Sierra Madre Occidental Research Articles

Population differentiation and phylogeography inLycianthes moziniana(Solanaceae: Capsiceae), a perennial herb endemic to the Mexican Transition Zone

AbstractLycianthes moziniana (Solanaceae: Capsiceae) is a perennial herb with edible fruits that is endemic to Mexico. Three varieties are recognized, all known in the Mexican Transition Zone. Lycianthes moziniana var. margaretiana grows in the Sierra Madre Oriental, whereas L. moziniana var. moziniana is common along the Trans-Mexican Volcanic Belt and in the Sierra Madre Occidental. Lycianthes moziniana var. oaxacana is found exclusively in the Sierra Madre del Sur. The Mexican Transition Zone is a complex geological, climatic and biogeographical area, the result of tectonic and volcanic activity that has promoted genetic divergence and speciation. We determined the genetic variation and structure of L. moziniana. Using phylogeographical approaches, we described the demographic history and evolutionary processes leading its divergence. The intergenic spacers rpl32-trnL and ycf1 were sequenced for 133 individuals pertaining to 15 populations. The genealogical relationships were analysed using haplotype networks. Finally, based on ecological niche models, we inferred the palaeodistribution of L. moziniana during the Pleistocene. The genetic differences and the haplogroups matched the three described varieties. Geological and climatic events of the Mexican Transition Zone facilitated these results. The Trans-Mexican Volcanic Belt isolated the populations of the Sierra Madre Oriental and the Sierra Madre del Sur, while allowing the migration to the Sierra Madre Occidental, during the middle Holocene.

<p><strong>A re-evaluation of taxonomy in <em>Quercus</em> section <em>Lobatae</em> subsection <em>Racemiflorae </em>(Fagaceae), resurrection of the name <em>Q. pennivenia</em> and description of a new taxon, <em>Q. huicholensis</em></strong></p>

Changes to the taxonomy of Quercus section Lobatae subsection Racemiflorae occurring in western Mexico are here made to reflect new evidence regarding species relationships of two lineages occurring in the southern Sierra Madre Occidental. The name Q. pennivenia is resurrected to recognize plants previously included under the name Q. urbanii. A new taxon, Q. huicholensis, is described to represent a distinct lineage segregated from Q. conzattii. With these nomenclatural changes we recognize the subsection Racemiflorae to consist of six taxa and we provide a key for their determination.

Predation of nesting Thick-billed Parrots Rhychopsitta pachyrhyncha by bobcats in northwestern Mexico

SummaryWe report on what appear to be increasing predation events on nesting Thick-billed Parrots Rhychopsitta pachyrhyncha. Thick-billed Parrots are classified as ‘Endangered’ and their seasonal breeding range is restricted to increasingly fragmented and degraded high elevation mixed conifer forest habitat within the Sierra Madre Occidental region of north-western Mexico. Predation of established breeding pairs has recently contributed to the ongoing decline of Thick-billed Parrot populations by removing mature birds with high reproductive value, which has associated consequences for future recruitment. We observed increasing predation events on nesting Thick-billed Parrots by bobcats Lynx rufus accompanied by kittens throughout the 2018–2019 breeding seasons, and we speculate that recent reductions in bobcat habitat have pushed them into new ranges where they are supplementing their diet with nontraditional prey items.

Spatial modeling of the ecological niche of Pinus greggii Engelm. (Pinaceae): a species conservation proposal in Mexico under climatic change scenarios

Abstract: Pinus greggii is a species of socio-economic importance in terms of wood production and environmental services in Mexico, though it is restricted by particular environmental conditions to the Sierra Madre Occidental. Species distribution models are geospatial tools widely used in the identification and delineation of species’ distribution areas and zones susceptible to climate change. The objectives of this study were to: (i) model and quantify the environmentally suitable area for Pinus greggii in Mexico, and possible future distributions under four different scenarios of climate change; (ii) identify the most relevant environmental variables that will possibly drive changes in future distribution; and (iii) to propose adequate zones for the species’ conservation in Mexico. Some 438 records of Pinus greggii from several national and international databases were obtained, and duplicates were discarded to avoid overestimations in the models. Climatic, edaphic, and topographic variables were used and 100 distribution models for current and future scenarios were generated using the Maxent software. The best model had an area under the curve (AUC) of 0.88 and 0.93 for model training and validation, respectively, a partial ROC of 1.94, and a significant Z test (p<0.01). The current estimated suitable area of Pinus greggii in Mexico was 617.706.04 ha. The most relevant environmental variables for current distribution were annual mean temperature, mean temperature of coldest quarter, and slope. For the 2041-2060 models, annual mean temperature, precipitation of coldest quarter, and slope were the most important drivers. The use of climatic models allowed to predict a future decrease in suitable habitat for the species by 2041-2060, ranging from 48.403.85 (7.8% - HadGEM2-ES RCP 8.5 model) to 134.680.17 ha (21.8% - CNRM-CM5 RCP 4.5). Spatial modeling of current and future ecological niche of Pinus greggii also allowed to delineate two zones for in situ conservation and restoration purpose in northeastern (Nuevo Leon) and central (Hidalgo) Mexico.

Reconstrucción de la precipitación y caudal medio del río Piaxtla mediante anillos de crecimiento de Pseudotsuga menziesii (Mirb.) Franco

La reconstrucción de variables hidroclimáticas es importante para comprender el funcionamiento de las cuencas forestales y tomar decisiones sobre su manejo. En este trabajo se reconstruyó la precipitación y el caudal medio a partir de información de anillos de crecimiento de Pseudostuga menziesii en la cuenca del río Piaxtla. Con la información de siete series dendrocronologías, se construyó una sola cronología regional. Se probó la correlación de la cronología regional con eventos de fenómenos océano-atmósfera como El Niño Oscilación del Sur, Oscilación Decadal del Pacífico, Oscilación Multidecadal del Atlántico e Índices de la Severidad de Sequía de Palmer. Los resultados mostraron que fue posible la reconstrucción de la precipitación de noviembre-abril y el caudal medio noviembre-agosto a partir de la serie de madera temprana con ecuaciones verificadas y validadas: Precipitación = -271.538 + 447.764*(índice de madera temprana), (r = 0.85, n = 49, p &lt; 0.0001) y caudal medio = 5.123 + 0.623*log10(índice de madera temprana), (r = 0.68, n = 46, p &lt; 0.001). Excepto por la Oscilación Multidecadal del Atlántico, todos los fenómenos globales mostraron correlación significativa con la información de los anillos de crecimiento. Este estudio confirma que los bosques de P. menziesii de la Sierra Madre Occidental son altamente sensibles al clima, lo que se refleja en la anchura de anillos de crecimiento y a su vez en la variabilidad del caudal medio de la cuenca. Por lo anterior se debe aprovechar el potencial de este tipo de trabajos para prever los cambios en la disponibilidad de recursos hídricos, así como ampliar su uso en la valoración de servicios ambientales hidrológicos.

Geochemistry and geological control of Sonora obsidian: New insights into the provenance study of archaeological obsidians in Mexico

Obsidian artifacts found in thirteen archaeological localities of Sonora show a petrological relationship with rhyolitic outcrops scattered in various geological localities (El Pinacate, Sierra Libre, Sierra El Aguaje, Hermosillo, Babidanchi and Sierra Los Mochos). X-Ray Fluorescence geochemical analysis of a group of 133 samples was done, including archaeological artifacts, as well as geological samples and anhydrous cores (raw material-lithic nodules) coming from both geological outcrops and archaeological sites. The geochemical data were compared with reference sample values from known primary obsidian knowing outcrops that also were analyzed by conventional techniques of ICP and XRF previously published. Geochemical results can be integrated into two large groups of obsidian from Sonora, and their spatial distribution holds a direct relation with the geological origin of perlitic outcrops. The first group corresponds to Oligocene rhyolites from the Sierra Madre Occidental. The second group correlates with Middle-Late Miocene rhyolites is associated to the Proto-Gulf of California development. Archaeologically, a distinct temporal sequence was identified as concerning its use according to the cultural areas in which they were found. The geological studies on obsidian sources help us to understand, on the one hand, the origin of perlitic landforms, their spatial situation and, on the other hand, to have a measurable comparative reference, that contributed to know the cultural extension of its indigenous use over time, as well as the reach of the social interaction networks, flaking techniques and use of specific artifact types. Finally, the integration of their geological control and geochemical characteristics allowed us to establish a reliable base to achieve provenance interpretations of obsidian lithic complexes in Sonora. All elements described here represent the obsidian phenomenon in Sonora and have an affinity with obsidian sources of NW Mexico, which provides a unique identity that needs to be located in the context of the interdisciplinary research of lithic in Mexico and SW United States.

Characteristics of mesoscale convection over northwestern Mexico, the Gulf of California, and Baja California Peninsula

AbstractMesoscale convective systems (MCSs) are frequent, but understudied, components of the warm season climatology in northwestern Mexico. This study provides an update of previous research on convective development and examines MCS life cycle, structure, and motion from July through September. It focuses on a region south of the North American monsoon core and, from 2009 to 2018 satellite observations, on patterns of cloud tops higher than 10 km above sea level. The diurnal cycle of convection shows cells initiating in the early afternoon over the Sierra Madre Occidental mountains and becoming better organized over the next few hours. These features typically move westward, grow upscale to reach maximum vertical extent near local sunset, and weaken during the night. However, there is a distinct region of deep convection over and off the coast of Nayarit (20–23°N), in the Pacific Ocean, that remains active through the night and into the early morning, producing heavy rainfall and frequent lightning. Occasionally, the inner structure of these MCSs can move across the Gulf of California and reach the southern Baja California Peninsula. One particular long‐lived, fast‐moving MCS from July 23 and 24, 2014 was selected for in‐depth analysis, because it was associated with weather conditions that included unusual precipitation and extreme winds. The MCS caused damage from sustained winds of tropical‐storm strength and an intense gust front in the Los Cabos area, in the southern tip of the peninsula. This extraordinary MCS developed in the most unstable and humid environment recorded during the 1976–2018 period, and was supported by a collocated upper‐level, inverted trough and a lower‐troposphere tropical wave. We also found that the 10 most unstable conditions have all occurred after 2011, possibly indicative of a trend toward more frequent and favourable environments to spawn MCSs over the Gulf of California entrance.

Mortalidad por influenza y neumonía en la Macrorregión del Centro de México: un análisis de sus tendencias y su distribución geográfico-climática

Este estudio investiga dos aspectos de la mortalidad por influenza y neumonía en la Macrorregión del Centro de México: (i) sus tendencias recientes (1979-2015) y (ii) su distribución geográfico-climática. Para ello, se ocuparon los reportes mensuales de defunciones del Sistema Nacional de Información en Salud (SINAIS) a nivel municipal, los datos poblacionales de cuatro censos nacionales y los datos de temperatura (T) y humedad (ed) media mensual de la base de datos CRU-TS4.01 de la Universidad de East Anglia, Reino Unido. Los resultados respecto a (i) muestran que, pese al incremento poblacional durante los últimos años (del 80%), las tasas de mortalidad registraron una tendencia negativa significativa (del 60%). Respecto a (ii), los resultados indican que la mayor mortalidad ocurre principalmente sobre tres regiones frías y secas (T &lt; 16°C y ed &lt; 10 hPa) sobre el Altiplano Central, sobre las regiones montañosas de la Sierra Madre Occidental y la Sierra Madre Oriental. Esta relación mortalidad-clima, explica patrones medios, pero no anómalos, por lo que las tendencias registradas de mortalidad no pueden ser directamente relacionadas a tendencias en el clima. Similarmente, esta relación tampoco explica la mortalidad sobre las megaciudades de Ciudad de México, Guadalajara y Puebla; la mortalidad sobre estas ciudades está muy por debajo de la media de la macrorregión. Ambas excepciones sugieren que, una explicación más completa de las causas de los patrones de mortalidad en la macrorregión estudiada, necesariamente tendría que considerar factores no climáticos, como los biológicos, socio-económicos o culturales.

&lt;p&gt;&lt;strong&gt;&lt;em&gt;Cunila socorroae&lt;/em&gt;&lt;/strong&gt;&lt;strong&gt; (Lamiaceae) a new species from Sierra Madre Occidental, Durango, Mexico&lt;/strong&gt;&lt;/p&gt;

Recent botanical explorations in Durango, Mexico, led to the discovery of a new species endemic to this state: Cunila socorroae (Lamiaceae), which is consequently here described and illustrated. The new species is morphologically most similar to C. jaliscana and C. lythrifolia. It can be distinguished from both in having less flowers per cyme, lanceolate floral bracts, longer calyx tube, and lanceolate calyx teeth and longer. It also deviates from C. jaliscana by the fewer floral internodes, longer floral bract, and generally longer corolla tube. Also, the exfoliating bark, white corollas and internally pubescent, make a clear distinction against C. lythrifolia. The distinctive geographic distribution of these species is an additional support to their separation; the new species is exclusive of the middle portion of Sierra Madre Occidental, whereas C. jaliscana is restricted to the northernmost portion of Sierra Madre del Sur, and C. lythrifolia, though mostly occurs in eastern Tans-Mexican Volcanic Belt, has also some localities in southern Chihuahuan Desert, Sierra Madre Oriental and Sierra Madre del Sur.

New records of ectoparasites for Mexico and their prevalence in the montane shrew Sorex monticolus (Eulipotyphla: Soricidae) at Cerro del Mohinora, Sierra Madre Occidental of Chihuahua, Mexico.

The Flora and Fauna Protection Area (Área de Protección de Flora y Fauna-ÁPFF) Cerro del Mohinora, is the highest mountain in northern Mexico, reaching an elevation of 3,300 meters. It constitutes one of the last high-elevation islands of alpine and subalpine vegetation known in the Sierra Madre Occidental, in the extreme southwestern part of Chihuahua. The ÁPFF Cerro del Mohinora is located near the state border and limits with Durango and Sinaloa. This type of ecosystem located at high altitudes is in danger of disappearing since only 1% or less of its original extension remains; it is considered a refuge for species with boreal affinities (McDonald et al. 2011).

Geosites of interest as a geopheritage of Jalisco, Mexico. Progress

Conserving the geological heritage in Jalisco implies, identifying, classifying and substantiating the importance of geosites in Jalisco and its subsequent dissemination through geotourism. The above can contribute to the creation of geo-park (s), according to the definition and methodology of UNESCO, with the consequent economic benefit to the inhabitants of these regions. The disclosure of geological information encourages an appreciation and care of abiotic resources (rocks, minerals, fossils, morphology, soil and water), especially prior to productive activities, minimizing their damage or avoiding building in areas with geological hazards. Jalisco has a great geodiversity, compared to other states, its history begins approximately 200 million years ago, recorded in the Sierra Madre del Sur and in the Jalisco Block, the most recent volcanic and tectonic activity is recorded in the Volcanic Belt Mexican. The previous provinces, together with the Sierra Madre Occidental and the Central Plateau, contain a wide range of rocks, fossil areas of economic and cultural importance (most of 70 places) and relate the geological history and its dynamics. Geothermal activity, is present in 400 locations.

Effect of spatial resolution, algorithm and variable set on the estimated distribution of a mammal of concern: the squirrel Sciurus aberti

ABSTRACT Most potential habitat models have been built from WorldClim using low resolution variables, even for areas of high heterogeneity with few weather stations. The resulting models can be too general and lead to erroneous decisions when used for conservation purposes. Sciurus aberti is a tree squirrel inhabiting highlands in the SW US and the Sierra Madre Occidental (SMO) in Mexico, where it is considered a species of low concern. We examined the effect of resolution, variables, and algorithms on the predicted potential habitat of S. aberti in Mexico and compared the resulting models against a previous one created from WorldClim variables using GARP (Genetic Algorithm for Rule Set Production). Our best model, using Maxent, 30 m spatial resolution and topographic variables, predicted a fragmented distribution in pine and pine–oak forests, consistent with what is known about the species’ natural history. The area represented only 2% of the SMO (compared to 28% for the GARP model), of which only 0.33% lies within protected areas. The model suggests that the habitat is highly fragmented, which threatens population continuity. Therefore, we propose that the conservation status of Sciurus aberti must be reassessed and that forest management better consider the conservation of arboreal species.

First steps towards the identification of evolutionarily significant units in Mexican native trout: An assessment of microsatellite variation

In the remote high-elevation streams and rivers in the northwest of Mexico, there is an endemic and highly diverse group of native trout related to the rainbow trout lineage (Oncorhynchus mykiss). Currently, only two species have been formally described from this trout complex, the Mexican golden trout, O. chrysogaster, and the San Pedro Martir rainbow trout, O. m. nelsoni, but only the former occurs in the Sierra Madre Occidental (SMO). South and north of the O. chrysogaster range, there are other undescribed trout that have been recently discovered. Given the various human impacts on aquatic systems occupied by these Mexican native trout, the lack of taxonomic descriptions and the imminent risk of losing populations without their even being documented, we sought to infer a hierarchical population structure of the Mexican native trout, determine the geographic patterns of genetic diversity and gene flow among them, and identify evolutionarily significant units for a prompt conservation strategy. The allelic diversity across eleven microsatellite loci was used to assess genetic divergences of wild trout collected throughout its range in Mexico. Our results reject the old hypothesis that many of the trout in Mexico are introduced or translocated hatchery-reared rainbow trout and strongly support the new hypothesis of distinct genetic populations and lineages in the northwest of Mexico. According to the different statistical analysis of the genetic data, we distinguish between species and subspecies (O. chrysogaster, O. mykiss, and O. m. nelsoni) of the other regional lineages of undescribed trout (northern and southern) inhabiting the SMO. We also found a strong genetic substructure within these large clusters. We propose the presence of seven Evolutionarily Significant Units in the drainage basins of the SMO (two occur in the northern region, four in the southern, and one for the area of distribution of O. chrysogaster) and one in north-western Baja California. Based in microsatellite data a minimum gene flow among populations is evidenced, resulting the presence the highly divergent populations.

A checklist of the amphibians and reptiles of Sinaloa, Mexico with a conservation status summary and comparisons with neighboring states.

Sinaloa possesses a rich biota with unique characteristics due to its proximity to the northern deserts, the tropical lowlands of the south, and the temperate environments of the western slopes of the Sierra Madre Occidental in Mexico. However, threats to its environment makes understanding the biological diversity of Sinaloa crucial. A checklist of the amphibians and reptiles has been generated, and the conservation status of Sinaloa's herpetofauna summarized with the aim of understanding the potential conservation or management needs. Sinaloa has 159 species of amphibians and reptiles, including 39 species of amphibians and 120 species of reptiles. The herpetofauna of Sinaloa has relatively few species of conservation concern at a global and national scale (IUCN and SEMARNAT lists), but Environmental Vulnerability Scores suggest that there might be greater conservation concerns for the Sinaloa herpetofauna. Families of particular conservation concern include Craugastoridae, Eleutherodactylidae, Ambystomatidae, Crocodylidae, Dactyloidae, Eublepharidae, Helodermatidae, Iguanidae, Phrynosomatidae, Phyllodactylidae, Colubridae, Natricidae, Viperidae, Cheloniidae, and Dermochelyidae.

Unexpected spatial patterns of natural regeneration in typical uneven-aged mixed pine-oak forests in the Sierra Madre Occidental, Mexico

Natural forest regeneration, i.e. self-renewal of forest stands, involves the replacement of old trees by the next generation and is influenced by environmental factors. The spatial structure of tree regeneration depends on and also influences the properties of the stands themselves. Few studies have investigated spatial patterns of naturally regenerated areas in Mexican pine–oak forests, which are considered one of the world’s top 34 biodiversity hotspots. In this study, we analyzed the spatial patterns, particularly the spatial structure, in clusters of naturally regenerated trees in seven 100 × 100 m plots in the Sierra Madre Occidental (northern Mexico), in relation to three factors: slope, geographical aspect and distance between each sapling to the edge of the nearest gap in the canopy. Three indices were used to describe spatial structure and the data were analyzed by bivariate Ripley’s K(t)-functions and three-parameter and six-parameter Weibull models. The results indicate that sapling regeneration was marginal in canopy gaps. Sapling density was ten times higher under the canopy cover, close to the edge than in the gaps. On average, the first maximum number of saplings was detected inside the canopy at about 81 cm from the gap edge, forming ring-type spatial patterns around the canopy gaps. These results contrast with the gap dynamics described in many other studies. We attribute these findings to the nurse effect of trees, which ameliorate abiotic effects, such as the extreme drought that occurred in 2011 and 2012 in the study region. In covered zones close to canopy edges, thece orientation. We recommend adapting or changing the current forest management system to improve continuous forest regeneration (including adaptive silviculture). We also strongly support i) research on the effects of cattle grazing on natural regeneration in the region and ii) reduction of livestock pressure, which is essential to support forest renewal. Complementary reforestation, in addition to maintenance of the few saplings growing within the gaps, may help enhance forest regeneration. Finally, the use of alternative regeneration methods, such as an irregular group shelterwood method (Expanding Gap Silviculture “Femelschlag”), should also be considered, in order to promote natural regeneration more purposefully.

Composición y estructura espacial de cinco asociaciones de bosques de Pinus durangensis

La estructura espacial refleja el patrón de disposición de los árboles sobre el terreno y es un elemento básico para entender la dinámica de los ecosistemas forestales. El objetivo de la presente investigación fue evaluar las características estructurales bivariadas de cinco asociaciones diferentes de bosques de Pinus durangensis, identificando las similitudes y diferencias en la distribución bivariada de uniformidad de ángulos, dominancia y mezcla. Los datos provienen de cinco sitios cuadrados con superficie de 2500 m2, establecidos cada uno en diferentes bosques de P. durangensis en la Sierra Madre Occidental. Para cada sitio se determinó altura promedio, diámetro promedio y cobertura de copa, así como índices de mezcla de especies, uniformidad de ángulos y dominancia. Los índices se combinaron dos a dos para obtener tres distribuciones bivariantes. El bosque puro de P. durangensis presentó los individuos con mayor altura, mientras que el mayor diámetro fue para la asociación con P. teocote. El índice de mezcla (Mi) indica que solo en el bosque puro existe una baja mezcla de especies. El índice de uniformidad de ángulos (Wi) muestra que los árboles, de manera general, tienen una distribución aleatoria. Los valores de dominancia (Ui) muestran que en todos los sitios existen todas las clases sociales representadas de manera equitativa. Los índices y sus combinaciones describen adecuadamente la distribución espacial de los árboles y su relación con sus vecinos más cercanos. La información obtenida de la combinación de las variables estructurales contribuye a mejorar la comprensión de la estructura espacial del bosque y contribuye a la regulación de la intensidad de corta y garantizar una gestión sostenible.

Individual Tree Diameter and Height Growth Models for 30 Tree Species in Mixed-Species and Uneven-Aged Forests of Mexico

Lack of knowledge of individual tree growth in species-rich, mixed forest ecosystems impedes their sustainable management. In this study, species-specific models for predicting individual diameter at breast height (dbh) and total tree height (h) growth were developed for 30 tree species growing in mixed and uneven-aged forest stands in Durango, Mexico. Growth models were also developed for all pine, all oaks, and all other species of the genus Arbutus (strawberry trees). A database of 55,158 trees with remeasurements of dbh and h of a 5-year growth period was used to develop the models. The data were collected from 217 stem-mapped plots located in the Sierra Madre Occidental (Mexico). Weighted regression was used to remove heteroscedasticity from the species-specific dbh and h growth models using a power function of the tree size independent variables. The final models developed in the present study to predict dbh and total tree height growth included size variables, site factors, and competition variables in their formulation. The developed models fitted the data well and explained between 98 and 99% and of the observed variation of dbh, and between 77 and 98% of the observed variation of total tree height for the studied species and groups of species. The developed models can be used for estimating the individual dbh and h growth for the analyzed species and can be integrated in decision support tools for management planning in these mixed forest ecosystems.

High genetic diversity and stable Pleistocene distributional ranges in the widespread Mexican red oak Quercus castanea Née (1801) (Fagaceae).

The Mexican highlands are areas of high biological complexity where taxa of Nearctic and Neotropical origin and different population histories are found. To gain a more detailed view of the evolution of the biota in these regions, it is necessary to evaluate the effects of historical tectonic and climate events on species. Here, we analyzed the phylogeographic structure, historical demographic processes, and the contemporary period, Last Glacial Maximum (LGM) and Last Interglacial (LIG) ecological niche models of Quercus castanea, to infer the historical population dynamics of this oak distributed in the Mexican highlands. A total of 36 populations of Q. castanea were genotyped with seven chloroplast microsatellite loci in four recognized biogeographic provinces of Mexico: the Sierra Madre Occidental (western mountain range), the Central Plateau, the Trans‐Mexican Volcanic Belt (TMVB, mountain range crossing central Mexico from west to east) and the Sierra Madre del Sur (SMS, southern mountain range). We obtained standard statistics of genetic diversity and structure and tested for signals of historical demographic expansions. A total of 90 haplotypes were identified, and 29 of these haplotypes were restricted to single populations. The within‐population genetic diversity was high (mean h S = 0.72), and among‐population genetic differentiation showed a strong phylogeographic structure (N ST = 0.630 > G ST = 0.266; p < .001). Signals of demographic expansion were identified in the TMVB and the SMS. The ecological niche models suggested a considerable percentage of stable distribution area for the species during the LGM and connectivity between the TMVB and the SMS. High genetic diversity, strong phylogeographic structure, and ecological niche models suggest in situ permanence of Q. castanea populations with large effective population sizes. The complex geological and climatic histories of the TMVB help to explain the origin and maintenance of a large proportion of the genetic diversity in this oak species.

Morphology of two native catfishes from the Sierra Madre Occidental, México: I. pricei and Ictalurus sp. (Siluriformes: Ictaluridae)

Introduction: Morphotypes of native catfish of the genus Ictalurus (Siluriformes: Ictaluridae) are known to occur in allopatry in the northern Sierra Madre Occidental of Mexico, with only the Yaqui catfish (Ictalurus pricei) taxonomically described. Recent genetic analysis of these morphotypes has revealed the monophyly of the I. pricei complex, which indicates Ictalurus sp. from the Culiacán River and San Lorenzo River basins as its nearest genetic relative and recognizes as an evolutionarily significant unit the Culiacán River and San Lorenzo River morphotypes. Objective: To compare the meristic and morphometric characteristics of the catfish of the Culiacán River basin with its nearest genetic relative, the Yaqui catfish, in order to determine the presence of distinctive morphological characters that support genetic evidence previously reported for these morphotypes. Methods: Catfish specimens were collected during various field expeditions (1990-2012) to remote sites of the Sierra Madre Occidental and conducted in the Yaqui River and Culiacán River basins with the purpose of morphological comparison. Forty-five morphological characters (40 morphometric and five meristic) were examined in 76 adult specimens – 52 Ictalurus sp. and 24 Ictalurus pricei. Three groups were subject to a discriminant function analysis (DFA), including two Ictalurus sp. groups from the Humaya River and Tamazula River sub-basins, representing the Culiacán River basin, and one I. pricei group representing the Yaqui River basin. The standardized measurements and meristic data of the catfish morphotypes were compared by means of DFA. Results: The DFA revealed 12 characters to be significantly different (P &lt; 0.01) among the groups compared. The morphological characters separating the Ictalurus sp. (Culiacán River basin) from the Yaqui catfish were associated with lower anal, pelvic and pectoral fin ray numbers, shorter head and predorsal lengths, shorter longest lateral barbel and longest dorsal ray lengths and a narrower premaxilar dentary plate; and finally longer distances in Ictalurus sp. for dorsal-fin origin to last anal-fin ray base and dorsal-fin origin to posterior end of the adipose fin base. The standardized coefficients for canonical variables 1 and 2 accounted for 85.6 % and 14.4 % of the total variation, respectively. Conclusions: The distinctive morphological characters of the Ictalurus sp. found in the Culiacán River basin, combined with the known mitochondrial evidence for this morphotype, identify it as an evolutionarily significant unit that requires description as a new species based on taxonomical protocols.

Patterns of Density and Production in the Community Forests of the Sierra Madre Occidental, Mexico

The Mexican Sierra Madre Occidental (SMO) represents a region where hundreds of plant species reach the limits of their northern or southern range. The SMO also features a unique cultural diversity, and many communities living within the forest or in its close vicinity depend on the products and services that these forests provide. Our study was based on a large set of remeasured field plots placed in the forests of Durango which are part of the SMO. Using hierarchical clustering, three distinctly different forest types were identified based on structural differences and the relation between stem density and basal area. Maximum forest densities were estimated using a 0.975th quantile regression. Forest production (expressed as current periodic volume increment per unit of area and time) was estimated based on number of stems, forest density, mean height, and forest diversity. Forest density is the principal factors affecting periodic volume production. The discussion presented recommendations for the sustainable use of this unique natural resource. Maintaining minimum levels of residual density is key to ensuring the continued viability of the forests of the Mexican SMO. Future research is needed to identify optimum residual structures, productive residual densities, and desirable levels of biodiversity.