Douglas et al : Geographic variation in cranial morphology of Stenella longirostris 



61 



high correlations (Table 3) with 

 all characters except Tooth W. 

 and Skull W. (at Parietals). Local- 

 ities to the right in Figure 3 are 

 from the Hawaiian Island area 

 (0702 and 0802; see Fig. 4), where 

 animals are larger. Specimens 

 from southern blocks (e.g., 0116, 

 0117, 0313) also are larger than 

 animals from other parts of the 

 range. Blocks to the left in Fig- 

 ure 3, with negative loadings on 

 component I, have snialler indi- 

 viduals. In general, S. longiros- 

 tris from the northeastern blocks 

 were the smallest (e.g., 0515, 

 0613, 0612). 



Component II has its highest 

 positive correlations with Skull 

 W. (at Parietals), Ht. Braincase, 

 and Tooth W. ; it has negative 

 associations with characters 23- 

 26, which involve numbers of 

 teeth. Block 0507 is the most ex- 

 treme, with a positive projection 

 on this component (see Fig. 3); 

 animals from this block have 

 relatively wide skulls and re- 

 duced numbers of teeth. In con- 

 trast, block 0516 is at the other extreme, 

 with relatively narrow skulls and greater 

 numbers of teeth. 



Figure 5 is a dendrogram depicting 

 results from a UPGMA cluster analysis 

 of the 25 geographic blocks. Four main 

 clusters are evident, with block 0702 

 being the most divergent and in its own 

 cluster. Block 0507 also is in a cluster by 

 itself. The first group in the diagram (i.e., 

 blocks 0116 through 0516 at top of Fig. 

 5) includes predominantly southern and 

 western localities. Those in the largest 

 cluster (listed from block 0411 to 0509 in 

 Fig. 5) are situated to the north and/or 

 east. 



A modified skyline diagram (Fig. 6A) 

 resulting from function-point clustering 

 for 25 blocks based on 30 characters in- 

 dicates an initial separation of block 0702 

 (which includes part of Hawaii) from the 

 others. At a w-value of 3.50, there are 

 three clusters: (1) block 0702; (2) the 

 southern blocks in addition to blocks 0508 and 0802; 

 and (3) the remaining northern and eastern blocks, in- 

 cluding those just north of the Equator. Further sub- 



Figure 4 



Geographic variation in principal component I. Bar represents range (low to high block 

 values), and midpoint is marked. Darkened part of bar indicates value for particular block. 



00 



I 



^ 



<s 



^ 



- 0116 

 -0117 



- 0216 

 -0215 

 -0313 



- 0508 



- 0315 



- 0002 

 -0516 

 -0411 



- 0615 

 -0312 

 -0505 

 -0612 

 -0614 

 -0613 



- 0417 

 -0512 

 -0514 

 -0513 

 -0506 

 -0505 

 -0509 

 -0507 

 -0702 



Figure 5 



Distance phenogram summarizing UPGMA clustering of 25 blocks based on 

 30 characters. Cophenetic correlation is 0.80. 



division results with smaller w'-values (see Fig. 6A). 



A similar analysis (Fig. 6B) was conducted using 



the five characters— Postorbital W., L. Rostrum (frm. 



