Resumen La distribución potencial de las poblaciones de Pinus cembroides depende de la variabilidad espacial y temporal de la temperatura y la precipitación. Dado el incremento en la disponibilidad de diferentes bases de datos climáticos en las últimas décadas, el objetivo del presente estudio fue evaluar el efecto de su variabilidad espacial y temporal en la modelación de la distribución potencial de P. cembroides. Se utilizó el algoritmo de Máxima Entropía (MaxEnt) para obtener la distribución potencial de P. cembroides a partir de los registros del Inventario Nacional Forestal y de Suelos y del Sistema Nacional de Información sobre Biodiversidad, con datos de cuatro fuentes de información climática. A pesar de las diferencias en la resolución espacial, se obtuvieron cuatro modelos confiables con valores de AUC cercanos a 0.8. La distribución de P. cembroides está limitada por la temperatura media de los trimestres más húmedo (Bio 8) y más seco (Bio 9). Los modelos de WorldClim v2.1 y SCM presentaron una mayor correlación entre la distribución de P. cembroides y las variables bioclimáticas seleccionadas. En los cuatro modelos, la especie registró una mayor probabilidad de ocurrencia (>70 %) en las sierras Madre Oriental y Occidental. Se concluye que son necesarias bases de datos con una resolución espacial de al menos 15 km2 para los estudios de distribución de P. cembroides. Este tipo de investigaciones deben considerarse un primer paso en la planeación y desarrollo de estrategias de manejo y conservación de la especie.

Abstract The potential distribution of Pinus cembroides populations depends on the spatial and temporal variability of the temperature and precipitation. Given the increase in the availability of different climatic databases in the last decades, the objective of the present study was to evaluate the effect of their spatial and temporal variability on the modeling of the potential distribution of P. cembroides. The Maximum Entropy (MaxEnt) algorithm was used to obtain the potential distribution of P. cembroides from the records of the National Forest and Soil Inventory and the National Biodiversity Information System with data from four sources of climatic information. Despite differences in spatial resolution, four reliable models were obtained with AUC values close to 0.8. The distribution of P. cembroides is limited by the mean temperature of the wettest (Bio 8) and driest (Bio 9) quarters. The WorldClim v2.1 and SCM models presented a higher correlation between the distribution of P. cembroides and the selected bioclimatic variables. In all four models, the species recorded a higher probability of occurrence (>70 %) in the Eastern and Western Sierras Madre. It is concluded that databases with a spatial resolution of at least 15 km2 are necessary for distribution studies of P. cembroides. The type of research should be considered a first step in the planning and development of management and conservation strategies for the species.

ABSTRACT The biological importance of rhizosphere sediment-associated fungi in mangroves is poorly understood, especially when they are affected by high salinity and anaerobiosis in disturbed areas. This study evaluated the fungal diversity in the rhizosphere sediments of three mangrove species associated with three conservation conditions of mangrove forests in preserved, semi-preserved, and deteriorated areas. In addition, fungal bioactivity was correlated to the fungal diversity found in mangrove species from each area. We isolated 50 fungal strains belonging to three phyla, seven classes, and 10 orders. The fungal diversity was higher in the preserved area (H’ = 2.22) than in the semi-preserved (H’ = 1.73) and deteriorated areas (H’ = 1.68); the redundancy analysis showed a tendency of fungal accumulation towards the rhizosphere of Rhizophora mangle and Avicennia germinans in the preserved and semi-preserved areas. In addition, the redundancy analysis showed that 10 bioactive fungi genera tended to accumulate on the rhizosphere of R. mangle and A. germinans in the preserved and semi-preserved areas. The preserved area is related to the semi-preserved area, with a 28% Jaccard similarity coefficient. The diversity and bioactivity of the isolated fungi encourage the need to conserve and restore mangrove ecosystems considering their current and potential services, such as bioprospecting new pharmacological compounds.

Abstract The use of beneficial microorganisms in agriculture can increase the productivity of agricultural crops; however, there are few studies that consider aromatic plants, such as basil (Ocimum basilicum L.). The aim of this study was to evaluate the growth of 'Sweet Nufar' basil inoculated with arbuscular mycorrhizal fungi (AMF) and Azospirillum brasilense. The treatments tested were: 1) without microorganisms (control), 2) Rizhophagus intraradices, 3) Funneliformis mosseae, 4) AMF consortium, 5) Azospirillum brasilense, 6) R. intraradices + A. brasilense and 7) without microorganisms and irrigated with 100 % Steiner's nutrient solution. Treatments 1 to 6 were irrigated with the same nutrient solution, but at 50 %. Fifty days after transplanting, growth variables, mineral concentration, colonization percentage and number of AMF spores were recorded. The AMF and A. brasilense bacterium increased the fresh biomass weight and leaf area of 'Nufar' basil, which was associated with the highest concentration of nitrogen and potassium in the plant tissue. This implies that the microorganisms evaluated increase the development and growth of basil grown with reduced levels of mineral nutrition, which represents a sustainable alternative in the agronomic management of this crop under greenhouse conditions.

Resumen El uso de microorganismos benéficos en la agricultura puede incrementar la productividad de los cultivos agrícolas; sin embargo, existen pocos estudios que consideran a las plantas aromáticas, como la albahaca (Ocimum basilicum L.). El objetivo del presente estudio fue evaluar el crecimiento de albahaca ‘Sweet Nufar’ inoculada con hongos micorrícicos arbusculares (HMA) y Azospirillum brasilense. Los tratamientos ensayados fueron: 1) sin microorganismos (testigo), 2) Rizhophagus intraradices, 3) Funneliformis mosseae, 4) consorcio de HMA, 5) Azospirillum brasilense, 6) R. intraradices + A. brasilense y 7) sin microorganismos e irrigados con solución nutritiva de Steiner al 100 %. Los tratamientos del 1 al 6 se irrigaron con la misma solución nutritiva, pero al 50 %. Cincuenta días después del trasplante se midieron variables de crecimiento, concentración mineral, porcentaje de colonización y número de esporas de HMA. Los HMA y la bacteria A. brasilense incrementaron el peso de biomasa fresca y el área foliar de albahaca ‘Nufar’, lo cual se asoció con la mayor concentración de nitrógeno y potasio en el tejido vegetal. Lo anterior implica que los microorganismos evaluados aumentan el desarrollo y el crecimiento de albahaca cultivada con niveles de nutrición mineral reducido, lo que representa una alternativa sustentable en el manejo agronómico de dicho cultivo en condiciones de invernadero.

Resumen Introducción. Los α-cetoanálogos de aminoácidos esenciales se utilizan en el tratamiento de la enfermedad renal crónica para retrasar los síntomas de la uremia. Sin embargo, se desconoce si los α-cetoanálogos de aminoácidos esenciales afectan el estrés oxidativo y la inflamación en la lesión renal aguda tal como en la producida por la isquemia-reperfusión. Objetivo. Evaluar el efecto de las α-cetoanálogos de aminoácidos esenciales sobre la lesión renal por isquemia-reperfusión en ratas Wistar. Materiales y métodos. Se emplearon 11 grupos de ratas (n=6): dos grupos recibieron solución salina fisiológica con lesión isquemia-reperfusión o sin ella (45 min/24 h), seis grupos recibieron α-cetoanálogos de aminoácidos esenciales (400, 800 o 1.200 mg/kg/24 h/7d) con lesión isquemia-reperfusión o sin ella (α-cetoanálogos de aminoácidos esenciales + isquemia-reperfusión), y dos grupos recibieron (50 mg/kg/24 h/7d) con lesión isquemia- reperfusión o sin ella. Los marcadores bioquímicos incluyeron creatinina y nitrógeno ureico en sangre (BUN), citocinas proinflamatorias (IL-1β, IL-6 y TNF-α), marcadores de daño renal (cistatina C, KIM-1 y NGAL) y marcadores del estrés oxidativo como el malondialdehído (MDA) y la actividad antioxidante total. Resultados. Los grupos tratados con α-cetoanálogos de aminoácidos esenciales y alopurinol tuvieron niveles inferiores de creatinina, BUN, marcadores de daño renal, citocinas proinflamatorias, actividad antioxidante total y MDA que los grupos isquemia- reperfusión correspondientes. Estos cambios se asociaron con la dosis. La actividad antioxidante total fue menor en los grupos tratados con α-cetoanálogos de aminoácidos esenciales que en los grupos isquemia-reperfusión correspondientes. Conclusiones. Este es un nuevo informe de los efectos nefroprotectores de las α-cetoanálogos de aminoácidos esenciales contra la lesión isquemia-reperfusión. Los α-cetoanálogos de aminoácidos esenciales disminuyeron los niveles de los marcadores bioquímicos, de los de lesión renal, de las citocinas proinflamatorias y el MDA, a la vez que minimizaron el consumo total de antioxidantes.

Abstract Introduction: Essential amino acid α-keto acid analogs are used in the treatment of chronic kidney disease to delay the symptoms of uremia. However, it is unknown whether essential amino acid α-keto acid analogs affect the oxidative stress and the inflammation in acute renal injury such as those produced by ischemia-reperfusion. Objective: To evaluate the effect of essential amino acid α-keto acid analogs on renal ischemia-reperfusion injury in Wistar rats. Materials and methods: Rats were divided into 11 groups (n=6/group): Two groups received physiological saline with or without ischemia-reperfusion injury (45 min/24 h), six groups received essential amino acid α-keto acid analogs (400, 800, or 1,200 mg/kg/24 h/7d) with or without ischemia-reperfusion injury (essential amino acid α-keto acid analogs + ischemia-reperfusion), and two groups received allopurinol (50 mg/kg/24 h/7d) with or without ischemia-reperfusion injury. Biochemical markers included creatinine and blood urea nitrogen (BUN), proinflammatory cytokines (IL-1β, IL-6, and TNF-α), renal damage markers (cystatin C, KIM-1, and NGAL), and markers of oxidative stress such as malondialdehyde (MDA) and total antioxidant activity. Results: The essential amino acid α-keto acid analog- and allopurinol-treated groups had lower levels of creatinine, BUN, renal damage markers, proinflammatory cytokines, and MDA than their corresponding ischemia-reperfusion groups. These changes were related to the essential amino acid α-keto acid analogs dosage. Total antioxidant activity was lower in essential amino acid α-keto acid analog- and allopurinol-treated groups than in the corresponding ischemia-reperfusion groups. Conclusions: This is a new report on the nephroprotective effects of essential amino acid α-keto acid analogs against ischemia-reperfusion injury. Essential amino acid α-keto acid analogs decreased the levels of biochemical markers, kidney injury markers, proinflammatory cytokines, and MDA while minimizing total antioxidant consumption.

Abstract The objective was to evaluate the effects of two (2x) vs three (3x) times per day milking on milk production and milk composition in dairy cows. Fourteen scientific papers, containing production data from 16 trials, where dairy cows were milked 2x or 3x, were analysed using meta-analysis with fixed and random-effects with the R statistical program. The degree of heterogeneity and publication bias were measured with the I2 statistic and Begg's test, respectively. In addition, the meta-regression analysis explored other sources of heterogeneity for the response. The estimated effect size of 2x and 3x milkings was calculated for dry matter intake (DMI), milk production, and milk composition. Dry matter intake, milk production, and milk fat and protein yields showed substantial heterogeneity (I2>50%). Whereas milk fat-percentage had moderate heterogeneity (I2<50%), and milk protein had no (I2=0%) heterogeneity. The year of publication, trial duration, and cattle breed did not influence production response parameters to milking frequency. We found no evidence of publication bias for the parameters evaluated (Begg's test; P>.05). Cows milked 2x produced less milk (2.23 kg/d), less milk fat (0.06 kg/d), and less milk protein (0.05 kg/d). In contrast, the fat percentage was lower (0.07 units) in 3x, compared with 2x milking frequency. There was no effect of milking frequency on DMI and milk protein percentage. In conclusion, milk production and milk fat and protein yields improves as milking frequency increase from 2x to 3x daily, without affecting DMI. The implementation of 3x milking frequency must consider dairy cow management, labor, and milking parlour infrastructure, particular to each dairy farm.

ABSTRACT Coccidioidomycosis is an endemic disease of arid regions in the Western hemisphere. Its clinical presentation varies from asymptomatic nodules on chest x-rays to disseminated disease. We present the case of a 48-year-old man with a hard and heterogeneous tumor in the posterior aspect of the right testis. Color flow doppler testicular ultrasonography was performed and two nodular masses in the tail of the right epididymis were identified. An epididymectomy was performed and histopathological examination revealed coccidioidomycosis. After diagnosis, the patient was successfully treated with fluconazol.

Resumen Introducción. El virus sincicial respiratorio humano (hRSV) es la causa más frecuente de infección respiratoria aguda de las vías respiratorias inferiores en niños menores de cinco años. El desarrollo de técnicas moleculares para identificarlo es uno de los retos actuales en el campo de la investigación clínica. Objetivo. Evaluar un método de amplificación isotérmica para la detección rápida del hRSV en niños con infección respiratoria aguda. Materiales y métodos. Se extrajo el ARN viral de 304 muestras de hisopado nasal en niños con síntomas de infección respiratoria aguda atendidos en el servicio de urgencias del Hospital de la Universidad del Norte en Barranquilla entre abril del 2016 y julio del 2017. Se evaluó la prueba de amplificación isotérmica mediada por bucle mediante transcriptasa inversa de la proteína de la matriz (M) (Reverse Transcription Loop-Mediated Isothermal Amplification, RT-LAMP) comparada con técnicas moleculares como la reacción en cadena de la polimerasa mediante transcriptasa inversa múltiple anidada (Reverse Transcription- Polymerase Chain Reaction, RT-PCR), la cual se empleó como la prueba estándar, la PCR en tiempo real (quantitative PCR, qPCR) y la RT-LAMP de la proteína L (L) para la detección rápida del virus sincicial respiratorio (VSR), subtipo A y subtipo B. Resultados. La prueba de RT-LAMP (M) tuvo una sensibilidad de 93,59 %, una especificidad de 92,92 % y una concordancia de 0,83 ± 0,036 comparada con la prueba de RT-PCR anidada. El índice kappa del RT-LAMP (M) fue superior, y los valores del RT-LAMP (L) y la qPCR concordaron (0,75 ± 0,043 y 0,71 ± 0,045, respectivamente). Conclusiones. Estos resultados indican que la prueba RT-LAMP (M) puede considerarse como una herramienta de utilidad clínica para detectar el hSRVA, dado que el tiempo requerido para la obtención de resultados, así como los costos, es menor, y su desempeño es mejor que el de las otras pruebas moleculares evaluadas.

Abstract Introduction: Human respiratory syncytial virus (hRSV) is the most frequent cause of acute respiratory infection of the lower respiratory tract in children under the age of five. The development of molecular techniques able to identify hRSV is one of the current challenges in the field of clinical research. Objective: To evaluate the ability of an isothermal amplification method to rapidly detect hRSV in children with acute respiratory infection. Materials and methods: We collected 304 nasopharyngeal swab samples from children with symptoms of acute respiratory infection who attended the emergency unit at Hospital de la Universidad del Norte in Barranquilla from April, 2016, to July, 2017. After extracting viral RNA from the samples, we evaluated the ability of the reverse transcriptase-loop-mediated isothermal amplification (RT-LAMP) M assay to rapidly detect hRSVA and hRSVB compared to other molecular techniques: quantitative PCR (qPCR), reverse transcriptase-LAMP L assay, and as a standard, the multiplex nested reverse transcriptase polymerase chain reaction (nested RT-PCR). Results: The RT-LAMP M assay had a sensitivity of 93.59% and a specificity of 92.92%, and a concordance of 0.83 ± 0.036 as compared with the nested RT-PCR test. While the Kappa index of the RT-LAMP M assay was higher than the values for the RT-LAMP L assay and the qPCR, the values of the latter two methods were in agreement (0.75 ± 0.043 and 0.71 ± 0.045, respectively). Conclusion: Due to the shorter running times, lower costs and better performance of the RT-LAMP M assay, it can be considered as a useful clinical tool for the detection of RSVA.

Abstract: The use of Ovsynch plus controlled internal drug release of progesterone (CIDR) in high producing dairy cows was evaluated. The study was carried-out at the Comarca Lagunera (25° 44´ N, 103° 10´ W, at 1,111 m asl.) during December and January. Cows (n= 100) were pre-synchronized with two injections of PGF2α at 35 and 47 d postpartum and assigned to two treatments (n= 50 each). 1) The group OV received the Ovsynch protocol: 100 µg GnRH (i.m.; d 1), 25 mg of PGF2α (i.m.; d 7), and 100 µg GnRH (i.m.; d 9); 2) The group OV+C was subjected to the Ovsynch protocol plus a CIDR (1.38 g P4) which was removed at d 7. Cows of both groups were exposed to a fixed time artificial insemination protocol (IATF; 16 to 20 h after the last injection). Response variables included pregnancy rate, cows with repeated estrus considering two periods, ≤24 and ≥25 d after insemination, and the period to return to estrus. While no differences occurred between groups regarding pregnancy rates (OV= 28 %, OV+C= 32 %; P>0.05), the percentage of cows showing estrus after IATF differed (P<0.05) between treatments for the two studied periods (28 % vs 62 % ≤24 d; 69 % vs 35 % ≥25 d; OV and OV+C, respectively). Moreover, mean of days when cows repeated estrus was lower (P<0.05) in the OV+C group (25 ± 1.6 vs 30 ± 1.3 d). Although the Ovsynch+CIDR treatment did not improve pregnancy rate, it reduced the latency for return to estrus, emerging as an alternative to diminish the days to the next AI, and potentially improve the reproductive efficiency and the economic return of the dairy herd.

Resumen: Se evaluó el uso de Ovsynch más dispositivo intravaginal de liberación controlada de progesterona (CIDR) en vacas altas productoras. El estudio se llevó en la Comarca Lagunera (25° 44´ N, 103° 10´ O a 1,111 msnm) durante diciembre y enero. Las vacas (n=100) se pre-sincronizaron con dos inyecciones de PGF2α a los 35 y 47 días posparto y asignadas a dos tratamientos (n= 50): 1) El grupo OV recibió el protocolo Ovsynch: 100 µg de GnRH (i.m.; día 1), 25 mg de PGF2α (i.m.; día 7) y 100 µg GnRH (i.m.; día 9); 2) El grupo (OV+C) recibió el protocolo Ovsynch más un CIDR (1.38 g), retirado siete días después. Todas las vacas se expusieron a un protocolo de inseminación artificial a tiempo fijo (IATF; 16 a 20 h posteriores a la última inyección). Se registró tanto el porcentaje de preñez, el número de vacas repitiendo celo considerando dos periodos (≤24 y ≥25 días post-inseminación), así como los días de retorno al celo. Mientras que no existió diferencia entre grupos para tasa de preñez (OV= 28 %, OV+C= 32 %; P>0.05), el porcentaje de vacas que manifestaron celo después de la IATF difirió (P<0.05) entre tratamientos durante los dos periodos estudiados, 28 vs 62 % ≤24 días; 69 vs 35 % ≥25 días; OV y OV+C, respectivamente. El promedio de días en que repitieron celo fue menor (P<0.05) en el OV+C (25 ± 1.6 vs 30 ± 1.3). El tratamiento Ovsynch+CIDR no mejoró la tasa de preñez; sin embargo, redujo la latencia en el retorno al celo, destacando como una alternativa para disminuir los días a la siguiente IA, y potencialmente para mejorar la eficiencia reproductiva y el retorno económico del hato lechero.

ABSTRACT Larval fish composition and abundance were analyzed during February-March (winter) and November-December (autumn) of 2005 to investigate which environmental conditions and mesoscale oceanographic processes affect the distribution of larval fish assemblages in the Gulf of California, and if these variables and processes are useful to delimit specific regions of ichthyofaunal distribution. The overall pattern was mostly a latitudinal gradient of the abundance of two faunistic complexes of larval fish assemblages (temperate northern and tropical southern complexes) strongly associated with the spatial distribution of sea surface temperature. The integration of these results, with previous investigations in the region, lets us confirm that the northern and southern larval fish assemblages extend and contract their distribution ranges according to the latitudinal displacement of the 21°C sea surface isotherm. We identified this to be a valuable criterion to establish the southern distribution limit of the temperate larval fish assemblage, and the 18°C as the northern limit of the tropical larval fish assemblage. However, this general pattern is maintained only in absence of mesoscale oceanographic features (upwelling and eddies) that increase larval drift from the coast to the central region of the Gulf, particularly during the November-December period when longitudinal gradients were stronger than in February-March.

Abstract Background Fungi from mangrove forests represent a great potential for the bioprospecting of new bioactive metabolites. The rhizosphere of several regions of the world has been widely studied, however, there are no studies on the biodiversity of Mexican mangroves. Objectives To evaluate the anti-proliferative activity of fungal extracts isolated from accumulated sediments in the rhizosphere of three mangrove species distributed in three zones with different degrees of salinity in Mexico. Methods The isolated fungi were identified at genus level by taxonomic keys. The anti-proliferative activity was determined by the SRB assay and the strains with values of GI50 <100 μg.mL-1 were identified molecularly. Results and conclusions Six extracts from four strains exhibited GI50 values < 100 µg.mL-1 in at least one cancer cell line. A strain of Aspergillus pulverulentus isolated from a disturbed area of Avicennia germinans showed the highest anti-proliferative activity against six different cancer cell lines. The GI50 values ranged from 40 to 83 µg.mL-1 in biomass extracts and 6 to 28 µg.mL-1 in culture broth extracts. This paper is the first study of bioprospecting fungi showing anti-proliferative activity in mangrove sediments in Mexico.

Resumen Antecedentes Los hongos de los bosques de manglar representan un gran potencial para la bioprospección de nuevos metabolitos bioactivos. La rizósfera de varias regiones del mundo ha sido ampliamente estudiada, no obstante, no existen estudios sobre la biodiversidad de los manglares mexicanos. Objetivos Evaluar la actividad anti-proliferativa de extractos de hongos aislados de sedimentos acumulados en la rizósfera de tres especies de mangles distribuidos en tres zonas con diferentes grados de salinidad en México. Métodos Los hongos aislados se identificaron a nivel de género, mediante claves taxonómicas. Se determinó la actividad anti-proliferativa mediante el ensayo SRB y se identificaron molecularmente las cepas con valores de GI50 <100 µg.mL-1. Resultados y conclusiones Seis extractos de cuatro cepas presentaron valores de GI50 <100 µg.mL-1 en al menos una línea celular cancerosa. Una cepa de Aspergillus pulverulentus aislada de una zona perturbada de Avicennia germinans mostró la mayor actividad anti-proliferativa con seis líneas celulares de cáncer diferentes. Los valores de GI50 variaron de 40 a 83 µg.mL-1 en extractos de biomasa y de 6 a 28 µg.mL-1 en extractos de caldo de cultivo. Este trabajo es el primer estudio de bioprospección de hongos que muestran actividad anti-proliferativa en sedimentos de manglar en México.

The situational disease is a nosographic category little analyzed in the medical literature. In this work important aspects related to its classificatory and practical value are approached, as well as the importance that it has in the training plan of the comprehensive general doctor, due to the development potentialities in the community. It is also emphasized on the practical possibilities of implementing the support psychotherapeutic procedures that are opportune and facilitators to avoid the overflood of secondary assistance demand, resulting from referral

La enfermedad situacional es una categoría nosográfica poco analizada en la bibliografía médica. En este artículo se abordan aspectos importantes relacionados con su valor clasificatorio y práctico, así como la importancia que reviste en el plan de formación del médico general integral, debido a las potencialidades de desarrollo en la comunidad. Además, se enfatiza en las posibilidades prácticas de aplicar los procedimientos psicoterapéuticos de apoyo, que son oportunos y facilitadores para evitar la sobresaturación de la demanda asistencial secundaria, resultante del envío o remisión

Abstract: Background and Aims: Endemism is a common phenomenon in arid regions. In this study we reviewed the distribution of endemic plants in the Chihuahuan Desert (DCH), which includes portions of the states of Arizona, Chihuahua, Coahuila, Durango, Nuevo Leon, Nuevo Mexico, San Luis Potosi, Tamaulipas, Texas and Zacatecas. Methods: A database was set up summarizing the information on the restricted species from the DCH. The following types of endemism were considered: 1) endemics which are known from the study region only, 2) quasi-endemics with distribution mainly in the DCH and some populations in the neighboring areas, 3) micro-endemics which are restricted to one location, and 4) endemics of non-arid habitats in the area. Key results: A total of 826 taxa (including species, additional infraspecific taxa and hybrids) were determined to be endemics or quasi-endemics, representing 24.87% of the total flora. Of this, 560 are endemics, 165 quasi-endemics, 176 micro-endemics and 116 are from non arid habitats. The families with the most endemics are Cactaceae (141 species), Asteraceae (106), Boraginaceae (34) and Brassicaceae (31), that represent 46.2% of the total. The genera with the highest taxa numbers are Coryphantha (24), Echinocereus (14), Mammillaria (15), Turbinicarpus (15). Nine genera are exclusive to the DCH. The dominant biological forms are perennial herbs and shrubs, frequently distributed in the xeric shrubland. The endemic distribution is heterogeneous, with a density index of 0.128 species/km2. Coahuila has the largest number of elements (31.15%). Conclusions: It is suggested to continue the protection of Cuatro Ciénegas, and portions of Brewster, as well as the Sierras La Madera and El Carmen. Sierras de Parras, La Paila and Jimulco, and Concepción del Oro and Presidio, are proposed as conservation areas, as they concentrate a large number of endemic species.

Resumen: Antecedentes y Objetivos: El endemismo es un fenómeno común de los organismos en las regiones áridas. En el presente trabajo se revisó la distribución de las plantas endémicas del Desierto Chihuahuense (DCH), cuya superficie abarca parte de los estados de Arizona, Chihuahua, Coahuila, Durango, Nuevo León, Nuevo México, San Luis Potosí, Tamaulipas, Texas y Zacatecas. Métodos: A través de la recopilación de información se elaboró una base de datos de especies con distribución restringida al DCH. Se consideraron los siguientes tipos de endemismo: 1) endémicos estrictos: aquellos elementos con localización conocida solo para el área de estudio, 2) cuasi -endémicos: aquellos presentes principalmente en el DCH y algunas poblaciones en localidades vecinas, 3) micro-endémicos: los que tienen una distribución restringida a una sola localidad y 4) endémicos a la región, pero de ecosistemas no áridos. Resultados clave: Se identificaron 826 taxa (incluye especies, taxa infraespecíficos adicionales e híbridos) que representan 24.87% de la flora total, 560 elementos de distribución endémica, 165 cuasi-endémicos, 176 micro-endémicos y 116 de ecosistemas no áridos. Las familias con mayor cantidad de endemismos son Cactaceae (141 especies), Asteraceae (106), Boraginaceae (34) y Brassicaceae (31) que en conjunto representan 46.2% del total. Los géneros con mayor número de taxa son Coryphantha (24), Echinocereus (14), Mammillaria (15) y Turbinicarpus (15), así como nueve géneros exclusivos al DCH. Las formas biológicas dominantes son las hierbas perennes y arbustivas, presentándose frecuentemente en el matorral xerófilo. La distribución endémica es de forma heterogénea, con una densidad de 0.128 especies/km2. Coahuila concentra la mayor proporción de elementos (31.15%). Conclusiones: Se sugiere continuar con la protección de Cuatro Ciénegas, Brewster, las Sierras La Madera y El Carmen y proponer como áreas de conservación a las Sierras de Parras, La Paila y Jimulco, y Concepción del Oro y Presidio, por presentar una alta concentración de endemismos.