DataSheet_1_Accessory gland size increases with sperm competition intensity in Cataglyphis desert ants.docx

In many species, females have multiple mates, whose sperm compete for paternity. Males may subsequently invest in the increased production of sperm and/or seminal fluid. The latter is a complex mixture of proteins, peptides, and other compounds generated by the accessory glands (AGs) and is transferred to females along with a male’s sperm. Seminal fluid is known to be a key determinant of competitive outcomes among sperm, and its production may trade off with that of sperm. We show that AG size—a proxy for seminal fluid production—has a positive and phylogenetically robust correlation with both sperm competition intensity and sperm production in nine species of Cataglyphis desert ants. These results indicate a lack of trade-off between sperm production and seminal fluid production. They underscore that sperm competition may strongly shape sperm traits and could drive reproductive performance in eusocial hymenopterans.