ABSTRACT
Termites perform key ecological functions in tropical ecosystems, are strongly affected by variation in rainfall, and respond negatively to habitat disturbance. However, it is not known how the projected increase in frequency and severity of droughts in tropical rainforests will alter termite communities and the maintenance of ecosystem processes. Using a large-scale termite suppression experiment, we found that termite activity and abundance increased during drought in a Bornean forest. This increase resulted in accelerated litter decomposition, elevated soil moisture, greater soil nutrient heterogeneity, and higher seedling survival rates during the extreme El Niño drought of 2015-2016. Our work shows how an invertebrate group enhances ecosystem resistance to drought, providing evidence that the dual stressors of climate change and anthropogenic shifts in biotic communities will have various negative consequences for the maintenance of rainforest ecosystems.
Subject(s)
Droughts , Isoptera/physiology , Rainforest , Soil , Animals , Borneo , Climate Change , El Nino-Southern Oscillation , Seedlings/growth & development , Tropical Climate , WaterABSTRACT
Two halogenated C15 acetogenins, named lembyne-A and lembyne-B, have been isolated from an unrecorded Laurencia species collected off the Malaysian waters. Their structures were deduced on the basis of spectroscopic evidence. Previously known elatol and iso-obtusol showed potent antibacterial activity against some marine bacteria.
Subject(s)
Anti-Bacterial Agents/isolation & purification , Bridged-Ring Compounds/isolation & purification , Halogens/chemistry , Hydrocarbons, Halogenated/isolation & purification , Rhodophyta/chemistry , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/metabolism , Bridged-Ring Compounds/chemistry , Bridged-Ring Compounds/metabolism , Hydrocarbons, Halogenated/chemistry , Hydrocarbons, Halogenated/metabolism , Spectrum AnalysisABSTRACT
The chemical compositions of five species of the red algal genus Laurencia from coastal waters of Okinawa Prefecture, Japan, have been investigated. A halogenated C(15) acetogenin, (12E)-lembyne-A, was isolated from L. mariannensis, and a halogenated sesquiterpene, (6R,9R,10S)-10-bromo-9-hydroxy-chamigra-2,7(14)-diene, was first found from L. majuscula as a naturally occurring compound. Laurencia nidifica yielded previously known laurinterol and isolaurinterol. Samples of L. cartilaginea and L. concreta afforded no halogenated metabolites. The structures of these halogenated metabolites as well as their antibacterial activity against some marine bacteria are reported.
Subject(s)
Anti-Bacterial Agents/isolation & purification , Halogens/isolation & purification , Rhodophyta/chemistry , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/metabolism , Anti-Bacterial Agents/pharmacology , Halogens/chemistry , Halogens/metabolism , Halogens/pharmacology , Magnetic Resonance Spectroscopy , Mass Spectrometry , Molecular Structure , StereoisomerismABSTRACT
In connection with our chemotaxonomic studies of Malaysian species of the red algal genus Laurencia, the chemical composition of Laurencia pannosa Zanardini was examined. Two halogenated sesquiterpenoids, named pannosanol (1) and pannosane (2), have been isolated along with a halogenated C15-acetogenin, (3Z)-chlorofucin (3). The structures of these compounds were determined from their spectroscopic data (IR, 1H NMR, 13C NMR, 2D NMR, and MS). Pannosanol and pannosane are novel halometabolites with an unusual rearranged chamigrane framework. Antibacterial activities of these metabolites against marine bacteria are also described.
