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Changes to flowering duration (i.e. the 10th–90th interquantile range) from 1940 to 2010. (a) Absolute shifts (ΔIQRY). (b) Shifts relative to 1940 duration (ΔRIQRY). Points give the mean of the posterior distribution, thick lines give the 50% CI, and thin lines give the 80% CI. Dark green indicates a > 90% probability, light green a > 75% probability, and gray a ≤ 75% probability of changes to duration.
Source publication
Changes to flowering phenology are a key response of plants to climate change. However, we know little about how these changes alter temporal patterns of reproductive overlap (i.e. phenological reassembly).
We combined long‐term field (1937–2012) and herbarium records (1850–2017) of 68 species in a flowering plant community in central North America...
Citations
... It is well documented that phenological data extracted from herbarium specimens covering a wide range of plant taxa at local scales can often provide comparable information to field-based phenology surveys in temperate regions (e.g. Davis et al., 2015;Austin et al., 2024). Using simulations, Park et al. (2024) found that herbarium data accurately predicted the timing and duration of flowering phenology at the population level. ...
The online mobilization of herbaria has made tens of millions of specimens digitally available, revolutionizing investigations of phenology and plant responses to climate change. We identify two main themes associated with this growing body of research and highlight a selection of recent publications exemplifying: investigating phenology at large spatial and temporal scales and in understudied locations and testing long‐standing theories and novel questions in ecology and evolution that were not previously answerable. We explore strengths and limitations of using digitized herbarium specimens in phenology research, including: issues of sampling; reliability, transferability, and biases; and ethical and social justice considerations. This field will see further breakthroughs as herbaria around the world continue to mobilize and digitally interlink their collections. New developments will likely come from advances in technology, international collaborations, and including understudied plant taxa and regions such as the Arctic and the tropics. Advances in technology are already improving digitization workflows and speeding the collection of phenology data from digital specimens.
... In the case of flowering season, our study detected a median increase of 0.023 d yr -1 and a median absolute change of 0.138 d yr -1 . Increases in flowering seasons or flowering durations have been reported across the literature, mostly from field studies, meta-analyses, and warming experiments in the field (Høye et al., 2013;Zhou et al., 2022;Chen et al., 2023;Austin et al., 2024). Similarly to changes in flowering date, the reported magnitude of change in flowering season duration varies greatly between study systems and species. ...
Flowering phenology is an indicator of the impact of climate change on natural systems. Anthropogenic climate change has progressed over more than two centuries, but ecological studies are mostly short in comparison. Here we harness the large‐scale digitization of herbaria specimens to investigate temporal trends in flowering phenology at a global scale.
We trained a convolutional neural network model to classify images of angiosperm herbarium specimens as being in flower or not in flower. This model was used to infer flowering across 8 million specimens spanning a century and global scales. We investigated temporal trends in mean flowering date and flowering season duration within ecoregions.
We found high diversity of temporal trends in flowering seasonality across ecoregions with a median absolute shift of 2.5 d per decade in flowering date and 1.4 d per decade in flowering season duration. Variability in temporal trends in phenology was higher at low latitudes than at high latitudes.
Our study demonstrates the value of digitized herbarium specimens for understanding natural dynamics in a time of change. The higher variability in phenological trends at low latitudes likely reflects the effects of a combination of shifts in temperature and precipitation seasonality, together with lower photoperiodic constraints to flowering.
Synopsis
Climate change is simultaneously increasing atmospheric carbon dioxide concentrations ([CO2]) and temperatures. We conducted a multi-factorial growth chamber experiment to examine how these climate change factors interact to influence the expression of ecologically relevant morphological and phenological traits, clines in these traits, and natural selection on these traits using diverse accessions of Boechera stricta (Brassicaceae) sourced from a broad elevational gradient in Colorado, USA. Plastic shifts in a key allocation trait (root mass fraction) in response to temperature accorded with the direction of selection via the probability of flowering, indicating that plasticity in this trait could be adaptive. However, plasticity in a foliar functional trait (leaf dry matter content) in response to temperature and [CO2] did not align with the direction of selection, indicating that plasticity could reduce fitness . For another ecologically important phenotype, selection favored resource acquisitive trait values (higher specific leaf area) under elevated [CO2] and resource conservative trait values (lower specific leaf area) at lower [CO2], despite the lack of plasticity in this trait. This pattern of selection counters published reports that elevated [CO2] induces low specific leaf area but could enable plants to reproduce across a greater period of the growing season under increasingly warm climates. Indeed, warmer temperatures prolonged the duration of flowering. This plasticity is likely adaptive, as selection favored increased flowering duration in the higher temperature treatment level. Thus, climate change could impose novel and unanticipated patterns of natural selection on plant traits, and plasticity in these traits can be a maladaptive response to stress.
Background
The frequency and intensity of droughts are expected to increase under global change, driven by anthropogenic climate change and water diversion. Precipitation is expected to become more episodic under climate change, with longer and warmer dry spells, although some areas might become wetter. Diversion of freshwater from lakes and rivers and groundwater pumping for irrigation of agricultural fields are lowering water availability to wild plant populations, increasing the frequency and intensity of drought. Given the importance of seasonal changes and extremes in soil moisture to influence plant reproduction, and because the majority of plants are flowering plants and most of them depend on pollinators for seed production, this review focuses on the consequences of drought on different aspects of reproduction in animal-pollinated angiosperms, emphasizing interactions among drought, flowering and pollination.
Scope
Visual and olfactory traits play crucial roles in attracting pollinators. Drought-induced floral changes can influence pollinator attraction and visitation, together with pollinator networks and flowering phenology, with subsequent effects on plant reproduction. Here, we review how drought influences these different aspects of plant reproduction. We identify knowledge gaps and highlight areas that would benefit from additional research.
Conclusions
Visual and olfactory traits are affected by drought, but their phenotypic responses can vary with floral sex, plant sex, population and species. Ample phenotypic plasticity to drought exists for these traits, providing an ability for a rapid response to a change in drought frequency and intensity engendered by global change. The impact of these drought-induced changes in floral traits on pollinator attraction, pollen deposition and plant reproductive success does not show a clear pattern. Drought affects the structure of plant–pollinator networks and can modify plant phenology. The impact of drought on plant reproduction is not always negative, and we need to identify plant characteristics associated with these more positive responses.
