Volcanic Belt Research Articles

A new species of Phyllopalpus Uhler (Orthoptera: Trigonidiidae) from Mexico

A new species of the Sword-tailed Cricket genus Phyllopalpus Uhler (Trigonidiidae: Phylloscyrtini), from Tzitzio, in the Trans-Mexican Volcanic Belt, Michoacán, Mexico, is described and illustrated. Morphological and molecular data are integrated to describe Phyllopalpus nicolaita sp. nov. The new species is similar to Phyllopalpus caeruleus (Saussure) from Mexico, from which the color pattern of the body can distinguish it.

Quercus purhepecha (Fagaceae), a new species of shrub oak endemic to the state of Michoacán, Mexico

Within the genus Quercus there are species with a shrubby habit that have been little studied worldwide. In Mexico, several shrub species within section Quercus are taxonomically highly problematic. These include eight named taxa that share traits such as abaxially tomentose leaves and growth of stems from one or multiple rhizomes, and there is evidence of additional undescribed species. Here, Quercus purhepecha is described and illustrated as a new tomentose shrubby white oak species, with a very restricted distribution within the Cuitzeo basin in the Trans-Mexican Volcanic Belt (TMVB), Michoacán state, Mexico. This new species is morphologically compared with Q. frutex, Q. microphylla and Q. repanda, which are similar taxa also distributed in the TMVB. In addition, a potential distribution model of Q. purhepecha for the Cuitzeo basin is presented.

The 1912 Seismic Swarm in Guadalajara, Mexico: An Example of Intense and Unusual Seismicity in the Trans-Mexican Volcanic Belt

Abstract The residents of the Guadalajara, Mexico metropolitan area awakened on 8 May 1912 to a strong earthquake. In the next two months, ∼1500 shocks followed this first event. Two additional clusters of microearthquakes occurred in July and September. Although no significant structural damage was reported, several churches, public buildings, and private dwellings in the cities of Guadalajara and Zapopan suffered damage. Based on the macroseismic data, the intensity of the larger earthquakes was modified Mercalli intensity (MMI) VI–VII. The area that strongly felt the earthquakes and where the damage was concentrated is contained within a radius of ∼5 km. We assume that the swarm took place within this circle. Based on the relations of MMI versus peak ground acceleration (PGA), it is estimated that the PGA during the swarm was ∼190 gals. The magnitude of the largest earthquakes in the swarm was initially estimated as Mw 5.7, using a published PGA-to-Mw relation. However, this relation was based on earthquakes located 20 km away from downtown Guadalajara. Considering that the distance of the swarm from the city was ∼5 km, the magnitude of the largest events in the swarm was recalibrated as Mw 4.7. A second estimate of the magnitude was based on ground-motion models to calculate the PGA resulting from an earthquake located 5 km away, at a depth of 1 km. The resulting magnitude is Mw 5.3 ± 0.5. Thus, we suggest that the largest earthquakes of the swarm had an approximate magnitude of Mw 5.0. The location of the swarm suggests the presence of active faults underlying the metropolitan area of Guadalajara, where no seismicity has been recorded. This should be carefully considered to assess the seismic hazard of this important city of over 5 million people.

Array analysis of P-wave polarization data for constraining near-surface shear wave speeds: Aplication to theValley of Mexico seismic network

SUMMARY We present an array method for constraining near-surface shear wave speed values from P-wave polarization data. As the direction of P-wave particle motion is determined both by the incident ray parameter and the local surficial shear wave speed, the latter can be inferred from three-component seismic records if the ray parameter is estimated first. Previous studies have analysed data recorded at a single station from various earthquakes in order to estimate near-surface shear wave speed. In contrast, this paper analyses data recorded at an array of stations. As such, this method can estimate both ray parameter data for the recorded earthquakes and near-surface shear wave speed values at the studied sites. And as an advantage, the method can analyse records of local and regional earthquakes where ray parameter information cannot be reliably estimated using 1D reference velocity models. Additionally, by processing polarization data spanning multiple events and stations, our method provides robust estimates for near-surface shear wave speed values. We apply this array-based method to a seismic array covering the Valley of Mexico. Analysed records correspond to regional earthquakes with epicentral distances of roughly 300 km. The corresponding ray parameter values for all earthquakes were estimated from the delay of the seismic waves arrival throughout the network as all stations have a reliable time reference. Near-surface shear wave speed values estimated from the array-based polarization analysis are correlated with major geological features of the area such as the Trans-Mexican Volcanic Belt and the local basin. We also apply the presented method to a minimal data scenario. The flexibility of this method allows it to employ a single ray parameter value as input, producing robust estimates for near-surface shear wave speed values within our case study. This feature becomes useful in a variety of scenarios, such as utilizing seismic data lacking timing information. The presented method constitutes an accessible and inexpensive alternative to study shallow seismic structure, opening opportunities to expand and complement current tools and techniques to assess seismic hazards.

Northward migration past the nearctic biogeographical divide; neotropical Gyrodactylus spp. infecting Astyanax have crossed the Trans-Mexican Volcanic Belt

The neotropical fish genus Astyanax (Characidae) and its associated helminths migrated northward from South America following the Great American Biotic Interchange (GABI): ca. 150 Astyanax spp. are found throughout South and Central America, up to the Mexico-USA border. Most characids are distributed south of the Trans-Mexican Volcanic Belt (TMVB), which bisects the country and represents a major transition zone between the neotropical and nearctic realms. Here, we characterize parasites of the monogenean genus Gyrodactylus infecting Astyanax spp. in Mexico: Astyanax aeneus south of the TMBV, Astyanax mexicanus north of it. Based on morphological, phylogenetic (internal transcribed spacer (ITS) and cytochrome oxidase subunit II (cox 2)) and statistical analyses of morphometric data, we confirmed the validity of Gyrodactylus pakan and Gyrodactylus teken, and erected two new species, Gyrodactylus aphaa n. sp. and Gyrodactylus ricardoi n. sp. These four gyrodactylids are part of a complex of morphologically cryptic species, which are phylogenetically closely related to each other, and sister species to Gyrodactylus carolinae and Gyrodactylus heteracanthus, parasites of characins in Brazil. Four gyrodactylid lineages (G. pakan, G. ricardoi n. sp., G. teken, Gyrodactylus sp. A) are distributed north of the TMVB; G. pakan is also widely distributed south of the TMVB, together with G. aphaa n. sp. Based on the ITS phylogeny, Brazilian parasites form a sister clade to all Mexican gyrodactylids, whose derived clades are distributed in progressively more northerly latitudes in Mexico – the three most-derived species north of the TMVB. This would suggest that gyrodactylid species diverged gradually, presumably as their characid fish hosts colonized and adapted to new environments north of the TMVB.

Forms of occurrence metals and metalloids in products of the Mutnovsky volcano gas-hydrothermal activity

On the basis of concentrate analysis of the Mutnovsky volcano thermal sites substance, new data of the ore elements forms of occurrence were obtained. In the course of large-scale hydrothermal alteration of volcanic rocks, with the participation of magmatic fluids and meteoric waters, metals and metalloids are transported to the surface, which are concentrated in the form of the main or impurity components of new-forming minerals. Sulfides of copper, zinc, mercury, silver and barium sulfate are confidently diagnosed, in which, in addition to mineral-forming Zn, Cu, Hg, Ag and Ba, admixtures of Mn, Cd, Sr, I, Cl, Te, Pb are present. Micron-sized phases were found containing Ru, Os and Ir (laurite), Pb (galena) as the main components, as well as intermetallic compounds (Fe–Ni), (Fe–Ir–Os), (Pb–Bi), (Bi–Te) and native Au. Most of the new-forming mineral individuals are associated with a mineral of the pyrite-marcasite group, which contains admixtures of As, Cu, Ni, and Co. Platinoids Os, Ir, Ru among the new-forming minerals within the East Kamchatka volcanic belt were discovered for the first time.

Distinct mechanisms controlling and influencing the supply of clay-sized sediments to the northern shelf of the Sea of Okhotsk since the Last Glacial Maximum

The Sea of Okhotsk is a transitional zone between East Asia and northwestern Pacific Ocean. As a result, its massive thick sediments contain numerous important records of geological past, such as the mechanisms of materials and energy exchanges. However, the scarcity of studies tracing the provenance of clay-sized sediments in the sea has limited the progress of reconstructing the paleoclimate of East Asia. In this study, clay mineral analysis was conducted on 31 surface stations and the LV87–54-1 core. These results were combined with grain-size to provide reliable evidence for distinct mechanisms controlling the influx of clay-sized sediments into the northern shelf of the Sea of Okhotsk since 23 ka. Results of provenance analyses suggested that clay-sized sediments in the northern shelf mainly originated from its northwestern shelf, the Okhotsk–Chukotka volcanic belt, and the Kamchatka Peninsula. Clay-sized sediments of the northern shelf was primarily transported from the northwestern shelf and the Okhotsk–Chukotka volcanic belt after 23 ka, while those analogues from the Kamchatka Peninsula increased after 11.7 ka. Based on variations in clay mineral ratios, sediments from the northwestern shelf were mainly transported by the North Okhotsk Countercurrent, wherein rapid millennial-scale variations were influenced by the high-latitude Arctic Oscillation (from the Last Glacial Maximum to the Last Deglaciation) and the low-latitude East Asian summer monsoon (including the Holocene), respectively. By contrast, the influx of clay-sized sediments from the western Kamchatka Peninsula might be mainly controlled by the intensity of the West Kamchatka Current. From the Last Glacial Maximum to the Last Deglaciation, north and northwest geostrophic winds dominated in winter, and the West Kamchatka Current shifted eastward. Since the Holocene, weakened north and northwest geostrophic winds, but strengthened east winds caused a series of rapid millennial-scale variations in the West Kamchatka Current.

Rabbit Hemorrhagic Disease Virus in Mexico in 2020-2021: Risk Areas and Climatic Distribution.

Mexico is home to 14 species of lagomorphs, 6 of which are endemic. Studies on diseases affecting native lagomorphs are scarce, and in most cases, the impact on their populations remains largely unknown. Rabbit hemorrhagic disease virus (RHDV), especially the RHDV2 variant, causes a serious and extremely contagious disease, resulting in high mortality rates and major declines in wild lagomorph populations. The objectives of this study were to identify disease hotspots and critical biodiversity regions in Mexico through the combined use of disease information and lagomorph distribution maps and to determine the areas of greatest concern. In total, 19 states of Mexico recorded RHDV2 from April 2020 to August 2021, and 12 of them reported the wild species Sylvilagus audubonii, Lepus californicus, and unidentified Leporidae species. The distribution of RHDV2 in Mexico can be closely predicted from climatic variables. RHDV2 hotspots are located in the central-southern area of the Mexican Highlands and the Trans-Mexican Volcanic Belt, where the virus affects multiple species. This knowledge is essential for proposing specific actions to manage and preserve lagomorph populations at risk and address these issues as soon as possible.

Culture, traditions and natural resources of Mexican lakes under the onslaught of anthropic pressures and climate change

Indigenous people and local communities play a vital role in conserving inland water ecosystems and their resources through their cultural and spiritual values embedded in the geographic, socio-political, and economic contexts. The Central Mexico lakes along the Trans-Mexican Volcanic Belt harbored important prehispanic cultures that hybridized during the Spanish conquest, evolving into modern Mexico and changing how lakes were valued. The terrestrial Spanish ways of life were inimical to the prehispanic indigenous lacustrine culture. After the conquest, various actions were carried out to drain the lakes for urban growth and to provide agricultural land. The result has been a decline (e.g., Lake Cuitzeo, Michoacán) and, in some extreme cases, the near disappearance (e.g., Lake Texcoco, Mexico City) of what were once extensive water bodies. Unsustainable use of resources, unsympathetic spatial planning (anthropic impacts), and climate change to warmer/drier conditions have all placed additional pressure on the inland ecosystems. Nonetheless, as herein presented, the prehispanic lacustrine cultural knowledge and traditions persist locally in some locations, having been perpetuated by indigenous people's traditions and habits.

Olivine Time-Capsules Constrain the Pre-Eruptive History of Holocene Basalts, Mount Meager Volcanic Complex, British Columbia, Canada

Abstract The Canadian segment of the Cascade Volcanic Arc (i.e. the Garibaldi Volcanic Belt) comprises more than 100 eruptive centres, spanning the entire Quaternary period (Pleistocene to Holocene in age), and with deposits ranging in composition from alkaline basalt to rhyolite. At least one of the volcanoes is currently active; Mount Meager / Q̓welq̓welústen erupted explosively 2360 years BP and has ongoing fumarolic activity. Long-term forecasting of eruption frequency and style depends on reconstruction of the history and timescales of magmatic processes preceding previous volcanic eruptions. Utilising diffusion chronometry, we investigate the Mount Meager Volcanic Complex focusing on Holocene olivine-phyric basalts (Lillooet Glacier basalts) exposed by the retreat of the Lillooet Glacier. We identify two distinct olivine populations in samples of quenched, glassy basalt lavas that record different magmatic processes and histories. Glomerocrysts of Fo83 olivine phenocrysts, entrained and transported by a hot mafic input, form Population 1. These exhibit resorption and normally zoned outermost rim compositions of Fo76–78; a third of them also show interior reverse compositional zoning. A second population of skeletal microphenocrysts have the same composition as the phenocryst rims (i.e. Fo76–78) and are in equilibrium with the adjacent matrix glass. We estimate the pre-eruptive temperature-fO2 conditions in a shallow reservoir (100 MPa; ~3 km) for a melt with H2O content of 0.5 to 1 wt % as ~1097°C to 1106°C (± 30°C), and NNO + 0.5 (±1.1), respectively. Using these input parameters, we report Fe-Mg diffusion chronometry results for 234 normally zoned profiles from 81 olivine phenocrysts. Diffusion modelling of compositional profiles in oriented crystals indicates pre-eruptive magmatic residence times of 1 to 3 months. These remarkably short residence times in shallow reservoirs prior to eruption suggest very short periods of unrest may precede future eruptions.

Teleseismic measurements of Upper Mantle Shear-Wave Anisotropy in Southern Mexico

The Mexican subduction system is an ideal region to study 3-D mantle deformation patterns in response to changes in slab geometry and the presence of tears. Shear-wave splitting measurements were made using SKS, SKKS, and PKS waves in southern Mexico, where the Cocos slab subducts beneath the North American and western Caribbean plates. For most of southern Mexico, the results are consistent with predominantly trench-normal fast polarization directions that can be interpreted as a consequence of sub-slab entrained flow and 2-D corner flow in the mantle wedge in the presence of A-type olivine fabric (or similar). This pattern of trench-perpendicular fast axes extends northward to the region southeast of the Trans-Mexican Volcanic Belt. Beneath its eastern end, fast axes rotate ∼20° clockwise and are likely controlled by the absolute motion of the North American plate. In southeastern Mexico, along the coast and above the mantle wedge tip, the fast axes are trench-normal and the delay times are the shortest. They were interpreted to result from a possibly serpentinized mantle wedge tip. In the same region above the mantle wedge core, the splitting parameters appear to result from different flow patterns in the mantle wedge and the sub-slab mantle.

Host Species and Environment Shape the Skin Microbiota of Mexican Axolotls

Skin microbiomes in amphibians are complex systems that can be influenced by biotic and abiotic factors. In this study, we examined the effect of host species and environmental conditions on the skin bacterial and fungal microbiota of four obligate paedomorphic salamander species, commonly known as axolotls (Ambystoma andersoni, A. dumerilii, A. mexicanum, and A. taylori), all of them endemic to the Trans-Mexican Volcanic Belt. We found that despite their permanent aquatic lifestyle, these species present a host-specific skin microbiota that is distinct from aquatic communities. We identified skin-associated taxa that were unique to each host species and that differentiated axolotl species based on alpha and beta diversity metrics. Moreover, we identified a set of microbial taxa that were shared across hosts with high relative abundances across skin samples. Specifically, bacterial communities were dominated by Burkholderiales and Pseudomonadales bacterial orders and Capnodiales and Pleosporales fungal orders. Host species and environmental variables collectively explained more microbial composition variation in bacteria (R2 = 0.46) in comparison to fungi (R2 = 0.2). Our results contribute to a better understanding of the factors shaping the diversity and composition of skin microbial communities in Ambystoma. Additional studies are needed to disentangle the effects of specific host associated and environmental factors that could influence the skin microbiome of these endangered species.

Environmental and anthropogenic factors mediating the functional connectivity of the mesquite lizard along the eastern Trans-Mexican Volcanic Belt.

Functional connectivity, the extent to which a landscape facilitates or impedes the dispersal of individuals across the landscape, is a key factor for the survival of species. Anthropogenic activities, such as urbanization, agriculture and roads, negatively impact functional connectivity of most species, particularly low-vagility species like lizards. Here, we examine how a landscape modified by anthropogenic activities affects the functional connectivity, at both broad and fine scales, of a widely distributed generalist lizard Sceloporus grammicus in the eastern Trans-Mexican Volcanic Belt, Mexico. We estimated for the first time the species' genetic structure, gene flow and functional connectivity in agricultural and forest zones using genomic data, a comprehensive landscape characterization and novel methods including gravity models. Our results showed not only marked genetic differentiation across the study region but also that functional connectivity is maintained for tens of kilometres despite S. grammicus low vagility. Specifically, we found that substrate and air temperature facilitated connectivity over broad and fine scales, respectively, while agricultural cover, relative humidity and slope were important for connectivity and gene flow. Contrastingly, forest cover and roads favoured (broad-scale) and limited (fine-scale) connectivity, likely associated with movement facilitated by small forest patches and with thermoregulation. Altogether, these results support that S. grammicus alternates its thermoregulatory behaviour depending on the distance travelled and the habitat environmental conditions, and that it can disperse through relatively modified landscapes, mainly using agricultural zones. The information obtained is crucial to understanding the response of lizards to current anthropogenic pressures and their potential to adapt.

Chorotypes and geographic relationships among endemic species of the Transmexican Volcanic Belt, Mexico

The Transmexican Volcanic Belt (TVB) is a complex biogeographical province characterized by several areas of endemism and high diversity of flora and fauna produced by complex geological and evolutionary processes. Chorotypes are biogeographical patterns that occur either when 2 or more independently distributed species share the same occupied area, or even when a single species’ distribution area differs significantly from others. Here, we identified chorotypes of 167 endemic species inhabiting the TVB using geographic distribution models and quantitative methods. Of those species, 136 were included in 11 chorotypes, named I to XI. In addition, the insect Aedes niveoscotum constituted chorotype XII. The 30 remaining species did not belong to any chorotype. All chorotypes included species from different taxonomic groups, which may be due to a shared biogeographical history. The chorotypes with the highest richness were located in the central and eastern TVB, suggesting that volcano peaks and surrounding areas are important for generating the particular environmental conditions that restrict the distribution of species of different taxonomic groups.

Petrogenetic evolution of the Jalapa del Marqués pluton: Miocene arc magmatism in southern Mexico and its tectonic implications

Arc-related plutonic rocks in southern Mexico occur along the Pacific coast in the Sierra Madre del Sur (SMS) igneous province. These rocks record the migration of the Caribbean–North America–Farallon/Cocos junction towards the east between the Late Cretaceous and Miocene. However, little is known about the petrogenesis of igneous rocks that were emplaced during the latest expressions of magmatism in the SMS (i.e., early–middle Miocene). Based on fieldwork, petrography, whole-rock and mineral geochemistry, thermobarometric calculations, and zircon UPb dating, we document the petrogenetic evolution of the Jalapa del Marqués pluton and adjoining intrusions, which are the youngest so far dated in the SMS and are located ∼150 km inland from the present-day trench. This subduction-related magmatic complex consists of granites, granodiorites, diorites, dacite porphyries, and intermediate-to-felsic dikes, whose geochemical features suggest early evolutionary processes driven by fractionation of amphibole ± clinopyroxene (moderate–high pressures) or plagioclase (low pressures). Pulses of evolved magmas were episodically injected into upper-crustal reservoirs (7–14 km) over ∼9 Myr, starting at 22.14 ± 0.65 Ma (2σ)—earlier than previously thought (∼15.7 Ma)—and producing subsequent pulses at 19.45 ± 0.36 Ma, from 16.36 ± 0.37 to 15.8 ± 0.34 Ma, and from 13.9 ± 0.5 to 13.3 ± 0.2 Ma. These ages correlate with the onset and early stages of volcanic centers in the Trans-Mexican Volcanic Belt (TMVB), some of which were located up to 500 km landward from the present-day trench. The large difference in the distance-to-trench between coeval magmatism in the Jalapa del Marqués pluton and the TMVB, indicates a variation in the subduction angle between two segments of the Farallon/Cocos Plate that were likely separated by a slab-tear. The eastward migration of this slab-tear (along with the triple junction) terminated the magmatic activity in the SMS by switching the locus of magmatism to the TMVB. This probably occurred shortly after the studied magmatic complex was assembled.

Provenance of sediments and environmental risk assessment of heavy metals in the “Mis Amores” beach, Veracruz, Gulf of Mexico, Mexico

In this study, grain-size, mineralogy, and geochemistry of Mis Amores (MA) beach sediments, Tuxpan, Veracruz State, Gulf of Mexico are analyzed. The textural parameters reveal that the sediments are fine-grained and vary from well-sorted to very well-sorted nature. The SEM-EDS analysis reveal that the sediments are abundant in minerals such as quartz, alkali feldspars, zircon, ilmenite, and pyroxene. Geochemically, the sediments are classified as sub-arkose type. The Chondrite normalized rare earth elements (REE) pattern suggest that the source area is dominated by felsic and intermediate igneous rocks (Eu/Eu* = 0.90 - 1.19, number of samples n = 16). The provenance discrimination diagrams indicated that the MA sediments were derived by the weathering of felsic igneous rocks, probably from the Trans Mexican Volcanic Belt. The results of this study reveal that the Tuxpan River played an important role in delivering sediments to the MA beach area. The environmental indices suggest that the sediments are moderately contaminated by Zn and moderate to extremely contaminated by Cu and As. The Cu (> 84%) and Zn (> 82%) concentrations are predominantly associated with the exchangeable fraction, which are readily bioavailable. Cu, As, and Zn in the MA sediments were derived from the agricultural activities and waste water discharges from the sanitary network of the Tuxpan town and port.

Response of the subalpine bunchgrasses to wildfires and its effects in the relative abundance of the volcano rabbit in the Ajusco-Chichinautzin Mountain Range.

The volcano rabbit (Romerolagus diazi) is a lagomorph endemic to the central mountains of the Trans-Mexican Volcanic Belt and is classified as threatened at extinction risk. It is a habitat specialist in bunchgrass communities. The annual wildfires that occur throughout its distribution range are a vulnerability factor for the species. However, the effects of wildfires on volcano rabbit populations are not fully understood. We evaluated the occupancy and change in the volcano rabbit relative abundance index in the burned bunchgrass communities of the Ajusco-Chichinautzin Mountain Range during an annual cycle of wildfire events. Additionally, we assessed the factors that favor and limit occupation and reoccupation by the volcano rabbit using the relative abundance index in burned plots as an indicator of these processes. The explanatory factors for the response of the volcano rabbit were its presence in the nearby unburned bunchgrasses, the height of three species of bunchgrass communities, the proportion of different types of vegetation cover within a 500 m radius around the burned plots, heterogeneity of the vegetation cover, and the extent of the wildfire. Statistical analyses indicated possible reoccupation in less than a year in burned bunchgrass communities adjacent to unburned bunchgrass communities with volcano rabbits. The relative abundance index of volcano rabbits was not favored when the maximum height of the Muhlenbergia macroura bunchgrass community was less than 0.77 m. When the vegetation around the burned plots was dominated by forest (cover >30% of the buffer) and the fire was extensive, the number of latrines decreased per month but increased when the bunchgrass and shrub cover was greater around the burned plots. While the statistical results are not conclusive, our findings indicate a direction for future projects, considering extensive monitoring to obtain a greater number of samples that contribute to consolidating the models presented.

A new endemic species and species richness distribution of the genus <em>Pinguicula</em> (Lentibulariaceae) in the Trans-Mexican Volcanic Belt, Mexico

Background: The genus Pinguicula harbors 110 species, of which 53 are distributed in Mexico. The formation of the Mexican mountains has favored the Pinguicula diversification. Pinguicula specimens collected in the State of México, along the Trans-Mexican Volcanic Belt (TMVB) do not correspond with any known species. Questions: Do the collected specimens belong to a new species? What is its conservation status? How many Pinguicula species are there along the TMVB and how do they differentiate? How is the Pinguicula species richness distributed? Studied species: Pinguicula. Study site and dates: TMVB, 2005-2023. Methods: Based on herbarium specimens and recently collected material, a morphological analysis and description were made. Conservation status was assessed following IUCN Red List Categories and Criteria. Herbarium specimens and digital records of Pinguicula from the TMVB were examined to generate a list and key. We analyzed the richness distribution of Pinguicula by states, vegetation types, elevation ranges, and grid cells. Results: Pinguicula tlahuica is proposed as a new species. It is distinguished by the linear-spatulate summer leaves. The new species falls into the Endangered (EN) category. Along the TMVB, 16 species of Pinguicula are distributed. The State of México, Hidalgo and Michoacán, and the pine-oak forest were the richest. Pinguicula appeared between 759-3,427 m asl. The grid cell analyses revealed different areas with high richness. Conclusions: Along the TMVB, the Pinguicula species richness centered on the Eastern and Western sectors. Pinguicula crassifolia, P. michoacana, P. tlahuica, and P. zamudioana are endemic to the TMVB.

A phylogenetically distant clade of Nostoc–like (Cyanobacteria) taxa with the description of Reofilinostoc matlalcueyense gen. et sp. nov. from an extreme environment

Although species of the order Nostocales have morphological similarities to each other, some Nostoc species have been considered cryptic and are classified in the families Nostocaceae, Nodulariaceae and Aphanizomenaceae. Since then, the phylogenetic and morphological evaluation of Nostoc-like organisms has led to the taxonomic revision of some genera in different families. In the present work a cyanobacterium morphologically identified as Nostoc was isolated from an extreme cold lotic environment, in a high mountain of the Transmexican Volcanic Belt, and was taxonomically and phylogenetically characterized based on a polyphasic approach. Analysis of the 16S rRNA gene sequence references: Reofilinostoc matlalcueyense gen. et sp. nov. Thus, establishing a new genus of the family Nodulariaceae. The morphology of Reofilinostoc in the wild is reminiscent of a mouse ear, it is of 0.4-1.2 cm in length and has a firm cartilaginous texture; colonies can be pale green, brown or dark green in colour. Through a microscopic inspection, the filaments resemble to Komarekiella atlantica, Desikacharya nostocoides and Minunostoc cylindricum. While, the phylogenetic approach yielded similar results and consistently showed that Reofilinostoc matlalcueyense F02 (OR724089) is closely related to D. nostocoides and M. cylindricum in the core clade of Nodulariaceae. This research revealed that some comparisons between genera of Nodulariaceae exhibited similarity values higher than 97%, such as Atlanticothrix vs. Goleter and Cyanocohniella vs. Anabaenopsis. Nevertheless, in comparison to these phylogenetically closer genera, a substantial difference in the length and structure of D1-D1’, Box-B and V3 helix was demostrated; where Reofilinostoc, Desikacharya, and Minunostoc are part of the Nodulariaceae family; leading to the establishment of Reofilinostoc gen. nov., with Reofilinostoc matlalcueyense sp. nov. as the type species.

Analyzing possible seismic velocity changes in Mexico City using seismic noise interferometry

The seismic response of the Mexico City basin has received plenty of attention as one of the most relevant cases of ground motion amplification. A recent study showed possible velocity variations of the deposits in both the lake bed and firm ground. A clear drop in seismic velocity was observed during the 2017.09.19 earthquake (Mw 7.1) in addition to more subtle seismic velocity changes related to seasonal temperature and precipitation. We use continuous seismic noise data recorded in a 29 broadband seismograph network in and around Mexico City to investigate Rayleigh wave group velocity structure and velocity changes. We estimate Green's functions (GF) between station pairs using seismic noise cross-correlation. An average estimate is computed for each of three five-day periods of recording. GFs are dominated by a Rayleigh pulse at low frequencies (between 0.1 and 0.2 Hz). Velocity changes are investigated through the comparison between GF's for different five-day periods. No velocity variations are observed. Station pairs separated at a distance smaller than 20 km also show some Rayleigh wave energy at higher frequencies, between 0.3 and 1.2 Hz. We repeated the analysis in a higher frequency band (up to 5 Hz) and show that again no velocity variation can be observed. In addition, we used horizontal-to-vertical spectral ratios computed for both earthquake and seismic noise records to identify possible non-linear effects during the 2017 earthquake. The results showed that significant non-linear effects during that event are to be discarded. Finally, we present preliminary results of a tomography of Rayleigh wave group velocity at the center of the array. Lateral structure variations below the geotechnical zonation are significant. Our data will be useful to constrain the structure of the volcanic deposits of the Transmexican Volcanic Belt (TVB).