Lázaro Guevara

Molecular systematics of small-eared shrews (Soricomorpha, Mammalia) within Cryptotis mexicanus species group from Mesoamérica

Cryptotis mexicanus species group is the most diverse group of Cryptotis shrews in the Mesoamerican highlands (ca.13 species). In México, eight endemic species occurs and several taxa are endangered. The species’ limits and phylogenetic relationships of these taxa have been recently examined using morphology; nevertheless, little is known about phylogenetic relationships among Cryptotis species at the molecular level. Therefore, our research included a mitochondrial DNA marker as a source of additional information to corroborate taxonomic identification and produce a phylogenetic hypothesis of the C. mexicanus species group. We were particularly interested in the status of Cryptotis magnus, a species considered as relict on the basis of primitive characters. Based on the analyses of genetic sequences of a high number of Cryptotis species, outgroups, and phylogenetic analyses of parsimony and Bayesian inference, we confirmed that Cryptotis genus consists of different lineages that represent species groups. A detailed analysis suggests that C. magnus is a species that shares an evolutionary history with the C. mexicanus species group because it is imbedded within this group. In particular, our data strongly support that C. magnus and Cryptotis phillipsii are sister groups, a pair of species that inhabit allopatrically Southern México.

Impact of Moderate Heat, Carvacrol, and Thymol Treatments on the Viability, Injury, and Stress Response of Listeria monocytogenes.

The microbial safety and stability of minimally processed foods are based on the application of combined preservative factors. Since microorganisms are able to develop adaptive networks to survive under conditions of stress, food safety may be affected, and therefore understanding of stress adaptive mechanisms plays a key role in designing safe food processing conditions. In the present study, the viability and the sublethal injury of Listeria monocytogenes exposed to moderate heat (55°C) and/or essential oil compounds (carvacrol and thymol, 0.3 mM) treatments were studied. Synergistic effects were obtained when combining mild heat (55°C) with one or both essential oil compounds, leading to inactivation kinetics values three to four times lower than when using heat alone. All the treatments applied caused some injury in the population. The injury levels ranged from around 20% of the surviving population under the mildest conditions to more than 99.99% under the most stringent conditions. Protein extracts of cells exposed to these treatments were analysed by two-dimensional gel electrophoresis. The results obtained revealed that stressed cells exhibited differential protein expression to control cells. The proteins upregulated under these stressing conditions were implicated, among other functions, in stress response, metabolism, and protein refolding.

A new species of small-eared shrew (Mammalia, Eulipotyphla, Cryptotis) from the Lacandona rain forest, Mexico

Abstract The diversity and distribution of mammals in the American tropics remain incompletely known. We describe a new species of small-eared shrew (Soricidae, Cryptotis) from the Lacandona rain forest, Chiapas, southern Mexico. The new species is distinguished from other species of Cryptotis on the basis of a unique combination of pelage coloration, size, dental, cranial, postcranial, and external characters, and genetic distances. It appears most closely related to species in the Cryptotis nigrescens species group, which occurs from southern Mexico to montane regions of Colombia. This discovery is particularly remarkable because the new species is from a low-elevation habitat (approximately 90 m), whereas most shrews in the region are restricted to higher elevations, typically > 1,000 m. The only known locality for the new shrew is in one of the last areas in southern Mexico where relatively undisturbed tropical vegetation is still found. The type locality is protected by the Mexican government as part of the Yaxchilán Archaeological Site on the border between Mexico and Guatemala. Resumen La diversidad y distribución de las musarañas en el trópico americano son, aún, parcialmente conocidas. Aquí presentamos la descripción de una nueva especie de musaraña de orejas cortas (Soricidae, Cryptotis) con base en dos ejemplares de museo colectados en la selva Lacandona, Chiapas, en el sur de Mexico. La nueva especie se puede distinguir de otras especies del género por una combinación de características que incluye la coloración del pelaje, el tamaño, caracteres dentales, craneales, postcraneales y distancias genéticas. El nuevo taxón podría estar relacionado al grupo de especies Cryptotis nigrescens, cuyas especies habitan desde el sur de Mexico hasta las montañas de Colombia. El descubrimiento es particularmente notable ya que la especie nueva habita en tierras bajas (cerca de los 90 m), mientras que la mayoría de las especies en la región están restringidas a elevaciones mayores a los 1000 m. La única localidad para la nueva especie descrita se ubica en la selva Lacandona, una de las últimas áreas al sur de Mexico con vegetación tropical que permanecen sin alterar. La localidad tipo se encuentra en una zona protegida por el gobierno federal mexicano, ya que es parte de la Zona Arqueológica Yaxchilán, ubicada en la frontera entre Mexico y Guatemala.

Noteworthy records of an endemic shrew from Mexico (Mammalia, Soricomorpha, Cryptotis griseoventris), with comments on taxonomy

Abstract The broad-clawed shrew Cryptotis griseoventris Jackson, 1933, is poorly known ecologically and behaviorally because distributional records are relatively scarce. Here, we provide new records based on 11 specimens deposited in mammal collections, more than 50 years since the last confirmed record. Historical records and specimens are reexamined and discussed. We suggest that C. griseoventris occurs in a small area (<5000 km2) above 2100 m dominated by pine oak and cloud forests in Los Altos de Chiapas, Mexico, and is likely endangered due to habitat deforestation. We also describe the humerus, a useful structure to delimit species and reconstruct phylogenetic relationships within the genus Cryptotis. The morphology of their humerus corroborates its taxonomic relatedness with the Cryptotis goldmani species group and yields a more comprehensive knowledge of the ecology and evolution within this group.

Patterns of morphological and ecological similarities of small-eared shrews (Soricidae, Cryptotis) in tropical montane cloud forests from Mesoamerica

It has been proposed that high morphological similarity between closely related species of small-eared shrews resulted from a recent divergence and intermittent population connectivity, presumably due to Pleistocene climatic fluctuations and associated changes in forest habitat distribution. Here we examined the morphological variation of two sister species of small-eared shrews inhabiting cloud forests from Mexico, Cryptotis obscurus and C. mexicanus. We then used ecological niche modelling to provide compelling evidence for current environmental barriers for population connectivity, and for detecting divergent ecological niches between candidate species. Our results indicated that the species boundaries in this clade should be subject to change. High morphological similarity suggested that populations of C. obscurus and C. mexicanus located west of the Isthmus of Tehuantepec, a major geographic barrier for montane species, are conspecific. Niche divergence between these two putative species was not supported indicating niche conservatism across the evolutionary history of these small-eared shrews. In addition, several barriers seem to play a main role for current lineage divergence between populations within this clade. The population located east of the Isthmus, previously referred to C. mexicanus, might prove to represent a new species based on morphological distinction and current geographic isolation. We have highlighted that estimating species’ potential distributions provides insights to evaluating the effect of geographic barriers on lineage divergence and making stronger inferences when delimiting species.

Variación entre Modelos de Circulación Global para reconstrucciones de distribuciones geográficas del Último Máximo Glacial: relevancia para la filogeografía

Delgado L.A. 2018. Landscape Heterogeneity and tree species diversity in a tropical forest. Development and validation of a methodological proposal. Ecosistemas 27(1): 105-115. Doi.: 10.7818/ECOS.1475 Many landscapes exist as unstable spatial-temporal mosaics where changes in patterns of biodiversity are affected by nature processes and the dynamic interaction between social and ecological factors. It is a consequence of the natural dynamics of socio-economic systems that regulate man-made tropical forests. However, a significant proportion of studies have made generalizations about the relative values of biodiversity, without taking into account the high levels of internal heterogeneity in the biophysical properties and land uses of each site. The purpose of this study is to propose and validate a methodology to delimit the heterogeneity of the landscape based on criteria that integrate the coupling of human-ecological systems such as: space-time dynamics of deforestation and fragmentation; complexity of the landscape structure; current and historical land use and biophysical variability. For this, the use of satellite images, landscape metrics, field work, documentary review and multivariate analysis were combined. The proposed methodology is intended to help guide the empirical delimitation of landscape heterogeneity as a prerequisite for the selection of similar landscapes and forest patches in studies of the diversity of tree species, in order to provide an opportunity to control the possible difficulties caused by variability in the proportion of forests, landscape configuration and successional states, in estimating its effects on forest richness and floristic composition.

Systematics of the broad-nosed bats, Platyrrhinus umbratus (Lyon, 1902) and P. nigellus (Gardner and Carter, 1972) (Chiroptera: Phyllostomidae), based on genetic, morphometric, and ecological niche analyses

ABSTRACT Platyrrhinus is a genus of leaf-nosed frugivorous bats that are endemic to the Neotropics. P. umbratus occurs in the Andean and costal mountain systems of Venezuela and Colombia. P. nigellus occurs along the Andes from Venezuela to Bolivia. Both species are medium-sized members of the genus possessing confusing taxonomic histories that have never intersected. Four of the 21 recognized species of Platyrrhinus, among them P. umbratus, do not have their taxonomic identification confirmed by molecular analyses. We provide the first genetic data (Cyt-b and ND2 sequences) for the species. Phylogenetic analyses including the new genetic data lead to the conclusion that P. umbratus and P. nigellus are conspecific. Through the use of Principal Components Analysis (PCA) and Ecological Niche Modeling (ENM), we confirm that P. umbratus and P. nigellus share high morphometric and environmental similarities. Based on such integrative approach, we regard P. nigellus as a junior synonym of P. umbratus. We provide an emended diagnosis of P. umbratus (subsuming P. nigellus) and draw morphological comparisons with other species of the genus with which it is sympatric. The conservation status of P. umbratus needs to be determined. The high rate of habitat destruction in the tropical Andes may soon cause P. umbratus to be reassigned to the Near-Threatened (NT) category of the International Union for Conservation of Nature (IUCN).

The thermal niche of Neotropical nectar‐feeding bats: Its evolution and application to predict responses to global warming

Abstract The thermal niche of a species is one of the main determinants of its ecology and biogeography. In this study, we determined the thermal niche of 23 species of Neotropical nectar‐feeding bats of the subfamily Glossophaginae (Chiroptera, Phyllostomidae). We calculated their thermal niches using temperature data obtained from collection records, by generating a distribution curve of the maximum and minimum temperatures per locality, and using the inflection points of the temperature distributions to estimate the species optimal (STZ) and suboptimal (SRZ) zones of the thermal niche. Additionally, by mapping the values of the STZ and SRZ on a phylogeny of the group, we generated a hypothesis of the evolution of the thermal niches of this clade of nectar‐feeding bats. Finally, we used the characteristics of their thermal niches to predict the responses of these organisms to climate change. We found a large variation in the width and limits of the thermal niches of nectar‐feeding bats. Additionally, while the upper limits of the thermal niches varied little among species, their lower limits differ wildly. The ancestral reconstruction of the thermal niche indicated that this group of Neotropical bats evolved under cooler temperatures. The two clades inside the Glossophaginae differ in the evolution of their thermal niches, with most members of the clade Choeronycterines evolving “colder” thermal niches, while the majority of the species in the clade Glossophagines evolving “warmer” thermal niches. By comparing thermal niches with climate change models, we found that all species could be affected by an increase of 1°C in temperature at the end of this century. This suggests that even nocturnal species could suffer important physiological costs from global warming. Our study highlights the value of scientific collections to obtain ecologically significant physiological data for a large number of species.