The low oxygen levels at high altitude are a potent and unavoidable physiological stressor to which highland mammals must adapt. One hypothesized adaptation to high altitude is an increased reliance on carbohydrates to support aerobic activities. Based on stoichiometries of combustion, ATP yield per mole of oxygen from carbohydrates is approximately 15% higher than from lipids (observed difference closer to 30%), and increased carbohydrate use represents an important oxygen-saving strategy that may be under high selective pressure. Although this hypothesis was first proposed nearly 30 years ago, the in vivo patterns of whole-body fuel use during exercise remain undefined for any highland mammal (including humans). Here we use a powerful multispecies approach to show that wild-caught high-altitude (4,000-4,500 m) native species of mice (Phyllotis andium and Phyllotis xanthopygus) from the Peruvian Andes use proportionately more carbohydrates and have higher oxidative capacities of cardiac muscles compared to closely related low-altitude (100-300 m) native counterparts (Phyllotis amicus and Phyllotis limatus). These results strongly infer that highland Phyllotis have evolved a metabolic strategy to economize oxygen when performing energy-demanding tasks at altitude. This study provides compelling evidence of adjustments in fuel use as an adaptation to high-altitude hypoxia in mammals.

No abstract

BackgroundUnderstanding the forces that shaped Neotropical diversity is central issue to explain tropical biodiversity and inform conservation action; yet few studies have examined large, widespread species. Lowland tapir (Tapirus terrrestris, Perissodactyla, Tapiridae) is the largest Neotropical herbivore whose ancestors arrived in South America during the Great American Biotic Interchange. A Pleistocene diversification is inferred for the genus Tapirus from the fossil record, but only two species survived the Pleistocene megafauna extinction. Here, we investigate the history of lowland tapir as revealed by variation at the mitochondrial gene Cytochrome b, compare it to the fossil data, and explore mechanisms that could have shaped the observed structure of current populations.ResultsSeparate methodological approaches found mutually exclusive divergence times for lowland tapir, either in the late or in the early Pleistocene, although a late Pleistocene divergence is more in tune with the fossil record. Bayesian analysis favored mountain tapir (T. pinchaque) paraphyly in relation to lowland tapir over reciprocal monophyly, corroborating the inferences from the fossil data these species are sister taxa. A coalescent-based analysis rejected a null hypothesis of allopatric divergence, suggesting a complex history. Based on the geographic distribution of haplotypes we propose (i) a central role for western Amazonia in tapir diversification, with a key role of the ecological gradient along the transition between Andean subcloud forests and Amazon lowland forest, and (ii) that the Amazon river acted as an barrier to gene flow. Finally, the branching patterns and estimates based on nucleotide diversity indicate a population expansion after the Last Glacial Maximum.ConclusionsThis study is the first examining lowland tapir phylogeography. Climatic events at the end of the Pleistocene, parapatric speciation, divergence along the Andean foothill, and role of the Amazon river, have similarly shaped the history of other taxa. Nevertheless further work with additional samples and loci is needed to improve our initial assessment. From a conservation perspective, we did not find a correspondence between genetic structure in lowland tapir and ecogeographic regions proposed to define conservation priorities in the Neotropics. This discrepancy sheds doubt into this scheme's ability to generate effective conservation planning for vagile species.

The southernmost limit of the distribution of endemic Andean cutaneous leishmaniasis (CL), commonly known as Uta, is localized in the western Andean valleys of Ayacucho, Peru. This area is completely isolated from other regions endemic for this disease. Identification of the insect vector for Andean CL was carried out by combining entomologic and parasitologic approaches. Two Lutzomyia species were captured: Lutzomyia ayacuchensis and Lu. noguchii. The former species was considered responsible for transmission of Leishmania because 1) there was a coincidence in space and time between the presence of this insect and the distribution of Andean CL, 2) it was shown to be highly anthropophilic, 3) Leishmania parasites of the subgenus Viannia were detected by a specific polymerase chain reaction assay, 4) promastigotes isolated from this insect were shown by multilocus enzyme electrophoresis and molecular karyotyping to belong to the same deme of Leishmania (Viannia) peruviana as the one circulating in humans living in the study area, and 5) the complete cycle of L. (V.) peruviana was observed in experimental infections of Lu. ayacuchensis. Parasite and vector homogeneity found in Ayacucho contrasted with the heterogeneity reported for other areas endemic for Andean CL. The potential influence of ecologic determinants on this geographically isolated area is discussed.

Leishmanial organisms isolated from 24 patients with Andean cutaneous leishmaniasis (uta) and from 7 with sylvatic leishmaniasis in both cutaneous and mucosal forms were characterized on the basis of their isoenzyme profiles for 13 enzymes using both cellulose acetate (CA) and thin-layer starch gel (TLS) electrophoretic techniques. Malate dehydrogenase (MDH) after electrophoresis on CA or TLS and mannose phosphate isomerase (MPI) on TLS were the only enzymes of 13 examined which discriminated between the organisms from patients with uta (L. (V.) peruviana) and those with sylvatic leishmaniasis (L. (V.) braziliensis). Mannose phosphate isomerase gave more clear-cut and reproducible discrimination than did MDH on either TLS or CA, and it is suggested that MPI is a reliable enzyme marker that can be used in routine TLS electrophoresis to distinguish between L. (V.) peruviana and L. (V). braziliensis.

In this article we present some aspects related to the population ecology of Mus musculus at the beginning and throughout the course of the dry season in the Lachay lomas. Population abundance in three zones with different altitudes decreased drastically during the dry season. Sex proportions showed that the number of males was always higher than the number of females. Home range was not statistically different between the three analyzed areas. Our results suggest that the presence and/or abundance of plants may be one of the most important in regulating the population this species. In addition our study suggests the hypothesis that females of Mus musculus are more sensitive tha males to the adverse climatic conditions in the Lachay National Reserve during dry season.

No abstract

No abstract