Format: ORAL

Yuanshu Pu1,2, Alexander Zizka4, Renske E. Onstein2,3

1 Univeristy of Leipzig, Leipzig, DE (yuanshu.pu@evobio.eu) 2 German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, DE 3 Naturalis Biodiversity Center, Leiden, NL 4 Philipps-University Marburg, Marburg, DE

Madagascars biodiversity faces various threats leading to defaunation and biodiversity loss. However, how defaunation affects biotic interactions and hence ecosystem functions, such as seed dispersal of fleshy fruited plants by vertebrate (frugivory), remains unclear. We used structural equation modelling to test whether the loss of trait matching between fruit-eating and seed dispersing animals (frugivores) and fleshy-fruited vertebrate-dispersed plants (i.e., dysfunctional seed dispersal) has led to high plant extinction risk, and whether protected areas in Madagascar conserve seed dispersal interactions. We integrated distribution data, dispersal traits, and IUCN Red List status of 2,852 vertebrate-dispersed plant species and 129 frugivore species in 649 communities across Madagascar. We detected a loss of seed size to body size trait matching in non-protected areas, suggesting that many large-seeded plants do not co-occur with frugivores that are able to swallow and effectively disperse the seeds. Interestingly, such dysfunctional communities also showed the largest proportion of threatened plants, but only when they were depleted of all large-bodied frugivorous lemurs, with birds or bats left as the largest seed dispersers. We also found that protected areas conserve lemur-dominated communities with the highest proportion of threatened plants, but not the highest seed dispersal dysfunctionality. In these communities higher dysfunctionality did not lead to higher threat. This suggests that increased plant extinction risk is linked to defaunation as well as other stressors. Our results highlight the importance of biotic interactions for ecosystem functioning and plant extinction risk in Madagascar, emphasizing how timely monitoring ecosystem functioning of degraded ecosystems may help conserve biodiversity.