Temporal niche influences higher extinction risk among diurnal tetrapods from tropical regions

Anthropocene extinctions of biodiversity vary dramatically through geographic and phylogenetic space, with certain regions and lineages concentrating high defaunation rates, while others remain nearly unchanged.This heterogeneity in biodiversity erosion results from (spatial and phylogenetic) variation in the interactions between species fitness-relevant traits and environmental threats that trigger extinctions. Evidence reveals that factors including life histories, ecophysiology, and resource-use generalism influence variation in species declines under rapidly changing environments. An emerging hypothesis predicts that species spread across different ‘locations’ of the 24h diel spectrum are exposed to different anthropogenic pressures on demographic stability (e.g. daytime contact with humans), which can trigger differential extinction risk among diurnal, nocturnal and cathemeral (day-night active) species. However, this hypothesis remains largely neglected. Only a single large-scale test exists, which documented higher declines among diurnal mammals. Here, we address this hypothesis across tetrapods globally, spanning >23,000 species across both endotherms and ectotherms for the first time. Our results reveal that cathemerality is significantly associated with a lower probability of undergoing population declines across tetrapods (except birds), while diurnality is associated with higher extinction risk category in amphibians. Collectively, our results suggest that the role of temporal niche in extinction is significant but variable across tetrapods.