WAPLES and ROSENBLATT: LARVAL DRIFT IN SOUTHERN CALIFORNIA 



35' 



30' 



25« 



T 1 1 r 



125° 



120° 



116° 



110° 



Figure 2.— Location of positive collections of Caulolatilus princeps larvae taken in CalCOFI sam- 

 pling program, 1955-59. 



terms of life history features. Given the larval cap- 

 ture data discussed above, it is not difficult to under- 

 stand v^hy the inclusion of data for C. princeps tends 

 to obscure patterns of genetic differentiation shared 

 by the other species. 



Two other species are exceptions (albeit not as 

 dramatic exceptions as C. princeps) to the recurring 

 patterns discussed above. Girella nigricans is the 

 only species for which the Channel Islands was 

 found to be the most genetically divergent locality 

 (Table 3), and S. pulcher is the only species apart 

 from C. princeps for which a strong Punta Eugenia- 

 Guadalupe connection was observed (Table 4). The 

 pattern in S. pulcher is due to loci for which consis- 

 tent heterozygote deficiencies were found (Waples 

 1986) and thus may provide information that is un- 

 related to actual levels of gene flow. Girella nigri- 



cans was the only species to be collected primarily 

 as juveniles; these samples largely comprise a single 

 year class, the allele frequencies for which might be 

 prone to short-term variations. Sampling of juve- 

 niles might thus have been expected to yield rela- 

 tively high levels of genetic divergence, but there 

 was no a priori reason to expect the particular pat- 

 tern of D values found in this species. 



Whether the results for G. nigricans are due to 

 as-yet-undetected processes of larval transport or 

 merely random noise in our analysis is thus unclear 

 at present. We face a similar difficulty in explain- 

 ing the heterogeneity (even among the "core" 

 species) in patterns of genetic affinities between the 

 two northern and two southern populations (Table 

 4). The decision to include a large number of species 

 in this study mandated a geographically restricted 



