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1. Arctic chironomid training set from Canada, Greenland, Iceland and Svalbard for estimating paleotemperatures (2022)

   https://doi.org/10.18739/A27H1DN9Q  

   Medeiros, Andrew; Axford, Yarrow; Chipman, Melissa; Francis, Donna; Hamerlik, Ladislav; Langdon, Peter; Schellinger, Grace; Puleo, Peter; Steigleder, Regan; Walker, Ian; et al (January 2022, NSF Arctic Data Center)

   This dataset includes chironomid species assemblage data and air temperature estimates from 400+ lakes across northern North America, Greenland, Iceland, and Svalbard to inform interpretations of Holocene subfossil chironomid assemblages used in paleolimnological reconstruction. This calibration-set was developed by re-identifying and taxonomically harmonizing chironomids in previously described surface sediment samples, with identifications made at finer taxonomic resolution than in original publications (which are cited in the publication describing this dataset, Medeiros et al. 2022 Quaternary Science Reviews, and should be cited by dataset users). Site summer air temperatures are newly estimated with a consistent method using the WorldClim 2.1 gridded bioclimatic dataset. The large geographic coverage of this dataset is intended to provide climatic analogs for a wide range of Holocene climates in the northwest North Atlantic region and North American Arctic, including Greenland. For many of these regions, modern calibration data for paleoclimate proxies are sparse despite keen interest in paleoclimate reconstructions from high latitudes. Dataset users should consult and cite the following source publication: Medeiros, A.S., Chipman, M., Francis, D.R., Hamerlik, L., Langdon, P., Puleo, P.J.K., Schellinger, G., Steigleder, R., Walker, I.R., Woodroffe, S., and Axford, Y. 2022. A continent-scale chironomid training set for reconstructing arctic temperatures. Quaternary Science Reviews 294, 107728. DOI 10.1016/j.quascirev.2022.107728. 

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2. Shared Features Underlying Compact Genomes and Extreme Habitat Use in Chironomid Midges

   https://doi.org/10.1093/gbe/evae086  

   Nell, Lucas A; Weng, Yi-Ming; Phillips, Joseph S; Botsch, Jamieson C; Book, K Riley; Einarsson, Árni; Ives, Anthony R; Schoville, Sean D (May 2024, Genome Biology and Evolution)

   Vieira, Cristina (Ed.)

   Abstract Nonbiting midges (family Chironomidae) are found throughout the world in a diverse array of aquatic and terrestrial habitats, can often tolerate harsh conditions such as hypoxia or desiccation, and have consistently compact genomes. Yet we know little about the shared molecular basis for these attributes and how they have evolved across the family. Here, we address these questions by first creating high-quality, annotated reference assemblies for Tanytarsus gracilentus (subfamily Chironominae, tribe Tanytarsini) and Parochlus steinenii (subfamily Podonominae). Using these and other publicly available assemblies, we created a time-calibrated phylogenomic tree for family Chironomidae with outgroups from order Diptera. We used this phylogeny to test for features associated with compact genomes, as well as examining patterns of gene family evolution and positive selection that may underlie chironomid habitat tolerances. Our results suggest that compact genomes evolved in the common ancestor of Chironomidae and Ceratopogonidae and that this occurred mainly through reductions in noncoding regions (introns, intergenic sequences, and repeat elements). Significantly expanded gene families in Chironomidae included biological processes that may relate to tolerance of stressful environments, such as temperature homeostasis, carbohydrate transport, melanization defense response, and trehalose transport. We identified several positively selected genes in Chironomidae, notably sulfonylurea receptor, CREB-binding protein, and protein kinase D. Our results improve our understanding of the evolution of small genomes and extreme habitat use in this widely distributed group. 

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3. Using a Paired Chironomid δ ¹⁸ O and Aquatic Leaf Wax δ ² H Approach to Reconstruct Seasonality on Western Greenland During the Holocene

   https://doi.org/10.1029/2020PA004169  

   Corcoran, Megan_C; Thomas, Elizabeth_K; Morrill, Carrie (April 2021, Paleoceanography and Paleoclimatology)

   Abstract The Arctic hydrological cycle is predicted to intensify as the Arctic warms, due to increased poleward moisture transport during summer and increased evaporation from seas once ice‐covered during winter. Records of past Arctic precipitation seasonality are important because they provide a context for these ongoing changes. In some Arctic lakes, stable isotopes of oxygen and hydrogen (δ¹⁸O and δ²H, respectively) vary seasonally, due to seasonal changes in precipitation δ¹⁸O and δ²H. We reconstruct precipitation seasonality from Lake N3, a well‐dated lake sediment archive in Disko Bugt, western Greenland, by generating Holocene records of two proxies that are produced at different times of the year, and therefore record different lake water seasonal isotopic compositions. Aquatic plants synthesize waxes throughout the summer, and their δ²H reflects winter‐biased precipitation δ²H at Lake N3, whereas chironomids synthesize their head capsules between late summer and winter, and their δ¹⁸O reflects summer‐biased precipitation δ¹⁸O at Lake N3. During the middle Holocene at Lake N3, aquatic plant leaf wax was strongly²H‐depleted, while chironomid chitin was¹⁸O‐enriched. We guide interpretations of these records using sensitivity tests of a lake water and energy balance model, where we change precipitation amount and isotope seasonality inputs. The sensitivity tests suggest that the contrasting trends between proxies were likely caused by an increase in precipitation amount during all seasons and an increase in precipitation isotope seasonality, in addition to proxy‐specific mechanisms, highlighting the importance of understanding lake‐ and proxy‐specific systematics when interpreting records from sediment archives. 

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4. NOAA/WDS Paleoclimatology - South Greenland Chironomid, Moss, and Cellulose Oxygen Isotope Data during the Younger Dryas and Early Holocene

   https://doi.org/10.25921/bdkp-mv47  

   Puleo, P.; Masterson, A.L.; Medeiros, A.; Schellinger, G.C.; Steigleder, R.; Woodroffe, S.; Osburn, M.R.; Axford, Y. (January 2022, NOAA National Centers for Environmental Information)

   This archived Paleoclimatology Study is available from the NOAA National Centers for Environmental Information (NCEI), under the World Data Service (WDS) for Paleoclimatology. The associated NCEI study type is Lake. The data include parameters of climate reconstructions|paleolimnology with a geographic location of Greenland. The time period coverage is from 13936 to -36 in calendar years before present (BP). See metadata information for parameter and study location details. Please cite this study when using the data. 

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5. Revisiting talus and free-air temperatures after 50 years of change at an American pika (Ochotona princeps) study site in the Southern Rockies

   https://doi.org/10.1371/journal.pclm.0000049  

   Monk, Emily M.; Ray, Chris (July 2022, PLOS Climate)

   Sharma, Lalit Kumar (Ed.)

   Climate change in mountain regions has exposed high-elevation species to rapidly changing temperatures. Although climate exposure can be reduced in certain microclimates, the quality of microclimatic refugia might also degrade with climate change. The American pika ( Ochotona princeps ) often inhabits high elevations, and is considered climate-sensitive due to its narrow thermal tolerance and recent extirpations in some warmer portions of its range. Pikas behaviorally thermoregulate by taking refuge in the subsurface microclimates found in taluses and other rocky habitats, where daily thermal fluctuations are attenuated and somewhat decoupled from free-air temperatures. Changes in microclimate might reduce the efficacy of this behavioral thermoregulation. This study compares recent (2009–2021) subsurface temperatures at a long-term pika study site with a rare instance of historical (1963–1964) data from the same location. We also place historical and recent microclimates in context using long-term data on free-air temperatures from the same area. Recent free-air temperatures were often warmer than historical records, and subsurface temperatures exhibited even stronger warming between periods. Temperatures measured in the talus were often dramatically warmer in recent records, especially at the deeper of two subsurface sensor placements in this study. Winter months showed the greatest changes in both talus and free-air temperatures. Differences between historical and recent microclimates were not explained by the precise placement of sensors, as recent temperatures were similar across a wide variety of subsurface placements, and temporal changes in free-air temperatures at the historical study site were also reflected in data from nearby weather stations. Together, these results suggest that subsurface microclimates important for pika thermoregulation have changed over the past few decades, perhaps even faster than observed changes in free-air temperatures. The generality of these results and their potential ramifications for ecosystem processes and services should be explored. 

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