Data from: 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 worker behavior, and we recorded proportions of seeds dispersed
after 60 minutes and 24 hours. KEY RESULTS: Field observations yielded
some significant within-pair differences. Ants dispersed more seeds of
widespread species for all pairs, although dispersal distances did not
differ. In laboratory experiments, after 24 hours, ants dispersed more
seeds of widespread species into nests. CONCLUSIONS: Endemic Trillium
species exhibited lower overall SDE than their widespread congeners. These
findings add to the list of ecological and demographic challenges that
face endemic plants when compared to common congeners. Lower SDE may
negatively impact reproductive rates and the colonization of new habitats,
which may contribute to patterns of endemism. If you would like your
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