Overall seed dispersal effectiveness is lower in endemic Trillium species than in their widespread congeners

PREMISE OF THE STUDY: Comparing ecological attributes of endemic species with related, widespread species can reveal differences accounting for rarity. Forests of the southeastern US are home to many range-restricted endemic and widespread species of Trillium, a genus of ant-dispersed herbs. Evidence suggests that aspects of seed-related life history stages are often correlated with plant rarity, but few studies have tested whether the process of seed dispersal differs for endemic and widespread species. To address this question, we compare aspects of seed dispersal effectiveness (SDE) for three sympatric widespread-endemic Trillium species pairs. METHODS: We observed ant seed dispersal for Trillium species pairs at eight sites, recorded numbers of seeds dispersed and dispersal distances, and described disperser interactions. To test disperser preference, we presented seeds of each pair to captive colonies of Aphaenogaster picea, a keystone disperser. Seeds were assigned scores based on...