Phenology, floral biology, morphology and hawkmoth pollination of Calliandra magdalenae (Fabaceae) in modified landscapes of the Soconusco region, Mexico

Abstract

Despite the recognized importance of nocturnal pollinators, studies focusing on nocturnally pollinated plants remain limited. Calliandra magdalenae (Fabaceae) is a species that exhibits floral morphology adapted to hawkmoths. The principal aim of this study was to determine the phenological patterns, whether the species reproduces in rural environments, and how climatic conditions influence their floral growth. For two years, the reproductive phenology of C. magdalenae was studied. Flower morphology was assessed using both univariate and multivariate analyses. Floral biology and environmental variables were monitored over 27 days, and their relationships were analyzed. Nocturnal pollinator observations were carried out over five nights. The phenology of C. magdalenae is synchronous among individuals and consists of extended flowering during the wet season and a fruiting period during the dry season. Two distinct floral morphs were documented based on the staminal tube lengths. Increased light is positively correlated with floral bud production, while higher humidity favored floral anthesis. The species exhibits low fruit set rates, possibly due to the low pollination visitation rates and habitat fragmentation. Four hawkmoth species were identified as principal pollinators, each with specific visitation behaviors. Utilizing different pollinators can enhance pollen dispersal. This study demonstrates that plants living in modified landscapes utilize complex strategies to sustain their reproduction.