Data from: Flowers of a South African succulent plant predict tomorrow’s weather, synchronizing flower opening with pollinator activity

1. Day-to-day synchrony between flower opening and pollinator activity is
important for maximizing plant fitness. A succulent, Bulbine frutescens
(L.) Willd., is an ideal model for studying synchrony in response to daily
weather as it flowers year-round. Additionally, it has self-incompatible
flowers that open for just one day, making it essential that flower
opening matches pollinator activity. 2. Observations were made on urban
plants in California, USA, with validation measurements in the native
range in South Africa. Independent observations indicated that flowers
open primarily after favorable conditions the previous day, specifically
air temperatures above 15°C. Solar radiation was experimentally shown to
have limited, but significant effects. Pollinators, mostly bee species,
had similar temperature thresholds to flowers. 3. Developmental
constraints on flowers were hypothesized to delay opening by a day. Flower
bud growth was closely related to temperature, with warm days resulting in
sufficient growth for buds to become competent to open the following day.
Lab experiments demonstrated that competent flowers were suppressed from
opening until at least 16 hours was accumulated in which temperatures were
above 12°C; thus, on many cool days, sufficient development to cause
flower opening would only occur a day after favorable weather. 4. Based
upon regression models of pollinator and flower response to weather,
fitness was estimated as a function of synchrony, over twenty years of
weather from California and across the natural range in South Africa.
Flowers responding to either the previous day’s or current day’s weather
resulted in similar predicted fitness, with flower response to the current
day’s weather leading to a slightly higher cost, i.e. flowers opened when
pollinators would be absent. 5. Multiple temperature-responsive
constraints on bud growth and development result in delays in flower
opening, such that flower opening occurs the day after favorable weather.
Given the high correlation between daily temperatures in the USA and South
African winter-rainfall environments, behavior predicting the following
day’s weather results in high fitness. Many pollinators share similar
temperature thresholds for activity, thus diverse plants may have evolved
predictive behavior maximizing daily synchrony between pollinators and
flower opening.