ABSTRACT
The study area is located in one of the most arid regions of the planet, in the north-west portion of Mexico and the south-west of the United States. This area comprises the biogeographical region of the Californias, which encompasses a portion of the richest state in the American Union, California, and perhaps the most conflictive peninsula in Mexico, Baja California, where this study is focused. Up to 1848 this region belonged to a single entity, not only from a biological perspective but also from a geopolitical point of view, since California formed part of Mexico. Since then, Baja California has remained a part of the Mexican Republic, and California has been a part of the United States of America.
