Diversity and Genetic Structure of Scarlet Plume (Euphorbia fulgens), an Endemic Plant of Mexico

Euphorbia fulgens is an ornamental species cultivated in Europe and endemic to Mexico; its ecological, genetic, and evolutionary aspects are not known. The objectives of this study were to determine its distribution, describe the places it inhabits, and analyze the diversity and genetic structures of wild populations of E. fulgens. A bibliographic review of the herbarium specimens and a field evaluation were carried out to develop a potential distribution map based on a multi-criteria analysis of the climatic and topographic variables. Three populations (forty-five individuals) from pine–oak and cloud forests located in the Southern Sierra of Oaxaca were analyzed using ten microsatellite loci. The analysis was conducted using Arlequin v. 3.5, Mega v. 10, and Structure v. 2.3 programs. Eight loci were polymorphic, and a total of thirty-eight alleles were obtained. The average number of alleles per polymorphic locus was 4.6. The average heterozygosity of the three populations was high (Ho = 0.5483), and genetic differentiation between populations were low, with a high genetic flow, suggesting that it could be an ancestral population that became fragmented and was just beginning to differentiate genetically. The information generated on this restricted distribution species can be used in conservation programs pertaining to human activities that endanger the habitats where it is found.

A tale about vipers’ tails: phylogeography of black-tailed rattlesnakes

The phylogenetic relationships among black-tailed rattlesnakes remain poorly understood and some authors indicated that the diversity of this group has been underestimated and additional analyses are required to clarify the biogeographic patterns throughout its distribution in Mexico. Therefore, the aim of this study was to elucidate the phylogenetic relationships among black-tailed rattlesnakes across their range, identifying relative divergence times among the main clades and reconstructing the biogeographical history of the group. Three partial mitochondrial genes (ND4, cytb and ATPase6) and one nuclear gene (RAG1) were sequenced to infer the phylogenetic relationships, through the maximum likelihood and Bayesian inference-based methods; demographic history reconstruction was investigated through Bayesian Skyline plot analysis and the ancestral area reconstruction was carried out considering a Bayesian framework. We found strong evidence that the black-tailed rattlesnakes’ group is composed of six clades, which is in agreement with subspecies previously reported. Divergence time estimation indicated that the origin of the C. molossus group could be traced to the middle of the Miocene (~7.71 Mya). Ancestral area reconstruction indicated that early divergence events occurred in Central Mexico, probably related to the geological dynamics of the Trans-Mexican Volcanic Belt. The lineage C. m. oaxacus is the basal member of the C. molossus group. Furthermore, the combination of geological events and changes in Quaternary vegetation may have contributed to the divergence of C. molossus clades. Our results suggest several clades within C. molossus complex could be potentially recognized as separate species.

Evolutionary insights and brief review of Loxodes Ehrenberg, 1830 (Ciliophora, Karyorelictea, Loxodidae) with description of a new species from Mexico

Karyorelictids are a group of ciliates inhabiting marine and freshwater biotopes and possessing a non-dividing macronucleus. We describe a new freshwater species based on morphology and the 18S rRNA gene sequence data. Loxodes tziscaensis n. sp. can be easily distinguished from other Loxodes species by the arrangement of the nuclear apparatus and features of the buccal and somatic ciliature. The current proposed 18S rRNA phylogeny of Loxodes, including seven Loxodes species, shows two morphologically well-supported groups. Group A (L. rostrum, type species; L. vorax and L. tziscaensis n. sp.) includes species with a single nuclear group (two macronuclei and one micronucleus), in contrast to species of group B, which possess more than one nuclear group (L. striatus, L. magnus, L. kahli, L. penardi, and L. rex). We propose that the last common ancestor of Loxodes was a marine Remanella-like species possessing a single nuclear group. The division and differentiation of the micronucleus into a new macronucleus and the retention of the old macronuclei, independently of cell division, may have been two crucial processes during the evolution and diversification of Loxodes species with one nuclear group into species with multiple nuclear groups.

A Salamander tale: Relative abundance, morphometrics and microhabitat of the critically endangered Mexican salamander Pseudoeurycea robertsi (Taylor, 1939)

Roberts’ False Brook Salamander (Pseudoeurycea robertsi) is a critically endangered plethodontid salamander, endemic to the Nevado de Toluca Volcano (NTV), Mexico. Little is known about the biology and ecology of this species, including its microhabitats. Thus, this study aimed to collect basic information about P. robertsi. We sampled fourteen forested sites in the NTV; to corroborate the correct identification of the species we used genetic data, we assessed the variation in head morphometric measurements and dorsal colouration patterns amongst localities and the microhabitat features associated with P. robertsi presence. Of the four potential salamander species, P. robertsi was the most abundant (89.80%) and widely distributed (approximately within 130 km2) salamander in the NTV. We did not find significant variations in morphometry; however, we found significant differences in dorsal patterns between populations (in the number and size of segments of the dorsal stripe). The average total length for 185 adults was 89.15 mm (38.7–117.9 mm); we found seven patterns of dorsal stripe. We found 98% of P. robertsi individuals under the bark of fallen logs in Abies religiosa and A. religiosa-Pinus sp. forests, with a higher number of detected salamanders in naturally-fallen logs than in cut logs (34% vs. 10%). Thus, keeping well-preserved A. religiosa forests and retaining fallen logs is essential to P. robertsi conservation.

Detección y genotipificación de Pneumocystis jirovecii en muestras de pacientes mexicanos VIH positivos y negativos

Introduction

Pneumocystis jirovecii is an atypical fungus particularly detected in HIV-positive or transplant patients.

Objective

To detect and genotype Pneumocystis jirovecii in patient samples from two hospitals in Mexico City.

Method

Eighty-nine respiratory tract samples, corresponding to 53 patients (30 HIV-positive and 23 HIV-negative) with respiratory symptoms and to 11 healthy individuals included as negative control, were processed. DNA was extracted from the ITS region and amplified by nested polymerase chain reaction from the internal transcribed spacer, with one fragment being obtained at each round (693 and 550 bp). Genotypes and their phylogenetic relationship were determined by sequencing the 550 bp fragment.

Results

Forty-eight samples from 30 HIV-positive patients were received from a single hospital, out of which 11 (36.6 %) were positive for Pneumocystis jirovecii. No sample was positive in HIV-negative patients or healthy subjects. The most frequently detected haplotypes were Eg and Em.

Conclusions

The frequency of Pneumocystis jirovecii infection was high in the studied Mexican population. The most common genotype was different from those reported in other countries. It is necessary to address this health problem through early detection of this infection.

Genetic diversity and demography of the critically endangered Roberts' false brook salamander (Pseudoeurycea robertsi) in Central Mexico

Land use changes are threatening the maintenance of biodiversity. Genetic diversity is one of the main indicators of biological diversity and is highly important as it shapes the capability of populations to respond to environmental changes. We studied eleven populations of Pseudoeurycea robertsi, a micro-endemic and critically endangered species from the Nevado de Toluca Volcano, a mountain that is part of the Trans-Mexican Volcanic Belt, Mexico. We sequenced the mitochondrial cytochrome b gene from 71 individuals and genotyped 9 microsatellites from 150 individuals. Our results based on the cytochrome b showed two divergent lineages, with moderate levels of genetic diversity and a recently historical demographic expansion. Microsatellite-based results indicated low levels of heterozygosity for all populations and few alleles per locus, as compared with other mole salamander species. We identified two genetically differentiated subpopulations with a significant level of genetic structure. These results provide fundamental data for the development of management plans and conservation efforts for this critically endangered species.