Trophic Basis of Production in a Neotropical Headwater Stream

Trophic basis of production analyses link consumers to energy flow and can thus provide insight into the consequences of declining animal diversity in streams. We examined gut contents of 18 dominant macroinvertebrate taxa, representing all functional feeding groups (FFG), from a Panamanian headwater stream before a massive amphibian decline occurred. We used secondary production estimates and assimilation and net production efficiencies, along with gut content data to quantify energy flow pathways. Overall consumption of allochthonous materials was greater than autochthonous materials in both the dry and wet seasons (p<0.001). Total consumption rates varied within and among shredders (0.85 – 12.10 g/m 2 /yr), scrapers (0.46 – 0.91 g/m 2 /yr), filterers (1.20 – 4.67 g/m 2 /yr), gatherers (0.43 – 2.44 g/m 2 /yr) and predators (0.05 – 0.95 g/m 2 /yr).  Anchytarsus , a shredder, had the highest consumption rate, while the predatory stonefly,  Anacroneuria , had the lowest. Omnivory was prevalent across all FFGs, but more pronounced in predators, especially  Anacroneuria  (55% animal; 45% plant). Early instar predators were more omnivorous than larger individuals. Further  post - amphibian decline studies will reveal how the sudden loss of consumer diversity alters energy flow in headwater streams.