Part 2

Considering its extensive geographic range and its occurrence in many contrasting environments, Myotis velifer varies little; and the variation that does occur is continuous. The change from the large, dark Mexican subspecies to the small, pale Arizonan subspecies is gradual. The reason may lie in the ecology of M. velifer. It seems that there are few barriers separating populations. Waterless areas and regions lacking suitable roosting places such as fissures in cliffs and outcrops of rocks, caves and buildings, may exclude the species from certain areas, but there are few areas of any great size within the range of the species that lack these features. Also, these bats are strong fliers; even between fairly distant colonies there may be considerable gene flow. The geographic variation observed probably is the result of adaptation, on the part of populations in different parts of the range of the species, to different environments. The lack of any effective barriers except possibly distance between populations tends to limit subspeciation and to cause gradual variation between subspecies. M. v. peninsularis, the subspecies at the southern tip of Baja California, is not considered in this discussion. So far as known, however, that subspecies is completely isolated from the mainland populations of M. velifer.

For the opportunity to examine specimens under their care I wish to thank Dr. William H. Burt of the University of Michigan Museum of Zoology, Dr. Rollin H. Baker of the Museum of Natural History of the University of Kansas, and Dr. Donald F. Hoffmeister of the University of Illinois Museum of Natural History. I am indebted also to persons in charge of the Biological Surveys Collection and the National Museum for the loan of critical material, and to Dr. E. Raymond Hall for suggestions. The following symbols are used to designate the source of specimens: BS--Biological Surveys Collection, IM--University of Illinois Museum of Natural History, KU--Museum of Natural History of the University of Kansas, MM--University of Michigan Museum of Zoology, NM--United States National Museum, TV--collection of Terry A. Vaughan.

Specimens examined.--Total, 110, distributed as follows:

=Arizona=: Mohave Co.: Big Sandy Creek, 3 BS. Yavapai Co.: Camp Verde, 3 KU. Gila Co.: 5 mi. SW Roosevelt, 8 BS. Maricopa Co.: Gila Bend, 1 BS. Graham Co.: Snow Flat, Graham Mountains, 1 IM; Bonita, Graham Mountains, 1 IM. Pima Co.: Tucson, 1 NM; Madera Canyon, 5000 ft., Santa Rita Mountains, 2 KU. Santa Cruz Co.: Madera Canyon, 6000 ft., Santa Rita Mountains, 2 KU. Cochise Co.: 8 mi. W Fort Huachuca, 26 IM; Hereford, 4 IM; 3 mi. SW Hereford, 1 IM; 14 mi, SW Fort Huachuca, 1 IM; San Bernardino Ranch, 4 NM.

=California=: Riverside Co.: Riverside Mountains, 35 mi. N Blythe, 51 (21 KU, 30 TV).

=Sonora=: Santa Maria Mine, El Tigre Mountains, 1 MM.

Transmitted March 22, 1954.