Mexico Environment Research Articles

Activity patterns in a feline assemblage in south-west Mexico, and their relationship with prey species

AbstractSeveral species of neotropical felines are morphologically and ecologically similar, and are sympatric along large areas of their distribution. This requires mechanisms to allow their coexistence, such as temporal segregation of their activities. The aim of this study was to evaluate the relation between activity patterns of felines and their prey using camera trapping data and their seasonal variation in two tropical environments in south-western Mexico. ExceptingPuma concolor, activity patterns for each feline species did not differ significantly between seasons nor between vegetation types. Activity patterns did not differ significantly between species of similar size: mid-sized species had high activity pattern overlaps in the medium forest while large-sized species overlapped to a lesser extent in the cloud forest.Leopardus wiediidiffered from large-sized predators in its activity patterns. We recorded a relatively high temporal overlap between felines and their main prey species, particularly in the periods of maximum activity. We found no evidence of temporal segregation between the felines of the Sierra Norte region of Oaxaca and we suggest their coexistence is mediated by the selection of prey with different activity patterns.

Effect of Rejuvenation Pruning on the Vegetative Growth and Productivity in Olive under Hot and Arid Environment of Mexico

Currently in Mexico there are few studies on agronomic management in olive production. The objective of this experiment was to evaluate three rejuvenation pruning intensities (25, 33, 50% and Control “traditional pruning”) in olive tree cv Manzanilla under hot and arid environment of Mexico. The experiment was carried out during four consecutive years from 2016 to 2019 at National Research Institute for Forestry, Agriculture and Livestock (INIFAP) in the Experimental Station Coast of Hermosillo, Sonora, Mexico. The experiment was carried out on 25-year-old olive orchard cultivar Manzanilla, planted at distance of 8 x 8 m (156 trees ha-1) and under surface irrigation. The variables evaluated were: vegetative parameters (wood weight, canopy diameter and plant height), olive yield and fruit characteristics (fruit weight and pulp-pit ratio). The experiment was organized as a randomized complete block design with five replications. Our results showed statistical differences (P<0.01) in all parameters evaluated with exception of fruit characteristics. During the rejuvenation process of the olive tree the treatment that obtained the higher yield was pruning with 25% intensity removing one trunk per year, which obtained an average yield in four years of 39.2 kg tree-1, while in the control treatment the yield was of 34.1 kg tree-1. Thus, it is possible to rejuvenate an olive orchard in four years without to affect olive yield.

How much can Mexican healthcare providers learn about breastfeeding through a semi-virtual training? A propensity score matching analysis

BackgroundMexico has shown a worrisome decrease in breastfeeding indicators, especially in the lowest socioeconomic level. Improving breastfeeding protection, promotion, and support services through workforce development is a key area of intervention. The objective of this study is to assess the influence on breastfeeding knowledge and abilities of a semi-virtual training for primary healthcare providers assisting beneficiaries of PROSPERA in Mexico, which is one of the largest conditional cash-transfer programs in the world.MethodsTwo independent cross-sectional samples of healthcare providers were drawn at baseline and post-intervention in three states of Mexico. Baseline data were collected among primary physicians, registered nurses and nurse technicians (i.e. unit of analysis) on July 2016 (n = 529) and post-training between March and April 2017 (n = 211). A 19-item telephone questionnaire assessed providers’ general knowledge about breastfeeding, breastfeeding benefits and clinical aspects of breastfeeding, clinical ability to solve problems and abilities to overcome breastfeeding challenges. The effects of the training were assessed through a propensity score matching (PSM) stratified by types of providers (i.e. physicians, registered nurses, nurse technicians).ResultsThe PSM analysis showed significant improvements among all providers in the general knowledge about breastfeeding (around 20 percentage points [pp]) and knowledge about breastfeeding benefits (approximately 50 pp). In addition, physicians improved their knowledge about clinical aspects of breastfeeding (7 pp), while registered nurses improved in their ability to solve breastfeeding problems (14 pp) and in helping mothers overcome breastfeeding challenges (12 pp).ConclusionsPromoting a breastfeeding enabling environment in Mexico to improve breastfeeding rates will require improving the knowledge and skills of healthcare providers. While a semi-virtual training showed large improvements in knowledge, developing skills among providers may require a more intensive approach.

Host selection of Aedes aegypti and Culex quinquefasciatus females in a semi-desert environment in Northern Mexico

Transmission of arboviral diseases such as those caused by dengue, chikungunya and West Nile viruses involves hematophagous insects. Arbovirus transmission is a complex process in which host selection plays an important role that determines the contact rates between vulnerable hosts and infective vectors. This paper describes host selection of Aedes aegypti (Linnaeus) (Diptera: Culicidae) and Culex quinquefasciatus in suburban neighborhood houses located in the semi-desert environment of northern Mexico. All bloodmeal analyses were completed in engorged females collected by means of BG-GAT (BIOGENTS ®) traps and blood identification was made through PCR analysis using cytochrome b as reference gene. The results show that Ae. aegypti is feeding primarily on birds from the Galliformes and Columbiformes orders. On the other hand, Culex quinquefasciatus exhibits the same behavior as Ae. aegypti, selecting Galliformes as the main blood source group but exhibits different behavior regarding humans, feeding preferentially on humans over non-human mammals. Regarding resource utilization, Ae. aegypti had a broader niche (0.79) than Cx. quinquefasciatus (0.46). Pianka´s niche overlap index (0.79) showed that both species share many common hosts. Host selection for the mosquito species analyzed were found to be atypical from what is reported in the literature, which could have an impact on the vectorial capacity of the mosquitoes within the study area.

Phylogenetic and phenotypic filtering in hummingbirds from urban environments in Central Mexico

Cities act as biological filters on native biodiversity, selecting for traits allowing species to use urban resources, which may modify the phylogenetic structure and composition of biotic assemblages. Although many studies about urban filtering have included bird communities, few have focused on diverse and specialized groups, such as hummingbirds. Here, we investigate if: (1) the urbanization process may have modified the phylogenetic and phenotypic structure of regional hummingbird assemblages in five cities along the Trans-Mexican Volcanic Belt in central Mexico, and (2) hummingbird species in urban environments have been filtered through the selection of particular morphological traits. We measured eight morphological traits related to the ability of hummingbird species to use resources, three of which (wing chord, culmen and bill curvature) were retained for phenotypic analyses. We estimated phylogenetic (MPD, mean pairwise distance, and MNTD, mean nearest taxon distance) and phenotypic structure values (pMPD and pMNTD) in regional and urban hummingbird assemblages, which allowed us to assess significant phylogenetic structure and phenotypic similarity among coexisting species, respectively. We also calculated phylogenetic signal to determine if traits are labile or conserved. We performed generalized linear mixed-effect models and a classification and regression tree analysis to determine which traits explained species’ presence in urban environments. Our results showed that urbanization modified the phylogenetic structure from a random pattern in regional assemblages towards more overdispersed values in urban assemblages, while phenotypic structure values changed either towards clustering or overdispersion in the different cities. Regression tree analyses showed that traits related to body-size and bill culmen may influence the presence of different hummingbird species in cities. Our results show that the urbanization process may change the phylogenetic and phenotypic structure of hummingbird assemblages, favoring species with generalist morphologies (intermediate body-sizes and relatively longer bills).

An Evaluation of Kernel Zinc in Hybrids of Elite Quality Protein Maize (QPM) and Non-QPM Inbred Lines Adapted to the Tropics Based on a Mating Design

Genetic improvement of maize with elevated levels of zinc (Zn) can reduce Zn deficiency among populations who rely on maize as a staple. Inbred lines of quality protein maize (QPM) and non-QPM with elevated Zn levels in the kernel have been identified. However, information about the optimal strategy to utilize the germplasm in breeding for high-Zn concentration is lacking. As a preliminary step, this study was conducted to ascertain the potential of QPM, non-QPM, or a combination of QPM and non-QPM hybrids for attaining desirable Zn concentration. Twenty elite inbreds, 10 QPM and 10 non-QPM, were crossed according to a modified mating design to generate hybrids, which were evaluated in four environments in Mexico during 2015 and 2016 in order to evaluate their merits as parents of hybrids. The highest mean values of Zn were observed when high-Zn QPM lines were crossed with high-Zn non-QPM lines. Hybrids with high Zn and grain yield were identified. General combining ability (GCA) effects for Zn concentration were more preponderant than specific combining ability (SCA) effects, suggesting the importance of additive gene action for the inheritance of Zn.

Wealth inequality, social stratification, and the built environment in Late Prehispanic Highland Mexico: A comparative analysis with special emphasis on Tlaxcallan

Beginning in the last century, archaeologists became interested in the development of social complexity. Since that time, the basic concept of states and complex societies has been defined by rigid social stratification, extreme wealth inequality, and political centralization. However, recently, landscape approaches, household archaeology, city-states, and “alternative pathways to complexity” have begun to make inroads in developing a more robust approach to premodern states. Specifically, anthropological theory has advanced significantly with the incorporation of Collective Action, yet theoretical and empirically based studies of wealth inequality, social stratification, and the built environment in the archaeological literature are still limited. Therefore, in this paper, we seek to test the traditional definition of the state and complex societies using cases from Middle-Late Postclassic Highland Mexico (Central Mexico and Oaxaca), especially the case of Tlaxcallan. Using a comparative approach, we find that a stark division between public and private architecture and a compression of wealth inequality and social stratification, especially the absence of palaces, and a comparatively high degree of political centralization, marked the Tlaxcaltecan state. Accordingly, we conclude that theoretical approaches in archaeology must incorporate Collective Action Theory or other comparable approaches to effectively deal with real empirical variation in the past.

Evaluation of temperature-based solar radiation models and their impact on penman-monteith reference evapotranspiration in a semiarid climate

Solar radiation is one of the most important climatic parameters that is involved in different environmental, hydrological, agricultural applications while not always measured at all weather stations due to the high equipment and maintenance cost. The objectives of this study were to evaluate the performance and accuracy of twenty temperature based solar radiation models at five weather stations (Alcalde, Fabian Garcia, Farmington, Leyendecker and Tucumcari) in New Mexico and to evaluate the impact of solar radiation prediction on the Penman-Monteith grass reference evapotranspiration (ETo) for the global period of 2009-2017. New constants of each model at each weather station were retrieved using the optimization procedure Solver in Excel that maximizes the Kling-Gupta Efficiency (KGE). The root mean squared error (RMSE), mean absolute error (MAE), mean bias error (MBE) and the Nash-Sutcliffe model efficiency coefficient (NSE) were used for model performance evaluation. The results showed that the Hargreaves and Samani (1982), improved by Allen 1995, Bristow-Campbell (1984), Hunt et al. (1998), Fan et al. (2018), Hassan et al. (2016), Samani (2000); Nage et al. (2018) 2 and the Richardson et al (2018) models were the most accurate and the best performing ones across all five research sites. The EL-Sabaii, Ert Yal and Clemence models showed the poorest performance at all five stations. The evaluation of the impact of the predicted solar radiation on the Penman-Monteith ETo showed that predicted solar radiation had non-significant effect of the daily ETo with a regression slope varying from 0.978 to 1.022, RMSE from 0.24 to 0.48 mm/day, MAE from 0.15 to 0.31 mm/day and MBE from -0.03 to 0.09 mm/day. All solar radiation models showed best performance at Farmington and Tucumcari while they registered the poorest performance at Alcalde. The Student T-test revealed non-significant differences between the daily ETo using the measured solar radiation data set and the predicted solar radiation by each of the twenty solar radiation models at each weather station. The new models developed in this study could be used to estimate daily solar radiation across the semiarid environment of New Mexico for satisfactory estimation of ETo.

Sexual dimorphism in size and shape among populations of the lizard Sceloporus variabilis (Squamata: Phrynosomatidae)

Sexual dimorphism in lizards is determined by ecological and environmental factors. Broadly distributed species may show variation in patterns of sexual dimorphism toward either sex, as well as exhibiting variation in morphological dimensions. In the present study, sexual dimorphism in size and shape attributes was evaluated in three populations of the lizard Sceloporus variabilis from different environments in Mexico. We evaluated the size attributes of 10 morphological variables: snout-vent length (SVL), tibia length (TL), femur length (FeL), forearm length (FoL), interaxial distance (ID), head length (HL), head width (HW), head height (HH), jaw length (JL), and jaw width (JW). We also evaluated the attributes of shape (relative dimensions of the 10 morphological variables). In the size attribute, sexual dimorphism was found, with males being larger than females. In the case of shape, sexual dimorphism was found, with the females being larger in relative dimensions of ID and JW. Also, the males showed larger relative dimensions in TL, FeL and FoL. Differences were found between populations in the dimension of the variables analyzed in each sex. The pattern in size can be explained by sexual selection, where the males of each population maintain larger dimensions to compete for territory and access to females. In shape, females can be favored if they have larger relative ID and JW, as it promotes maintenance of clutch sizes, and use of microhabitats and different consumption of prey types than males. In the case of males, relative dimensions of TL, FeL and FoL may be functioning as important traits for escape from predators. The present study shows the importance of incorporating size and shape variables into analyses of sexual dimorphism among populations of a single species with a wide distribution. These types of studies help to identify the causes that promote sexual dimorphism, as well as the degree of difference among populations that inhabit different environments.

Four Consistent Loci Confer Adult Plant Resistance to Leaf Rust in the Durum Wheat Lines Heller#1 and Dunkler.

The durum wheat lines Heller#1 and Dunkler from the International Maize and Wheat Improvement Center Global Wheat Program showed moderate and stable adult plant resistance to leaf rust under high disease pressure over field environments in northwestern Mexico. Leaf rust phenotyping was performed on two recombinant inbred line (RIL) populations derived from crosses of Heller#1 and Dunkler with the susceptible parent Atred#2, conducted under artificially induced Puccinia triticina epidemics in 2013, 2014, 2015, and 2016. The Atred#2 × Heller#1 and Atred#2 × Dunkler populations were genotyped by single nucleotide polymorphism (SNP) platforms and diversity arrays technology markers, respectively. Four leaf rust resistance quantitative trait loci were detected simultaneously in the two RIL populations: Lr46, QLr.cim-2BC, QLr.cim-5BL, and QLr.cim-6BL based on phenotypic data across all four crop seasons. They explained 11.7 to 46.8%, 7.2 to 26.1%, 8.4 to 24.1%, and 12.4 to 28.5%, respectively, of the phenotypic variation for leaf rust resistance in Atred#2 × Heller#1 and 16.3 to 56.6%, 6.7 to 15.7%, 4.1 to 10.1%, and 5.1 to 20.2% of the variation in the Atred#2 × Dunkler population. Only the resistance allele of QLr.cim-2BC was from the susceptible parent Atred#2, and resistance alleles at other loci came from the resistant parents Heller#1 and Dunkler. The SNP markers closely linked to Lr46 and QLr.cim-2BC were converted to kompetitive allele specific PCR markers for use in marker-assisted selection to improve leaf rust resistance through crosses with Heller#1 and Dunkler sources.

Insectivorous bats as biomonitor of metal exposure in the megalopolis of Mexico and rural environments in Central Mexico

The Megalopolis of Mexico is one of the largest cities in the world and presents substantial problems of metal pollution. Insectivorous bats that inhabit this city are potentially exposed to metals and could therefore serve as a good biomonitor. We collected 70 adult male individuals of Tadarida brasiliensis (Chiroptera: Molossidae) from two areas inside the Megalopolis (Cuautitlán and Xochimilco) and two rural environments in Central Mexico (Tequixquiac and Tlalcozotitlán). We analyzed livers to determine the total concentrations of ten metals by the ICP-MS technique, compared concentrations among study sites to provide evidence of metal exposure, and explored the associations between metals and their accumulation patterns in bats. The hepatic metal concentrations we recorded were generally consistent with those of similar studies in insectivorous bats. Higher concentrations of Cu and Zn in Cuautitlán and Xochimilco bats were associated with vehicular traffic. Higher concentrations of V, Cr, and Co in Tequixquiac bats and Cd in Tlalcozotitlán bats were linked with industrial, agricultural, or sewage sources. Variations in Fe and Mn concentrations were related to geogenic sources or local conditions. Similar Ni and Pb concentrations were linked with strong homeostatic controls or historical pollution. Accumulation patterns showed that all urban bats belonged to a single population with similar degrees of metal exposure, while rural bats belonged to two different populations exposed to different metals. Our results highlight the need to monitor the emissions generated by particular sources in each study site.

Evaluation of U.S. inbred lines with expired plant variety protection for mid-altitude tropical maize breeding

Maize (Zea mays L.) inbred lines with expired U.S. Plant Variety Protection Act certificates (ex-PVPA) can be an important source of favorable alleles to improve grain yield, root and stalk lodging, drydown, plant architecture, and reduced time to maturity of tropical hybrids. Understanding the heterotic patterns and combining ability of ex-PVPA lines with tropical lines is necessary to design effective breeding strategies using this germplasm. This study evaluated 10 Iowa Stiff Stalk Synthetic (BSSS) and 11 Non-Stiff Stalk Synthetic (NSSS) inbred lines in hybrid combinations with tropical mid-altitude testers in five mid-altitude environments (900–2000 masl) in Mexico and identified six hybrids with grain yield equal or superior to that of the check hybrids. Two NSSS inbred lines: PHR03 and PHN82 had significant (P < 0.01) and positive general combining ability (GCA) effects with inbred lines from CIMMYT’s Tuxpeno heterotic group. Similarly, the BSSS line PHG39 had a significant positive GCA effect (P < 0.05) with non-Tuxpeno lines. The lines PHN82 and PHK29 had positive GCA effects (P < 0.01) under drought stress and could be used as sources of drought tolerance in CIMMYT breeding programs. The mid-altitude lines CML537 and CML539 had positive GCA effects (1.45 and 0.69 t/ha, respectively; P < 0.01) with NSSS lines whereas hybrids of CML384 with BSSS lines yielded 0.64 t/ha (P < 0.01) more than the average of the testcrosses. These results showed that U.S. ex-PVPA lines can increase grain yield of CIMMYT’s tropical mid-altitude hybrids.

Graptopetalum sinaloensis (Crassulaceae), una nueva especie de Sinaloa, México

Antecedentes y Objetivos: El género Graptopetalum (Crassulaceae) incluye cerca de 20 especies de herbáceas rosetoides, con tallos ramificados o acaules, que se desarrollan en ambientes semiáridos y poco accesibles (montañas o barrancas) de México y Arizona. Como parte del trabajo continuo de los autores para documentar la flora de Sinaloa, en el presente artículo, se reporta una novedad taxonómica del género Graptopetalum. Métodos: En junio de 2013, en el municipio Culiacán, Sinaloa, México, se encontró una pequeña población de plantas del género Graptopetalum con inflorescencias secas, de la cual se colectaron algunos individuos para cultivar; florecieron en marzo. Especímenes con flor se colectaron en campo en la misma localidad en febrero de 2014. Al comparar el material de campo y el cultivado con material de herbario, literatura y cultivo de otras especies del género, se determinó que se trataba de una especie nueva para la ciencia. Resultados clave: Se describe el nuevo taxón Graptopetalum sinaloensis de la sección Graptopetalum, se discuten diferencias y similitudes con las especies más cercanas y se proporciona una clave dicotómica nueva y actualizada para las ocho especies de esta sección. Conclusiones: Graptopetalum sinaloensis es endémica del centro-sur de Sinaloa, México. Crece sobre paredes rocosas de arroyos y pie de cerros muy localizados, en poblaciones pequeñas y áreas reducidas de entre 5 y 10 m2. Se diferencia fácilmente de las otras especies de la sección Graptopetalum de Sinaloa por su flor pentámera, ya que G. rusbyi presenta 6-7, y por su inflorescencia en panícula porque G. occidentale presenta una cima. Además, la distribución geográfica no se traslapa con ninguna de ellas.

An analysis of stakeholder networks to support the breastfeeding scale-up environment in Mexico.

Little information exists on how to garner political commitment to strengthen large-scale breastfeeding policies and programmes by targeting key decision makers. The present study aims to map and describe the influence of stakeholders involved in breastfeeding policy and programming and identify opportunities to strengthen the breastfeeding-friendly environment in Mexico. A total of nine key informants from seventeen stakeholder organisations were selected based on their in-depth knowledge of the breastfeeding environment in Mexico and were individually interviewed using Net-Map methodology. This participatory interview technique combines stakeholder mapping, social network analysis and influence mapping to identify relevant stakeholders. Participants identified a total of fifty-five stakeholders shaping breastfeeding programmes and policies through four domains of influence: commands (n 32 stakeholders), dissemination (n 40), funding (n 35) and technical assistance (n 37). The Federal Ministry of Health emerged as the most influential stakeholder of breastfeeding policy and programming decisions in Mexico among all domains of influence. The Ministry of Finance and Public Credit as well as the National Institute of Public Health were identified as additional key stakeholders providing funding and technical assistance to the Federal Ministry of Health, respectively. Engaging identified key stakeholders can generate a multisectoral commitment to breastfeeding and strengthen the breastfeeding-friendly environment in Mexico.

N2O emission factors from a wastewater irrigated land in a semiarid environment in Mexico

Irrigation with wastewater is an increasing practice around the world triggered by the large needs of water for agriculture. Many times this source of water is added by flooding to the fields, creating short temporal oxygen-depleted environments, where nitrous oxide (N2O) emissions are promoted. Agriculture is responsible for up to 60% of the global annual emissions of this gas, and its emission factors (EF) must be reported. During 21 months, we installed closed chambers to measure the N2O emissions from a wastewater irrigated plot in the Mezquital Valley. Here, alfalfa, rye grass, and maize were grown in succession, receiving mainly organic N contained in the untreated wastewater and the residues of the previous crop; only maize received extra mineral fertilization of 100 kg of N ha−1. We obtained a time series where the gaps were filled by linear interpolation. EF and N2O direct emissions were estimated by the Tier 1 approach of the IPCC. We found that the alfalfa and rye grass, which only receive organic nitrogen, produced minor N2O emissions, that reflected in lower EF (0.004 and 0.001, respectively), compared with the default value of the IPCC (0.01). In contrast, maize, which receives organic and inorganic N, lost 1% of this N input as N2O, the same as the default value (0.01). It seems that the form of N, the crop age and type influence greatly the N dynamics in this wastewater irrigated land-use system. Therefore, the Tier I approach of the IPCC seems to underestimate the N efficiency of this agroecosystem and overestimates the N2O direct emissions from alfalfa and rye grass.

Doña Aurelia: nuevo cultivar de piñón para el trópico de México

Durante más de ocho años, el INIFAP ha realizado trabajos de investigación enfocados a los insumos para la producción de biocombustibles entre ellos el piñón mexicano (Jatropha curcas L.). A lo largo de este tiempo, se establecieron ensayos genéticos en cuatro ambientes tropicales de México basados en genotipos seleccionados de acuerdo con sus atributos agronómicos e industriales. Los principales criterios de selección abordados fueron: rendimiento de grano, contenido de aceite, hábito de crecimiento y presencia de flores femeninas. Los mejores genotipos de los ensayos fueron dos variedades con presencia de 100% de flores femeninas y una variedad con predominio de flores masculinas, pero también con la presencia de flores femeninas y hermafroditas. Una de estas variedades con flores 100% femeninas se registró con la denominación ‘Doña Aurelia’ con título de obtentor número 1541. Esta variedad ha demostrado ser estable en cuanto a sus características morfológicas y de producción en los años de evaluación. Esta variedad tiene un rendimiento promedio en ambientes del trópico húmedo de 0.49 t ha-1 en el primer año del cultivo, con un rendimiento potencial al primer año de 0.98 t ha-1, bajo condiciones de trópico seco. Alcanza rendimientos de 3 t de grano seco por hectárea al cuarto año de producción. El contenido promedio de aceite en las semillas de la variedad es de 53.4%. Las características fisicoquímicas del aceite son: 98.57 gI2/100 de índice de yodo, 0.921 g cm-3 de densidad, 34.894 mm2 s-1 de viscosidad y 2.974 mg KOH g-1 de índice de acidez y composición de ácidos grasos de 35.36% de ácidos grasos saturados y 64.64% de ácidos grasos insaturados, de acuerdo con la norma americana ASTM ‘Doña Aurelia’ se considera de buena calidad como materia prima para obtener biodiesel.

The Effect of Bacterial Sulfate Reduction Inhibition on the Production and Stable Isotopic Composition of Methane in Hypersaline Environments

The aim of this research was to investigate the competition between methanogens and sulfate-reducing bacteria in hypersaline environments. Samples of photosynthetic microbial mats, both soft mats (salinities of 55–126 ppt) and gypsum-hosted endoevaporite mats (salinities of 77–320 ppt), were obtained from hypersaline environments in California, USA, Mexico and Chile. Methane production was determined from the increase in headspace methane concentration within incubation vials containing mat samples. At the end of the incubation period, the δ13C values of produced methane were measured. Soft microbial mat vials containing molybdate, a specific inhibitor of bacterial sulfate reduction, exhibited dramatically higher methane production rates and higher (enriched in 13C) methane δ13C values than the controls. This suggests that the inhibition of sulfate reduction allowed the methanogens at these sites to use the competitive substrates (H2 and/or acetate) made available. Further, the higher δ13C values of the produced methane suggest that substrates (both competitive and non-competitive) were used to near completion. At the endoevaporite sites, which have much higher salinities than the soft mat sites, methane production was not significantly different and the methane δ13C values either remained the same or decreased (depleted in 13C) with added molybdate. We suggest that substrate availability increased enough to allow for somewhat greater isotopic fractionation resulting in the lower methane δ13C values that were observed, but not enough to significantly increase measured production rates. Where no changes in either methane production rates or δ13C values occurred, we hypothesize that salinity itself was inhibiting sulfate reduction and thus controlling microbe populations and rates of metabolism.

MANEJO DE LOS MEDICAMENTOS VETERINARIOS CADUCOS EN LA ZONA METROPOLITANA DEL VALLE DE MÉXICO

In Mexico, veterinary expired medications are classified as hazardous waste according to the Mexican Official Standard NOM-052-SEMARNAT-2005. Nevertheless, a void in the assignation of responsibility regarding the monitoring and fulfillment of regulations distorts the procedures comprising their managing and final disposal, since medications are still disposed in the garbage or flushed down the toilet or sink. The aim of this study was to know the current situation of the management of these residues in the Metropolitan Zone of Mexico City (MZMC). A survey was conducted including 162 managers of veterinary pharmacies, of which 112 agreed to collaborate. Our findings revealed that more than 95% of the respondents are conscious that their establishments generate diverse types of hazardous waste (including expired medications) and claim that some veterinary medications are expired in their pharmacies. Although 64.3% of the respondents reported they use the service of companies specialized in the removal and/or destruction of expired veterinary medications in the MZMC, there does not exist an interest to corroborate if such enterprises operate in accordance to regulations, if they give a final disposition adapted to these kind of waste or even to know the management way of waste, since 95% of the companies named by the respondents are not registered nor authorized by the Secretariat of Environment and Natural Resources of Mexico. From this study, it is concluded that there are mechanisms in Mexico for the correct environmental management of pharmaceutical waste; however, the absence of specific policies for veterinary expired medications makes management, treatment and/or disposal methods inadequate.

Reproductive Cold Stress Tolerance in Sorghum F1 Hybrids is a Heterotic Trait

The sensitivity of sorghum to pre-flowering cold stress, resulting in reduced pollen viability and poor seed set, is a major constraint for expanding growing areas into higher altitudes and latitudes. Nevertheless, compared to juvenile cold tolerance, reproductive cold tolerance in sorghum has received much less attention so far, and very little is known about its inheritance in F1-hybrids. We have composed a representative factorial (n = 49 experimental F1-hybrids) for a comprehensive study on heterosis and combining ability for crucial tolerance traits as spikelet fertility (panicle harvest index), seed yield and pollen viability, using field trials in stress- and control environments in Germany and Mexico as well as climate chamber experiments. Our results indicate a heterotic and rather dominant inheritance of reproductive cold tolerance in sorghum, with strong effects of female general combining ability (GCA) on F1-hybrid performance in our material. These findings, together with the comparatively low contribution of specific combining ability (SCA) effects and high heritability estimates, suggest that robust and efficient enhancement of reproductive cold tolerance is feasible via hybrid breeding.

Feeding leucaena to dairy cows in intensive silvopastoral systems in Colombia and Mexico

Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia.The demand for milk and dairy products globally is expected to grow in future decades, leading to an increase in the global dairy cattle population. Therefore it is important to identify production options that both improve efficiency and help reduce negative effects on the environment. Intensive silvopastoral systems have been proposed as a sustainable strategy in the tropics to increase the availability and quality of forage throughout the year for milk production from cattle. This paper reports the effects of silvopastoral systems that include leucaena at the farm level on milk production and on the environment in both Colombia and Mexico. Evaluation of different milk production systems has shown that the leucaena-based systems increased milk production both per cow and per hectare, increased the production of milk solids, improved the fatty acid profile in the milk and resulted in environmental benefits when compared with conventional systems.