The evolutionary assembly of forest communities along environmental gradients: recent diversification or sorting of pre-adapted clades?

Recent studies have demonstrated that ecological processes that shape community structure and dynamics change along environmental gradients. However, much less is known about how the emergence of the gradients themselves shape the evolution of species that underlie community assembly. In this study, we address how the creation of novel environments leads to community assembly via two nonmutually exclusive processes: immigration and ecological sorting of pre-adapted clades (ISPC), and recent adaptive diversification (RAD). We study these processes in the context of the elevational gradient created by the uplift of the Central Andes. We develop a novel approach and method based on the decomposition of species turnover into within- and among-clade components, where clades correspond to lineages that originated before mountain uplift. Effects of ISPC and RAD can be inferred from how components of turnover change with elevation. We test our approach using data from over 500 Andean forest plots. We found that species turnover between communities at different elevations is dominated by the replacement of clades that originated before the uplift of the Central Andes. Our results suggest that immigration and sorting of clades pre-adapted to montane habitats is the primary mechanism shaping tree communities across elevations.

Pollen limitation in a narrow endemic plant: geographical variation and driving factors.

Pollen limitation may have important consequences for the reproduction and abundance of plant species. It may be especially harmful to endangered and endemic plants with small populations. In this study, we quantify the effect of pollen limitation on seed production and seedling emergence in an endangered narrow endemic crucifer, Erysimum popovii. We conducted a pollen addition experiment across the entire geographic distribution of the species, and explored the effect of pollinator assemblage, plant population size and density, and other habitat variables on pollen limitation intensity in 13 populations. We supplemented flowers in 20 plants per population with allogamous pollen. To account for potential resource reallocation, we used two types of control untreated flowers: internal control flowers from the same individual as the supplemented flowers, and external control flowers from other individuals. Our results indicate that E. popovii is pollen-limited in most of the populations studied, but only through seed production, since pollen supplementation did not enhance seedling emergence. Beefly abundance was associated with among-population differences in pollen limitation intensity. Populations in which beeflies were more abundant were less pollen-limited. In contrast, the abundance of other flower visitors, such as large bees or butterflies, was not associated with pollen limitation. Annual rainfall and bare soil cover were associated with the intensity of pollen limitation across populations.

First reports of envenoming by South American water snakes Helicops angulatus and Hydrops triangularis from Bolivian Amazon: A one-year prospective study of non-front-fanged colubroid snakebites.

Although snakebite incidence is underestimated in Bolivia, the Amazon region presents the highest incidence of these accidents. The local effects of bites by some non-front-fanged colubroid (NFFC) snakes are usually confused with that of viperids, resulting in the improper use of antivenoms and medications. Since there is scarce information on clinical treatment and management of NFFC bites from Bolivian Amazon, we conducted a prospective study of NFFC snakebites by reviewing the records of patients admitted with a snakebite diagnosis at Hospital Central Ivirgarzama, Bolivia. Snakebites were recorded for 12 months (December 2019-November 2020), including information about the sex and age of the patient, snakebite date, and treatment. Eight (5.7 %) of 152 patients were bitten by NFFC Helicops angulatus, Hydrops triangularis, and Erythrolamprus sp. Our results showed that 5/7 patients had prolonged clotting time and INR, as well as local edema and mild pain, suggesting systemic envenoming. Previously non-documented mild coagulopathy was observed for H. angulatus and H. triangularis bites. In some cases, incorrect first-aid measures, and inappropriate use of bothropic/lachesic antivenom were administrated. All the patients received supportive therapy and antihistamine drugs. Unsupported use of non-evidence-based treatments for snakebites such as corticoids, non-steroidal anti-inflammatory drugs (NSAIDs), and prophylactic antibiotic prescription were recorded. In conclusion, we describe the first formally documented snakebite cases produced by NFFC from Bolivia, highlighting the urgent need for training of the medical team in the snake identification, clinical management of snakebite, and the existence of a human-snake conflict involving NFFC species.

A novel approach to assessing environmental disturbance based on habitat selection by zebra fish as a model organism.

Aquatic ecotoxicity assays used to assess ecological risk assume that organisms living in a contaminated habitat are forcedly exposed to the contamination. This assumption neglects the ability of organisms to detect and avoid contamination by moving towards less disturbed habitats, as long as connectivity exists. In fluvial systems, many environmental parameters vary spatially and thus condition organisms' habitat selection. We assessed the preference of zebra fish (Danio rerio) when exposed to water samples from two western Ecuadorian rivers with apparently distinct disturbance levels: Pescadillo River (highly disturbed) and Oro River (moderately disturbed). Using a non-forced exposure system in which water samples from each river were arranged according to their spatial sequence in the field and connected to allow individuals to move freely among samples, we assayed habitat selection by D. rerio to assess environmental disturbance in the two rivers. Fish exposed to Pescadillo River samples preferred downstream samples near the confluence zone with the Oro River. Fish exposed to Oro River samples preferred upstream waters. When exposed to samples from both rivers simultaneously, fish exhibited the same pattern of habitat selection by preferring the Oro River samples. Given that the rivers are connected, preference for the Oro River enabled us to predict a depression in fish populations in the Pescadillo River. Although these findings indicate higher disturbance levels in the Pescadillo River, none of the physical-chemical variables measured was significantly correlated with the preference pattern towards the Oro River. Non-linear spatial patterns of habitat preference suggest that other environmental parameters like urban or agricultural contaminants play an important role in the model organism's habitat selection in these rivers. The non-forced exposure system represents a habitat selection-based approach that can serve as a valuable tool to unravel the factors that dictate organisms' spatial distribution in connected ecosystems.