PS 37-17 - Morphological and dietary shift following arrival of new species

Abstract: Long term historical sampling available through natural history collections offer unique opportunities to observe changes in faunal composition and examine changes in diet as the fauna changes through time. Catatonk Creek in the upper Susquehanna River drainage has been sampled continuously by the Cornell University Museum of Vertebrates for nearly a century and in that time the darter (fishes in the family Percidae) species assemblage has grown from two species to four due to the recent introduction of two additional species (Etheostoma zonale in 1980 and E. blennioides in 2000). We examined the oral physiology and nitrogen stable isotope ratio of E. olmstedi, an original species, compared to the two invaders and found that mouth morphologies changed in both E. olmstedi and E. zonale. In addition, the nitrogen stable isotope ratios enriched in the invader compared to the original species by 2.6 per mil. These results together suggest that when the two species came together in Catatonk Creek, the invasive species moved up in trophic position and the resident species moved down. This temporal examination of morphology and stable isotopes shows a definitive shift in diet for the darters pre and post colonization in this time series.