Benthic Macroinvertebrates Cane Creek NC 65 



wide range (14-21), but was always high. Even stressed areas may have a 

 diverse chironomid fauna (Penrose et al. 1980) although tolerant species 

 will become dominant. The "other" category includes miscellaneous 

 Insecta (Neuroptera, Lepidoptera), Turbellaria, Hirudinea, Nemertea, 

 Porifera, and Nematoda. Variation in this category is very unpredictable. 



Table 4 presents average taxa richness values for streams in three 

 broad geographic areas in North Carolin: Mountains (data expanded 

 from Penrose et al. 1982); Piedmont (as in Table 5); and Coastal Plain. 

 These three physiographic regions have differing physical characteris- 

 tics. Going from the mountains to the coast one would expect increasing 

 water temperature, lower gradient, and increasing amonts of sand and 

 silt. The Coastal Plain data set is based on collections in Craven, Hert- 

 ford, and Northampton counties. These coastal streams are not entirely 

 unstressed, but the data are adequate to illustrate geographic trends. 



The overall trend suggests a relatively constant number of species 

 in stream environments. Average taxa richness for Coastal Plain and 

 Mountain streams is well within the range expected for Piedmont 

 streams (Table 3). From this pattern one might advance the hypothesis 

 that unpolluted streams have a relatively constant number of niches. 

 Furthermore, these data imply that taxa richness is an excellent moni- 

 toring tool across a wide range of stream types. A similar hypothesis 

 was advanced by Patrick (1975:448). She examined species richness in 

 nine different rivers and concluded that "similar-sized areas of different 

 streams support similar numbers of species." This constancy of "a - 

 diversity" prevailed even when the number of species shared between 

 streams was low. 



Table 4. Average taxa richness by group for Coastal Plain, Piedmont and 

 Mountain streams in North Carolina. See text for data sources. 

 Number of streams shown in parentheses. 



Group 



Coastal Plain (7) 



Piedmont (6) 



Mountains (9) 



EPHEMEROPTERA 



2.9 



8.5 



9.7 



PLECOPTERA 



0.8 



3.2 



6.5 



ODONATA 



2.5 



1.4 



0.8 



TRICHOPTERA 



3.9 



4.6 



7.8 



COLEOPTERA 



2.8 



4.6 



2.5 



MEGALOPTERA 



0.7 



1.8 



0.2 



DIPTERA 



23.0 



17.1 



14.5 



MOLLUSCA 



3.7 



2,1 



0.5 



OLIGOCHAETA 



3.6 



2.2 



0.9 



CRUSTACEA 



2.5 



2.1 



0.9 



OTHER 



2.0 



0.9 



0.2 



TOTALS 



48.4 



48.9 



44.5 



