Floral longevity is thought to evolve by natural selection imposed by pollinators and resource constraints acting on heritable phenotypic variation. In species with pollination-induced wilting, pollination rates may also influence expression of variation, raising questions of how and when floral longevity is shaped by adaptation. We created an experimental range of pollen deposition rates in a wild population of Sabatia angularis (Gentianaceae) against the backdrop of natural abiotic variation. We investigated how pollination environment affected expression of longevity, distribution of variation, phenotypic correlations, and predispersal seed predation risk. We evaluated whether any effects of abiotic factors are modified by pollination environment. Mean and variance in floral longevity declined with increasing pollen deposition rates, and phenotypic distributions became increasingly compressed. Nevertheless, we detected a flower lifespan-number trade-off and a positive flower lifespan-size relationship, independent of treatment. Vapor pressure deficit (VPD) and intraseasonal changes constrained longevity. Suppression associated with VPD was greatest under low pollen deposition rates, where selection is expected to favor longer-lived flowers. Floral longevity had weak and inconsistent effects on predispersal seed predation risk. Our results demonstrate that phenotypic variation in floral longevity is conditionally expressed across ecological contexts, altering when variation is exposed to selection and subsequent evolutionary potential.
Spigler et al. (Sun,) studied this question.