Extinction debt of species and ecological interactions in a fragmented landscape

Addressing the worldwide biodiversity crisis in fragmented landscapes requires considering both immediate and delayed extinctions-the extinction debt. This debt arises from the gradual loss of species following habitat fragmentation. Additionally, species interactions may also experience an extinction debt, affecting ecosystem structure and function. However, the extinction debt for species interactions has received little attention. We studied the lasting effects of habitat fragmentation on plants, herbivore insects of four trophic guilds, parasitoids and their trophic interactions in a dryland landscape in central-western Argentina. Assuming a paid debt in long-fragmented habitats, we examined the potentially unpaid debt in recently fragmented habitats as the difference between the current richness of species and interactions and their expected richness based on area and connectivity from long-fragmented habitats. We found a higher extinction debt for herbivores and plant-herbivore interactions in small, isolated habitats and a lower extinction debt for plants only in small habitats. By contrast, the extinction debt of parasitoids was higher in large, well-connected habitats, while there was no extinction debt detected for herbivore-parasitoid interactions. Understanding the magnitude of extinction debts for species and interactions offers guidance for mitigating future extinctions of species and interactions to curb the degradation of ecosystems and preserve their long-term function.