172 



F. E. PEABODY AND J. M. SAVAGE 



trans-valley leak, hence the Sierran population must be a recent 

 introduction across the valley. The only other trans-valley leak 

 noted seems to have occurred in the distribution of the limbless 

 lizard, Anniella pulchra, which is a Madro-Tertiary species. Again, 

 the leak has been from west to east, near the position of the delta. 

 It is not known if moisture has been the critical factor here as it 

 surely has been for the salamanders, or whether the leak is indeed 



ARBOREAL SALAMANDER 

 ANEIDES LUGUBRIS 



TRANS- / 

 \ VALLEY / 



\"LEAK" / 



\ ' 



Fig. 8. Distribution of arboreal salamander, Amides luguhris. Note 

 trans-valley leak, which probably occurred in pluvial times and estab- 

 lished species in Sierra foothills. 



genuine (the supposed leak may represent an inadequately known 

 distribution of the lizard northward along the entire eastern side of 

 the Great Valley). The few occurrences of trans-valley leaks em- 

 phasize the overall efificiency of the Great Valley as a barrier to 

 transverse dispersal between the corridor and the Sierras except at 

 the north and south ends. Finally, no Arcto-Tertiary species appears 

 to have moved down the corridor and back up the Sierras, or vice 

 versa. Dispersals southward along the corridor and along the Sierras 

 have remained largely separated in southern California in coastal 

 lowland and interior highland, or have achieved only limited 

 sympatry there. 



