Genetic drift and gene flow in a prehistoric population of the Azapa valley and coast,Chile

The present paper studies the evolutionary process operating on prehistoric groups from the Azapa valley and coast (northern Chile). The sample consists of 237 crania from the Archaic Late, Early Intermediate, Middle, Late Intermediate, and Late periods. Six metric variables were used, which were transformed to eliminate the special environmental component and to increase the proportion of genetic variance. Population structure was assessed using a method based on quantitative genetic theory, which predicts a lineal relationship between average within-group phenotypic variance and group distance to the population centroid. Results indicate that 17.5% of the total variance accounts for special environmental variance. An excess in extraregional genetic flow is observed in the population corresponding to the Early Intermediate period in the valley. A reduced differentiation is observed between Archaic and Early Intermediate coastal groups, as well as between the latter and the inhabitants of the valley in the same period. Genetic differences between both areas increased substantially since the Middle period. Evidence indicates that long-range gene flow was lower on the coast than in the valley, the lowest estimated Fst being 0.0199 for the total population (coast and valley), 0.0111 for the coastal population, and 0.0057 for the valley. Results are discussed in terms of regional archeological and ethnohistorical evidence, and a microevolutionary model is presented to account for the biological history of the population.     

Nonmetric cranial trait variation and prehistoric biocultural change in the Azapa Valley, Chile

Historically, interpretations of both biological and cultural change within the prehistoric Azapa Valley, northern Chile, have cited large-scale population movements, with replacement from complex societies located in the adjacent highlands to the east. Biological estimates of this change have traditionally relied upon biodistance estimates, using craniofacial measures of both deformed and nondeformed skulls. In order to evaluate whether large-scale prehistoric migrations occurred in the Azapa Valley, we examine biodistance results from nonmetric cranial traits for eight mortuary samples that represent all time periods of prehistoric occupation of the valley. None of the mean measures of divergences (MMD) among mortuary samples examined by this study were significant. These results suggest biological continuity in the Azapa Valley during 5,000 years of prehistory, with nonsignificant gene flow during the late Middle Horizon (AD 750-1100) and Late Intermediate (AD 1100-1476) periods. Biodistance results also suggest endogamy within coastal and inland populations. The broader implications of these results are discussed.     

The genetic divergence of prehistoric populations of the south-central Andes as established by means of craniometric traits

The peopling of the south-central Andean region can be determined by exploring a combination of cultural, economic, and biological factors that influence the structure of populations and determine particular dispersals of gene frequencies. Quantitative characters from 1,586 adult crania of both sexes from northern Chile, northwestern Argentina, and the Cochabamba valleys in Bolivia were analyzed employing multivariate statistical analyses. Biological distances, representing phenotypic variation between these regions and their subregions, were studied within a population genetics framework. An analysis of Mahalanobis D(2) distances establishes two principle directions of interaction: the first between the Cochabamba valleys and northern Chile, and the second between the Cochabamba region and northwestern Argentina. The Chile and Argentina regions are shown to be less related to each other than each is to the Bolivian region. A higher mean genetic divergence is found for the entire region (F(ST) = 0.195); with northwestern Argentina having the highest spatial isolation (F(ST) = 0.143) and northern Chile the lowest (F(ST) = 0.061). These results allow us to propose a populating model based on the dispersion of several lines from a common ancestral population similar to those who inhabited the Cochabamba valleys. These lines differentiated themselves in time and space according to the effective size and the rate of gene flow, eventually producing the human groups which inhabited the valleys of northern Chile and northwestern Argentina.     

The Influence of Tiwanaku on Life in the Chilean Atacama: Mortuary and Bodily Perspectives

ABSTRACT  Using a contextualized bioarchaeological framework, in this article, I examine the complex relationship between the Tiwanaku polity of the Bolivian altiplano (C.E. 550–1000) and the inhabitants of the San Pedro de Atacama oases of northern Chile, in Tiwanaku's far periphery. I focus on how influences from Tiwanaku might have affected the presentation of Atacameño group identity in the mortuary context. I compare skeletal and mortuary data from 300 individuals buried during the peak of Tiwanaku influence in the Atacama to assess mortuary context, trauma, and body modifications. Results suggest a complex response to Tiwanaku influence. Data from the grave and mortuary assemblage reveal traditional Atacameño tombs with occasional foreign objects. Evidence of increased traumatic injury suggests that this relationship was not without some conflict. Finally, the maintenance of bodily expressions of local identity indicates a society that used their bodies to mark Atacameño identity.     

Stigmella epicosma (Meyrick) (Lepidoptera: Nepticulidae): first distribution records from Chile and first host plant record

The presence of Stigmella epicosma (Meyrick) is reported for the first time from two coastal valleys from northern Chile: Azapa and Chaca. Adults examined were reared from leafminer larvae on Trixis cacalioides (Asteraceae), the first host plant known for S. epicosma.     

Isotopic evidence for divergent diets and mobility patterns in the Atacama Desert,northern Chile,during the Late Intermediate Period (AD 900–1450)

The decline of the Tiwanaku state saw the emergence of two new cultures—Pica‐Tarapacá and Atacama—during the Late Intermediate Period in northern Chile. Archeological evidence suggests that both groups practised maize agriculture and pastoralism, but that their interaction zones differed significantly. Marine resources are common at Pica‐Tarapacá sites, even those far from coast, while Atacama sites in the desert oases and precordilleran area seem to have directed their networks towards the highlands. Here we apply stable carbon, nitrogen, and oxygen isotope analysis on human bone and enamel to test dietary patterns and residential mobility at two sites, Pica 8 and Quitor 6, representing the Pica‐Tarapacá and Atacama cultures, respectively. Our results show that diet at the two sites indeed differed: significant but variable consumption of marine resources and maize is indicated at Pica 8, despite being an inland site, while diet at Quitor 6 was based mainly on terrestrial resources. The use of seabird guano and llama dung as fertilizers and extreme aridity may have contributed to the high nitrogen isotope values observed in Pica 8 humans. The δ¹⁸O values in Pica 8 individuals are generally lower than for Quitor in spite of its greater distance from the Andes. All three isotopes suggest the presence of at least five nonlocals in the 30 measured at Pica 8. This evidence for human mobility is consistent with the high levels of trade and interaction observed in the archeological record, and begins to quantify the degree of movement of specific individuals. Am J Phys Anthropol 156:374–387, 2015. © 2014 Wiley Periodicals, Inc.     

Cranial morphological diversity of early,middle, and late Holocene Brazilian groups: Implications for human dispersion in Brazil

The history of human occupation in Brazil dates to at least 14 kyr BP, and the country has the largest record of early human remains from the continent. Despite the importance and richness of Brazilian human skeletal collections, the biological relationships between groups and their implications for knowledge about human dispersion in the country have not been properly explored. Here, we present a comprehensive assessment of the morphological affinities of human groups from East‐Central, Coastal, Northeast, and South Brazil from distinct periods and test for the best dispersion scenarios to explain the observed diversity across time. Our results, based on multivariate assessments of shape and goodness of fit tests of dispersion and adaptation models, favor the idea that Brazil experienced at least two large dispersion waves. The first dispersive event brought the morphological pattern that characterize Late Pleistocene groups continent‐wide and that persisted among East‐Central Brazil groups until recently. Within the area covered by our samples, the second wave was probably restricted to the coast and is associated with a distinct morphological pattern. Inland and coastal populations apparently did not interact significantly during the Holocene, as there is no clear signal of admixture between groups sharing the two morphological patterns. However, these results cannot be extended to the interior part of the country (Amazonia and Central Brazil), given the lack of skeletal samples in these regions. Am J Phys Anthropol 155:546–558, 2014. © 2014 Wiley Periodicals, Inc.     

Genetic variability and interpopulational differentiation of Artemia strains from South America

Seven Artemia samples from three South American countries (Chile, Brazil, Peru) were studied by starch electrophoresis with the aim of comparing levels of genetic variation and genetic similarity to representative populations of A. franciscana (San Francisco Bay, California, USA) and A. persimilis (Buenos Aires, Argentina), which are species endemic to the New World. Based on the analysis of 22 loci, parameters measuring genetic variability were, for some populations, found to be among the highest reported for Artemia so far. The percentage of polymorphic loci varied from 31.8% (Piura, Peru; Buenos Aires) to 50% (Los Vilos and Salar de Atacama, Chile), while the observed heterozygosity varied from 0.025 (Piura) to 0.165 (Los Vilos, Chile). A dendrogram based on Nei's genetic distance (D) produced four major groups. The Argentinian form, A. persimilis; the San Francisco Bay strain together with samples from Brazil (Macau and Rio Grande do Norte) and Chile (Pichilemu and Salar de Atacama); two coastal populations from Chile (Los Vilos and Iquique) and the sample from Peru (Piura). These four groups have inter-group D values that are, in some cases, far above those normally associated with conspecific populations.     

Megalorhipida leucodactyla (Fabricius) (Lepidoptera: Pterophoridae): first distribution record from Chile and new host plant record

The presence of Megalorhipida leucodactyla (Fabricius) (Lepidoptera: Pterophoridae) in Chile is reported for the first time from the Azapa valley, northern Chile. In this locality, some immature stages of M. leucodactyla were found to be associated with Tessaria absinthioides (Hook. & Arn.) DC., Asteraceae, a new host plant record at the species, genus and family level for M. leucodactyla.     

Phylogenetic and biogeographic relationships of the mouse opossum Thylamys (Didelphimorphia,Didelphidae) in southern South America

Nucleotide sequence data from the mitochondrial cytochrome b gene were used to evaluate the phylogenetic relationships among mouse opossum species of the genus Thylamys. Based on approximately 1000 bp in five of the six species of the genus and including different localities for some of the species, we concluded that T. macrura from the subtropical forests of eastern Paraguay is the most primitive taxon. Subsequent radiation of the genus is explained mainly via founder effect speciation. This evolutionary scenario would account for the speciation of T. pusilla, T. venusta, T. pallidior, and T. elegans in the Chaco, southern Bolivia and northern Argentina, the Andean Altiplano, the Coastal Desert of Chile, and coastal Perú, respectively. Calibration of a molecular clock set the Pleistocene as the period for the differentiation of Thylamys species. The molecular results confirm the strong genetic connection between populations that inhabit the "pre-cordillera" of northern Chile (T. pallidior) and the canyons that run through the Atacama Desert to the lowlands in northern Chile. Our results confirm the occurrence of two Thylamys species in Chile, T. pallidior and T. elegans, within and south to the Atacama Desert, respectively.     

Disrupted phylogeographical microsatellite and chloroplast DNA patterns indicate a vicariance rather than long‐distance dispersal origin for the disjunct distribution of the Chilean endemic Dioscorea biloba (Dioscoreaceae) around the Atacama Desert

Aim The Chilean endemic Dioscorea biloba (Dioscoreaceae) is a dioecious geophyte that shows a remarkable 600 km north–south disjunction in the peripheral arid area of the Atacama Desert. Its restricted present‐day distribution and probable Neogene origin indicate that its populations have a history linked to that of the Atacama Desert, making this an ideal model species with which to investigate the biogeography of the region. Location Chile, Atacama Desert and peripheral arid area. Methods Two hundred and seventy‐five individuals from nine populations were genotyped for seven nuclear microsatellite loci, and plastid trnL–F and trnT–L sequences were obtained for a representative subset of these. Analyses included the estimation of genetic diversity and population structure through clustering, Bayesian and analysis of molecular variance analyses, and statistical parsimony networks of chloroplast haplotypes. Isolation by distance was tested against alternative dispersal hypotheses. Results Microsatellite markers revealed moderate to high levels of genetic diversity within populations, with those from the southern Limarí Valley showing the highest values and northern populations showing less exclusive alleles. Bayesian analysis of microsatellite data identified three genetic groups that corresponded to geographical ranges. Chloroplast phylogeography revealed no haplotypes shared between northern and southern ranges, and little haplotype sharing between the two neighbouring southern valleys. Dispersal models suggested the presence of extinct hypothetical populations between the southern and northern ranges. Main conclusions Our results are consistent with prolonged isolation of the northern and southern groups, mediated by the life‐history traits of the species. Significant isolation was revealed at both large and moderate distances as gene flow was not evident even between neighbouring valleys. Bayesian analyses of microsatellite and chloroplast haplotype diversity identified the southern area of Limarí as the probable area of origin of the species. Our data do not support recent dispersal of D. biloba from the southern range into Antofagasta, but indicate the fragmentation of an earlier wider range, concomitant with the Pliocene–Pleistocene climatic oscillations, with subsequent extinctions of the Atacama Desert populations and the divergence of the peripheral ones as a consequence of genetic drift.     

Issues of affinity: Exploring population structure in the middle and regional developments periods of San Pedro de Atacama,Chile

The Middle Period (AD 400–1000) in northern Chile's Atacama oases is characterized by an increase in social complexity and regional interaction, much of which was organized around the power and impact of the Tiwanaku polity. Despite the strong cultural influence of Tiwanaku and numerous other groups evident in interactions with Atacameños, the role of immigration into the oases during this period is unclear. While archaeological and bioarchaeological research in the region has shown no evidence that clearly indicates large groups of foreign immigrants, the contemporary increase in interregional exchange networks connecting the oases to other parts of the Andes suggests residential mobility and the possibility that movement of people both into and out of the oases accompanied these foreign influences. Here, we analyze biodistance through cranial non‐metric traits in a skeletal sample from prehistoric San Pedro de Atacama to elucidate the extent of foreign influence in the oases and discuss its implications. We analyzed 715 individuals from the Middle Period (AD 400–1000) and later Regional Developments Period (AD 1000–1450), and found greater phenotypic differences between Middle Period cemeteries than among cemeteries in the subsequent period. We argue that this greater diversity extends beyond the relationship between the oases and the renowned Tiwanaku polity and reflects the role of the oases and its different ayllus as a node and way station for the Middle Period's myriad interregional networks. Am J Phys Anthropol 152:370–382, 2013. © 2013 Wiley Periodicals, Inc.     

Cosmic gourds: Cucurbit and Crescentia effigy pottery of coastal Ecuador

This paper treats the identification of modeled images of cucurbits —gourds and squash—in the ceramics of the Late Formative Era (or Chorrera culture) of coastal Ecuador (ca. 900 B.C. to 100 A.D.). These images provide good evidence for the sophisticated cultivation of cucurbits by the native peoples of the coast of South America from very early time periods in Ecuador. Their importance in the iconography of Late Formative cultures certainly demonstrates that the domestication of fruits with both hard and soft rinds must have been well established by the time ceramic production had begun. Depictions of combinations of animals with cucurbit-shaped bodies in the mortuary ceramics of the Late Formative period also demonstrate that cucurbits were an essential part of life (and death) on the coast of Ecuador.     

First record of the sedge feeder Bactra verutana Zeller (Lepidoptera: Tortricidae) in Chile based on morphology and DNA barcodes

The sedge-feeding moth Bactra verutana Zeller, 1875 (Lepidoptera: Tortricidae: Olethreutinae: Bactrini), described from Dallas, Texas, USA, is widespread, recorded throughout much North America, Central and South America, including the Caribbean, and Africa. The species is recorded for the first time from Chile based on specimens collected in the coastal valleys of the Atacama Desert, where its larvae feed on Cyperus corymbosus Rottb. var. subnodosus (Nees & Meyen) Kük. (Cyperaceae). A single DNA barcode haplotype, which is widespread in USA, was found in two Chilean specimens sequenced.     

External auditory exostosis in prehistoric Chilean populations: A test of the cold water hypothesis

Over one thousand prehistoric crania (n = 1,149) from northern Chile were analyzed to determine if the presence of external auditory exostosis (EAE) was a type of subsistence-induced pathology, a consequence of habitual fishing i the cold water of the Pacific Ocean, rather than genetically determined. To test this occupational hypothesis, the sample was divided according to chronology, type of economy, site elevation, and sex. The crania came from 43 sites, including the coast, lowland valleys (100–2,000 m), and highlands (2,000 to 4,000 m) with a time frame of 7,000 B.C. to the Inca era (1500 A.D.). There was a significant association between EAE, environment, and sex. The coastal inhabitants had the highest prevalence of EAE with 30.7% (103/336), followed by 2.3% (6/264) for the valley people and 0% (0/549) for highlanders. Coastal and valley men were significantly more affected than their female counterparts. Contrary to expectations, there was nonsignificant association between EAE and economy and/or chronology. In the Arica area, the early Chinchorro fishers, without agriculture, had 27.7% (26/94) EAE, the subsequent agro-pastoralists, 42.7% (32/75), and the late Arican agro-pastoral fishers had 35.6% (36/101) EAE. Apparently, with the advent of agriculture, the coastal Arican populations increased their ocean harvests, rather than decreased them, to gain a surplus in order to trade with nonmaritime groups. Am J Phys Anthropol 103:119–129, 1997. © 1997 Wiley-Liss, Inc.     

Of Maize and Men: A Critique of the Maritime Hypothesis of State Origins on the Coast of Peru

The adaptation of preindustrial band and tribal groups to environments subject to aperiodic downturns of long duration can often be understood by reference to limiting factors affecting the productivity of the subsistence system. This paper examines the two alternative hypotheses of the maritime and agricultural foundations of state society on the coast of Peru, and by reference to limiting factors affecting the Peru Coastal Current, argues that coastal maritime groups never advanced beyond an egalitarian tribal stage. Support for the acceptance of the alternative agricultural hypothesis of state origins is provided by an ecological analysis of relevant features of the marine and terrestrial biomes, ethnographic data on marine subsistence villages, and archaeological data for the Late Archaic and Formative periods . [Central Andes, state origins, coastal adaptations, ecological anthropology, limiting factors]     

Historical and ecological divergence among populations of Monttea chilensis (Plantaginaceae), an endemic endangered shrub bordering the Atacama Desert,Chile

The coastal deserts of northern Chile show an important latitudinal gradient of aridity with more arid areas to the north of the Atacama Desert than to the south. Several plant species have disjunct distributions that correspond with the extremes of this latitudinal gradient. In this study, using genetic (chloroplast and nuclear DNA), morphological (vegetative and floral traits of various kinds) and climatic and topographic information, we explored ecological and historical events that have putatively shaped patterns of variation among Monttea chilensis populations—a species that shows this disjunct distribution. Through phylogeographic and phylogenetic analyses, two divergent lineages were identified located at the latitudinal extremes. The lineage located northern lineage (NG) of the Atacama Desert showed more genetic diversity and better-resolved phylogeographic structure than the southern lineage (SG). Considerable morphological variation across the geographical range corresponds with these genetic groups. We observed contrasting relationships between floral and vegetative traits: populations from the most arid region NG possessed larger flowers, but smaller vegetative values, and vice versa. Niche modelling and multivariate analyses, including environmental data, revealed different environmental requirements for each lineage. NG plants occur in regions with warmer and drier climatic conditions and at higher altitudes, while SG populations inhabit colder and more humid environments and lower altitudes. The evolutionary history of M. chilensis exhibits a phylogeographical footprint consistent with past fragmentation and allopatric differentiation, where the hyper-arid zone formed by the Atacama Desert clearly acted as an important gene flow barrier. This barrier has led to considerable differentiation in morphology and ecology, resulting in two ecotypes or geographical races, suggesting incipient speciation promoted by local adaptation and geographical isolation.     

Paleogenetical study of pre‐Columbian samples from Pampa Grande (Salta,Argentina)

Ancient DNA recovered from 21 individuals excavated from burial sites in the Pampa Grande (PG) region (Salta province) of North‐Western Argentina (NWA) was analyzed using various genetic markers (mitochondrial DNA, autosomal STRs, and Y chromosomal STRs). The results were compared to ancient and modern DNA from various populations in the Andean and North Argentinean regions, with the aim of establishing their relationships with PG. The mitochondrial haplogroup frequencies described (11% A, 47% B, and 42% D) presented values comparable to those found for the ancient Andean populations from Peru and San Pedro de Atacama. On the other hand, mitochondrial and Y chromosomal haplotypes were specific to PG, as they did not match any other of the South American populations studied. The described genetic diversity indicates homogeneity in the genetic structure of the ancient Andean populations, which was probably facilitated by the intense exchange network in the Andean zone, in particular among Tiwanaku, San Pedro de Atacama, and NWA. The discovery of haplotypes unique to PG could be due to a loss of genetic diversity caused by recent events affecting the autochthonous populations (establishment of the Inca Empire in the region, colonization by the Europeans). Am J Phys Anthropol 2010. © 2009 Wiley‐Liss, Inc.