FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA 



SOUTHWEST MONSOON (APR- SEPT) 



No./m' 



a 



0.01 -0.1 



D 



0.1 1 - I 



 



I.OI - 10 



40°E 



NORTHEAST MONSOON (OCT -MAR) 



4(yE 



120° 



120° 



I.O.S.N. SAMPLES 



Figure 38. — Abundance of Pontellina morii and P. plumata in Indian Ocean Standard Net (lOSN) collections. Samples 

 collected during southwest and northeast monsoon seasons. Dots represent localities sampled. Abundance values are 

 estimated number of adults per m^ water strained. 



P. morii and plumata exhibit distinctive dis- 

 tributions in both monsoon seasons (Figure 38) 

 as well as general zonal separation (Figure 39), 

 differences that are blurred in charts prepared 

 without regard for seasonal variation (e.g., 

 Figures 5, 12). During the southwest monsoon, 

 plumata appeared in large numbers off the 

 Somali coast and near the Seychelles whereas 

 morii was much more frequent in the eastern 

 Arabian Sea and the eastern Bay of Bengal. 

 In the northeast monsoon both species were 

 abundant in the Somali Current. However, only 

 morii appeared to be common in and about the 

 Andaman Sea whereas an indication of large 

 numbers of plumata appeared just south of 

 Java. 



Morphological relationships analyzed above 

 indicate the species have common ancestry that 

 produced three main lines of descent represented 

 respectively by plumata, platychela, and the 

 Indian-Pacific tropical pair of siblings, morii 

 and sobrina. Ample evidence of co-occurrence 



tvy 



plumata 



[\] SOUTHWEST MONSOON 

 ^ NORTHEAST MONSOON 



[V 



^1 



Figure 39. — Frequency of occurrence of Pontellina 

 plumata and P. morii in the Indian Ocean north of selected 

 latitudes compared to that south of the same latitudes. 



115 



