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espanolEl declive de la diversidad de especies dulceacuicolas es un fenomeno mundial, pero es especialmente pronunciado en las regiones aridas como en el Desierto Chihuahuense de Coahuila y Durango, norte-centro de Mexico. Existen pocos datos historicos sobre la distribucion y ninguna informacion sobre extinciones de gasteropodos dulceacuicolas mexicanos. En tales casos, los datos paleontologicos pueden ser muy utiles y, a menudo, son la unica forma de documentar las distribuciones pasadas y los eventos locales de extincion u extirpacion. Este nuevo enfoque paleoecologico, llamado Paleobiologia de Conservacion, puede proporcionar perspectivas importantes para los esfuerzos de conservacion de ecosistemas analogos recientes. El sitio de estudio contiene depositos fosiles (Holoceno Tardio) del Distrito Laguna, un area pequena en Coahuila y Durango. De estos depositos fosiles describimos una nueva especie y reportamos varios registros nuevos de gasteropodos cochliopidos, hidrobidos, planorbidos y neritidos. La mayoria de estas especies y algunos generos no se conocen como fosiles de Mexico y todos ellos desaparecieron en tiempos muy recientes. En conjunto con datos de nuestros estudios paleomalacologicos anteriores, presentamos aqui un ejemplo de una extirpacion local “silenciosa” en el norte de Mexico la cual comenzo en el Holoceno Medio. Esta perdida de especies aumento rapidamente en la segunda mitad del siglo XX. De las 32 especies de caracoles dulceacuicolas presentes en el area de estudio durante el Holoceno, solo 4 (12.5%) aun existen. Al menos 24 (75.0%) de ellos desaparecieron del area en el siglo XX debido a la perdida de habitat causada por actividades antropogenicas. Nuestros resultados muestran que especialmente los hidrobidos con intervalos geograficos pequenos (especies endemicas locales) son altamente sensibles y vulnerables a tales acontecimientos de extirpacion. La extirpacion de los caracoles dulceacuicolas en el area de estudio ocurrio silenciosamente (sin registros), mientras que al mismo tiempo unos doscientos kilometros mas al norte, uno de los mayores focos de diversidad de gasteropodos en America del Norte permanecio en la cuenca de Cuatrocienegas. Las mismas amenazas que llevaron a la extirpacion local en nuestra area de estudio aun amenazan a las comunidades de caracoles dulceacuicolas del valle de Cuatrocienegas. EnglishThe decline of freshwater species diversity is a worldwide phenomenon but it is especially pronounced in arid regions such as in the Chihuahuan Desert of Coahuila and Durango, Northern Mexico. There are few historical data on the distribution but no data on extinctions of Mexican freshwater gastropods. In such cases, paleontological data can be very helpful and are often the only way to document past distributions and local extinction or extirpation events. This new paleoecological approach, called Conservation Paleobiology, can provide important perspectives in favor of conservation of recent analogue ecosystems. The study site contains subfossil (Late Holocene) deposits of the Laguna District, a small area in Coahuila and Durango. Here we describe a new species and report several new records of subfossil cochliopid, hydrobid, planorbid and neritid gastropods. Most of these species (and some genera) have not been known as fossil from Mexico and all of them disappeared in very recent times. Together with data from our former paleomalacological studies, we present herein an example of a “silent” local extirpation in northern Mexico that began in the Middle Holocene. This loss of species apparently increased rapidly in the second half of the 20th century. Of 32 species of freshwater snails present in the area of study through the Holocene only four (12.5%) are still extant. At least 24 (75.0%) of them disappeared from the area in the 20th century due to habitat loss caused by anthropogenic activities. The results show that especially hydrobiid species with small geographic ranges (local endemics) are highly sensitive and vulnerable to such extirpation events. In this study area the extirpation of freshwater snails happened silently (unrecorded) while at the same time some two hundred kilometers farther north, one of the greatest recent hotspots of gastropods diversity in North America remained in the Cuatrocienegas Basin. The same imperilment that led to local extirpation in the area of study still threatens the freshwater snail communities of the Cuatrocienegas valley.

Background The cultural importance assigned to biodiversity is a complex subject, its study has been developed from ethnobotany and ethnomicology, mainly. A new proposal to address cultural importance is from the biocultural key species. Therefore, integrating information on the knowledge and use of various biological groups, the species with the greatest cultural relevance were selected. Methods An index (BKSI: Biocultural Key Species Index) was integrated, which assesses the relevance based on general attributes associated with fauna, flora and funga. The study was carried out in the Náhuatl community called El Barco, Lolotla; in the Huastec Hidalguense region. Field work was carried out for two years (2018–2019) with 24 field trips. Percentage ethnographic method combined with snowball (10% of the population) were applied; and as the ethnographic tool multiple free listings (n = 50) were used. Results In total of 335 species associated to 537 traditional names in Spanish and indigenous language (Náhuatl) are reported, that belongs to different biological groups (fungi and plants; fish, amphibians, reptiles, birds and mammals). The biocultural relevance degree was categorized respect to the obtained value in the index (BKSI); a representative set of each biological group was selected, being those with the highest biocultural relevance. Conclusions It is proposed that these species constitute a useful tool in the application of programs that promote the conservation of diversity from a biocultural approach; they may even promote the proper use of resources or biological restoration.

The role of natural selection in the evolution of trait complexity can be characterized by testing hypothesized links between complex forms and their functions across species. Predatory venoms are composed of multiple proteins that collectively function to incapacitate prey. Venom complexity fluctuates over evolutionary timescales, with apparent increases and decreases in complexity, and yet the causes of this variation are unclear. We tested alternative hypotheses linking venom complexity and ecological sources of selection from diet in the largest clade of front-fanged venomous snakes in North America: the rattlesnakes, copperheads, cantils, and cottonmouths. We generated independent transcriptomic and proteomic measures of venom complexity and collated several natural history studies to quantify dietary variation. We then constructed genome-scale phylogenies for these snakes for comparative analyses. Strikingly, prey phylogenetic diversity was more strongly correlated to venom complexity than was overall prey species diversity, specifically implicating prey species’ divergence, rather than the number of lineages alone, in the evolution of complexity. Prey phylogenetic diversity further predicted transcriptomic complexity of three of the four largest gene families in viper venom, showing that complexity evolution is a concerted response among many independent gene families. We suggest that the phylogenetic diversity of prey measures functionally relevant divergence in the targets of venom, a claim supported by sequence diversity in the coagulation cascade targets of venom. Our results support the general concept that the diversity of species in an ecological community is more important than their overall number in determining evolutionary patterns in predator trait complexity.

Leija, E.G., Valenzuela-Ceballos, S.I., Valencia-Castro, M., Jimenez-Gonzalez, G., Castaneda-Gaytan, G., Reyes-Hernandez, H., Mendoza, M.E. 2020. Analysis of change in vegetation cover and land use in the north-central region of Mexico. The case of the lower basin of the Nazas river. Ecosistemas 29(1): 1826. https://doi.org/10.7818/ECOS.1826 Deforestation has an important impact on ecosystems, altering their capacity for providing environmental services, affecting particularly semiarid areas. The Parque Estatal Canon de Fernandez is located on the lower section of Nazas river, with 24936,6 ha and constitutes an important national and international natural protected area, because it supplies water to several cities in the north of Mexico and is recognized as a highly important habitat for aquatic birds. Nevertheless, the necessity of satisfying agricultural activities and a growing population has promoted land use and cover changes in the region. The aim of this research was to evaluate land cover and land use changes on the lower basin of Rio Nazas between 1990 and 2016. Based on visual interpretation of Landsat Tm and ETM images we generated digital data bases for land cover and land use. On 2016 the natural vegetation was composed by xeric shrub and riparian forest. In twenty six years deforestation affected 32.1% of the total area. There is a necessity to develop public policies for improving water sustainable use to preserve this xeric ecosystem.

© 2018 The US and Mexico share a common history in many areas, including language and culture. They face ecological changes due to the increased frequency and severity of droughts and rising energy demands; trends that entail economic costs for both nations and major implications for human wellbeing. We describe an ongoing effort by the Environment Working Group (EWG), created by The University of California's UC-Mexico initiative in 2015, to promote binational research, teaching, and outreach collaborations on the implications of climate change for Mexico and California. We synthesize current knowledge about the most pressing issues related to climate change in the US-Mexico border region and provide examples of cross-border discoveries and research initiatives, highlighting the need to move forward in six broad rubrics. This and similar binational cooperation efforts can lead to improved living standards, generate a collaborative mindset among participating universities, and create an international network to address urgent sustainability challenges affecting both countries.

Resumen La informacion sobre la ecologia espacial de la tortuga de bisagra es limitada, pese a ser una de las especies mas importantes para desarrollar estrategias de conservacion del valle de Cuatro Cienegas. Durante este trabajo se monitorizaron los movimientos diarios de 7 hembras de tortuga de bisagra de agosto a octubre de 2014 y 12 hembras de abril a junio del 2015, en el area de Los Gatos, dentro del valle de Cuatro Cienegas. Se estimo el ambito hogareno mediante el poligono minimo convexo y el metodo de Kernel fijo al 95%; las areas nucleo de actividad fueron estimadas mediante el Kernel fijo al 50%. La direccionalidad fue estimada mediante la prueba de Rao. El ambito hogareno vario entre ambos periodos mediante el poligono minimo convexo, mientras que el metodo de Kernel fijo al 95% no presento diferencias entre ambos periodos; lo mismo ocurrio para las areas nucleo de actividad. Por otra parte, las hembras no presentaron movimientos al azar durante todo el muestreo. Los resultados evidencian que la especie ocupa areas de mayor tamano que las planteadas en otros trabajos. La conservacion de habitat para la especie debe de contemplar la interconexion de los cuerpos de agua presentes en el sitio Los Gatos.

Species delimitation is a major topic in systematics. Species delimitation methods based on molecular data have become more common since this approach provides insights about species identification via levels of gene flow, the degree of hybridization and phylogenetic relationships. Also, combining multilocus mitochondrial and nuclear DNA leads to more reliable conclusions about species limits. Coalescent-based species delimitation methods explicitly reveal separately evolving lineages using probabilistic approaches and testing the delimitation hypotheses for several species. Within a multispecies, multilocus, coalescent framework, we were able to clarify taxonomic uncertainties within S. cyanostictus, an endangered lizard that inhabits a narrow strip of the Chihuahuan Desert in Mexico. We included, for the first time in a phylogenetic analysis, lizards from the three populations of S. cyanostictus recognized so far (East Coahuila, West Coahuila and Nuevo León). Phylogenetic analysis corroborates the hypothesis of two separately evolving lineages, i.e. the East and West Coahuila populations, as proposed in a previous study. We also found a distant phylogenetic relationship between the lizards from Nuevo León and those of East and West Coahuila. Finally, based on the species delimitation results, we propose and describe a new species of Sceloporus: S. gadsdeni sp. nov.

Rhizobacteria are central components of the plant microbiome and influence root development and function. Desciphering how rhizobacteria contribute to plant performance under adverse environments is a major research challenge. The aims of the present study were to isolate and characterize rhizobacteria from the halophilic grass Distichlis spicata and to test their possible growth promoting and salt protective properties in Arabidopsis thaliana, Cucumis sativus, and Citrullus lanatus. To determine their possible plant growth promoting properties, 38 rhizobacterial isolates were co-cultivated with Arabidopsis seedlings in vitro. Out of these, two halophilic bacteria, LBEndo1 and KBEcto4, were selected following their strong shoot and root biostimulation. 16S rRNA sequencing identified LBEndo1 as Bacillus sp. and KBEcto4 as Pseudomonas lini. Both strains improved growth under standard and saline conditions, which correlated with IAA and siderophore production, as well as phosphate solubilization. Additionally, the KBEcto4 strain expresses the ACC deaminase enzyme (acdS gene), and slightly increases auxin redistribution within Arabidopsis roots expressing an auxin-inducible gene construct. These data reveal the potential of saltgrass (Distichlis spicata) rhizobacteria to promote growth and confer salt tolerance to Arabidopsis and crop plants.

Snake venoms represent an enriched system for investigating the evolutionary processes that lead to complex and dynamic trophic adaptations. It has long been hypothesized that natural selection may drive geographic variation in venom composition, yet previous studies have lacked the population genetic context to examine these patterns. We leverage range-wide sampling of Mojave Rattlesnakes (Crotalus scutulatus) and use a combination of venom, morphological, phylogenetic, population genetic, and environmental data to characterize the striking dichotomy of neurotoxic (Type A) and hemorrhagic (Type B) venoms throughout the range of this species. We find that three of the four previously identified major lineages within C. scutulatus possess a combination of Type A, Type B, and a ‘mixed’ Type A + B venom phenotypes, and that fixation of the two main venom phenotypes occurs on a more fine geographic scale than previously appreciated. We also find that Type A + B individuals occur in regions of inferred introgression, and that this mixed phenotype is comparatively rare. Our results support strong directional local selection leading to fixation of alternative venom phenotypes on a fine geographic scale, and are inconsistent with balancing selection to maintain both phenotypes within a single population. Our comparisons to biotic and abiotic factors further indicate that venom phenotype correlates with fang morphology and climatic variables. We hypothesize that links to fang morphology may be indicative of co-evolution of venom and other trophic adaptations, and that climatic variables may be linked to prey distributions and/or physiology, which in turn impose selection pressures on snake venoms.

Los hongos micorrícicos arbusculares (HMA) de los ambientes áridos y semiáridos son importantes para el desarrollo de las plantas que crecen bajo estrés biótico y abiótico en áreas naturales o en agroecosistemas. Existe poca información sobre la diversidad temporal de los HMA en plantas perennes de ecosistemas áridos en el norte de México. En este estudiose evaluaron la colonización micorrícica y la diversidad temporal de los HMA en la rizosfera de Larrea tridentata, planta perenne de amplia distribución en el Desierto Chihuahuense. Se obtuvieron muestras de la rizosfera y de raíces de 15 plantas, en 3 fechas de muestreo del año 2015. Se encontró un total de 17 especies de HMA, distribuidas en 12 géneros y 7 familias dentro del phylum Glomeromycota. La especie más abundante fue Funneliformis geosporum. Esta especie pertenece a la familia Glomeraceae, la única que estuvo representada con varios géneros en L. tridentata. El mayor porcentaje de micorrización se presentó en febrero, con un 83,22%, en septiembre fue del 75,27% y en mayo del 65,27%. El muestreo realizado en febrero presentó el mayor número de especies (16), seguido por el de mayo (15) y el de septiembre (12). El análisis estadístico mostró diferencias significativas en el número de esporas entre los muestreos de febrero y los de mayo y septiembre. Arbuscular mycorrhizal fungi (AMF) of arid and semiarid ecosystems are important for the development of plants that grow under biotic stress in wild or in agro-ecosystems. There is little information on the temporal diversity of these organisms in perennial plants from arid ecosystems in northern Mexico. On this study, the mycorrhizal colonization and the temporal diversity of AMF in the rhizosphere of Larrea tridentata, perennial plant abundant in the Chihuahuan Desert region were explored. Samples of the rhizosphere and roots of fifteen plants in each of the three sampling dates during the 2015 year were obtained. A total of 17 species of HMA belonging to 12 genera and 7 families within the phylum Glomeromycota in all three sampling dates were found. Funneliformis geosporum was the dominant species belonging to the family Glomeraceae which possess the highest genera number on L. tridentata.The highest mycorrhization percentage was in February with 83.22, followed by September and May with 75.27 and 65.27%, respectively. A maximum of 16 AM fungal species were isolated and identified from L. tridentata rhizosphere in February, 15 species in May and 12 species in September. Statistical analysis showed significant differences between sampling dates in the spores number.

Rattlesnake venoms may be classified according to the presence/absence and relative abundance of the neurotoxic phospholipases A2s (PLA2s), such as Mojave toxin, and snake venom metalloproteinases (SVMPs). In Mexico, studies to determine venom variation in Mojave Rattlesnakes (Crotalus scutulatus scutulatus) are limited and little is known about the biological and proteolytic activities in this species. Tissue (34) and venom (29) samples were obtained from C. s. scutulatus from different locations within their distribution in Mexico. Mojave toxin detection was carried out at the genomic (by PCR) and protein (by ELISA) levels for all tissue and venom samples. Biological activity was tested on representative venoms by measuring LD50 and hemorrhagic activity. To determine the approximate amount of SVMPs, 15 venoms were separated by RP-HPLC and variation in protein profile and proteolytic activity was evaluated by SDS-PAGE (n = 28) and Hide Powder Azure proteolytic analysis (n = 27). Three types of venom were identified in Mexico which is comparable to the intraspecific venom diversity observed in the Sonoran Desert of Arizona, USA: Venom Type A ( Type II), with Mojave toxin, highly toxic, lacking hemorrhagic activity, and with scarce proteolytic activity; Type B ( Type I), without Mojave toxin, less toxic than Type A, highly hemorrhagic and proteolytic; and Type A + B, containing Mojave toxin, as toxic as venom Type A, variable in hemorrhagic activity and with intermediate proteolytic activity. We also detected a positive correlation between SVMP abundance and hemorrhagic and proteolytic activities. Although more sampling is necessary, our results suggest that venoms containing Mojave toxin and venom lacking this toxin are distributed in the northwest and southeast portions of the distribution in Mexico, respectively, while an intergradation in the middle of both zones is present Consejo Nacional de Ciencia y Tecnologia/[221343]/CONACYT/México UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto Clodomiro Picado (ICP) UCR::Vicerrectoría de Docencia::Salud::Facultad de Microbiología

Resumen. A nivel mundial los estudios de diversidad entomofaunistica en agroecosistemas van en aumento, en especial los asociados a cultivos geneticamente modificados. No obstante, en Mexico se carece de dichas evaluaciones en la mayoria de los estados productores. Se compararon las especies de insectos presentes en algodonero geneticamente modificado en cinco estados de Mexico. De los 6994 insectos obtenidos, 59 son especies distintas pertenecientes a nueve Ordenes y 40 familias. El Orden con mas insectos fue Diptera (51.5%) mientras que Coleoptera presento mayor diversidad en familias y especies (32.5 y 35%). Once especies de insectos de cinco se encontraron en todos los estados; 10 familias estuvieron presentes en uno de los estados. Coahuila presento mas familias (65%), mientras que Baja California y Chihuahua presentaron mayor diversidad (50.8%). El estado con el mayor numero de insectos fue Coahuila con el 47.7%. La familia con mas insectos fue Sciaridae con un 46.1% presente en los cinco estados. E...

The Mojave rattlesnake (Crotalus scutulatus) inhabits deserts and arid grasslands of the western United States and Mexico. Despite considerable interest in its highly toxic venom and the recognition of two subspecies, no molecular studies have characterized range-wide genetic diversity and population structure or tested species limits within C. scutulatus. We used mitochondrial DNA and thousands of nuclear loci from double-digest restriction site associated DNA sequencing to infer population genetic structure throughout the range of C. scutulatus, and to evaluate divergence times and gene flow between populations. We find strong support for several divergent mitochondrial and nuclear clades of C. scutulatus, including splits coincident with two major phylogeographic barriers: the Continental Divide and the elevational increase associated with the Central Mexican Plateau. We apply Bayesian clustering, phylogenetic inference, and coalescent-based species delimitation to our nuclear genetic data to test hypotheses of population structure. We also performed demographic analyses to test hypotheses relating to population divergence and gene flow. Collectively, our results support the existence of four distinct lineages within C. scutulatus, and genetically defined populations do not correspond with currently recognized subspecies ranges. Finally, we use approximate Bayesian computation to test hypotheses of divergence among multiple rattlesnake species groups distributed across the Continental Divide, and find evidence for co-divergence at this boundary during the mid-Pleistocene.

We compiled a list of the herpetofauna of the state of Durango, México, based on published records. The checklist contains 151 species (33 amphibians and 118 reptiles) allocated to one or more of the four major ecoregions of the state. We identified many gaps in the current knowledge of the herpetofauna of Durango, concerning the number of species and their distribution in the state, and hence, further surveys and taxonomic studies are needed to improve the completeness of this checklist.

Arbuscular mycorrhizal fungi (AMF) of arid and semiarid ecosystems are important for the development of plants that grow under biotic stress in wild or in agro-ecosystems. There is little information on the temporal diversity of these organisms in perennial plants from arid ecosystems in northern Mexico. On this study, the mycorrhizal colonization and the temporal diversity of AMF in the rhizosphere of Larrea tridentata, perennial plant abundant in the Chihuahuan Desert region were explored. Samples of the rhizosphere and roots of fifteen plants in each of the three sampling dates during the 2015 year were obtained. A total of 17 species of HMA belonging to 12 genera and 7 families within the phylum Glomeromycota in all three sampling dates were found. Funneliformis geosporum was the dominant species belonging to the family Glomeraceae which possess the highest genera number on L. tridentata. The highest mycorrhization percentage was in February with 83.22, followed by September and May with 75.27 and 65.27%, respectively. A maximum of 16 AM fungal species were isolated and identified from L. tridentata rhizosphere in February, 15 species in May and 12 species in September. Statistical analysis showed significant differences between sampling dates in the spores number.

We describe discrete variation in throat color, an important sexual signal, in males of 2 populations of the mesquite lizard (Sceloporus grammicus). At one locality, males exhibit orange, yellow, and blue morphs; whereas at the other, males exhibit orange, yellow, and white morphs. We performed dyadic agonistic behavior trials in both populations and found that variation in throat color is associated with variation in aggression level. However, the association between color and behavior is not the same between these 2 populations. The association between color and behavior in the mesquite lizard is also not consistent with some of the associations documented in closely related species with variable throat color. Our findings suggest that although the tendency for discrete color variation to signal alternative reproductive tactics is phylogenetically widespread, both the color signals and the behaviors associated with them may change rapidly over evolutionary time.

Color polymorphic sexual signals are often associated with alternative reproductive behaviors within populations, and the number, frequency, or type of morphs present often vary among populations. When these differences lead to assortative mating by population, the study of such polymorphic taxa may shed light on speciation mechanisms. We studied two populations of a lizard with polymorphic throat color, an important sexual signal. Males in one population exhibit orange, yellow, or blue throats; whereas males in the other exhibit orange, yellow, or white throats. We assessed female behavior when choosing between allopatric and sympatric males. We asked whether females discriminated more when the allopatric male was of an unfamiliar morph than when the allopatric male was similar in coloration to the sympatric male. We found that female rejection of allopatric males relative to sympatric males was more pronounced when males in a pair were more different in throat color. Our findings may help illuminate how behavioral responses to color morph differences between populations with polymorphic sexual signals contribute to reproductive isolation.

Between 2009 and 2011, 21 individuals of X. extorris were collected in the area of the Sierra of Jimulco, at Torreón, Coahuila. This finding represents the first record for the state of Coahuila. The potential ecological niche of X. extorris at this mountain was calculated using the software MaxEnt. We also revised the stomach content of 11 individuals. The dietary habits suggest that X. extorris forages near to its preferred microhabitats eating secretive species like spiders, pseudoscorpions and beetles.

Uma paraphygas es una lagartija endémica y en peligro de extinción debido a su distribución muy restringida, escasa variabilidad genética y a la elevada presión ecológica y ambiental a la que esta sujeta. Se evaluaron estacionalmente dos poblaciones de U. paraphygas en dos áreas de 2 ha cada una en la Reserva de la Biosfera de Mapimí, Durango. El trabajo de campo se desarrolló desde el otoño de 1997 hasta el verano de 1999. El estudio se hizo empleando una captura y varias recapturas por medio de la técnica de la lazada. Los organismos capturados se marcaron permanentemente y se obtuvieron los datos pertinentes. Este estudio da a conocer la estructura y dinámica de dos poblaciones de este lacertilio para determinar su estatus actual. Se estimó la densidad, biomasa, estructura de edades, tasas de crecimiento, sobrevivencia, tasa de reemplazamiento poblacional y el tiempo generacional de esta especie. La densidad y biomasa promedio anual se modificaron en relación con la precipitación acumulada. No hubo diferencias significativas para los factores de densidad y biomasa entre las dos poblaciones estudiadas. El mayor porcentaje de la población lo conformaron las hembras adultas seguidas de los machos adultos. La mayor tasa de crecimiento diario la presentaron las crías de ambos sexos, la cual a su vez disminuye gradualmente conforme tienen más edad. La sobrevivencia anual para la especie fue de 0.20. Sin embargo, la menor sobrevivencia fue para las hembras subadultas, y la mayor fue para los machos subadultos. Se presume que la sobrevivencia de las diferentes clases de edad de esta especie está relacionada con factores de competencia intra-específica. La tasa de reemplazamiento poblacional indicó una estabilidad aparente para las dos poblaciones y el tiempo generacional fue de 1.26 años.