RODENTS OF LIBYA 61 



Conclusions 



This study of Libyan rodents is based primarily on specimens 

 obtained by the author during the period from October 1961 to July 

 1962 and is the first attempt to provide a comprehensive treatment 

 of the taxonomy and distribution of the Libyan rodents based upon 

 actual specimens and field experience. 



Fifty-six kinds of rodents comprising 7 families, 14 genera, 28 

 species, and 4S subspecies occur in Libya. In this report, 20 subspecies 

 are described as new, and 3 forms, Gerbillus aureus, Meriones caudatus, 

 and Jaculus deserti, which had previously been regarded as subspecies, 

 are elevated to full species. 



Species belonging to the genera Gerbillus, Meriones, and Jaculus 

 show the widest range of geographic and individual variation found 

 among the Libyan rodent fauna. The polytypic species Gerbillus 

 campestris, Gerbillus gerbillus, and Jaculus jaculus, each represented 

 in Libya by 5 subspecies, are the most widely distributed and the 

 most genetically variable of any of the Libyan rodents. 



Libyan rodents usually do not conform to climatic or ecogeographical 

 rules, such as Bergmann's or Allen's rule, and geographic variation in 

 response to selective factors of the environment is most apparent in 

 the cryptic coloration of the "substrate races" of Gerbillus campestris 

 and Meriones caudatus. 



The populational structure of Libyan rodents is characterized by 

 two primary components. These are geographical isolates and, less 

 frequently, a series of contiguous populations showing progressive 

 change in morphological characters (clines). It is probable that 

 in Libya most species have arisen as a result of the genetic divergence 

 of peripheral isolates. Gradual speciation, as opposed to instantaneous 

 speciation or macroevolution, has been the prevailing mode of specia- 

 tion for Libyan rodents. Of the two types of gradual speciation, geo- 

 graphic, rather than sympatric, has played the primary evolutionary 

 role. 



Three faunal areas, which coincide roughly with the major physi- 

 ographic, vegetative, and climatic features, are recognizable in Libya 

 based on the distribution of the rodent fauna. Each of these faunal 

 areas is divisible into two regional provinces according to the kinds 

 of rodents most typical of each. The faunal areas of Libya and their 

 provinces are: The Mediterranean Faunal Area which is comprised 

 of the Coastal Plain Province and the Cyrenaican Plateau Province; 

 the Saharan Steppe Faunal Area consisting of the Transitional 

 Desert Province and the Tripolitanian Gebel Province; and the 

 Saharan Desert Faunal Area which includes the Cyrenaican Desert 

 Province and the Fezzanese Desert Province. 



