|Lead PI||Matt Whiles (Southern Illinois University)|
|Co-PIs||Catherine Pringle (UGA), Susan Kilham (Drexel University), Karen Lips (University of Maryland)|
|Graduate Students (Drexel U)||Meshagae Hunte-Brown (PhD)|
|Graduate Students (So. Illinois U)||Checo Colon-Gaud (PhD), Therese Frauendorf (MS), Amanda Rugenski (PhD)|
|Graduate Students (UGA)||Tom Barnum (PhD), Scott Connelly (PhD)|
|Post-Doctoral Fellow (UGA)||Piet Verburg|
What are the short- and long-term consequences of extinction?
Quantifying the ecological effects of catastrophic amphibian declines in Neotropical streamsThe TADS (Tropical Amphibian Declines) Project is a long-term collaborative project (funded by the NSF for 13 yrs) that is examining both the short- and long-term consequences of the disease-driven extinction of an entire species assemblage of stream-dwelling frogs in Panama. Quantifying and predicting the ecological consequences of declining biodiversity is an urgent challenge, particularly in freshwater ecosystems where species declines and losses are among the highest. Over the past 13 years, we have focused on quantifying the ecological effects of the loss of stream-dwelling frogs from a fungal (Batrachochytrium dendrobatidis) disease in highland streams of Panama that has moved through Central America in a unidirectional wave from west to east (See Figs. 1,2). By working on both sides of this disease front we were able to obtain pre- and post extirpation data on stream ecosystem structure and function, allowing for comprehensive pre- and post-decline comparisons in the same streams. Prior to their decline, larval frogs (tadpoles) were the most abundant and diverse group of stream vertebrates in many highland streams of Central America: our focal study streams in Panama contained 21 stream-dwelling species and densities often greater than 50 individuals m-2.
Project History The TADS Project began in 2000 with funding from an NSF SGER Grant (Evaluating the role of stream-dwelling frogs in tropical foodwebs; Pringle, Lips and Kilham; 2000-01) and was followed by two NSF Collaborative Ecosystem Grants that extended to 2013: (1) Response of tropical stream ecosystem structure and function to amphibian extinctions (2003-06); and (2) Ecosystem- level consequences of extinction: quantifying the ecological effects of catastrophic amphibian declines in neotropical streams Whiles, Lips, Pringle and Kilham, 2008-13). While NSF funding from our last collaborative grant ended in 2013, we are continuing post-decline sampling and analyses in order to take advantage of the unprecedented opportunity to measure long-term changes associated with the loss of an entire group of consumers using pre- and post-extirpation datasets from our focal study streams in El Cope and El Valle, Panama. Our project has shown that extinction is a much larger issue than species loss, with cascading ecosystem-level consequences. Research findings have established the key role that larval frogs played in stream ecosystem function before they were extirpated. Larval tadpoles controlled the amount of basal resources in the stream food web, significantly decreasing algal standing crop and accrual rates and enhancing rates of leaf decomposition. Following their extirpation, the biomass of algal primary producers increased by over two fold, with greater than 50% reduction in rates of nitrogen uptake. Post-extirpation studies (over three years) showed that changes in rates of ecosystem processes (resulting from loss of the frog assemblage) were not compensated for by other functionally redundant consumer organisms (e.g., aquatic insects). Our findings do not support the assumption that tropical ecosystems with high biodiversity are more resilient to extinction events because of the greater potential for ecological redundancy. Instead, we found that ecosystem-level consequences of declining biodiversity were not offset by ecological redundancy, at least in the short-term (over three years). By quantifying ecosystem-level consequences of the loss of biodiversity at relevant spatial and temporal scales, we are addressing one of the grand challenges and focal areas of ecological research designated by the National Academy of Sciences’ National Research Council. Moreover, our project is providing an unparalleled long-term data set (2000-present) on ecosystem structure and function before and after an extinction event. Consequently, our data set provides an invaluable foundation for future quantification of long-term effects of an extinction event.