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Gallagher MK, Campbell DR. Shifts in water availability mediate plant-pollinator interactions. THE NEW PHYTOLOGIST 2017; 215:792-802. [PMID: 28517023 DOI: 10.1111/nph.14602] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 04/11/2017] [Indexed: 05/22/2023]
Abstract
Altered precipitation patterns associated with anthropogenic climate change are expected to have many effects on plants and insect pollinators, but it is unknown if effects on pollination are mediated by changes in water availability. We tested the hypothesis that impacts of climate on plant-pollinator interactions operate through changes in water availability, and specifically that such effects occur through alteration of floral attractants. We manipulated water availability in two naturally occurring Mertensia ciliata (Boraginaceae) populations using water addition, water reduction and control plots and measured effects on vegetative and floral traits, pollinator visitation and seed set. While most floral trait values, including corolla size and nectar, increased linearly with increasing water availability, in this bumblebee-pollinated species, pollinator visitation peaked at intermediate water levels. Visitation also peaked at an intermediate corolla length, while its relationship to corolla width varied across sites. Seed set, however, increased linearly with water. These results demonstrate the potential for changes in water availability to impact plant-pollinator interactions through pollinator responses to differences in floral attractants, and that the effects of water on pollinator visitation can be nonlinear. Plant responses to changes in resource availability may be an important mechanism by which climate change will affect species interactions.
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Affiliation(s)
- M Kate Gallagher
- Department of Ecology and Evolutionary Biology, University of California, 321 Steinhaus Hall, Irvine, CA, 92697-2525, USA
- Rocky Mountain Biological Laboratory, Crested Butte, CO, 81224, USA
| | - Diane R Campbell
- Department of Ecology and Evolutionary Biology, University of California, 321 Steinhaus Hall, Irvine, CA, 92697-2525, USA
- Rocky Mountain Biological Laboratory, Crested Butte, CO, 81224, USA
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Varga S, Soulsbury CD. Sexually-trimorphic interactions with colour polymorphism determine nectar quality in a herbaceous perennial. Sci Rep 2017; 7:45838. [PMID: 28374829 PMCID: PMC5379179 DOI: 10.1038/srep45838] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 03/06/2017] [Indexed: 11/09/2022] Open
Abstract
Amongst gynodioecious plant breeding systems, there can exist intermediate morphs with a reduction in their male function (i.e. reduced number of functional anthers). Along with this sexual trimorphism, plants can also show floral colour polymorphism. Such intricate mixtures of phenotypes within a species may have complex effects on floral rewards. Floral rewards are known to vary between sexually dimorphic species and to a lesser extent between colour morphs. However, the interactive effect of sexual trimorphism and colour polymorphism is unexplored. We measured nectar's sugar content in the sexually trimorphic Geranium sylvaticum, a gynodioecious plant with a light/dark floral polymorphism. We found that nectar reward differed across genders and colour morphs. Results were not however consistent within the three genders; dark female and hermaphrodite flowers had higher sugar content than light morphs, whereas intermediate flowers did not. As expected, females and hermaphrodites had different nectar reward, with intermediate morphs being midway between the other genders. In intermediates, the sugar content was not related to the number of functional stamens. We show for the first time the existence of sex-specific differences between flower gender and colour morphs in nectar rewards. Our results demonstrate the importance of considering multiple and conflicting selection pressures to explain rewards.
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Affiliation(s)
- Sandra Varga
- School of Life Sciences, University of Lincoln, Joseph Banks Laboratories, Lincoln LN6 7TS, UK
| | - Carl D. Soulsbury
- School of Life Sciences, University of Lincoln, Joseph Banks Laboratories, Lincoln LN6 7TS, UK
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53
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López-Jurado J, Balao F, Mateos-Naranjo E. Deciphering the ecophysiological traits involved during water stress acclimation and recovery of the threatened wild carnation, Dianthus inoxianus. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2016; 109:397-405. [PMID: 27814569 DOI: 10.1016/j.plaphy.2016.10.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 10/04/2016] [Accepted: 10/25/2016] [Indexed: 06/06/2023]
Abstract
Dianthus inoxianus is an endangered species endemic from a small littoral area in the SW Spain, with an unusual flowering season under the adverse conditions of dry Mediterranean summer. A greenhouse experiment was designed to assess the physiological traits involved in drought acclimation and recovery of 3-month-old plants. The evolution of plant water status, leaf gas exchange, chlorophyll fluorescence, photosynthetic pigments concentrations and a quantitative analysis of photosynthesis limitations were followed during water stress and re-watering. Our results indicated that the plant water status, Ψw and RWC, only decreased at the end of the drought period (18th day), together with the net photosynthetic rate, AN. Photosynthetic impair was mainly caused by diffusional limitations (SL and MCL) of CO2, as indicated the joint and marked decrease of gs, gm and Ci during drought period, while Vc,max did not vary. After rewatering, leaf water status recovered faster than photosynthetic one, reaching control values on day 1 after recovery, while AN, gm and Ci took 7 days. Additionally, gs showed the slowest recovery taking 15 days, but gs decrease was enough to keep Ψw and RWC at constant values throughout the experiment. Results suggest a high tolerance and recovery of D. inoxianus from severe drought periods. This drought tolerance was also reflected in the stability of its photochemical apparatus and pigments concentrations, as indicated the constant values of Fv/Fm, ФPSII and pigments concentrations through experimental period. However, prolonged drought events due to global climate change could negatively affect the physiological mechanisms of this species.
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Affiliation(s)
- Javier López-Jurado
- Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Apdo. 1095, 41080 Sevilla, Spain.
| | - Francisco Balao
- Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Apdo. 1095, 41080 Sevilla, Spain
| | - Enrique Mateos-Naranjo
- Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Apdo. 1095, 41080 Sevilla, Spain
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54
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Graham CH, Supp SR, Powers DR, Beck P, Lim MCW, Shankar A, Cormier T, Goetz S, Wethington SM. Winter conditions influence biological responses of migrating hummingbirds. Ecosphere 2016. [DOI: 10.1002/ecs2.1470] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Affiliation(s)
- Catherine H. Graham
- Ecology and Evolution Department Stony Brook University Stony Brook New York 11794 USA
| | - Sarah R. Supp
- Ecology and Evolution Department Stony Brook University Stony Brook New York 11794 USA
| | - Donald R. Powers
- Biology Department George Fox University Newberg Oregon 97132 USA
| | - Pieter Beck
- Woods Hole Research Center Falmouth Massachusetts 02540 USA
| | - Marisa C. W. Lim
- Ecology and Evolution Department Stony Brook University Stony Brook New York 11794 USA
| | - Anusha Shankar
- Ecology and Evolution Department Stony Brook University Stony Brook New York 11794 USA
| | - Tina Cormier
- Woods Hole Research Center Falmouth Massachusetts 02540 USA
| | - Scott Goetz
- Woods Hole Research Center Falmouth Massachusetts 02540 USA
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Prieto-Benítez S, Dötterl S, Giménez-Benavides L. Circadian rhythm of a Silene species favours nocturnal pollination and constrains diurnal visitation. ANNALS OF BOTANY 2016; 118:907-918. [PMID: 27451986 PMCID: PMC5055817 DOI: 10.1093/aob/mcw136] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 04/24/2016] [Accepted: 05/31/2016] [Indexed: 05/24/2023]
Abstract
Background and Aims Traits related to flower advertisement and reward sometimes vary in a circadian way, reflecting phenotypic specialization. However, specialized flowers are not necessarily restricted to specialized pollinators. This is the case of most Silene species, typically associated with diurnal or nocturnal syndromes of pollination but usually showing complex suites of pollinators. Methods A Silene species with mixed floral features between diurnal and nocturnal syndromes was used to test how petal opening, nectar production, scent emission and pollination success correlate in a circadian rhythm, and whether this is influenced by environmental conditions. The effect of diurnal and nocturnal visitation rates on plant reproductive success is also explored in three populations, including the effect of the pollinating seed predator Hadena sancta. Key Results The result showed that repeated petal opening at dusk was correlated with nectar secretion and higher scent production during the night. However, depending on environmental conditions, petals remain opened for a while in the morning, when nectar and pollen still were available. Pollen deposition was similarly effective at night and in the morning, but less effective in the afternoon. These results were consistent with field studies. Conclusions The circadian rhythm regulating floral attractiveness and reward in S. colorata is predominantly adapted to nocturnal flower visitors. However, favourable environmental conditions lengthen the optimal daily period of flower attraction and pollination towards morning. This allows the complementarity of day and night pollination. Diurnal pollination may help to compensate the plant reproductive success when nocturnal pollinators are scarce and when the net outcome of H. sancta shifts from mutualism to parasitism. These results suggest a functional mechanism explaining why the supposed nocturnal syndrome of many Silene species does not successfully predict their pollinator guilds.
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Affiliation(s)
- Samuel Prieto-Benítez
- Departamento de Biología y Geología, Física y Química Inorgánica, Universidad Rey Juan Carlos-ESCET, C/ Tulipán, s/n. 28933-Móstoles, Madrid, Spain
| | - Stefan Dötterl
- Department of Ecology & Evolution, Plant Ecology, University of Salzburg, Hellbrunnerstr. 34, 5020 Salzburg, Austria
| | - Luis Giménez-Benavides
- Departamento de Biología y Geología, Física y Química Inorgánica, Universidad Rey Juan Carlos-ESCET, C/ Tulipán, s/n. 28933-Móstoles, Madrid, Spain
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56
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McKay AF, Ezenwa VO, Altizer S. Consequences of Food Restriction for Immune Defense, Parasite Infection, and Fitness in Monarch Butterflies. Physiol Biochem Zool 2016; 89:389-401. [DOI: 10.1086/687989] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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57
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Ferris KG, Barnett LL, Blackman BK, Willis JH. The genetic architecture of local adaptation and reproductive isolation in sympatry within the Mimulus guttatus species complex. Mol Ecol 2016; 26:208-224. [PMID: 27439150 DOI: 10.1111/mec.13763] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 06/30/2016] [Accepted: 07/05/2016] [Indexed: 01/05/2023]
Abstract
The genetic architecture of local adaptation has been of central interest to evolutionary biologists since the modern synthesis. In addition to classic theory on the effect size of adaptive mutations by Fisher, Kimura and Orr, recent theory addresses the genetic architecture of local adaptation in the face of ongoing gene flow. This theory predicts that with substantial gene flow between populations local adaptation should proceed primarily through mutations of large effect or tightly linked clusters of smaller effect loci. In this study, we investigate the genetic architecture of divergence in flowering time, mating system-related traits, and leaf shape between Mimulus laciniatus and a sympatric population of its close relative M. guttatus. These three traits are probably involved in M. laciniatus' adaptation to a dry, exposed granite outcrop environment. Flowering time and mating system differences are also reproductive isolating barriers making them 'magic traits'. Phenotypic hybrids in this population provide evidence of recent gene flow. Using next-generation sequencing, we generate dense SNP markers across the genome and map quantitative trait loci (QTLs) involved in flowering time, flower size and leaf shape. We find that interspecific divergence in all three traits is due to few QTL of large effect including a highly pleiotropic QTL on chromosome 8. This QTL region contains the pleiotropic candidate gene TCP4 and is involved in ecologically important phenotypes in other Mimulus species. Our results are consistent with theory, indicating that local adaptation and reproductive isolation with gene flow should be due to few loci with large and pleiotropic effects.
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Affiliation(s)
- Kathleen G Ferris
- Department of Biology, Duke University, 125 Science Drive, Durham, NC, 27705, USA
| | - Laryssa L Barnett
- Department of Biology, Duke University, 125 Science Drive, Durham, NC, 27705, USA
| | - Benjamin K Blackman
- Department of Biology, University of Virginia, 485 McCormick Road, Charlottesville, VA, 22904, USA
| | - John H Willis
- Department of Biology, Duke University, 125 Science Drive, Durham, NC, 27705, USA
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58
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Affiliation(s)
- Nickolas M. Waser
- Rocky Mountain Biological Laboratory; P. O. Box 519 Crested Butte Colorado 81224 USA
- School of Natural Resources and the Environment; The University of Arizona; Tucson Arizona 85721 USA
| | - Mary V. Price
- Rocky Mountain Biological Laboratory; P. O. Box 519 Crested Butte Colorado 81224 USA
- School of Natural Resources and the Environment; The University of Arizona; Tucson Arizona 85721 USA
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59
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Martielly SDS, Lucin eacute ia DSS, Carlos ASC, Fabio PG, Larissa CEADBC, Rosilene ADO, Delmira DCS. Effects of water deficit on morphophysiology, productivity and chemical composition of Ocimum africanum Lour (Lamiaceae). ACTA ACUST UNITED AC 2016. [DOI: 10.5897/ajar2015.10248] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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60
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Gezon ZJ, Inouye DW, Irwin RE. Phenological change in a spring ephemeral: implications for pollination and plant reproduction. GLOBAL CHANGE BIOLOGY 2016; 22:1779-1793. [PMID: 26833694 DOI: 10.1111/gcb.13209] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 12/08/2015] [Accepted: 12/14/2015] [Indexed: 06/05/2023]
Abstract
Climate change has had numerous ecological effects, including species range shifts and altered phenology. Altering flowering phenology often affects plant reproduction, but the mechanisms behind these changes are not well-understood. To investigate why altering flowering phenology affects plant reproduction, we manipulated flowering phenology of the spring herb Claytonia lanceolata (Portulacaceae) using two methods: in 2011-2013 by altering snow pack (snow-removal vs. control treatments), and in 2013 by inducing flowering in a greenhouse before placing plants in experimental outdoor arrays (early, control, and late treatments). We measured flowering phenology, pollinator visitation, plant reproduction (fruit and seed set), and pollen limitation. Flowering occurred approx. 10 days earlier in snow-removal than control plots during all years of snow manipulation. Pollinator visitation patterns and strength of pollen limitation varied with snow treatments, and among years. Plants in the snow removal treatment were more likely to experience frost damage, and frost-damaged plants suffered low reproduction despite lack of pollen limitation. Plants in the snow removal treatment that escaped frost damage had higher pollinator visitation rates and reproduction than controls. The results of the array experiment supported the results of the snow manipulations. Plants in the early and late treatments suffered very low reproduction due either to severe frost damage (early treatment) or low pollinator visitation (late treatment) relative to control plants. Thus, plants face tradeoffs with advanced flowering time. While early-flowering plants can reap the benefits of enhanced pollination services, they do so at the cost of increased susceptibility to frost damage that can overwhelm any benefit of flowering early. In contrast, delayed flowering results in dramatic reductions in plant reproduction through reduced pollination. Our results suggest that climate change may constrain the success of early-flowering plants not through plant-pollinator mismatch but through the direct impacts of extreme environmental conditions.
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Affiliation(s)
- Zachariah J Gezon
- Department of Biological Sciences, Dartmouth College, 78 College St, Hanover, NH, 03755, USA
- Rocky Mountain Biological Laboratory, Crested Butte, CO, 81224, USA
- Florida Museum of Natural History, Gainesville, FL, 32611, USA
| | - David W Inouye
- Rocky Mountain Biological Laboratory, Crested Butte, CO, 81224, USA
- Department of Biology, University of Maryland, College Park, MD, 20742, USA
| | - Rebecca E Irwin
- Department of Biological Sciences, Dartmouth College, 78 College St, Hanover, NH, 03755, USA
- Rocky Mountain Biological Laboratory, Crested Butte, CO, 81224, USA
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61
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Burkle LA, Runyon JB. Drought and leaf herbivory influence floral volatiles and pollinator attraction. GLOBAL CHANGE BIOLOGY 2016; 22:1644-54. [PMID: 26546275 DOI: 10.1111/gcb.13149] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 10/11/2015] [Accepted: 10/21/2015] [Indexed: 05/10/2023]
Abstract
The effects of climate change on species interactions are poorly understood. Investigating the mechanisms by which species interactions may shift under altered environmental conditions will help form a more predictive understanding of such shifts. In particular, components of climate change have the potential to strongly influence floral volatile organic compounds (VOCs) and, in turn, plant-pollinator interactions. In this study, we experimentally manipulated drought and herbivory for four forb species to determine effects of these treatments and their interactions on (1) visual plant traits traditionally associated with pollinator attraction, (2) floral VOCs, and (3) the visitation rates and community composition of pollinators. For all forbs tested, experimental drought universally reduced flower size and floral display, but there were species-specific effects of drought on volatile emissions per flower, the composition of compounds produced, and subsequent pollinator visitation rates. Moreover, the community of pollinating visitors was influenced by drought across forb species (i.e. some pollinator species were deterred by drought while others were attracted). Together, these results indicate that VOCs may provide more nuanced information to potential floral visitors and may be relatively more important than visual traits for pollinator attraction, particularly under shifting environmental conditions.
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Affiliation(s)
- Laura A Burkle
- Department of Ecology, Montana State University, Bozeman, MT, 59717, USA
| | - Justin B Runyon
- Rocky Mountain Research Station, USDA Forest Service, 1648 S. 7th Avenue, Bozeman, MT, 59717, USA
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62
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Sidhu SC, Wilson Rankin EE. Honey Bees Avoiding Ant Harassment at Flowers Using Scent Cues. ENVIRONMENTAL ENTOMOLOGY 2016; 45:420-426. [PMID: 26834187 DOI: 10.1093/ee/nvv230] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Pollinators require resources throughout the year to maintain healthy populations. Along the urban-natural interface, floral resource availability may be limited especially when the system experiences extreme drought and fire threats. In such areas, succulents, such as Aloe spp., are commonly planted to serve as functional drought-tolerant, fire-protective landscaping, which can also support pollinator populations. However, access to this resource may be restricted by competition from other floral foragers, including invasive pests. We measured free-foraging honey bee (Apis mellifera L.) visitation rate and visitation duration to aloe flowers with and without Argentine ants (Linepithema humile (Mayr)) in a drought-stressed environment and found that bees actively avoided foraging on the ant-occupied flowers. To determine the mechanisms of avoidance, our subsequent experiments assessed visitation in the absence of ants and compared aloe flowers treated with ant pheromone to unmanipulated flowers lacking ant pheromone. Bees approached all flowers equally, but accepted flowers without ants at a higher rate than flowers with ants. Visitation duration also increased twofold on ant-excluded flowers, which suggests that Argentine ants may limit resource acquisition by bees. Honey bees similarly avoided flowers with Argentine ant pheromone and preferentially visited unmanipulated flowers at threefold higher rate. This study demonstrates that honey bees avoid foraging on floral resources with invasive Argentine ants and that bees use ant odors to avoid ant-occupied flowers. Resource limitation by this invasive pest ant may have serious implication for sustaining healthy pollinator populations at the urban-natural interface.
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Affiliation(s)
- Sheena C Sidhu
- Department of Entomology, University of California, Riverside 900 University Ave, Riverside, CA 92521 (; ), and
| | - Erin E Wilson Rankin
- Department of Entomology, University of California, Riverside 900 University Ave, Riverside, CA 92521 (; ), and
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63
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Gillespie S, Long R, Williams N. Indirect Effects of Field Management on Pollination Service and Seed Set in Hybrid Onion Seed Production. JOURNAL OF ECONOMIC ENTOMOLOGY 2015; 108:2511-2517. [PMID: 26470371 DOI: 10.1093/jee/tov225] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 07/09/2015] [Indexed: 06/05/2023]
Abstract
Pollination in crops, as in native ecosystems, is a stepwise process that can be disrupted at any stage. Healthy pollinator populations are critical for adequate visitation, but pollination still might fail if crop management interferes with the attraction and retention of pollinators. Farmers must balance the direct benefits of applying insecticide and managing irrigation rates against their potential to indirectly interfere with the pollination process. We investigated these issues in hybrid onion seed production, where previous research has shown that high insecticide use reduces pollinator attraction. We conducted field surveys of soil moisture, nectar production, pollinator visitation, pollen-stigma interactions, and seed set at multiple commercial fields across 2 yr. We then examined how management actions, such as irrigation rate (approximated by soil moisture), or insecticide use could affect the pollination process. Onions produced maximum nectar at intermediate soil moisture, and high nectar production attracted more pollinators. Insecticide use weakly affected pollinator visitation, but when applied close to bloom reduced pollen germination and pollen tube growth. Ultimately, neither soil moisture nor insecticide use directly affected seed set, but the high correlation between pollinator visitation and seed set suggests that crop management will ultimately affect yields via indirect effects on the pollination process.
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Affiliation(s)
- Sandra Gillespie
- Department of Biology, Simon Fraser University, 8888 University Drive, Burnaby B.C. Canada, V5A 1S6.
| | - Rachael Long
- Department of Entomology, University of California, Davis, CA 95616
| | - Neal Williams
- University of California Cooperative Extension, Yolo County, CA 95616
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Takkis K, Tscheulin T, Tsalkatis P, Petanidou T. Climate change reduces nectar secretion in two common Mediterranean plants. AOB PLANTS 2015; 7:plv111. [PMID: 26374517 PMCID: PMC4614813 DOI: 10.1093/aobpla/plv111] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 08/31/2015] [Indexed: 05/25/2023]
Abstract
Global warming can lead to considerable impacts on natural plant communities, potentially inducing changes in plant physiology and the quantity and quality of floral rewards, especially nectar. Changes in nectar production can in turn strongly affect plant-pollinator interaction networks-pollinators may potentially benefit under moderate warming conditions, but suffer as resources reduce in availability as elevated temperatures become more extreme. Here, we studied the effect of elevated temperatures on nectar secretion of two Mediterranean Lamiaceae species-Ballota acetabulosa and Teucrium divaricatum. We measured nectar production (viz. volume per flower, sugar concentration per flower and sugar content per flower and per plant), number of open and empty flowers per plant, as well as biomass per flower under a range of temperatures selected ad hoc in a fully controlled climate chamber and under natural conditions outdoors. The average temperature in the climate chamber was increased every 3 days in 3 °C increments from 17.5 to 38.5 °C. Both study species showed a unimodal response of nectar production (volume per flower, sugar content per flower and per plant) to temperature. Optimal temperature for sugar content per flower was 25-26 °C for B. acetabulosa and 29-33 °C for T. divaricatum. According to our results, moderate climate warming predicted for the next few decades could benefit nectar secretion in T. divaricatum as long as the plants are not water stressed, but have a moderate negative effect on B. acetabulosa. Nevertheless, strong warming as predicted by climate change models for the end of the 21st century is expected to reduce nectar secretion in both species and can thus significantly reduce available resources for both wild bees and honeybees in Mediterranean systems.
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Affiliation(s)
- Krista Takkis
- Laboratory of Biogeography and Ecology, Department of Geography, University of the Aegean, University Hill, GR-81100 Mytilene, Greece
| | - Thomas Tscheulin
- Laboratory of Biogeography and Ecology, Department of Geography, University of the Aegean, University Hill, GR-81100 Mytilene, Greece
| | - Panagiotis Tsalkatis
- Laboratory of Biogeography and Ecology, Department of Geography, University of the Aegean, University Hill, GR-81100 Mytilene, Greece
| | - Theodora Petanidou
- Laboratory of Biogeography and Ecology, Department of Geography, University of the Aegean, University Hill, GR-81100 Mytilene, Greece
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65
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Knauer AC, Schiestl FP. Bees use honest floral signals as indicators of reward when visiting flowers. Ecol Lett 2014; 18:135-43. [PMID: 25491788 DOI: 10.1111/ele.12386] [Citation(s) in RCA: 126] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 09/20/2014] [Indexed: 11/27/2022]
Abstract
Pollinators visit flowers for rewards and should therefore have a preference for floral signals that indicate reward status, so called 'honest signals'. We investigated honest signalling in Brassica rapa L. and its relevance for the attraction of a generalised pollinator, the bumble bee Bombus terrestris (L.). We found a positive association between reward amount (nectar sugar and pollen) and the floral scent compound phenylacetaldehyde. Bumble bees developed a preference for phenylacetaldehyde over other scent compounds after foraging on B. rapa. When foraging on artificial flowers scented with synthetic volatiles, bumble bees developed a preference for those specific compounds that honestly indicated reward status. These results show that the honesty of floral signals can play a key role in their attractiveness to pollinators. In plants, a genetic constraint, resource limitation in reward and signal production, and sanctions against cheaters may contribute to the evolution and maintenance of honest signalling.
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Affiliation(s)
- A C Knauer
- Institute of Systematic Botany, University of Zurich, Zollikerstrasse 107, 8008, Zurich, Switzerland
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66
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Forrest JRK. Plant-pollinator interactions and phenological change: what can we learn about climate impacts from experiments and observations? OIKOS 2014. [DOI: 10.1111/oik.01386] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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67
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Mallet B, Martos F, Blambert L, Pailler T, Humeau L. Evidence for isolation-by-habitat among populations of an epiphytic orchid species on a small oceanic island. PLoS One 2014; 9:e87469. [PMID: 24498329 PMCID: PMC3911949 DOI: 10.1371/journal.pone.0087469] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Accepted: 12/27/2013] [Indexed: 11/19/2022] Open
Abstract
Identifying factors that promote population differentiation is of interest for understanding the early stages of speciation. Gene flow among populations inhabiting different environments can be reduced by geographical distance (isolation-by-distance) or by divergent selection resulting from local adaptation (isolation-by-ecology). Few studies have investigated the influence of these factors in small oceanic islands where the influence of geographic distance is expected to be null but where habitat diversity could have a strong effect on population differentiation. In this study, we tested for the spatial divergence of phenotypes (floral morphology and floral scent) and genotypes (microsatellites) among ten populations of Jumellea rossii, an epiphytic orchid endemic to Réunion growing in three different habitats. We found a significant genetic differentiation between populations that is structured by habitat heterogeneity rather than by geographic distance between populations. These results suggest that ecological factors might reduce gene flow among populations located in different habitats. This pattern of isolation-by-habitat may be the result of both isolation-by-ecology by habitat filtering and asynchrony in flowering phenology. Furthermore, data on floral morphology match these findings, with multivariate analysis grouping populations by habitat type but could be only due to phenotypic plasticity. Indeed floral scent compounds were not significantly different between populations indicating that specific plant-pollinator mutualism does not seem to play a major role in the population differentiation of J. rossii. In conclusion, the results from our study emphasize the importance of habitat diversity of small oceanic islands as a factor of population differentiation.
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Affiliation(s)
- Bertrand Mallet
- UMR Peuplements Végétaux et Bio-Agresseurs en Milieu Tropical, Université de La Réunion, Saint-Denis, Ile de La Réunion, France
| | - Florent Martos
- School of Life Sciences, University of KwaZulu-Natal, Pietermaritzburg, South Africa
| | - Laury Blambert
- UMR Peuplements Végétaux et Bio-Agresseurs en Milieu Tropical, Université de La Réunion, Saint-Denis, Ile de La Réunion, France
| | - Thierry Pailler
- UMR Peuplements Végétaux et Bio-Agresseurs en Milieu Tropical, Université de La Réunion, Saint-Denis, Ile de La Réunion, France
| | - Laurence Humeau
- UMR Peuplements Végétaux et Bio-Agresseurs en Milieu Tropical, Université de La Réunion, Saint-Denis, Ile de La Réunion, France
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Cosacov A, Cocucci AA, Sérsic AN. Geographical differentiation in floral traits across the distribution range of the Patagonian oil-secreting Calceolaria polyrhiza: do pollinators matter? ANNALS OF BOTANY 2014; 113:251-66. [PMID: 24252281 PMCID: PMC3890392 DOI: 10.1093/aob/mct239] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Accepted: 08/30/2013] [Indexed: 05/23/2023]
Abstract
BACKGROUND AND AIMS The underlying evolutionary processes of pollinator-driven floral diversification are still poorly understood. According to the Grant-Stebbins model speciation begins with adaptive local differentiation in the response to spatial heterogeneity in pollinators. Although this crucial process links the micro- and macroevolution of floral adaptation, it has received little attention. In this study geographical phenotypic variation was investigated in Patagonian Calceolaria polyrhiza and its pollinators, two oil-collecting bee species that differ in body size and geographical distribution. METHODS Patterns of phenotypic variation were examined together with their relationships with pollinators and abiotic factors. Six floral and seven vegetative traits were measured in 45 populations distributed across the entire species range. Climatic and edaphic parameters were determined for 25 selected sites, 2-16 bees per site of the most frequent pollinator species were captured, and a critical flower-bee mechanical fitting trait involved in effective pollination was measured. Geographical patterns of phenotypic and environmental variation were examined using uni- and multivariate analyses. Decoupled geographical variation between corolla area and floral traits related to the mechanical fit of pollinators was explored using a Mantel test. KEY RESULTS The body length of pollinators and the floral traits related to mechanical fit were strongly correlated with each other. Geographical variation of the mechanical-fit-related traits was decoupled from variation in corolla size; the latter had a geographical pattern consistent with that of the vegetative traits and was mainly affected by climatic gradients. CONCLUSIONS The results are consistent with pollinators playing a key role in shaping floral phenotype at a geographical scale and promoting the differentiation of two floral ecotypes. The relationship between the critical floral-fit-related trait and bee length remained significant even in models that included various environmental variables and an allometric predictor (corolla area). The abiotic environment also has an important role, mainly affecting floral size. Decoupled geographical variation between floral mechanical-fit-related traits and floral size would represent a strategy to maintain plant-pollinator phenotypic matching in this environmentally heterogeneous area.
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Affiliation(s)
- Andrea Cosacov
- For correspondence. Present address: Edificio de Investigaciones Biológicas y Tecnológicas, Ciudad Universitaria, CC 495, CP 5000 Córdoba, Argentina. E-mail
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Ghorecha V, Patel K, Ingle S, Sunkar R, Krishnayya NSR. Analysis of biochemical variations and microRNA expression in wild ( Ipomoea campanulata ) and cultivated ( Jacquemontia pentantha ) species exposed to in vivo water stress. PHYSIOLOGY AND MOLECULAR BIOLOGY OF PLANTS : AN INTERNATIONAL JOURNAL OF FUNCTIONAL PLANT BIOLOGY 2014; 20:57-67. [PMID: 24554839 PMCID: PMC3925483 DOI: 10.1007/s12298-013-0207-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Revised: 09/10/2013] [Accepted: 09/13/2013] [Indexed: 05/27/2023]
Abstract
The current study analyses few important biochemical parameters and microRNA expression in two closely related species (wild but tolerant Ipomoea campanulata L. and cultivated but sensitive Jacquemontia pentantha Jacq.G.Don) exposed to water deficit conditions naturally occurring in the field. Under soil water deficit, both the species showed reduction in their leaf area and SLA as compared to well-watered condition. A greater decrease in chlorophyll was noticed in J. pentantha (~50 %) as compared to I. campanulata (20 %) under stress. By contrast, anthocyanin and MDA accumulation was greater in J. pentantha as compared to I. campanulata. Multiple isoforms of superoxide dismutases (SODs) with differing activities were observed under stress in these two plant species. CuZnSOD isoforms showed comparatively higher induction (~10-40 %) in I. campanulata than J. pentantha. MicroRNAs, miR398, miR319, miR395 miR172, and miR408 showed opposing expression under water deficit in these two plant species. Expression of miR156, miR168, miR171, miR172, miR393, miR319, miR396, miR397 and miR408 from either I. campanulata or J. pentantha or both demonstrated opposite pattern of expression to that of drought stressed Arabidopsis. The better tolerance of the wild species (I. campanulata) to water deficit could be attributed to lesser variations in chlorophyll and anthocyanin levels; and relatively higher levels of SODs than J. pentantha. miRNA expression was different in I. campanulata than J. pentantha.
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Affiliation(s)
- Vallabhi Ghorecha
- />Ecology Laboratory, Botany Department, Faculty of Science, M.S.University of Baroda, Baroda, 390002 India
| | - Ketan Patel
- />Microbiology Department, Faculty of Science, M.S.University of Baroda, Baroda, 390002 India
| | - S. Ingle
- />Microbiology Department, Faculty of Science, M.S.University of Baroda, Baroda, 390002 India
| | - Ramanjulu Sunkar
- />Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74074 USA
| | - N. S. R. Krishnayya
- />Ecology Laboratory, Botany Department, Faculty of Science, M.S.University of Baroda, Baroda, 390002 India
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Burkle LA, Souza L, Genung MA, Crutsinger GM. Plant genotype, nutrients, and G × E interactions structure floral visitor communities. Ecosphere 2013. [DOI: 10.1890/es13-00039.1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Jorgensen R, Arathi HS. Floral longevity and autonomous selfing are altered by pollination and water availability in Collinsia heterophylla. ANNALS OF BOTANY 2013; 112:821-8. [PMID: 23884393 PMCID: PMC3747799 DOI: 10.1093/aob/mct146] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Accepted: 05/07/2013] [Indexed: 05/20/2023]
Abstract
BACKGROUND AND AIMS A plant investing in reproduction partitions resources between flowering and seed production. Under resource limitation, altered allocations may result in floral trait variations, leading to compromised fecundity. Floral longevity and timing of selfing are often the traits most likely to be affected. The duration of corolla retention determines whether fecundity results from outcrossing or by delayed selfing-mediated reproductive assurance. In this study, the role of pollination schedules and soil water availability on floral longevity and seed production is tested in Collinsia heterophylla (Plantaginaceae). METHODS Using three different watering regimes and pollination schedules, effects on floral longevity and seed production were studied in this protandrous, flowering annual. KEY RESULTS The results reveal that soil water status and pollination together influence floral longevity with low soil water and hand-pollinations early in the floral lifespan reducing longevity. However, early pollinations under excess water did not extend longevity, implying that resource surplus does not lengthen the outcrossing period. The results also indicate that pollen receipt, a reliable cue for fecundity, accelerates flower drop. Early corolla abscission under drought stress could potentially exacerbate sexual conflict in this protandrous, hermaphroditic species by ensuring self-pollen paternity and enabling male control of floral longevity. While pollination schedules did not affect fecundity, water stress reduced per-capita seed numbers. Unmanipulated flowers underwent delayed autonomous selfing, producing very few seeds, suggesting that inbreeding depression may limit benefits of selfing. CONCLUSIONS In plants where herkogamy and dichogamy facilitate outcrossing, floral longevity determines reproductive success and mating system. Reduction in longevity under drought suggests a strong environmental effect that could potentially alter the preferred breeding mode in this mixed-mated species. Extrapolating the findings to unpredictable global drought cycles, it is suggested that in addition to reducing yield, water stress may influence the evolutionary trajectory of plant mating system.
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Campbell DR, Wendlandt C. Altered precipitation affects plant hybrids differently than their parental species. AMERICAN JOURNAL OF BOTANY 2013; 100:1322-1331. [PMID: 23748678 DOI: 10.3732/ajb.1200473] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
PREMISE OF THE STUDY Future changes in environmental conditions may alter evolutionary processes, including hybridization in nature. Frequency of hybrids could be altered via range shifts by the parental species or by changes in prezygotic or postzygotic reproductive isolation. We examined the potential for range shifts and change in postzygotic isolation by determining effects of increasing and decreasing precipitation on leaf physiology and fitness components in the subalpine herbs Ipomopsis aggregata (Polemoniaceae), I. tenuituba¸ and their natural hybrids in a common garden in the habitat of I. aggregata. METHODS Summer precipitation was experimentally doubled or halved over 3 yr in comparison with ambient conditions. We measured relative growth rate, specific leaf area, intrinsic water-use efficiency, survival to reproduction, biomass, number of flowers produced, and floral morphology. KEY RESULTS Ipomopsis tenuituba increased relative growth rate with higher precipitation more so than did I. aggregata during the first summer, but this response did not result in changes across treatments in relative survival or final reproductive success of the two species. When precipitation was reduced, the relative success of hybrids was greater than that of the home species, I. aggregata. In dry conditions, hybrids increased water-use efficiency and fitness as indexed by number of flowers more so than the other plant types did. CONCLUSIONS Increased reproduction in hybrids in the reduced precipitation regime indicates that postzygotic reproductive isolation may breakdown under imposition of dry conditions. These results suggest the potential for frequency of hybrids to increase if severe droughts become more common.
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Affiliation(s)
- Diane R Campbell
- Department of Ecology and Evolutionary Biology, University of California, Irvine, California 92697, USA.
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Pélabon C, Osler NC, Diekmann M, Graae BJ. Decoupled phenotypic variation between floral and vegetative traits: distinguishing between developmental and environmental correlations. ANNALS OF BOTANY 2013; 111:935-44. [PMID: 23471008 PMCID: PMC3631334 DOI: 10.1093/aob/mct050] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
BACKGROUND AND AIMS In species with specialized pollination, floral traits are expected to be relatively invariant and decoupled from the phenotypic variation affecting vegetative traits. However, inferring the degree of decoupling between morphological characters from patterns of phenotypic correlations is difficult because phenotypic correlations result from the superimposition of several sources of covariance. In this study it is hypothesized that, in some cases, negative environmental correlations generated by non-congruent reaction norms across traits overshadow positive developmental correlations and generate a decoupling of the phenotypic variation between vegetative and floral traits. METHODS To test this hypothesis, Campanula rotundifolia were grown from two distinct populations under two temperature treatments, and patterns of correlation were analysed between leaf size and flower size within and among treatments. KEY RESULTS Flower size was less sensitive to temperature variation than leaf size. Furthermore, flower size and leaf size showed temperature-induced reaction norms in opposite directions. Flower size decreased with an increasing temperature, while leaf size increased. Consequently, among treatments, correlations between leaf size and flower size were negative or absent, while, within treatments, these correlations were positive or absent in the cold and warm environments, respectively. CONCLUSIONS These results confirm that the decoupling of the phenotypic variation between vegetative and floral traits can be dependent on the environment. They also underline the importance of distinguishing sources of phenotypic covariance when testing hypotheses about phenotypic integration.
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Affiliation(s)
- Christophe Pélabon
- Centre for Conservation Biology, Department of Biology, Norwegian University of Science and Technology, 7491 Trondheim, Norway.
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Soper Gorden NL, Adler LS. Abiotic conditions affect floral antagonists and mutualists of Impatiens capensis (Balsaminaceae). AMERICAN JOURNAL OF BOTANY 2013; 100:679-689. [PMID: 23482480 DOI: 10.3732/ajb.1200460] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
PREMISE OF THE STUDY While the effect of abiotic factors on leaf herbivory is well known, the relative importance of abiotic conditions influencing both mutualists and antagonists is less well understood. Species interactions could enhance or reduce the direct effects of abiotic factors, depending on how mutualists and antagonists respond to abiotic conditions. METHODS We manipulated soil nutrients and shade in a factorial design and measured soil moisture in the annual Impatiens capensis. We then measured interactions with mutualists (two pollinating species) and antagonists (herbivores, florivores, nectar thieves, and flower bud gallers), as well as plant growth, floral rewards, and plant reproduction. KEY RESULTS Fertilizer increased plant growth, floral attractiveness, mutualist and antagonist interactions, and plant reproduction. Shade had no effects, and soil moisture was negatively associated with plant growth and reproduction. All effects were additive. Mutualist and antagonist floral interactions both increased on fertilized plants, but antagonists increased at a greater rate, leading to a larger ratio of antagonist to mutualist interactions on fertilized plants. Despite having more antagonists, fertilized plants still had significantly higher reproduction, suggesting higher tolerance to antagonists. CONCLUSIONS Abiotic effects can have consistent effects on antagonists and mutualists, and on both floral and leaf antagonists. However, tolerance to antagonisms increased in favorable conditions. Thus, the direct positive effects of favorable abiotic conditions on plants outweighed negative indirect effects via increased antagonisms, which may lead to selection to grow in high-nutrient microsites in spite of increased herbivory.
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Affiliation(s)
- Nicole L Soper Gorden
- Department of Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA.
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Carlson JE, Holsinger KE. Direct and indirect selection on floral pigmentation by pollinators and seed predators in a color polymorphic South African shrub. Oecologia 2012; 171:905-19. [PMID: 23007806 DOI: 10.1007/s00442-012-2453-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Accepted: 08/24/2012] [Indexed: 12/30/2022]
Abstract
The coexistence of different color morphs is often attributed to variable selection pressures across space, time, morph frequencies, or selection agents, but the routes by which each morph is favored are rarely identified. In this study we investigated factors that influence floral color polymorphisms on a local scale in Protea, within which approximately 40% of species are polymorphic. Previous work shows that seed predators and reproductive differences likely contribute to maintaining polymorphism in four Protea species. We explored whether selection acts directly or indirectly on floral color in two populations of Protea aurea, using path analysis of pollinator behavior, nectar production, seed predation, color, morphology, and maternal fecundity fitness components. We found that avian pollinators spent more time on white morphs, likely due to nectar differences, but that this had no apparent consequences for fecundity. Instead, the number of flowers per inflorescence underpinned many of the reproductively important differences between color morphs. White morphs had more flowers per inflorescence, which itself was positively correlated with nectar production, seed predator occurrence, and total long-term seed production. The number of seeds per plant to survive predation, in contrast, was not directly associated with color or any other floral trait. Thus, although color differences may be associated with conflicting selection pressures, the selection appears to be associated with the number of flowers per inflorescence and its unmeasured correlates, rather than with inflorescence color itself.
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Affiliation(s)
- Jane E Carlson
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT 06269, USA.
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Edwards CE, Ewers BE, McClung CR, Lou P, Weinig C. Quantitative variation in water-use efficiency across water regimes and its relationship with circadian, vegetative, reproductive, and leaf gas-exchange traits. MOLECULAR PLANT 2012; 5:653-68. [PMID: 22319207 DOI: 10.1093/mp/sss004] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Drought limits light harvesting, resulting in lower plant growth and reproduction. One trait important for plant drought response is water-use efficiency (WUE). We investigated (1) how the joint genetic architecture of WUE, reproductive characters, and vegetative traits changed across drought and well-watered conditions, (2) whether traits with distinct developmental bases (e.g. leaf gas exchange versus reproduction) differed in the environmental sensitivity of their genetic architecture, and (3) whether quantitative variation in circadian period was related to drought response in Brassica rapa. Overall, WUE increased in drought, primarily because stomatal conductance, and thus water loss, declined more than carbon fixation. Genotypes with the highest WUE in drought expressed the lowest WUE in well-watered conditions, and had the largest vegetative and floral organs in both treatments. Thus, large changes in WUE enabled some genotypes to approach vegetative and reproductive trait optima across environments. The genetic architecture differed for gas-exchange and vegetative traits across drought and well-watered conditions, but not for floral traits. Correlations between circadian and leaf gas-exchange traits were significant but did not vary across treatments, indicating that circadian period affects physiological function regardless of water availability. These results suggest that WUE is important for drought tolerance in Brassica rapa and that artificial selection for increased WUE in drought will not result in maladaptive expression of other traits that are correlated with WUE.
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Levin DA. Mating system shifts on the trailing edge. ANNALS OF BOTANY 2012; 109:613-20. [PMID: 21980190 PMCID: PMC3278285 DOI: 10.1093/aob/mcr159] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Accepted: 04/20/2011] [Indexed: 05/19/2023]
Abstract
BACKGROUND The trailing edges of species ranges are becoming a subject of increasing interest as the environment changes due to global warming. Trailing edge populations are likely to face extinction because of a decline in numbers and an inability to evolve new adaptations with sufficient speed. Discussions of character change in the trailing edge have focused on physiological, exomorphic and phenological traits. The mating pattern within populations has not been part of the discourse, in spite of the fact that the mating pattern may affect the ability of populations to respond to environmental change and to maintain their sizes. In this paper, the case is made that a substantial increase in self-fertilization rates may occur via plastic responses to stress. SCOPE AND CONCLUSIONS Small populations on the trailing edge are especially vulnerable to environmental change because of inadequate levels of cross-fertilization. Evidence is presented that a deficiency of cross-seed production is due to inadequate pollinator services and a paucity of self-incompatibility alleles within populations. Evidence also is presented that if plants are self-compatible, self-fertilization may compensate in part for this deficiency through a stress-induced increase in levels of self-compatibility and stress-induced alterations in floral morphology that elevate self-pollination. Whereas increased self-fertility may afford populations the time to adapt to their changing environments, it can be concluded that increased selfing is not a panacea for the ills of environmental change, because it will lead to substantial reductions in genetic diversity, which may render adaptation unlikely.
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Affiliation(s)
- Donald A Levin
- Section of Integrative Biology, University of Texas-Austin, TX 78713, USA.
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Brys R, Jacquemyn H. Effects of human-mediated pollinator impoverishment on floral traits and mating patterns in a short-lived herb: an experimental approach. Funct Ecol 2011. [DOI: 10.1111/j.1365-2435.2011.01923.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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De Boeck HJ, Dreesen FE, Janssens IA, Nijs I. Whole-system responses of experimental plant communities to climate extremes imposed in different seasons. THE NEW PHYTOLOGIST 2011; 189:806-817. [PMID: 21054412 DOI: 10.1111/j.1469-8137.2010.03515.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
• Discrete climate events such as heat waves and droughts can have a disproportionate impact on ecosystems relative to the temporal scale over which they occur. Research oriented towards (extreme) events rather than (gradual) trends is therefore urgently needed. • Here, we imposed heat waves and droughts (50-yr return time) in a full factorial design on experimental plant communities in spring, summer or autumn. Droughts were created by removing the controlled water table (rainout shelters prevented precipitation), while heat waves were imposed with infrared heaters. • Measurements of whole-system CO(2) exchange, growth and biomass production revealed multiple interactions between treatments and the season in which they occurred. Heat waves had only small and transient effects, with infrared imaging showing little heat stress because of transpirational cooling. If heat waves were combined with drought, negative effects observed in single factor drought treatments were exacerbated through intensified soil drying, and heat stress in summer. Plant recovery from stress differed, affecting the biomass yield. • In conclusion, the timing of extreme events is critical regarding their impact, and synergisms between heat waves and drought aggravate the negative effects of these extremes on plant growth and functioning.
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Affiliation(s)
- Hans J De Boeck
- Research Group of Plant and Vegetation Ecology, Department of Biology, Universiteit Antwerpen (Campus Drie Eiken), Universiteitsplein 1, B-2610 Wilrijk, Belgium
| | - Freja E Dreesen
- Research Group of Plant and Vegetation Ecology, Department of Biology, Universiteit Antwerpen (Campus Drie Eiken), Universiteitsplein 1, B-2610 Wilrijk, Belgium
| | - Ivan A Janssens
- Research Group of Plant and Vegetation Ecology, Department of Biology, Universiteit Antwerpen (Campus Drie Eiken), Universiteitsplein 1, B-2610 Wilrijk, Belgium
| | - Ivan Nijs
- Research Group of Plant and Vegetation Ecology, Department of Biology, Universiteit Antwerpen (Campus Drie Eiken), Universiteitsplein 1, B-2610 Wilrijk, Belgium
- King Saud University, Riyadh, Saudi Arabia
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Cuevas E, López S. Sex Ratio and Sex-specific Latitudinal Variation in Floral Characteristics of Gynodioecious Kallstroemia grandiflora (Zygophyllaceae) in Mexico. Biotropica 2010. [DOI: 10.1111/j.1744-7429.2010.00692.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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81
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Pélabon C, Armbruster WS, Hansen TF. Experimental evidence for the Berg hypothesis: vegetative traits are more sensitive than pollination traits to environmental variation. Funct Ecol 2010. [DOI: 10.1111/j.1365-2435.2010.01770.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Christophe Pélabon
- Department of Biology, Centre for Conservation Biology, Norwegian University of Science and Technology, 7491 Trondheim, Norway
| | - W. Scott Armbruster
- Department of Biology, Norwegian University of Science and Technology, 7491 Trondheim, Norway
- School of Biological Sciences, King Henry Building, University of Portsmouth, Portsmouth PO1 2DY, UK
- Institute of Arctic Biology, University of Alaska, Fairbanks, Alaska 99775, USA
| | - Thomas F. Hansen
- Department of Biology, Centre for Ecological and Evolutionary Synthesis, University of Oslo, 0316 Oslo, Norway
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Halpern SL, Adler LS, Wink M. Leaf herbivory and drought stress affect floral attractive and defensive traits in Nicotiana quadrivalvis. Oecologia 2010; 163:961-71. [PMID: 20461411 DOI: 10.1007/s00442-010-1651-z] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2009] [Accepted: 04/20/2010] [Indexed: 10/19/2022]
Abstract
Adaptive phenotypic plasticity allows sessile organisms such as plants to match trait expression to the particular environment they experience. Plasticity may be limited, however, by resources in the environment, by responses to prior environmental cues, or by previous interactions with other species, such as competition or herbivory. Thus, understanding the expression of plastic traits and their effects on plant performance requires evaluating trait expression in complex environments, rather than across levels of a single variable. In this study, we tested the independent and combined effects of two components of a plant's environment, herbivory and water availability, on the expression of attractive and defensive traits in Nicotiana quadrivalvis in the greenhouse. Damage and drought did not affect leaf nicotine concentrations but had additive and non-additive effects on floral attractive and defensive traits. Plants in the high water treatment produced larger flowers with more nectar than in the low water treatment. Leaf damage induced greater nectar volumes in the high water treatment only, suggesting that low water limited plastic responses to herbivore damage. Leaf damage also tended to induce higher nicotine concentrations in nectar, consistent with other studies showing that leaf damage can induce floral defenses. Our results suggest that there are separate and synergistic effects of leaf herbivory and drought on floral trait expression, and thus plasticity in response to complex environments may influence plant fitness via effects on floral visitation and defense.
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Affiliation(s)
- Stacey L Halpern
- Biology Department, Pacific University, 2043 College Way, Forest Grove, OR 97116, USA.
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Canopy and leaf gas exchange of Haloxylon ammodendron under different soil moisture regimes. SCIENCE CHINA-LIFE SCIENCES 2010; 53:718-28. [DOI: 10.1007/s11427-010-4013-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Accepted: 02/08/2010] [Indexed: 10/19/2022]
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Maherali H, Walden AE, Husband BC. Genome duplication and the evolution of physiological responses to water stress. THE NEW PHYTOLOGIST 2009; 184:721-731. [PMID: 19703115 DOI: 10.1111/j.1469-8137.2009.02997.x] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Whole-genome multiplication, or polyploidy, is common in angiosperms and many species consist of multiple cytotypes that have different physiological tolerances. However, the relative importance of genome duplication vs post-duplication evolutionary change in causing differentiation between cytotypes is not known. We examined the water relations of Chamerion angustifolium, a herbaceous perennial in which diploid and tetraploid cytotypes occupy different niches. To differentiate between the effects of genome duplication and evolutionary changes that followed polyploidization, we compared extant diploids and tetraploids with experimentally synthesized neotetraploids. Tetraploids had 32% higher xylem hydraulic conductivity (K(H)) than neotetraploids and 87% higher K(H) than diploids, but vulnerability to water stress induced cavitation and gas exchange sensitivity to water potential did not differ among cytotypes. Nevertheless, tetraploids took 22% and 30% longer to wilt than neotetraploids and diploids. A simple hydraulic model suggested that tetraploids deplete soil moisture to a greater degree than neotetraploids and diploids before reaching leaf water potentials that cause stomatal closure. We conclude that the different physiological tolerances and distribution of diploid and tetraploid C. angustifolium are unlikely to be caused solely by genome duplication. The enhanced ability of tetraploids to survive water stress likely evolved after polyploidization.
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Affiliation(s)
- Hafiz Maherali
- Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Alison E Walden
- Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Brian C Husband
- Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
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85
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Randle AM, Slyder JB, Kalisz S. Can differences in autonomous selfing ability explain differences in range size among sister-taxa pairs of Collinsia (Plantaginaceae)? An extension of Baker's Law. THE NEW PHYTOLOGIST 2009; 183:618-629. [PMID: 19659585 DOI: 10.1111/j.1469-8137.2009.02946.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Species with greater selfing ability are predicted to be better adapted for colonizing new habitats (Baker's Law). Here, we tested an expansion of this hypothesis: that species proficient at autonomous selfing have larger range sizes than their less proficient sister taxa. We also tested competing hypotheses regarding seed production and niche breadth on range size. Floral traits affecting the proficiency of autonomous selfing were measured and seed production was calculated for six sister-taxa pairs in the clade Collinsia. We tested for the hypothesized effects of these variables on elevational distribution and range size. We found that species most proficient at selfing had significantly larger range sizes than their sister-taxa that were less proficient at selfing. Species proficient at autonomous selfing occupied a higher mean elevation than their sister taxa, but they did not differ in their total elevational range. Species with greater seed production did not have larger range sizes. Our results extend Baker's Law, suggesting that species proficient at autonomous selfing are better adapted to establish new populations and thus can more readily expand their range. Autonomous selfing ability may play a vital role in explaining variance in range size among other species.
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Affiliation(s)
- April M Randle
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Jacob B Slyder
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Susan Kalisz
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
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86
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Brock MT, Stinchcombe JR, Weinig C. Indirect effects of FRIGIDA: floral trait (co)variances are altered by seasonally variable abiotic factors associated with flowering time. J Evol Biol 2009; 22:1826-38. [PMID: 19583697 DOI: 10.1111/j.1420-9101.2009.01794.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reproductive timing is a critical life-history event that could influence the (co)variation of traits developing later in ontogeny by regulating exposure to seasonally variable factors. In a field experiment with Arabidopsis thaliana, we explore whether allelic variation at a flowering-time gene of major effect (FRIGIDA) affects (co)variation of floral traits by regulating exposure to photoperiod, temperature, and moisture levels. We detect a positive latitudinal cline in floral organ size among plants with putatively functional FRI alleles. Statistically controlling for bolting day removes the cline, suggesting that seasonal abiotic variation affects floral morphology. Both photoperiod and precipitation at bolting correlate positively with the length of petals, stamens, and pistils. Additionally, floral (co)variances differ significantly across FRI backgrounds, such that the sign of some floral-trait correlations reverses. Subsequent experimental manipulations of photoperiod and water availability demonstrate direct effects of these abiotic factors on floral traits. In sum, these results highlight how the timing of life-history events can affect the expression of traits developing later in ontogeny, and provide some of the first empirical evidence for the effects of major genes on evolutionary potential.
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Affiliation(s)
- M T Brock
- Department of Botany, University of Wyoming, 1000 E. University Ave., Laramie, WY 82071, USA.
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87
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Schlumpberger BO, Cocucci AA, Moré M, Sérsic AN, Raguso RA. Extreme variation in floral characters and its consequences for pollinator attraction among populations of an Andean cactus. ANNALS OF BOTANY 2009; 103:1489-500. [PMID: 19342397 PMCID: PMC2701769 DOI: 10.1093/aob/mcp075] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
BACKGROUND AND AIMS A South American cactus species, Echinopsis ancistrophora (Cactaceae), with dramatic among-population variation in floral traits is presented. METHODS Eleven populations of E. ancistrophora were studied in their habitats in northern Argentina, and comparisons were made of relevant floral traits such as depth, stigma position, nectar volume and sugar concentration, and anthesis time. Diurnal and nocturnal pollinator assemblages were evaluated for populations with different floral trait combinations. KEY RESULTS Remarkable geographical variations in floral traits were recorded among the 11 populations throughout the distribution range of E. ancistrophora, with flower lengths ranging from 4.5 to 24.1 cm. Other floral traits associated with pollinator attraction also varied in a population-specific manner, in concert with floral depth. Populations with the shortest flowers showed morning anthesis and those with the longest flowers opened at dusk, whereas those with flowers of intermediate length opened at unusual times (2300-0600 h). Nectar production varied non-linearly with floral length; it was absent to low (population means up to 15 microL) in short- to intermediate-length flowers, but was high (population means up to 170 microL) in the longest tubed flowers. Evidence from light-trapping of moths, pollen carriage on their bodies and moth scale deposition on stigmas suggests that sphingid pollination is prevalent only in the four populations with the longest flowers, in which floral morphological traits and nectar volumes match the classic expectations for the hawkmoth pollination syndrome. All other populations, with flowers 4.5-15 cm long, were pollinated exclusively by solitary bees. CONCLUSIONS The results suggest incipient differentiation at the population level and local adaptation to either bee or hawkmoth (potentially plus bee) pollination.
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88
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Herrera J. Visibility vs. biomass in flowers: exploring corolla allocation in Mediterranean entomophilous plants. ANNALS OF BOTANY 2009; 103:1119-27. [PMID: 19258340 PMCID: PMC2707908 DOI: 10.1093/aob/mcp046] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
BACKGROUND AND AIMS While pollinators may in general select for large, morphologically uniform floral phenotypes, drought stress has been proposed as a destabilizing force that may favour small flowers and/or promote floral variation within species. METHODS The general validity of this concept was checked by surveying a taxonomically diverse array of 38 insect-pollinated Mediterranean species. The interplay between fresh biomass investment, linear size and percentage corolla allocation was studied. Allometric relationships between traits were investigated by reduced major-axis regression, and qualitative correlates of floral variation explored using general linear-model MANOVA. KEY RESULTS Across species, flowers were perfectly isometrical with regard to corolla allocation (i.e. larger flowers were just scaled-up versions of smaller ones and vice versa). In contrast, linear size and biomass varied allometrically (i.e. there were shape variations, in addition to variations in size). Most floral variables correlated positively and significantly across species, except corolla allocation, which was largely determined by family membership and floral symmetry. On average, species with bilateral flowers allocated more to the corolla than those with radial flowers. Plant life-form was immaterial to all of the studied traits. Flower linear size variation was in general low among conspecifics (coefficients of variation around 10 %), whereas biomass was in general less uniform (e.g. 200-400 mg in Cistus salvifolius). Significant among-population differences were detected for all major quantitative floral traits. CONCLUSIONS Flower miniaturization can allow an improved use of reproductive resources under prevailingly stressful conditions. The hypothesis that flower size reflects a compromise between pollinator attraction, water requirements and allometric constraints among floral parts is discussed.
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89
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Elliott SE, Irwin RE. Effects of flowering plant density on pollinator visitation, pollen receipt, and seed production in Delphinium barbeyi (Ranunculaceae). AMERICAN JOURNAL OF BOTANY 2009; 96:912-919. [PMID: 21628244 DOI: 10.3732/ajb.0800260] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Variation in flowering plant density can have conflicting effects on pollination and seed production. Dense flower patches may attract more pollinators, but flowers in those patches may also compete for pollinator visits and abiotic resources. We examined how natural and experimental conspecific flowering plant density affected pollen receipt and seed production in a protandrous, bumble bee-pollinated wildflower, Delphinium barbeyi (Ranunculaceae). We also compared floral sex ratios, pollinator visitation rates, and pollen limitation of seed set from early to late in the season to determine whether these factors mirrored seasonal changes in pollen receipt and seed production. Pollen receipt increased with natural flowering plant density, while seed production increased across lower densities and decreased across higher flower densities. Experimental manipulation of flowering plant density did not affect pollinator visitation rate, pollen receipt, or seed production. Although pollinator visitation rate increased 10-fold from early to late in the season, pollen receipt and seed set decreased over the season. Seed set was never pollen-limited. Thus, despite widespread effects of flowering plant density on plant reproduction in other species, the effects of conspecific flowering plant density on D. barbeyi pollination and seed production are minor.
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Affiliation(s)
- Susan E Elliott
- Biology Department, Dartmouth College, Hanover, New Hampshire 03755 USA
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Irwin RE, Galen C, Rabenold JJ, Kaczorowski R, McCutcheon ML. MECHANISMS OF TOLERANCE TO FLORAL LARCENY IN TWO WILDFLOWER SPECIES. Ecology 2008; 89:3093-3104. [DOI: 10.1890/08-0081.1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2008] [Revised: 03/04/2008] [Accepted: 03/13/2008] [Indexed: 11/18/2022]
Affiliation(s)
- Rebecca E. Irwin
- Biology Department, Dartmouth College, Hanover, New Hampshire 03755 USA
- Rocky Mountain Biological Laboratory, Crested Butte, Colorado 81224 USA
| | - Candace Galen
- Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211 USA
| | - Jessica J. Rabenold
- Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211 USA
| | - Rainee Kaczorowski
- Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211 USA
| | - Meghan L. McCutcheon
- Rocky Mountain Biological Laboratory, Crested Butte, Colorado 81224 USA
- School of Natural Sciences, Hampshire College, Amherst, Massachusetts 01002 USA
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Effmert U, Dinse C, Piechulla B. Influence of green leaf herbivory by Manduca sexta on floral volatile emission by Nicotiana suaveolens. PLANT PHYSIOLOGY 2008; 146:1996-2007. [PMID: 18281418 PMCID: PMC2287366 DOI: 10.1104/pp.107.112326] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2007] [Accepted: 02/07/2008] [Indexed: 05/23/2023]
Abstract
Plants have to cope with various abiotic and biotic impacts as a consequence of changing environments, which can impair their ability to sexually reproduce. The main objective of this study was to investigate whether green leaf herbivory, having one of the most hazardous biotic impacts, would have any direct effect on the production and emission of floral volatiles because volatiles are known to play a crucial role in pollination. Nicotiana suaveolens plants were challenged with Manduca sexta feeding on leaves, and alterations in the quality and quantity of the floral blend, shifts in emission patterns, and changes in expression patterns of the floral benzoic/salicylic acid carboxyl-methyltransferase were monitored in noninfested and infested plants. Leaves responded to larval feeding by herbivory-induced diurnal emission of semiochemicals, whereas the emission of floral volatiles remained unchanged in comparison to the noninfested control. Neither the volatile composition nor the quantity of components or the nocturnal emission patterns was altered. The mRNA and protein levels of the benzoic/salicylic acid carboxyl-methyltransferase, as well as its enzyme activity, also did not show any significant differences. These results indicate that metabolism in flowers at and postanthesis is an autonomous process and is independent of metabolic changes in green leaves. By this sustaining mechanism, N. suaveolens plants ensure sexual reproduction even under unfavorable conditions.
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Affiliation(s)
- Uta Effmert
- Institute of Biological Sciences, Biochemistry, University of Rostock, 18059 Rostock, Germany.
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92
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Borrell BJ. Scaling of Nectar Foraging in Orchid Bees. Am Nat 2007; 169:569-80. [PMID: 17427129 DOI: 10.1086/512689] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2006] [Accepted: 11/21/2006] [Indexed: 11/04/2022]
Abstract
Morphology influences the rate at which foraging bees visit nectar flowers, the quantity of nectar they must consume to fuel their activities, and, consequently, the profitability of flower species. Because feeding time is a major determinant of visitation rate, I used a biomechanical model to examine how energy intake rate (E) varies with sucrose concentration, body mass (M), and proboscis length in orchid bees (Apidae: Euglossini). Under geometric scaling, the optimal sugar concentration (Smax) should be largely independent of body size, and E proportional to M1.0. In a comparative study of 30 orchid bee species ranging from 50 to 800 mg, Smax fell between 35% and 40% w/w, but E proportional to M0.54, significantly less than model predictions. Proboscis length and radius scale geometrically with body mass, but proboscis length exhibits substantial size-independent variation, particularly in small bees. One cost of a long proboscis is a reduction in both E and Smax in accordance with the scaling model. This finding highlights a difference between the lapping mechanism used by bumblebees and the suction mechanism used by orchid bees. A field study confirms that orchid bees harvest nectars with between 34% and 42% sucrose, independent of body size.
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Affiliation(s)
- Brendan J Borrell
- Department of Integrative Biology, University of California, Berkeley, California 94720, USA.
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Fenster CB, Cheely G, Dudash MR, Reynolds RJ. Nectar reward and advertisement in hummingbird-pollinated Silene virginica (Caryophyllaceae). AMERICAN JOURNAL OF BOTANY 2006; 93:1800-1807. [PMID: 21642126 DOI: 10.3732/ajb.93.12.1800] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We tested for an association between nectar and various floral traits and investigated their roles as primary and secondary pollinator attractants in hummingbird-pollinated Silene virginica. Our goal was to gain insight into the mechanisms of pollinator-mediated selection that underlies floral trait divergence within the genus. In a field population of S. virginica, we measured five floral and eight vegetative traits and quantified nectar volume, nectar sugar concentration, and total sugar reward (nectar volume × nectar sugar concentration). All three components of nectar reward were positively correlated to flower size, and nectar volume varied significantly among individuals within the population. To ascertain whether the correlation of specific floral traits with nectar reward influences the behavior of the primary pollinator of S. virginica, the ruby-throated hummingbird, Archilochus colubris, we investigated whether A. colubris preferred the expression of floral traits associated with high nectar volume and total sugar reward. We accomplished this by constructing floral arrays consisting of artificial flowers that had equal nectar quantity and total sugar reward but that differed in petal area and corolla tube diameter, which were positively correlated with nectar quantity and total sugar reward in our field study. In observations of visitation frequencies to the various floral-trait combinations, hummingbirds preferentially visited artificial floral phenotypes with larger petal displays, with the greatest preference for floral phenotypes with both larger petals and wider corolla-tube diameters. This association between primary and secondary floral attractants and hummingbird discrimination of floral features supports the concept that the floral traits of S. virginica reflect pollinator-mediated selection by the principal pollinator.
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Affiliation(s)
- Charles B Fenster
- Department of Biology, University of Maryland, College Park, Maryland 20742 USA; Mountain Lake Biological Station, Pembroke, Virginia 24136 USA; and Department of Biology, Amherst College, Amherst, Massachusetts 01002 USA
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Island–mainland difference in Nicotiana glauca (Solanaceae) corolla length: a product of pollinator-mediated selection? Evol Ecol 2006. [DOI: 10.1007/s10682-006-9125-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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95
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Šimková A, Ottová E, Morand S. MHC variability, life-traits and parasite diversity of European cyprinid fish. Evol Ecol 2006. [DOI: 10.1007/s10682-006-0014-z] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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96
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Ackermann M, Weigend M. Nectar, floral morphology and pollination syndrome in Loasaceae subfam. Loasoideae (Cornales). ANNALS OF BOTANY 2006; 98:503-14. [PMID: 16820408 PMCID: PMC2803572 DOI: 10.1093/aob/mcl136] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2006] [Revised: 03/20/2006] [Accepted: 05/19/2006] [Indexed: 05/10/2023]
Abstract
BACKGROUND AND AIMS Loasaceae subfam. Loasoideae are mostly distributed in South America (sea level to over 4500 m) with a wide range of animals documented as pollinators. The aim was to investigate correlations between nectar parameters, flower morphology, pollination syndrome and phylogeny. METHODS Nectar was collected from 29 species from seven genera in the subfamily. Concentration and volumes were measured and the amount of sugar calculated. Correlations of nectar data were plotted on a ternary graph and nectar characteristics compared with flower visitors, floral morphology and phylogenetic data. KEY RESULTS Sugar concentrations are generally higher than reported for most plant families in the literature. The species investigated can be roughly grouped as follows. Group I: plants with approx. 1.5(-3.5) microL nectar with (40-)60-80% sugar and 0.19-2 mg sugar flower-1; with small, white, star-shaped corollas, pollinated by short-tongued bees. Groups II, III and IV: plants with mostly orange, balloon-, saucer-, bowl- or bell-shaped corollas. Group II: plants with approx. 9-14 microL nectar with 40-60% sugar and 4-10 mg sugar flower-1; mostly visited by long-tongued bees and/or hummingbirds. Group III: plants with 40-100 microL nectar with 30-40% sugar and 14-36 mg sugar flower-1, mostly visited by hummingbirds. Group IV: geoflorous plants with 80-90 microL with 10-15% sugar and 8.5-12 mg sugar flower-1, presumably visited by small mammals. Groups II and III include species visited by bees and/or hummingbirds. CONCLUSIONS Pollinator switches from short-tongued bees via long-tongued bees to hummingbirds appear to have taken place repeatedly in the genera Nasa, Loasa and Caiophora. Changes in nectar amount and concentration appear to evolve rapidly with little phylogenetic constraint.
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Affiliation(s)
- Markus Ackermann
- Institut für Biologie der Freien Universität Berlin, Systematische Botanik und Pflanzengeographie, Altensteinstrasse 6, 14195 Berlin, Germany.
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