Male Success in Intrasexual Contests Extends to the Level of Sperm Competition in a Species of Dung Roller Beetle

Abstract

Contests between males fighting over limited resources often determine the reproductive success of the contestants. It is possible that the outcomes of such contests are affected by traits that also contribute to the likelihood of males achieving paternity when sperm from multiple males compete to fertilize the ova of a single female; however, this relationship has been poorly characterized. In dung and carrion roller beetles, contests among males for the possession of a food balla vital resource for nestingare frequent in nature. However, females that roll and nest with a male often store the sperm of previous mates, forcing males to engage in sperm competition. We analyzed the relationship between wins and losses in contests between food ball owner males and subsequent paternity success in the carrion roller beetle Canthon cyanellus using both na€ ıve (virgin) and experienced (previously mated) males. Owner males that initiated contests were more likely to win, and contest durations were longer between experienced owner males than between na€ ıve owners. The paternity of the winner owner males nesting with a female that had previously mated with another male was higher than for loser owner males, and the paternity of experienced owners also tended to be higher than for virgin owners. Our results indicate that winning and being an experienced male are associated with greater success at fighting and sperm competition than losing and being a na€ ıve male.

Contests over reproductive resources in female roller beetles: Outcome predictors and sharing as an option

“…Fights among male roller beetles for the ownership of a food ball during rolling and nesting have been widely documented [ 26 – 27 , 33 – 34 ], showing that ownership of the food ball, together with size (RHP) asymmetries, predict fight outcome. Our results show that food ball female owners of C .…”

“…Males fight for food which allows the winner to obtain a mate. In Canthon cyanellus cyanellus , a carrion roller beetle, asymmetries in ownership and RHP during male-male contests influence the ability of the contestant to defend or gain food resources for reproduction [ 32 – 34 ]. Furthermore, the reproductive status of both contenders is also related to the chance of winning: previously mated owners have a higher probability of winning than virgin owners.…”

The reproductive behavior of Neotropical dung beetles

“…Another study found that the combat outcome can significantly affect the reproductive success of both combatants. Winning males increase their acquired paternity under conditions of sperm competition compared to loser males in previous combats (Chamorro-Florescano and Favila, 2016;Chamorro-Florescano et al, 2017).…”

“…However, the female may also perform sperm choice of specific phenotypes by shedding sperm and biasing sperm utilization by muscle contractions, among other possible mechanisms (Eberhard, 1996). These mechanisms have not been explored, but it has been reported that C. cyanellus females may benefit certain males having reproductive experience and a successful combat outcome (Chamorro-Florescano and Favila, 2016;Chamorro-Florescano et al, 2017).…”