Experimental evolution of sperm competitiveness in a mammal

• Published in: BMC evolutionary biology Vol. 11; no. 1; p. 19
• Main Authors: Firman, Renée C, Simmons, Leigh W
• Format: Journal Article
• Language: English
• Published: London BioMed Central 20.01.2011; BioMed Central Ltd; BMC
• Subjects: Animal reproduction; Animal Systematics/Taxonomy/Biogeography; Animals; Biological Evolution; Biomedical and Life Sciences; Competition; Deoxyribonucleic acid; DNA; Embryo; Embryos; Entomology; Evolution; Evolutionary Biology; Experiments; Female; Females; Fertility; Genetic aspects; Genetics and Population Dynamics; Genotype; Genotype & phenotype; Life Sciences; Male; Males; Mice - genetics; Mice - physiology; Microsatellite Repeats; Phenotype; Physiological aspects; Polygamy; Research Article; Sperm; Sperm Count; Sperm Motility; Spermatozoa; Spermatozoa - cytology; Australia; Selection Line; Fertilisation Success; Sperm Competition; House Mouse; Sperm Quality
• ISSN: 1471-2148; 1471-2148
• DOI: 10.1186/1471-2148-11-19

Background When females mate with multiple partners, sperm from rival males compete to fertilise the ova. Studies of experimental evolution have proven the selective action of sperm competition on male reproductive traits. However, while reproductive traits may evolve in response to sperm competition, this does not necessarily provide evidence that sperm competitive ability responds to selection. Indeed, a study of Drosophila failed to observe divergence in sperm competitive ability of males in lines selected for enhanced sperm offence and defence. Results Adopting the naturally polygamous house mouse ( Mus domesticus ) as our vertebrate model, we performed an experimental evolution study and observed genetic divergence in sperm quality; males from the polygamous selection lines produced ejaculates with increased sperm numbers and greater sperm motility compared to males from the monogamous lines. Here, after 12 generations of experimental evolution, we conducted competitive matings between males from lineages evolving under sperm competition and males from lineages subject to relaxed selection. We reduced variation in paternity arising from embryo mortality by genotyping embryos in utero at 14 days gestation. Our microsatellite data revealed a significant paternity bias toward males that evolved under the selective regime of sperm competition. Conclusion We provide evidence that the sperm competitiveness phenotype can respond to selection, and show that improved sperm quality translates to greater competitive fertilisation success in house mice.