Examinando por Autor "Harrod, Chris"

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    Diet of Andean Leaf-Eared Mice (Phyllotis) Living atExtreme Elevations on Atacama Volcanoes: Insights FromMetagenomics, DNA Metabarcoding, and Stable Isotopes
    (WILEY, 2024) Quezada Romegialli, Claudio; Quiroga Carmona, Marcial; D'Elía, Guillermo; Harrod, Chris ; Storz, Jay F.
    On the flanks of > 6000 m Andean volcanoes that tower over the Atacama Desert, leaf-eared mice (Phyllotis vaccarum) live at extreme elevations that surpass known vegetation limits. The diet of these mice in these barren, hyperarid environments has been the subject of much speculation. According to the arthropod fallout hypothesis, sustenance is provided by windblown in-sects that accumulate in snowdrifts (“aolian deposits”). Mice may also feed on saxicolous lichen or forms of cryptic vegetation that have yet to be discovered at such high elevations. We tested hypotheses about the diet of mice living at extreme elevations on Atacama volcanoes by combining metagenomic and DNA metabarcoding analyses of gut contents with stable isotope analyses of mouse tissues. Genomic analyses of contents of the gastrointestinal tract of a live-captured mouse from the summit of VolcánLlullaillaco (6739 m) revealed an opportunistic but purely herbivorous diet, including lichens. Although we found no evidence of animal DNA in gut contents of the summit mouse, stable isotope data indicate that mice from elevations at or near vegetation limits (~5100 m) include a larger fraction of animal prey in their diet than mice from lower elevations. Some plant species detected in the gut contents of the summit mouse are known to exist at lower elevations at the base of the volcano and in the surrounding Altiplano, suggesting that they may occur at higher elevations beneath the snowpack or in other cryptic microhabitats.
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    Differences in the adulteration degree and antimicrobial activity of chilean ulmo honey versus multifloral honey revealed by stable isotope analysis
    (ELSEVIER, 2024) Pérez, Pablo; Lavín, Paris; Harrod, Chris; Echeveste, Pedro
    Honey, valued for its nutritional and antimicrobial benefits, has experienced an increased production in recent decades. However, this rise has been accompanied by concerns of adulteration, often involving the fraudulent addition of sugars. Our study sought to compare the physicochemical and isotopic properties of various honeys available to Chilean consumers, assessing the extent of adulteration. Samples included honey produced from bees that fed on multiple flowers and those fed by ulmo flowers – an endemic species of South America that produces a high-quality, high-cost honey – and analyzed for antimicrobial activity against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The analysis of ash content (%), moisture (%), pH and total phenolic content (mg GAE/100 g honey) found little obvious differences among honeys regardless of the feeding flowers (multifloral vs ulmo), type of purchase market (formal vs informal) or origin of the honeys (Central vs Southern Chile). However, the use of stable isotope analysis (δ 13 C and δ 15 N) of honey provided a powerful means to identify the degree of adulteration prior to the point of sale. Multifloral honeys purchased at informal markets were all adulterated, and ulmo honeys included both the least and most adulterated honeys. Regarding their antimicrobial activity, most multifloral honeys were less effective than ulmo honeys. Notably, while multifloral honey activity was independent of adulteration, the antimicrobial activity of ulmo honey was negatively affected by adulteration.
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    Identifying knowledge gaps in hypersaline systems supporting the global electrical transition: invertebrate community structure in salars from the lithium triangle
    (PeerJ Inc., 2025) Salazar, Gonzalo; Aguilar, Pablo; Harrod, Chris
    Following decades of mining impacts, South America’s hypersaline wetlands (salars)face increasing threats from lithium extraction to support global decarbonisation.Although globally important, salars are understudied and information needed tounderstand environmental impacts is lacking. Modern ecological studies on salarshave focused on microbial community composition and function but other taxa areless studied, including resident and migratory reptiles and birds and their aquaticinvertebrate prey.Given the scale and immediate nature of the threats associated with lithiumexploitation, we must deepen our understanding of salar biology, but this is impededby logistic/financial restrictions given the heightened costs of sampling in these oftenremote, extreme environments. Given the pressing demand for information, wecollated/analysed information from the literature. We generated lists of invertebratetaxa present in 63 hypersaline environments from Argentina, Bolivia, Chile andPeru, and examined relationships between invertebrate community structure andphysicochemical factors. We recorded 46 different taxa, with the Centropagidae beingthe most frequently recorded taxon across systems. Multivariate analyses of communitystructure showed significant clustering among sites. Variation in community structurewas best explained by maximum salinity (18%). Geographical location or ecosystemsize had no obvious effect on community structure. We provide a useful broad view ofaquatic invertebrate diversity in the hypersaline salars but highlight the general lack ofinformation regarding the ecology of these ecosystems
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    Unexpected trophic diversity in the endemic fish Orestias chungarensis in a high-altitude freshwater ecosystem, Lake Chungará (4520 m), northern Chile
    (Wiley, 2025) Gonzalez, Karina; Gomez-Uchida, Daniel; Harrod, Chris
    Orestias chungarensis Vila & Pinto, 1986 is a small-bodied (max forklength = 120 mm) cyprinodontiform fish with a very restricted global distribution.The species is limited to a single, small (283 km2 ), high-altitude (4520 m) catchmentlocated in the Altiplano of northern Chile. Until the late 20th century, O. chungarensiswas the only fish species inhabiting both Lake Chungará and its main afferent river,the River Chungará. The introduction of rainbow trout [Oncorhynchus mykiss(Walbaum, 1792)] at this time raised concerns for the long-term conservation of Ores-tias. By 2017, O. chungarensis were no longer present in the River Chungará butremain relatively numerous in Lake Chungará. Although O. chungarensis are of ele-vated conservation concern, little is known regarding their ecology, and the few stud-ies conducted have relied on individuals captured from shallow littoral habitats. Here,we captured O. chungarensis from different lake habitats and analysed multi-tissuestable isotopes (δ13C, δ15 N, δ34 S) and stomach contents to characterise their trophicecology. We also used geometric morphometrics to analyse any putative habitat-associated variation in body shape. O. chungarensis showed very wide variation intheir stable isotope values (range: δ13 C = _x0001_15.1 to _x0001_8.0‰; δ15 N = 8.9–14.1‰;δ34S = _x0001_10.5–1.7‰). A k-means cluster analysis indicated that individuals could bebest classified into two groups in stable isotope space. A discriminant function analy-sis supported the separation of the sampled population into two groups (jack-knifedclassification success = 98%). Individuals belonging to either a putative littoral group(13 C-enriched, 15 N-depleted and 34 S-depleted) or a group associated with pelagic-derived materials (13 C-depleted, 15N-enriched, 34 S-enriched), which likely fed offshore or in deeper waters. Stomach contents results showed that O. chungarensisfrom the two putative groups had consumed similar prey prior to capture, feedingmainly on benthic macroinvertebrates (amphipods, chironomid larvae and pupae andgastropods). Mixing models analysis showed a broadly similar diet between groups,but the scale of contribution to the assimilated diet differed between groups. Com-parisons of stable isotope niche size and overlap showed limited niche overlap, pro-viding more evidence for differential foraging patterns. The dichotomy between theresults from stable isotope and stomach content analysis suggests thatO. chungarensis individuals forage on taxonomically similar diets, but their prey arefuelled from materials derived from different lake habitats (littoral and open-water).Given the remarkable plasticity found in the genus, our results could reflect the exis-tence of a previously unrecognised ecotype.
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    Why aquatic scientists should use sulfur stable isotope ratios (ẟ34S) more often
    (ELSEVIER, 2024) Raoult, Vincent; Phillips, Alexandra A.; Nelson, James; Niella, Yuri; Skinner, Christina; Bell Tilcock, Miranda; Burke, Patrick J.; Szpak, Paul; James, W. Ryan; Harrod, Chris
    Over the last few decades, measurements of light stable isotope ratios have been increasingly used to answer questions across physiology, biology, ecology, and archaeology. The vast majority analyse carbon (δ13C) and nitrogen (δ15N) stable isotopes as the ‘default’ isotopes, omitting sulfur (δ34S) due to time, cost, or perceived lack of benefits and instrumentation capabilities. Using just carbon and nitrogen isotopic ratios can produce results that are inconclusive, uncertain, or in the worst cases, even misleading, especially for scientists that are new to the use and interpretation of stable isotope data. Using sulfur isotope values more regularly has the potential to mitigate these issues, especially given recent advancements that have lowered measurement barriers. Here we provide a review documenting case studies with real-world data, re-analysing different biological topics (i.e. niche, physiology, diet, movement and bioarchaeology) with and without sulfur isotopes to highlight the various strengths of this stable isotope for various applications. We also include a preliminary meta-analysis of the trophic discrimination factor (TDF) for sulfur isotopes, which suggest small (mean 0.4 ± 1.7 ‰ SD) but taxa- dependent mean trophic discrimination. Each case study demonstrates how the exclusion of sulfur comes at the detriment of the results, often leading to very different outputs, or missing valuable discoveries entirely. Given that studies relying on carbon and nitrogen stable isotopes currently underpin most of our understanding of various ecological processes, this has concerning implications. Collectively, these examples strongly suggest that researchers planning to use carbon and nitrogen stable isotopes for their research should incorporate sulfur where possible, and that the new ‘default’ isotope systems for aquatic science should now be carbon, nitrogen, and sulfur.