Decrypting the Mitochondrial Gene Pool of Modern Panamanians

The Isthmus of Panama–the narrow neck of land connecting the northern and southern American landmasses–was an obligatory corridor for the Paleo-Indians as they moved into South America. Archaeological evidence suggests an unbroken link between modern natives and their Paleo-Indian ancestors in some areas of Panama, even if the surviving indigenous groups account for only 12.3% of the total population. To evaluate if modern Panamanians have retained a larger fraction of the native pre-Columbian gene pool in their maternally-inherited mitochondrial genome, DNA samples and historical records were collected from more than 1500 volunteer participants living in the nine provinces and four indigenous territories of the Republic. Due to recent gene-flow, we detected ∼14% African mitochondrial lineages, confirming the demographic impact of the Atlantic slave trade and subsequent African immigration into Panama from Caribbean islands, and a small European (∼2%) component, indicating only a minor influence of colonialism on the maternal side. The majority (∼83%) of Panamanian mtDNAs clustered into native pan-American lineages, mostly represented by haplogroup A2 (51%). These findings reveal an overwhelming native maternal legacy in today's Panama, which is in contrast with the overall concept of personal identity shared by many Panamanians. Moreover, the A2 sub-clades A2ad and A2af (with the previously named 6 bp Huetar deletion), when analyzed at the maximum level of resolution (26 entire mitochondrial genomes), confirm the major role of the Pacific coastal path in the peopling of North, Central and South America, and testify to the antiquity of native mitochondrial genomes in Panama

Organic Carbon Determination by the Walkley-Black and Dry Combustion Methods in SurfaceSoils and Andept Profiles from Costa Rica

Este artículo pertenece a la División S-3 -Microbiología y bioquímica de suelos de la Revista Soil Science Society of AmericaThe efficiency of oxidation of organic C by the Walkley-Black method was studied by comparing with determinations using dry combustion equipment and gravimetric determination for the evolved CO2. Fifty surface soils (0-30 cm) were studied, in groups of 10, each one belonging to one of the following taxonomic suborders: fluvents, Andepts, Tropepts, Udults and Ustults. Samples from 17 Andepts profiles were also analysed to study changes of oxidation efficiency with depth. The results for the surface samples indicated that the commonly used conversion factor was somewhat too small. It is recommended that 75% oxidation be used as the base for conversion to total C, as 86% of the studied samples deviated in <2% from this value. It was observed that the organic matter in the deeper horizons is more easily oxidized through the Walkley-Black procedure, perhaps because plant residues are less abundant and there is an accumulation of fulvic acids. In some cases the oxidation is almost complete. This oxidation is rather variable and it was not correlated with the texture or pH of these soils. It is believed that the extent of oxidizability can allow conclusions on the relative age of horizons in Andept profiles and indicates the presence of buried horizons.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Químic

Reactive Intermediates in the Photolysis of Furan, Thiophene and Pyrrole: The Dewar and the Ring Contraction forms

Five-member aromatic heterocycles have been known to undergo scrambling of the ring atoms upon photolysis. These reactions are characterized by their selectivity and several mechanisms have been proposed involving the intermediacy of a variety of isomeric structures, in particular, the Dewar and the ring-contracted forms. We have carried out a series of low-temperature argon-matrix photolysis and solution phase trapping experiments on the parent furan, thiophene and pyrrole in order to obtain evidence on the formation of these reaction intermediates.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Químic

Exploring the Y Chromosomal Ancestry of Modern Panamanians

<div><p>Geologically, Panama belongs to the Central American land-bridge between North and South America crossed by <i>Homo sapiens</i> >14 ka ago. Archaeologically, it belongs to a wider Isthmo-Colombian Area. Today, seven indigenous ethnic groups account for 12.3% of Panama’s population. Five speak Chibchan languages and are characterized by low genetic diversity and a high level of differentiation. In addition, no evidence of differential structuring between maternally and paternally inherited genes has been reported in isthmian Chibchan cultural groups. Recent data have shown that 83% of the Panamanian general population harbour mitochondrial DNAs (mtDNAs) of Native American ancestry. Considering differential male/female mortality at European contact and multiple degrees of geographical and genetic isolation over the subsequent five centuries, the Y-chromosome Native American component is expected to vary across different geographic regions and communities in Panama. To address this issue, we investigated Y-chromosome variation in 408 modern males from the nine provinces of Panama and one indigenous territory (the comarca of Kuna Yala). In contrast to mtDNA data, the Y-chromosome Native American component (haplogroup Q) exceeds 50% only in three populations facing the Caribbean Sea: the comarca of Kuna Yala and Bocas del Toro province where Chibchan languages are spoken by the majority, and the province of Colón where many Kuna and people of mixed indigenous-African-and-European descent live. Elsewhere the Old World component is dominant and mostly represented by western Eurasian haplogroups, which signal the strong male genetic impact of invaders. Sub-Saharan African input accounts for 5.9% of male haplotypes. This reflects the consequences of the colonial Atlantic slave trade and more recent influxes of West Indians of African heritage. Overall, our findings reveal a local evolution of the male Native American ancestral gene pool, and a strong but geographically differentiated unidirectional sex bias in the formation of local modern Panamanian populations.</p></div

Cocoteros en las Américas

It has been clearly established that the Portuguese introduced coconuts to the Cape Verde islands in 1499, and these supplied the Atlantic coasts and the Caribbean in the 1500s. By contrast, early 16th century reports of coconuts on the Pacific coast of Panama are controversial. Recent DNA analysis of modern coconut populations there shows them to be similar to Philippine varieties, agreeing with morphometric analysis. Hence, coconuts must have been brought by boat from the western Pacific, but no archaeological, ethnobotanical or linguistic evidence for pre-Columbian coconuts has been found. Thus, the most parsimonious explanation is that coconuts were introduced to Panama after Spanish conquest, as supported by DNA analysis and historical records of Spanish voyages. New collections along the Pacific coast, from Mexico to Colombia, are increasing the sampling for genetic analysis, and further work in the Philippines is suggested to test probable origins. Unless new archaeological discoveries prove otherwise, the strong hypothesis of Philippine origin should direct future research on the sources of American Pacific coast coconuts. © 2013 The New York Botanical Garden