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The biology and evolution of the reproductive cycle of Miniopterus schreibersii and M. australis (Chiroptera: Vespertilionidae)

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Abstract

The reproductive biology of Miniopterus schreibersii and M. australis was studied at latitude 28·5°S, in eastern Australia. Comparison was made with material from 23·5°S to 37°S.

Both species are monoestrous and monotocous. Ovulation is from the left ovary and implantation is in the right cornu. At latitude 28·5°S, a “silent heat” precedes behavioural oestrus and fertilization by two months in M. schreibersii and three months in M. australis. In M. schreibersii copulation and fertilization occur in late May and early June, immediately after a relatively short period of spermatogenesis and about one month after the release of sperm to the epididymides. During winter, implantation of the blastocyst stage is delayed. The male accessory glands involute but a store of epididymal sperm is retained. Implantation occurs in August and birth is in December.

M. australis conceives in mid-August, after an extended period of spermatogenesis which ceases four to six weeks prior to copulation. An epididymal sperm store is present some 21/2 months prior to insemination. Implantation has occurred by mid-September and parturition takes place in December.

Comparative data from other latitudes in eastern Australia show no differences in the timing of a reproductive events of M. australis between 23·5°S and 31°S. In M. schreibersii in South Australia (37°S) mating occurs in April and May. Plasticity in the timing of parturition (October to December) and other anomalies of this population are discussed.

The data suggest that evolutionary hypotheses involving extrapolation from one species to the other are questionable and that a more complex and varied adaptive response to climate may exist than has hitherto been supposed.

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