Je. Maldonado et al., INTRASPECIFIC GENETIC DIFFERENTIATION IN CALIFORNIA SEA LIONS (ZALOPHUS-CALIFORNIANUS) FROM SOUTHERN CALIFORNIA AND THE GULF-OF-CALIFORNIA, Marine mammal science, 11(1), 1995, pp. 46-58
Intraspecific patterns of mitochondrial DNA sequence variation were de
termined among California sea lions (Zalophus californianus california
nus) from three colonies along the Pacific coast of southern and Baja
California and one colony in the Gulf of California. We found no varia
tion in 368 base pairs (bp) of cytochrome b sequence among 40 sea lion
s from these localities, but analysis of 360 base pairs of control reg
ion revealed eleven genotypes. The four genotypes found in the Gulf of
California population were unique and phylogenetically distinct from
those found in sea lions along the Pacific coast. The average sequence
divergence between Gulf and Southern California genotypes was 4.3%, s
uggesting a relatively long period of isolation. However, colonies alo
ng the Pacific coast, which are less than 200 km apart, shared mtDNA g
enotypes, indicating that recent genetic exchange has occurred between
them. Therefore, we suggest that regional female philopatry exists in
California sea lions. Regional boundaries may be related to oceanic c
urrents or patchiness in the distribution of resources. Further resear
ch is needed to better understand the underlying causes of genetic dif
ferentiation in the California sea lion.