Individual resource limitation combined with population‐wide pollen availability drives masting in the valley oak (Quercus lobata)

Abstract

1. Masting, the synchronized production of variable seed crops, is widespread among woody plants, but there is no consensus about the underlying proximate mechanisms. To understand this population-level behaviour, it is necessary to dissect the behaviour of individual trees as well as the interactions that synchronize them. 2.Here, we test a model of masting in which variability in seed set is driven by resource limitation within trees and synchrony is driven by pollen limitation due to phenological asynchrony in some years.3. We used a 35-year seed set data set and a 12-year phenological data set to analyse seed production of 84 valley oaks (Quercus lobata) in central coastal California. Individual trees varied tremendously in their seed production patterns; trees with high levels of seed production were less variable over time, but showed stronger negative autocorrelation between years, suggesting that they are more resource-limited than unproductive trees. In years of more asynchronous flowering, Q. lobata produced fewer seeds, consistent with the importance of phenological synchrony. 4. We parametrized a model with these results to investigate how individual resource limitation and population-wide pollen limitationa consequence of asynchronous flowering during cold spring temperaturesinteract to shape annual variation in seed production. The model illustrates that this proximate abiotic driver can synchronize the behaviour of individuals, resulting in population-wide seed production patterns that closely resemble the field data. 5. Synthesis. Our findings support the hypothesis that an interaction between two proximate mechanisms, individual resource limitation and environmental variation affecting population-wide pollen availability, drives masting in this population of Quercus lobata. This combination of internal and external proximate drivers may underlie masting behaviour in many wind-pollinated plants.

Masting in wind‐pollinated trees: system‐specific roles of weather and pollination dynamics in driving seed production

“…, Pesendorfer et al. ). Generally, this suggests that in fruit maturation masting species such as oaks (i.e., in which flowering and fruiting intensity are decoupled), the variability in seed production is a consequence of interacting constraints (weather and resources) limiting seed production in some years, and creating bumper crops in others (Koenig et al.…”

“…, Pesendorfer et al. ). Potentially, in such species high annual variability in seed production could emerge without the functional economies of scale (Pearse et al.…”

“…, Pesendorfer et al. ). Stabilizing selection acting on flowering phenology by increasing the seed set of plants flowering with the rest of the population was found in a number of non‐masting species, but this is not a rule (Elzinga et al.…”

“…, Pesendorfer et al. ). Weather may simultaneously affect resources of individual plants, such as in systems where precipitation is the main constraint on seed production (Espelta et al.…”

Nature beyond Linearity: Meteorological Variability and Jensen's Inequality Can Explain Mast Seeding Behavior

“…Comprehending the role of weather as a proximate cause for masting is especially important after the recent discoveries that resources invested in reproduction are acquired only during the several months prior to fruit maturation (Hoch et al, 2013;Ichie et al, 2013;Fernández-Martínez et al, 2015;Allen et al, 2017). Additionally, multiple meteorological variables can linearly or non-linearly interact to force trees to produce or not produce seeds in a given year, because weather affects both the acquisition of resources by plants, by conditioning their photosynthetic rates, and pollination efficiency (Fernández-Martínez et al, 2012;Koenig et al, 2015;Pesendorfer et al, 2016;Bogdziewicz et al, 2017a,b). We propose that rejecting weather as the most parsimonious driver of high interannual variability of seed production in masting plants was premature and should be revised.…”