Middle American Research Articles

Mapping of the Ur‐7 Gene for Specific Resistance to Rust in Common Bean

Bean rust, caused by Uromyces appendiculatus (Pers.: Pers.) Unger, is a major disease of common bean (Phaseolus vulgaris L.). A recommended strategy to obtain durable rust resistance is to use molecular markers linked to rust resistance genes for pyramiding monogenic resistance genes into a single bean cultivar. However, markers linked to the Ur‐7 gene for specific resistance (SR) to rust present in the cultivar Great Northern (GN) 1140 have not been reported. Our objectives were to identify random amplified polymorphic DNA (RAPD) markers linked to the Ur‐7 gene for SR to rust race 59 using bulked segregant analysis in an F2 population from the Middle American (MA) common bean cross ‘GN1140’ (resistant) × GN Nebr. #1 (susceptible) and to map the Ur‐7 gene on an existing RAPD marker‐based linkage map constructed by means of recombinant inbred lines (RILs) from the MA cross GN BelNeb‐RR‐1 × A 55. A single dominant gene controlling SR to race 59 was found in the F2 and confirmed in the F3 Six RAPD markers were detected in a coupling phase linkage with the Ur‐7 gene. Cosegregating coupling‐phase markers OAD12.550 and OAF17.900 were found. These were also present in pinto US‐5 from which the rust resistance of GN1140 was derived. Among the three repulsion‐phase markers, marker OAB18.650 was the most closely linked to the Ur‐7 gene at a distance of 7.6 centimorgans (cM). All linked markers detected in the F2 population also segregated in the RILs and were located on linkage group 11 of the existing linkage map. These markers linked to the Ur‐7 gene of MA origin identified here, along with other independent rust resistance genes from other germplasm, could be utilized to pyramid multiple genes into a bean cultivar for more durable rust resistance.

Contributions of the Bean/Cowpea CRSP to management of bean diseases

Diseases are a major constraint to production of beans in developing countries, reducing yields and seed quality. Contributing factors include poor disease management, lack of resistant cultivars, and the limited availability of certified disease-free seed. From the outset the Bean/Cowpea Collaborative Research Support Program (CRSP) has emphasized integrated disease management, and breeding for resistance to bean rust ( Uromyces appendiculatus), common bacterial blight ( Xanthomonas campestris (= X. axonopodis) pv. phaseoli) (CBB) and web blight ( Thanatephorus cucumeris (anamorph Rhizoctonia solani)) (WB). Later in the 1990s, angular leaf spot ( Phaeoisariopsis griseola) (ALS), and virus induced bean common mosaic (BCM) and bean common mosaic necrosis (BCMN) became more widespread and epidemic. The research included development of disease-resistant germplasm and studies of pathogenic variation and epidemiology. During the early 1990s bean golden yellow mosaic (BGYM), became a major disease of common bean in the Caribbean and Central America. No cultivar resistant to the gemini virus causing BGYM was available in the Dominican Republic (DR) and pesticides were used to reduce transmission of the virus by white flies ( Bremisia tabaci) biotype A. A change in the bean-production system to limit reproduction of the vector through a host-free period and concentrate the bean growing season to a four month period reduced BGYM significantly. Improved resistant cultivars and disease management resulted in high yields and self-sufficiency of beans in the DR. Evidence for co-evolution of the pathogens causing ALS, CBB, and rust in the two major bean gene pools (Andean and Middle American) was found. Variation in the WB pathogen on bean indicated independent genetic populations and the presence of different anastosmosis subgroups. WB disease management practices should be designed for the sub-group of the pathogen. Seed transmission was found to be a significant source of R. solani inoculum. Specific ( Ur-9 gene) and adult-plant resistance ( Ur-12 gene) to rust was identified for PC-50 (Andean origin) in the DR, and the genes were mapped. A mobile rust nursery was developed to monitor races of rust in a region and assist in resistance-gene deployment in bean germplasm and varieties. DNA based diagnostic methods were developed to differentiate X. campestris pv. phaseoli from X. campestris pv. phaseoli var fuscans (prevalent in East Africa) and P. griseola isolates. DNA hybridization methods also were developed to identify BGYM and bean golden mosaic viruses. Research in USA and East Africa has helped define bean common mosaic virus (BCMV) and bean common mosaic necrotic virus (BCMNV) as separate viruses and has demonstrated that BCMNV appears to be indigenous to Africa. Serological tools were developed that assist in the detection and identification of potyviruses, BCMV and BCMNV. These tools are now used worldwide.

Rare Snakes—Five New Species from Eastern Panama: Reviews of Northern Atractus and Southern Geophis (Colubridae: Dipsadinae)

Abstract The South American genus Atractus barely enters political North America on the eastern half of the Isthmus of Panama, where it is extraordinarily rare. Collected over a period of 39 years, the five Panamanian specimens of Atractus known to the author represent five species! Four new species are described: A. darienensis, A. hostilitractus, A. imperfectus, and A. depressiocellus. The fifth species is A. clarki Dunn and Bailey, for which a second specimen is reported from the Colombia Choco. The noncapitate hemipenis of A. clarki may be primitive in being calyculate and deeply bilobed. The morphologically convergent Geophis is primarily a Middle American genus—Mexico to western Panama, with two or three outlying species in the western Andes of Colombia (G. betaniensis, G. nigroalbus, and probably G. hoffmanni). The genus is unrecorded from eastern Panama, and a few old records for central Panama seem to have been based on erroneous specimen data. Nonetheless, the genus does occur in east-central Pa...

Human Rights in China and the United States: Competing Visions and Discrepant Performances

Important differences exist between the Chinese and US political systems and cultures. Yet they share one seemingly paradoxical similarity. Each sees itself as a special, if not unique, case that at the same time somehow offers a worthy model for emulation by others. Whether described as the Middle Kingdom syndrome, Manifest Destiny, or American exceptionalism, popular self-attribution assigns to each country a particularly favorable, indeed central, status in the community of nations. This self-image, however, is often accompanied by a strong isolationist streak with an open disdain for the rest of the world. Paradoxically, the views and conduct of both countries also evince a self-appointed messianic role, assuming as a matter of course that their values, institutions, and practices should naturally be a source of inspiration for and a target of admiration and imitation by others. Thus, notwithstanding self-attribution of distinctness, each sees itself as the embodiment of universal principles. There appears to be little discomfort in this apparent contradiction?and little awareness of the shared proclivity for self-assured ethnocentrism and missionary zeal for converts. Both countries also appear to be remarkably at ease in moving in and out of phases of love and hate?repeating seemingly alternating cycles of cordiality and confrontation. Periods of mutual admiration and enchant ment (remember the euphoria accompanying Richard Nixon's opening of

Why is the Central Trans-Mexican Volcanic Belt (102°–99°W) in transtensive deformation?

Using well-defined focal mechanisms, new poles of rotation, and accurate bathymetry, it will be shown that the N34°E oblique convergence between the Cocos and North America plates, along the N290°E Middle American Trench, in front of Central Mexico (102°–99°W), is associated with slip partitioning. In the same way, it will be shown that the forearc sliver will move rigidly eastward along a trench parallel left-lateral strike-slip fault. By reviewing the literature and analysing seismicity, the E–W Central Trans-Mexican Volcanic Belt (TMVB) is the only active zone in Central Mexico. It is the best candidate to accommodate slip partitioning at the trench where mainly extensive E–W-trending normal active faults with left-lateral component are reported. Fault striae inversions, derived from the literature and our focal mechanisms inversion, confirm that the state of stress in the Central TMVB is transtensive since Middle Quaternary with Shmin ( σ 3) trending NW–SE and Shmax ( σ 1 or σ 2) trending NE–SW. The oblique convergence and slip partitioning at the trench induce this state of stress. The N290°W trench-parallel component, which should be accommodated in the upper plate, is, however, not parallel to the E–W arc-parallel component, but differs by about 20° clockwise. This implies that the former must be partitioned along the E–W faults of the Central TMVB. If we assume that the trench-parallel slip rate of 8 mm year −1 (102°–99°W) is fully accommodated along the Central TMVB, we should expect maximum horizontal extensional and left-lateral slip rates along E–W normal faults of 2 mm year −1 and less than 7 mm year −1, respectively. Strain partitioning may also be accommodated partially by the accretionary wedge or/and by normal faulting that affects the deeper part of the upper plate around 18°N of latitude.

The Attacks of 9/11: Evidence of a Clash of Religions?

President George W. Bush and Prime Minister Tony Blair have repeatedly declared that the coalition war in Afghanistan is not a war against Islam. Islam, however, was a feature of the events of 11 September 2001 and of the events that followed. Should the conflict between the United States and Osama bin Laden and between the coalition forces and the Taliban be seen as an example of a conflict between two religious traditions in the way Professor Samuel Huntington prophesied in his seminal Clash of Civilizations essay? (1) This article aims to unravel some of the religious background to the attacks on the World Trade Center and the Pentagon on what began as a perfect day in September in New York and Washington. (2) It looks too at the religious background to events that have followed on from those attacks. Much of the latter part of the article will be devoted to examining any perceived from the Muslim point of view in an attempt to generate a better understanding of how at least some Muslims view the West in general and America in particular. It will look, again from the Muslim point of view, at how any perception of a clash might be either ameliorated or neutralized. Religious Motivation of the Terrorists should pray, you should fast. You should ask God for guidance, you should ask God for help....Continue to recite the [Koran]. Purify your heart and clean it from all earthly matters. So read the hand-written instructions to the hijackers who carried out their suicide missions by flying into the World Trade Center and into the Pentagon on 11 September 2001. Their task was perceived as a religious one. instructions continued: The time of fun and waste has gone. time of judgment has arrived.... You will be entering paradise. You will be entering the happiest life, everlasting (3) These instructions demonstrate how--for the writer and for the hijackers themselves--the suicide mission was seen as a religious one. first four pages of the hijackers' instructions recalled incidents in Islamic history, particularly incidents of Muhammad triumphing against adversaries. On the fifth and last page, guidance was given about what to do on entering the plane. hijacker was asked to pray, Allah, open all doors for me. Oh Allah who answers prayers and answers those who ask you, I am asking for your help. Allah, I trust in you. Allah, I myself in your hands.... There is no God but Allah, I being a sinner. We are of Allah and to Allah we return. (4) In 1990 Iraq Kuwait and so began the Gulf War. A coalition of Muslim Middle Eastern and American, British, and other nations joined together to drive out Saddam Hussein's army. For some Arab Muslims, bin Laden included, this period was classed as al amza, the crisis. It was a crisis for at least two reasons: first, it involved Muslim Arabs fighting other Muslim Arabs; second, it involved American and other non-Arab forces entering Saudi territory. To understand why this second reason was seen as problematic, one has to understand that for a Muslim the Saudi city of Mecca, the birthplace of the prophet Muhammad, is a holy city. Indeed, it is so holy that non-Muslims are not allowed to enter it. Some of that holiness is seen by some Muslims to spread through the whole country of Saudi Arabia. To have non-Muslim soldiers enter the country, and particularly to do so in order to help one Muslim country fight against another Muslim country, was seen as offensive. America and its allies, in the eyes of some fundamentalist Muslims, represent the very opposite of what Islam stands for. Islam is seen to stand for solidarity among Muslim peoples; it is seen to stand for moral decency, for obedience to Allah and the precepts of Allah found in Islam's holy book, the Koran, and in the sayings and deeds of Muhammad, the sunnah. fundamentalist Muslim saw his holy land of Saudi Arabia invaded by troops whose home country represented, as he saw it, the very opposite of the Muslim way of life. …

Patterns of resistance to angular leaf spot, anthracnose and common bacterial blight in common bean germplasm

Diseases and insect pests are major causes of low yields of common bean (Phaseolus vulgaris L.) in Latin America and Africa. Anthracnose, angular leaf spot and common bacterial blight are widespread foliar diseases of common bean that also infect pods and seeds. One thousand and eighty-two accessions from a common bean core collection from the primary centres of origin were investigated for reaction to these three diseases. Angular leaf spot and common bacterial blight were evaluated in the field at Santander de Quilichao, Colombia, and anthracnose was evaluated in a screenhouse in Popay�n, Colombia. By using the 15-group level from a hierarchical clustering procedure, it was found that 7 groups were formed with mainly Andean common bean accessions (Andean gene pool), 7 groups with mainly Middle American accessions (Middle American gene pool), while 1�group contained mixed accessions. Consistent with the theory of co-evolution, it was generally observed that accessions from the Andean gene pool were resistant to Middle American pathogen isolates causing anthracnoxe, while the Middle American accessions were resistant to pathogen isolates from the Andes. Different combinations of resistance patterns were found, and breeders can use this information to select a specific group of accessions on the basis of their need.

Selection for seed yield in Andean intra-gene pool and Andean × Middle American inter-gene pool populations of common bean

Yields of large-seeded Andean (A) common bean (Phaseolus vulgaris L.) cultivars of Chile and Nueva Granada races are 40 to 60% lower compared to their Middle American (M) counterparts of small-seeded Mesoamerica and medium-seeded Durango races. Our objective was to use the concept of congruity backcrossing between Andean x Middle American inter-gene pool [AM 11833 = A 483 (A)///// A 686 (M) //// PVA 800A(A)/// ‘Carioca’ (M)// Carioca (M)/ G 19833 (A)] and between races within Andean gene pool [i.e., intra-gene pool Andean, AA 11834 = A483 (A)//// ‘Cardinal’(A) /// ‘Blanco Espanol’(A) // BlancoEspanol (A) / ‘Taylor’ (A)] to compare selection for seed yield improvement of large-seeded Andean beans. Seven hundred sixty seven F2-derived F3 (F2:3) families were produced for each population. Visual appraisal for total plant performance, combined with seed yield from non-replicated plots was used for selection of 551 families in F2:3, 182 families in F2:4, and 91 families in F2:5 in each population. Eight hundred twenty three F5:6 lines were developed from the 91 F2:5 families in each population. Visual selection, combined with seed yield in non-replicated plots was again used to select 294 lines in F5:6 in each population. Similarly, 44 highest yielding F5:7 lines were selected in AM 11833 and 39 F5:7 lines in AA 11834. Thus, single plant selections were made in the F2 and F5, and plants within each plot were harvested in bulk in F3, F4, F6, and F7. Thirty nine F5:8 lines from AA 11834 and 44 lines from AM 11833, parents, and checks were evaluated at Popayan and Quilichao, Colombia in 1998 and 1999. Selected lines in both populations, on average, out-yielded the mean of their large-seeded Andean parents. Mean yield of the lines selected from AM 11833 was 50% higher than AA 11834 lines. Twelve F5:8 lines out-yielded the highest yielding Andean parents G 19833 and A 483 in AM 11833, whereas only one line yielded significantly higher (p < 0.05) than the highest yielding parent A 483 in AA 11834. However, none of selected lines out-yielded small-seeded Middle American parents used in AM 11833 (A 686 and ‘Carioca’). The mean 100 seed-weight of AA 11834 was 36 g compared to 28 G for AM 11833 F5:8 lines. Selected lines had similar days to maturity as parents in AM 11833, and matured 3 d later in AA11834. Correlation coefficients between yield and 100 seed-weight were negative in both populations. Yield and days to maturity were positively correlated in AA 11834.

Seed compositional and disease resistance differences among gene pools in cultivated common bean

It is widely accepted that two major gene pools exist in cultivated common bean, one Middle American and one Andean. Recently another gene pool, designated as North Andean and a fourth group (not considered to be a distinct gene pool) have been reported by the senior author and his colleagues. Many of the agronomic and seed compositional attributes of the two major gene pools are well known, but the seed compositional value and disease resistance of the North Andean gene pool has not yet been characterized. To rectify this situation, the seed compositional characters, percentage of protein concentrations (phaseolin, lectin and alpha-amylase inhibitor), the nutrient elements (calcium, phosphorus, iron and zinc) and the disease and pest attributes (angular leaf spot, anthracnose, common bacterial blight and empoasca damage) were considered. The Middle American gene pool gave higher lectin, calcium, phosphorus, sulfur and zinc than the Andean gene pool but lower phaseolin and iron. The North Andean gene pool is more like the Andean gene pool for phaseolin, resistance to angular leaf spot and anthracnose from Andean pathogen isolates, but more like the Middle American gene pool for lectin, zinc, sulfur and resistance to anthracnose from Middle American pathogen isolates. On the other hand, it had the highest iron concentration and was more resistant to common bacterial blight. These results indicate the potential value of this gene pool in a common bean breeding program.

Genetic variability in cultivated common bean beyond the two major gene pools

It is generally accepted that two major gene pools exist in cultivated common bean (Phaseolus vulgaris L.), a Middle American and an Andean one. Some evidence, based on unique phaseolin morphotypes and AFLP analysis, suggests that at least one more gene pool exists in cultivated common bean. To investigate this hypothesis, 1072 accessions from a common bean core collection from the primary centres of origin, held at CIAT, were investigated. Various agronomic and morphological attributes (14 categorical and 11 quantitative) were measured. Multivariate analyses, consisting of homogeneity analysis and clustering for categorical data, clustering and ordination techniques for quantitative data and nonlinear principal component analysis for mixed data, were undertaken. The results of most analyses supported the existence of the two major gene pools. However, the analysis of categorical data of protein types showed an additional minor gene pool. The minor gene pool is designated North Andean and includes phaseolin types CH, S and T; lectin types 312, Pr, B and K; and mostly A5, A6 and A4 types alpha-amylase inhibitor. Analysis of the combined categorical data of protein types and some plant categorical data also suggested that some other germplasm with C type phaseolin are distinguished from the major gene pools.

Preferência Alimentar de Adultos de Diabrotica speciosa (Ger.) (Coleoptera: Chrysomelidae) por Genótipos de Feijoeiro

Testes para avaliar a resistencia de feijoeiro (Phaseolus vulgaris L.) a Diabrotica speciosa (Ger.) foram conduzidos com os genotipos Goiano Precoce, Jalo Precoce, PR 95105146, PR 95105142 (centro de domesticacao Andino, AN), Emgopa 201 Ouro e IAPAR 57 (centro de domesticacao Mesoamericano, MA), em 1998 e 1999, na Fazenda da UNESP-FCAV, Jaboticabal, SP, Brasil. Discos foliares obtidos de plantas com 20 dias de idade, mantidas em vasos, foram usados nos testes com e sem chance de escolha em BOD. No teste com chance de escolha 12 adultos foram confinados numa placa de Petri (140 mm de diâmetro), contendo dois discos de cada genotipo. No teste sem chance de escolha, foram confinados dois insetos numa placa de Petri (60 mm de diâmetro) com dois discos do genotipo a ser avaliado. No experimento de campo foram liberados 400 insetos e no 30o dia apos o plantio, quinze foliolos por parcela foram coletados para avaliacao do consumo foliar. Um experimento sem chance de escolha foi conduzido mantendo-se um vaso com um genotipo (com 20 dias de idade) em telados individuais cobertos com tecido voil onde liberaram-se 10 adultos por 72h. Os genotipos Emgopa 201 Ouro e IAPAR 57 (ambos MA) foram os mais preferidos nos testes conduzidos em BOD, campo e telados enquanto que os genotipos AN foram menos consumidos.

Broadening the Genetic Base of Common Bean Cultivars

Knowledge, access, and use of diversity available in cultivated and wild relatives are essential for broadening the genetic base of cultivars to sustain improvement. My objectives are to review briefly the origin, domestication, and organization of genetic diversity in Phaseolus beans, highlight production problems and traits deficient in the common bean (P. vulgaris L.) cultivars, cite sources of useful gemplasm, and review progress achieved in broadening the genetic base of cultivars. Phaseolus beans originated in the Americas. Only five species, P. acutifolius A. Gray, P. coccineus L., P. lunatus L., P. polyanthus Greenman, and P. vulgaris L. were domesticated. The interspecies diversity in relation to common bean is organized in primary, secondary, tertiary, and quaternary gene pools. Intraspecies diversity in common bean is separated into two major gene pools (Andean and Middle American). Cultivars are further divided into races, each with their distinguishing characteristics. Also, cultivars of dry seed and snap bean exist. Abiotic and biotic stresses limit common bean production. The genetic base of cultivars within market classes is narrow and inadequate level of resistance to common bacterial blight [caused by Xanthomonas campestris pv. phaseoli (Smith) Dye] and white mold [caused by Sclerotinia sclerotiorum (Lib) de Bary] exist in cultivars. High levels of resistance to these and other desirable traits exist in the relatives and gene pools of P. vulgaris Early maturity, adaptation to higher latitude, upright plant type, high pod quality and seed yield, and resistance to Bean common mosaic virus (a potyvirus) and/or rust [caused by Uromyces appendiculatus (Pers.:Pers.) Unger] have been bred into cultivars. However, most of the genetic variability available in the common bean races, gene pools, and wild relatives remains to be utilized. To maximize and sustain bean production, high yielding, high quality cultivars that are less dependent on water, fertilizer, pesticides, and manual labor should be developed. This need warrants sustained, comprehensive, and integrated genetic improvement, in which favorable alleles from cultivated and wild relatives are accumulated in superior cultivars. A three‐tiered breeding approach involving: (i) gene introgression from alien germplasm, (ii) pyramiding favorable alleles from different sources, and (iii) simultaneous improvement of multiple traits for common bean cultivars would be the most appropriate strategies to meet theses needs.

Combining ability for nodulation in common bean (Phaseolus vulgaris L.) genotypes from Andean and Middle American gene pools

Ten F1's obtained from crosses among five common bean genotypes of Andean (WAF 15, Mineiro Precoce and Batatinha) and Middle American (BAT 304 and Ouro) gene pools were assessed for their combining abilities for root nodulation with Rhizobium tropici strain CIAT 899. The plants were grown under controlled conditions and evaluated for number of nodules per plant (NN), nodule dry weight (NDW), mean nodule weight (MNW) and plant fresh weight (PFW). The subdivision of the treatment effects on the general (GCA) and specific combining effects (SCA) were performed according to Griffing's diallel analysis method 2, model 1. The analyses of variance and estimates of quadratic components showed that non-additive gene effects were more important in the expression of NN and PFW, whereas additive gene effect was predominant for NDW and MNW. A close association was observed between high number of nodules and GCA. Generally, crosses involving parents of different gene pools yielded hybrids with high positive estimates of SCA for all assessed traits. The genotypes of Andean origin WAF 15 and Mineiro Precoce are the most promising parents for breeding programs to increase NN and NDW in common beans.

Seismic tomography with local earthquakes in Costa Rica

The Costarican isthmus is located at the western limit of the Caribbean oceanic plateau, where the Cocos plate subducts along the Middle American Trench. This plate shows strong lateral variations in its morphology and structure. The main objective of this study is to investigate the effects of subduction-related magmatism as a function of morphology and structure of the subducting plate, by performing a simultaneous inversion of the 3-D crustal velocity field and hypocenter locations from local earthquakes. For that, we used the traveltimes of P-waves first arrivals from more than 5000 events, recorded at the Costarican seismic networks between 1991 and 1998. In order to prevent data and modeling inaccuracies, we followed an inversion scheme consisting of four steps. (1) Selection of an adequate data subset for tomographic inversion, (2) estimation of the best reference 1-D model, (3) determination of the finest parameterization and (4) evaluation of resolution. The results show that the uppermost levels of the crust (0–6 km) are consistent with geology, since the velocity anomalies reflect the most meaningful geological features observed in the surface. Below these levels (6–20 km deep), we found two different zones separated by a SW–NE seismic alignment. The northern part is characterized by a highly heterogeneous velocity field and is seismically active, while the southern part is much more homogeneous and practically inactive. Moreover, the northern part shows a certain accumulation of low velocity material within the upper mantle. We suggest and illustrate that the structural differences between the northern and southern zones can be a consequence of the differences on the geometry and structure of the subducting slab.

Lithium isotopic compositions of pore fluids and sediments in the Costa Rica subduction zone: implications for fluid processes and sediment contribution to the arc volcanoes

Pore fluid and sediment Li concentrations and isotopic ratios provide important insights on the hydrology, sediment contribution to the arc volcanoes and fluid–sediment reactions at the dominantly non-accretionary Costa Rica subduction zone. Ocean Drilling Program Site 1039 in the trench axis provides a reference section of 400 m of the incoming sediments, and Site 1040, situated arcward from the trench, consists of a deformed sedimentary wedge and apron sediments, the décollement, and the partially dewatered underthrust sediment section. At the reference site, pore fluids show important isotopic variations (δ 6Li=−21.7 to −37.8‰), reflecting the interplay of in situ alteration of volcanic material and ion exchange with clay minerals. In the basal section, a reversal of Li concentration and δ 6Li toward seawater values is observed, providing supporting evidence for a lateral seawater flow system in the upper oceanic basement underlying this sediment section. At Site 1040, pore fluid of the lower deformed wedge sediments and within the décollement is enriched in Li and the isotopic compositions are relatively light, suggesting infiltration of a deep-seated fluid. The δ 6Li value of −22‰ of this Li-enriched fluid (261 μM), when compared with the δ 6Li value of the subducted sediment section (−11‰), suggests that the deep source fluid originates from mineral fluid dehydration and transformation reactions at temperatures of 100 to 150°C, consistent with the temperature range of the up-dip seismogenic zone and of transformation of smectite to illite. The distribution of Li and its isotopes in the underthrust section are similar to those at the reference site, indicating near complete subduction of the incoming sediments and that early dewatering of the underthrust sediments occurs predominantly by lateral flow into the ocean. The hemipelagic clay-rich sediment section of the subducting plate carries most of the Li into this subduction zone, and the pelagic diatomaceous and nannofossil calcareous oozes contain little Li. The Li isotopes of both the clay-rich hemipelagic sediments and of the pelagic oozes are, however, similar, with δ 6Li values of −9 to −12‰. The observations that (1) the δ 6Li values of the underthrust sediments are distinctly lower than that of the mantle, and (2) the lavas of the Costa Rican volcanoes are enriched in Li and 7Li, provide an approximation of the contribution of the subducted sediments to the arc volcanoes. A first order mass balance calculation suggests that approximately half of the Li flux delivered by subducted sediments and altered oceanic crust into the Middle American Trench is recycled to the Costa Rican arc and at most a quarter of sedimentary Li is returned into the ocean through thrust faults, primarily the décollement thrust.

Southern Distinctiveness, Yet Again, or, Why America Still Needs the South

In 1976 Democratic Party nominated a true blue son of South--Jimmy Carter--to be its presidential candidate. During that campaign, and especially after Carter's election, things southern--from rednecks and born-again Protestantism to potlikker and red-eye gravy--were journalistic rage. Southerners did things differentially, they--we--spoke differently, we ate different kinds of food, we believed and acted differently, and, during those early Carter years, national media seemed entranced by southernness of it all, believing themselves, I suppose, called first to understand South and then to help American people--or at least non-southerners among us--understand it too. I was finishing graduate school in Baltimore at time, and I remember my Yankee friends asking me an inordinate number of questions about South, about being southern. Of course, I was neither first nor last southerner to have enjoyed that particular pleasure: southerners have been explaining, telling about, South for generations.(1) We saw some of same curiosity--this attention to southernness--in 1992 presidential election, but by then novelty of a southerner sitting in White House had worn off, and, anyway, Arkansan Bill Clinton gave country other things to talk about. And if sometimes-southerner Al Gore wins 2000 election, I doubt very much that region will again be scrutinized and stared at as it was in late 1970s. Still, Gore's real but delicate Tennessee roots, as Los Angeles Times puts it, have motivated some media attention already, and I suspect more is to come. past is never dead. It's not even William Faulkner once said, and I think he's right.(2) In South, to be sure, past is not past, but even in America, past is not even past, if topic is South. The reasons for this are easy enough to understand. All know that until quite recently--say, 1970s--the relationship between South and America was strained, to say very least, and it had been so for two centuries or more: from antebellum slavery debates through Civil War and Reconstruction to modern Civil Rights movement of 1950s and 1960s, region and nation were at odds. Indeed, South and America fought--politically, legally, culturally, and even militarily--and that conflicted, sorrowful past is not easily forgotten. As title of a 1998 New York Times article has it, South's History Rises, Again and Again. No culture, of course, exists only in present: all draw on, hark back to, a past significant precisely because of its continued moral, identity, and emotional utility. In this South is no different, but what is unusual is how explicitly, how routinely, and how pervasively region's history, that very particular southern past, is evoked in present: South of then is recreated and oddly memorialized, concretized in a sense, in South of now.(3) Images abound of South's past continuing to rise again and again, and some of those most sharply etched--in particular, those that portray in one way or another conflict between nation and region, or South's outcast nature--are found in today's newspaper. A special section of very first issue of New York Times to appear in new century, titled Reflections on Century Past and Decades Ahead, included interviews with individuals for whom twentieth century's signal moments remain vivid memories and with those who, according to Times, inherit this history. Not surprisingly, people interviewed were from places with histories heavy with drama and death, shame and struggle, pain and possibility: India, Cambodia, and Germany, Russia and China, South Africa and Middle East, and Detroit and American South. Two southerners were interviewed about past and future of race and rights in region, and, perhaps paradoxically suggesting continuity amidst change, were from localities about as opposite in cultural trajectory as one could imagine, that New South symbol (or perhaps No-South symbol), Atlanta, and what historian James Cobb has called the most Southern place on earth, Mississippi Delta. …

Cerro Grande volcano: the evolution of a Miocene stratocone in the early Trans-Mexican Volcanic Belt

Cerro Grande volcano is a well-preserved, low-angle composite volcano that evolved between 11 and 9 Ma. It represents the beginning of volcanism in the eastern sector of the early Trans-Mexican Volcanic Belt. Extensive field, stratigraphic and petrologic work revealed a complex volcanic evolution that can be summarized in six principal stages. (I) construction of a shield-like lava cone; (II) generation of unusual lithic-rich ignimbrites, apparently related to powerful eruptions that caused rapid and significant vent erosion — these eruptions could have resulted from shallow magma–water interactions; (III) eruption of peripheral fissural lava flows following a NNW–SSE-trending fissure system; (IV) period of dome growth and explosive collapse; (V) short period of repose followed by open-vent explosive magmatic and hydromagmatic eruptions; (VI) radial eruption of lava flows, related to a ring-fissural system. Geochemistry data of late Miocene volcanics show a continental arc magmatic origin, and show that crystal fractionation contributed strongly to magma differentiation. Several lava flows were erupted with a persistent NNW–SSE-trending orientation, and the entire late Miocene geologic record is affected by highly dislocated normal faults with the same orientation; this may indicate that late Miocene volcanism was under tectonic control. Finally, late Miocene volcanics, and the inception of the early Trans-Mexican Volcanic Belt, could be related to a shallow subduction angle influenced by a significant increase in the convergence rate along the Middle American Trench at about 20 Ma.

New insights into the subducting oceanic crust in the Middle American Trench off western Mexico (17–19°N)

We present new multibeam bathymetric and multichannel seismic data on the Middle American Trench, between 17 and 19°N. These data show, north of the present tip of the East Pacific Rise, unsedimented seafloor with an abyssal hill fabric bare of sediments at the outer wall of the trench (18°30′N). Two multichannel seismic profiles orthogonal to the Middle American Trench display clear oceanic crust extending more than 20 km beneath the overriding plate. These seismic images suggest that the subducting oceanic crust along the Middle American Trench is younger than previously proposed. This result, therefore, implies a new location for the East Pacific Rise termination in relation to the trench. The subduction of this young oceanic crust off western Mexico provides new constraints on the deformation and magmatism of the western Mexican mainland.

Middle Powers and American Foreign Policy: Lessons from Irano-U. S. Relations, 1962-77

By examining the lessons of Irano-US. relations, the article contends that a post-Cold War American foreign policy relying on middle powers can achieve American security interests while avoiding the potential for excessive entanglements arising from a direct role. The effective implementation of this policy is argued to be consistent with the promotion of regional stability and the diffusion of democracy.

Molecular Phylogenetic Analysis of Relationships of the Tropical Salamander GeneraOedipinaandNototriton, with Descriptions of a New Genus and Three New Species

Abstract Sequences of two mitochondrial genes (385 base pairs of cytochrome b and approximately 520 base pairs of 16S DNA) were gathered for 26 taxa of the Middle American plethodontid salamander genera Nototriton and Oedipina and from three outgroup members of the tribe Bolitoglossini. Phylogenetic analyses of these data reveal well-supported cladistic structure and demonstrate the paraphyly of the moss salamanders of the genus Nototriton, which includes two well-defined clades. One clade, the sister taxon of Oedipina, corresponding to the Costa Rican and Honduran species of the picadoi, richardi, and barbouri groups, retains the name Nototriton. A new name is required for the second clade, the sister taxon of Oedipina plus Nototriton (sensu stricto). This clade, which we name Cryptotriton, is well supported morphologically and includes the species of the nasalis and adelos groups. A new species of Nototriton from Monteverde, Costa Rica, is described as Nototriton gamezi. Species of Oedipina fall into tw...