Chironomid-climate continentality conundrum

PLOS One | https://doi.org/10.1371/journal.pone.0327780 August 5, 2025 4 / 18 Site selection The following sets of sites (Table 1) were used to compile the training set: (1) six oceanic sites from Norway (part of the Swiss-Norwegian training set collected in 1995–1999 by Heiri et al. [39]; the data were downloaded from the National Centre of Environmental Information online storage); (2) seven intermediate continentality sites from Latvia (part of the Finno-Baltic-Polish training set collected in 2019–2021 by Bakumenko et al. [42]); (3) thirty-one intermediate to continental sites from western Russia collected for this study in 2021; (4) nine oceanic to intermediate continentality sites from Sweden (Huser, unpublished) collected in 2014 were added to fill the biogeographical gap between the Norwegian and Latvian-Russian parts of the dataset (Fig 1). Fig 1. Map of sampled lakes with respect to mean July air temperature (MJAT; °C), ice-cover duration (days), annual temperature range (ATR; °C), and Kerner Oceanity Index (KOI; continental area (orange) is KOI −10 - 0, transitional (green) is KOI = 0–10, and oceanic (blue) is KOI 10-20). https://doi.org/10.1371/journal.pone.0327780.g001