Earth's Hotspots Research Articles

Multi-Tissue Transcriptomes Yield Information on High-Altitude Adaptation and Sex-Determination in Scutiger cf. sikimmensis.

The Himalayas are one of earth’s hotspots of biodiversity. Among its many cryptic and undiscovered organisms, including vertebrates, this complex high-mountain ecosystem is expected to harbour many species with adaptations to life in high altitudes. However, modern evolutionary genomic studies in Himalayan vertebrates are still at the beginning. Moreover, in organisms, like most amphibians with relatively high DNA content, whole genome sequencing remains bioinformatically challenging and no complete nuclear genomes are available for Himalayan amphibians. Here, we present the first well-annotated multi-tissue transcriptome of a Greater Himalayan species, the lazy toad Scutiger cf. sikimmensis (Anura: Megophryidae). Applying Illumina NextSeq 500 RNAseq to six tissues, we obtained 41.32 Gb of sequences, assembled to ~111,000 unigenes, translating into 54362 known genes as annotated in seven functional databases. We tested 19 genes, known to play roles in anuran and reptile adaptation to high elevations, and potentially detected diversifying selection for two (TGS1, SENP5) in Scutiger. Of a list of 37 genes, we also identify 27 candidate genes for sex determination or sexual development, all of which providing the first such data for this non-model megophryid species. These transcriptomes will serve as a valuable resource for further studies on amphibian evolution in the Greater Himalaya as a biodiversity hotspot.

Mapping and Assessing Surface Morphology of Holocene Lava Field in Krafla (NE Iceland) Using Hyperspectral Remote Sensing

Iceland is well known for its volcanic activity due to its location on the spreading Mid Atlantic Ridge and one of the earth's hot spot. In the past 1000 years there were about 200 eruptions occurring in Iceland, meaning volcanic eruptions occurred every four to five years, on average. Iceland currently has 30 active volcano systems, distributed evenly throughout the so- called Neovolcanic Zone. One of these volcanic systems is the Krafla central volcano, which is located in the northern Iceland at latitude 65°42'53'' N and longitude 16°43'40'' W. Krafla has produced two volcanic events in historic times: 1724-1729 (Myvatn Fires) and 1975-1984 (Krafla Fires). The Krafla Fires began in December 1975 and lasted until September 1984. This event covered about 36-km2 surrounding area with lava, having a total volume of 0.25-0.3 km3. Previous studies of lava surface morphology at Krafla focused on an open channel area by remote sensing are essential as a complementary tool to the previous investigations and to extend the area of mapping. Using Spectral Angle Mapper (SAM) classification approach by selecting spectral reflectance end members, this study has successfully produced a detailed map of the surface morphology in Krafla lava field EO-1 Hyperion (Hyperspectral) satellite images. The overall accuracy of lava morphology map is 61.33% (EO-1 Hyperion). These results show that hyperspectral remote sensing is an acceptable alternative to field mapping and assessing the lava surface morphology in the Krafla lava field. In order to get validation of the satellite image's spectral reflectance, in-situ measurements of the lava field's spectral reflectance using ASD FieldSpec3 is essential.

Germination and emergence measurements could group individuals and species?

In the present study, the contribution of individuals to species variability and the contribution of each species in relation to the studied group were quantified, using nested analysis. Genetic parameters were also determined and PCA analysis was performed. Diaspores of Anadenanthera colubrina var. cebil, Cedrela fissilis, Ceiba speciosa, Lithraea molleoides, and Myracrodruon urundeuva that were collected in a fragmented area of the Cerrado Biome, one important Earth hotspot according to the Conservation International, were studied. More than 60 % of the total variability in the germination process and seedling emergence were attributed to the species and the high heritability values, above 0.80, registered for most of the characteristics evaluated, indicated that the largest proportion of the total variability is of genetic nature. The highest genetic variability was registered among L. molleoides and C. fissilis individuals. The asynchrony of the germination and emergence processes that groups the individuals of L. molleoides serves to distinguish this species from the others, confirming the high relative contribution of this species to the total variability detected in the nested analysis. The magnitude of genetic variability in the studied species in relation to the germination and emergence processes highlights the background variation inherent to these species that should be considered in conservation projects. Besides, the heritability and coefficient of genetic variation values, associated with the nested analysis open a new way to evaluate the genetic potential of the plants in relatively young phases, based on germination and emergence characteristics, within conventional experiments in seed studies.

Symmetries of volcanic distributions on Mars and Earth and their mantle plume dynamics

The symmetries in the distribution of major volcanic centers on Mars have been analyzed by employing a technique involving the angular self‐similarity of point fields. The distribution of all central vent volcanoes exhibits an axisymmetry along with a reflecting symmetry about a plane whose normal is the axis of axisymmetry. The latter axis is skewed by about 30° from the rotational axis and is suggested to represent the early axis of symmetry of the interior dynamics. The high level of symmetry of Mars' volcanic distribution may be the result of a focusing of seismic energy from a major impact in the Hellas area that formed the Hellas basin and may have triggered the onset of volcanic activity in the greater Tharsis area. If the highland paterae near the Hellas region are not taken into account in the analysis, an asymmetry with respect to the reflecting plane appears. This is probably representative of the Late Hesperian and Amazonian, when the once global volcanic activity had retreated to the Tharsis province. These angular symmetries suggest a simple pattern of long‐wavelength axisymmetric martian mantle convection involving a large stationary plume, as shown by our three‐dimensional (3‐D) spherical‐shell simulations. On the basis of these calculations, we venture to propose that the volcanic history of Mars reflects the transformation of a bipolar mantle plume structure into a single megaplume by the process of plume‐plume collision acting in concert with the deep Martian phase transitions. This transformation might have overcome the original pattern induced by a major impact forming the Hellas basin. We have repeated the procedure for the Earth's hotspot distribution, which revealed both axisymmetry and a certain level of reflecting symmetry. This similarity between the two planets is striking. The symmetries of the Earth's hotspot distribution are probably due to the interaction of the lower mantle megaplumes with the endothermic perovskite to γ‐spinel phase transition.

The effects of a deep mantle endothermic phase change on the structure of thermal convection in silicate planets

Previous studies of the effects of silicate phase transitions on mantle convection have tended to use numerical models in which the phase transitions have the same depths as found in the Earth's mantle, or in which a single transition is placed at a depth equal to half the layer thickness. This study presents a systematic investigation designed to examine the effects of an endothermic phase transition near the core‐mantle boundary of terrestrial type planets. The results indicate that a deep mantle endothermic phase change may trap the lower thermal boundary layer, allowing only one upwelling to penetrate the phase transition. In these situations the deep endothermic phase change excites a dipolar convection pattern. This mechanism may have a role in the degree one power observed in the distribution of the Earth's hotspots and the development of the Martian crustal dichotomy.

The Earth's hot spots : Vink, G.E., W.J. Morgan and P.R. Vogt, 1985. Scient. Am., 252(4):50–57

The Earth's hot spots : Vink, G.E., W.J. Morgan and P.R. Vogt, 1985. Scient. Am., 252(4):50–57