A potential microevolutionary life‐history trade‐off in White‐Footed Mice (Peromyscus leucopus)

Abstract

Summary 1.Reproductive costs can affect survival and future reproduction. In winter and in short photoperiods, some individuals within populations of temperate-zone rodents inhibit reproduction and decrease food intake, while others do not. 2. Two lines derived from a natural population of White-Footed Mice and selected to maintain or inhibit reproduction in short photoperiod were tested for two potentially correlated responses to selection: changes in food intake and body mass. Mice were raised to age 70 days in short or long photoperiod, following which testis size, body mass and food intake were measured over a 2-week period. 3. In both lines and both photoperiods, there was an apparent response to selection in testis size and a correlated response to selection in food intake but not body mass. In both photoperiods, mice in the line selected for winter reproduction ate 50% more than mice in the line selected for winter reproductive inhibition. Mice in an unselected control line were intermediate for testis size and food intake. 4. The increased food intake in a line of mice with a genetic tendency for winter reproduction suggests a potential cost of winter reproduction and a potential microevolutionary trade-off related to this cost of reproduction.

Testosterone does not mediate variation in basal metabolic rate and activity in relation to reproductive condition and photoperiod in white‐footed mice (Peromyscus leucopus)

“…We found a significant difference in food intake between T and C mice in SD with no significant difference in total body mass, which is consistent with previous studies of these mice (Heideman et al, ; Kaseloo et al, ). Average testosterone and dry seminal vesicle mass were also significantly different between the two treatments and were significantly correlated with each other, providing evidence that the testosterone implants effectively introduced the hormone into the mice.…”

Number of Immunoreactive GnRH‐Containing Neurons Is Heritable in a Wild‐Derived Population of White‐Footed Mice (Peromyscus leucopus)

“…Alternatively, higher numbers of IR-GnRH neurons might provide sufficient GnRH to support reproduction in the presence 1.0 .03 .14 of some inhibitory inputs, such as short photoperiod. Consistent with the suggestion that factors other than number or activity of GnRH neurons may regulate reproductive organ mass in SP is the observation that food intake was correlated with reproductive organ mass in SP, but not LP, in this population (Heideman et al 2005). We propose the hypothesis that, in the natural source population, a higher number of IR-GnRH neurons provides sufficient GnRH secretion to maintain reproduction in spite of inhibition by winter photoperiods.…”

Variation in levels of luteinizing hormone and reproductive photoresponsiveness in a population of white-footed mice (Peromyscus leucopus)

“…We predicted that levels of LH would be lower in a line of mice artificially selected for strong suppression of reproduction in short-day photoperiods (SD) than in a line of mice artificially selected against suppression of reproduction in SD. We tested levels of LH in both SD [ (19,21). The hypothesis was tested in ovariectomized females with constant-release implants of estradiol from two divergent selection lines held in LD or SD.…”