Page 5 - 1991_Hutterer

Variation and evolution of the Sicilian shrew 245

Size (%)

120.-----------------------------------------~

Si ze reduction of Crocidur a sicu la
110

100

90

80
70

60 MALTAIGOZO SICILY/EGADI

50+------,------,------,------.,------------~

Malta EP Ma l ta UP Malta NL Gozo Sicily UP Sicil y Egadi

Localities l Periods

-Tibia -+- Mean skull values

Fig. 4: Size reduction of Crocidura sicula from the Pleistocene to Present. Mean values for
tibia length and for five skull measurements expressed as percentages of the Pleistocene
population of Ghar-Dalam Cave, Malta. EP = Early Pleistocene, UP = Upper Pleistocene,
NL = Neolithic, other samples from extant populations.

also counts for the tooth size, for example of M3 (Tab. 2). A detailed comparison
(Tab. 3) also shows that the extant populations differ considerably in their dimen-
sions, Sicly being largest, and Gozo and Egadi smallest. lt is also interesting that the
size reduction is more pronounced for the tibia length than for the skull size (Fig. 4).

Discussion

No substantial character differences could be found between Pleistocene shrews of
Malta and Sicily, previously referred to C esuae, and between Holocene and Recent
populations of C sicula. Moreover, it was found that the tibia length varies with .
body size. Therefore I see no reason to distinguish different species in this group.
This conclusion is also supported by the low genetica! distances reported by Mad-
dalena & Vogel (1990). However, a temporal size reduction of 25 ll7o has never been
documented for a shrew and seems quite unusual. Fig. 4 also shows that the ex-
tremities suffered more size reduction than the skull, which seems logica!, as there
appears to be a limit for the reduction of the brain and dentition. However, it remains
unknown whether a part of the tibia-lengthening was due to adaptive processes. An
answer to this question would require a detailed knowledge of the landscape of
Malta and Sicily during the Pleistocene. Today, large parts of these islands are
covered by rocky country, a condition which would favour adaptations for climbing,
including lengthening of the limbs.

The conformity of the Pleistocene populations of Malta and Sicily and the diversi-
ty of the extant island populations is easily explained by looking at the geologica!
setting of the area (Fig. 1). According to Donn et al. (1962) and other authors,