Current northernmost distribution of the Andean bear (Tremarctos ornatus) is not defined precisely; mentioned to be located "at the Serranía del Perijá" without accurate/confirmed distribution records, and placed by the IUCN at the Serranía de Portuguesa (Venezuela). There is an information gap on the fragmentation of the Andean bear associated ecosystems (Andean forest and Paramo) throughout its distribution in Colombia and Venezuela. The aim of this study is to provide precise knowledge on the current northernmost distribution of the Andean bear in South America at the Serranía del Perijá, besides quantifying spatial trends of the fragmentation of its associated ecosystems at the eastern and western slopes. Confirmed distribution records were obtained from field surveys (2009 to 2016), literature, scientific collections and biodiversity databases. The fragmentation degree of Andean bear associated ecosystems was characterized using FRAGSTATS (V 4.2) software with satellite images from 2008. A current population block with at least three sectors of incidence is present along both slopes of the Serranía del Perijá. Although the Colombian slope comprises greater raw area of Andean bear associated ecosystems, it is highly fragmented and isolated. Core area analysis (extracting a disturbance buffer of 1,000 m into the border of each patch) exhibits a Venezuelan slope maintaining greater amount of Andean bear associated ecosystems at few, large and less fragmented patches. This study extends the distribution of the species 180 km until the north of the Serranía del Perijá (regarding the current distribution recognized by the IUCN) and provides the northernmost confirmed distribution records for South America: Barrancas (Colombia) and Mara (Venezuela) municipalities. This study provides the first finescale information on Andean bear associated ecosystems fragmentation for Colombia and Venezuela, with traceable landscape measurements permitting future long-term comparative analyses. A high fragmentation degree of the Andean bear associated ecosystems is present at the Colombian slope of the Serranía del Perijá due to extensive legal and illegal agricultural activities and wood extraction. The lack of information about the Andean bear distribution and its associated ecosystems fragmentation could be putting the survival of local populations at risk, while a clear knowledge on these issues could generate planned conservation actions by the governmental environmental authorities.La distribución más septentrional actual del oso andino (Tremarctos ornatus) no está definida con precisión; generalmente se le localiza "en la Serranía del Perijá" sin registros precisos/confirmados, y la UICN la ubica en la Serranía de Portuguesa (Venezuela). Existe un vacío de información de la fragmentación de los ecosistemas asociados al oso andino (bosque Andino y Páramo) en Colombia y Venezuela. El objetivo de este estudio es brindar conocimiento preciso sobre la distribución más septentrional del oso andino en Suramérica en la Serranía del...

Temperatures have increased around the globe, affecting many ecosystems, including high-elevation Andean streams where important aquatic insect species coexist. Depending on the magnitude of change, warming could lead to the mortality of sensitive species, and those tolerant to rising water temperatures may exhibit differences in growth rates and development. Taxon-specific optimal temperature ranges for growth determine how high or low temperatures alter an organism’s body size. In this study, we observed the effects of different climate change scenarios (following three scenarios of the 2021 IPCC predictions) in two aquatic insect species distributed in high-elevation streams in Ecuador: the mayfly Andesiops peruvianus (Ephemeroptera: Baetidae) and the caddisfly Anomalocosmoecus illiesi (Trichoptera: Limnephilidae). We assessed how increased water temperatures affect larval growth rates and mortality during a 10-day microcosm experiment. Our results showed that Andesiops peruvianus was more thermally sensitive than Anomalocosmoecus illiesi. Mortality was higher (more than 50% of the individuals) in mayflies than in caddisflies, which presented mortality below 12% at +2.5°C and +5°C. Mortality in mayflies was related to lower dissolved oxygen levels in increased temperature chambers. Higher temperatures affected body size and dry mass with a faster growth rate of Andesiops peruvianus larvae at experimentally higher temperatures, suggesting an important response of this hemimetabolous species to stream temperatures. For Anomalocosmoecus illiesi, we did not find significant changes in mortality, body size or growth rate in response to temperature changes during our experiment. In situ outcomes of species survival and growth in Andean streams are difficult to predict. Nevertheless, our results suggest that at only +2.5°C, a water temperature increase affected the two insect taxa differentially, leading to a drastic outcome for one species’ larvae while selecting for a more tolerant species. Our study suggests that climate change might produce significant mortality and growth rate effects on ectotherm tropical aquatic insects, especially Andean mayflies, which showed higher sensitivity to increased water temperature scenarios.