To pupate or not to pupate: a case study of an obligate pollination mutualism in Glochidion ferdinandi (Phyllanthaceae) and Epicephala colymbetella (Gracillariidae)

Obligate pollination mutualisms have recently been recorded in the Glochidion genus with Epicephala moth associates (leaf-flower and leaf-flower moths). There is limited literature on Australian Glochidion species and their pollinators. Glochidion ferdinandi occurs predominantly across the east coast of Queensland, Australia and has an obligate pollination association with Epicephala colymbetella. Early descriptions of G. ferdinandi describe the encapsulation of the adult moth within the fruit. In the present study, observations and fruit dissections were recorded to analyse the role of symbionts within this mutualism, pollinator life history and the flowering phenology of the host. Our study confirmed this rare behaviour in which E. colymbetella pupated within G. ferdinandi fruit in which adult moths were retained until fruit dehiscence. Fruit dissections identified two other species alongside E. colymbetella, a seed consuming Spilomelinae moth and parasitoid Bracon wasp. Although both moth species were found to reduce the number of surviving ovules in the fruit, E. colymbetella also provided a pollination benefit to G. ferdinandi. Furthermore, the life histories of E. colymbetella and phenology of G. ferdinandi were observed to be highly synchronous, with larvae developing concurrently with ovules after flower fertilisation. Retention of the adult moth in fruit has only previously been recorded in one other Epicephala (lanceolaria).