Anthropogenic disturbance is restructuring ecosystems and changing interactions within ecological communities.
On the Hawaiʼian Islands, habitat degradation is linked to the establishment of invasive species; and together these
stressors may lead to declining native populations and changes in food webs. In this study we employed stable isotopes
to examine the structure of multiple Hawaiʼian stream food webs with varying levels of these stressors to illustrate
interactions between native and non-native organisms that may represent drivers of community change. Limahuli stream
contains all five species of native Hawaiʼian gobies, has a small number of introduced species, and minimal human
disturbance. ʻOpaekaʼa, Hul¯eʼia and Kapaʼa streams are more heavily invaded than Limahuli and have greater human
influence. We found increased species richness, increased trophic diversity, and increased total niche area in the more
heavily invaded stream food webs relative to Limahuli. We also found non-native predatory species inhabiting top trophic
positions in the three more heavily invaded streams and isotope mixing model estimates suggest that several species
of non-natives have overlapping prey sources with native gobies in these sites. Lastly, we found that native stream
organisms were nearly absent in ʻOpaekaʼa stream which also had the highest percent urban development of the streams
sampled. Our results suggest significant trophic changes have occurred as the result of introduced species and possibly
related to increased human disturbance.
Flow intermittency influences the trophic base, but not the overall diversity of alpine stream food webs
