Spatial decoupling and herbivory tolerance stabilise a nursery pollination mutualism in an aquatic plant

Nursery pollination systems face an inherent conflict: pollinator larvae consume seeds or floral tissues. Known conflict-resolution mechanisms, including host sanctions, selective abortion, chemical defences, and third-party suppression, operate in systems where larvae feed on seeds. How mutualisms are stabilised when larvae feed on vegetative tissues remains unclear. We investigated a novel nursery pollination involving the dioecious aquatic plant Ottelia jingxiensis, combining field observations, exclusion experiments, floral manipulation, and chemical and colour analyses. We tested whether spatial decoupling of oviposition and larval feeding eliminates the conflict (conflict avoidance), or whether herbivory tolerance is required (conflict resolution). Shore flies (Hydrellia sp.) are primary pollinators; rewardless female flowers attract them via imperfect Bakerian mimicry. Shore flies oviposit on persistent female calyces, but larvae migrate to submerged leaves. Foliar herbivory is substantial (c. 62% of leaves with > 30% area consumed) yet uncorrelated with seed set (R² < 0.001), consistent with substantial tolerance. A parasitoid wasp (Chaenusa naiadum) parasitises 67.5-80.1% of pupae and provides supplementary pollination but does not reduce within-generation herbivory or seed predation. Spatial decoupling and herbivory tolerance jointly resolve the pollination-herbivory conflict without requiring host sanctions or biotic regulation, representing a previously unrecognised stabilisation mechanism in nursery pollination.