RODENTS OF LIBYA 29 



The Cyrenaican Plateau, in view of its unique ecologic and climatic 

 regimen, has a surprisingly- depauperate rodent fauna. The absence of 

 endemic subspecies in an area so distinct ecologically is most surprising. 

 The most logical explanation for this lack of differentiation in the 

 populations of rodents occurring here may be the close proximity of the 

 coastal plain and, in many places, the continuity of similar habitats 

 between it and the uplands of the plateau, which have allowed for 

 genetic interchange between populations of rodents occurring in both 

 areas. 



The Coastal Plain Province has a richer rodent fauna than the 

 Cyrenaican Plateau probably because of its larger area and its greater 

 diversity of habitats. Although rainfall is more seasonal on the coastal 

 plain, falling mostly during a comparatively short winter period, 

 there are much greater local fluctuations in daily and yearly temper- 

 atures. Most inland areas of the coastal plain are contiguous with 

 the Saharan steppe and tend to be somewhat arid. Some portions of 

 the coastal plain, in floral composition and climate, do not differ 

 appreciably from the Saharan steppe. This ecologic and climatic 

 diversity has increased significantly the number of habitats available 

 to mammals, and the rodent fauna is accordingly more diversified. 



The most characteristic species of rodents of the Coastal Plain 

 Province are: Gerbilbis eatoni; Gerbillus henleyi; Meriones libycus; 

 Psammomys obesus; Jaculus orientalis; and Allactaga tetradactyla. All 

 of these species except Jaculus orientalis, which occurs on the Cyrenai- 

 can Plateau and Gebel Nefusa, are restricted to the coastal plain. 

 Most of these coastal species have developed subspecies in response 

 to local differences in the character of the coastal plain. Thus Gerbillus 

 eatoni is divisible into three subspecies, G. e. eatoni, with a broad 

 range covering the southern margins of the Gulf of Sirte; G. e. inflatus, 

 which is confined to the coastal plain of extreme northeastern Cyrena- 

 ica; and G. e. versicolor, whose range includes the coastal plain of the 

 eastern margins of the Gulf of Sirte. 



The sand rat, Psammomys obesus, is represented by two subspecies, 

 P. o. obesus and P. o. tripolitanus, which are confined, respectively, to 

 the coastal plains of northeastern Cyrenaica and the Gulf of Sirte. 



Meriones libycus is also divisible into two coastal subspecies. 

 The range of Meriones libycus auratus includes all coastal areas of 

 Tripolitania and those areas adjoining the southern margins of the 

 Gulf of Sirte, while Meriones libycus azizi is confined to the coastal 

 plain of northern Cyrenaica. 



The species Gerbillus henleyi and Jaculus orientalis inhabit large 

 portions of the Libyan coastal plain but have not differentiated 

 sufficiently in Libya to warrant division into subspecies. The raono- 

 typic species, Allactaga tetradactyla, likewise has not formed subspecies. 



