Home About us Contact
|
Home About us Contact | ||
|
|
||
South American Populations (south + american_population)
Selected AbstractsA COMPREHENSIVE STUDY OF THE LIFE CYCLE OF A SOUTH AMERICAN POPULATION OF STIGEOCLONIUM TENUE (CHAETOPHORALES, CHLOROPHYTA),JOURNAL OF PHYCOLOGY, Issue 5 2010Karina M. Michetti The diplobiontic,haplodiplontic life cycle with alternating isomorphic generations in Stigeoclonium tenue (C. Agardh) Kütz. is described for the first time. Sporophytes (2n = 10) arise from tetraflagellate zoospores that are produced by meiosis. Sporic meiosis might be inferred from the cruciform divisions formed during zoosporogenesis and is confirmed through observations of prophase I substages. Zoospores do not germinate directly but produce a haploid cyst that germinates to give rise to a gametophyte (n = 5). Gametophytes produce biflagellate isogametes, which fuse to produce zygotes that germinate by mitosis into the sporophytic stage. Gametophytes and sporophytes reproduce asexually both via mitotic tetraflagellate zoospores and by thallus fragmentation. Results from this study indicate that both the cosmopolitan distribution and dominance of S. tenue in many periphytic communities might be due to its multiple reproductive strategies. [source] Liriomyza huidobrensis in Yunnan, China: current distribution and genetic structure of a recently established populationENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2002Liping He Abstract Liriomyza huidobrensis Blanchard (Diptera: Agromyzidae) is a very serious and economically important pest around the world. Liriomyza huidobrensis in China was first reported from Kunming of Yunnan province in 1993. We report here that this pest has recently expanded its distribution, along with a host plant range extension and population explosion. The mitochondrial cytochrome oxidase II gene was sequenced for eight populations from Yunnan. All individuals were identical: no genetic variation was observed between populations either from different geographical localities or from different host plants. The phylogenetic analysis shows that the Yunnan population is grouped into the South American clade, which also includes other recently introduced Asian populations. Together with ecological data and colonization history of this pest, our results suggest that Yunnan population might have an ultimate, albeit not immediate, origin from South American populations. [source] PHYLOGEOGRAPHIC STRUCTURE AND CRYPTIC SPECIATION IN THE TRANS-ANTARCTIC MOSS PYRRHOBRYUM MNIOIDESEVOLUTION, Issue 2 2003Stuart F. McDaniel Abstract Many bryophyte species have distributions that span multiple continents. The hypotheses historically advanced to explain such distributions rely on either long-distance spore dispersal or slow rates of morphological evolution following ancient continental vicariance events. We use phylogenetic analyses of DNA sequence variation at three chloroplast loci (atpB-rbcL spacer, rps4 gene, and trnL intron and 3,spacer) to examine these two hypotheses in the trans-Antarctic moss Pyrrhobryum mnioides. We find: (1) reciprocal monophyly of Australasian and South American populations, indicating a lack of intercontinental dispersal; (2) shared haplotypes between Australia and New Zealand, suggesting recent or ongoing migration across the Tasman Sea; and (3) reciprocal monophyly among Patagonian and neotropical populations, suggesting no recent migration along the Andes. These results corroborate experimental work suggesting that spore features may be critical determinants of species range. We use the mid-Miocene development of the Atacama Desert, 14 million years ago, to calibrate a molecular clock for the tree. The age of the trans-Antarctic disjunction is estimated to be 80 million years ago, consistent with Gondwanan vicariance, making it among the most ancient documented cases of cryptic speciation. These data are in accord with niche conservatism, but whether the morphological stasis is a product of stabilizing selection or phylogenetic constraint is unknown. [source] Ontogeny of robusticity of craniofacial traits in modern humans: A study of South American populationsAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2010Paula N. Gonzalez Abstract To date, differences in craniofacial robusticity among modern and fossil humans have been primarily addressed by analyzing adult individuals; thus, the developmental basis of such differentiation remains poorly understood. This article aims to analyze the ontogenetic development of craniofacial robusticity in human populations from South America. Geometric morphometric methods were used to describe cranial traits in lateral view by using landmarks and semilandmarks. We compare the patterns of variation among populations obtained with subadults and adults to determine whether population-specific differences are evident at early postnatal ontogeny, compare ontogenetic allometric trajectories to ascertain whether changes in the ontogeny of shape contribute to the differentiation of adult morphologies, and estimate the amount of size change that occurs during growth along each population-specific trajectory. The results obtained indicate that the pattern of interpopulation variation in shape and size is already established at the age of 5 years, meaning that processes acting early during ontogeny contribute to the adult variation. The ontogenetic allometric trajectories are not parallel among all samples, suggesting the divergence in the size-related shape changes. Finally, the extension of ontogenetic trajectories also seems to contribute to shape variation observed among adults. Am J Phys Anthropol 2010. © 2009 Wiley-Liss, Inc. [source] Blood group O alleles in Native Americans: Implications in the peopling of the AmericasAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010Benito Estrada-Mena Abstract All major ABO blood alleles are found in most populations worldwide, whereas the majority of Native Americans are nearly exclusively in the O group. O allele molecular characterization could aid in elucidating the possible causes of group O predominance in Native American populations. In this work, we studied exon 6 and 7 sequence diversity in 180 O blood group individuals from four different Mesoamerican populations. Additionally, a comparative analysis of genetic diversity and population structure including South American populations was performed. Results revealed no significant differences among Mesoamerican and South American groups, but showed significant differences within population groups attributable to previously detected differences in genetic drift and founder effects throughout the American continent. Interestingly, in all American populations, the same set of haplotypes O1, O1v, and O1v(G542A) was present, suggesting the following: (1) that they constitute the main genetic pool of the founding population of the Americas and (2) that they derive from the same ancestral source, partially supporting the single founding population hypothesis. In addition, the consistent and restricted presence of the G542A mutation in Native Americans compared to worldwide populations allows it to be employed as an Ancestry informative marker (AIM). Present knowledge of the peopling of the Americas allows the prediction of the way in which the G542A mutation could have emerged in Beringia, probably during the differentiation process of Asian lineages that gave rise to the founding population of the continent. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. [source] Population-specific deviations of global human craniometric variation from a neutral modelAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010John H. Relethford Abstract Past studies have revealed that much of human craniometric variation follows a neutral model of population relationships. At the same time, there is evidence for the influence of natural selection in having shaped some global diversity in craniometrics. In order to partition these effects, and to explore other potential population-specific influences, this article analyzes residuals of craniometric distances from a geographically based neutral model of population structure. W.W. Howells' global craniometric data set was used for these analyses, consisting of 57 measurements for 22 populations around the world, excluding Polynesia and Micronesia because of the relatively recent settlement of these regions. Phenotypic and geographic distances were derived between all pairs of populations. Three-dimensional multidimensional scaling configurations were obtained for both distance matrices, and compared using a Procrustes rotation method to show which populations do not fit the geographic model. This analysis revealed three major deviations: the Buriat, Greenland Inuit, and Peru. The deviations of the Buriat and Greenland Inuit appear to be related to long-term adaptation to cold environments. The Peruvian sample is more similar to other New World populations than expected based on geographic distance alone. This deviation likely reflects the evolutionarily recent movement of human populations into South America, such that these populations are further from genetic equilibrium. This same pattern is seen in South American populations in a comparative analysis of classical genetic markers, but not in a comparative analysis of STR loci, perhaps reflecting the higher mutation rate for the latter. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. [source] Paleogenetical study of pre-Columbian samples from Pampa Grande (Salta, Argentina)AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2010Fransisco R. Carnese Abstract 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. [source] Hierarchical modeling of genome-wide Short Tandem Repeat (STR) markers infers native American prehistoryAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2010Cecil M. Lewis Jr. Abstract This study examines a genome-wide dataset of 678 Short Tandem Repeat loci characterized in 444 individuals representing 29 Native American populations as well as the Tundra Netsi and Yakut populations from Siberia. Using these data, the study tests four current hypotheses regarding the hierarchical distribution of neutral genetic variation in native South American populations: (1) the western region of South America harbors more variation than the eastern region of South America, (2) Central American and western South American populations cluster exclusively, (3) populations speaking the Chibchan-Paezan and Equatorial-Tucanoan language stock emerge as a group within an otherwise South American clade, (4) Chibchan-Paezan populations in Central America emerge together at the tips of the Chibchan-Paezan cluster. This study finds that hierarchical models with the best fit place Central American populations, and populations speaking the Chibchan-Paezan language stock, at a basal position or separated from the South American group, which is more consistent with a serial founder effect into South America than that previously described. Western (Andean) South America is found to harbor similar levels of variation as eastern (Equatorial-Tucanoan and Ge-Pano-Carib) South America, which is inconsistent with an initial west coast migration into South America. Moreover, in all relevant models, the estimates of genetic diversity within geographic regions suggest a major bottleneck or founder effect occurring within the North American subcontinent, before the peopling of Central and South America. Am J Phys Anthropol 2010. © 2009 Wiley-Liss, Inc. [source] MtDNA from extinct Tainos and the peopling of the CaribbeanANNALS OF HUMAN GENETICS, Issue 2 2001C. LALUEZA-FOX Tainos and Caribs were the inhabitants of the Caribbean when Columbus reached the Americas; both human groups became extinct soon after contact, decimated by the Spaniards and the diseases they brought. Samples belonging to pre-Columbian Taino Indians from the La Caleta site (Dominican Republic) have been analyzed, in order to ascertain the genetic affinities of these groups in relation to present-day Amerinds, and to reconstruct the genetic and demographic events that took place during the peopling of the Caribbean. Twenty-seven bone samples were extracted and analyzed for mtDNA variation. The four major Amerindian mtDNA lineages were screened through amplification of the specific marker regions and restriction enzymatic digestion, when needed. The HVRI of the control region was amplified with four sets of overlapping primers and sequenced in 19 of the samples. Both restriction enzyme and sequencing results suggest that only two (C and D) of the major mtDNA lineages were present in the sample: 18 individuals (75%) belonged to the C haplogroup, and 6 (25%) to the D haplogroup. Sequences display specific substitutions that are known to correlate with each haplogroup, a fact that helped to reject the possibility of European DNA contamination. A low rate of Taq misincorporations due to template damage was estimated from the cloning and sequencing of different PCR products of one of the samples. High frequencies of C and D haplogroups are more common in South American populations, a fact that points to that sub-continent as the homeland of the Taino ancestors, as previously suggested by linguistic and archaeological evidence. Sequence and haplogroup data show that the Tainos had a substantially reduced mtDNA diversity, which is indicative of an important founder effect during the colonization of the Caribbean Islands, assumed to have been a linear migratory movement from mainland South America following the chain configuration of the Antilles. [source] Lack of Genetic Structuring among Tropical Brazilian Wood Stork Populations and Low Genetic Differentiation from North American PopulationsBIOTROPICA, Issue 2 2004Cristiano Dosualdo Rocha ABSTRACT The Wood Stork (Mycteria americana) is a wading bird inhabiting subtropical and tropical regions of the American continent. This species is considered endangered in the United States. We compared variability and genetic structuring of nine Brazilian Pantanal subpopulations with an North American population using eight allozyme loci data (MPI, ICD, NSP, EST-D, LDH, PGM, 6PGD, and PEP-A) and four microsatellite loci data (WS1, WS2, WS4, and WS6). Average expected heterozygosity of Pantanal population was similar (0.198 ± 0.065) to that expected for the North American population (0.231 ± 0.066). No significant genetic differentiation was found among Pantanal subpopulations (Fst= 0.012) and low differentiation was detected between Pantanal and North American populations (Fst= 0.023). Lack of differentiation among Pantanal subpopulations may have been due to high gene flow level among birds of neighbor breeding colonies and low natal philopatry. We propose that low differentiation between North and South American populations has arisen either because these populations occupied neighboring regions during late glaciation or because there is a continuous gene flow between them, via Central American or northern South American populations. RESUMO O Cabeça-seca (Mycteria americana) é uma ave aquática habitante das regiões tropicais e subtropicais do continente americano. Essa espécie está ameaçada de extinção nos Estados Unidos. Nós comparamos a variabilidade e a estruturação genética de nove subpopulações brasileiras do Pantanal com as da população norte americana, baseando-se em dados de oito locos alozímicos (MPI, ICD, NSP, EST-D, LDH, PGM, 6PGD, e PEP-A) e em dados de quatro locos de microssatélites (WS1, WS2, WS4, e WS6). A heterozigosidade média esperada para a população do Pantanal (0.198 ± 0.065) foi semelhante á esperada para a população norte americana (0.231 ± 0.066). Não foi encontrada diferenciação genética significativa entre as subpopulaçóes do Pantanal (Fst= 0.012) e baixa diferenciação genética foi detectada entre as populações do Pantanal e a norte americana (.Fst= 0.023). A não diferenciação entre subpopulações do Pantanal pode ser resultante de um alto nível do fluxo génico entre aves de colónias reprodutivas vizinhas e da baixa filopatria natal. Nós propomos que a baixa diferenciação entre as populações norte e sul americanas seja decorrente da ocupaçaTo de regiões vizinhas por essas populações durante a última glaciação ou devido á existéncia de fluxo contínue entre elas, via populações da América Central ou do norte da América do Sul. [source] | ||||||||||