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1. Temperature controls phenology in continuously flowering Protea species of subtropical Africa

   https://doi.org/10.1002/aps3.1232  

   Daru, Barnabas H. ; Kling, Matthew M. ; Meineke, Emily K. ; van Wyk, Abraham E. ( March 2019 , Applications in Plant Sciences)

   Herbarium specimens are increasingly used as records of plant flowering phenology. However, most herbarium‐based studies on plant phenology focus on taxa from temperate regions. Here, we explore flowering phenologic responses to climate in the subtropical plant genusProtea(Proteaceae), an iconic group of plants that flower year‐round and are endemic to subtropical Africa.

   We present a novel, circular sliding window approach to investigate phenological patterns developed for species with year‐round flowering. We employ our method to evaluate the extent to which site‐to‐site and year‐to‐year variation in temperature and precipitation affect flowering dates using a database of 1727 herbarium records of 25Proteaspecies. We also explore phylogenetic conservatism in flowering phenology.

   We show that herbarium data combined with our sliding window approach successfully captured independently reported flowering phenology patterns (r= 0.93). Both warmer sites and warmer years were associated with earlier flowering of 3–5 days/°C, whereas precipitation variation had no significant effect on flowering phenology. Although species vary widely in phenological responsiveness, responses are phylogenetically conserved, with closely related species tending to shift flowering similarly with increasing temperature.

   Our results point to climate‐responsive phenology for this important plant genus and indicate that the subtropical, aseasonally flowering genusProteahas temperature‐driven flowering responses that are remarkably similar to those of better‐studied northern temperate plant species, suggesting a generality across biomes that has not been described elsewhere.

    

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2. Differences in flowering time maintain species boundaries in a continental radiation of Viburnum

   https://doi.org/10.1002/ajb2.1292  

   Spriggs, Elizabeth L. ; Schlutius, Caroline ; Eaton, Deren A. ; Park, Brian ; Sweeney, Patrick W. ; Edwards, Erika J. ; Donoghue, Michael J. ( May 2019 , American Journal of Botany)

   We take an integrative approach in assessing how introgression and Pleistocene climate fluctuations have shaped the diversification of the coreLentagoclade ofViburnum, a group of five interfertile species with broad areas of sympatry. We specifically tested whether flowering time plays a role in maintaining species isolation.

   RAD‐seq data for 103 individuals were used to infer the species relationships and the genetic structure within each species. Flowering times were compared among species on the basis of historical flowering dates documented by herbarium specimens.

   Within each species, we found a strong relationship between flowering date and latitude, such that southern populations flower earlier than northern ones. In areas of sympatry, the species flower in sequence rather than simultaneously, with flowering dates offset by ≥9 d for all species pairs. In two cases it appears that the offset in flowering times is an incidental consequence of adaptation to differing climates, but in the recently diverged sister speciesV. prunifoliumandV. rufidulum, we find evidence that reinforcement led to reproductive character displacement. Long‐term trends suggest that the two northern‐most species are flowering earlier in response to recent climate change.

   We argue that speciation in theLentagoclade has primarily occurred through ecological divergence of allopatric populations, but differences in flowering time were essential to maintain separation of incipient species when they came into secondary contact. This combination of factors may underlie diversification in many other plant clades.

    

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3. Species-specific flowering phenology responses to experimental warming and drought alter herbaceous plant species overlap in a temperate–boreal forest community

   https://doi.org/10.1093/aob/mcaa156  

   Rice, Karen E ; Montgomery, Rebecca A ; Stefanski, Artur ; Rich, Roy L ; Reich, Peter B ( August 2020 , Annals of Botany)

   Abstract Background and Aims Warmer temperatures and altered precipitation patterns are expected to continue to occur as the climate changes. How these changes will impact the flowering phenology of herbaceous perennials in northern forests is poorly understood but could have consequences for forest functioning and species interactions. Here, we examine the flowering phenology responses of five herbaceous perennials to experimental warming and reduced summer rainfall over 3 years. Methods This study is part of the B4WarmED experiment located at two sites in northern Minnesota, USA. Three levels of warming (ambient, +1.6 °C and +3.1 °C) were crossed with two rainfall manipulations (ambient and 27 % reduced growing season rainfall). Key Results We observed species-specific responses to the experimental treatments. Warming alone advanced flowering for four species. Most notably, the two autumn blooming species showed the strongest advance of flowering to warming. Reduced rainfall alone advanced flowering for one autumn blooming species and delayed flowering for the other, with no significant impact on the three early blooming species. Only one species, Solidago spp., showed an interactive response to warming and rainfall manipulation by advancing in +1.6 °C warming (regardless of rainfall manipulation) but not advancing in the warmest, driest treatment. Species-specific responses led to changes in temporal overlap between species. Most notably, the two autumn blooming species diverged significantly in their flowering timing. In ambient conditions, these two species flowered within the same week. In the warmest, driest treatment, flowering occurred over a month apart. Conclusions Herbaceous species may differ in how they respond to future climate conditions. Changes to phenology may lead to fewer resources for insects or a mismatch between plants and pollinators. 

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4. Spatial variation in bidirectional pollinator-mediated interactions between two co-flowering species in serpentine plant communities

   https://doi.org/10.1093/aobpla/plab069  

   Stanley, Amber ; Martel, Carlos ; Arceo-Gómez, Gerardo ( December 2021 , AoB PLANTS)

   Boege, Karina (Ed.)

   Abstract Pollinator-mediated competition and facilitation are two important mechanisms mediating co-flowering community assembly. Experimental studies, however, have mostly focused on evaluating outcomes for a single interacting partner at a single location. Studies that evaluate spatial variation in the bidirectional effects between co-flowering species are necessary if we aim to advance our understanding of the processes that mediate species coexistence in diverse co-flowering communities. Here, we examine geographic variation (i.e. at landscape level) in bidirectional pollinator-mediated effects between co-flowering Mimulus guttatus and Delphinium uliginosum. We evaluated effects on pollen transfer dynamics (conspecific and heterospecific pollen deposition) and plant reproductive success. We found evidence of asymmetrical effects (one species is disrupted and the other one is facilitated) but the effects were highly dependent on geographical location. Furthermore, effects on pollen transfer dynamics did not always translate to effects on overall plant reproductive success (i.e. pollen tube growth) highlighting the importance of evaluating effects at multiple stages of the pollination process. Overall, our results provide evidence of a spatial mosaic of pollinator-mediated interactions between co-flowering species and suggest that community assembly processes could result from competition and facilitation acting simultaneously. Our study highlights the importance of experimental studies that evaluate the prevalence of competitive and facilitative interactions in the field, and that expand across a wide geographical context, in order to more fully understand the mechanisms that shape plant communities in nature. 

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5. Bee species exhibit different phenological trajectories in communities of annual flowering plants in the genus Clarkia

   https://doi.org/10.1016/j.ecochg.2021.100031  

   Anderson, Alyssa C. ; James, Aubrie R.M. ; Magno, Elizabeth ; Geber, Monica ( December 2021 , Climate Change Ecology)