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Song B, Chen J, Lev-Yadun S, Niu Y, Gao Y, Ma R, Armbruster WS, Sun H. Multifunctionality of angiosperm floral bracts: a review. Biol Rev Camb Philos Soc 2024; 99:1100-1120. [PMID: 38291834 DOI: 10.1111/brv.13060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 01/02/2024] [Accepted: 01/22/2024] [Indexed: 02/01/2024]
Abstract
Floral bracts (bracteoles, cataphylls) are leaf-like organs that subtend flowers or inflorescences but are of non-floral origin; they occur in a wide diversity of species, representing multiple independent origins, and exhibit great variation in form and function. Although much attention has been paid to bracts over the past 150 years, our understanding of their adaptive significance remains remarkably incomplete. This is because most studies of bract function and evolution focus on only one or a few selective factors. It is widely recognised that bracts experience selection mediated by pollinators, particularly for enhancing pollinator attraction through strong visual, olfactory, or echo-acoustic contrast with the background and through signalling the presence of pollinator rewards, either honestly (providing rewards for pollinators), or deceptively (attraction without reward or even trapping pollinators). However, studies in recent decades have demonstrated that bract evolution is also affected by agents other than pollinators. Bracts can protect flowers, fruits, or seeds from herbivores by displaying warning signals, camouflaging conspicuous reproductive organs, or by providing physical barriers or toxic chemicals. Reviews of published studies show that bracts can also promote seed dispersal and ameliorate the effects of abiotic stressors, such as low temperature, strong ultraviolet radiation, heavy rain, drought, and/or mechanical abrasion, on reproductive organs or for the plants' pollinators. In addition, green bracts and greening of colourful bracts after pollination promote photosynthetic activity, providing substantial carbon (photosynthates) for fruit or seed development, especially late in a plant's life cycle or season, when leaves have started to senesce. A further layer of complexity derives from the fact that the agents of selection driving the evolution of bracts vary between species and even between different developmental stages within a species, and selection by one agent can be reinforced or opposed by other agents. In summary, our survey of the literature reveals that bracts are multifunctional and subject to multiple agents of selection. To understand fully the functional and evolutionary significance of bracts, it is necessary to consider multiple selection agents throughout the life of the plant, using integrative approaches to data collection and analysis.
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Affiliation(s)
- Bo Song
- Key Laboratory for Plant Diversity and Biogeography of East Asia/Yunnan Key Laboratory for Integrative Conservation of Plant Species with Extremely Small Populations, Kunming Institute of Botany, Chinese Academy of Sciences, 132 Lanhei Road, Kunming, 650201, China
| | - Jiaqi Chen
- Key Laboratory for Plant Diversity and Biogeography of East Asia/Yunnan Key Laboratory for Integrative Conservation of Plant Species with Extremely Small Populations, Kunming Institute of Botany, Chinese Academy of Sciences, 132 Lanhei Road, Kunming, 650201, China
- School of Life Sciences, Yunnan University, Huannan Road, East of University Town, Chenggong New Area, Kunming, 650500, China
| | - Simcha Lev-Yadun
- Department of Biology and Environment, Faculty of Natural Sciences, University of Haifa at Oranim, Kiryat Tiv'on, 36006, Israel
| | - Yang Niu
- Key Laboratory for Plant Diversity and Biogeography of East Asia/Yunnan Key Laboratory for Integrative Conservation of Plant Species with Extremely Small Populations, Kunming Institute of Botany, Chinese Academy of Sciences, 132 Lanhei Road, Kunming, 650201, China
| | - Yongqian Gao
- Yunnan Forestry Technological College, 1 Jindian, Kunming, 650224, China
| | - Rong Ma
- Key Laboratory for Plant Diversity and Biogeography of East Asia/Yunnan Key Laboratory for Integrative Conservation of Plant Species with Extremely Small Populations, Kunming Institute of Botany, Chinese Academy of Sciences, 132 Lanhei Road, Kunming, 650201, China
| | - W Scott Armbruster
- School of Biological Sciences, University of Portsmouth, King Henry Building, King Henry I Street, Portsmouth, PO1 2DY, UK
- Institute of Arctic Biology, University of Alaska, PO Box 757000, Fairbanks, AK, 99775, USA
| | - Hang Sun
- Key Laboratory for Plant Diversity and Biogeography of East Asia/Yunnan Key Laboratory for Integrative Conservation of Plant Species with Extremely Small Populations, Kunming Institute of Botany, Chinese Academy of Sciences, 132 Lanhei Road, Kunming, 650201, China
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Pertierra LR, Martínez PA, Rubalcaba JG, Richardson DM, Olalla-Tárraga MA. Contrasting patterns in phylogenetic and biogeographic factories of invasive grasses (Poaceae) across the globe. NPJ BIODIVERSITY 2023; 2:11. [PMID: 39242679 PMCID: PMC11332090 DOI: 10.1038/s44185-023-00016-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 04/05/2023] [Indexed: 09/09/2024]
Abstract
Grasses (Family Poaceae) are among the most successful invasive plants in the world. Here we evaluate phylogenetic and biogeographic patterns of emergence of naturalized and invasive species among grasses globally. In our data, circa 19% of the grasses are currently catalogued as invasive and almost 38% are listed as naturalized; these are among the highest ratios for single families of organisms. Remarkably, most tribes of grasses contain numerous naturalized and invasive species, suggesting that the invasion success is rooted broadly in ancestral traits in the Poaceae. Moreover, the probability of invasiveness is positively related to the diversification rates in the family also suggesting a link with recent radiation events. The phylogenetic distribution of the invasive condition is neither strongly conserved nor purely random. Phylogenetic clumping levels also vary between Poaceae subclades. We postulate that this diffuse clumping could be partially attributed to the expression of labile traits that contribute to species invasiveness. In addition, floristic regions (biomes and biogeographic realms) have different proportions of invasive species, with the temperate Palearctic region having the highest ratio of invasive vs. non-invasive species. The phylodiversity of aliens across regions is also variable in space. Comparison of alien phylodiversity levels across biogeographic realms and biomes reveals regions producing highly restricted invasive lineages and others where the diversity of aliens exported is no different from global mean diversity levels in grasses. Elucidating the evolutionary patterns and drivers of invasiveness is useful for understanding and managing invasions, with the low phylogenetic structure of alien grasses warning of their overall high invasiveness potential.
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Affiliation(s)
- Luis R Pertierra
- BIOMA Lab, Departamento de Biología, Geología, Química y Física Inorgánica, Universidad Rey Juan Carlos, Móstoles, Spain.
- Department of Plant & Soil Sciences, University of Pretoria, Pretoria, South Africa.
| | - Pablo A Martínez
- BIOMA Lab, Departamento de Biología, Geología, Química y Física Inorgánica, Universidad Rey Juan Carlos, Móstoles, Spain
- PIBi Lab, Departamento de Biologia, Universidade Federal do Sergipe, São Cristovão, Brazil
| | - Juan G Rubalcaba
- BIOMA Lab, Departamento de Biología, Geología, Química y Física Inorgánica, Universidad Rey Juan Carlos, Móstoles, Spain
| | - David M Richardson
- Department of Botany & Zoology, Centre for Invasion Biology, Stellenbosch University, Stellenbosch, South Africa
- Department of Invasion Ecology, Institute of Botany, Czech Academy of Sciences, Průhonice, Czech Republic
| | - Miguel A Olalla-Tárraga
- BIOMA Lab, Departamento de Biología, Geología, Química y Física Inorgánica, Universidad Rey Juan Carlos, Móstoles, Spain
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Hopkins JR, Huffman JM, Jones NJ, Platt WJ, Sikes BA. Pyrophilic Plants Respond to Postfire Soil Conditions in a Frequently Burned Longleaf Pine Savanna. Am Nat 2023; 201:389-403. [PMID: 36848518 DOI: 10.1086/722569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AbstractFire-plant feedbacks engineer recurrent fires in pyrophilic ecosystems like savannas. The mechanisms sustaining these feedbacks may be related to plant adaptations that trigger rapid responses to fire's effects on soil. Plants adapted for high fire frequencies should quickly regrow, flower, and produce seeds that mature rapidly and disperse postfire. We hypothesized that the offspring of such plants would germinate and grow rapidly, responding to fire-generated changes in soil nutrients and biota. We conducted an experiment using longleaf pine savanna plants that were paired on the basis of differences in reproduction and survival under annual ("more" pyrophilic) versus less frequent ("less" pyrophilic) fire regimes. Seeds were planted in different soil inoculations from experimental fires of varying severity. The more pyrophilic species displayed high germination rates followed by species-specific rapid growth responses to soil location and fire severity effects on soils. In contrast, the less pyrophilic species had lower germination rates that were not responsive to soil treatments. This suggests that rapid germination and growth constitute adaptations to frequent fires and that plants respond differently to fire severity effects on soil abiotic factors and microbes. Furthermore, variable plant responses to postfire soils may influence plant community diversity and fire-fuel feedbacks in pyrophilic ecosystems.
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Lamont BB. Grass species with smoke-released seed dormancy: A response to climate and fire regime but not photosynthetic pathway. PLANT BIOLOGY (STUTTGART, GERMANY) 2023; 25:24-31. [PMID: 36250211 PMCID: PMC10099466 DOI: 10.1111/plb.13479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 10/10/2022] [Indexed: 06/16/2023]
Abstract
Both C3 and C4 photosynthetic pathways and smoke-released seed dormancy occur among grasses. C4 species evolved from C3 species as seasonality and fire frequency increased and might therefore imply that their smoke sensitivity increased. I searched the worldwide literature for reports on germination responses among grasses, whose photosynthetic pathway was known, to treatment by smoke. Data were obtained for 217 species and 126 genera. While subfamilies tended to be C3 (Pooideae), C4 (Chloridoideae) or a mixture (Panicoideae), a beneficial smoke response was independent of their photosynthetic pathway. The only exceptions were Danthonioideae (C3, non-smoke responsive) and Triodia (C4, smoke responsive). One third of both C3 and C4 genera were smoke responsive. Even within genera, 90% of species showed contrasting smoke responses, confirming that smoke sensitivity is rarely taxonomically constrained. Data on photosynthetic pathway, climate, fire regime and vegetation were compiled for 15 regions that formed four distinct groups: 1) In warm climates with aseasonal rainfall, C4 grasses are moderately better represented, with crown fires and limited smoke responses. 2) In cool regions, most species are C3, with surface-crown fires and lack smoke responses. 3) In warm regions with summer rain (savannas), most species are C4, with surface fires and lack smoke responses. 4) In Mediterranean-climate regions with summer drought, most species are C3, with crown fires and smoke-released dormancy. Thus, even though C3 and C4 grasses are equally capable of expressing smoke sensitivity, their response depends on the region's climate and fire regime that also dictate which photosynthetic pathway dominates.
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Affiliation(s)
- B. B. Lamont
- Ecology Section, School of Molecular and Life SciencesCurtin UniversityPerthWAAustralia
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Petersen KB, Kellogg EA. Diverse ecological functions and the convergent evolution of grass awns. AMERICAN JOURNAL OF BOTANY 2022; 109:1331-1345. [PMID: 36048829 PMCID: PMC9828495 DOI: 10.1002/ajb2.16060] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 08/23/2022] [Accepted: 08/25/2022] [Indexed: 06/15/2023]
Abstract
The awn of grasses is a long, conspicuous outgrowth of the floral bracts in a grass spikelet. It is known to impact agricultural yield, but we know little about its broader ecological function, nor the selective forces that lead to its evolution. Grass awns are phenotypically diverse across the extant ~12,000 species of Poaceae. Awns have been lost and gained repeatedly over evolutionary time, between and within lineages, suggesting that they could be under selection and might provide adaptive benefit in some environments. Despite the phylogenetic context, we know of no studies that have tested whether the origin of awns correlates with putative selective forces on their form and function. Presence or absence of awns is not plastic; rather, heritability is high. The awns of grasses often are suggested as adaptations for dispersal, and most experimental work has been aimed at testing this hypothesis. Proposed dispersal functions include soil burial, epizoochory, and aerial orientation. Awns may also protect the seed from drought, herbivores, or fire by helping it become buried in soil. We do not fully understand the fitness or nutrient costs of awn production, but in some species awns function in photosynthesis, providing carbon to the seed. Here we show that awns likely provide an adaptive advantage, but argue that studies on awn function have lacked critical phylogenetic information to demonstrate adaptive convergent evolution, are taxonomically biased, and often lack clear alternative hypotheses.
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Simpson KJ, Archibald S, Osborne CP. Savanna fire regimes depend on grass trait diversity. Trends Ecol Evol 2022; 37:749-758. [PMID: 35577616 DOI: 10.1016/j.tree.2022.04.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 04/14/2022] [Accepted: 04/20/2022] [Indexed: 11/17/2022]
Abstract
Grasses fuel most fires on Earth and strongly influence local fire behaviour through traits that determine how flammable they are. Therefore, grass communities that differ in their species and trait compositions give rise to significant spatial variation in savanna fire regimes across the world, which cannot be otherwise explained. Likewise, fire regimes are continuously modified by alterations to savanna grass community traits, through species introductions and climatic changes. However, current representation of grassy fuels in global fire models misses important variation and therefore limits predictive power. The inclusion of grass trait diversity in models, using remotely sensed trait proxies, for example, will greatly improve our ability to understand and project savanna fires and their roles in the Earth system.
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Affiliation(s)
- Kimberley J Simpson
- Plants, Photosynthesis and Soil, School of Biosciences, University of Sheffield, Sheffield, UK; Department of Botany, Rhodes University, Makhanda, South Africa.
| | - Sally Archibald
- Centre for African Ecology, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Colin P Osborne
- Plants, Photosynthesis and Soil, School of Biosciences, University of Sheffield, Sheffield, UK.
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Teixeira J, Souza L, Le Stradic S, Fidelis A. Fire promotes functional plant diversity and modifies soil carbon dynamics in tropical savanna. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 812:152317. [PMID: 34914993 DOI: 10.1016/j.scitotenv.2021.152317] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 12/07/2021] [Accepted: 12/07/2021] [Indexed: 06/14/2023]
Abstract
Fire is an evolutionary environmental filter in tropical savanna ecosystems altering functional diversity and associated C pools in the biosphere and fluxes between the atmosphere and biosphere. Therefore, alterations in fire regimes (e.g. fire exclusion) will strongly influence ecosystem processes and associated dynamics. In those ecosystems C dynamics and functions are underestimated by the fire-induced offset between C output and input. To determine how fire shapes ecosystem C pools and fluxes in an open savanna across recently burned and fire excluded areas, we measured the following metrics: (I) plant diversity including taxonomic (i.e. richness, evenness) and plant functional diversity (i.e. functional diversity, functional richness, functional dispersion and community weighted means); (II) structure (i.e. above- and below-ground biomass, litter accumulation); and (III) functions related to C balance (i.e. net ecosystem carbon dioxide (CO2) exchange (NEE), ecosystem transpiration (ET), soil respiration (soil CO2 efflux), ecosystem water use efficiency (eWUE) and total soil organic C (SOC). We found that fire promoted aboveground live and belowground biomass, including belowground organs, coarse and fine root biomass and contributed to higher biomass allocation belowground. Fire also increased both functional diversity and dispersion. NEE and total SOC were higher in burned plots compared to fire-excluded plots whereas soil respiration recorded lower values in burned areas. Both ET and eWUE were not affected by fire. Fire strongly favored functional diversity, fine root and belowground organ biomass in piecewise SEM models but the role of both functional diversity and ecosystem structure to mediate the effect of fire on ecosystem functions remain unclear. Fire regime will impact C balance, and fire exclusion may lead to lower C input in open savanna ecosystems.
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Affiliation(s)
- Juliana Teixeira
- Laboratory of Vegetation Ecology, Department of Biodiversity, Bioscience Institute, São Paulo State University (Unesp), Av. 24 A 1515, 13506-900 Rio Claro, SP, Brazil; Oklahoma Biological Survey & Department of Microbiology and Plant Biology, the University of Oklahoma, 111 E. Chesapeake Street, Norman, OK 73019-0390, USA.
| | - Lara Souza
- Oklahoma Biological Survey & Department of Microbiology and Plant Biology, the University of Oklahoma, 111 E. Chesapeake Street, Norman, OK 73019-0390, USA
| | - Soizig Le Stradic
- Chair of Restoration Ecology, Department of Life Science Systems, Technical University of Munich, Emil-Ramann-Str. 6, 85354 Freising, Germany
| | - Alessandra Fidelis
- Laboratory of Vegetation Ecology, Department of Biodiversity, Bioscience Institute, São Paulo State University (Unesp), Av. 24 A 1515, 13506-900 Rio Claro, SP, Brazil
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Di B, Firn J, Buckley YM, Lomas K, Pausas JG, Smith AL. The impact of roadside burning on genetic diversity in a high‐biomass invasive grass. Evol Appl 2022; 15:790-803. [PMID: 35603028 PMCID: PMC9108304 DOI: 10.1111/eva.13369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 12/06/2021] [Accepted: 02/23/2022] [Indexed: 11/28/2022] Open
Affiliation(s)
- Binyin Di
- School of Agriculture and Food Sciences University of Queensland Gatton 4343 Australia
| | - Jennifer Firn
- School of Biology & Environmental Science Queensland University of Technology Brisbane 4000 Australia
| | - Yvonne M. Buckley
- School of Natural Sciences, Zoology Trinity College Dublin The University of Dublin Dublin 2 Ireland
| | - Kate Lomas
- School of Biology & Environmental Science Queensland University of Technology Brisbane 4000 Australia
| | - Juli G. Pausas
- Centro de Investigaciones sobre Desertificación (CIDE‐CSIC) 46113 Montcada, Valencia Spain
| | - Annabel L. Smith
- School of Agriculture and Food Sciences University of Queensland Gatton 4343 Australia
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Day NJ. When do grasses resprout after fire? THE NEW PHYTOLOGIST 2021; 230:406-407. [PMID: 33729594 DOI: 10.1111/nph.17275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Affiliation(s)
- Nicola J Day
- School of Biological Sciences, Victoria University of Wellington, Aotearoa, 6012, New Zealand
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Jardine EC, Thomas GH, Osborne CP. Traits explain sorting of C 4 grasses along a global precipitation gradient. Ecol Evol 2021; 11:2669-2680. [PMID: 33767828 PMCID: PMC7981197 DOI: 10.1002/ece3.7223] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 12/06/2020] [Accepted: 12/26/2020] [Indexed: 11/29/2022] Open
Abstract
Species distributions are closely associated with moisture availability, but the underlying mechanisms remain unresolved. Drought relations are especially important for plants such as C4 grasses that dominate seasonally dry ecosystems. Here, we test the hypothesis that C4 grass species sampled across global precipitation gradients show variation in survival under drought that can be explained by their traits.Our experiment subjected 18 C4 grass species to a lethal drought under controlled environmental conditions. The number of days until death was measured, along with root traits, senescence, and aspects of hydraulic function.We identified two strategies: Drought-avoiding species that stayed green as the water potential declined and drought-tolerating species that senesced more quickly but could extend survival via drought-tolerant meristems.Plants that stay-green for longer occupied drier habitats and had the longest survival under drought, facilitated by narrow root diameter and isohydric stomatal behavior. Plants that senesced quickly had thicker roots, an anisohydric strategy, and occupied wetter habitats.Global distributions of C4 grasses can be predicted by variation in rates of senescence, meristem survival, root traits, and stomatal strategy, showing the value of these traits for understanding plant distributions in relation to climate.
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Affiliation(s)
- Emma C. Jardine
- Department of Animal and Plant SciencesUniversity of SheffieldSheffieldUK
| | - Gavin H. Thomas
- Department of Animal and Plant SciencesUniversity of SheffieldSheffieldUK
| | - Colin P. Osborne
- Department of Animal and Plant SciencesUniversity of SheffieldSheffieldUK
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