Sperm competition and evidence of sperm fertilization patterns in the carrion ball-roller Canthon cyanellus cyanellus LeConte (Scarabaeidae: Scarabaeinae)

Field observation and laboratory experiments were conducted to investigate sperm competition and pat- terns of sperm fertilization under different experimental conditions in the carrion ball-roller beetle Canthon cyanel- lus cyanellus. Males in nature can mate with females whose spermathecae contains fertile sperm from other males. Sperm precedence was investigated using a visible genetic marker. The progeny of red (homozygous recessive) virgin females mated once with a red male and afterward, once with a green beetle (homozygous dominant) and vice versa, revealed that regardless of its color, the last male to mate fertilized c.a. 50% of the eggs, suggesting strong sperm competition. Males were able to achieve higher levels of pa- ternity (more than 80%) when mated ad libitum with previ- ously mated females, although large amount of variance in paternity does not exclude the possibility of first male sperm precedence or female cryptic choice. These results suggest that repeated mating and sperm replacement are the mech- anisms by which last males achieve sperm precedence.