Pernn et al.: Geographic variation in cranial morphology of Stenella attenuata 



327 



obtained by repeating the analysis at different clus- 

 tering levels. Results are displayed in modified sky- 

 line diagrams (Wirth et al., 1966). 



Using standardized data, we constructed scatter 

 diagrams by projecting blocks onto the first two 

 principal components (Sneath and Sokal, 1973) ex- 

 tracted from a matrix of correlations among the 30 

 characters. Canonical-variates analysis also was 

 employed to obtain the subset of variables that 

 shows the greatest interblock separation relative to 



intrablock variation (Program P7M of BMDP statis- 

 tical software; Dixon, 1990). Plots of the first two 

 canonical variables show the maximum separation 

 of blocks in two-dimensional space. 



Mantel test for geographic patterning 



A Mantel ( 1967) test was used to assess interlocality 

 variation in each character and determine whether 

 measures are geographically patterned or, alterna- 



