Condition‐dependent interaction between mating success and competitive fertilization success in Drosophila melanogaster*

Abstract

Dietary restriction during development can affect adult body size and condition. In many species, larger (high‐condition) males gain higher mating success through male‐male competition and female choice, and female condition can affect the extent of both female mate choice and male investment in courtship or ejaculates. However, few studies have examined the joint effects and interplay of male and female condition during both the pre‐ and the postcopulatory phases of sexual selection. We therefore manipulated the larval diet of male and female Drosophila melanogaster to study how body size variation in both sexes biases competitive outcomes at different reproductive stages, from mating to paternity. We did not find a difference in mate preference or mating latency between females of different conditions, nor any interaction between male and female conditions. However, large males were more successful in gaining matings, but only when in direct competition, whereas mating latencies were shorter for low‐condition males in noncompetitive settings. Small males also transferred more sperm to nonvirgin females, displaced a larger proportion of resident sperm, and achieved higher paternity shares per mating than large males. In agreement with existing theory, we suggest that small males might partially compensate for their low mating success by strategically investing in larger sperm numbers and potentially other, unmeasured ejaculate traits, when they do have a mating opportunity.

Parasite‐mediated sexual selection in a damselfly

“…Body condition can affect reproductive fitness through sexual selection, as individuals in better conditions are more likely to mate (Nardo et al, 2021). The condition of an individual can be expressed in phenotypes such as secondary sexual ornaments (i.e.…”

Divergent natural selection alters male sperm competition success in Drosophila melanogaster

“…The sperm and ejaculate traits underlying competitive fertilization success are shaped by postcopulatory sexual selection (Parker, 2020). Environmental factors can also affect the outcome of sperm competition, both in the short term via plastic responses (De Nardo et al, 2021; Dobler & Reinhardt, 2016; Vasudeva et al, 2019) and over multiple generations via natural selection (Singh et al, 2016). Note that for the purpose of this paper, we will use the term “natural selection” as a shorthand for “narrow‐sense” natural selection (Endler, 1986; Shuker & Kvarnemo, 2021), that is, non‐sexual selection.…”

“…Certainly, a number of studies have examined how sperm traits respond plastically to environmental variables like diet (Engqvist, 2008), rearing density (Morrow et al, 2008), and, especially, temperature (Adriaenssens et al, 2012; Blanckenhorn & Hellriegel, 2002; Fenkes et al, 2017; Gasparini et al, 2018; Iglesias‐Carrasco et al, 2020; Kekäläinen et al, 2018; Vasudeva et al, 2019). Several others have investigated environmental effects on sperm competitiveness per se (diet: Almbro et al, 2011; De Nardo et al, 2021; Rahman et al, 2014); rearing density: (Amitin & Pitnick, 2007); temperature: (van Lieshout et al, 2013; Sales et al, 2018; Vasudeva et al, 2014); elevated CO 2 (hypercapnia) (Dobler & Reinhardt, 2016)).…”

Sperm depletion in relation to developmental nutrition and genotype in Drosophila melanogaster

“…Although numbers of sperm produced and stored are informative of male potential to invest in sperm transfer, they do not provide complete information on male postcopulatory investment strategies. For example, males of low condition may have a reduced ability to produce large quantities of sperm, but if they rarely achieve mating, they may strategically allocate relatively more sperm to a single mating compared to highcondition males (Rowe and Arnqvist 1996;Danielsson 2001;Fricke et al 2015;De Nardo et al 2021). Such conditional tactics in postcopulatory reproductive investment have been demonstrated in the ladybird, Adalia bipunctata, where food-deprived (i.e., low-condition) males transfer relatively more sperm compared to well-nourished (i.e., high-condition) males, whereas the latter transfer larger spermatophores with relatively more nonsperm components (Perry and Rowe 2010).…”

“…This prediction was based on the assumptions that males reared on low nutrients would have lower nutrient stores compared to males reared on higher nutrients, and that these males would therefore incur relatively higher costs of sperm production and have smaller total sperm reserves (Lüpold et al 2016). Moreover, males reared on a low-nutrient larval diet might invest relatively more in earlier matings if they are less attractive to females and therefore anticipate fewer mating opportunities (see De Nardo et al 2021). We also predicted that (ii) isolines would exhibit broad-sense genetic variation in male mating latency, mating duration, and sperm transfer (e.g., see Lüpold et al 2012), and that effects of isoline and diet would interact, reflecting a genotype-by-environment interaction for males' ability to invest in reproduction.…”