FLEMINGER and HULSEMANN: FOUR SIBLING SPECIES OF PONTELLINA 



Table 12. — Comparison by rank test (Tate and Clelland, 1957:89) of the ratio exopod length to endopod length in the 



fifth legs of adult females. 



Samples tested 



Median 



Range 



N 



robs. 



856.5 



373 



967.5 



1655.5 



1911.5 



3.58 



0.38 



2.85 



0.14 



5.58 



<0.01 



0.7 



<0.01 



0.88 



<0.001 



sympatry have been discussed in recent studies 

 on the calanoid genera Lahidocera and Clauso- 

 calanus (Fleminger, 1967b, in press; Frost and 

 Fleminger, 1968). The similarity of the plumata 

 case to the character displacement found in 

 North American chorus frogs (Pseudacris). 

 reviewed by Littlejohn (1969, Figure 3), is 

 especially noteworthy. Differing only in geo- 

 graphical scale, both cases support the view of 

 a growing number of workers that premating 

 isolating mechanisms tend to be a product of 

 sympatry resulting from expansion of the 

 range of daughter populations that have diverg- 

 ed in geographical isolation (Alexander, 1969). 



REMARKS ON HABITAT 

 BIOGEOGRAPHY 



Vertical Distribution 



Essentially similar results from a number of 

 independent sets of published observations de- 

 lineate general features of the vertical distribu- 

 tion of P<>)itelUiia. The genus has been found 

 commonly between the surface and 200 m. Un- 

 fortunately differences between the congeners 

 were not noticed, and all specimens were re- 

 garded as representing a single species. Though 

 individuals may on occasion appear below 200 

 m, the largest numbers have been taken regular- 

 ly between the surface and 100 m (Vinogradov, 

 1968). Diurnal migrations seem to be neither 

 consistent nor extensive in vertical distance 

 (Wilson, 1942; Heinrich, 1961; Vinogradov 



and Voronina, 1964; Roehr and Moore, 1965). 

 Vinogradov and Voronina's report of a pattern 

 of latitudinal variation in the depth range of 

 Pontellina is particularly interesting in the 

 light of differences in the latitudinal distribu- 

 tion of plumata and the equatorial species. In 

 central waters the daytime 80% level (i.e.. the 

 depth above which 80% of the population occurs) 

 was found at 200 m, and the highest concentra- 

 tions appeared between 50 and 100 m. In 

 equatorial waters of the eastern Pacific the 

 daytime 80% level was found between 100 and 

 150 m, and the highest concentrations varied 

 between the to 25 m and the 25 to 50 m sam- 

 pling sti'ata. 



Wilson's (1942) records of Pontellina during 

 Cruise VII of the CaDiegie were based on sam- 

 ples collected with open nets routinely deployed 

 at 0830 h local time at three depths (0, 50, and 

 100 m) and towed horizontally. As in Vinogradov 

 and Voronina's (1964) results, Wilson's data 

 also show variation in frequency of captures 

 and aoundance at the three depths relative to 

 the geographical origin of the samples (Table 13). 



Vinogradov and Voronina (1963) and Voro- 

 nina (1964) found the largest number of Pontel- 

 li)ia in equatorial surface waters of the eastern 

 Pacific Ocean. They noted that the genus tends 

 to concentrate in upwelling regions along zones 

 of divergence and in the vicinity of the tropical 

 convergence. 



Previous observations that the genus Pontel- 

 lina occurs chieflv above 100 m in the more 



105 



