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Shrestha M, Tai KC, Dyer AG, Garcia JE, Yang EC, Jentsch A, Wang CN. Flower colour and size-signals vary with altitude and resulting climate on the tropical-subtropical islands of Taiwan. FRONTIERS IN PLANT SCIENCE 2024; 15:1304849. [PMID: 38362451 PMCID: PMC10867191 DOI: 10.3389/fpls.2024.1304849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Accepted: 01/09/2024] [Indexed: 02/17/2024]
Abstract
The diversity of flower colours in nature provides quantifiable evidence for how visitations by colour sensing insect pollinators can drive the evolution of angiosperm visual signalling. Recent research shows that both biotic and abiotic factors may influence flower signalling, and that harsher climate conditions may also promote salient signalling to entice scarcer pollinators to visit. In parallel, a more sophisticated appreciation of the visual task foragers face reveals that bees have a complex visual system that uses achromatic vision when moving fast, whilst colour vision requires slower, more careful inspection of targets. Spectra of 714 native flowering species across Taiwan from sea level to mountainous regions 3,300 m above sea level (a.s.l.) were measured. We modelled how the visual system of key bee pollinators process signals, including flower size. By using phylogenetically informed analyses, we observed that at lower altitudes including foothills and submontane landscapes, there is a significant relationship between colour contrast and achromatic signals. Overall, the frequency of flowers with high colour contrast increases with altitude, whilst flower size decreases. The evidence that flower colour signaling becomes increasingly salient in higher altitude conditions supports that abiotic factors influence pollinator foraging in a way that directly influences how flowering plants need to advertise.
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Affiliation(s)
- Mani Shrestha
- Department of Disturbance Ecology and Vegetation Dynamics, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany
- Department of Life Science, National Taiwan University, Taipei, Taiwan
| | - King-Chun Tai
- Department of Life Science, National Taiwan University, Taipei, Taiwan
- Institute of Ecology and Evolutionary Biology, National Taiwan University, Taipei, Taiwan
| | - Adrian G. Dyer
- Department of Physiology, Monash University, Clayton, VIC, Australia
| | - Jair E. Garcia
- Melbourne Data Analytics Platform, The University of Melbourne, Melbourne, VIC, Australia
| | - En-Cheng Yang
- Department of Entomology, National Taiwan University, Taipei, Taiwan
| | - Anke Jentsch
- Department of Disturbance Ecology and Vegetation Dynamics, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany
| | - Chun-Neng Wang
- Department of Life Science, National Taiwan University, Taipei, Taiwan
- Institute of Ecology and Evolutionary Biology, National Taiwan University, Taipei, Taiwan
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Althiab-Almasaud R, Teyssier E, Chervin C, Johnson MA, Mollet JC. Pollen viability, longevity, and function in angiosperms: key drivers and prospects for improvement. PLANT REPRODUCTION 2023:10.1007/s00497-023-00484-5. [PMID: 37926761 DOI: 10.1007/s00497-023-00484-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 10/19/2023] [Indexed: 11/07/2023]
Abstract
Pollen grains are central to sexual plant reproduction and their viability and longevity/storage are critical for plant physiology, ecology, plant breeding, and many plant product industries. Our goal is to present progress in assessing pollen viability/longevity along with recent advances in our understanding of the intrinsic and environmental factors that determine pollen performance: the capacity of the pollen grain to be stored, germinate, produce a pollen tube, and fertilize the ovule. We review current methods to measure pollen viability, with an eye toward advancing basic research and biotechnological applications. Importantly, we review recent advances in our understanding of how basic aspects of pollen/stigma development, pollen molecular composition, and intra- and intercellular signaling systems interact with the environment to determine pollen performance. Our goal is to point to key questions for future research, especially given that climate change will directly impact pollen viability/longevity. We find that the viability and longevity of pollen are highly sensitive to environmental conditions that affect complex interactions between maternal and paternal tissues and internal pollen physiological events. As pollen viability and longevity are critical factors for food security and adaptation to climate change, we highlight the need to develop further basic research for better understanding the complex molecular mechanisms that modulate pollen viability and applied research on developing new methods to maintain or improve pollen viability and longevity.
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Affiliation(s)
- Rasha Althiab-Almasaud
- Université de Toulouse, LRSV, Toulouse INP, CNRS, UPS, 31326, Castanet-Tolosan, France
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI, 02912, USA
| | - Eve Teyssier
- Université de Toulouse, LRSV, Toulouse INP, CNRS, UPS, 31326, Castanet-Tolosan, France
| | - Christian Chervin
- Université de Toulouse, LRSV, Toulouse INP, CNRS, UPS, 31326, Castanet-Tolosan, France
| | - Mark A Johnson
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI, 02912, USA
| | - Jean-Claude Mollet
- Univ Rouen Normandie, GLYCOMEV UR4358, SFR NORVEGE, Fédération Internationale Normandie-Québec NORSEVE, Carnot I2C, RMT BESTIM, GDR Chemobiologie, IRIB, F-76000, Rouen, France.
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3
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Karban R, Rutkowski D, Murray NA. Flowers that self-shade reduce heat stress and pollen limitation. AMERICAN JOURNAL OF BOTANY 2023; 110:e16109. [PMID: 36416006 DOI: 10.1002/ajb2.16109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Revised: 11/12/2022] [Accepted: 11/15/2022] [Indexed: 06/16/2023]
Abstract
PREMISE Plants are facing increased risk of heat stress with global climate change. Reproductive tissues are particularly heat-sensitive, which can result in lower plant fitness. Floral shading and closure are possible mechanisms to limit heat stress although most previous work on petal orientation has considered adaptations to raise temperatures. We hypothesized that floral shading could reduce temperature and increase reproductive success. METHODS We measured floral temperatures of four species that exhibited intraspecific variation in flower closure (Opuntia ficus-indica, Oenothera elata, Convolvulus arvensis, and Romneya coulteri). We also wired newly opened R. coulteri flowers so that they were either permanently open or permanently closed; controls were not wired. RESULTS Individual flowers of all four species that shaded their pistils were exposed to temperatures 3-8°C lower than those that remained open and unshaded. In our wiring experiment, unencumbered R. coulteri controls were 40% more likely to produce seeds than flowers that were either permanently open or closed. Without added pollen, control flowers produced 2× more seeds than flowers wired open and 8× more than those wired closed. However, pollen addition eliminated the effects of wiring and increased capsule mass and seed production. This effect of pollen addition suggests that pollen limitation was responsible for observed differences in the wiring treatments. Pollinators may prefer control flowers over those that were wired open or closed; petal shading may make flowers cooler and more attractive to pollinators. CONCLUSIONS Petal shading may be a behavior that allows flowers to reduce heat stress and increases their chances of pollination and seed set.
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Affiliation(s)
- Richard Karban
- Department of Entomology and Nematology, University of California, Davis, Davis, CA, 95616, USA
| | - Danielle Rutkowski
- Department of Entomology and Nematology, University of California, Davis, Davis, CA, 95616, USA
| | - Naomi A Murray
- Department of Entomology and Nematology, University of California, Davis, Davis, CA, 95616, USA
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The True Identity of the “Second Pollen Morphology” of Camellia oleifera—Stomium Cells. HORTICULTURAE 2022. [DOI: 10.3390/horticulturae8040347] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Previous studies on Camellia oleifera pollen morphology have indicated dual morphologies, defined as “dimorphism”. However, they were limited to morphological studies at the end of final development and did not elucidate the origin, structure, and function of the second pollen morphology (striate pollen). In this study, the differences between the two “pollen” types were compared by paraffin sections, scanning electron microscopy (SEM), fluorescence microscopy, and in vitro germination. The results clearly showed that the second pollen type was formed by stomium cells of the anther, which is responsible for anther dehiscence. The nucleus and vesicles of the stomium cell were specifically distributed during anther development, which may be related to the formation of the septum, pollen dispersal activity, and the increase in stomium cell count; at the microscopic level, the stomium cell mainly consisted of the cell wall, large vesicles, and nucleus. The large vesicles facilitate the rapid dehydration of stomium cells under suitable conditions for anther dehiscence. Furthermore, studies on other species of the genus Camellia have suggested that the second type of pollen morphology is pseudopollen, which is capable of partaking in deceptive pollination. The present study refuted this theory and suggested that the pseudopollen are stomium cells, whose structure relates to their function. These results provide the basis for further research on C. oleifera pollen physiology toward the improvement of pollination rates with agricultural practices or breeding interventions.
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Koski MH, Galloway LF, Busch JW. Hybrid breakdown is elevated near the historical cores of a species' range. Proc Biol Sci 2022; 289:20220070. [PMID: 35291839 PMCID: PMC8924771 DOI: 10.1098/rspb.2022.0070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
New species form when they become reproductively isolated. A classic model of speciation posits that derived mutations appear in isolated populations and reduce fitness when combined in hybrids. While these Bateson-Dobzhansky-Muller incompatibilities are known to accumulate as populations diverge over time, they may also reflect the amount of standing genetic variation within populations. We analysed the fitness of F2 hybrids in crosses between 24 populations of a plant species (Campanula americana) with broad variation in standing genetic variation and genetic differentiation driven by post-glacial range expansions. Hybrid breakdown varied substantially and was strongest between populations near the historical cores of the species range where within-population genetic diversity was high. Nearly half of the variation in hybrid breakdown was predicted by the combined effects of standing genetic variation within populations, their pairwise genetic differentiation and differences in the climates they inhabit. Hybrid breakdown was enhanced between populations inhabiting distinct climates, likely reflecting local adaptation. Results support that the mutations causing hybrid breakdown, the raw material for speciation, are more common in long-inhabited areas of the species range. Genetic diversity harboured in refugial areas is thus an important source of incompatibilities critical to the speciation process.
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Affiliation(s)
- Matthew H. Koski
- Department of Biological Sciences, Clemson University, 134 Long Hall, Clemson, SC 29634, USA
| | - Laura F. Galloway
- Department of Biology, University of Virginia, PO Box 400328, Charlottesville, VA 22904, USA
| | - Jeremiah W. Busch
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA 99164, USA
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Ahmad S, Chen J, Chen G, Huang J, Zhou Y, Zhao K, Lan S, Liu Z, Peng D. Why Black Flowers? An Extreme Environment and Molecular Perspective of Black Color Accumulation in the Ornamental and Food Crops. FRONTIERS IN PLANT SCIENCE 2022; 13:885176. [PMID: 35498642 PMCID: PMC9047182 DOI: 10.3389/fpls.2022.885176] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Accepted: 03/23/2022] [Indexed: 05/04/2023]
Abstract
Pollinators are attracted to vibrant flower colors. That is why flower color is the key agent to allow successful fruit set in food or ornamental crops. However, black flower color is the least attractive to pollinators, although a number of plant species produce black flowers. Cyanidin-based anthocyanins are thought to be the key agents to induce black color in the ornamental and fruit crops. R2R3-MYB transcription factors (TFs) play key roles for the tissue-specific accumulation of anthocyanin. MYB1 and MYB11 are the key TFs regulating the expression of anthocyanin biosynthesis genes for black color accumulation. Post-transcriptional silencing of flavone synthase II (FNS) gene is the technological method to stimulate the accumulation of cyanidin-based anthocyanins in black cultivars. Type 1 promoter of DvIVS takes the advantage of FNS silencing to produce large amounts of black anthocyanins. Exogenous ethylene application triggers anthocyanin accumulation in the fruit skin at ripening. Environment cues have been the pivotal regulators to allow differential accumulation of anthocyanins to regulate black color. Heat stress is one of the most important environmental stimulus that regulates concentration gradient of anthocyanins in various plant parts, thereby affecting the color pattern of flowers. Stability of black anthocyanins in the extreme environments can save the damage, especially in fruits, caused by abiotic stress. White flowers without anthocyanin face more damages from abiotic stress than dark color flowers. The intensity and pattern of flower color accumulation determine the overall fruit set, thereby controlling crop yield and human food needs. This review paper presents comprehensive knowledge of black flower regulation as affected by high temperature stress, and the molecular regulators of anthocyanin for black color in ornamental and food crops. It also discusses the black color-pollination interaction pattern affected by heat stress for food and ornamental crops.
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Affiliation(s)
- Sagheer Ahmad
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization at College of Landscape Architecture, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Jinliao Chen
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization at College of Landscape Architecture, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Guizhen Chen
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization at College of Landscape Architecture, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Jie Huang
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization at College of Landscape Architecture, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yuzhen Zhou
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization at College of Landscape Architecture, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Kai Zhao
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization at College of Landscape Architecture, Fujian Agriculture and Forestry University, Fuzhou, China
- College of Life Sciences, Fujian Normal University, Fuzhou, China
| | - Siren Lan
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization at College of Landscape Architecture, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Zhongjian Liu
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization at College of Landscape Architecture, Fujian Agriculture and Forestry University, Fuzhou, China
- *Correspondence: Zhongjian Liu,
| | - Donghui Peng
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization at College of Landscape Architecture, Fujian Agriculture and Forestry University, Fuzhou, China
- Donghui Peng,
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7
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Colicchio JM, Hamm LN, Verdonk HE, Kooyers NJ, Blackman BK. Adaptive and nonadaptive causes of heterogeneity in genetic differentiation across the Mimulus guttatus genome. Mol Ecol 2021; 30:6486-6507. [PMID: 34289200 DOI: 10.1111/mec.16087] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 07/08/2021] [Accepted: 07/19/2021] [Indexed: 11/29/2022]
Abstract
Genetic diversity becomes structured among populations over time due to genetic drift and divergent selection. Although population structure is often treated as a uniform underlying factor, recent resequencing studies of wild populations have demonstrated that diversity in many regions of the genome may be structured quite dissimilar to the genome-wide pattern. Here, we explored the adaptive and nonadaptive causes of such genomic heterogeneity using population-level, whole genome resequencing data obtained from annual Mimulus guttatus individuals collected across a rugged environment landscape. We found substantial variation in how genetic differentiation is structured both within and between chromosomes, although, in contrast to other studies, known inversion polymorphisms appear to serve only minor roles in this heterogeneity. In addition, much of the genome can be clustered into eight among-population genetic differentiation patterns, but only two of these clusters are particularly consistent with patterns of isolation by distance. By performing genotype-environment association analysis, we also identified genomic intervals where local adaptation to specific climate factors has accentuated genetic differentiation among populations, and candidate genes in these windows indicate climate adaptation may proceed through changes affecting specialized metabolism, drought resistance, and development. Finally, by integrating our findings with previous studies, we show that multiple aspects of plant reproductive biology may be common targets of balancing selection and that variants historically involved in climate adaptation among populations have probably also fuelled rapid adaptation to microgeographic environmental variation within sites.
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Affiliation(s)
- Jack M Colicchio
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA
| | - Lauren N Hamm
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA
| | - Hannah E Verdonk
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA
| | - Nicholas J Kooyers
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA.,Department of Biology, University of Virginia, Charlottesville, Virginia, USA.,Department of Biology, University of Louisiana, Lafayette, Lafayette, Louisiana, USA
| | - Benjamin K Blackman
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA.,Department of Biology, University of Virginia, Charlottesville, Virginia, USA
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8
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Grossenbacher D, Makler L, McCarthy M, Fraga N. Abiotic Environment Predicts Micro- but Not Macroevolutionary Patterns of Flower Color in Monkeyflowers (Phrymaceae). FRONTIERS IN PLANT SCIENCE 2021; 12:636133. [PMID: 33841464 PMCID: PMC8030662 DOI: 10.3389/fpls.2021.636133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 03/04/2021] [Indexed: 06/12/2023]
Abstract
Anthocyanin pigments are responsible for many of the vivid pink, purple, red, and blue flower colors across angiosperms and frequently vary within and between closely related species. While anthocyanins are well known to influence pollinator attraction, they are also associated with tolerance to abiotic stressors such as extreme temperatures, reduced precipitation, and ultraviolet radiation. Using a comparative approach, we tested whether abiotic variables predict floral anthocyanin in monkeyflowers (Phrymaceae) across western North America. Within two polymorphic species, we found that abiotic variables predicted flower color across their geographic ranges. In Erythranthe discolor, the frequency of pink flowered (anthocyanin producing) individuals was greater in populations with reduced precipitation. In Diplacus mephiticus, the frequency of pink flowered individuals was greater at higher elevations that had reduced precipitation and lower temperatures but less ultraviolet radiation. At the macroevolutionary scale, across two parallel radiations of North American monkeyflowers, species with floral anthocyanins (pink, purple, or red corollas) occupied areas with reduced precipitation in Erythranthe but not Diplacus. However, after accounting for phylogenetic relatedness, we found no evidence for the joint evolution of flower color and environmental affinity in either clade. We conclude that although abiotic stressors may play a role in the evolution of flower color within polymorphic species, we found no evidence that these processes lead to macroevolutionary patterns across monkeyflowers.
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Affiliation(s)
- Dena Grossenbacher
- Department of Biology, California Polytechnic State University, San Luis Obispo, CA, United States
| | - Leah Makler
- Department of Biology, California Polytechnic State University, San Luis Obispo, CA, United States
| | | | - Naomi Fraga
- California Botanic Garden, Claremont, CA, United States
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9
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Koski MH. The role of sensory drive in floral evolution. THE NEW PHYTOLOGIST 2020; 227:1012-1024. [PMID: 32112572 DOI: 10.1111/nph.16510] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 02/17/2020] [Indexed: 05/25/2023]
Abstract
Sensory drive theory posits that the evolution of communication signals is shaped by the sensory systems of receivers and the habitat conditions under which signals are received. It has inspired an enormous body of research, advancing our understanding of signal evolution and speciation in animals. In plants, the extreme diversification of floral signals has fascinated biologists for over a century. While processes involved in sensory drive probably play out in plant-pollinator communication, the theory has not been formally synthesized in this context. However, it has untapped potential to explain mechanisms underlying variation in pollinator preferences across populations, and how environmental conditions impact floral signal transmission and perception. Here I develop a framework of sensory drive for plant-pollinator interactions, identifying similarities and differences from its original conception. I then summarize studies that shed light on how the primary processes of sensory drive - habitat transmission, perceptual tuning, and signal matching - apply to the evolution of floral color and scent. Throughout, I propose research avenues and approaches to assess how sensory drive shapes floral diversity. This framework will be important for explaining patterns of extant floral diversity and examining how altered signaling conditions under global change will impact the evolutionary trajectory of floral traits.
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Affiliation(s)
- Matthew H Koski
- Department of Biological Sciences, Clemson University, Clemson, SC, 29631, USA
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10
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Koski MH, Galloway LF. Geographic Variation in Floral Color and Reflectance Correlates With Temperature and Colonization History. FRONTIERS IN PLANT SCIENCE 2020; 11:991. [PMID: 32714360 PMCID: PMC7340105 DOI: 10.3389/fpls.2020.00991] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 06/17/2020] [Indexed: 05/12/2023]
Abstract
Petal color variation within species is common and may be molded by abiotic or biotic selection pressures, or neutral population structure. For example, darker flowers may be favored in cooler environments because they absorb more solar radiation, elevating the temperature of reproductive structures. Additionally, flower color may evolve to attract the dominant or most efficient pollinator type in a given population. Here, we evaluate geographic variation in petal coloration across the range of Campanula americana in Eastern North America and test whether color covaries with abiotic factors, the pollination community, and genetic structure established through post-glacial expansion. Consistent with other studies, flowers from cooler, higher latitude populations were less reflective across the UV-NIR spectrum than those from warmer populations. Local temperature explained variation in petal reflectance better than the pollinator community or colonization history. Petal color perceived by trichromatic bee pollinators displayed a strong longitudinal pattern but was unassociated with climatic factors and the pollinator community. Instead, pollinator-perceived color was tightly correlated with the geographic distance from C. americana's glacial refugium. In total, abiotic conditions appear to shape large-scale geographic variation in the intensity of petal reflectance while genetic structure is the strongest driver of pollinator-perceived petal coloration. This study highlights the importance of abiotic factors and historical processes associated with range expansion as major evolutionary forces shaping diversity of flower coloration on large geographic scales.
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Affiliation(s)
- Matthew H. Koski
- Department of Biological Sciences, Clemson University, Clemson, SC, United States
- Department of Biology, University of Virginia, Charlottesville, VA, United States
| | - Laura F. Galloway
- Department of Biology, University of Virginia, Charlottesville, VA, United States
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11
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Peach K, Liu JW, Mazer SJ. Climate Predicts UV Floral Pattern Size, Anthocyanin Concentration, and Pollen Performance in Clarkia unguiculata. FRONTIERS IN PLANT SCIENCE 2020; 11:847. [PMID: 32612627 PMCID: PMC7308548 DOI: 10.3389/fpls.2020.00847] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 05/26/2020] [Indexed: 05/25/2023]
Abstract
Given that flower size and pigmentation can mediate plant-pollinator interactions, many studies have focused on pollinator-driven selection on these floral traits. However, abiotic factors such as precipitation, temperature, and solar radiation also contribute to geographic variation in floral color, pattern, and size within multiple species. Several studies have described an ecogeographic pattern within species in which high temperature, high ultraviolet (UV) radiation, low precipitation and/or low latitudes are associated with increased floral anthocyanin production, smaller flowers, and/or larger UV-absorbing floral patterns (nectar guides or bullseyes). However, latitude or elevation is often used as a proxy variable to study variation in floral traits associated with a wide range of climatic variables, making the proximate abiotic drivers of variation difficult to identify. In this study, we tested and corroborated several predictions for how the abiotic environment may directly or indirectly shape geographic patterns of floral color, pattern, and size in Clarkia unguiculata (Onagraceae). This study provides the first report of geographic variation in multispectral floral color and pattern in C. unguiculata, while also providing an experimental test of the putative protective role of UV absorption for pollen performance. We quantified geographic variation among greenhouse-raised populations in UV floral pattern size, mean UV petal reflectance, anthocyanin concentration, and petal area in C. unguiculata across its natural range in California and, using 30 year climate normals for each population, we identified climatic and topographic attributes that are correlated with our focal floral traits. In addition, we examined pollen performance under high and low UV light conditions to detect the protective function (if any) of UV floral patterns in this species. Contrary to our expectations, the nectar guide and the proportion of the petal occupied by the UV nectar guide were largest in low solar UV populations. Estimated floral anthocyanin concentration was highest in populations with high solar UV, which does support our predictions. The size of the UV nectar guide did not affect pollen performance in either of the light treatments used in this study. We conclude that, under the conditions examined here, UV-absorbing floral patterns do not serve a direct "pollen protection" function in C. unguiculata. Our results only partially align with expected ecogeographic patterns in these floral traits, highlighting the need for research in a wider range of taxa in order to detect and interpret broad scale patterns of floral color variation.
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Affiliation(s)
- Kristen Peach
- Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Jasen W. Liu
- Population Biology Graduate Group, University of California, Davis, Davis, CA, United States
| | - Susan J. Mazer
- Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
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12
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Koski MH, Berardi AE, Galloway LF. Pollen colour morphs take different paths to fitness. J Evol Biol 2020; 33:388-400. [PMID: 32012387 DOI: 10.1111/jeb.13599] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2019] [Revised: 12/04/2019] [Accepted: 01/24/2020] [Indexed: 01/23/2023]
Abstract
Colour phenotypes are often involved in communication and are thus under selection by species interactions. However, selection may also act on colour through correlated traits or alternative functions of biochemical pigments. Such forms of selection are instrumental in maintaining petal colour diversity in plants. Pollen colour also varies markedly, but the maintenance of this variation is little understood. In Campanula americana, pollen ranges from white to dark purple, with darker morphs garnering more pollinator visits and exhibiting elevated pollen performance under heat stress. Here, we generate an F2 population segregating for pollen colour and measure correlations with floral traits, pollen attributes and plant-level traits related to fitness. We determine the pigment biochemistry of colour variants and evaluate maternal and paternal fitness of light and dark morphs by crossing within and between morphs. Pollen colour was largely uncorrelated with floral traits (petal colour, size, nectar traits) suggesting it can evolve independently. Darker pollen grains were larger and had higher anthocyanin content (cyanidin and peonidin) which may explain why they outperform light pollen under heat stress. Overall, pollen-related fitness metrics were greater for dark pollen, and dark pollen sires generated seeds with higher germination potential. Conversely, light pollen plants produce 61% more flowers than dark, and 18% more seeds per fruit, suggesting a seed production advantage. Results indicate that light and dark morphs may achieve fitness through different means-dark morphs appear to have a pollen advantage whereas light morphs have an ovule advantage-helping to explain the maintenance of pollen colour variation.
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Affiliation(s)
- Matthew H Koski
- Department of Biological Sciences, Clemson University, Clemson, SC, USA.,Department of Biology, University of Virginia, Charlottesville, VA, USA
| | - Andrea E Berardi
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
| | - Laura F Galloway
- Department of Biology, University of Virginia, Charlottesville, VA, USA
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13
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Borghi M, Perez de Souza L, Yoshida T, Fernie AR. Flowers and climate change: a metabolic perspective. THE NEW PHYTOLOGIST 2019; 224:1425-1441. [PMID: 31257600 DOI: 10.1111/nph.16031] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Accepted: 06/24/2019] [Indexed: 05/18/2023]
Abstract
Adverse climatic conditions at the time of flowering severely hinder crop yields and threaten the interactions between plants and their pollinators. These features depend on a common trait: the metabolism of flowers. In this Viewpoint article, we aim to provide insight into the metabolic changes that occur in flowers in response to changes in climate and emphasize that these changes severely impact the fitness of autogamous and allogamous species, plant-pollinator interactions, and overall ecosystem health. We review the biochemical processes that lead to failure of gamete development and to alterations of color, scent and nectar secretion. Then, making use of open access expression data, we examine the expression of genes that may drive these changes in response to heat and drought. Finally, we present measurements of metabolites from flowers exposed to a heat wave and discuss how the results of this short-term experiment may give rise to misleading conclusions regarding the positive effect of heat on flower fitness. We hope this article draws attention to this often-neglected dynamic and its important consequences.
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Affiliation(s)
- Monica Borghi
- Max-Planck-Institute of Molecular Plant Physiology, 14476, Potsdam-Golm, Germany
| | | | - Takuya Yoshida
- Max-Planck-Institute of Molecular Plant Physiology, 14476, Potsdam-Golm, Germany
| | - Alisdair R Fernie
- Max-Planck-Institute of Molecular Plant Physiology, 14476, Potsdam-Golm, Germany
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van der Kooi CJ, Kevan PG, Koski MH. The thermal ecology of flowers. ANNALS OF BOTANY 2019; 124:343-353. [PMID: 31206146 PMCID: PMC6798827 DOI: 10.1093/aob/mcz073] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 04/27/2019] [Indexed: 05/16/2023]
Abstract
BACKGROUND Obtaining an optimal flower temperature can be crucial for plant reproduction because temperature mediates flower growth and development, pollen and ovule viability, and influences pollinator visitation. The thermal ecology of flowers is an exciting, yet understudied field of plant biology. SCOPE This review focuses on several attributes that modify exogenous heat absorption and retention in flowers. We discuss how flower shape, orientation, heliotropic movements, pubescence, coloration, opening-closing movements and endogenous heating contribute to the thermal balance of flowers. Whenever the data are available, we provide quantitative estimates of how these floral attributes contribute to heating of the flower, and ultimately plant fitness. OUTLOOK Future research should establish form-function relationships between floral phenotypes and temperature, determine the fitness effects of the floral microclimate, and identify broad ecological correlates with heat capture mechanisms.
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Affiliation(s)
- Casper J van der Kooi
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, the Netherlands
| | - Peter G Kevan
- School of Environmental Sciences, University of Guelph, Guelph, Canada
| | - Matthew H Koski
- Department of Biology, University of Virginia, Charlottesville, VA, USA
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Ison JL, Tuan ESL, Koski MH, Whalen JS, Galloway LF. The role of pollinator preference in the maintenance of pollen colour variation. ANNALS OF BOTANY 2019; 123:951-960. [PMID: 30566588 PMCID: PMC6589511 DOI: 10.1093/aob/mcy211] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2018] [Accepted: 11/12/2018] [Indexed: 05/26/2023]
Abstract
BACKGROUND AND AIMS Pollinators often drive the evolution of floral traits, but their capacity to influence the evolution of pollen colour remains unclear. Pollen colour in Campanula americana is variable and displays a longitudinal cline from prevalence of deep purple in western populations to white and light-purple pollen in eastern populations. While selection for thermal tolerance probably underlies darker pollen in the west, factors contributing to the predominance of light pollen in eastern populations and the maintenance of colour variation within populations throughout the range are unknown. Here we examine whether pollinators contribute to the maintenance of pollen colour variation in C. americana. METHODS In a flight cage experiment, we assessed whether Bombus impatiens foragers can use pollen colour as a reward cue. We then established floral arrays that varied in the frequency of white- and purple-pollen plants in two naturally occurring eastern populations. We observed foraging patterns of wild bees, totalling >1100 individual visits. KEY RESULTS We successfully trained B. impatiens to prefer one pollen colour morph. In natural populations, the specialist pollinator, Megachile campanulae, displayed a strong and consistent preference for purple-pollen plants regardless of morph frequency. Megachile also exhibited a bias toward pollen-bearing male-phase flowers, and this bias was more pronounced for purple pollen. The other main pollinators, Bombus spp. and small bees, did not display pollen colour preference. CONCLUSIONS Previous research found that Megachile removes twice as much pollen per visit as other bees and can deplete pollen from natural populations. Taken together, these results suggest that Megachile could reduce the reproductive success of plants with purple pollen, resulting in the prevalence of light-coloured pollen in eastern populations of C. americana. Our research demonstrates that pollinator preferences may play a role in the maintenance of pollen colour variation in natural populations.
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Affiliation(s)
- Jennifer L Ison
- The College of Wooster, Department of Biology, Wooster, OH, USA
| | | | - Matthew H Koski
- University of Virginia, Department of Biology, Charlottesville, VA, USA
| | - Jack S Whalen
- The College of Wooster, Department of Biology, Wooster, OH, USA
| | - Laura F Galloway
- University of Virginia, Department of Biology, Charlottesville, VA, USA
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