Holocene biogeography of the southwestern European white-toothed shrew (Crocidura iculisma, Eulipotyphla) through its fossil record

Abstract

1. Crocidura iculisma is a shrew showing a fragmented distribution limited to the Iberian Peninsula, southern and western France. Although it has been in the Iberian Peninsula since the Middle Pleistocene, its biogeographical history remains poorly known. 2. Here, we provide new data on Crocidura iculisma from the Castillejo del Bonete site (southern Spain). At the same time, we analyse changes in its geographic distribution based on its palaeontological record. 3. We have reviewed thoroughly the Holocene record of Crocidura iculisma in southwestern Europe considering independently the three time intervals according to the stages defined for this geological time series. The relative abundance of the two sympatric shrews of the genus Crocidura in fossil sites was analysed. The data obtained concerning its past distribution range and relative abundances were compared with the current status of the species to interpret changes through time. 4. The southwestern European white-toothed shrew has undergone a relevant regression in its distribution range in the Iberian Peninsula until today. The occurrence at Castillejo del Bonete besides other palaeontological records located beyond its current distribution range show that it was distributed in several areas of the eastern part and southern interior of Iberia, at least until the second half of the Meghalayan. Relative abundance patterns observed in the fossil assemblages suggest that competitive exclusion by C. russula and climatic changes played a crucial role in driving the extirpation of C. iculisma from a substantial portion of the Iberian Peninsula.