Data for: Legacy of the lost and pressure of the present: Malagasy plant seeds retain megafauna dispersal signatures but downsize under human pressure

Ongoing declines of large-bodied frugivores limit the dispersal of
large-seeded plants, contributing to their (local) demise and ‘downsizing’
of seeds across assemblages. However, the extent to which human pressure
leads to contemporary seed downsizing, and whether extinct megafrugivores
have left imprints on seed size, remains unclear. Here, we integrate trait
and distribution data for 2,852 endozoochorous plant species, 48 extant
and 15 extinct frugivore species across 361 assemblages on Madagascar.
Using structural equation models, we show that assemblages with a higher
human footprint, a cumulative index of human pressure, have smaller
maximum seed sizes, especially through downsizing of extant frugivores.
Furthermore, among assemblages with ‘mega-seeded’ plants (i.e., seeds that
cannot be swallowed by any extant Malagasy frugivore), larger seed sizes
are associated with larger past megafrugivores, reflecting the legacy of
past interactions.  Human-driven seed downsizing highlights
broader implications in the erosion of important ecosystem functions such
as forest carbon storage.