Sergio Flores

Phylogenetic relationships among tribes in Xylocopinae (Apidae) and implications on nest structure evolution.

The subfamily Xylocopinae has been recognized as the most basal lineage within the family Apidae, comprising four tribes; Allodapini, Ceratinini, Xylocopini and Manueliini. Relationships among the tribes are not well resolved with morphological data. In particular, Manueliini and Xylocopini have each been placed as the most basal lineage in separate analyses of the subfamily. While relationships within each tribe, excepting Manueliini, have been investigated using molecular data, these data have not been applied to examine the relationships among tribes, which remain controversial. Here we present results of molecular phylogenetic analyses using sequences of CoI, Cytb and EF-1alphaF1 from members of the four tribes of Xylocopinae. We used available data from other studies in combination with data generated for the three species of Manueliini. Competing phylogenetic hypotheses regarding the alternate positions proposed to Manueliini and Xylocopini were evaluated through statistical tests. The basal position of either Manueliini or Xylocopini has contrasting implications on the evolutionary history of nest architecture, which mediates the potential for contact between adult and immature individuals. Our results indicate that Manueliini is the most basal lineage of Xylocopinae, in agreement with an evolutionary transition from nests having completely sealed cells to nests lacking cells. A nest structure with closed cells prevents physical interactions between adult and immature stages, whereas an open structure provides the opportunity for interactions that may play an important role in the emergence of sociality.

Fixations of the HIV-1 env gene refute neutralism: New evidence for pan-selective evolution

We examined 103 nucleotide sequences of the HIV-1 env gene, sampled from 35 countries and tested: I) the random (neutral) distribution of the number of nucleotide changes; II) the proportion of bases at molecular equilibrium; III) the neutral expected homogeneity of the distribution of new fixated bases; IV) the hypothesis of the neighbor influence on the mutation rates in a site. The expected random number of fixations per site was estimated by Bose-Einstein statistics, and the expected frequencies of bases by matrices of mutation-fixation rates. The homogeneity of new fixations was analyzed using χ² and trinomial tests for homogeneity. Fixations of the central base in trinucleotides were used to test the neighbor influence on base substitutions. Neither the number of fixations nor the frequencies of bases fitted the expected neutral distribution. There was a highly significant heterogeneity in the distribution of new fixations, and several sites showed more transversions than transitions, showing that each nucleotide site has its own pattern of change. These three independent results make the neutral theory, the nearly neutral and the neighbor influence hypotheses untenable and indicate that evolution of env is rather highly selective.

Brief Communication: Lactase Persistence and Dairy Intake in Mapuche and Mestizo Populations From Southern Chile

Lactase persistence (LP) occurs at a very low frequency in indigenous populations from Latin America, offering an opportunity to understand the relationship between this genetic trait and patterns of dairy consumption. Here, the frequency of LP is analyzed from Mapuche and -an adjacent- mestizo population inhabiting the Araucanía region. In addition to genotyping for LP, participants were surveyed in relation to general perception and consumption habits of dairy products. Low LP frequency (10%) and very low dairy intake was found among the Mapuche population as compared with Mestizo populations inhabiting Chile. The survey reported that the main reasons for avoidance of dairy were the gastrointestinal symptoms after dairy intake and cultural dietary habits. The interaction between low LP genotype frequency, low dairy intake, and sociocultural determinants is here discussed in the light of their potential health outcomes.

Lactase non-persistence and general patterns of dairy intake in indigenous and mestizo chilean populations.

Lactase persistence (LP) is a genetic trait that has been studied among different countries and ethnic groups. In Latin America, the frequencies of this trait have been shown to vary according to the degree of admixture of the populations. The objective of this study is to better understand the relationship between this genetic trait and dairy intake in a multiethnic context through a synthesis of studies conducted in four regions of Chile.

Adaptation to milking agropastoralism in Chilean goat herders and nutritional benefit of lactase persistence

The genetic trait of lactase persistence (LP) evolved as an adaptation to milking pastoralism in the Old World and is a well‐known example of positive natural selection in humans. However, the specific mechanisms conferring this selective advantage are unknown. To understand the relationship between milk drinking, LP, growth, reproduction, and survival, communities of the Coquimbo Region in Chile, with recent adoption of milking agropastoralism, were used as a model population.

Variabilidad Fenotípica en Maíz (Zea Mays) del Sitio de Caserones- I, Región de Tarapacá

En este articulo se analiza la variabilidad fenotipica del maiz en el sitio Caserones-1, comparando siete caracteres entre ejemplares pertenecientes a dos periodos: Formativo e Intermedio Tardio (cal. 20-1.020 d.C.). Considerando la antigua relacion entre esta especie y diversos grupos humanos en America (ca. 7.500 AP), asi como la tendencia generalizada a la disminucion de la variabilidad genetica como resultado de los procesos de seleccion y domesticacion, es que aqui ponemos a prueba la hipotesis de disminucion de la variabilidad fenotipica desde el Formativo al Periodo IntermedioTardio como consecuencia del manejo antropico. Los resultados aqui mostrados refutan la hipotesis anterior, describiendo un panorama inverso: de acuerdo al Analisis de Componentes Principales, la longitud es el atributo que presenta la transformacion mas intensa entre estos dos periodos, ampliando considerablemente su rango superior e incrementando la variabilidad alcanzada en el Formativo. Estos resultados aportan evidencia sobre las dinamicas de seleccion y manejo antropico por parte de algunas comunidades prehispanicas tarapaquenas, las que aqui son interpretadas como espacios de experimentacion agricola desde el Formativo Tardio.

Patrones de consumo y genotipos determinantes de la tolerancia al alcohol: estudio en estudiantes universitarios de Santiago de Chile

BACKGROUND Alleles involved in inefficient (ADH1B2*2 and ALDH2*2) or efficient (SNP6, ADH4 gene) alcohol metabolism may influence the risk of alcoholism. Alcoholism susceptibility has been classified as protector and risk-dependence phenotypes, associated with inefficient and efficient alcohol genetic metabolizing variants, respectively. AIM To investigate the possible association between genetic protective and risk-dependence variants and alcohol intake patterns. MATERIAL AND METHODS Saliva DNA samples were obtained and the AUDIT (Alcohol Use Disorders Identification Test) questionnaire was applied to 210 university students aged between 18 and 25 years old. RESULTS No statistically significant association between protective or risk-dependence genetic variants and alcohol pattern intake was detected. However, new categories of alcohol intake patterns-not included in the AUDIT questionnaire-were identified. CONCLUSIONS No association between the protector and risk-dependence phenotypes and patterns of alcohol consumption was detected in this sample of students.Background: Alleles involved in inefficient (ADH1B2*2 and ALDH2*2) or efficient (SNP6, ADH4 gene) alcohol metabolism may influence the risk of alcoholism. Alcoholism susceptibility has been classified as protector and risk-dependence phenotypes, associated with inefficient and efficient alcohol genetic metabolizing variants, respectively. Aim: To investigate the possible association between genetic protective and risk-dependence variants and alcohol intake patterns. Material and methods: Saliva DNA samples were obtained and the AUDIT (Alcohol Use Disorders Identification Test) questionnaire was applied to 210 university students aged between 18 and 25 years old. Results: No statistically significant association between protective or risk-dependence genetic variants and alcohol pattern intake was detected. However, new categories of alcohol intake patterns -not included in the AUDIT questionnaire- were identified. Conclusions: No association between the protector and risk-dependence phenotypes and patterns of alcohol consumption was detected in this sample of students.

Brief Communication: Lactase persistence and dairy intake in Mapuche and Mestizo populations from southern Chile: Lactase Nonpersistence and Diary Intake in Chile

Lactase persistence (LP) occurs at a very low frequency in indigenous populations from Latin America, offering an opportunity to understand the relationship between this genetic trait and patterns of dairy consumption. Here, the frequency of LP is analyzed from Mapuche and -an adjacent- mestizo population inhabiting the Araucanía region. In addition to genotyping for LP, participants were surveyed in relation to general perception and consumption habits of dairy products. Low LP frequency (10%) and very low dairy intake was found among the Mapuche population as compared with Mestizo populations inhabiting Chile. The survey reported that the main reasons for avoidance of dairy were the gastrointestinal symptoms after dairy intake and cultural dietary habits. The interaction between low LP genotype frequency, low dairy intake, and sociocultural determinants is here discussed in the light of their potential health outcomes.