Breeding Systems of Spinifex Hopping Mice (Notomys-Alexis) and Plains Rats (Pseudomys-Australis) - a Test for Multiple Paternity Within the Laboratory

Abstract

This study was carried out as part of a broader investigation into the factors that determine interspecific variation in testis size amongst conilurine rodents. The hypothesis proposed is that the huge differences in absolute and relative testis size between the spinifex hopping mouse (Notomys alexis) and the plains rat (Pseudomys australis) relate to differences in breeding system. One aspect of a species' breeding system, the capacity for multiple paternity, was assessed under laboratory conditions for each species. Allozyme markers were used to set up appropriate trios consisting of one female cohabiting with two mates of different genotypes and to assess the paternity of the resultant pups that were born. Multiple paternity within a single litter was not recorded for hopping mice but was observed occasionally in plains rats, a result consistent with the hypothesis under test.