Reproductive Constraints and Severe Pollinator Limitation in the Mexican Endemic Orchid Govenia capitata:...

Understanding the reproductive biology of orchids is essential for evaluating population viability and guiding conservation strategies, as their persistence often depends on complex interactions between ecological, physiological, and environmental factors. Govenia capitata, a threatened orchid endemic to the montane forests of central Mexico, had not previously been studied in this regard. We examined flowering phenology, floral longevity, stigmatic receptivity, natural and experimental pollination success, seed viability, and asymbiotic germination in two wild populations. Flowering was synchronous, with inflorescences lasting up to 57 days and individual flowers persisting for an average of 20 days. Stigmatic receptivity was detectable from the first day of anthesis and remained evident for at least eight days. Natural fruit set was very low (16.6%), while assisted self- and cross-pollination reached 100% success, demonstrating self-compatibility despite the inability for autonomous selfing due to floral structure. Seed viability differed significantly among treatments, being lowest in selfed capsules (11%) and highest in cross-pollinated ones (32%), representing a 65% reduction and reflecting severe inbreeding depression that extended to germination performance. In vitro germination success also varied, with the L-arginine medium yielding the highest values (46% for cross-pollinated seeds and 44% for naturally pollinated seeds), though post-germination survival requires optimization for conservation applications. Despite the conspicuous floral display, floral visitation was extremely rare and the pollinator identity remains unknown, with only one potentially effective visitor observed during 144 h of monitoring, and most floral visitors were non-pollinating arthropods such as crab spiders, weevils, hymenopterans, and thrips. Population density varied dramatically (26-fold) between sites separated by less than 1 km, indicating pronounced sensitivity to local environmental conditions. These findings reveal that reproduction in G. capitata is constrained by both extrinsic (pollinator limitation) and intrinsic factors (reduced seed viability), which collectively jeopardize long-term population persistence. From a conservation perspective, protecting montane forest remnants and pollinator communities is essential, while the demonstrated potential of asymbiotic germination provides a complementary tool for ex situ propagation and management of this endemic orchid.