Berry Batesian mimicry enables bird dispersal of asexual bulbils in a yam

Abstract

Many plants that abandon sex rely on clonal propagules, but their short dispersal distances can trap offspring near parent plants and enemies. We show that the yam Dioscorea melanophyma—which has lost sexual reproduction—evolved black, glossy bulbils that mimic co-occurring black berries and entice frugivorous birds to ingest and disperse them. Birds from 22 species fed on bulbils, with visits peaking in October–February when true fruits are scarce. Bulbil reflectance overlapped sympatric berries and was indistinguishable in a UV-sensitive avian vision model for many species, consistent with Batesian visual mimicry. Feeding trials with the dominant visitor (Pycnonotus xanthorrhous) showed short gut retention and negligible destruction, so bulbils are excreted largely intact and viable and monitoring revealed that bulbils achieved dispersal distances similar to rewarding endozoochorous plants. Thus, sensory deception that exploits fruit–frugivore signal–reward rules can restore ecologically meaningful movement after the loss of sex in asexual lineages