Mast seeding, or masting, is the highly variable and spatially synchronous production of seeds by a population of plants. The production of variable seed crops is typically correlated with weather, ...so it is of considerable interest whether global climate change has altered the variability of masting or the size of masting events. We compiled 1086 datasets of plant seed production spanning 1900–2014 and from around the world, and then analysed whether the coefficient of variation (CV) in seed set, a measure of masting, increased over time. Over this 115-year period, seed set became more variable for plants as a whole and for the particularly well-studied taxa of conifers and oaks. The increase in CV corresponded with a decrease in the long-term mean of seed set of plant species. Seed set CV increased to a greater degree in plant taxa with a tendency towards masting. Seed set is becoming more variable among years, especially for plant taxa whose masting events are known to affect animal populations. Such subtle change in reproduction can have wide-ranging effects on ecosystems because seed crops provide critical resources for a wide range of taxa and have cascading effects throughout food webs.
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Mast seeding is a widespread reproductive phenomenon in plants, and testing evolutionary drivers is challenging. New research uses four decades of individual-tree reproduction data and demonstrates ...selection for hypersensitivity to a weather cue, high temporal variability, and high synchrony with neighbours.
Mast seeding is a widespread reproductive phenomenon in plants, and testing evolutionary drivers is challenging. New research uses four decades of individual-tree reproduction data and demonstrates selection for hypersensitivity to a weather cue, high temporal variability, and high synchrony with neighbours.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Biogeography and phylogeny of masting Pearse, Ian S.; LaMontagne, Jalene M.; Lordon, Michael ...
New phytologist,
September 2020, Volume:
227, Issue:
5
Journal Article
Peer reviewed
Open access
Interannual variability of seed crops (CVp) has profound consequences for plant populations and food webs, where high CVp is termed ‘masting’. Here we ask: is global variation in CVp better predicted ...by plant or habitat differences consistent with adaptive economies of scale, in which flower and seed benefits increase disproportionately during mast years; or by passive mechanisms, in which seed production responds to variation in resource availability associated with climate variability?
To address this question, we compiled a dataset for phylogenetic comparative analysis of long-term fruit/seed production for plants comprising 920 time series spanning 311 plant species.
Factors associated with both adaptive benefits of CVp (wind pollination and seed dispersal) and climatic variability (variability of summer precipitation) were among the best predictors of global variation in CVp. We observed a hump-shaped relationship between CVp and latitude and intermediate phylogenetic and geographic signals in CVp.
CVp is patterned nonrandomly across the globe and over the plant tree of life, where high CVp is associated with species benefiting from economies of scale of seed or flower production and with species that experience variable rainfall over summer months when seeds usually mature.
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Our overall objective is to synthesize mast-seeding data on North American Pinaceae to detect characteristic features of reproduction (i.e. development cycle length, serotiny, dispersal agents), and ...test for patterns in temporal variation based on weather variables. We use a large dataset (
= 286 time series; mean length = 18.9 years) on crop sizes in four conifer genera (
,
,
,
) collected between 1960 and 2014. Temporal variability in mast seeding (CVp) for 2 year genera (
,
,
) was higher than for
(3 year), and serotinous species had lower CVp than non-serotinous species; there were no relationships of CVp with elevation or latitude. There was no difference in family-wide CVp across four tree regions of North America. Across all genera, July temperature differences between bud initiation and the prior year (Δ
) was more strongly associated with reproduction than absolute temperature. Both CVp and Δ
remained steady over time, while absolute temperature increased by 0.09°C per decade. Our use of the Δ
model included a modification for
, which initiates cone primordia 2 years before seedfall, as opposed to 1 year. These findings have implications for how mast-seeding patterns may change with future increases in temperature, and the adaptive benefits of mast seeding. This article is part of the theme issue 'The ecology and evolution of synchronized seed production in plants'.
Aim
The evolution of fruit size is poorly understood, though long‐standing hypotheses, the dispersal syndrome hypothesis and correlated evolution hypothesis, have highlighted the influence of ...frugivores and phylogeny on fruit size variation.
Location
Interaction networks were extracted from studies carried out in Asia, Europe, Africa, Hawaii, Australia, New Zealand and the Neotropics.
Time Period
Up to 50 years between 1970 and 2022.
Major Taxa Studied
Frugivores (birds and mammals) and fleshy‐fruited plants.
Methods
We compiled a global data set on fruit size (i.e. width and length) and plant traits (i.e. leaf area and plant height) for 349 fleshy‐fruited plants, and the body mass of frugivores from 326 interaction networks. We constructed a plant phylogeny from a mega‐tree containing 74,533 vascular plant species and we calculated Pagel's λ to assess the phylogenetic signal in plant traits and fruit size. Phylogenetic generalized linear mixed model (PGLMM) was used to reveal relationships between fruit size and plant traits as well as the body mass of interacting frugivores. We used phylogenetic partial R2s regression model to tease apart the effects of body mass of frugivores, leaf area, plant height and plant phylogeny on the evolution of fruit size.
Results
We show that the global variation in fruit width is better explained by frugivorous assemblages than by phylogeny and plant functional traits (leaf area and plant height). Despite the significant evolutionary correlation between fruit length and width, fruit length appears to be more phylogenetically constrained and less sensitive to frugivore‐driven selection than fruit width.
Main Conclusion
In light of the two original hypotheses, our study demonstrates a global phylogenetic constraint on fruit length and frugivore‐driven selection on fruit width, provides a novel mechanistic explanation for the evolution of fruit size across fleshy‐fruited plant species. Our findings contribute to a deeper understanding of the complex interplay between frugivory, phylogeny and plant traits in the evolution of fruit size, offering valuable insights into the broader context of published findings and hypotheses in this field.
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Atmospheric variability can impact biological populations by triggering facultative migrations, but the stability of these atmosphere-biosphere connections may be vulnerable to climate change. As an ...example, we consider the leading mode of continental-scale facultative migration of Pine Siskins, where the associated ecological mechanism is changes in resource availability, with a mechanistic pathway of climate conditions affecting mast seeding patterns in trees which in turn drive bird migration. The three summers prior to pine siskin irruption feature an alternating west-east mast-seeding dipole in conifer trees with opposite anomalies over western and eastern North America. The climate driver of this west-east mast-seeding dipole, referred to as the North American Dipole, occurs during summer in the historical record, but shifts to spring in response to future climate warming during this century in a majority of global climate models. Identification of future changes in the timing of the climate driver of boreal forest mast seeding have broadly important implications for the dynamics of forest ecosystems.
Display omitted
•The first test of the bird irruption mechanism using mast seeding data•Projected climate change shifts the North American Dipole from its current summer timing to spring.•This discovery provides far-reaching impacts on studying boreal forests and their associated species.
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Ecological processes, such as migration and phenology, are strongly influenced by climate variability. Studying these processes often relies on associating observations of animals and plants with ...climate indices, such as the El Niño–Southern Oscillation (ENSO). A common characteristic of climate indices is the simultaneous emergence of opposite extremes of temperature and precipitation across continental scales, known as climate dipoles. The role of climate dipoles in shaping ecological and evolutionary processes has been largely overlooked. We review emerging evidence that climate dipoles can entrain species dynamics and offer a framework for identifying ecological dipoles using broad-scale biological data. Given future changes in climatic and atmospheric processes, climate and ecological dipoles are likely to shift in their intensity, distribution, and timing.
Climate variability is cataloged using climate indices that ecologists rely on to study phenology, migration, and population dynamics.Climate dipoles are a common characteristic of climate variability that emerge in terrestrial and marine systems as contrasting patterns in anomalies of temperature or precipitation appearing at two different geographic locations at the same time.Climate dipoles have the potential to entrain continent-wide processes ranging from bird migration to plant reproduction and produce ecological dipoles.Ecological dipoles can be identified by applying approaches of space–time analysis to biological and climatological observations collected at continental scales.Given the altered patterns of atmospheric processes, increasing synchrony of weather, and land-use-driven changes in climate, it is likely that climate and ecological dipoles will shift dramatically in the future.
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Tree fecundity and recruitment have not yet been quantified at scales needed to anticipate biogeographic shifts in response to climate change. By separating their responses, this study shows ...coherence across species and communities, offering the strongest support to date that migration is in progress with regional limitations on rates. The southeastern continent emerges as a fecundity hotspot, but it is situated south of population centers where high seed production could contribute to poleward population spread. By contrast, seedling success is highest in the West and North, serving to partially offset limited seed production near poleward frontiers. The evidence of fecundity and recruitment control on tree migration can inform conservation planning for the expected long-term disequilibrium between climate and forest distribution.
1. Mast seeding is the synchronous and highly variable production of seed by a population of plants. Mast seeding results from the behaviour of individuals; however, little is known about the ...synchrony of individuals at local scales. 2. We address two primary questions at a within-population (17-36 ha study plots) and individual level: (i) How variable is seed production between and within years? (ii) How synchronized is seed production between individuals? 3. We monitored annual cone production of 356 Picea glauca (white spruce) from 1990 to 2005 within four plots spanning a total distance of 5.3 km in the Yukon Territory, Canada. 4. Spearman correlations (rs) were conducted to test for synchrony. Overall, the trees were moderately synchronous (mean$r_s (\pm SE)$of$0.52 \pm 0.14$), and synchrony was statistically detectable ($r_s > 0$) over all distances. Individuals < 75 m apart were highly synchronous ($0.64 \pm 0.18$), and correlations dropped to$0.33 \pm 0.07$for trees > 3 km apart. There was considerable variation in cone production patterns among pairs of individuals. 5. The number of mast years per plot varied from one to three. During a mast year, many individuals within plots produced large cone crops, with more variability between individuals in low mean cone years. Individual trees had dominant endogenous cycles varying from none to 1- 5 years. Forty-four per cent of trees had no significant lag, 23% a negative 1-year lag, and 20% a positive 3-year lag. Basal area did not influence lags, but trees with higher mean cone production throughout the study were more likely to have a 3-year lag compared with no lag. 6. The scale of highest synchrony coincided with the scale at which the dominant seed predator in the area, the territorial red squirrel (Tamiasciurus hudsonicus), operates. This may be the scale at which selection for synchrony occurs. 7. Based on high synchrony locally, high synchrony within a mast year, and multiple lags in cone production by individuals, both available resources and strong weather cues appear to play roles in the observed patterns.
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Populations of many tree species exhibit synchronous and highly temporally variable seed crops across years. This is called mast seeding, and there are two predominant hypotheses for this pattern of ...reproduction: pollination efficiency and seed-predator satiation. Mast seeding studies typically involve records of population-level reproduction, with less information on the characteristics of reproductive structures. Here, we use data across 6 years (2012–2017), spanning a range of population-level cone conditions, to characterize (i) white spruce (Picea glauca (Moench) Voss) cone lengths and seeds per cone, and (ii) levels of seed predation. We quantified population-level cone production and collected 1399 cones from a total of 38 trees in the Huron Mountains, Michigan, USA. Linear mixed models showed that mean and minimum cone lengths varied significantly across years; both being longest during the greatest cone production year. Larger cones had more seeds and the slopes of the relationships as well as the intercepts varied significantly across years. Generalized linear mixed models and Akaike’s information criterion model selection showed that cones with insect predation damage was greatest when population-level reproduction was the lowest, with a mean proportion of cones damaged 0.82 in that year. Our findings show that white spruce cone characteristics and losses to insect seed predation vary temporally, and follow expectations based on mast seeding hypotheses.
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