The eastern continental divide that bisects Georgia runs through Gwinnett County, separating headwater streams of the western Chattahoochee River watershed from headwater streams of the eastern Ocmulgee and Oconee River watersheds. This landscape feature was used to test hypotheses regarding headwater habitat, fish diversity and gene flow. Headwater habitats are dominant components of river network ecosystems delivering vital ecosystem services and biodiversity. Three headwater streams, one in the Chattahoochee watershed and two in the Oconee watershed, on Gwinnett County Park property, were sampled for differences in physical and chemical properties and fish inter- and intraspecific diversity. Our results suggest the headwater habitats are each distinguished by unique physical and temporal features. Initial hypotheses regarding expectations of fish diversity based on habitat type were not supported. However, hypotheses regarding the impact of gene flow on genetic diversity among headwater stream species were supported. Gene flow estimates and phylogenetic analyses among three well-sampled species observed in these headwater streams, Semotilus atromaculatus, Notropis lutipinnis, and Nocomis leptocephalus, suggest the Eastern Continental Divide acts as a barrier for gene flow for some species. Our findings highlight a proposed methodology for headwater stream analysis that combines habitat heterogeneity with community and species-level measures of diversity.


We would like to thank the students of Georgia Gwinnett College Ecology (BIOL 3500K) classes of 2021 for assistance in data collection.