Hierarchical modeling of genome‐wide Short Tandem Repeat (STR) markers infers native American prehistory

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.     

Patterns of Admixture and Population Structure in Native Populations of Northwest North America

The initial contact of European populations with indigenous populations of the Americas produced diverse admixture processes across North, Central, and South America. Recent studies have examined the genetic structure of indigenous populations of Latin America and the Caribbean and their admixed descendants, reporting on the genomic impact of the history of admixture with colonizing populations of European and African ancestry. However, relatively little genomic research has been conducted on admixture in indigenous North American populations. In this study, we analyze genomic data at 475,109 single-nucleotide polymorphisms sampled in indigenous peoples of the Pacific Northwest in British Columbia and Southeast Alaska, populations with a well-documented history of contact with European and Asian traders, fishermen, and contract laborers. We find that the indigenous populations of the Pacific Northwest have higher gene diversity than Latin American indigenous populations. Among the Pacific Northwest populations, interior groups provide more evidence for East Asian admixture, whereas coastal groups have higher levels of European admixture. In contrast with many Latin American indigenous populations, the variance of admixture is high in each of the Pacific Northwest indigenous populations, as expected for recent and ongoing admixture processes. The results reveal some similarities but notable differences between admixture patterns in the Pacific Northwest and those in Latin America, contributing to a more detailed understanding of the genomic consequences of European colonization events throughout the Americas.     

Phaseolin-protein Variability in Wild Forms and Landraces of the Common Bean(Phaseolus vulgaris): Evidence for Multiple Centers of Domestication

A sample of 106 wild forms and 99 landraces of common bean (Thaseolus vulgaris) from Middle America and the Andean region of South America were screened for variability in phaseolin seed protein using one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS/PAGE) and two-dimensional isoelectric focusing SDS/PAGE. The Middle American wild forms exhibited phaseolin patterns similar to the ‘S’ pattern described previously in cultivated forms, as well as a wide variety of additional banding patterns—‘M’ (Middle America) types—not encountered among common bean cultivars. The Andean wild forms showed only the ‘T’ phaseolin pattern, also described previously among cultivated forms. Landraces from Middle America showed ‘S’ or ‘S’-like patterns with the exception of 2 lines with ‘T’ phaseolin. In Andean South America, a majority of landraces had the ‘T’ phaseolin. Additional types represented in that region were (in decreasing order of frequency) the ‘S’ and ‘C’ types (already described among cultivated forms) as well as the ‘H’ (Huevo de huanchaco) and ‘A’ (Ayacucho), (new patterns previously undescribed among wild and cultivated beans). In each region—Middle America and Andean South America—the seeds of landraces with ‘T’ phaseolin were significantly larger than those of landraces with ‘S’ phaseolin. No significant differences in seed size were observed among landraces with ‘T,’ ‘C,’ ‘H,’ and ‘A’ phaseolin types of the Andean region. Our data favor 2 primary areas of domestication, one in Middle America leading to small-seeded cultivars with ‘S’ phaseolin patterns and the other in the Andes giving rise to large-seeded cultivars with ‘T’ (and possibly ‘C,’ ‘H,’ and ‘A’) phaseolin patterns.     

Geographic patterns of genetic diversity in Poulsenia armata (Moraceae): implications for the theory of Pleistocene refugia and the importance of riparian forest

Abstract. Tropical forests are species-diverse communities, but we know very little about the geographical distribution of genetic diversity within a species. During the late Pleistocene, lower temperatures and rainfall reduced the distribution of tropical wet forests, and in Central America lowland species may have been limited to riparian habitats. Approximately 12,000 years bp , temperature and rainfall increased in Central America, the distribution of wet forest species expanded, and today the distribution of some species extends into southern Mexico. The distribution of genetic diversity, based on RAPD markers, among ten populations of Poulsenia armata (Miq.) Standl. (Moraceae) suggests that these populations did not originate from a single refugium or region in the late Pleistocene. The Central American populations had high genetic diversity and unique bands giving support to the hypothesis that populations of P. armata occurred in Central American during the late Pleistocene. The majority of genetic diversity was partitioned among populations and there was no geographical relationship among populations, suggesting that these populations were isolated for a long period and there has been little gene flow. Populations of P. armata may have persisted in riparian zones along the Caribbean coast during the late Pleistocene. Given that riparian forest can support high levels of biodiversity in ecological time, and they have played an important role during periods of climate change over geological time, their conservation is of utmost importance particularly with the threat of a rapid shift in climatic patterns.     

Asymmetric Response of Costa Rican White-Breasted Wood-Wrens (Henicorhina leucosticta) to Vocalizations from Allopatric Populations

Divergence in song between allopatric populations can contribute to premating reproductive isolation in territorial birds. Song divergence is typically measured by quantifying divergence in vocal traits using audio recordings, but field playback experiments provide a more direct way to behaviorally measure song divergence between allopatric populations. The White-breasted Wood-Wren (Henicorhina leucosticta; hereafter “WBWW”) is an abundant Neotropical species with four mitochondrial clades (in Central America, the Darién, the Chocó and the Amazon) that are deeply divergent (~5–16% sequence divergence). We assessed the possibility that the WBWW as currently defined may represent multiple biological species by conducting both statistical analysis of vocal characters and field playback experiments within three clades (Central America, Chocó and Amazon). Our analysis of vocal traits revealed that Central American songs overlapped in acoustic space with Chocó songs, indicating vocal similarity between these two populations, but that Central American songs were largely divergent from Amazonian songs. Playback experiments in the Caribbean lowlands of Costa Rica revealed that Central American WBWWs typically responded aggressively to songs from the Chocó population but did not respond to playback of songs from the Amazonian population, echoing the results of the vocal trait analysis. This marked difference in behavioral response demonstrates that the songs of Central American and Amazonian WBWWs (but not Central American and Chocó WBWWs) have diverged sufficiently that Central American WBWWs no longer recognize song from Amazonian WBWWs as a signal to elicit territorial defense. This suggests that significant premating reproductive isolation has evolved between these two populations, at least from the perspective of the Central American population, and is consistent with the possibility that Central American and Amazonian populations represent distinct biological species. We conclude by advocating for the further use of field playback experiments to assess premating reproductive isolation (and species limits) between allopatric songbird populations, a situation where behavioral systematics can answer questions that phylogenetic systematics cannot.     

Morphometric and genetic analyses differentiate Mesoamerican populations of the endangered stingless bee Melipona beecheii (Hymenoptera: Meliponidae) and support their conservation as two separate units

Phenotypic and molecular differences were previously found in populations of the endangered stingless bee Melipona beecheii from two extremes of its geographic range. In this study we combine the use of morphometric and molecular tools, with the aim of investigating patterns of phenotypic and molecular variation in populations across Mesoamerica. Morphometric analyses showed that bees from Mexico have significantly smaller body size compared with populations from Central America, forming two separated groups. Bayesian analysis of the ITS1 spacer of the ribosomal gene also showed the existence of two clusters: one composed by the Mexican populations, and another in which the Central American ones assembled (Guatemala, El Salvador, Nicaragua and Costa Rica). The combined results confirm the presence of two taxonomic units: one distributed in southern Mexico (ranging from the Yucatan peninsula to the north of Guatemala), and a Central American unit found from the southern part of Guatemala down to Costa Rica. These units should be considered separately under conservation programs and therefore, human assisted colony exchange between them should be avoided.     

Possible migration routes into South America deduced from mitochondrial DNA studies in Colombian Amerindian populations

Mitochondrial DNA haplotype studies have been useful in unraveling the origins of Native Americans. Such studies are based on restriction site and intergenic deletion/insertion polymorphisms, which define four main haplotype groups common to Asian and American populations. Several studies have characterized these lineages in North, Central, and South American Amerindian, as well as Na Dene and Aleutian populations. Siberian, Central Asian, and Southeast Asian populations have also been analyzed, in the hope of fully depicting the route(s) of migration between Asia and America. Colombia, a key route of migration between North and South America, has until now not been studied. To resolve the current lack of information about Colombian Amerindian populations, we have investigated the presence of the founder haplogroups in 25 different ethnic groups from all over the country. The present research is part of an interdisciplinary program, Expedición Humana, fostered by the Universidad Javeriana and Dr. J. E. Bernal V. The results show the presence of the four founder A-D Amerindian lineages, with varied distributions in the different populations, as well as the presence of other haplotypes in frequencies ranging from 3% to 26%. These include some unique or private polymorphisms, and also indicate the probable presence of other Asian and a few non-Amerindian lineages. A spatial structure is apparent for haplogroups A and D, and to a lesser extent for haplogroup C. While haplogroup A and D frequencies in Colombian populations from the northwestern side of the Andes resemble those seen in Central American Amerindians more than those seen in South American populations, their frequencies on the southeastern side more closely resemble the bulk of South American frequencies so far reported, raising the question as to whether they reflect more than one migration route into South America. High frequencies of the B lineage are also characteristic of some populations. Our observations may be explained by historical events during the pre-Columbian dispersion of the first settlers and, later, by disruptions caused by the European colonization.     

Dispersal Pathways and Genetic Differentiation among Worldwide Populations of the Invasive Weed Centaurea solstitialis L. (Asteraceae)

The natural history of introduced species is often unclear due to a lack of historical records. Even when historical information is readily available, important factors of the invasions such as genetic bottlenecks, hybridization, historical relationships among populations and adaptive changes are left unknown. In this study, we developed a set of nuclear, simple sequence repeat markers and used these to characterize the genetic diversity and population structure among native (Eurasian) and non-native (North and South American) populations of Centaurea solstitialis L., (yellow starthistle). We used these data to test hypotheses about the invasion pathways of the species that were based on historical and geographical records, and we make inferences about historical relationships among populations and demographic processes following invasion. We confirm that the center of diversity and the native range of the species is likely the eastern Mediterranean region in the vicinity of Turkey. From this region, the species likely proceeded to colonize other parts of Europe and Asia via a slow, stepwise range expansion. Spanish populations were the primary source of seed to invade South America via human-mediated events, as was evident from historical records, but populations from the eastern Mediterranean region were also important. North American populations were largely derived from South America, but had secondary contributors. We suggest that the introduction history of non-native populations from disparate parts of the native range have allowed not just one, but multiple opportunities first in South America then again in North America for the creation of novel genotypes via intraspecific hybridization. We propose that multiple intraspecific hybridization events may have created especially potent conditions for the selection of a noxious invader, and may explain differences in genetic patterns among North and South America populations, inferred differences in demographic processes, as well as morphological differences previously reported from common garden experiments.     

Distribution of Sexual and Agamospermous Populations of Eupatorium (Compositae) in Asia

Abstract Examinations of chromosome number voucher specimens show that sexual diploid and agamospermous polyploid plants of Eupatorium in Asia can be distinguished by morphology, fertility, and stainability of pollen grains. Using these criteria, reproductive systems (sexual vs. agamospermous) were estimated for 558 herbarium specimens of Eupatorium in East Asia. Of 22 taxa examined, six included both sexual and agamospermous specimens; those of one taxon were all agamospermous; and those of 15 taxa were all sexual. This result shows that 21 taxa are not agamospermous microspecies but are differentiated at the diploid level. Sexual populations of most taxa had restricted geographical distributions. Eupatorium chinense var. chinense and var. oppositifolium consisted of both sexual and agamospermous populations. Sexual populations of these two varieties were allopatric and distinct in external morphology, suggesting differentiation at the species level. The specimens of E. heterophyllum s. str. were all agamospermous, while those of E. mairel , often treated as synonymous with E. heterophyllum , were sexual.
In comparing East Asian and North American Eupatorium for the distributional patterns of sexual and agamospermous populations, three differences can be pointed out: (1) Agamospermous plants of autopolyploid origin have evolved in eight species and are widespread in North America; while most agamospermous plants in East Asia may be of allopolyploid origin, have relatively restricted ranges, and are less frequent than the diploid plants with the exception of in E. chinense var. oppositifolium , (2) The number of sexual species with wide range is greater in North America than in East Asia. (3) The number of sexual species with restricted ranges is greater in East Asia than in North America. The results obtained suggest that speciation among the plants of Eupatorium has occurred more recently in East Asia than in North America.     

A rapid diversification of rainforest trees (Guatteria; Annonaceae) following dispersal from Central into South America

Several recent studies have suggested that a substantial portion of today's plant diversity in the Neotropics has resulted from the dispersal of taxa into that region rather than vicariance, but more data are needed to substantiate this claim. Guatteria (Annonaceae) is, with 265 species, the third largest genus of Neotropical trees after Inga (Fabaceae) and Ocotea (Lauraceae), and its widespread distribution and frequent occurrence makes the genus an excellent model taxon to study diversification patterns. This study reconstructed the phylogeny of Guatteria and inferred three major biogeographical events in the history of the genus: (1) a trans-oceanic Miocene migration from Central into South America before the closing of the Isthmus of Panama; (2) a major diversification of the lineage within South America; and (3) several migrations of South American lineages back into Central America via the closed Panamanian land bridge. Therefore, Guatteria is not an Amazonian centred-genus sensu Gentry but a major Miocene diversification that followed its dispersal into South America. This study provides further evidence that migration into the Neotropics was an important factor in the historical assembly of its biodiversity. Furthermore, it is shown that phylogenetic patterns are comparable to those found in Ocotea and Inga and that a closer comparison of these genera is desirable.     

Dissemination pathways of common bean (Phaseolus vulgaris,Fabaceae) deduced from phaseolin electrophoretic variability. I. The Americas

Dissemination pathways of common bean (Phaseolus vulgaris) cultivars from their areas of domestication to other parts of the Americas were determined using phaseolin type, as determined by 1-dimensional SDS/PAGE. Common bean cultivars of lowland South America exhibited approximately equal numbers of ‘S’ and ‘T’ phaseolin types. ‘S2019 cultivars of that region may have been introduced along a route starting in Middle America and leading into Colombia, Venezuela, and eventually Brazil. ‘T’ phaseolin cultivars in lowland South America may have been introduced directly from the Andes or indirectly by European immigrants. In the southwestern U.S.A., most of the cultivars showed an ‘S’ phaseolin, confirming the Middle American origin of these cultivars, as suggested previously by the archaeological record. In northeastern U.S.A. and Canada, the ‘T’and ‘C’ phaseolin types were more frequent than the ‘S’ phaseolin cultivars. While most of the former were possibly introduced into that region by European immigrants, most of the latter may have been introduced by the pre-Columbian Indian populations. Seed size analysis revealed that ‘T’ or ‘C’ phaseolin cultivars had significantly larger seeds than ‘S’ phaseolin cultivars, as had been observed previously in Middle America and the Andes. The phaseolin types of commercial seed types and of early northeastern U.S. cultivars are discussed.     

INTRASPECIFIC MOLECULAR PHYLOGENY IN THE YELLOW WARBLER (DENDROICA PETECHIA), AND IMPLICATIONS FOR AVIAN BIOGEOGRAPHY IN THE WEST INDIES

A phylogenetic analysis of mitochondrial DNA (mtDNA) restriction sites was used to examine the evolutionary history of populations of yellow warbler (Dendroica petechia) sampled from North America, Central America, South America, and the West Indies. Thirty-seven haplotypes were identified, and only one was found in more than one of these regions. Estimated sequence divergence among haplotypes ranged from 0.14 to 3.17%, and mtDNAs from North American migratory populations clearly were differentiated from those of most tropical sedentary populations. Parsimony analysis of haplotypes suggested multiple colonizations of the West Indies archipelago and of individual Caribbean islands. The inference of multiple colonizations has important implications for studies of avian ecology and evolution in this region.     

The geography of diversification in the mormoopids (Chiroptera: Mormoopidae)

The traditional explanation of the distribution of the Mormoopidae is that this family originated in southern Central America or northern South America, later expanding its range north to Mexico and the West Indies, and differentiating into eight species. An alternative fossil-based hypothesis argues that the family originated in the northern Neotropics, reached the Caribbean early in its history, and dispersed to South America after the completion of the Isthmus of Panama. The present study analyses new and previously published sequence data from the mitochondrial 12S, tRNA^val, 16S, and cytochrome b , and the nuclear Rag 2, to evaluate species boundaries and infer relationships among extant taxa. Fixed differences in cytochrome b often coincide with published morphological characters and show that the family contains at least 13 species. Two additional, morphologically indistinct, lineages are restricted to Suriname and French Guiana. Phylogeny-based inferences of ancestral area are equivocal on the geographical origin of mormoopids, in part because several internal nodes are not resolved with the available data. Divergences between Middle American and Antillean populations are greater than those between Mexico/Central America and South America. This suggests that mormoopids diversified in northern Neotropics before entering South America. A northern neotropical origin for mormoopids is congruent with both the Tertiary fossil record and recent phylogenetic hypotheses for the sister family to the Mormoopidae, the Phyllostomidae.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 101–118.     

Phylogeny and biogeography of Yellow-headed and Blue-fronted Parrots (Amazona ochrocephala and Amazona aestiva) with special reference to the South American taxa

The Yellow-headed Parrot ( Amazona ochrocephala ) has a broad Neotropical distribution, ranging from Mexico to the Amazon Basin, and a history of complex taxonomy and controversial species limits. Recent molecular analyses have started to clarify the taxonomic arrangement of the complex, but have not included a representative geographical sampling from South America. These studies have shown that the Yellow-headed complex can be divided into three main lineages, and seems to be paraphyletic, due to the inclusion of the Blue-fronted Parrot ( Amazona aestiva ) that occurs in central South America. Here we present a phylogenetic analysis based on mitochondrial DNA sequences of 45 representatives of the Yellow-headed complex from South and Central America, plus 13 Blue-fronted individuals from different localities in South America. Our analyses recover the three primary lineages found previously in the Yellow-headed complex, show that there is genetic structure in the South American lineage, which can be divided into two well-supported, closely related clades, and demonstrate that Blue-fronted samples are distributed in both clades. Differentiation of South American Blue-fronted and Yellow-headed Parrot populations does not correspond to the plumage differences used to distinguish the Blue-fronted Parrot from the Yellow-headed Parrot, nor to plumage differences used to distinguish among South American Yellow-headed subspecies. This suggests that traditional taxonomy based on plumage characters needs revision, and that this may be an interesting example of ongoing divergence-with-gene-flow related to the forest/open area ecotone in southern Amazonia.     

Chloroplast DNA Microsatellites Reveal Contrasting Phylogeographic Structure in Mahogany (Swietenia macrophylla King, Meliaceae) from Amazonia and Central America

Big-leaf mahogany (Swietenia macrophylla King) is one of the most valuable and overharvested timber trees of tropical America. In order to better characterize geographic patterns of genetic variation, we performed a phylogeographic analysis of S. macrophylla based on six polymorphic chloroplast genome simple sequence repeat loci (cpSSRs) analyzed in 16 populations (N?=?245 individuals) distributed across Central America and the Brazilian Amazon. Of the 31 total cpDNA haplotypes identified, 16 occurred in Central America and 15 in Amazonia with no single haplotype shared between the two regions. Populations from Central America showed moderate differentiation (F _ST ?=?0.36) while within population genetic diversity was generally high (mean Nei’s H _E ?=?0.639). In contrast, the Amazonian populations were strongly differentiated (F _ST ?=?0.91) and contained relatively low genetic diversity (mean H _E ?=?0.176), except for one highly diverse population (H _E ?=?0.925) from eastern Amazonia. Spatial analysis of molecular variance (SAMOVA) identified a single Central American phylogroup and four Amazonian phylogroups, indicating stronger phylogeographic structure within Amazonia. The results demonstrate distinctive regional patterns of S. macrophylla differentiation, and the first evidence of a strong phylogeographic break between Central American and South American mahogany populations. We suggest that the frequent occurrence of hurricanes in Central America, the differences in the glacial histories and in the duration and intensity of anthropogenic disturbance during the late Holocene may have played important roles in the geographic structuring of cpDNA lineages in the two regions. The high private haplotype diversity in Brazilian populations suggests that cpSSRs can be used as DNA barcodes for regional timber certification.     

Molecular population genetics of the malaria vector Anopheles darlingi in Central and South America

To analyze the genetic relatedness and phylogeographic structure of Anopheles darlingi from 19 localities throughout Central and South America, we used a minimum spanning network, diversity measures, differentiation, neutrality tests, and mismatch distribution with mitochondrial cytochrome oxidase subunit I (COI) sequences. All the Central American haplotypes were separated by seven mutational steps from the South American haplotypes and the FST distance-based neighbor-joining tree showed a primary division between Central and South America, evidence for a putative gene pool division. More ancestral and diverse haplotypes were found in Amazonian and southern Brazil populations, suggesting that Central American populations may have originated in South America. The patterns of the mtDNA haplotype diversity and five of six tests for equilibrium implicate demographic expansion in the South American populations as the historical structure, but mismatch distribution depicts populations at mutation drift equilibrium (MDE). In South America, the departure from equilibrium was consistent with an expansion that occurred during the Pleistocene.     

Historical isolation,range expansion,and secondary contact of two highly divergent mitochondrial lineages in spotted salamanders (Ambystoma maculatum)

Abstract.— The high species diversity of aquatic and terrestrial faunas in eastern North America has been attributed to range reductions and allopatric diversification resulting from historical climate change. The role these processes may have played in speciation is still a matter of considerable debate; however, their impacts on intraspecific genetic structure have been well documented. We use mitochondrial DNA sequences to reconstruct an intraspecific phylogeny of the widespread North American spotted salamander, Ambystoma maculatum , and test whether phylogenetic patterns conform to regional biogeographical hypotheses about the origins of diversity in eastern North America. Specifically, we address the number and locations of historical refugia, the extent and patterns of postglacial colonization by divergent lineages, and the origin and affinities of populations in the Interior Highland region. Despite apparent morphological uniformity, genetic discontinuities throughout the range of this species suggest that populations were historically fragmented in at least two refugia in the southern Appalachian Mountains. The ranges of these two highly divergent clades expanded northward, resulting in two widely distributed lineages that are sympatric in regions previously proposed as suture zones for other taxa. The evolutionary history of spotted salamander populations underscores the generality of biogeographical processes in eastern North America: despite differences in population size, glacial refugia, and vagility, similar signatures of differentiation are evident among and within widespread taxa.     

Dermatoglyphic assessment of the genetic relationships of native American populations

Genetic distance techniques and cluster analysis were used to determine which dermatoglyphic parameters were most useful in assessing genetic relationships between native American populations. The dermatoglyphic parameters used for this analysis were those most completely reported in the papers examined in a literature survey we had carried out previously, and include digital patterns, modal types of the C-line and D-line terminations, and palmar patterns in the hypothenar, thenar/I, and interdigital areas. The populations examined were separated by sex and divided into seven major geographical groups: Eskimo; North American Indian; Maya and non-Maya (Central America); Amazonian; Quechua, and Aymara (South America). Mean frequencies of dermatoglyphic traits were computed for each group and pairwise “genetic” distances calculated using Cavalli-Sforza and Edward's D-test. Dendrograms were then generated from these D-values using Q-mode cluster analysis. Using the hypothenar, thenar/I and III and IV interdigital areas, the results of this analysis demonstrated a good fit to an expected phylogenetic tree. When digital patterns, patterns in the II interdigital area, and the modal types of the C-line were included in the analysis, the same phylogenetic relationships were observed. However, inclusion of the modal types of the D-line with the other parameters tended to introduce some distortion and a greater separation between sexes within the same populations.     

Gm haplotype distribution in Amerindians: Relationship with geography and language

A review is made of the Gm haplotype distribution in 60 groups of Eskimos, North, Central and South American Indians, totaling 22,808 individuals. Differences were observed in the shapes of the distribution of Gm*ag and the other markers. Nearly identical values for F_ST and average heterozygosities were obtained in the North+Central/South comparisons. North-South and Southwest/Northeast clinal differences were observed in the Americas using correspondence factorial analysis. The two haplotypes mainly responsible for these differences are Gm*axg and Gm*abOst. When the populations are classified by language groups, besides the recognized differences between Eskimos and Athabaskan (Na-Dene) speakers compared with Amerinds, others are found. For instance, Uto-Aztecan speakers of the United States and Mexico differ in Gm frequencies from the Nuclear Chibchan, Macro-Arawak, and Carib speakers of Central and South America. The notion of a homogeneous Amerind genetic pool does not conform with these and other results. © 1993 Wiley-Liss, Inc.     

Comparative phylogeography of short-tailed bats (Carollia: Phyllostomidae)

This is the first study of comparative phylogeography involving closely related species of Neotropical bats of the family Phyllostomidae. We compared patterns of geographical variation within the five species of fruit-eating bats currently recognized in the genus Carollia using the complete mitochondrial cytochrome-b gene. Our results suggest that the combined effect of the uplift of the Andes and the Panamanian land bridge has been as important for bats as for terrestrial mammals in shaping present-day biodiversity in the New World tropics. Species in this genus can be arranged in two highly supported clades, with a deep subdivision within each that corresponds well to differences across the Andes. We found three congruent phylogeographical patterns across species in this genus. First, the closer relationship between samples from western Ecuador and those from Central America, compared with populations east of the Andes in C. brevicauda, C. castanea and C. perspicillata. Second, the likelihood of a similar timing in South America for the arrival and diversification of C. brevicauda and C. perspicillata from their Central America ancestors. Third, the expansion of C. perspicillata and C. sowelli into northwestern Central America in the relatively recent past. Using a molecular clock, with rates ranging from 2.3 to 5% per 10(6) years, diversification within Carollia would have occurred over the last 1-4.5 Myr. These estimates agree well with the last rise of the Northern Andes and the Panama isthmus.