Examinando por Autor "Gomez-Uchida, Daniel"

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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.