Aethomys chrysophilus (Rodentia: Muridae)

The genus Aethomys currently includes 11 species, but recent evidence indicates a need for taxonomic revision of the genus. Aethomys chrysophilus (De Winton, 1897) is a muroid rodent commonly called the red veld rat. A medium-sized rodent with a long, sparsely haired tail, A. chrysophilus is largely parapatric with its sibling species, A. ineptus, and in areas of co-occurrence, determination of chromosome number, mitochondrial DNA analysis, or morphology of spermatozoa are required to distinguish A. chrysophilus from A. ineptus. Endemic to Africa, A. chrysophilus is found in savanna–woodland habitats that include varying combinations of grass–herbaceous ground cover, shrub understory, and miombo or mopane woodlands. It is not of special conservation concern.Centre of Excellence for Invasion Biolog

Aethomys ineptus (Rodentia: Muridae)

Aethomys ineptus (Thomas and Wroughton, 1908), commonly called the Tete veld rat, is a medium-sized rodent with a long, sparsely haired tail and spermatozoa with spatulate-shaped heads (unique for all muroid rodents thus far examined). A. ineptus co-occurs with its sibling species, A. chrysophilus, and in areas of co-occurrence, an examination of spermatozoa, diploid number, allozymes, or mitochondrial DNA is required to distinguish the 2. Previous work described as many as 11 species of Aethomys, but recent evidence indicates a need for taxonomic revision of the genus. Endemic to Africa, A. ineptus prefers habitats where there is substantial cover in the form of shrubs, rocks, and herbaceous vegetation. It is not of special conservation concern.Centre of Excellence for Invasion Biolog

Sperm competition and the evolution of male reproductive anatomy in rodents

Sperm competition is a pervasive selective force in evolution, shaping reproductive anatomy, physiology and behaviour. Here, we present comparative evidence that varying sperm competition levels account for variation in the male reproductive anatomy of rodents, the largest and most diverse mammalian order. We focus on the sperm-producing testes and the accessory reproductive glands, which produce the seminal fluid fraction of the ejaculate. We demonstrate a positive association between relative testis size and the prevalence of within-litter multiple paternity, consistent with previous analyses in which relative testis size has been found to correlate with sperm competition levels inferred from social organization and mating systems. We further demonstrate an association between sperm competition level and the relative size of at least two accessory reproductive glands: the seminal vesicles and anterior prostate. The size of the major product of these glands—the copulatory plug—is also found to vary with sperm competition level. Our findings thus suggest that selection for larger plugs under sperm competition may explain variation in accessory gland size, and highlight the need to consider both sperm and non-sperm components of the male ejaculate in the context of post-copulatory sexual selection