AN ANALYSIS OF SKELETAL SIZE VARIATION IN MYSTACINA-ROBUSTA DWYER, 1962 (CHIROPTERA, MYSTACINIDAE)

Size variation within the presumably extinct greater short-tailed bat Mystacina robusta is described from a variety of teeth and longbone me asurements. Data from recent specimens collected from Big South Cape a nd Solomon Islands are compared with those from fossil bones, mainly o f Holocene age, from the Waitomo - Hawkes Bay and Martinborough region s of the North Island, and Takaka, North Canterbury and South Canterbu ry in the South Island, New Zealand. Variation is clinal, with size de creasing significantly southwards. The hypothesis is proposed that thi s clinal variation is a net response to two selection pressures. First ly, it was advantageous for M. robusta to be relatively large to explo it the abundant macro-invertebrates and microvertebrates available on the forest floor. Secondly, large size would have been increasingly co ld-limited towards the south, where the energy required to rewarm the animals from the near-ambient temperatures reached during torpor was g reatest.