Extreme rainfall events alter the trophic structure in bromeliad tanks across the Neotropics

Abstract

Changes in global and regional precipitation regimes are among the most pervasive components of climate change. Intensification of rainfall cycles, ranging from frequent downpours to severe droughts, could cause widespread, but largely unknown, alterations to trophic structure and ecosystem function. We conducted multi-site coordinated experiments to show how variation in the quantity and evenness of rainfall modulates trophic structure in 210 natural freshwater microcosms (tank bromeliads) across Central and South America (18°N to 29°S). The biomass of smaller organisms (detritivores) was higher under more stable hydrological conditions. Conversely, the biomass of predators was highest when rainfall was uneven, resulting in top-heavy biomass pyramids. These results illustrate how extremes of precipitation, resulting in localized droughts or flooding, can erode the base of freshwater food webs, with negative implications for the stability of trophic dynamics.

Climate influences the response of community functional traits to local conditions in bromeliad invertebrate communities

“…The amount of water found in a bromeliad at the time of sampling is related to the amount of habitat available to invertebrates, the risk of drought, and whether it is colonized by predators, and as such, habitat size is an important predictor of species richness, species composition and trophic structure (Srivastava et al 2008, Amundrud and Srivastava 2015, Petermann et al 2015). In an experiment where many of these factors were controlled for, local variation in rainfall impacted the community structure of bromeliad macroinvertebrates (Srivastava et al 2020b), and in extreme cases, caused an inversion of the trophic pyramid (Romero et al 2020). So a combination of local conditions will have some effect on community dynamics and the distribution of traits.…”

“…However, much of the geographic variation in invertebrate composition remains unexplained, and consequently begs for more explicit incorporation of broad‐scale variables like climate. For example, extreme rainfall events lead to an inversion of the trophic pyramid of macroinvertebrates in bromeliads across seven study sites broadly distributed across the neotropics (Romero et al 2020).…”

A proposal to advance theory and promote collaboration in tropical biology by supporting replications

“…Some of the most important advances in tropical biology have come from researchers forming networks to systematically collect observations of tree growth and diversity in permanent plots (Anderson-Teixeira et al, 2015;Menke et al, 2012;Poorter et al, 2016;Rovero & Ahumada, 2017). The same is likely to be true as tropical biologists embrace "distributed experiments" (Borer et al, 2014;Fraser et al, 2013), in which the same experimental manipulation is implemented at geographically and ecologically disparate locations (e.g., Romero et al, 2020). The Reproducibility Project in Tropical Biology (RP:TB) we envision complements these efforts with a new means by which researchers throughout the tropics can collaborate to test and advance theory.…”

High Temporal Beta Diversity in an Ant Metacommunity, With Increasing Temporal Functional Replacement Along the Elevational Gradient

“…Montane insect assemblages are thought to be very vulnerable to global warming (Laurance et al, 2011), because with increasing temperature, these organisms are expected to shift their elevational ranges, leading to mountaintop extinctions (Colwell et al, 2008). As there is growing evidence that climate change affects both temperature and precipitation regimes (e.g., Romero et al, 2020) and also the occurrence and intensity of extreme climatic events (e.g., Fischer and Knutti, 2015;Patricola and Wehner, 2018), we may expect that such increase in climatic variation and instability will drastically affect ant metacommunities. With this higher temporal variation in conditions and resources, we might lose the rarer and specialized species (Davies et al, 2004) that cannot survive the new environmental filter, leading to the homogenisation of the metacommunity (Newbold et al, 2019).…”