Climate versus weather extremes: Temporal predictor resolution matters for future rather than current regional species distribution models

Aim: Climate is considered a major driver of species distributions. Long-term climatic means are commonly used as predictors in correlative species distribution models (SDMs). However, this coarse temporal resolution does not reflect local conditions that populations experience, such as short-term weather extremes, which may have a strong impact on population dynamics and local distributions. We here compare the performance of climate- and weather-based predictors in regional SDMs and their influence on future predictions, which are increasingly used in conservation planning. Location: South-western Germany. Methods: We built different SDMs for 20 Orthoptera species based on three predictor sets at a regional scale for current and future climate scenarios. We calculated standard bioclimatic variables and yearly and seasonal sets of climate change indicating variables of weather extremes. As the impact of extreme events may be stronger for habitat specialists than for generalists, we distinguished species' degrees of specialization. We computed linear mixed-effects models to identify significant effects of algorithm, predictor set and specialization on model performance and calculated correlations and geographical niche overlap between spatial predictions. Results: Current predictions were rather similar among all predictor sets, but highly variable for future climate scenarios. Bioclimatic and seasonal weather predictors performed slightly better than yearly weather predictors, though performance differences were minor. We found no evidence that specialists are more sensitive to weather extremes than generalists. Main conclusions: For future projections of species distributions, SDM predictor selection should not solely be based on current performances and predictions. As long-term climate and short-term weather predictors represent different environmental drivers of a species' distribution, we argue to interpret diverging future projections as complements. Even if similar current performances and predictions might imply their equivalency, favouring one predictor set neglects important aspects of future distributions and might mislead conservation decisions based on them.