Assessing ecological responses to catastrophic amphibian declines: Patterns of macroinvertebrate production and food web structure in upland Panamanian streams

Abstract

As part of the Tropical Amphibian Declines in Streams (TADS) project, we estimated macroinvertebrate production and constructed quantitative food webs for four headwater stream reaches in the Panamanian uplands: two that had experienced massive amphibian declines and two with unaffected amphibian populations. As expected for forested headwaters, allochthonous materials were the dominant energy source. Total macroinvertebrate biomass and production ranged from 231 to 360 mg ash-free dry mass m 22 and from 3.1 to 4.4 g ash-free dry mass m 22 yr 21 , respectively, and did not appear influenced by the presence or absence of amphibians. However, macroinvertebrate functional structure differed between pre-and post-decline sites, with shredder production significantly higher in pre-decline sites and scrapers significantly higher in post-decline sites. Taxonomic differences between pre-and post-decline sites were also evident. There was a shift in scrapers from smaller-bodied taxa (e.g., Psephenus) in pre-decline sites to larger-bodied groups (e.g., Petrophila) in post-decline sites. Detrital pathways were dominant in these systems, with shredders and collectors accounting for most energy flow. However, scrapers were well-represented and they were food-limited in these systems, particularly in the presence of larval amphibians at pre-decline sites. Ecological effects of catastrophic amphibian declines ranged from subtle shifts in taxonomic composition and functional structure of remaining consumers to changes in the availability and relative importance of autochthonous energy sources.

Mapping the Global Emergence of Batrachochytrium dendrobatidis, the Amphibian Chytrid Fungus

“…Bd has an unusually wide host-range: it has been detected infecting hundreds of species. Cascading effects owing to declines of multiple host species as a result of chytridiomycosis could potentially undermine ecosystem stability and function [9], [10], although some studies have not supported key functional roles of amphibians in local ecosystems [11]. Hence, although caution is necessary because amphibians' ecological roles will vary with location, as a worst case scenario, the potential of Bd to act synergistically with other anthropogenic drivers may catastrophically disturb biological communities and substantially contribute to the ongoing 6 th mass extinction event [8].…”

Energy flow and the trophic basis of macroinvertebrate and amphibian production in a neotropical stream food web

“…the trophic basis of production), is lacking (but see Ramírez & Pringle, ; Cross et al ., ; Colón‐Gaud et al ., ). Flooding during the tropical wet season reduces detrital resources and algal standing stocks in stream channels (Dudgeon, ; Yang, Tang & Dudgeon, ), which may limit secondary production (Colón‐Gaud et al ., ) and influence the type of resources consumed. In contrast, relatively stable conditions during the dry season favour development of algal communities and animal populations (Dudgeon, ; Yang et al ., ).…”

Emerging fungal threats to animal, plant and ecosystem health

“…17). As a consequence of the infection, some areas of central America have lost over 40% of their amphibian species 18 , a loss that has resulted in measurable ecosystem-level changes 19 . This spatiotemporal pattern has been broadly mirrored in other continents 15 , and ongoing reductions in amphibian diversity owing to chytridiomycosis have contributed to nearly half of all amphibian species being in decline worldwide 20 .…”