Human biology in Tlaxcala, Mexico: demography

A demographic survey was conducted as part of an ongoing population study of large Mestizo and Indian communities in Tlaxcala, Mexico. Comparative data on population structure and movement, mate selection, age at marriage, differential fertility, and mortality were collected through the administration of a standardized demographic proforma, and then cross-tabulated by computer analysis. The resulting differences between the Indian and Mestizo populations are interpreted in terms of the relative importance of hybridization, natural selection, and genetic drift. Sizeable variance in achieved reproduction and the high neonatal mortality suggest the operation of natural selection in these two populations. Observed patterns of population movement and mate selection indicate that the Mestizo population of the city of Tlaxcala is highly hybridized, in contrast to the endogamous Indian community of San Pablo del Monte.     

The agroecology of corn production in Tlaxcala,Mexico

The primary components of Tlaxcalan corn agriculture are described, including cropping patterns employed, resource management strategies, and interactions of human and biological factors. Tlaxcalan farmers grow corn in an array of poly-culture and agroforestry designs that result in a series of ecological processes important for insect pest and soil fertility management. Measurements derived from a few selected fields show that trees integrated into cropping systems modify the aerial and soil environment of associated understory corn plants, influencing their growth and yields. With decreasing distance from trees, surface concentrations of most soil nutrients increase. Certain tree species affect corn yields more than others. Arthropod abundance also varies depending on their degree of association with one or more of the vegetational components of the system. Densities of predators and the corn pest Macrodactylussp. depend greatly on the presence and phenology of adjacent alfalfa strips. Although the data were derived from nonreplicated fields, they nevertheless point out some important trends, information that can be used to design new crop associations that will achieve sustained soil fertility and low pest potentials.     

The Collection and Sale of Wild Mushrooms in a Community of Tlaxcala,Mexico

The Collection and Sale of Wild Mushrooms in a Community of Tlaxcala, Mexico. In this paper, we characterize the harvest and sale of wild mushrooms in Javier Mina (Tlaxcala state, Mexico) based on observations made during visits to that community during the rainy seasons of 1995 and 2001. While there, we visited the forests with various families of mushroom gatherers and also carried out 16 visits to a local mushroom broker to obtain information on the buying and selling of the mushrooms, including a list of the prices per kilo of the species that are sold commercially. Boletus cf. pinophilus, Lyophyllum cf. decastes, Hebeloma aff. mesophaeum and the Amanita caesarea complex were the highest–priced species, and were those collected in the greatest amounts. Our observations indicate that the gathering of mushrooms, a traditional activity among the people of Javier Mina, contributes, through the sale of the mushrooms, to the income of the community during the rainy season.

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Recolección y venta de hongos silvestres en una comunidad de Tlaxcala, México. Recolección y venta de hongos silvestres en una comunidad de Tlaxcala, México. El objetivo de este trabajo es describir el proceso de recolección y venta de hongos silvestres en Javier Mina, Tlaxcala. Para describir estas actividades se realizaron visitas a los bosques con varias familias recolectoras de hongos durante las épocas de lluvias de 1995 y 2001. Además, se realizaron 16 visitas a un distribuidor local para registrar información con respecto a la compra y venta de los hongos. Se obtuvo un listado de los precios por kilo de los hongos que se comercializan. Boletus cf. pinophilus, Lyophyllum cf. decastes, Hebeloma aff. mesophaeum y Amanita caesarea complex fueron los hongos recolectados en mayor cantidad durante este estudio, mismos que tuvieron los precios más altos de compra–venta. Se concluye que la recolección de hongos es una actividad tradicional para la gente de Javier Mina; sin embargo, la venta de éstos, contribuye a la obtención de ingresos durante la temporada de lluvias.

     

Apolipoprotein E polymorphism in the Indian and Mestizo populations of Mexico

Apolipoprotein E (APOE) genotypes were determined in 75 Mazatecan Indians and 83 Mexican mestizos. APOE allele and genotype frequencies in Mazatecans and mestizos were similar, with high frequencies of the APOE*3 allele (0.900 and 0.915, respectively) and the E3/3 genotype (0.813 and 0.831, respectively) and an absence in both samples of the APOE*2 allele. Our data are similar to those previously described for Mexican-American and Mayan populations, which show the highest frequency worldwide of the APOE*3 allele and the E3/3 genotype. Mazatecans and mestizos also show a decreased frequency of the APOE*4 allele when compared to other Amerindian groups. The absence of the APOE*2 allele has also been reported in other Amerindian groups such as Mayans and Cayapa, whereas in Caucasians the average frequency of this allele is about 8%. Our data are in agreement with previous reports showing absence of the APOE*2 allele in Native American groups. These findings suggest that the APOE*2 allele was absent in humans from northern Asia who settled in the Arctic and populated the American continent.     

Traditional knowledge about mushrooms in a Nahua community in the state of Tlaxcala, Mexico

This paper describes the traditional mycological knowledge of the Nahua of San Isidro Buensuceso, on the slopes of La Malinche Volcano National Park, in the state of Tlaxcala, México. The results described in this paper were obtained through interviews with villagers selected at random; a free-listing technique was used to determine the cultural significance of the mushrooms of the region. A total of 48 species, which had 65 Náhuatl names and 40 in Spanish, were identified. Although San Isidro villagers consider mushrooms to be a natural resource mainly used for food, they also use them for medicine, insecticides and trade. This paper presents traditional information on the morphology, ecology, fenology and consistency of the mushrooms found around San Isidro. It proposes that, from a cultural perspective, Gomphus flocossus, Ramaria spp. and Boletus spp. are the most important species of the region.     

A new dicrocoeliid (Digenea: Dicrocoeliinae) parasite of rodents from Tlaxcala, Mexico

Caballerolecythus ibunami n. gen., n. sp. is described from the intestine of 2 species of rodents (Liomys irroratus [Gray, 1868] and Peromyscus difficilis [Allen, 1891]) from Pi?onal, El Carmen Tequexquitla, Tlaxcala state, Mexico. These specimens represent a new genus and a new species of Dicrocoeliinae by possession of an extremely short ceca (ending at equatorial level of ovary); vitelline follicles that begin posterior to these structures, without overlapping; and a body that is long and slender (length/width ratio 1:17-21). To the best of our knowledge, this combination of characters has not been reported in other genera of this subfamily (Athesmia Looss, 1899; Unilaterilecithum Oshmarin in Skrjabin and Evranova, 1952; and Pseudathesmia Travassos, 1942).     

Endothelial nitric oxide synthase gene polymorphism in the Indian and Mestizo populations of Mexico

Endothelium-derived nitric oxide (NO) is an important factor in vasodilation synthesized by endothelial nitric oxide synthase (eNOS). A polymorphism (894 G to T) in exon 7 of the eNOS gene causes the conversion of Glu to Asp in position 298. The Glu298Asp polymorphism has been extensively associated with cardiovascular disease. We determined the Glu298Asp polymorphism frequency in healthy Mexican Mestizo, Huastec, Mayo, and Mayan populations by the endonuclease restriction method. The four populations analyzed were in Hardy-Weinberg equilibrium. Allele frequencies were similar among Mexican populations but different when compared with Caucasians. However, when compared with allele frequencies in Asian populations, Mestizo and Huastec allele frequencies were significantly different. Genotypically, only the Mestizos presented Asp298 homozygosity. The absence of double mutants in Indian populations resembles that in Asians. With these data, we conclude that the low frequency of the eNOS Glu298Asp polymorphism in Indian and Mestizo populations of Mexico is related to the Asian origin of Amerindian groups.     

Gender differences and regionalization of the cultural significance of wild mushrooms around La Malinche volcano, Tlaxcala, Mexico

The purpose of this study was to determine the cultural significance of wild mushrooms in 10 communities on the slopes of La Malinche volcano, Tlaxcala. The frequency and order of mention of each mushroom species in interviews of 200 individuals were used as indicators of the relative cultural significance of each species. A X(2) analysis was used to compare the frequency of mention of each species between males and females, and a Mann-Whitney U test was used to compare the difference in the total number of fungi mentioned by either gender. Traditional names for mushroom species were documented and frequency of mention assessed through multivariate statistics. The fungi with highest frequency of mention were Amanita basii, Lyophyllum decastes, Boletus pinophilus, Gomphus floccosus and Cantharellus cibarius complex. We found significant differences in the frequency of mention of different fungi by males and females but no significant difference was found for the total number of fungi mentioned by either gender. Principal component analysis suggested a cultural regionalization of La Malinche volcano communities based on preferences for consumption and use of traditional names. We observed two groups: one formed by communities on the eastern part of the volcano (with mixed cultures) and the other including communities on the western slope (ethnic Nahua towns). San Isidro Buensuceso is the most distinct community, according to the criteria in this study.     

Phylogenetic analysis of bacterial populations in waters of the former Texcoco Lake, Mexico

Molecular techniques were used to compare the compositions of the bacterial communities of the 2 following lagoons from the former soda Texcoco Lake, Mexico: the restored Facultativa lagoon and the Nabor Carrillo lagoon. Ribosomal intergenic spacer analysis (RISA) revealed that bacterial communities of the 2 lagoons were different and presented a relatively low diversity. Clone libraries of 16S rDNA genes were constructed, and significant phylotypes were distinguished by restriction fragment length polymorphism (RFLP). A representative clone from each phylotype was partially sequenced. Molecular identification and phylogenetic analyses based on ribosomal sequences revealed that the Facultativa lagoon harbored mainly gamma- and beta-Proteobacteria, low G+C Gram-positive bacteria, and several members of the Halobacteriaceae family of archaea. The Nabor Carrillo lagoon mainly included typical halophilic and alkaliphilic low G+C Gram-positive bacteria, gamma-Proteobacteria, and beta-Proteobacteria similar to those found in other soda lakes. Several probably noncultured new bacterial species were detected. Three strains were isolated from the Nabor Carrillo lagoon, their partial 16S rDNA sequences were obtained. On this basis, they were identified as Halomonas magadiensis (H1), Halomonas eurihalina (H2), and Staphylococcus sciuri (H3). This is the first study that uses molecular techniques to investigate potential genetic diversity in the Texcoco lakes. In this preliminary evaluation, we infer the presence of alkalophilic, halophilic, or haloalkaliphilic bacteria potentially useful for biotechnology.     

Human biology in Mexico. II. A comparison of blood group, serum and red cell enzyme frequencies, and genetic distances of the Indian populations of Mexico

Three hundred and ninety-five individuals from two populations from the State of Tlaxcala, Mexico, were studied in relation to the ABO, Rh, MNS, P, Kell, Lewis, Diego, Kidd, Duffy, Haptoglobin, Transferrin, Group specific component, Albumin, Acid Phosphatase and Phosphoglucomutase systems. One of the populations (San Pablo del Monte) is Indian, while the other (City of Tlaxcala) is Mestizo. The alleles which show variation in the Mestizo population are intermediate between the Spanish and the Indian gene frequencies. Three different genetic distance measures suggest that the Mestizo population is a triracial hybrid, while the Indian population is closely related to its two most proximal geographic neighbors, Vera Cruz and Puebla.     

Indian and Nation in Revolutionary Mexico

Indian and Nation in Revolutionary Mexico . Alexander S. Dawson. Tucson: University of Arizona Press, 2004. 240 pp.     

Gene diversity in Indian populations

Summary The phenotypes of glyoxalase I (GLO) were determined in a random population from Hessen (Germany) by high-voltage agarose gel electrophoresis. The gene frequencies in 1150 unrelated individuals were 0.4391 for GLO¹ and 0.5609 for GLO². Rare phenotypes were not observed. The segregation of phenotypes in 50 families and 32 mother-child combinations supports the assumed autosomal codominant inheritance. The possibility of a simultaneous typing for GLO, esterase D (EsD), and carbonic anhydrase₂ (CA₂) on one gel is discussed.     

Genetic distance analysis of twenty-two South American Indian populations.

Extent of genic variability among 22 tribal groups of South American Indians in terms of net codon differences per locus has been studied on the basis of determinations on ten genetic systems. The possibility of more than one (other than the north-south route, considered by others) migrational pattern is discussed in the light of the existing genetic variability among the Andean highland and the jungle populations. Genic similarities (as measured by gene identity) are related with geographic proximities which reflect the importance of random genetic drift in creating the present genic divergence among these population groups. Although the materials used in this paper form probably only a non-random sample of structural genome, intralocus variance (sampling) is found to contribute only a little in the variabilities of heterozygosity or genetic distance.     

Population and genomic lessons from genetic analysis of two Indian populations

Indian demographic history includes special features such as founder effects, interpopulation segregation, complex social structure with a caste system and elevated frequency of consanguineous marriages. It also presents a higher frequency for some rare mendelian disorders and in the last two decades increased prevalence of some complex disorders. Despite the fact that India represents about one-sixth of the human population, deep genetic studies from this terrain have been scarce. In this study, we analyzed high-density genotyping and whole-exome sequencing data of a North and a South Indian population. Indian populations show higher differentiation levels than those reported between populations of other continents. In this work, we have analyzed its consequences, by specifically assessing the transferability of genetic markers from or to Indian populations. We show that there is limited genetic marker portability from available genetic resources such as HapMap or the 1,000 Genomes Project to Indian populations, which also present an excess of private rare variants. Conversely, tagSNPs show a high level of portability between the two Indian populations, in contrast to the common belief that North and South Indian populations are genetically very different. By estimating kinship from mates and consanguinity in our data from trios, we also describe different patterns of assortative mating and inbreeding in the two populations, in agreement with distinct mating preferences and social structures. In addition, this analysis has allowed us to describe genomic regions under recent adaptive selection, indicating differential adaptive histories for North and South Indian populations. Our findings highlight the importance of considering demography for design and analysis of genetic studies, as well as the need for extending human genetic variation catalogs to new populations and particularly to those with particular demographic histories.     

Skin colour in north Indian populations

The skin colour of six endogamous groups of north India has been studied reflectometrically. The percentage reflectance at upper arm and forchead of 650 adult males (20–25 years) is described and discussed using 601 (425 nm), 605 (545 nm) and 609 (685 nm) filters of the “EEL” spectrophotometer. The inter-group heterogeneity is revealed by variance-ratio test. The t-test has been applied to study inter-group differences in pigmentation. Some correspondence has been found in skin colour with caste hierarchy, which holds only when the populations living in the same region are compared. These differences are assigned to adaptive adjustments superimposed by caste endogamy and assortative mating for skin colour.     

Mitochondrial genetic variation in European, African and Indian cattle populations

Mitochondrial DNA from representative animals of 13 different cattle breeds was assayed for restriction fragment length polymorphisms (RFLP) to determine phylogenetic relationships and levels of variation among breeds; 16 different mitotypes were found, described by 20 polymorphisms. Within these 16 mitotypes two major lineages were apparent: an Afro-European and an Asian type. These were found to differ at over 2.3% of sites surveyed. None of the mitotypes found in the Asian lineage was detectable in the Afro-European lineage and vice versa. Within each of the major mitotypes there were no further significant differences within or among breeds. Using rates of mitochondrial evolution estimated from other species, the two lineages were estimated to have diverged between 575000 and 1150000 years ago; well outside the 10000 years bp timeframe postulated by a single domestication hypothesis. The results presented are concordant with those generated in other studies and provide strong evidence for an independent domestication of Asian Bos indicus. Furthermore, the grouping of all African indicine populations within the clade containing all Bos taurus lineages points to the hybrid origins of the humped cattle of that continent.     

Reproductive indicators in natural populations of Douglas-fir in Mexico

The reproductive capacity in nine Mexican Douglas-fir populations was determined by analyzing seed production traits from 144 trees collected in 2001. Significant variation was found for all traits among populations; they contributed between 21% and 43% of total phenotypic variation found in these traits, indicating broad differences in reproductive capacity for that particular year. Seed efficiency (filled seed/seed potential) varied from 14% to 42% among populations; all populations from Central Mexico had a seed efficiency below 25%. The proportion of developed that were empty seeds varied from 0.40 to 0.81 among populations, whereas seed size varied also from 0.88 to 1.21 g per 100 seeds among them. Average ratio of filled seed weight to cone weight (reproductive efficiency) was 29.6 mg g⁻¹, but it varied three-fold between populations with extreme values. Populations with larger cones had greater seed potential and heavier seed but not necessarily higher reproductive or seed efficiency. Most reproductive indicators were significantly correlated with latitude, with lower values in the marginal populations from Central Mexico, in the southern extreme of the species range. Given these results, the need for conservation of Douglas-fir populations in Central Mexico is discussed.     

Indian genetic heritage in Southeast Asian populations

The great ethnolinguistic diversity found today in mainland Southeast Asia (MSEA) reflects multiple migration waves of people in the past. Maritime trading between MSEA and India was established at the latest 300 BCE, and the formation of early states in Southeast Asia during the first millennium CE was strongly influenced by Indian culture, a cultural influence that is still prominent today. Several ancient Indian-influenced states were located in present-day Thailand, and various populations in the country are likely to be descendants of people from those states. To systematically explore Indian genetic heritage in MSEA populations, we generated genome-wide SNP data (using the Affymetrix Human Origins array) for 119 present-day individuals belonging to 10 ethnic groups from Thailand and co-analyzed them with published data using PCA, ADMIXTURE, and methods relying on f-statistics and on autosomal haplotypes. We found low levels of South Asian admixture in various MSEA populations for whom there is evidence of historical connections with the ancient Indian-influenced states but failed to find this genetic component in present-day hunter-gatherer groups and relatively isolated groups from the highlands of Northern Thailand. The results suggest that migration of Indian populations to MSEA may have been responsible for the spread of Indian culture in the region. Our results also support close genetic affinity between Kra-Dai-speaking (also known as Tai-Kadai) and Austronesian-speaking populations, which fits a linguistic hypothesis suggesting cladality of the two language families.