352 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1926 
peratures would everywhere surround an animal staying below- 
ground; but a fact bearing on this suggestion is that the high- 
mountain gophers all winter do extensive burrowing through the 
snow, thereby reaching in safety stems of plants above the ground 
surface ! 
Returning now to the subject of isolation of high-mountain types 
on disconnected mountain masses, interesting examples are afforded 
on the highest mountains of southern California by members of the 
alpinus group. These are alpinus, in the vicinity of Mount Whit- 
ney; neglectus, on Mount San Antonio, of the San Gabriel Range; 
altivallis, on the San Bernardino Mountains; and jacinteus, on San 
Jacinto Peak. As a rule, low-level types of gophers intervene in the 
low passes between these boreal colonies, sequestered as they are by 
some factor involved in altitude. As a further example of montane 
sequestration we find at the north, in the monticola group, premazdl- 
laris set apart on the Yolla Bolly Mountains. But, curiously, we find 
mazama, of the same group, on the Trinity Mountains and on the 
LIFE ZONES 
ARCTIC ALPINE 
HUDSONIAN 
CANADIAN 
TRANSITION 
UPPER SONORAN 
LOWER SONORAN 
SEA LEVEL 
Fig. 2.—Sectional profile of the Sierra Nevada through the region of Yosemite, showing 
the location of the species and subspecies of pocket gopher according to altitude and life 
zone. 
Siskiyou Mountains, both these representations without any detect- 
able differences between them, separated by the valley of the Klamath 
River. This intervening valley is occupied by lewcodon, a member 
of the bottae group. 
With respect to differentiation within the lowland groups, we 
find an obvious association of the areas of differentiation with dif- 
ference in climatic humidity—rainfall, or perhaps cloudiness. In 
this connection, the general northwest-southeast trend of the areas 
of occupancy of the different members of the bottae group is sig- 
nificant. Comparison of this map of gopher distribution with a 
rainfall map of California shows the parallel. ‘Take an east-west 
section, gopherwise, from the coast at Santa Cruz, and we find 
bottae inhabiting the narrow, most humid, coastal belt; in the in- 
terior San Benito or other valleys, of lesser rainfall, we find 
angularis; on the hard-soiled, juniper-clothed ridges of the Diablo 
range, is diaboli; beyond this on the floor of the San Joaquin 
