Breeding system of the critically endangered Lakela's Mint and influence of plant height on pollinators and seed output

Abstract

AbstractUnderstanding reproductive systems of rare plants is critical for conservation efforts. Lakela's Mint, Dicerandra immaculata Lakela var. immaculata, is an endangered plant endemic to an approximately 4.8‐km long area in Florida, USA. We used an experimental garden and three populations of Lakela's Mint to determine: (1) what is the breeding system (autonomous, asexual, self‐fertile, cross‐fertile) and are insects necessary for reproduction; (2) which native and nonnative insect species visit flowers and is the frequency of visits to a plant influenced by its height; (3) does the number of flowers visited within a plant by individual insects differ among native and nonnative insect species and due to plant height; and (4) is seed output influenced by plant height? Our results indicate that the breeding system of Lakela's Mint was facultative outcrossing. Insect‐pollinated flowers produced more seeds than flowers that reproduced autonomously or asexually. The honey bee Apis mellifera L., a nonnative species, was the most frequent visitor to plants and visited more flowers within plants than native pollinators, but its behavior was not influenced by plant height. Native pollinators such as Bombus impatiens Cresson were attracted more frequently to shorter plants, but visited fewer flowers than on taller plants. Despite having fewer total and pollinated flowers, shorter plants had a higher output of intact seeds than taller plants, which could be due to differences in efficiency between native and nonnative pollinators or other factors. Our results add insight into factors influencing seed output and interactions between pollinators and rare plants.