Secondary Production in Four Panamanian Highland Streams: Assessing Macroinvertebrate Responses to Catastrophic Amphibian Declines

As part of the Tropical Amphibian Declines in Streams (TADS) project, we quantified macroinvertebrate production and community structure for 1 year in four streams in two upland regions of Panama, one that experienced massive amphibian declines and one with healthy amphibian assemblages.  Total habitat-weighted macroinvertebrate production was similar across all streams, ranging from 2.3 to 3.3 g ash-free dry mass (AFDM) m-2 y-1, and annual production/biomass ratios ranged from 9-12.  Total production was low compared to estimates from subtropical and temperate streams, but much higher than an estimate from a lowland stream in Costa Rica.  Functional feeding group production varied across sites, with filterers and shredders dominating pre-decline sites (27-32% of total) and predators and filterers dominating post-decline sites (35-48%). The shredding coleopteran Anchytarsus (0.5-0.9 gAFDM m-2 y-1) had the highest production in pre-decline sites, whereas Leptonema, a filter-feeder, was most productive in post-decline sites (0.3-1.1 gAFDM m-2 y-1).  Grazer production, which we hypothesized would be most influenced by the loss of grazing tadpoles, was similar among sites. However, community composition varied between pre- and post-decline streams, with Psephenus beetles as one of the dominant grazers at pre-decline streams, while mayflies and lepidopterans dominated post-decline streams.