Mechanisms of mast seeding: resources, weather, cues, and selection

Abstract

546I.546II.547III.548IV.552V.554VI.556VII.558VIII.558IX.559559References559 Summary Mast seeding is a widespread and widely studied phenomenon. However, the physiological mechanisms that mediate masting events and link them to weather and plant resources are still debated. Here, we explore how masting is affected by plant resource budgets, fruit maturation success, and hormonal coordination of cues including weather and resources. There is little empirical support for the commonly stated hypothesis that plants store carbohydrates over several years to expend in a high‐seed year. Plants can switch carbohydrates away from growth in high‐seed years, and seed crops are more probably limited by nitrogen or phosphorus. Resources are clearly involved in the proximate mechanisms driving masting, but resource budget (RB) models cannot create masting in the absence of selection because some underlying selective benefit is required to set the level of a ‘full’ seed crop at greater than the annual resource increment. Economies of scale (EOSs) provide the ultimate factor selecting for masting, but EOSs probably always interact with resources, which modify the relationship between weather cues and reproduction. Thus, RB and EOS models are not alternative explanations for masting – both are required. Experiments manipulating processes that affect mast seeding will help clarify the physiological mechanisms that underlie mast seeding.

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

“…In particular, the mechanisms that connect the variability of weather to the plants’ seed production are still unclear, even in light of considerable interest and research effort (Pearse et al. ). There is consensus that flowering and pollination dynamics play a central role in synchronizing seed production in populations of wind‐pollinated species, but surprisingly few studies have directly investigated the relationship between airborne pollen and seed production (Sarvas , García‐Mozo et al.…”

Edible dormice (Glis glis) avoid areas with a high density of their preferred food plant - the European beech

“…Secondly, seed predators that are swamped in mast years may actually cache more seeds than they are able to retrieve, which would benefit seed dispersal and germination [10]. The third explanation involves weather conditions, which may either enhance or impair pollination success directly, or may affect flowering because selection has favored plants that all respond to weather characteristics in the same way, resulting in high synchrony [11]. Under all these scenarios synchrony between individual plants maybe further enhanced by long-term effects of the depletion of resources in masting years.…”

“…We used pollen densities as an indicator, but since pollen densities may not reflect seed densities in all species (e.g. [11]), we additionally confirmed seed densities visually in the field. However, edible dormice already have to know in spring whether a year will be a full or non-mast year, because growth of gonads and mating has to occur right away, to make sure ripe beech seeds are available to juveniles for prehibernation fattening [31].…”

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

“…Such an irregular pattern of producing seeds has strong consequences in ecosystems, leading to cascading effects throughout the food web (Ostfeld and Keesing, 2000;Bogdziewicz et al, 2016). The mechanisms behind this intriguing behavior have puzzled ecologists for decades (Norton and Kelly, 1988;Sork et al, 1993;Espelta et al, 2008;Fernández-Martínez et al, 2012, 2017Crone and Rapp, 2014;Pearse et al, 2016), leading to the formulation of several hypotheses about ultimate and proximate causes of this bizarre reproductive behavior.…”

“…Amongst proximate causes, meteorological variability may be an inseparable component of variable seed production , because weather is the most evident source of interannual variability that can affect plant productivity. However, it has often been claimed that factors other than weather have to be involved in driving mast seeding behavior (Koenig and Knops, 2000;Kelly and Sork, 2002;Crone and Rapp, 2014;Pearse et al, 2016).…”