DOI: 10.5061/dryad.ns1rn8pv8
title: Warming and top predator loss drive direct and indirect effects on multiple trophic groups within and across ecosystems

description: 1. The interspecific interactions within and between adjacent ecosystems
 strongly depend on the changes in their abiotic and biotic components.
 However, little is known about how climate change and biodiversity loss in
 a specific ecosystem can impact the multiple trophic interactions of
 different biological groups within and across ecosystems. 2. We used
 natural micro-ecosystems (tank-bromeliads) as a model system to
 investigate the main and interactive effects of aquatic warming and
 aquatic top predator loss (i.e., trophic downgrading) on trophic
 relationships in three integrated food web compartments: i) aquatic
 microorganisms, ii) aquatic macroorganisms, and iii) terrestrial predators
 (i.e., via cross ecosystem effects). 3. The aquatic top predator loss
 substantially impacted the three food web compartments. In the aquatic
 macrofauna compartment, trophic downgrading increased the filter-feeder
 richness and abundance directly and indirectly via an increase of
 detritivore richness, likely through a facilitative interaction. For the
 microbiota compartment, aquatic top predator loss had a negative effect on
 algae richness, probably via decreasing the input of nutrients from
 predator biological activities. Furthermore, the more active terrestrial
 predators responded more to aquatic top predator loss, via an increase of
 some components of aquatic macrofauna, than more stationary terrestrial
 predators. The aquatic trophic downgrading indirectly altered the richness
 and abundance of cursorial terrestrial predators, but these effects had
 different direction according to the aquatic functional group,
 filter-feeder or other detritivores. The web-building predators were
 indirectly affected by aquatic trophic downgrading due to increased
 filter-feeder richness. Aquatic warming did not affect the aquatic micro-
 or macro-organisms but did positively affect the abundance of web-building
 terrestrial predators. 4. These results allow us to raise a predictive
 framework of how different anthropogenic changes predicted for the next
 decades, such as aquatic warming and top predator loss, could
 differentially affect multiple biological groups through interactions
 within and across ecosystems.
description: We conducted the study at the Serra do Mar State Park, Nucleo
 Picinguaba, on the northern coast of the state of São Paulo, Brazil, from
 April to July 2014. The bromeliad species <i>Neoregelia
 johannis</i> (Carriere) LB Smith. (Bromeliaceae) were employed as a
 model system in the experiment. Our study investigated how aquatic warming
 and the loss of top aquatic predators affect the food web structure of
 aquatic macrofauna and microfauna, as well as multiple groups of
 terrestrial predators. Temperature manipulations here predicted warming
 for the next decades in the study site, i.e., an average projected for
 2040 (2°C above ambient), and 2100 (4°C above ambient). To sample the
 aquatic microbiota organisms, we homogenized the bromeliad water,
 collected 2 ml, and fixed it with 5% Lugol for counting and identifying
 microscopic algae, protozoa, and metazoa (hereafter referred to as
 microbiota). To sample macrofauna organisms at the end of the experiment,
 we first sampled the terrestrial organisms foraging upon the experimental
 tank-bromeliads (e.g., spiders, centipeds, ants). After that, we dissected
 and washed the bromeliads. Then, we separated terrestrial and aquatic
 organisms found in the trays, counted, fixed, and later identified the
 organisms to the lowest possible taxonomic level and functional group
 (Antiqueira et al., 2018a). The details of the sampling and
 characterization of macrofauna and microfauna are described in Appendix 1
 of the paper. The consumer-resource relationships between all the
 macrofauna and microbiota were determined according to specific literature
 and field observation.
description: ID = experimental unity identification block = block identification pred = predator treatment (1spp, 4spp, no=absence) temp = warming treatment (amb=ambient; Two = +2ºC; Four= +4ºC) media.t = average temperature of each experimental bromeliad pred.1 = predator treatment (Presence/Absence) filt.feed.abund = filter-feeder abundance filt.feed.riq = filter-feeder richness mesopred.riq = aquatic mesopredator richness mesopred.abund = aquatic mesopredator abundance detritivore.abund = detritivore abundance detririvore.riq = detritivore richness curs.pred.t.rich = cursorial terrestrial predator richness curs.pred.t.abd = cursorial terrestrial predator abundance web.pred.rich = web-building predator richness web.pred.abd = web-building predator abundance mesopred.t.ric = terrestrial mesopredator richness mesopred.t.ab = terrestrial mesopredator abundance ciliate.abund = ciliates abundance ciliate.richness = ciliates richness ameb.abund = testate amoebae abundance ameb.richness = testate amoebae richness zoop.abundance = zooplankton abundance zoop.richness = zooplankton richness flage.abund = flagellates abundance flage.richness = flagellates richness phyto.rich = algae richness phyto.abund = algae abundance