Winter is coming: hibernation reverses the outcome of sperm competition in a fly

Abstract

Sperm commonly compete within females to fertilize ova, but research has focused on short‐term sperm storage: sperm that are maintained in a female for only a few days or weeks before use. In nature, females of many species store sperm for months or years, often during periods of environmental stress, such as cold winters. Here we examine the outcome of sperm competition in the fruit fly Drosophila pseudoobscura, simulating the conditions in which females survive winter. We mated females to two males and then stored the female for up to 120 days at 4°C. We found that the outcome of sperm competition was consistent when sperm from two males was stored for 0, 1 or 30 days, with the last male to mate fathering most of the offspring. However, when females were stored in the cold for 120 days, the last male to mate fathered less than 5% of the offspring. Moreover, when sperm were stored long term the first male fathered almost all offspring even when he carried a meiotic driving sex chromosome that drastically reduces sperm competitive success under short‐term storage conditions. This suggests that long‐term sperm storage can radically alter the outcome of sperm competition.

Local adaptation of reproductive performance during thermal stress

“…In work on the closely related polyandrous species, D. pseudoobscura, parasperm protect brother eusperm from a hostile female reproductive tract . Sperm precedence favours the last male, but after lengthy exposure to cold stress, sperm precedence reverses to favour the first male (Giraldo-Perez et al, 2016). Whether, and the extent to which intra-ejaculate interactions and ejaculate-female reproductive tract interactions change as a consequence of either juvenile or adult heat stress and whether this is impacted by mating system is unknown.…”

Directional postcopulatory sexual selection is associated with female sperm storage in Trinidadian guppies

“…; Giraldo‐Perez et al. ). This suggests that FSS may influence sperm competition outcome and that some males’ sperm may be more efficient than others to survive within FSS organs or to retain a greater fertilization efficiency after FSS.…”

“…Evidence of divergent selection on sperm characteristics in relation to the level and timing of sperm competition in relation to FSS is often only indirect. For example, although last-male precedence is usually observed in sperm-storing species (Birkhead and Pizzari 2002), paternity share in current broods can also be biased toward sperm of males that mated with the female during previous ovarian cycles (Olsson et al 2007;López-Sepulcre et al 2013;Giraldo-Perez et al 2015). This suggests that FSS may influence sperm competition outcome and that some males' sperm may be more efficient than others to survive within FSS organs or to retain a greater fertilization efficiency after FSS.…”

The impact of female mating strategies on the success of insect control technologies

“…Similarly, field conditions could hamper the effectiveness of the (genetic) manipulation mechanism. For example, low temperatures can alter sperm competition dynamics between drive-carrying and wildtype males [69], and elevated temperatures in the field can substantially reduce Wolbachia-induced CI in Ae. aegypti [48].…”