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We studied four currently recognized endemics of Ruta (Rutaceae) from the Canary Islands, an oceanic biodiversity hotspot, to identify genetic variation, reconstruct evolutionary relationships and clarify the taxonomic delimitation of several recently discovered populations. We analysed four plastid DNA regions for a thorough population sampling of Ruta oreojasme on Gran Canaria, R. pinnata on Tenerife and La Palma and R. microcarpa and the only known population of the recently described R. nanocarpa on La Gomera. Bayesian clock dating analysis, haplotype network and ancestral area reconstructions were carried out. Our results reveal a complex, extremely dynamic and largely overlooked pattern of colonization and evolutionary history of Ruta in the archipelago. Thirty haplotypes were found, but only one of them was shared across more than one island. Species divergence and all colonization events in the Canary Islands were dated from the late Pliocene to the Pleistocene, and R. oreojasme has an earlier origin than its Canarian congeners. Multiple secondary colonization events between and within islands account for the diversification of R. pinnata and R. microcarpa. Our data cannot discard a possible independent origin of R. oreojasme and do not support the currently accepted circumscription of R. pinnata and R. microcarpa. Rather, the high levels of genetic differentiation detected suggest the existence of ongoing diversification processes and of new taxa. Urgent population-level conservation efforts should be undertaken, especially focused on the single population on La Gomera that can be attributed to R. microcarpa, R. nanocarpa and genetically distinct populations from La Palma and the palaeo-islands of Tenerife. [ABSTRACT FROM AUTHOR]

Mountain systems harbor a substantial fraction of global biodiversity and, thus, provide excellent opportunities to study rapid diversification and to understand the historical processes underlying the assembly of biodiversity hotspots. The rich biodiversity in mountains is widely regarded as having arisen under the influence of geological and climatic processes as well as the complex interactions among them. However, the relative contribution of geology and climate in driving species radiation is seldom explored. Here, we studied the evolutionary radiation of Oreocharis (Gesneriaceae), which has diversified extensively throughout East Asia, especially within the Hengduan Mountains (HDM), using transcriptomic data and a time calibrated phylogeny for 88% (111/126) of all species of the genus. In particular, we applied phylogenetic reconstructions to evaluate the extent of incomplete lineage sorting accompanying the early and rapid radiation in the genus. We then fit macroevolutionary models to explore its spatial and diversification dynamics in Oreocharis and applied explicit birth–death models to investigate the effects of past environmental changes on its diversification. Evidence from 574 orthologous loci suggest that Oreocharis underwent an impressive early burst of speciation starting ca. 12 Ma in the Miocene, followed by a drastic decline in speciation toward the present. Although we found no evidence for a shift in diversification rate across the phylogeny of Oreocharis , we showed a difference in diversification dynamics between the HDM and non-HDM lineages, with higher diversification rates in the HDM. The diversification dynamic of Oreocharis is most likely positively associated with temperature-dependent speciation and dependency on the Asian monsoons. We suggest that the warm and humid climate of the mid-Miocene was probably the primary driver of the rapid diversification in Oreocharis , while mountain building of the HDM might have indirectly affected species diversification of the HDM lineage. This study highlights the importance of past climatic changes, combined with mountain building, in creating strong environmental heterogeneity and driving diversification of mountain plants, and suggests that the biodiversity in the HDM cannot directly be attributed to mountain uplift, contrary to many recent speculations.[East Asian monsoons; environmental heterogeneity; Hengduan Mountains; incomplete lineage sorting; Oreocharis ; past climate change; rapid diversification; transcriptome.] [ABSTRACT FROM AUTHOR]

The humid mid-elevation montane forests (MMF) of the tropical Andes harbour high levels of plant species diversity, contributing to the exceptional overall diversity of the tropical Andean biodiversity hotspot. However, little is known about the diversification dynamics of MMF plant lineages compared to lineages in other Andean biomes. Here, we use Macrocarpaea (Gentianaceae) to investigate patterns of plant diversification in the MMF, using molecular dating with fossils and secondary calibration (from a family-wide phylogenetic analysis of Gentianaceae). We sequenced 76 of 118 recognized Macrocarpaea spp. for six markers to reconstruct a time-calibrated phylogenetic tree and infer the historical biogeography of Macrocarpaea using maximum-likelihood methods implemented in BioGeoBEARS, estimating diversification rates through time and among lineages with BAMM. We document a rapid radiation of Macrocarpaea in Andean MMF coinciding with rapid colonization and range expansion across the entire distribution of the genus in the Andes starting 7.2 Mya. Our results support allopatric founder-event speciation as the dominant process contributing to geographical phylogenetic structure across the genus. We propose that establishment of the MMF in the late Miocene, when the Andes attained critical elevation to modify regional climates, provided large new areas of suitable habitat for Macrocarpaea to quickly colonize and expand through repeated founder-events. We suggest that this wave of colonization and range expansion triggered rapid diversification, and, as the MMF became progressively occupied, the diversification rate slowed. Our study also supports the idea that MMF plant radiations are older and more slowly evolving than the quickly evolving lineages in the recent Andean high-elevation grasslands. [ABSTRACT FROM AUTHOR]

Eastern Australia encompasses the longest track (~2000 km) of age-progressive continental volcanoes on Earth. These so-called 'central volcanoes' are shield volcanoes considered as surficial expressions of Cenozoic mantle plume activity under the northward moving Australian continent. Here, we investigate three central volcanoes located in the southern, younger part of the volcanic track (Ebor, Nandewar, and Canobolas) with the aim of unraveling the plumbing system architecture during waning hotspot activity. We explore the duration of volcanic activity and compare long-term evolution of magmatic processes via 40Ar/39Ar geochronology, mineral and groundmass chemistry, mineral-melt thermobarometry, and Rhyolite-MELTS thermodynamic simulations. 40Ar/39Ar geochronology on groundmass and mineral separates indicates that Ebor is the oldest of the three volcanoes, with duration of at least ~1 Ma (20.4 ± 0.09 to 19.4 ± 0.07 Ma). Nandewar also lasted ~1 Ma (19.4 ± 0.03 to 18.5 ± 0.03 Ma). The Canobolas volcanic complex was younger and shorter lived at ~0.5 Ma (12.0 ± 0.02 to 11.55 ± 0.05 Ma). Interestingly, all three volcanoes share a repetitive tempo of ~0.1 Ma between eruptions. The volcanoes produced porphyritic to aphyric lavas with basalt to trachyte compositions. The phenocryst assemblage includes plagioclase and K-feldspar, pink and green clinopyroxene, rare olivine, and titanomagnetite. Textural and compositional zoning of phenocrysts reveals successive events of mafic replenishment and magma transport prior to eruption. Dissolution textures in plagioclase, coupled with increasing An and FeOt and decreasing Ba and Ce from crystal cores to mantles, indicate recharge with mafic, oxidised melt. Increasing Mg# and Cr from clinopyroxene cores to rims also supports primitive magma replenishment. Mineral–melt thermobarometry and Rhyolite–MELTS simulations indicate a main level of magma storage in the three volcanoes in the middle crust (18–25-km depth; ~1100°C), repeatedly replenished by undegassed, primitive melts. Green clinopyroxene cores crystallised in isolated pockets where magmas underwent extensive fractionation at depths of 15 to 30 km and ~800°C. The shallow level plumbing system was volumetrically minor and dominated by crystallisation of low-An plagioclase with large melt inclusions, possibly crystallised from degassed, reduced and evolved magma, as suggested by plagioclase hygrometry and fO2 modelling. Our combined geochronological and geochemical approach reveals that the three spatially separated but genetically linked volcanoes had comparable, complex plumbing system architectures. Fractionation and repeated magma rejuvenation were critical processes throughout the lifespans of volcanism, and eruptive tempos were controlled by recurrent mafic influx. The maficity of lavas and their crystal cargo correlate with the volume fraction of phenocrysts, suggesting mafic recharge was a key driver of mush remobilisation and eruption. Other volcanoes active during the late stages of plume activity in eastern Australia share similar textural and geochemical features, suggesting that waning hotspot activity may result in increased complexity in magma transport and storage. [ABSTRACT FROM AUTHOR]

We examined the floristics of granitoid inselbergs in the hitherto poorly documented south-eastern region of the Southwest Australian Floristic Region (SWAFR) and adjacent Great Western Woodlands, addressing several hypotheses of OCBIL (old, climatically buffered, infertile landscapes) theory. We found exceptional taxon richness (1550 taxa on 89 inselbergs, with 58 well-sampled inselbergs and 1493 taxa chosen for detailed analyses). Granite inselberg endemism declined towards the arid inland, although taxon richness did not. OCBILs are likely to be found up to 500 km inland, not ~300 km as previously hypothesized. Hybrids were extremely rare on the 58 inselbergs analysed, whereas rare species, including singletons, were abundant. Conversely, exotic weeds were less common than in the whole SWAFR flora (8.2% vs 12.8%). Granite plant communities were distributed in bands parallel to the south coast, approximating the general transition from the Esperance and Boylya Floristic Districts across the SWAFR boundary north into the Arid Zone's Great Western Woodlands. Positive correlations were found between several plant life forms and inselberg area. There was a decrease from the coast inland for most life forms, except for annual and graminoid herbs that increased in taxa inland. Thus, inselberg floristics exemplify the coast-to-inland OCBIL transition in this global biodiversity hotspot. [ABSTRACT FROM AUTHOR]

SARS-CoV-2 is an intensively investigated virus from the order Nidovirales (Coronaviridae family) that causes COVID-19 disease in humans. Through enormous scientific effort, thousands of viral strains have been sequenced to date, thereby creating a strong background for deep bioinformatics studies of the SARS-CoV-2 genome. In this study, we inspected high-frequency mutations of SARS-CoV-2 and carried out systematic analyses of their overlay with inverted repeat (IR) loci and CpG islands. The main conclusion of our study is that SARS-CoV-2 hot-spot mutations are significantly enriched within both IRs and CpG island loci. This points to their role in genomic instability and may predict further mutational drive of the SARS-CoV-2 genome. Moreover, CpG islands are strongly enriched upstream from viral ORFs and thus could play important roles in transcription and the viral life cycle. We hypothesize that hypermethylation of these loci will decrease the transcription of viral ORFs and could therefore limit the progression of the disease. [ABSTRACT FROM AUTHOR]

The Cook–Austral volcanic lineament is thought to be the product of three overlapping South Pacific hotspot tracks: Macdonald, Arago, and Rarotonga. However, the entire Rarotonga hotspot track consists of volcanism on just two islands, Rarotonga and Aitutaki, making it difficult to evaluate a hotspot origin for the young volcanism on these islands. We present new Sr–Nd–Hf–Pb–He isotopic and major and trace element data on Aitutaki—which has two periods of volcanism, older (9·39 Ma) and younger (1·382–1·941 Ma)—and Atiu in the Cook Islands to evaluate a hotspot origin. Like Atiu, the 'older volcanic series' at Aitutaki was tentatively linked with the Arago hotspot based on its age, but this link has never been tested with geochemistry. New geochemical data on the older Aitutaki volcanic series show clear affinities to the Arago hotspot volcano Atiu. In contrast, the younger Aitutaki volcanic series, erupted on a near-atoll, exhibits evidence for a rejuvenated, non-plume volcanic origin. If Rarotonga (1·157–1·697 Ma) and the young series at Aitutaki share a common heritage and mechanism for formation as previously proposed—they erupted only 260 km apart over an overlapping time period and exhibit overlapping radiogenic isotopic compositions—then Rarotonga lavas may also represent a subaerial rejuvenated volcanic stage capping an older volcano related to a different hotspot, consistent with no direct involvement from a mantle plume in the origin of subaerial lavas at Rarotonga. Rarotonga, Aitutaki, and Atiu exhibit some of the most extreme enriched mantle (EM) signatures in the Cook–Austral volcanic lineament. There are three geographically separated geochemical domains along the Cook–Austral volcanic lineament—a northern geochemical domain with EM geochemical signatures is separated from a southern EM domain by a 1000 km long central HIMU ('high μ', or high 238U/204Pb) domain—and Rarotonga, Aitutaki, and Atiu are part of the northernmost geochemical domain. There is a possible role for lithospheric thickness in controlling geochemical compositions of melt extracted from the mantle along the Cook–Austral volcanic lineament, particularly across the Austral Fracture Zone. However, this is complicated by the lineament's juxtaposition with the South Pacific Superswell, which may modify lithospheric behavior and complicate a simple lithospheric thickness model describing variable hotspot volcano compositions in the region. [ABSTRACT FROM AUTHOR]

Mediterranean marine protected areas (MPAs), designed to achieve long-term nature conservation, are progressively conquered by invasive species of tropical origin, posing novel challenges for managers and policymakers of the 21st century. In this study, we assessed the vulnerability of 142 coastal Mediterranean MPAs to nine of the most invasive fishes under current and future climatic conditions. We predicted invasive species' habitat suitability using an ensemble modelling approach, calibrating models on the entire distribution of the species. We categorized three risk levels for Mediterranean MPAs, based on the assumption that more suitable habitat conditions make protected areas more prone to invasion. Future projections forecasted an increase of suitable areas for all considered species in the Mediterranean basin. In the Levantine Sea, almost all MPAs are at high risk of invasion by the considered species both in the current and future scenarios. MPAs located in the other Mediterranean sectors have currently a low suitability for most invasive species, but their risk level will increase overall by 2050, especially in the South Adriatic Sea and off South Western Italy. By identifying spatial priorities in a global change context, we fill critical information gaps on the vulnerability of MPAs to the future expansion of warm-water invaders. [ABSTRACT FROM AUTHOR]

An understanding of the genetic composition of populations across management boundaries is vital to developing successful strategies for sustaining biodiversity and food resources. This is especially important in ecosystems where habitat fragmentation has altered baseline patterns of gene flow, dividing natural populations into smaller subpopulations and increasing potential loss of genetic variation through genetic drift. River systems can be highly fragmented by dams built for flow regulation and hydropower. We used reduced-representation sequencing to examine genomic patterns in an exploited catfish, Hemibagrus spilopterus , in a hotspot of biodiversity and hydropower development—the Mekong River basin. Our results revealed the presence of 2 highly divergent coexisting genetic lineages which may be cryptic species. Within the lineage with the greatest sample sizes, pairwise F ST values, principal component analysis, and a STRUCTURE analysis all suggest that long-distance migration is not common across the Lower Mekong Basin, even in areas where flood-pulse hydrology has limited genetic divergence. In tributaries, effective population size estimates were at least an order of magnitude lower than in the Mekong mainstream indicating these populations may be more vulnerable to perturbations such as human-induced fragmentation. Fish isolated upstream of several dams in one tributary exhibited particularly low genetic diversity, high amounts of relatedness, and a level of inbreeding (G IS = 0.51) that has been associated with inbreeding depression in other outcrossing species. Our results highlight the importance of assessing genetic structure and diversity in riverine fisheries populations across proposed dam development sites for the preservation of these critically important resources. [ABSTRACT FROM AUTHOR]

A better understanding of the spatiotemporal variation of human pressures, such as fishing, is crucial in the framework of ecosystem-based management. In this context, the spatiotemporal patterns of fishing effort from Greek trawlers operating in the eastern Mediterranean were studied using Vessel Monitoring System data over a 6-year period (2010–2015). The exploratory analysis of the data consisted of spatial autocorrelation techniques assessing clusters of high fishing effort (hotspots). Cycles, seasonality, trends, and the inter/intra-annual persistence of hotspots were also examined. The spatiotemporal association between the fishing effort (fine-scale: 5 × 5 km, monthly basis) and environmental/economic variables (depth, chlorophyll-a, fuel price, distance from port) was investigated through Generalized Additive Modelling. The results revealed higher fishing effort at depths <250 m, at distances between 15 and 55 km from the departure port and in areas of relatively high primary productivity. In winter, fishing effort was observed in shallower waters while during mid/late spring in deeper strata. In autumn, the effort was higher than any other season. Fishing effort was negatively correlated with fuel price and a decrease was noticeable during 2012–2013, the period of fuel price peaks. Potential implications of the methodology and results on spatial planning and management are discussed. [ABSTRACT FROM AUTHOR]

Background Refugia are island-like habitats that are linked to long-term environmental stability and, as a result, high endemism. Conservation of refugia and endemism hotspots should be based on a deep ecological and evolutionary understanding of their functioning, which remains limited. Although functional traits can provide such insights, a corresponding, coherent framework is lacking. Proposed Framework Plant communities in refugia and endemism hotspots should, due to long-term environmental stability, display unique functional characteristics linked to distinct phylogenetic patterns. Therefore, such communities should be characterized by a functional signature that exhibits: (1) distinct values and combinations of traits, (2) higher functional diversity and (3) a prevalence of similar traits belonging to more distantly related lineages inside, compared to outside, of endemism hotspots and refugia. While the limited functional trait data available from refugia and endemism hotspots do not allow these predictions to be tested rigorously, three potential applications of the functional signature in biogeography and conservation planning are highlighted. Firstly, it allows the functional characteristics of endemism hotspots and refugia to be identified. Secondly, the strength of the functional signature can be compared among these entities, and with the surrounding landscape, to provide an estimate of the capacity of endemism hotspots and refugia to buffer environmental changes. Finally, the pattern of the functional signature can reveal ecological and evolutionary processes driving community assembly and functioning, which can assist in predicting the effect of environmental changes (e.g. climate, land-use) on communities in endemism hotspots and refugia. Conclusion The proposed functional signature concept allows the systematic integration of plant functional traits and phylogeny into the study of endemism hotspots and refugia, but more data on functional traits in these entities are urgently needed. Overcoming this limitation would facilitate rigorous testing of the proposed predictions for the functional signature, advancing the eco-evolutionary understanding of endemism hotspots and refugia. [ABSTRACT FROM AUTHOR]

Seamounts formed adjacent to mid-ocean ridges are the most abundant on Earth, numbering several orders of magnitude higher than hotspot-related seamounts. The Taney Seamounts are a linear NW-SE-trending, near mid-ocean ridge chain consisting of five volcanoes located on the Pacific plate 300km west of San Francisco, California. Taney Seamount-A, the largest and oldest in the chain, has four well-defined calderas. These calderas have clear cross-cutting relationships, creating a relative chronology. The caldera walls and intracaldera pillow mounds were sampled systematically by a remotely operated vehicle to obtain stratigraphically controlled samples, a unique aspect of this study. Changes in lava geochemistry are consistent with an open-system sub-caldera reservoir that undergoes periodic collapse, replenishment, shallow crystallization, and eruption. Replenishing magmas contain large, anorthite-rich plagioclase crystals that exhibit sieve textures and zoning indicating interaction with percolating melt. The enrichment of elements in the lavas that are incorporated in plagioclase (e.g. aluminum, strontium) provides chemical evidence for the interaction between mantle-derived melts and plagioclase cumulates in the lower oceanic crust or upper mantle (8-12 km), prior to magmas entering the sub-caldera plumbing system. Based on trace element variations, the erupted lavas vary from typical peridotite-derived normal mid-ocean ridge basalt (N-MORB) compositions to those with an apparent residual garnet signature. Geochemical and thermodynamic modeling shows that decompression melting of a MORB mantle peridotite re-fertilized by garnet pyroxenite partial melts can reproduce the garnet signature observed in the Taney-A edifice lavas. Hence the magmatic architecture of Taney Seamount-A is characterized by the melting of a mixed lithology mantle, melt-rock interaction in the upper mantle to lower oceanic crust, and open-system evolution in a sub-caldera magma reservoir. [ABSTRACT FROM AUTHOR]

The origin of intraplate volcanoes in Northeast Asia is considered to be associated with upwelling of hot and wet asthenospheric materials in the big mantle wedge above the stagnant Pacific slab in the mantle transition zone. Among these intraplate volcanoes, Changbai is the largest and most active one, and very deep earthquakes (500–650 km depths) in the Pacific slab under East Asia occur ∼300 km to the east of the Changbai volcano. Integrating the findings of geophysical, geochemical and petrologic studies so far, we suggest a link between Changbai volcanism and the deep earthquakes in the Pacific slab. Many large shallow earthquakes occurred in the Pacific Plate in the outer-rise areas close to the oceanic trench, and sea water may enter down to a deep portion of the oceanic lithosphere through the active normal faults which generated the large outer-rise earthquakes. Sea water or fluids may be preserved in the active faults even after the Pacific Plate subducts into the mantle. Many large deep earthquakes are observed that took place in the subducting Pacific slab under the Japan Sea and the East Asian margin. At least some of the large deep earthquakes are caused by the reactivation of faults preserved in the subducting slab, and the fluids preserved in the faults within the slab may cause the observed non-double-couple components of the deep earthquake faulting. Fluids preserved in the slab may be released to the overlying mantle wedge through large deep earthquakes. Because large deep earthquakes occur frequently in the vicinity of the Changbai volcano, many more fluids could be supplied to this volcano than in other areas in Northeast Asia, making Changbai the largest and most active intraplate volcano in the region. [ABSTRACT FROM AUTHOR]

The caenogastropod family Littorinidae is almost exclusively marine, but a unique freshwater genus, Cremnoconchus, is known from India. Its members are restricted to montane streams on the western escarpment of the Western Ghats, at altitudes between 300 and 1400 m. Four species and several varieties were described in the 19th century, but no taxonomic study has been carried out for over 120 years and the last anatomical report was in 1935. Nevertheless, they are of unusual evolutionary interest and also of conservation concern as a genus endemic to the Western Ghats biodiversity hotspot. Based on anatomical study of newly collected material and examination of historical and type specimens, we present a systematic revision of Cremnoconchus, illustrating shells, radulae, and reproductive anatomy. The very large eggs, invaginated penial filament, and calcified operculum are unique among Littorinidae. Three valid, described species ( C. syhadrensis, C. conicus, C. canaliculatus) are recognized in the northern Western Ghats in Maharashtra state, where all can occasionally be found sympatrically. We describe an additional six new species from the central Western Ghats in a small area (linear distance 80 km) of Karnataka state, over 500 km south of the previously known range of the genus. Here the species each appear to be restricted to a single drainage system. Because of their highly restricted distribution and fragile habitat, this radiation of nine species is judged to be endangered. © 2013 The Linnean Society of London [ABSTRACT FROM AUTHOR]

The phase relations have been investigated experimentally at 200 and 500 MPa as a function of water activity for one of the least evolved (Indian Batt Rhyolite) and of a more evolved rhyolite composition (Cougar Point Tuff XV) from the 12·8–8·1 Ma Bruneau–Jarbidge eruptive center of the Yellowstone hotspot. Particular priority was given to accurate determination of the water content of the quenched glasses using infrared spectroscopic techniques. Comparison of the composition of natural and experimentally synthesized phases confirms that high temperatures (>900°C) and extremely low melt water contents (<1·5 wt % H2O) are required to reproduce the natural mineral assemblages. In melts containing ∼0·5–1·5 wt % H2O, the liquidus phase is clinopyroxene (excluding Fe–Ti oxides, which are strongly dependent on fO2), and the liquidus temperature of the more evolved Cougar Point Tuff sample (BJR; ∼940–1000°C) is at least 30°C lower than that of the Indian Batt Rhyolite lava sample (IBR2; 970–1030°C). For the composition BJR, the comparison of the compositions of the natural and experimental glasses indicates a pre-eruptive temperature of at least 900°C. The composition of clinopyroxene and pigeonite pairs can be reproduced only for water contents below 1·5 wt % H2O at 900°C, or lower water contents if the temperature is higher. For the composition IBR2, a minimum temperature of 920°C is necessary to reproduce the main phases at 200 and 500 MPa. At 200 MPa, the pre-eruptive water content of the melt is constrained in the range 0·7–1·3 wt % at 950°C and 0·3–1·0 wt % at 1000°C. At 500 MPa, the pre-eruptive temperatures are slightly higher (by ∼30–50°C) for the same ranges of water concentration. The experimental results are used to explore possible proxies to constrain the depth of magma storage. The crystallization sequence of tectosilicates is strongly dependent on pressure between 200 and 500 MPa. In addition, the normative Qtz–Ab–Or contents of glasses quenched from melts coexisting with quartz, sanidine and plagioclase depend on pressure and melt water content, assuming that the normative Qtz and Ab/Or content of such melts is mainly dependent on pressure and water activity, respectively. The combination of results from the phase equilibria and from the composition of glasses indicates that the depth of magma storage for the IBR2 and BJR compositions may be in the range 300–400 MPa (∼&leq;13 km) and 200–300 MPa (∼&leq;10 km), respectively. [ABSTRACT FROM AUTHOR]

SUMMARY The interpretation of seismic tomographic images of upper-mantle seismic wave speed structure is often a matter of considerable debate because the observations can usually be explained by a range of hypotheses, including variable temperature, composition, anisotropy, and the presence of partial melt. An additional problem, often overlooked in tomographic studies using relative as opposed to absolute arrival-times, is the issue of the resulting velocity model's zero mean. In shield areas, for example, relative arrival-time analysis strips off a background mean velocity structure that is markedly fast compared to the global average. Conversely, in active areas, the background mean is often markedly slow compared to the global average. Appreciation of this issue is vital when interpreting seismic tomographic images: 'high' and 'low' velocity anomalies should not necessarily be interpreted, respectively, as 'fast' and 'slow' compared to 'normal mantle'. This issue has been discussed in the seismological literature in detail over the years, yet subsequent tomography studies have still fallen into the trap of mis-interpreting their velocity models. I highlight here some recent examples of this and provide a simple strategy to address the problem using constraints from a recent global tomographic model, and insights from catalogues of absolute traveltime anomalies. Consultation of such absolute measures of seismic wave speed should be routine during regional tomographic studies, if only for the benefit of the broader Earth Science community, who readily follow the red = hot and slow, blue = cold and fast rule of thumb when interpreting the images for themselves. [ABSTRACT FROM AUTHOR]

The Tropical Andes is a diversity hotspot for plants, but there is a scant knowledge about patterns of genetic variation within its constituent species. Phaedranassa tunguraguae is an IUCN endangered plant species endemic to a single valley in the Ecuadorian Andes. We estimate the levels of genetic differentiation across the geographic distribution of P. tunguraguae using 12 microsatellite loci. We discuss factors that might influence the genetic structure of this species. Genetic distance was used to evaluate relationship among populations and geographic patterns. Bayesian methods were used to investigate population structure, migration, evidence of recent bottlenecks, and time of divergence. The 7 populations form 2 genetic clusters. These clusters show highly significant differentiation between them, along with isolation by distance. Allele richness decreases from the most diverse westernmost population to the least diverse easternmost population. The species overall shows an excess of homozygotes, with highest levels of inbreeding in the easternmost population. We found evidence of recent bottleneck events. Migration rates were in general low but were higher between populations within each of the clusters. Time of divergence between populations was related to historical volcanic activity in the area. Based on our results, we propose 2 management units for P. tunguraguae. [ABSTRACT FROM PUBLISHER]

The Easter Seamount Chain and Nazca Ridge are two of the most conspicuous volcanic features on the Nazca plate. Many questions about their nature and origin have remained unresolved because of a lack of geochronological and geochemical data for large portions of both chains. New 40Ar−39Ar incremental heating age determinations for dredged rocks from volcanoes east of Salas y Gomez Island show that, with very few exceptions, ages increase steadily to the east from 1·4 to 30 Ma, confirming that the two chains are parts of the same hotspot trail and indicating a hotspot location near Salas y Gomez rather than beneath Easter Island some 400 km farther west. Most of the volcanoes appear to have been erupted onto seafloor that was 5–13 Myr old, and no systematic variation in seafloor age at the time of seamount formation is apparent. At about 23 Ma, the formation of the Nazca Ridge ceased and that of the Easter Seamount Chain began, corresponding to a change in the direction of motion of the Nazca plate. Most of the studied rocks are moderately alkalic to transitional basalts. Their geochemical characteristics suggest that they represent relatively small mean amounts of partial melting initiating in garnet-bearing mantle and ending in the spinel facies. Nd–Sr–Pb isotopic compositions are within the range of values previously observed for volcanoes of the Easter Seamount Chain, west of Easter Island; moreover, most of our data cluster in a rather small part of this range [e.g. &varepsilon;Nd(t) is between +6·0 and +4·0]. The results indicate that the mantle source has consisted of the same two principal components, a C/FOZO-type component and a high-&varepsilon;Nd, incompatible-element-depleted Pacific mid-ocean ridge basalt-source-type component, since at least 30 Ma. The lack of any geochemical gradient along the chain east of Salas y Gomez implies that no systematic change over time has occurred in the proportions of these end-members. [ABSTRACT FROM AUTHOR]

New Pb, Sr, Nd, Hf, and He isotope data for Quaternary basalts, erupted from Debre Zeyit, Butajira, and the Wonji Fault Belt of the Main Ethiopian Rift, show systematic mixing relationships involving three distinct mantle sources. The Pb, Sr, Nd, and Hf isotopic arrays converge in a specific region of isotopic multi-space where they define the composition of the Afar mantle plume (centered about 206Pb/204Pb = 19·5, 87Sr/86Sr = 0·7035, ɛNd = +4·6, ɛHf = +9·3, 3He/4He > 15 RA). This plume end-member has an identical composition to that observed previously in oceanic basalts. The distinct isotopic arrays for the various volcanic areas in the Main Ethiopian Rift vary spatially in a systematic manner, and may be viewed as pseudo-binary mixing arrays. This further suggests that the Afar mantle plume interacts with the local continental lithosphere and upper mantle asthenosphere (mid-ocean ridge basalt-like source) through an ordered sequence of mixing events. Simple mixing models require that the mass proportions of continental lithosphere and upper mantle involved in magma generation must be nearly constant within each volcanic area, but that the proportion of plume material decreases regularly with distance southwestward along the Main Ethiopian Rift, away from the central axis of the plume. This systematic behavior means that continental lithosphere can become detached and mixed into the shallow mantle prior to the flow of upwelling plume material beneath the developing rift system. Detachment and mixing into the asthenosphere during continental rift evolution is an important process for producing the range of ambient upper mantle compositions sampled by mid-ocean ridge volcanism away from island hotspots. [ABSTRACT FROM PUBLISHER]

An analysis of microwave heating of a thin ceramic cylinder in a single mode, highly resonant cavity is presented. Realistic assumptions regarding the effective electrical conductivity, thermal parameters, and physical dimensions are adhered to throughout. Consequently, the model developed herein incorporates most of detuning and a local electric feild perturbation on the heating process. The model presented takes the form of a one-dimensional reaction–diffusion equation which contains a functional. The developement of this equation is the product of a systematic modelling process that involves S-matrix theory, a small-Biot-number asymptotic analysis, and a matched asymptotic analysis of a non-standard electromagnetic scattering problem. This equation reveals both the mathematical structure and physical mechanism for the formation of hot spots. An accurate numerical method which approximates the solution of this equation is presented. The results agree qualitatively with experiments and predict observed trends. [ABSTRACT FROM PUBLISHER]