Hornbills as drivers of plant range shifts under climate change

Abstract

Range shifts of plants under climate change depend on frugivore-mediated seed dispersal. However, the role of frugivores in facilitating these shifts remains uncertain. This study assessed how plant-hornbill functional connectivity varied across latitude and elevation in South Asia by integrating species distribution models under present and future climate change scenarios with connectivity analysis under conservative (single-generation) and optimistic (multi-generational) seed dispersal scenarios. The connectivity patterns were synthesised using generalised additive models and indicated that latitude explained significantly more variation in connectivity than elevation. The range shifts of plants were primarily constrained by dispersal limitation rather than by the availability of suitable future habitat. Under conservative dispersal, connectivity remained stagnant despite climate change whereas optimistic dispersal fundamentally reshaped connectivity patterns, creating new pathways that aligned with areas of habitat gain. These findings demonstrate that the capacity of tropical plants to track climate change is critically dependent on hornbills, highlighting the urgent need to conserve both frugivore populations and landscape connectivity to ensure ecosystem resilience.