The role of photoperiod in the timing of reproduction in the Dasyurid Marsupial Antechinus stuartii.

Antechinus stuartii has one highly synchronized mating period which occurs at the same time each year. An analysis of the time of reproduction in 162 populations of A. stuartii shows that the onset of the mating period is correlated with the rate of change of photoperiod, rather than with critical photoperiodic length. The rate of change of photoperiod is different for two designated forms of this species and can be used as a predictor of these animals' reproductive timing. A rate of change model further explains the rigid and highly sunchronized nature of the mating period and, by providing a mechanism for reproductive isolation, offers an explanation for the evolution of the two forms of this species.