Late Carboniferous intra-arc sediments in the north Chilean Andes: Stratigraphy,paleogeography and paleoclimate

Summary Thick terrestrial Late Carboniferous to Triassic volcanosedimentary successions, a prominent feature of the Chilean and Argentinian High Andes, were formed on the active continental margin of Gondwanaland. Their stratigraphic position and the paleogeographic and paleoclimatic relations to neighbouring successions are poorly defined. A more precise age has been obtained for alluviolimnic intra-arc sediments (Miembro Medio), which are intercalated in the Late Carboniferous-Triassic volcano-sedimentary successions in the Salar de Atacama area of northern Chile. The ostracodesCarbonita cf.pungens andParaparchites sp., which occur in the lower part of the Miembro Medio, are of Late Carboniferous, probably Westphalian age. The diverse taphoflora, which occurs in a higher stratigraphic level than the ostracodes, includes sphenophytes, ferns, gymnosperms and pteridophylls, for which we assume a late Westphalian-Early Permian age. Considering radiometric data of under-and overlying volcanic rocks, a Westphalian-Stephanian (to? Early Permian) age is inferred for the Miembro Medio. Fauna and flora indicate that warm-humid and seasonal climatic conditions existed during the deposition of the lower fossiliferous part of the Miembro Medio. This coincides with the sedimentary paleoclimatic indicators of the Miembro Medio and the climate which was assumed to have predominated in wide parts of the Central and Southern Andes during the Latest Carboniferous.     

Neoboeckella loffleri (Copepoda: Calanoida), a new species and genus from Bolivian fresh waters

A new species and genus of freshwater calanoid, Neoboeckella loffleri, is described from shallow, high-altitude waters. N. kinzeli (Löffler), 1955, is also included in the new genus. Neoboeckella, like Hemiboeckella Sars from Australia, is characterized inter alia by an exceptionally high degree of sexual dimorphism in size.     

The Work of Indebtedness: The Traumatic Present of Late Capitalist Chile

In political and biomedical discourses, "posttraumatic stress disorder" has become a set of organizing concepts for trauma and traumatic memory. These concepts, however, are predicated on an understanding of traumatic memory as a discrete etiological event that, when reexperienced, is productive of symptoms. In this essay, I explore alternative framings of trauma that arise out of historical changes in political economic language and from experiences of monetary, historical, and affective indebtedness in Santiago, Chile. This ethnographic research is based in an historically leftist población (poor urban sector) and follows the interwoven narratives of a formerly exiled communist militant and her adopted daughter. Throughout this essay, I describe the mother's attempts to inhabit an untimely language of socialist politics and the daughter's rejection of both this language and her mother's pain. I elaborate on how these attempts are products of and productive of monetary and intersubjective indebtedness in a neoliberal present. By describing the differing historical languages inhabited by these subjects, I attempt to evoke an understanding of trauma not as an individual possession or etiological event, but rather as a referential dissonance in the neoliberal context. This referential dissonance emerges from the gap between the historical languages that inform subjectivities. I explore how such a gap can create contexts in which the everyday itself both threatens the disarticulation of the subject and produces injurious affective relationships. In this way, I interrogate relationships between trauma, recovery, and the everyday.     

Molecular analysis of enrichment cultures of ammonia oxidizers from the Salar de Huasco,a high altitude saline wetland in northern Chile

We analyzed enrichment cultures of ammonia-oxidizing bacteria (AOB) collected from different areas of Salar de Huasco, a high altitude, saline, pH-neutral water body in the Chilean Altiplano. Samples were inoculated into mineral media with 10 mM NH₄ ⁺ at five different salt concentrations (10, 200, 400, 800 and 1,400 mM NaCl). Low diversity (up to three phylotypes per enrichment) of beta-AOB was detected using 16S rDNA and amoA clone libraries. Growth of beta-AOB was only recorded in a few enrichment cultures and varied according to site or media salinity. In total, five 16S rDNA and amoA phylotypes were found which were related to Nitrosomonas europaea/Nitrosococcus mobilis, N. marina and N. communis clusters. Phylotype 1-16S was 97% similar with N. halophila, previously isolated from Mongolian soda lakes, and phylotypes from amoA sequences were similar with yet uncultured beta-AOB from different biofilms. Sequences related to N. halophila were frequently found at all salinities. Neither gamma-AOB nor ammonia-oxidizing Archaea were recorded in these enrichment cultures.     

Effects of low water supplementation and nutrient addition on the aboveground biomass production of annual plants in a Chilean coastal desert site

Summary The effects of low water supplementation and nutrients on the aboveground biomass production of annual plants was tested in the field by mimicking small rainfall events of 5mm per month and by adding fertilizers to experimental quadrats. Field measurements were made during an extremely dry year, so the potential additional effects of rainfall probably had no important effect on plant responses. Biomass of non-native species was higher in irrigated than in non-irrigated quadrats. No significant responses to irrigation treatments were detected in native species. This lack of response may be due to higher thresholds of watering being required for either germination and/or growth. Because of the low water inputs, fertilizer additions did not promote any biomass response in either native or non-native species. Responses of non-native species to low and frequent pulses of water, which is characteristic of this arid system, may be important for the persistence of these species in this environment.This is a contribution of the Program of Arid zone Studies of Universidad de La Serena     

Mating success of the endemic Des Murs’ Wiretail (Sylviorthorhynchus desmursii,Furnariidae) in fragmented Chilean rainforests

Abstract: We studied the effects of fragment size, vegetation structure and presence of habitat corridors on the reproductive success of the Des Murs’ Wiretail (Sylviorthorhynchus desmursii Des Murs, Furnariidae), a small (10 g) understorey bird, endemic to South American forests. In a rural landscape of Chiloé Island, southern Chile (42°S; 70°W), we determined the mating and nesting success of wiretails in 28 territories distributed in seven small (1–20 ha) and two large (>300 ha) forest fragments during the 1997–1998 breeding season. Wiretails inhabited dense bamboo thickets in the understorey of forest patches, dense shrublands covering old fields, and dense early successional forest vegetation. Wiretails avoided open pastures. Reproductive success depended solely on the probability of finding mates, and the main factor affecting mating success was the presence of corridors. Mated individuals occupied 72% of the territories in forest patches <20 ha connected by corridors, 73% of the territories in large (>300 ha) fragments, but only 20% of territories in isolated fragments surrounded by pastures. Because of the rapid expansion of pastures in southern Chile, the conservation of wiretails and other understorey birds will depend on the maintenance of travel corridors with dense understorey vegetation between forest fragments.     

Populations and assemblages of parasites in hake, Merluccius gayi, from the southeastern Pacific Ocean: stock implications

To assess fish stocks, the populations and community assemblages of metazoan parasites were compared in 1172 Chilean hake Merluccius gayi landed at two major ports, and caught during 1991–1992 in three major fishing areas off central Chile. At least two ecological stocks are suggested, based on consistent differences in parasitism between body length classes for Grillotia dollfusi, Hysterothylacium sp., Clestobothrium crassiceps and Aporocotyle wilhelmi . More use should be made of the information on whole parasite assemblages including, for example, patterns of co-occurrence of parasite species. Univariate analyses on selected taxa in samples from different areas may show no differences because of the same prevalence or abundance for each parasite taxon, but opposite numerical arrangements of co-occurring taxa in community assemblages would remain undetected.