Population Of Central Mexico Research Articles

Negative effects of agricultural open-channel irrigation system on vertebrate populations in central Mexico.

Linear infrastructures such as agricultural irrigation channels produce physical changes and negative impacts to habitats, wildlife populations, communities, and ecosystems. Open irrigation channels act as a pitfall for wildlife and can affect vertebrates of all sizes. Nonetheless, small channels have received relatively little attention by conservation biologists. The objective of this study was to analyze vertebrate species richness and mortality in relation to different sections of an irrigation channel system and the surrounding landscape characteristics. For two years, we conducted monthly surveys along an open-channel irrigation system to estimate its effect on vertebrates through records of dead and alive individuals. We examined the spatial relation of species richness and mortality with transects using a canonical correspondence analysis and chi-squared tests to determine possible variations in the different structures of the channel and seasonality. Further, a landscape diversity index was used to analyze the importance of surrounding habitat structure and composition on these parameters. Most vertebrates (61%) were found dead, small mammals and reptiles were the most affected. Our results indicate that mortality of small vertebrates varies depending on species, structures of the open-channel agricultural irrigation system (i.e., concrete channel and floodgates), seasonality (i.e., wet, and dry), and landscape heterogeneity (i.e., high, medium, and low landscape diversity). The open-channel irrigation system is a threat to populations of small vertebrates in anthropized landscapes, conservation efforts should be directed at protecting water bodies and restructuring the open-channel agricultural irrigation system to avoid mortality of species such as small rodents (M. mexicanus) and reptiles (C. triseriatus, B. imbricata, and Thamnophis spp.).

Prescriptions for the Control of a Clonal Invasive Species Using Demographic Models.

Until recently, little research has focused on determination of the population dynamics of invasive species and evaluating their genetic variation. Consequently, not much is known of what drives clonal invasive species and their demography. Here, we describe the population dynamics of Kalanchoe delagoensis (Crassulaceae), considered invasive to several countries. We quantified the demography of a population in central Mexico using integral projection models (IPM) in a population that reproduced asexually exclusively through plantlets. The effect of clonal recruitment on population growth rate () was evaluated by changing plantlet survival and simulating management scenarios that used previous data of watering and seven experimental herbicide treatments. The finite rate of population increase indicated that this Kalanchoe delagoensis population is growing (above one) and with water availability, growth rates will only accelerate. The IPM showed that plantlet survival and recruitment were the most critical steps in the cycle for the population, and simulations of different management scenarios showed that reducing plantlet survival significantly decreased only in two out of the seven herbicides used.

A Change in Conservation Status of Pachyphytum caesium (Crassulaceae), a Threatened Species from Central Mexico Based on Genetic Studies.

Simple SummarySpecies decline has accelerated in recent decades, with rare species often being the first to go extinct, mainly due to low population sizes. This study worked with Pachyphytum cesium (Crassulaceae), an endemic species from central Mexico threatened by human activities and climate change. To increase our knowledge of the species, we analyze the diversity and genetic structure of all known populations of P. caesium to change their current genetic status and propose conservation strategies. The results indicate that this species presents low to moderate levels of genetic diversity and incipiently structured populations due to low genetic flow. We found that genetic parameters are essential to the conservation strategies and status vulnerability reclassification. Based on our results, we propose reclassifying the conservation status of the species in danger of extinction; hence a series of conservation strategies are provided to prevent its disappearance.Genetic studies in rare species are important to determine their patterns of genetic diversity among populations and implement conservation plans aimed to reduce extinction risks. Pachyphytum caesium is an endemic species with extremely small populations in central Mexico. This work analyzes the diversity and genetic structure of Pachyphytum cesium (Crassulaceae) to change the conservation status and propose conservation strategies. Twelve dominant ISSR markers were used to describe the genetic diversity of all known populations. Additionally, we carried out two simulations to explore how the loss of individuals or the local populations extinction affect the genetics parameters of the species. The average results indicated moderate levels of genetic diversity (number of alleles = 89.7 ± 3.9, expected heterozygosity = 0.212 ± 0.0, and percentage of polymorphic loci = 56.1 ± 3.9), parameters that decreased significantly when simulations were performed in P. caesium. Additionally, a genetic structure of the populations was found with low gene flow (Nm = 0.92). Genetic parameters are negatively affected by the loss of individuals and the local extinction of populations. Based on our results, we propose to reclassify the conservation status of the species in danger of extinction, hence a series of conservation strategies are provided to prevent its disappearance.

The late Holocene Nealtican lava-flow field, Popocatépetl volcano, central Mexico: Emplacement dynamics and future hazards

Abstract Popocatépetl, one of the most hazardous volcanoes worldwide, poses significant threats for nearby populations in central Mexico. Therefore, it is important to reconstruct its eruptive history, including estimates of lava-flow emplacement times and their rheological properties. These studies define possible future eruptive scenarios and are necessary to mitigate the risk. Stratigraphic studies of the cal 350–50 B.C. Lorenzo Plinian pumice sequence indicate that effusive activity (Nealtican lava-flow field) occurred shortly after explosive activity, reflecting drastic changes in the eruptive dynamics. It was likely due to the efficient degassing of the magma during the Plinian phase and a decrease of magma ascent and decompression rates. Magma mixing, fractional crystallization, and a minor crust assimilation are the processes controlling the differentiation of the Nealtican lavas. We used lava chemical and mineralogical composition to estimate lava-flow viscosities, and used high-resolution elevation data to estimate emplacement times. Results indicate that lava viscosities of andesites and dacites ranged from 109 to 1012 Pa·s and emplacement durations were between ~1 and ~29 years, depending on the flow unit and morphological method employed. Considering the entire volume of emitted lava (4.2 km3) and a mean output rate of ~1 m3/s to ~15 m3/s, we estimated that the effusive phase that produced the Nealtican lava-flow field may have lasted ~35 years. This eruption had a considerable impact on pre-Hispanic settlements around the volcano, whose population exodus and relocation probably contributed to the rise of important cities in central Mexico, such as Teotihuacán and Cholula.

Echeandia cholulensis (Asparagaceae), una especie nueva del centro de México

Antecedentes y Objetivos: El género Echeandia (Asparagaceae) agrupa geófitas que caracterizan la flora de México. El grupo es endémico de América e incluye 85 especies, 74 de las cuales han sido encontradas en México y 63 son endémicas de este país. Su riqueza se concentra en la Zona de Transición Mexicana, incluido el Eje Volcánico Transmexicano (EVT). En este trabajo, se nombra y se describe a una especie nueva de Echeandia recolectada en el EVT en los estados de Puebla y Tlaxcala.Métodos: Recolectas en campo y revisión de ejemplares de herbario permitieron el descubrimiento de una especie nueva de Echeandia. Analizamos la morfología de ocho ejemplares de herbario y plantas vivas de dos poblaciones para describir el nuevo taxón y diferenciarlo de E. michoacensis y E. robusta. Por último, evaluamos su estado de conservación mediante el cálculo de la extensión de ocurrencia (EOO) y el área de ocupación (AOO) con la herramienta GeoCAT y basándonos en las categorías y criterios de la Lista Roja de la IUCN.Resultados clave: Describimos Echeandia cholulensis como una especie nueva de México. Se caracteriza por desarrollar los engrosamientos de las raíces alejados del cormo. Las hojas son lanceoladas, onduladas y glaucas. Produce flores ascendentes con tépalos blancos, filamentos clavados y muricados y anteras libres con dehiscencia longitudinal. Se conoce de tres poblaciones en el centro de México, en los estados de Puebla y Tlaxcala.Conclusiones: En el EVT, el volcanismo ha generado variación topográfica y climática que favorece la especiación y persistencia de las plantas. El descubrimiento y descripción morfológica de Echeandia cholulensis ejemplifican lo anterior. La exploración botánica y la revisión de los ejemplares de herbario podrían resultar en el descubrimiento de especies nuevas que aumenten la riqueza florística del EVT.

Female choice and male aggression in the polymorphic lizard Sceloporus minor

AbstractIn comparison with some other vertebrate groups, female choice in lizards is relatively poorly understood. In contrast, aggressive behavior in lizards has been better studied; nevertheless, there are many genera and even whole families for which little or no information on aggressive behavior has been described. Therefore, the objective of this study was to experimentally evaluate the importance of morphometric traits, body coloration, and behavioral attributes of male Sceloporus minor from a population in central Mexico in order to (1) determine whether female choice exists in this species, and if so, identify which features of males females are using to do so, and (2) identify the phenotypic features of males that predict dominance status in contests between dominant and subordinate males. We found that females of S. minor indeed show a preference for males on the basis of ventral patch color; specifically, females chose males with ventral patches of Spectrum Blue or True Blue over males with ventral patches of other blue hues, but found no evidence of choice based on other morphological characters examined. Results also showed that winner (i.e., dominant) males exhibited more aggressive behaviors and were larger in body size than subordinate (i.e., loser) males. Notably, we found no support for a role of male polymorphic dorsal coloration on either female choice or male contest outcome. The results of this study showed evidence of female choice and male‐male competition, suggesting that in this population, males exhibit intrasexual interactions to compete for resources such as territories and produce displays that serve in part to attract females.

Factors affecting the abundance of Peters’s squirrel, Sciurus oculatus, in a population of Central Mexico

Peters’s squirrel, Sciurus oculatus , is an endemic species distributed in fragmented populations in Central Mexico, which is one of the most densely populated areas in Mexico. No study has estimated the abundance of this species yet, and the effects of human-environmental factors on its abundance and distribution are unknown. Understanding the role of these factors on its abundance is crucial to its management and conservation. We used the Royle-Nichols model to estimate the abundance and detection probability with detection-non-detection data collected from a camera trap survey. The human-environmental factors that might influence the abundance and distribution of squirrel were modeled. Distance to nearest human settlements had a positive effect on abundance; meanwhile, the presence of the main predator species of the squirrel was a negative factor for detection probability. These findings suggest less abundance or/and a decrease in-ground use in areas with the presence of predators and nearest to human settlements. These results indicate the negative effect of human activities on squirrel abundance and the possible anti-predatory behavior of Peters’s squirrel.

ОПИСИ КУЛЬТУ АЦТЕКСЬКОГО БОГА ТЕСКАТЛІПОКИ У ДЖЕРЕЛАХ ІСПАНСЬКОГО ПОХОДЖЕННЯ

The author of the article aims to conduct a comprehensive analysis of sources of Spanish origin, since they constitute the most significant category of documents used by Amerindologists. At the same time, it draws attention to the historiography of the topic. Conditionally, it is divided into two groups: works that highlight the general features of the entire pantheon of Aztecs and those that analyze the cult of Tezcatlipoca itself and its characteristics. The use of the linguistic method in connection with the names of Tezcatlipoca allows us to understand the functions that the Aztecs bestowed on this god and more accurately interpret the mentioned deity. Particular attention is paid to the translation of Nahuatl names and the explanations given by the authors of the sources. Comparing the names of the god and the descriptions of his cult, created after the conquest, allows us to trace how the Europeans could at their own discretion treat Tezcatlipoca as an individual representative of the pantheon and how the autochthonous population of central Mexico saw it. In addition to the analysis of names, the paper reviews the main holidays in honor of Tezcatlipoca, compares the testimony of different sources on this occasion. In this context, the prayers and typical sacrifices of the worship of this god are analyzed. This allows to expand the range of ideas about the essence and functions of Tezcatlipoca, as well as to trace the various local variants of his cult within central Mexico The article also explores the legends that cite sources of Spanish descent about Tezcatlipoca. Because of this, two different traditions of mythological tradition about the mentioned god were distinguished. One is likely to relay events in the history of Tollan in the form of a legend, while the other reflects representations of the creating of the world and the role of Tezcatlipoca in this. Moreover, the first variant of the myth of the mentioned god has differences in different sources of Spanish origin, which allows for a more thorough analysis of these testimonies. Further development of the problematic issue is to attract sources of pre-colonial age, which will help to create a more thorough understanding of this cult.

Does florivory affect the attraction of floral visitors to buzz-pollinated Solanum rostratum?

Floral herbivory (florivory) can directly and indirectly affect plant reproduction through the loss of ovules or seeds and by reducing the visitation by pollinators through the reduction in flower attractiveness, respectively. We studied the effect of florivory on pollinator visitation in a buzz-pollinated herb. We used Solanum rostratum as the study model because its specialised morphology, heterantherous flowers that emit floral scents, demands a close association with its pollinators (buzzing bees). We hypothesized that when florivores consume the attractive structures (corolla and rewarding anthers), the pollinators would visit the damaged flowers less often, indirectly affecting S. rostratum reproductive success. Furthermore, we hypothesized that consumption of the reproductive structures (pollinating anther and pistil) would directly affect the plants reproductive success. We conducted observations of three S. rostratum populations in central Mexico. We observed twelve species of florivore consuming S. rostratum flowers. Florivores preferred to consume the attractive structures (corolla) over reproductive structures. However, they preferred to consume the anthers specialised for feeding pollinators over the anthers specialised for pollination. In addition, we recorded floral volatiles emitted by flowers damaged by florivory using solid-phase microextraction coupled with gas chromatography–mass spectrometry. We identified 25 volatile compounds in S. rostratum flowers, mainly aromatic, monoterpene and sesquiterpene compounds. The relative proportions of these compounds differed between undamaged and damaged flowers. Bioassays showed that both legitimate visitors (pollinators) and illegitimate visitors (thieves) visited undamaged flowers more often than flowers damaged by florivores; however, the decrease in visitation frequency did not affect fruit and seed production. In conclusion, the consumption of attractive (corolla) and reward floral structures (feeding anthers) reduced the frequency of visits by pollinators but does not affect S. rostratum reproductive success (fruit and seed set) probably because reproductive structures (pistil and pollinating anthers) are less often consumed.

Genetic Variation among Island and Continental Populations of Burrowing Owl (Athene cunicularia) Subspecies in North America

Burrowing Owls (Athene cunicularia) have a large geographic range spanning both North and South America and resident populations occur on many islands in the eastern Pacific Ocean and the Caribbean Sea. Many owl populations are isolated and disjunct from other populations, but studies on genetic variation within and among populations are limited. We characterized DNA microsatellite variation in populations varying in size and geographic isolation in the Florida (A. c. floridana), the Western (A. c. hypugaea), and the Clarion (A. c. rostrata) subspecies of the Burrowing Owl. We also characterized genetic variation in a geographically isolated population of the western subspecies in central Mexico (near Texcoco Lake). Clarion Burrowing Owls had no intrapopulation variation (i.e., fixation) at 5 out of 11 microsatellite loci, a likely outcome of genetic drift in an isolated and small population. The Florida subspecies had only polymorphic loci but had reduced levels of genetic variation compared with the more-widespread western subspecies that occurs throughout western North America. Despite the extensive geographic distribution of the Western Burrowing Owl, we found genetic differentiation between the panmictic population north of the Trans-Mexican Volcanic Belt and the resident Texcoco Lake population in central Mexico.

Validation of a non-laboratorial questionnaire to identify Metabolic Syndrome among a population in central Mexico.

ABSTRACTObjectiveTo determine the reliability of a non-laboratorial questionnaire, the Encuesta de Identificación de Sujetos Metabólicamente Comprometidos en Fase-I (ESF-I) for identifying Metabolic Syndrome among a population in central Mexico.MethodsClinical and biochemical parameters were collected for 232 participants from 1 June 2012 – 31 August 2013. Three definitions of Metabolic Syndrome (Harmonizing, National Cholesterol Education Program Expert Panel and Adult Treatment Panel III [ATPIII], and International Diabetes Federation [IDF]) were used to allocate subjects to either the normal or Metabolic Syndrome positive (MetS+) group. The predictability of the questionnaire was determined by the Area-Under-the-Receiver-Operating Characteristic curve (AUC). Youden's index was calculated and the highest score was considered the optimal cutoff value. Cohen´s kappa (κ) was calculated to determine the level of agreement between the ESF-I questionnaire (max score: 15 based on 15 items) and Metabolic Syndrome.ResultsFrom 53.8% – 60.7% of the participants were determined to be MetS+. The average questionnaire score was significantly higher in the MetS+ group for each definition (4.0 vs. 8.0, P < 0.05). The ESF-I questionnaire was predictive for the Harmonizing definition (AUC = 0.841, 95%CI: 0.790 – 0.892), the ATPIII definition (AUC = 0.827, 95%CI: 0.774 – 0.880), and the IDF definition (AUC = 0.836, 95%CI: 0.785 – 0.887). A cutoff value of 7 was determined for each definition; therefore, the cohort was re-categorized based on questionnaire results. There was a strong agreement between the ESF-I questionnaire and MetS (Harmonizing: accuracy = 77.6%, κ = 0.554; ATPIII: accuracy = 74.1%, κ = 0.489; IDF: accuracy = 74.6%, κ = 0.495, P < 0.001).ConclusionThe ESF-I questionnaire can identify MetS+ patients, and therefore, lead to earlier diagnoses, reduced number of consultations, and lower costs with easier application.

ESTRUCTURA SILVÍCOLA DE POBLACIONES DE Pseudotsuga menziesii (Mirb.) Franco EN TLAXCALA Y PUEBLA

&#x0D; &#x0D; &#x0D; Las poblaciones de Pseudotsuga menziesii del centro de México son pequeñas, fragmentadas y están afectadas por diversos factores de disturbio: naturales y de origen humano. El escaso conocimiento sobre su estructura silvícola limita el diseño de programas de manejo, a pesar del estatus de protección especial de la especie. Los objetivos del presente estudio fueron caracterizar, comparar y analizar la estructura silvícola de siete poblaciones de Pseudotsuga localizadas en los estados de Tlaxcala y Puebla. La información se obtuvo mediante un muestreo sistemático, con parcelas circulares anidadas de 0.1, 0.05 y 0.005 ha, en las que se registró el diámetro normal de los árboles vivos, muertos y tocones de todos los individuos arbóreos existentes. Los resultados del área basal y valor de importancia indican que en las localidades dominan Pseudotsuga menziesii-Quercus sp., y en menor proporción se identificaron coníferas como Abies religiosa. Las distribuciones diamétricas de Pseudotsuga son irregulares y desbalanceadas, con notable carencia de diámetros pequeños (&lt; 10 cm) y superiores a 85 cm. Los tres sitios de Tlaxcala mostraron mayores densidades de árboles muertos en pie y tocones que los de Puebla. . La similitud entre rodales, evaluada con el Índice de Morisita modificado, reflejó una influencia de la cercanía geográfica de los rodales, pero también sugiere la incidencia importante de factores de disturbio en el desarrollo de las distribuciones diamétricas observadas en las poblaciones.&#x0D; &#x0D; &#x0D;

Puma (Puma concolor), a top predator in Sierra del Tentzo Nature Reserve in Central Mexico

The puma ( Puma concolor ) is the felid with the broadest distribution in America and plays a key role in the environment. However, there is scarce information about the species, as well as on how habitat loss, prey depletion and hunting have affected puma population along its range. Thus, it is imperative to generate information on the presence and distribution of puma in highly fragmented habitats like Central Mexico. We conducted a camera trapping survey to determine deer densities during September 2012 along trails in remnants of oak forest near the town of San Nicolas Huajuapan in the municipality of Huehuetlan el Grande, Puebla (18° 46ʹ 57.18ʺ N, -98° 07ʹ 18.95ʺ W). A photograph of an adult puma of undetermined sex was obtained at 00:32 hours on September 16 near a dry river bed at 1,680 masl. During the same season, we also captured other species like white tailed deer ( Odocoileus virginianus ), ringtail ( Bassariscus astutus ), coyote ( Canis latrans ) and grey fox ( Urocyon cinereoargenteus ). This record is important as the closest protected area presumably inhabited by puma is the Izta-Popo Nature Reserve; other sightings have also been recorded in the Mixteca Poblana and the Tehuacan-Cuicatlan Biosphere Reserve. This record is noteworthy because the species distribution in the state is unknown. A distance analysis showed that this site is relevant for connecting different puma populations in Central Mexico.

Reproductive Traits of Dusky Rattlesnakes (Crotalus triseriatus) in Central Mexico

Abstract Reproductive aspects of most snake species remain elusive because of secretive habits or rarity. Here, we report data on litters of Crotalus triseriatus from two populations in central Mexico. We made 4-d visits to both study sites every other week from April to June during 2014 and 2015 (Site 1) and during 2015 (Site 2). Surveys were made from 0900 to 1800 h to catch as many gravid females as possible. All adult females were maintained in captivity until parturition. We recorded a total of 16 litters (10 from Site 1 and six from Site 2). Average litter size was 7.2 ± 2.2 (n = 13), higher than previously reported in the species. We found no relationship between maternal snout–vent length (SVL) and litter size, and litter size did not differ between study sites or years. In contrast with other studies, we found no relationship between neonate SVL, body mass, and litter size or between maternal and neonatal traits. Dusky Rattlesnakes demonstrate a plastic reproductive response to changing environme...

Genetic Diversity and Distribution of Blastocystis Subtype 3 in Human Populations, with Special Reference to a Rural Population in Central Mexico.

Blastocystis subtype 3 (ST3) is a parasitic protist found in the digestive tract of symptomatic and asymptomatic humans around the world. While this parasite exhibits a high prevalence in the human population, its true geographic distribution and global genetic diversity are still unknown. This gap in knowledge limits the understanding of the spread mechanisms, epidemiology, and impact that this parasite has on human populations. Herein, we provided new data on the geographical distribution and genetic diversity of Blastocystis ST3 from a rural human population in Mexico. To do so, we collected and targeted the SSU-rDNA region in fecal samples from this population and further compared its genetic diversity and structure with that previously observed in populations of Blastocystis ST3 from other regions of the planet. Our analyses reveled that diversity of Blastocystis ST3 showed a high haplotype diversity and genetic structure to the world level; however, they were low in the Morelos population. The haplotype network revealed a common widespread haplotype from which the others were generated recently. Finally, our results suggested a recent expansion of the diversity of Blastocystis ST3 worldwide.

Natural selection drives chemical resistance of Datura stramonium.

Plant resistance to herbivores involves physical and chemical plant traits that prevent or diminish damage by herbivores, and hence may promote coevolutionary arm-races between interacting species. Although Datura stramonium’s concentration of tropane alkaloids is under selection by leaf beetles, it is not known whether chemical defense reduces seed predation by the specialist weevil, Trichobaris soror, and if it is evolving by natural selection. We measured infestation by T. soror as well as the concentration of the plants’ two main tropane alkaloids in 278 D. stramonium plants belonging to 31 populations in central Mexico. We assessed whether the seed predator exerted preferences on the levels of both alkaloids and whether they affect plant fitness. Results show great variation across populations in the concentration of scopolamine and atropine in both leaves and seeds of plants of D. stramonium, as well as in the intensity of infestation and the proportion of infested fruits by T. soror. The concentration of scopolamine in seeds and leaves are negatively associated across populations. We found that scopolamine concentration increases plant fitness. Our major finding was the detection of a positive relationship between the population average concentrations of scopolamine with the selection differentials of scopolamine. Such spatial variation in the direction and intensity of selection on scopolamine may represent a coevolutionary selective mosaic. Our results support the view that variation in the concentration of scopolamine among-populations of D. stramonium in central Mexico is being driven, in part, by selection exerted by T. soror, pointing an adaptive role of tropane alkaloids in this plant species.

Prevalence and predictors of alanine aminotransferase elevation among normal weight, overweight and obese youth in Mexico

This study aimed to determine the prevalence of and risk factors associated with elevated alanine aminotransferase (ALT) levels among a sample of normal weight, overweight and obese youth from two urban populations in Central Mexico. Baseline data from 1262 youth aged 8-19 years who participated in the Mexican Health Worker Cohort Study from March 2004 to April 2006 were reviewed, including 680 girls and 582 boys, with a total of 83 participants with elevated ALT level (>40 U/L). Information was obtained from self-administered questionnaires, anthropometric results and clinical measurements. Associations of interest were examined using multivariate logistic regression models. A total of 3.8% of girls and 9.8% of boys had elevated ALT levels. Elevated ALT was observed in 28.9% of the obese and 14.2% of the overweight participants. Metabolic syndrome (MS) occurred in 6.1% of the study population and those with MS had a high percentage of elevated ALT (14.5% of girls and 40.0% of boys, respectively). Abdominal obesity and insulin resistance were also associated with a greater risk of elevated ALT. Obesity and certain metabolic risk factors are important predictors for elevated ALT. Screening for ALT levels in obese youth could help to identify those at risk and reduce the possibility of future liver diseases.

Influence of the geological history of the Trans‐Mexican Volcanic Belt on the diversification of Nolina parviflora (Asparagaceae: Nolinoideae)

AbstractAimOur aims were to determine the pattern of genetic variation in the endemic shrub Nolina parviflora, and to evaluate the influence of the geological history of the Trans‐Mexican Volcanic Belt (TMVB) and nearby mountainous regions on plant population divergence.LocationTrans‐Mexican Volcanic Belt, Sierra Madre Occidental, Sierra Madre Oriental and Sierra Madre del Sur mountain ranges in Mexico.MethodsTwenty‐eight populations (210 individuals) were sequenced for one nuclear (rpb2) and two chloroplast (trnL–F and psbA–trnH) DNA markers. Intraspecific phylogenetic relationships among haplotypes were reconstructed, and molecular dating, population genetic analyses and group testing were performed on the data. Isolation‐by‐distance analysis was conducted for the populations spanning the distribution of the species.ResultsTwenty‐four chloroplast marker haplotypes and 36 rpb2 haplotypes were recovered from the populations sampled. The combined marker phylogeny indicates the presence of two well‐supported clades within the N. parviflora populations. Clade 1 includes populations from Jalisco and Zacatecas and Clade 2 comprises the remaining populations. We found an east–west geographical pattern of chloroplast DNA (cpDNA) haplotype distribution, indicating a lack of gene flow between these two regions. Divergence time estimates indicate an Oligocene to mid‐Miocene divergence between Nolina and Dasylirion. Divergence estimates for Clade 1 are from the mid‐Miocene to early Pleistocene, and for Clade 2 from the early Miocene to mid‐Pliocene. Values of cpDNA GST (0.702) indicate a strong population structure and differentiation. A spatial analysis of molecular variance indicates 11 groups among the sampled populations and detects various well‐supported geographical barriers.Main conclusionsDivergence time estimates suggest a correlation between the time of divergence between distinct N. parviflora populations and periods of uplift in the TMVB. We infer that the orogeny of this mountain range played an important role in driving the diversification of plant populations in central Mexico by creating topographical barriers that limited gene flow.

What can the demography of Astrophytum ornatum tell us of its endangered status?

The Cactaceae are prominent members of national and international endangered species lists. This is true for even those that have not been studied in any significant detail, and given the need to assess these species there is still a general lack of information. Demographic studies in the Cactaceae have highlighted several threats some of which are clearly human induced (disturbance), and others that have a biological component (e.g. low survival rates of seedlings). We modelled the population dynamics of Astrophytum ornatum (the southernmost representative of Astrophytum) in one population in central Mexico, during a three year period. We constructed two size classified transition matrices and determined the growth rate (λ), as well as the stochastic log growth rate. We simulated changes in the matrix elements that correspond to the seed bank and the seed-seedling transition as these were the most important bottlenecks to population growth. In both years, the growth rate indicates a declining population, which will face serious problems in the next 2 to 3 decades. The simulations show that the seed bank is not as important as the seed-seedling transition. Any program that aims to restore A. ornatum populations needs to enhance seedling establishment.

Phylogeography of the Barred Owl (Strix varia): Species limits, multiple refugia, and range expansion

ABSTRACT. The Barred Owl (Strix varia) is a common nonmigratory owl distributed across southern Canada, south to California in the west, and to Texas and Florida in the east, with isolated populations in central Mexico. We examined the genetic structure of Barred Owl populations throughout their range using 500–600 base pairs each of one nuclear and three mitochondrial genes. In 75% of the shortest trees and 64% of the bootstrapped trees, Barred Owls were not monophyletic; rather, S. v. sartorii of Mexico was separated from the remaining taxa of S. varia by S. fulvescens of Central America. Consequently, the Barred Owls of Mexico are a species-level taxon. There was a large component (32%) of genetic variance distributed among population samples from the United States and Canada because of the occurrence of two clades of haplotypes (4.8% sequence divergence) with differing geographic distributions. One clade was predominant along the Atlantic Coast and the second in the south-central United States. The tw...