Date of Completion


Degree Type

Honors Thesis - Campus Access


Biology (BIOL)

First Advisor

Dr. Martina Ramirez


In a study of the phylogeny and biogeography of the fossorial coastal dune spider Lutica, Ramirez & Beckwitt (1995) found that the mainland populations of new species A and B are only about 57 km apart at their southern and northern boundaries respectively [between La Jolla Beach, Ventura County and the Ballona Wetlands, Los Angeles County], yet spiders from these regions are members of different taxa. To determine if this north-south disjunction is also seen in other southern California spiders, this study investigated the genetic differentiation and biogeography of silver garden spiders (Argiope argentata), a species whose distribution includes coastal populations both north and south of the Ballona Wetlands. This was accomplished by the genetic characterization of spider samples from A. argentata populations from Ventura County to San Diego County, using allozyme electrophoresis as the molecular assessment technique, given its cost-effectiveness for large samples. The results of this study the existence of three distinct population groups: Group A- Leo Carillo State Park (LC) to Point Dume State Beach (PD); Group B- Malibu Bluffs Park (MB) to Palos Verdes Drive South (PVD); and Group C- Bolsa Chica Ecological Reserve (BC) to Crest Canyon Park (CRC). This pattern may reflect the influence of the historic north-south biogeographic disjunction noted by Ramirez & Beckwitt (1995).