virgin males, and total developmental time did not differ among treatments. In a second experiment, con fi nement with two males during oviposition disrupted egg clustering and reduced egg fertil- ity, but not female fecundity, relative to con fi nement with one male or oviposition in solitude, suggesting a negative impact of male harassment on female fi tness in the presence of multiple males. However, the continued presence of two males also improved progeny survival and reduced progeny development time relative to female con fi nement with one, likely due to summation of paternal effects when females were allowed unlimited matings with both males. These results do not rule out genetic bene fi ts of polyandry, but sup- port the view that enhanced egg fertility is a primary bene fi t, and suggest more subtle bene fi ts may be obtained in the form of additive paternal effects. The average number of female matings in nature may even exceed that required to obtain such bene fi ts if females use convenience polyandry to diminish male harassment.

Highlights

Throughout much of the 20th century, sexual selection theory rested on the premise that male reproductive success was limited by access to females, whereas female reproductive success was limited by access to resources that can be converted into offspring, rather than by access to sperm (Trivers, 1972; Jennions & Kokko, 2010)
Polyandry improved egg fertility compared with monogamy (T1 vs T2: F = 4.86; df = 1, 21; P = 0.039), egg fertility was unaffected by male mating status (T2 vs T3: F = 0.11; df = 1,20; P = 0.739) or female ability to choose mates (T3 vs T4: F = 1.53; df = 1,20; P = 0.231)
Matings with a series of different males increased the egg fertility of H. convergens females in comparison to a similar number of matings with the same male, supporting our first hypothesis that matings with novel males would improve female reproductive success compared to a similar number of matings with the same male

Summary

Introduction

Throughout much of the 20th century, sexual selection theory rested on the premise that male reproductive success was limited by access to females, whereas female reproductive success was limited by access to resources that can be converted into offspring, rather than by access to sperm (Trivers, 1972; Jennions & Kokko, 2010). There is growing evidence that females may receive various material benefits from males apart from sperm, and that mating with multiple males can improve female reproductive success in various ways unrelated to sperm limitation (Ridley, 1988; Hunter et al, 1993; Jennions & Petrie, 2000; Tregenza & Wedell, 2000; Hosken & Stockley, 2003; Simmons, 2005). 2002; Hosken & Stockley, 2003; Hosken et al, 2003), and there is abundant evidence from many taxa that multiple maternal matings can improve offspring fitness in various ways, both genetic and epigenetic (Madsen et al, 1992; Olsson et al, 1996; Tregenza & Wedell, 1998; Fisher et al, 2006; Parker & Birkhead, 2013). In coccinellid beetles, paternal effects on offspring fitness may be functionally linked to fecundity stimulation and can vary with male mating status (e.g., Michaud et al, 2013; Mirhosseini et al, 2014)

Methods

Results

Conclusion