Consistent patterns of male mate preference in the laboratory and field

Mate preference by males is a widely observed phenomenon; however, it is not well understood how these preferences are expressed in wild populations. Most studies that describe the expression of male mate preference in the wild tend to observe assortative mating, where higher quality males express a strong preference for high quality females while low quality males express either no preference or a preference for low quality females. We examined male mate preference in Bolitotherus cornutus, the forked fungus beetle, a system that exhibits male–male combat and protracted male courtship. We conducted no-choice trials in the laboratory and monitored male courtship in a wild population. In the laboratory, we found a strong preference for larger, more fecund females across all sizes of males. Results from the field were similar to those in the lab; larger females were courted more often, and there was no relationship between the size of a male and the mean size of females he courted (i.e., no assortative mating). This study documents an unusual pattern of expression of male mate preference in the wild and suggests that mate preference by males may be underappreciated in species with intense male–male competition and non-assortative mating. While males of many species express a preference for high-quality females, their preferences can change in complex social situations such as those in wild populations, often resulting in pairing for quality. However, recent mathematical theory suggests that male preference could evolve in a variety of social contexts. We studied the mate preferences of male forked fungus beetles in the laboratory and a wild population. In the lab, males of all sizes preferred larger females. In the complex social environment of a wild population, males still preferred larger females even though there was a strong male-male competition. There was no pairing for quality as often observed in other species. These results suggest that male mate preferences may evolve in a variety of systems not just those with flexible preferences and pairing for quality.