||May RM. How Many Species Are There on Earth? Science. 1988 Sep 16241(4872):1441-1449PubMed ID17790039
||J. E. Cohen, C. M. Newman, F. E. Briand, Proc. R. Soc. London Ser. B 224, 449 (1985).
||Cohen and Briand (1, 2) have compiled and analyzed a catalog that now includes 113 food webs, embracing a wide variety of natural environments (55 food webs from continental settings-23 terrestrial and 32 aquatic-along with 45 coastal and 13 oceanic webs).
||The average number of other species with which any one species interacts directly is consistently around 3 to 5. The number is consistently higher (average, 4.6) in relatively constant environments than in fluctuating ones (average, 3.2)