Chironomid-climate continentality conundrum

PLOS One | https://doi.org/10.1371/journal.pone.0327780 August 5, 2025 9 / 18 Table 2. Results of the redundancy analysis (RDA) of the dataset and tested environmental and climatic variables in the dataset: lake-water depth (m); longitude; lake-water pH; bedrock type; July (Jul T), October (Oct T), and April (Apr T) mean air temperatures (°C); lake ice-cover (days); growing degree days with base temperature of 5°C (GDD5); Kerner Oceanity Index (KOI); and annual temperature range (ATR). The proportion of chironomid-assemblage variation explained by each variable, p-values, and λ1:λ2 ratios are given. Variable % of variation explained p-value λ1:λ2 Longitude 13.1 0.001 0.8 Environment Bedrock 16.8 0.001 1.1 pH 12.3 0.001 1 Soil base saturation 8 0.002 0.5 Soil clay content 10 0.001 0.7 Soil sand content 4.7 0.013 0.2 LOI (Russian and Latvian samples) – 0.6 – Depth (m) 8.3 0.001 0.5 Climate GDD5 17.2 0.001 1.5 Oct T 14.2 0.001 1.2 Apr T 4 0.045 0.2 Jul T 17.4 0.001 1.3 Jan T 8 0.021 0.5 Ice-cover 15.5 0.001 1.1 ATR 15 0.001 1.3 KOI 18.4 0.001 1.6 https://doi.org/10.1371/journal.pone.0327780.t002 Fig 4. Redundancy analysis (RDA) plot showing the climate and environmental variables, revealed the significant dependency in the dataset: lake-water depth (m); longitude; lake water pH; bedrock type; soil base saturation (soil BS); soil clay content (soil clay); soil sand content (soil sand); July (Jul T), January (Jan T), October (Oct T), and April (Apr T) mean air temperatures (°C); lake-ice cover (days); growing degree days

with base temperature of 5°C (GDD5); Kerner Oceanity Index (KOI); and annual temperature range (ATR). Variables explain 44.6% of variation in total with a p-value of 0.001. Continental sites (orange) correspond to −10–0 KOI, transitional sites (green) to 0–10 KOI, and oceanic sites (blue) to 10–20 KOI. https://doi.org/10.1371/journal.pone.0327780.g004