Flowering synchrony drives reproductive success in a wind‐pollinated tree

Abstract

Synchronised and quasi‐periodic production of seeds by plant populations, known as masting, is implicated in many ecological processes, but how it arises remains poorly understood. Flowering and pollination dynamics are hypothesised to provide the mechanistic link for the observed relationship between weather and population‐level seed production. We report the first experimental test of the phenological synchrony hypotheses as a driver of pollen limitation in mast seeding oaks (Quercus ilex). Higher flowering synchrony yielded greater pollination efficiency, which resulted in 2‐fold greater seed set in highly synchronised oaks compared to asynchronous individuals. Pollen addition removed the negative effect of asynchronous flowering on seed set. Because phenological synchrony operates through environmental variation, this result suggests that oak masting is synchronised by exogenous rather than endogenous factors. It also points to a mechanism by which changes in flowering phenology can affect plant reproduction of mast‐seeding plants, with subsequent implications for community dynamics.

Environmental variation drives continental‐scale synchrony of European beech reproduction

“…Both exogenous factors, like environmental conditions, and endogenous factors, like flower abscission and pollination, have been considered as drivers of spatial synchrony in models of proximate drivers of masting (Satake and Iwasa 2002 a , Lyles et al 2015, Noble et al 2018, Schermer et al 2019). Depending on specific assumptions, these theoretical models may require some form of coupling of seed production of nearby plants to create synchrony (e.g., pollen coupling), alongside the effect of correlated environmental fluctuations (Satake and Iwasa 2002 a , Noble et al 2018, Bogdziewicz et al 2020 d ). In our MRM analysis, proximity played no apparent role in influencing beech masting synchrony after controlling for synchrony in environmental variation.…”

Leaf phenology correlates with fruit production in European beech (Fagus sylvatica) and in temperate oaks (Quercus robur and Quercus petraea)

“…Variation of canopy duration impacts nutrient remobilization, which can make elements less available for reproduction and impact fruit production. While we worked at the population scale, future research should focus on individual plants, as they present considerable variation in fecundity (Davi et al 2016;Hacket-Pain et al 2019), leaf phenology that can impact individual tree growth (Delpierre et al 2017), and age and size that impacts both mean fecundity and inter-annual variation of seed production (Pesendorfer et al 2020;Bogdziewicz et al 2020b). Inter-annual and inter-individual variation of leaf phenology could improve our understanding of resource allocation and variability in plant reproductive patterns.…”

“…Flower phenology is known to be a major driver of masting. For example, the variability of flower phenology and the synchrony during the period of pollination have a direct influence on the intensity of fructification (Koenig et al 2015;Bogdziewicz et al 2020b). Growing season length, referred to here as canopy duration, i.e., the period between leaf unfolding and leaf senescence, might also be important for reproduction.…”

Climate change and plant reproduction: trends and drivers of mast seeding change

“…In that group, masting synchrony appears to be determined by a pollination Moran effect, i.e. pollination success is driven by variation in spring weather conditions [66,67]. Mechanisms responsible for changes in spatial synchrony of reproduction in F. sylvatica were less clear, as the weather cue that correlated with seed production showed no trends in spatial synchrony [44].…”