Montecino V.,University of Chile |
Molina X.,University of Chile |
Molina X.,POCH Ambiental SA |
Bothwell M.,Environment Canada |
And 7 more authors.
Science of the Total Environment | Year: 2016
We document the distribution of Didymosphenia geminata in central-southern Chilean rivers and identify the chemical and physical factors associated with its presence/absence (p/a). Repeated surveys in five successive years provided evidence that D. geminata could be nearing a biogeographic equilibrium in the region. D. geminata databases from extensive biological and environmental surveys in 187 rivers, within ten catchments, south of 38°S commenced in November 2010 and ran through May 2013. In addition, data from two other field surveys were used. The sites evenly distributed latitudinally were climatically characterized. The recent sampling program, following a published species distribution model, was designed to explore D. geminata distribution within thirteen catchments (34°S-48°S). An extensive river survey in 2014 (spring-summer) and in 2015 (autumn) included the p/a, and relative abundance of D. geminata cells in phytobenthos and in the drift. These p/a results showed that the probability of re-encountering D. geminata cells at sites where the species was previously found was significantly high while the probability of finding D. geminata cells at sites previously without the species was significantly low. This suggests that the distribution of D. geminata cells among suitable habitats was nearing completion. The relative abundance of D. geminata cells in the phytobenthos versus in the drift indicates seasonality with higher proportion of cells in the phytobenthos during the spring-summer than during the autumn. During the final surveys, principal component analysis of chemical and physical characteristics of rivers showed significant differences between rivers with and without D. geminata. Based on our observations of the distribution of D. geminata cells among rivers with suitable habitat conditions and the fluctuating rate of spread between rivers, we conclude that D. geminata is probably in the ending stage of its spatial demographic expansion in Chile surmounting the different barriers of the invasive process. © 2016 Elsevier B.V.
Guichon R.A.,CONICET |
Buikstra J.E.,Arizona State University |
Stone A.C.,Arizona State University |
Harkins K.M.,Arizona State University |
And 6 more authors.
International Journal of Paleopathology | Year: 2015
This work contributes to ongoing discussions about the nature of tuberculosis in the Western Hemisphere prior to the time of European contact. Our example, from the extreme south of South America was, at the time of our study, without firm temporal association or molecular characterization. In Tierra del Fuego, Constantinescu (1999) briefly described vertebral bone lesions compatible with TB in an undated skeleton from Myren 1 site (Chile). The remains of Myren are estimated to represent a man between 18 and 23 years old at the time of death. The objectives of this research are to extend this description, to present molecular results, to establish a radiocarbon date, and to report stable isotopic values for the remains. We provide further description of the remains, including tuberculosis-like skeletal pathology. Radiocarbon dating of 640. ±. 20 years BP attributes this individual to the precontact fourteenth-fifteenth centuries. Isotopic ratios for nitrogen and carbon from bone collagen suggest a mixed diet. Molecular results were positive for the rpoB quantitative PCR (qPCR) assays but negative for two independent IS6110 and IS1081 qPCR assays. Further testing using genomic methods to target any mycobacteria for specific identification are needed. © 2015 Elsevier Inc..
Montecino V.,University of Chile |
Molina X.,University of Chile |
Molina X.,POCH Ambiental SA |
Kumar S.,Colorado State University |
And 2 more authors.
Aquatic Invasions | Year: 2014
Aquatic invasive species are a major threat to native freshwater ecosystems and cause enormous ecological and economic damage worldwide. Didymosphenia geminata (Lyngbye) M. Schmidt is an emerging invasive aquatic species that is spreading aggressively in Southern South America. Using niche analysis and species distribution models (SDMs), we examined niche requirements of D. geminata using climatic, topographic, and biological variables. We compared the realized niche of the species in the United States (US) with the niche in Chile. Within Chile, we also examined the environmental conditions (environmental envelopes) of rivers with and without this alga, to assess whether this species has the potential to colonize more rivers. Finally, we compared the SDMs from the US and Chile projected to Chile. Results showed that the potential distribution of D. geminata varied significantly between US and Chile. The US-based model predicted a geographic distribution in Chile which ranged from 32º to 55º S latitude while the Chile-based model predicted suitable habitats only from 36° to 48º S, and not so in the coastal ranges nor in Southern Patagonia (̴ 52-55°S). In Chile, we found no differences in the environmental envelopes of the invaded and uninvaded rivers, thus suggesting that this species has even more suitable habitats to invade. These results can be used for prioritizing survey sites in Southern Chile for an early detection and management of D. geminata and for the conservation of native flora and fauna in freshwater ecosystems in Chile. © 2014 REABIC.
Cavieres L.A.,University of Concepcion |
Cavieres L.A.,Institute Ecologia y Biodiversidad IEB |
Penaloza A.,POCH Ambiental SA
Perspectives in Plant Ecology, Evolution and Systematics | Year: 2012
Most of the studies that have evaluated the interplay between interference and facilitation have been done at the interspecific level, whereas studies at the intraspecific level are scarce. The montane sclerophyllous forests of central Chile are dominated by the tree Kageneckia angustifolia, a semi-deciduous species that lose part of its foliage during summer. It has been reported that during winter snow accumulates in lower amounts beneath the canopy of K. angustifolia favoring the recruitment of new individuals compared to open areas (i.e., facilitation effect). However, it has also been reported that the leaf litter accumulated beneath parental trees contains allelopathic compounds that decrease seed germination, suggesting that recruitment beneath parental plants can be disfavored (i.e., interference effect). Hence, this system seems appropriate to assess the net-outcome between facilitative and negative effects during the emergence and survival of seedlings during the first year. In this study, we asked (i) what is the net-outcome between facilitative and interfering effects for K. angustifolia? (ii) does this net-outcome varies with the distance to parental trees? (iii) are positive and negative effects consistent through the seedling emergence and first year seedling survival phases? (iv) what are the main mechanisms behind the observed net-outcome? and (v) which is the optimal microhabitat for successful recruitment of this species? In an experimental plot of 10,000m 2, we selected ten K. angustifolia trees and evaluated the effect of leaf litter on the emergence and survival of seedlings produced by experimentally sown seed seeds in three different microhabitats: beneath adult trees, edge of canopy and in open areas. In addition, we sampled three K. angustifolia stands to evaluate the microhabitat where the natural recruitment of this species actually occurring. Results showed that (1) seedling emergence was greater beneath canopy, intermediate in canopy edge and low in open areas, (2) whilst leaf litter significantly reduced seed germination, the magnitude of this negative effect was lower than the positive effect of beneath canopy microhabitat, (3) seedling survival was affected by microhabitats but not by the presence of leaf litter, (4) that the main mechanisms behind the observed patterns are the lower and delayed emergence of seedlings in open areas due to the longer duration of snow cover, decreasing the time to growth before the onset of summer drought, and (5) the greatest natural recruitment of K. angustifolia seedlings occurs beneath parental plants. Therefore, our findings suggest that the net-outcome between facilitative and interfering effect during the first year is mostly facilitative, indicating that adult trees of K. angustifolia are exerting a conspecific nurse effect on the recruitment of new individuals, a form of parental care in plants. © 2011 Perspectives in Plant Ecology, Evolution and Systematics.
Pfeiffer M.,University of Chile |
Mascayano C.,POCH Ambiental SA |
Aburto F.,University of Chile |
Aburto F.,University of California at Davis
Eurasian Soil Science | Year: 2010
Previous studies have shown that the area between the present Northern and Southern Patagonian Ice Fields (47°S to 48°S) was covered with ice during the Last Glacial Maximum (16000 BP). The ice retreat generated a typical glacial geomorphology with moraines, kettles, kame terraces, fluvioglacial terraces and fluvial terraces. Until now, there have been no detailed studies to determine the type of soils in the area. We described and classified one hundred and fifty pedons located in the Baker River Basin (47°S) and the Pascua River Basin (48°S), which we correlate with the respective geomorphology. The mean annual precipitation is 1000 mm for the Baker River study area and 2500 mm for the Pascua River Basin area, whereas the average annual temperature is 9°C and 7°C, respectively. Based on previous studies that described the glacial fluctuations of the Northern and Southern Ice Fields and considering the presence of a volcanic ash layer due to the major Holocene eruptions of the Hudson Volcano (6700 BP), tentative soil profile ages are proposed, and the geomorphologic and soil descriptions are presented. Soils are classified as Entisols, Inceptisols, and Histosols, reflecting weak pedogenetic development, and consistent with the landscape age and climatic conditions. © 2010 Pleiades Publishing, Ltd.