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.

There is growing recognition that ecosystems may be more impacted by infrequent extreme climatic events than by changes in mean climatic conditions. This has led to calls for experiments that explore the sensitivity of ecosystems over broad ranges of climatic parameter space. However, because such response surface experiments have so far been limited in geographic and biological scope, it is not clear if differences between studies reflect geographic location or the ecosystem component considered. In this study, we manipulated rainfall entering tank bromeliads in seven sites across the Neotropics, and characterized the response of the aquatic ecosystem in terms of invertebrate functional composition, biological stocks (total invertebrate biomass, bacterial density) and ecosystem fluxes (decomposition, carbon, nitrogen). Of these response types, invertebrate functional composition was the most sensitive, even though, in some sites, the species pool had a high proportion of drought‐tolerant families. Total invertebrate biomass was universally insensitive to rainfall change because of statistical averaging of divergent responses between functional groups. The response of invertebrate functional composition to rain differed between geographical locations because (1) the effect of rainfall on bromeliad hydrology differed between sites, and invertebrates directly experience hydrology not rainfall and (2) the taxonomic composition of some functional groups differed between sites, and families differed in their response to bromeliad hydrology. These findings suggest that it will be difficult to establish thresholds of “safe ecosystem functioning” when ecosystem components differ in their sensitivity to climatic variables, and such thresholds may not be broadly applicable over geographic space. In particular, ecological forecast horizons for climate change may be spatially restricted in systems where habitat properties mediate climatic impacts, and those, like the tropics, with high spatial turnover in species composition.

The Neotropics are a hotspot of global diversity for many groups of organisms, including the dragonflies and damselflies (Insecta: Odonata). While the number of biodiversity surveys and new species descriptions for Neotropical odonates is increasing, diversity in this region is still under-explored, and very few studies have looked at the genetic and morphological diversity among (and within) species. Here, we present an overview of the evolutionary history of the Neotropical damselfly family Polythoridae. The family comprises 57 species across seven genera: Chalcopteryx Selys, Chalcothore De Marmels, Cora Selys, Euthore Selys, Miocora Calvert, Polythore Calvert and Stenocora Kennedy. Using a multi-locus approach, mitochondrial (COI, ND1, 16S) and nuclear (18S, 28S, EF1-alpha) genes were concatenated to estimate phylogenetic relationships. Our results support five monophyletic clades, which were not always congruent with the genera previously considered to be monophyletic. Only Polythore was recovered as monophyletic, and within it there was geographical structure. We propose the following new genus-level classification: Chalcothore, Chalcopteryx, Cora s.s., Cora s.l., Miocora, Euthore s.l and Polythore. In addition, we proposed the following new combinations: Miocora aurea comb.n., Miocora chirripa comb.n., Euthore confusa comb.n., Euthore klenei comb.n., and Euthore terminalis comb.n., based on our phylogenetic analyses, our evaluation of morphological characters and their geographical distribution: these data each support the monophyletic entities we recover here. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid: zoobank.org:pub:E9E10CD8-6A04-4F2E-A632-1B998BAFB193.

The study of diversity gradients is a frequent approach to understand evolutionary processes that structure communities. Altitudinal gradients allow the analysis of community spatial responses to environmental fluctuations. One interesting place to study altitudinal gradients is the Andes system because of the coexistence of isolated and continuous mountain ranges. We investigated the altitudinal turnover of species in peripheral mountainous systems by analyzing the structure of dung beetle assemblages along a complete gradient in the Sierra Nevada de Santa Marta, Colombia. Seven sites ranging from 480 to 2,890 m were evaluated, using linear transects of pitfall traps. A total of 2,992 individuals and 46 species were collected. Abundance, richness, and diversity diminished with altitude, revealing significant differences among sites. Some genera appeared at certain altitudes and most species appeared at unique sites, indicating a marked altitudinal turnover. A similarity analysis demonstrated the existence of separate lowland and high mountain groups with a turnover at 1,200-1,600 m asl. We registered for the first time a species replacement between Scarabaeinae (low-lands) and Aphodiinae (high-lands) in the Neotropical region. Our results largely agree with the species pattern described for Mesoamerica, although, in this case the altitudinal turnover is more evident, unveiling a transition zone between lowland and high mountain fauna elements. This result suggests an equilibrium between a weak horizontal colonization and a strong vertical turnover, that appears to be higher in isolated mountains. Future investigations with other insect groups are necessary to corroborate this altitudinal pattern in isolated mountains.

Batesian mimics can parasitize Müllerian mimicry rings mimicking the warning color signal. The evolutionary success of Batesian mimics can increase adding complexity to the signal by behavioral and locomotor mimicry. We investigated three fundamental morphological and locomotor traits in a Neotropical mimicry ring based on Ithomiini butterflies and parasitized by Polythoridae damselflies: wing color, wing shape, and flight style. The study species have wings with a subapical white patch, considered the aposematic signal, and a more apical black patch. The main predators are VS-birds, visually more sensitive to violet than to ultraviolet wavelengths (UVS-birds). The white patches, compared to the black patches, were closer in the bird color space, with higher overlap for VS-birds than for UVS-birds. Using a discriminability index for bird vision, the white patches were more similar between the mimics and the model than the black patches. The wing shape of the mimics was closer to the model in the morphospace, compared to other outgroup damselflies. The wing-beat frequency was similar among mimics and the model, and different from another outgroup damselfly. Multitrait aposematic signals involving morphology and locomotion may favor the evolution of mimicry rings and the success of Batesian mimics by improving signal effectiveness toward predators.