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Universidad Mayor
GEMA Center for Genomics, Ecology & Environment
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Wageningen University & Research
University of Strasbourg
Pontificia Universidad Católica de Chile
Pontificia Universidad Católica de Chile
University of Valencia
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Pontificia Universidad Católica de Chile
Pontificia Universidad Católica de Chile
Pädagogische Hochschule Heidelberg
Pontificia Universidad Católica de Chile
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INTERACCIONES GEOGRÁFICAS-AMBIENTALES: VINCULANDO LOS SISTEMAS SOCIO ECOLÓGICOS CON LA HISTORIA AMBIENTAL. VALLE EXPLORADORES, PATAGONIA OCCIDENTAL, REGIÓN DE AYSÉN
Establecer un marco conceptual y operacional para la compresión de las interacciones geográfico-ambientales en una escala local y su vinculación con los SESs, tomando como modelo de estudio el Valle Exploradores, Región de Aysén
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Research Items (32)
Background: Little is known about the global distribution and environmental drivers of key microbial functional traits such as antibiotic resistance genes (ARGs). Soils are one of Earth largest reservoirs of ARGs, which are integral for soil microbial competition, and have potential implications for plant and human health. Yet, their diversity and global patterns remain poorly described. Here, we analyzed 285 ARGs in soils from 1012 sites across all continents, and created the first global atlas with the distributions of topsoil ARGs. Results: We show that ARGs peaked in high latitude cold and boreal forests. Climatic seasonality and mobile genetic elements, associated with the transmission of antibiotic resistance, were also key drivers of their global distribution. Dominant ARGs were mainly related to multidrug resistance genes and efflux pump machineries. We further pinpointed the global hotspots of the diversity and proportions of soil ARGs. Conclusions: Together, our work provides the foundation for a better understanding of the ecology and global distribution of the environmental soil antibiotic resistome.
El rol de los herbívoros en el control de la riqueza de especies vegetales es un tema critico en la conservación. Diferentes investigaciones demuestran que los herbívoros aumentan la diversidad de las plantas, pero no necesariamente modifican la riqueza del banco de semillas del suelo, dependiendo de las condiciones ambientales. El objetivo de este trabajo es evaluar el efecto de la pérdida de herbívoros en la composición y estructura de plantas anuales y su respectivo banco de semillas en el matorral semiárido costero durante 10 años. Para ello, analizamos los índices de diversidad de comunidades de plantas anuales en presencia y ausencia de herbívoros en el experimento de largo plazo del Parque Nacional Fray Jorge.
The interplay between plants and soil drives the structure and function of soil microbial communities. In water-limited environments where vascular plants are often absent and only specialized groups of rootless plants grow, this interaction could be mainly asymmetric, with plants supporting nutrients and resources via litter deposition. In this study, we use observational approaches to evaluate the impact of local distribution of Tillandsia landbeckii across elevation on soil bacterial community structure and composition in the Atacama Fog Desert. Tillandsia landbeckii is a plant without functional roots that develops on meter-scale sand dunes and depends mainly on marine fog that transports resources (water and nutrients) from the Pacific Ocean. Our data show that soil bacterial abundance, richness, and diversity were significantly higher beneath T. landbeckii plants relative to bare soils. However, these differences were not significant across T. landbeckii located at different elevations and with different input of marine fog. On the other hand, bacterial community composition was significantly different with T. landbeckii plants across elevations. Further, samples beneath T. landbeckii and bare soils showed significant differences in bacterial community composition. Around 99% of all operational taxonomic units (OTUs) were recorded exclusively beneath T. landbeckii, and only 1% of OTUs were observed in bare soils. These findings suggest that the presence of T. landbeckii promotes significant increases in bacterial abundance and diversity compared with bare soils, although we fail to demonstrate that local-scale changes in elevation can affect patterns of soil bacterial diversity and abundance beneath T. landbeckii.
Despite the extensive area covered by the coastal Atacama fog Desert (18–32° S), there is a lack of understanding of its most notorious characteristics, including fog water potential, frequency of fog presence, spatial fog gradients or fog effect in ecosystems, such as Tillandsia fields. Here we discuss new meteorological data for the foggiest season (July–August–September, JAS) in 2018 and 2019. Our meteorological stations lie between 750 and 1211 m a. s. l. at two sites within the Cordillera de la Costa in the hyperarid Atacama (20° S): Cerro Oyarbide and Alto Patache. The data show steep spatial gradients together with rapid changes in the low atmosphere linked to the advection of contrasting coastal (humid and cold) and continental (dry and warm) air masses. One main implication is that fog presence and fog water yields tend to be negatively related to both distance to the coast and elevation. Strong afternoon SW winds advect moisture inland, which take the form of fog in only about 6% of the JAS at 1211 m a. s. l., but 65% at 750 m a. s. l. on the coastal cliff. Although sporadic, long lasting fog events embrace well-mixed marine boundary layer conditions and thick fog cloud between 750 and 1211 m a. s. l. These fog events are thought to be the main source of water for the Tillandsia ecosystems and relate their geographic distribution to the lowest fog water yields recorded. Future climate trends may leave fog-dependent Tillandsia even less exposed to the already infrequent fog resulting in rapid vegetation decline.
The hyperarid Atacama Desert coast receives scarce moisture inputs mainly from the Pacific Ocean in the form of marine advective fog. The collected moisture supports highly specialized ecosystems, where the bromeliad Tillandsia landbeckii is the dominant species. The fog and low clouds (FLCs) on which these ecosystems depend are affected in their interannual variability and spatial distribution by global phenomena, such as ENSO. Yet, there is a lack of understanding of how ENSO influences recent FLCs spatial changes and their interconnections and how these variations can affect existing Tillandsia stands. In this study, we analyze FLCs occurrence, its trends and the influence of ENSO on the interannual variations of FLCs presence by processing GOES satellite images (1995-2017). Our results show that ENSO exerts a significant influence over FLCs interannual variability in the Atacama at ~ 20°S. Linear regression analyses reveal a relation between ENSO3.4 anomalies and FLCs with opposite seasonal effects depending on the ENSO phase. During summer (winter), the ENSO warm phase is associated with an increase (decrease) of the FLCs occurrence, whereas the opposite occurs during ENSO cool phases. In addition, the ONI Index explains up to ~ 50 and ~ 60% variance of the interannual FLCs presence in the T. land-beckii site during summer and winter, respectively. Finally, weak negative (positive) trends of FLCs presence are observed above (below) 1000 m a. s. l. These results have direct implications for understanding the present and past distribution of Tillandsia ecosystems under the extreme conditions characterizing our study area.
The structure and function of the soil microbiome of urban greenspaces remain largely undetermined. We conducted a global field survey in urban greenspaces and neighboring natural ecosystems across 56 cities from six continents, and found that urban soils are important hotspots for soil bacterial, protist and functional gene diversity , but support highly homogenized microbial communities worldwide. Urban greenspaces had a greater proportion of fast-growing bacteria, algae, amoebae, and fungal pathogens, but a lower proportion of ectomy-corrhizal fungi than natural ecosystems. These urban ecosystems also showed higher proportions of genes associated with human pathogens, greenhouse gas emissions, faster nutrient cycling, and more intense abiotic stress than natural environments. City affluence, management practices, and climate were fundamental drivers of urban soil communities. Our work paves the way toward a more comprehensive global-scale perspective on urban greenspaces, which is integral to managing the health of these ecosystems and the well-being of human populations.
Coastal systems are highly productive areas for primary productivity and ecosystem services and host a large number of human activities. Since industrialization, metal micronutrients in these regions have increased. Phytoplankton use metals as micronutrients in metabolic processes, but in excess, had deleterious effects. In coastal systems, picoeukaryotes represent a diverse and abundant group with widespread distribution and fundamental roles in biogeochemical cycling. We combined different approaches to explore picoeukaryotes seasonal variability in a chronically metal polluted coastal area at the southeastern Pacific Ocean. Through remote and field measurements to monitor environmental conditions and 18S rRNA gene sequencing for taxo-nomic profiling, we determined metal chronic effect on picoeukaryote community's structure. Our results revealed a stable richness and a variable distribution of the relative abundance, despite the physicochemical seasonal variations. These results suggest that chronic metal contamination influences temporal heterogeneity of picoeukaryote communities, with a decoupling between abiotic and biotic patterns.
The variability of rainfall‐dependent streamflow at catchment scale modulates many ecosystem processes in wet temperate forests. Runoff in small mountain catchments is characterized by a quick response to rainfall pulses which affects biogeochemical fluxes to all downstream systems. In wet‐temperate climates, water erosion is the most important natural factor driving downstream soil and nutrient losses from upland ecosystems. Most hydrochemical studies have focused on water flux measurements at hourly scales, along with weekly or monthly samples for water chemistry. Here, we assessed how water and element flows from broad‐leaved, evergreen forested catchments in southwestern South America, are influenced by different successional stages, quantifying runoff, sediment transport and nutrient fluxes during hourly rainfall events of different intensities. Hydrograph comparisons among different successional stages indicated that forested catchments differed in their responses to high intensity rainfall, with greater runoff in areas covered by secondary forests (SF), compared to old‐growth forest cover (OG) and dense scrub vegetation (CH). Further, throughfall water was greatly nutrient enriched for all forest types. Suspended sediment loads varied between successional stages. SF catchments exported 455 kg of sediments per ha, followed by OG with 91 kg/ha and CH with 14 kg/ha, corresponding to 11 rainfall events measured from December 2013 to April 2014. Total Nitrogen (TN) and Phosphorus (TP) concentrations in stream water also varied with rainfall intensity. In seven rainfall events sampled during the study period, CH catchments exported less nutrients (46 kg/ha TN and 7 kg/ha TP) than SF catchments (718 kg/ha TN and 107 kg/ha TP), while OG catchments exported intermediate sediment loads (201 kg/ha TN and 23 kg/ha TP). Further, we found significant effects of successional stage attributes (vegetation structure and soil physical properties) and catchment morphometry on runoff and sediment concentrations, and greater nutrients retention in OG and CH catchments. We conclude that in these southern hemisphere, broad‐leaved evergreen temperate forests, hydrological processes are driven by multiple interacting phenomena, including climate, vegetation, soils, topography, and disturbance history. This article is protected by copyright. All rights reserved.
The importance of soil age as an ecosystem driver across biomes remains largely unresolved. By combining a cross-biome global field survey, including data for 32 soil, plant, and microbial properties in 16 soil chronosequences, with a global meta-analysis, we show that soil age is a significant ecosystem driver, but only accounts for a relatively small proportion of the cross-biome variation in multiple ecosystem properties. Parent material, climate, vegetation and topography predict, collectively, 24 times more variation in ecosystem properties than soil age alone. Soil age is an important local-scale ecosystem driver; however, environmental context, rather than soil age, determines the rates and trajectories of ecosystem development in structure and function across biomes. Our work provides insights into the natural history of terrestrial ecosystems. We propose that, regardless of soil age, changes in the environmental context, such as those associated with global climatic and land-use changes, will have important long-term impacts on the structure and function of terrestrial ecosystems across biomes.
Ecosystem functions in forests can vary significantly after disturbance, depending on changes in vegetation structure during succession and soil biophysical characteristics. We examined streamflow regulation, water storage and soil protection functions in small catchments covered by evergreen temperate rain forests, developed over volcanic ash soils, in southern South America. Our aims were to understand the differences in ecosystem functioning among catchments representing different forest stages following human disturbance, from scrubland to old-growth forest condition. In these catchments (n = 3 per condition), we assessed and compared eco-hydrological functions over 21 months. In old-growth (OG) forest catchments, streamflow for the entire study period averaged 2102 ± 110 mm, followed by secondary forest (SF) catchments with an average of 1770 ± 284 mm and finally scrub catchments (CH) with 1684 ± 267 mm. Evapotranspiration showed higher values in SF catchments (643 mm), followed by CH catchments (612 mm) and OG catchments (346 mm). OG and CH catchments had the lowest sediment export in streamflow, without statistical difference between them, while SF catchments had the highest sediment concentrations in all seasons of the year. Principal component analysis revealed that soil physical properties, vegetation structure and catchment morphometry were all relevant to explain the differences among the three forest successional stages compared. We validate the hypotheses that streamflow regulation and soil water storage capacity are greatly enhanced in old-growth forests, while the soil protection function is maximized in both early (bamboo-dominated) and advanced forest stages. Paper can be downloaded from: https://link.springer.com/content/pdf/10.1007%2Fs10021-019-00404-7.pdf
The role of soil biodiversity in regulating multiple ecosystem functions is poorly understood, limiting our ability to predict how soil biodiversity loss might affect human wellbeing and ecosystem sustainability. Here, combining a global observational study with an experimental microcosm study, we provide evidence that soil biodiversity (bacteria, fungi, protists and invertebrates) is significantly and positively associated with multiple ecosystem functions. These functions include nutrient cycling, decomposition, plant production, and reduced potential for pathogenicity and belowground biological warfare. Our findings also reveal the context dependency of such relationships and the importance of the connectedness, biodiversity and nature of the globally distributed dominant phylotypes within the soil network in maintaining multiple functions. Moreover, our results suggest that the positive association between plant diversity and multifunctionality across biomes is indirectly driven by soil biodiversity. Together, our results provide insights into the importance of soil biodiversity for maintaining soil functionality locally and across biomes, as well as providing strong support for the inclusion of soil biodiversity in conservation and management programmes. Combining field data from 83 sites on five continents, together with microcosm experiments, the authors show that nutrient cycling, decomposition, plant production and other ecosystem functions are positively associated with a higher diversity of a wide range of soil organisms.
p>Predicting the potential distribution of short-lived species with a narrow natural distribution range is a difficult task, especially when there is limited field data. The possible distribution of L. ovallei was modeled using the maximum entropy approach. This species has a very restricted distribution along the hyperarid coastal desert in northern Chile. Our results showed that local and regional environmental factors define its distribution. Changes in altitude and microhabitat related to the landforms are of critical importance at the local scale, whereas cloud cover variations associated with coastal fog was the principal factor determining the presence of L. ovallei at the regional level. This study verified the value of the maximum entropy in understanding the factors that influence the distribution of plant species with restricted distribution ranges.</p
Unlike plants and vertebrates, the ecological preferences, and potential vulnerabilities of soil invertebrates to environmental change, remain poorly understood in terrestrial ecosystems globally. We conducted a cross‐biome survey including 83 locations across six continents to advance our understanding of the ecological preferences and vulnerabilities of the diversity of dominant and functionally important soil invertebrate taxa, including nematodes, arachnids and rotifers. The diversity of invertebrates was analyzed through amplicon sequencing. Vegetation and climate drove the diversity and dominant taxa of soil invertebrates. Our results suggest that declines in forest cover and plant diversity, and reductions in plant production associated with increases in aridity, can result in reductions of the diversity of soil invertebrates in a drier and more managed world. We further developed global atlases of the diversity of these important soil invertebrates, which were cross‐validated using an independent database. Our study advances the current knowledge of the ecological preferences and vulnerabilities of the diversity and presence of functionally important soil invertebrates in soils from across the globe. This information is fundamental for improving and prioritizing conservation efforts of soil genetic resources and management policies.
Identifying the global drivers of soil priming is essential to understanding C cycling in terrestrial ecosystems. We conducted a survey of soils across 86 globally-distributed locations, spanning a wide range of climates, biotic communities, and soil conditions, and evaluated the apparent soil priming effect using 13C-glucose labeling. Here we show that the magnitude of the positive apparent priming effect (increase in CO2 release through accelerated microbial biomass turnover) was negatively associated with SOC content and microbial respiration rates. Our statistical modeling suggests that apparent priming effects tend to be negative in more mesic sites associated with higher SOC contents. In contrast, a single-input of labile C causes positive apparent priming effects in more arid locations with low SOC contents. Our results provide solid evidence that SOC content plays a critical role in regulating apparent priming effects, with important implications for the improvement of C cycling models under global change scenarios.
Belowground organisms play critical roles in maintaining multiple ecosystem processes, including plant productivity, decomposition, and nutrient cycling. Despite their importance, however, we have a limited understanding of how and why belowground biodiversity (bacteria, fungi, protists, and invertebrates) may change as soils develop over centuries to millennia (pedogenesis). Moreover, it is unclear whether belowground biodiversity changes during pedogenesis are similar to the patterns observed for aboveground plant diversity. Here we evaluated the roles of resource availability, nutrient stoichiometry, and soil abiotic factors in driving belowground biodiversity across 16 soil chronosequences (from centuries to millennia) spanning a wide range of globally distributed ecosystem types. Changes in belowground biodiversity during pedogenesis followed two main patterns. In lower-productivity ecosystems (i.e., drier and colder), increases in belowground biodiversity tracked increases in plant cover. In more productive ecosystems (i.e., wetter and warmer), increased acidification during pedogenesis was associated with declines in belowground biodiversity. Changes in the diversity of bacteria, fungi, protists, and invertebrates with pedogenesis were strongly and positively correlated worldwide, highlighting that belowground biodiversity shares similar ecological drivers as soils and ecosystems develop. In general, temporal changes in aboveground plant diversity and belowground biodiversity were not correlated, challenging the common perception that belowground biodiversity should follow similar patterns to those of plant diversity during ecosystem development. Taken together, our findings provide evidence that ecological patterns in belowground biodiversity are predictable across major globally distributed ecosystem types and suggest that shifts in plant cover and soil acidification during ecosystem development are associated with changes in belowground biodiversity over centuries to millennia.
Larger volumes of sea ice have been thawing in the Central Arctic Ocean (CAO) during the last decades than during the past 800,000 years. Brackish brine (fed by meltwater inside the ice) is an expanding sympagic habitat in summer all over the CAO. We report for the first time the structure of bacterial communities in this brine. They are composed of psychrophilic extremophiles, many of them related to phylotypes known from Arctic and Antarctic regions. Community structure displayed strong habitat segregation between brackish ice brine (IB; salinity 2.4–9.6) and immediate sub-ice seawater (SW; salinity 33.3–34.9), expressed at all taxonomic levels (class to genus), by dominant phylotypes as well as by the rare biosphere, and with specialists dominating IB and generalists SW. The dominant phylotypes in IB were related to Candidatus Aquiluna and Flavobacterium, those in SW to Balneatrix and ZD0405, and those shared between the habitats to Halomonas, Polaribacter and Shewanella. A meta-analysis for the oligotrophic CAO showed a pattern with Flavobacteriia dominating in melt ponds, Flavobacteriia and Gammaproteobacteria in solid ice cores, Flavobacteriia, Gamma- and Betaproteobacteria, and Actinobacteria in brine, and Alphaproteobacteria in SW. Based on our results, we expect that the roles of Actinobacteria and Betaproteobacteria in the CAO will increase with global warming owing to the increased production of meltwater in summer. IB contained three times more phylotypes than SW and may act as an insurance reservoir for bacterial diversity that can act as a recruitment base when environmental conditions change.
During soil development bacteria and fungi can be differentially affected by changes in soil biogeochemistry. Since the chemistry of parent material affects soil pH, nutrient availability, and indirectly litter quality, we hypothesize that parent material has an important influence on microbial community patterns during long-term soil development. 2. In this paper, we tested for the effect of parent material, as well as, soil and litter properties upon microbial community patterns in three ca. 20,000-year-old semiarid chronosequences developed on sedimentary and volcanic (i.e. Andesitic and Dacitic) soils in the Dry Puna of Bolivia. We evaluated microbial patterns by analyzing the Terminal Restriction Fragment Length Polymorphism (T-RFLP) from amplified bacterial 16S rRNA genes, and the fungal Internal Transcribed Spacer (ITS) region, and quantitative real time polymerase chain reaction (qPCR). 3. Soil and litter characteristics differed significantly between the Sedimentary and volcanic chronosequences. In particular, soil pH was alkaline in all stages of the Sedimentary chronosequence; whereas it changed from alkaline to near neutral across stages in both volcanic chronosequences. Composition of bacterial communities changed across volcanic chronosequences, and this change was associated with a reduction in soil pH and increases in litter quality, whereas no differences were found in the Sedimentary chronosequence. Fungal community composition, in contrast, did not change across any chronosequence. 4. Relative microbial abundance, expressed as the fungal:bacterial ratio, declined across stages of the Sedimentary chronosequence in association with decreases in TC and TP, whereas in the Andesitic chronosequence decreases in fungal:bacterial ratios were related with increases in litter quality and declines in soil pH. 5. Synthesis. Our results show the importance of parent material in affecting bacterial and fungal communities during soil development. Further, in semiarid chronosequences, fungal:bacterial ratios tend to decline given that soil pH in young soils is rather alkaline. Our results also are consistent with the general framework that highlights the importance of aboveground (i.e. litter quality) and belowground (i.e. soil properties) in affecting microbial relative abundance and community composition during soil development. This article is protected by copyright. All rights reserved.
This paper reports a quantitative survey of the composition, diversity and structure of the plant communities on six islands of Uyuni and Coipasa salt lakes (Bolivia). Plant communities on each island were examined via the use of 10 transects, along which species richness and abundance were recorded. Seventy-one species were found in total, representing pteridophytes (6%), gymnosperms (1%), monocotyledons (14%) and dicotyledons (79%). About 21% of the species were endemic or faced some degree of threat. The calculation of Shannon-Wiener α-diversity indices and comparisons of community structure revealed similarities between the islands. Indeed these analyses suggest the existence of a single floral assemblage; however, small differences in the plant communities were visually identified during fieldwork. These islands are home to a considerable subset of the Altiplano’s flora and appear to have been little disturbed. They should therefore be the subject of surveillance/conservation programs.
Background/Question/Methods Today, over half of humanity lives in cities and the expansion of urban areas is considered one of the greatest threats to biodiversity. Urbanization, negatively affects bird’s richness, abundances and reproduction because it constitutes a drastic habitat modification, and enhance inhospitable environment for many species. However, an important role of urban parks for bird’s populations, has been documented depending on park traits such as size, connectivity and vegetation structure. Moreover, despite the effect of parks, to understand the effects of urbanization on wildlife, an understudied driver of global biodiversity loss in urban context, is the simultaneous loss of biological and cultural diversity, and their replacement by cosmopolitan or exotic species. We aimed to explore the effect of park size, connectivity and native vegetation on bird’s populations and reproduction. At each season of 2014, bird richness and abundance were measured using 25 m fixed radius point counts in 51 urban parks. Then in 2015, we selected 17 parks, grouped in three-size categories: small (< 0.99 ha), medium (between 1 and 4.99 ha) and large (> 5 ha) and monitored every nest in the reproductive season to estimate the Mayfield reproductive index. Additionally, in spring 2014 in a subsample of ten parks, we surveyed 142 visitors, to understand the knowledge of birds and perceived diversity by urban citizens. Results/Conclusions We recorded a total of 39 bird species (36 native and 3 exotic), and results showed that significantly higher richness was observed in large parks in contrast to medium size and small parks. A total of 112 nests of 7 native species were monitored. We did not find any relation among the proportion of native vegetation with bird richness or abundances and park size or vegetation, on the reproductive success of urban birds. Thus, despite lower diversity, small parks did not reduce reproductive success. Finally, we discovered that people recognized just a limited number of bird species, mainly exotic ones, despite these species were the minority of species listed on the survey. Additionally, we found no relationship between perceived and estimated bird diversity, suggesting that people tend to underestimate biodiversity in urban parks. These results highlight the importance of large parks for bird’s conservation in an urban context, and the relevance to the scientific community and naturalists to boost a better appreciation of our natural heritage, through more innovative mechanisms to stimulate the flow of information on local biodiversity.
Multiple ecological factors are known to drive variation in social behavior. However, group-living in some species appears to be highly conserved, suggesting a phylogenetic influence. In this study, we evaluated both scenarios using intraspecific and interspecific comparisons across octodontid rodents. We first examined 2 different populations of Andean degu (Octodontomys gliroides), representing 2 extremes of a climate vegetation gradient across the Andes range. We evaluated how ecological variation in terms of abundance and distribution of food resources, predation risk, and burrowing costs predicted interpopulation variation in group size and range-area overlap (2 proxies of sociality). We estimated these measures of sociality from livetrapping and radiotelemetry. We then used phylogenetic methods to determine whether sociality exhibits a phylogenetic signal and reconstructed the ancestral state of sociality across the family Octodontidae. Overall activity of females and males of O. gliroides was greater during nighttime than daytime. Across populations we found significant differences in ecology, including abundance and distribution of food, predation risk, and burrowing costs. However, populations were similar in terms of group size and range-area overlap. The phylogenetic approach revealed a strong and significant phylogenetic signal associated with sociality, where this behavior was present early during the evolution of octodontid rodents. Together, these findings imply that sociality of O. gliroides is not linked to current population differences in ecology.
Background/Question/Methods Cloud cover is a major and nearly permanent feature (80% persistence) of the eastern Pacific Ocean in the arid and semiarid continental margin of South America. The cloud field is maintained at a fixed elevation (above 600 m) by a thermal inversion, providing the main or the only source of humidity for a chain of highly vegetated hotspots found along coastal hills from northern Peru to the semiarid margin of the Atacama Desert in Chile. In semiarid Chile (30 S, Fray Jorge Forest), a chain of isolated rainforest fragments occurs on coastal mountaintops inundated by oceanic fog, receiving only sporadic rainfall (annual mean=14 cm). Because fog is essential for the persistence of forest patches and their rich floristic assemblage, closely related to austral temperate rainforests, we initiated a quantitative study of decadal trends in cloud and rainwater inputs. We were interested in the constancy of fog inputs and their temporal synchrony with rainfall, in the face of variable and declining rainfall. For a period of 10 years, we kept monthly records of water inputs originated from passive cloud interception, stemflow, throughfall, and direct precipitation outside and inside six patches varying in size and at location in the semiarid landscape. Results/Conclusions Rainfall varied greatly among years, influenced by El Niño Southern Oscillation (ENSO), with unusually dry extremes of 10 mm, and unusually wet years reaching >200 mm. Rainfall declined by 12% in decade of study, despite a wet ENSO event in 2002. Peak rainfall is concentrated in the midst of the austral winter, July-August, followed by nearly 8 months of spring-summer drought. In contrast, fog inputs peaked in late spring and summer (September-February) providing moisture to the forest during the rainless period. We estimate that canopy interception and stemflow contributed an additional equivalent to 300 mm. The persistent cloud cover and low air temperatures (10-15 degrees less than the surrounding semiarid shrubland), severely limit losses from evaporation and transpiration, improving water economy at tree and ecosystem levels. Only small differences in water capture were recorded between small (<1 ha) and large (20-30 ha) patches, suggesting that all fragments are capable of similar fog water capture, but small patches have a less efficient water economy due to strong edge effects, increasing their fragility to drying trends. Fog interception showed no significant trend for the decadal period studied, which suggests that fog may compensate current declines in rainfall.
Background/Question/Methods Nitrogen (N) and Phosphorus (P) are major cellular components in consumer organisms and, limitations in their availability and accessibility can strongly affect growth and development, as well as life history strategies and population dynamics of consumer species. In environments where periodic disturbances induce formation of soil age gradients, biogeochemical shifts during soil development often are accompanied by individual and community modifications in primary producers, which in turn propagate these effects to consumer trophic levels. For example, as long-term soil development proceeds, changes in soil nutrient availability induce modifications in plant strategies to increase efficiency of nutrient (e.g. N and P) use and retention; which in turn affects herbivores and detritivores arthropods, that are under strong stoichiometric control, because, feed on low nutrient quality plant tissues and litter. Here we studied the effects of pronounced variability in primary producer nutrient content (i.e. leaf and litter) upon trophic structure and ecological stoichiometry (body C, N and P content) of arthropods and vertebrates during soil development in three c.20.000-years chronosequences in the Andean Dry Puna, Bolivia. We hypothesized that herbivores and arthropods in detritus-based food web experience major stoichiometric control across biogeochemical gradients during soil development because the chronic soil N-limitation in this Andean environment. Results/Conclusions Our results indicate that soil and plant N-limitation have a strong effect on nutrient body content and trophic structure of consumer species. C:N and N:P body contents in herbivores and detritivores species changed during soil development and were associated to increases in N-content of leaf and litter. Further, extreme lower N-contents in young soils were associated to lower arthropods species richness and simplified detritus-based food webs. Accordingly, biomass of herbivores and detritivores increased during soil development. Vertebrate predators abundance increased during late stages of development and this was positively related to increases in arthropods biomass. Significant differences in herbivores and detritivores diversity and biomass along soil age gradient indicate that soil and plant heterogeneity drives arthropods community structure and function, meanwhile biogeochemical gradients and N-limitation determined nutrient body content in both functional groups. These findings indicate that from individual to trophic structure chronic N-limitation is a critical driver of Andean food webs.
2014). Molecular phylogenetics of mouse opossums: new findings on the phylogeny of Thylamys (Didelphi-morphia, Didelphidae) — Zoologica Scripta, 43, 000–000. The mouse opossums of the genus Thylamys constitute a group of species mainly adapted to open xeric-like habitats and restricted to the southern portion of South America. We used molecular data (mitochondrial and nuclear sequences) to evaluate the phylogenetic and bio-geographical relationships of all currently known living species of the genus, recognizing a new taxon from the middle and high elevations of the Peruvian Andes and evaluating the phylogenetic structuring within T. pallidior and T. elegans, as well as the validity of T. sponso-rius, T. cinderella and T. tatei, and the haplogroups recognized within T. pusillus. Our results confirm the monophyly of the genus and that the Caatinga and the Cerrado inhabitants Thylamys karimii and T. velutinus are the most basal species in the radiation of Thylamys. We also calibrated a molecular clock which hypothesized a time of origin of the genus of about 24 My, with most species differentiating in middle and late Miocene and Plio-Pleisto-cene times of South America. Corresponding author: R. Horacio Zeballos, Centro de Investigaci on para la Promoci on de los Pueblos, Cooperativa V ıctor Andr es Bela unde I-8 Yanahuara, Arequipa, Per u.
The mouse opossums of the genus Thylamys constitute a group of species mainly adapted to open xeric-like habitats and restricted to the southern portion of South America. We used molecular data (mitochondrial and nuclear sequences) to evaluate the phylogenetic and biogeographical relationships of all currently known living species of the genus, recognizing a new taxon from the middle and high elevations of the Peruvian Andes and evaluating the phylogenetic structuring within T. pallidior and T. elegans, as well as the validity of T. sponsorius, T. cinderella and T. tatei, and the haplogroups recognized within T. pusillus. Our results confirm the monophyly of the genus and that the Caatinga and the Cerrado inhabitants Thylamys karimii and T. velutinus are the most basal species in the radiation of Thylamys. We also calibrated a molecular clock which hypothesized a time of origin of the genus of about 24 My, with most species differentiating in middle and late Miocene and Plio-Pleistocene times of South America.
Background/Question/Methods What factors drive the observed changes in the number of coexisting species across different spatial and temporal scales? This is a fundamental, albeit vexing, question in ecology. Most answers to this question emphasize the role of abiotic factors (e.g., area, temperature, energy) as drivers of diversity patterns. However, empirical and theoretical evidence suggest that biodiversity; biotic factors such as species interactions or biological heterogeneity, could regulate diversity itself within and across communities. This regulation can be either direct, through species interactions, or indirect due to modulation of abiotic factors by the organisms. Here we perform a meta-analysis to test the hypothesis that biodiversity drives diversity patterns by: (1) quantifying the relative importance of abiotic vs. biotic drivers on species diversity patterns and (2) quantifying how the relative importance of these drivers varies across scales, organismal type and ecosystems. To address these objectives we first identified all proposed biotic and abiotic drivers and hypotheses reported in the literature to account for patterns in diversity. We used these as a template to classify a set of 307 papers compiled by Field et al (2009) and then created the dataset used in the meta analyses. Results/Conclusions Initial results from our meta-analysis indicate that both abiotic and biotic drivers may positively influence diversity, but the effect size of biotic drivers is significantly larger. Our results show that this difference is the result of biotic drivers having a larger and significant effect in animal consumers than in producers, in continental than in island settings, in terrestrial than in freshwater or marine ecosystems, at large spatial extents ranging from 100-1000 km2, and in the context of hypotheses dealing with historical processes. Although the biotic factors analyzed in our study do not capture all possible aspects of biodiversity, we offer strong evidence in support of the hypothesis that biodiversity is a strong driver of diversity. Noteworthy, biotic factors appeared to be stronger than abiotic ones, especially in terrestrial environments and for consumer organisms at large spatial scales. We discuss the mechanisms behind these patterns
An active Trypanosoma cruzi transmission cycle maintained by wild rodents in the Andean valleys of Cochabamba Bolivia is described. Wild and domestic Triatoma infestans with 60% infection with T. cruzi were found and was evidenced in 47.5% (rodents) and 26.7% (marsupial) by parasitological and/or serologycal methods. Phyllotis ocilae and the marsupial species Thylamys elegans, are the most important reservoirs followed by Bolomys lactens and Akodon boliviensis. In spite of both genotypes (TCI and TCII) being prevalent in Bolivia, in our study area only T. cruzi I is being transmitted. Our data suggest that wild T. infestans and wild small mammals play an important role in the maintenance of the transmission cycle of T. cruzi. Furthermore, the finding of high prevalence of T. cruzi infection in wild T. infestans point to the risk of the dispersion of Chagas' disease.
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