Population-Level Metrics of Trophic Structure Based on Stable Isotopes and Their Application to Invasion Ecology

Biological invasions are a significant driver of human-induced global change and many ecosystems sustain sympatric invaders. Interactions occurring among these invaders have important implications for ecosystem structure and functioning, yet they are poorly understood. Here we apply newly developed metrics derived from stable isotope data to provide quantitative measures of trophic diversity within populations or species. We then use these to test the hypothesis that sympatric invaders belonging to the same functional feeding group occupy a smaller isotopic niche than their allopatric counterparts. Two introduced, globally important, benthic omnivores, Louisiana swamp crayfish (Procambarus clarkii) and carp (Cyprinus carpio), are sympatric in Lake Naivasha, Kenya. We applied our metrics to an 8-year data set encompassing the establishment of carp in the lake. We found a strong asymmetric interaction between the two invasive populations, as indicated by inverse correlations between carp abundance and measures of crayfish trophic diversity. Lack of isotopic niche overlap between carp and crayfish in the majority of years indicated a predominantly indirect interaction. We suggest that carp-induced habitat alteration reduced the diversity of crayfish prey, resulting in a reduction in the dietary niche of crayfish. Stable isotopes provide an integrated signal of diet over space and time, offering an appropriate scale for the study of population niches, but few isotope studies have retained the often insightful information revealed by variability among individuals in isotope values. Our population metrics incorporate such variation, are robust to the vagaries of sample size and are a useful additional tool to reveal subtle dietary interactions among species. Although we have demonstrated their applicability specifically using a detailed temporal dataset of species invasion in a lake, they have a wide array of potential ecological applications

A continuous 55-million-year record of transient mantle plume activity beneath Iceland

In the North Atlantic Ocean, a mid-ocean ridge bisects the Icelandic mantle plume, and provides a window into its temporal evolution1, 2, 3. V-shaped ridges of thick oceanic crust observed south of Iceland are thought to record pulses of upwelling within the plume4, 5, 6, 7. Specifically, excess crust is thought to form during the quasi-periodic generation of hot solitary waves triggered by thermal instabilities in the mantle8. Here we use seismic reflection data to show that V-shaped ridges have formed over the past 55 million years—providing the longest record of plume periodicity of its kind. We find evidence for minor, but systematic, asymmetric formation of crust, due to migration of the mid-ocean ridge with respect to the underlying plume. We also find changes in periodicity: from 55 to 35 million years ago, the V-shaped ridges form every 3 million years or so and reflect small fluctuations in plume temperature of about 5–10 °C. From 35 million years ago, the periodicity changes to about 8 million years and reflects changes in mantle temperature of 25–30 °C. We suggest that this change in periodicity is probably caused by perturbations in the thermal state at the plume source, either at the mantle-transition zone or core–mantle boundary

Modern microbial mats and endoevaporites systems in Andean lakes a general approach

Puna wetlands and salars are a unique extreme environment all over the world, since their locations are in high-altitude saline deserts, largely influenced by volcanic activity. Ultraviolet radiation, arsenic content, high salinity, and low dissolved oxygen content, together with extreme daily temperature fluctuations and oligotrophic conditions, shape an environment that recreates the early Earth and, even more so, extraterrestrial conditions. Microbes inhabiting extreme environments face these conditions with different strategies, including formation of intricate microbial communities with an increasing degree of complexity. In that way, biofilms, mats, endoevaporitic mats, domes, and microbialites have been found to exist in association with salars, lagoons, and even volcanic fumaroles in Central Andean extreme environments. They form microbial ecosystems, where light and O2 availability decrease with depth stratification, promoting functional group diversity. This microbial diversity, together with the geochemistry, may favor the precipitation of minerals. This chapter summarizes general concepts in the environmental microbiology of extreme Andean ecosystems, which are explored throughout this book.Fil: Farias, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Saona Acuña, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; Argentin

Progress in Myrtacease genetics and genomics: Eucalyptus as the pivotal genus

The status of genomics and genetics research in the Myrtaceae, a large family of dicotyledonous woody plants, is reviewed with Eucalyptus as the focal genus. The family contains over 5,650 species in 130 to 150 genera, predominantly of neo-tropical and Southern Hemisphere distribution. Several genera are well known for their economic importance worldwide. Myrtaceae are typically diploids with small to intermediate genome size. Microsatellites have been developed for several genera while higher throughput marker systems such as diversity arrays technology and single nucleotide polymorphism are available for Eucalyptus. Molecular data have been fundamental to current perspectives on the phylogeny, phylogeography and taxonomy of the Myrtaceae, while numerous studies of genetic diversity have been carried out particularly as it relates to endangered, rare, fragmented, overharvested or economically important species. Large expressed sequence tag collections for species of Eucalyptus have recently become public to support the annotation of the Eucalyptus grandis genome. Transcriptomics in Eucalyptus has advanced by microarrays and next-generation sequencing focusing on wood development. Linkage maps for Eucalyptus display high synteny across species and have been extensively used to map quantitative trait loci for a number of traits including growth, wood quality, disease and insect resistance. Candidate gene-based association genetics have successfully found marker–trait associations for wood and fiber traits. Genomic selection experiments have demonstrated clear potential to improve the efficiency of breeding programs while freeze-tolerant transgenic Eucalyptus trials have recently been initiated. The recently released E. grandis genome, sequenced to an average coverage of 8�, will open up exceptional opportunities to advance Myrtaceae genetics and genomics research