Beyond Temperature: Surface-Physical Drivers Differentiate Halobates Distributions — A SHAP-Based Analysis

Sea skaters of the genus Halobates (Heteroptera: Gerridae) are the only insects known to inhabit the open ocean, yet the relative importance of the environmental factors shaping their distributions remains poorly resolved. Prior work has emphasized sea-surface temperature as the primary constraint, but temperature, salinity, productivity, and ocean dynamics are tightly coupled in the ocean, and conventional importance metrics struggle to disentangle their contributions under collinearity. Here we apply SHAP (SHapley Additive exPlanations) analysis — combined with pairwise permutation testing and false discovery rate (FDR) correction — to quantify and compare the environmental drivers of distribution in three Halobates species: the widespread oceanic H. micans, the range-restricted H. sobrinus, and the coastal/neritic H. sericeus. Using spatially thinned occurrence records and eleven environmental predictors organized into physiological, physical habitat, and trophic tiers, we built species-specific Maxent models and decomposed their predictions into mean absolute and mean signed SHAP values. Contrary to the temperature-first emphasis of the prior literature, temperature, chlorophyll-a, and dissolved oxygen showed no significant pairwise differences between species in their net directional effects. Instead, only wind speed, annual variance in sea-surface salinity, and sea-surface height differed significantly between species after the FDR correction.