Environmental heterogeneity at two spatial scales affects litter diversity-decomposition relationships.

The effects of biodiversity on ecological processes have been experimentally evaluated mainly at the local scale under homogeneous conditions. To scale up experimentally based biodiversity-functioning relationships, there is an urgent need to understand how such relationships are affected by the environmental heterogeneity that characterizes larger spatial scales. Here, we tested the effects of an 800-m elevation gradient (a large-scale environmental factor) and forest habitat (a fine-scale factor) on litter diversity-decomposition relationships. To better understand local and landscape scale mechanisms, we partitioned net biodiversity effects into complementarity, selection, and insurance effects as applicable at each scale. We assembled different litter mixtures in aquatic microcosms that simulated natural tree holes, replicating mixtures across blocks nested within forest habitats (edge, interior) and elevations (low, mid, high). We found that net biodiversity and complementarity effects increased over the elevation gradient, with their strength modified by forest habitat and the identity of litter in mixtures. Complementarity effects at local and landscape scales were greatest for combinations of nutrient-rich and nutrient-poor litters, consistent with nutrient transfer mechanisms. By contrast, selection effects were consistently weak and negative at both scales. Selection effects at the landscape level were due mainly to nonrandom overyielding rather than spatial insurance effects. Our findings demonstrate that the mechanisms by which litter diversity affects decomposition are sensitive to environmental heterogeneity at multiple scales. This has implications for the scaling of biodiversity-ecosystem function relationships and suggests that future shifts in environmental conditions due to climate change or land use may impact the functioning of aquatic ecosystems.

Seasonal variation of the biomass of a dung beetle assemblage (Coleoptera: Scarabaeinae) in a high andean grassland / Variación estacional de la biomasa de un ensamble de escarabajos coprófagos (coleoptera: scarabaeinae) en un pastizal altoandino

RESUMEN Los escarabajos coprófagos son excelentes indicadores de la integridad ecológica de los ecosistemas, cumpliendo un rol funcional esencial en el reciclaje de nutrientes, fertilización y aireación del suelo. Sin embargo, se conoce muy poco acerca de los ensambles de escarabajos altoandinos y de su estacionalidad. Por lo anterior, se buscó entender la variación estacional de la estructura del ensamble y su efecto en la biomasa, se escogieron dos pastizales, en la Reserva Biológica Encenillo (Guasca-Cundinamarca). En cada uno se dispusieron diez trampas de caída distanciadas 50 m y cebadas con excremento durante 24 horas. Se realizaron tres réplicas en cada una de las tres épocas estudiadas (seca, transición y lluvias). Se registró una variación estacional significativa, demostrando que las especies están asociadas a la época de lluvias. Se encontraron diferencias significativas para la biomasa entre especies y por época. La especie con la mayor biomasa fue Homocopris achamas. Se evidencia que los ensambles de pastizales altoandinos son poco diversos, debido a la fuerte perturbación antrópica, las presiones asociadas con la altitud y a la misma dinámica evolutiva de estas regiones. La marcada estacionalidad de las especies registradas y la estrecha asociación con la época de lluvias concuerda con el patrón estacional que se registra en el Neotrópico. La fuerte variación estacional de la biomasa puede tener un fuerte impacto en la funcionalidad ecológica y los servicios ecosistémicos en este hábitat. Es necesario cuantificar a futuro el aporte funcional de las especies y su variación estacional, con miras a su conservación.

ABSTRACT Dung beetles are excellent indicators of ecosystem ecological integrity, accomplishing an essential role in nutrient cycling process that includes fertilization and soil aeration. Nevertheless, very little is known about the influence of season variation on the assemblage composition and ecological function of dung beetles from high Andean zones. We aimed to investigate the seasonal effect on the diversity and ecological function of dung beetles in terms of biomass. We sampled two pasture patches of the "Reserva Biológica Encenillo", located in Cundinamarca-Colombia, using ten pitfall traps baited with feces placed 50 m apart for 24 hours. This sample design was replicated during each season (dry, transition, and rain). A significant seasonal variation was documented, demonstrating an important association with the rainy season. Significant differences were found for the biomass between species and seasons. The species with the highest biomass was Homocopris achamas. It is evident that high Andean pastures assemblages have low diversity, due to the strong human disturbance, the pressures associated with the altitude, and the evolutionary dynamics of these regions. The marked seasonality of the registered species and the close association with the rainy season are consistent with the pattern established for the Neotropical region. Likewise, a strong seasonal variation of the biomass is evident, which could have a significant impact on the ecological functionality and the ecosystem services in this habitat. In future studies, it is necessary to quantify the functional contribution of the species and their seasonal variation to contribute to their conservation.

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

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.

Altitudinal Turnover of Species in a Neotropical Peripheral Mountain System: A Case Study With Dung Beetles (Coleoptera: Aphodiinae and Scarabaeinae).

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.

The larva and female of Perigomphus basicornis Amaya-Vallejo, Novelo-Gutiérrez & Realpe, 2017, and the first record of Perigomphus pallidistylus (Belle, 1972) for Colombia (Insecta: Odonata: Gomphidae).

The larva and female of Perigomphus basicornis are described and illustrated, and compared with the larva and female of P. pallidistylus. The larva of P. basicornis differs from that of P. pallidistylus in having sternum 8 divided in five sclerites, abdominal segments 8 and 9 with small, low protuberances on the tergites and male's epiproct as long as its basal width, mainly. The female of P. basicornis differs from that of P. pallidistylus in having the apical lobes of vulvar lamina wider, with divergent tips. P. pallidistylus is recorded for Colombia for the first time.

Toxicity evaluation and initial characterization of the venom of a Colombian Latrodectus sp.

The genus Latrodectus has not been studied in Colombia even though it is medically important worldwide; there are three species for the country, this study focused on a non-identified species found in the Tatacoa Desert in the Huila Department. This research is the first approximation to the extraction, composition analysis and toxicity evaluation of the venom of a species of the genus Latrodectus in Colombia; and aims to evaluate the toxicity by the initial characterization of its venom. The venom extraction was accomplished with electrostimulation and total protein concentration was determined by the Lowry method and BCA assays from crude venom; with these methods, high protein concentration of the samples was measured. Bioassays on mice were also made to evaluate the toxicity and compare the symptoms produced by this Colombian spider to the Latrodectism Syndrome. Finally, an SDS-PAGE electrophoresis was used to separate the main components of high molecular weight from the samples and compared to a control of the venom of Latrodectus mactans to determine if the venom composition is different between these two species.

Multitrait aposematic signal in Batesian mimicry.

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.

A neotropical polymorphic damselfly shows poor congruence between genetic and traditional morphological characters in Odonata.

The Neotropical damselfly genus Polythore consists of nineteen described morphospecies. We used the COI barcode locus (799 bp), male genitalia, wing venation, and geometrical pattern variation to clarify specific status in four Polythore procera populations in the Andean foothills of Colombia. Morphological data corroborates that all populations are P. procera, but molecular data suggests two well-supported reciprocal monophyletic clades. A high genetic divergence (∼ 3%) was observed between them, and different degrees of gene flow were estimated by MDIV among populations. Our results support a recent (1.4 mya) possible speciation with morphological stasis where unknown reproductive mechanisms may be involved.

Histological analyses of the fungal endophytes in Rosa hybrida.

Endophytes are fungi that cause asymptomatic infections in leaves and stems of healthy plants. This study evaluated the presence of endophytic fungi on leaves of Rosa hybrida collected in Bogota, (Colombia) using histological techniques and light microscopy. Histological preparations showed fungal mycelium with few cells in the vascular tissue. Colonization of mesophyll cells was not observed. Visualization of fungal cells within plant tissues is a confirmatory test of the endophytic habitat of fungi isolated from leaves of Rosa hybrida.