Reproductive Ecology of Loeselia mexicana (Polemoniaceae): Protandry, Self-Incompatibility and a Generalized Pollination System Challenge Traditional Ornithophilous Assumptions

Loeselia mexicana (Polemoniaceae) is a Mexican shrub with significant medicinal value since pre-Hispanic times. Despite its ethnobotanical importance and apparent role in supporting pollinator communities, detailed information about its reproductive biology remains limited, hindering conservation efforts for this increasingly harvested species. We investigated the reproductive ecology of L. mexicana across two flowering seasons (2023–2024 and 2024–2025) in central Mexico through an integrated approach examining flowering phenology, floral morphology, sexual maturation sequence, nectar characteristics, floral visitors, and breeding system experiments. Flowering occurs from September to March, peaking in October. Flowers exhibit protandry, with anther dehiscence on days 1–2 and stigma receptivity from day 2 onward (flower lifespan: 2.85 ± 0.11 days). Maximum nectar production (1.46 ± 0.05 µL per flower; 193.13 ± 8.8 mg/mL) coincided with peak visitor activity. Despite possessing classic ornithophilous traits, we recorded 21 floral visitor species (5 hummingbirds, 3 hymenopterans, 13 butterflies) with similar visitation patterns, challenging previous assumptions about pollination specialization. Controlled pollination experiments confirmed self-incompatibility, with cross-pollination producing significantly more seeds than autonomous selfing. Our findings reveal that L. mexicana maintains a generalized pollination system, while protandry and self-incompatibility enforce outcrossing, providing critical baseline information for conservation strategies.