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Wu LY, Huang SQ, Tong ZY. Elevational and temporal patterns of pollination success in distylous and homostylous buckwheats ( Fagopyrum) in the Hengduan Mountains. PLANT DIVERSITY 2024; 46:661-670. [PMID: 39290890 PMCID: PMC11403118 DOI: 10.1016/j.pld.2023.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2023] [Revised: 09/21/2023] [Accepted: 10/07/2023] [Indexed: 09/19/2024]
Abstract
Reproductive strategies of sexually dimorphic plants vary in response to the environment. Here, we ask whether the sexual systems of Fagopyrum species (i.e., selfing homostylous and out-crossing distylous) represent distinct adaptive strategies to increase reproductive success in changing alpine environments. To answer this question, we determined how spatial and temporal factors (e.g., elevation and peak flowering time) affect reproductive success (i.e., stigmatic pollen load) in nine wild Fagopyrum species (seven distylous and two homostylous) among 28 populations along an elevation gradient of 1299-3315 m in the Hengduan Mountains, southwestern China. We also observed pollinators and conducted hundreds of hand pollinations to investigate inter/intra-morph compatibility, self-compatibility and pollen limitation in four Fagopyrum species (two distylous and two homostylous). We found that Fagopyrum species at higher elevation generally had bigger flowers and more stigmatic pollen loads; late-flowering individuals had smaller flowers and lower pollen deposition. Stigmatic pollen deposition was more variable in distylous species than in homostylous species. Although seed set was not pollen-limited in all species, we found that fruit set was much lower in distylous species, which rely on frequent pollinator visits, than in homostylous species capable of autonomous self-pollination. Our findings that pollination success increases at high elevations and decreases during the flowering season suggest that distylous and homostylous species have spatially and temporally distinct reproductive strategies related to environment-dependent pollinator activity.
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Affiliation(s)
- Ling-Yun Wu
- Faculty of Resources and Environmental Science, Hubei University, Wuhan 430062, China
- Institute of Evolution and Ecology, School of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Shuang-Quan Huang
- Institute of Evolution and Ecology, School of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Ze-Yu Tong
- Institute of Evolution and Ecology, School of Life Sciences, Central China Normal University, Wuhan 430079, China
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2
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Larue C, Petit RJ. Harmful self-pollination drives gynodioecy in European chestnut, a self-incompatible tree. AMERICAN JOURNAL OF BOTANY 2024; 111:e16329. [PMID: 38708705 DOI: 10.1002/ajb2.16329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Revised: 02/27/2024] [Accepted: 03/04/2024] [Indexed: 05/07/2024]
Abstract
PREMISE Gynodioecy is a rare sexual system in which two genders (sensu Lloyd, 1980), cosexuals and females, coexist. To survive, female plants must compensate for their lack of siring capacity and male attractiveness. In European chestnut (Castanea sativa), an outcrossing tree, self-pollination reduces fruit set in cosexual individuals because of late-acting self-incompatibility and early inbreeding depression. Could this negative sexual interaction explain the presence of females in this species? METHODS We studied gender variation in wild populations of European chestnut. In addition, we compared fruit set (the proportion of flowers giving fruits) and other key female fitness components as well as reproductive allocation between genders. We then performed emasculation experiments in cosexual trees, by removing nectar-producing fertile male inflorescences. We also removed sterile but nectar-producing male inflorescences from female trees, as a control. RESULTS We found a highly variable proportion of male-sterile individuals in the wild in European chestnut. In the experimental plot, trees from each gender had similar size, flower density, and burr set, but different fruit set. Removing nectar-producing male inflorescences from branches or entire trees increased fruit set in cosexual but not in female trees. CONCLUSIONS These results show that self-pollination impairs fruit set in cosexual trees. Female trees avoid these problems as they do not produce pollen but continue to attract pollinators thanks to their rewarding male-sterile inflorescences, resulting in a much higher fruit set than in cosexuals. This demonstrates that even outcrossed plants can benefit from the cessation of self-pollination, to the point that unisexuality can evolve.
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Affiliation(s)
- Clément Larue
- Univ. Bordeaux, INRAE, Biogeco, Cestas, 33610, France
- INVENIO, Maison Jeannette, Douville, 24140, France
| | - Rémy J Petit
- Univ. Bordeaux, INRAE, Biogeco, Cestas, 33610, France
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3
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Dai W, Ochola AC, Li Y. Spatio-Temporal Variations in Pollen Limitation and Floral Traits of an Alpine Lousewort ( Pedicularis rhinanthoides) in Relation to Pollinator Availability. PLANTS (BASEL, SWITZERLAND) 2022; 12:78. [PMID: 36616207 PMCID: PMC9824556 DOI: 10.3390/plants12010078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 12/14/2022] [Accepted: 12/20/2022] [Indexed: 06/17/2023]
Abstract
Populations of the same plant species living in different locations but flowering at different times may vary in pollinator availability and floral traits. However, the spatial and temporal links between floral traits and pollination are rarely included in single studies. In this study, three populations of an alpine lousewort, Pedicularis rhinanthoides Schrenk subsp. tibetica (Bonati) Tsoong, were surveyed to detect the variations in floral traits and pollinator activity. We hypothesized that floral divergence was spatio-temporally correlated with pollen limitation (PL) in relation to pollinators. Sampled plants from each population were divided into three groups, according to flowering stage: early, peak, and late. Pollen-supplementation experiments and investigations into pollinators, reproductive success, and floral traits were conducted on the plants from the different flowering stages and across the populations. Our results showed that the extent of PL varies across populations and among flowering stages. Populations in which more pollinators were recorded displayed a lower extent of PL. Furthermore, the temporal differences in PL showed a similar pattern for the three populations; the plants from the peak flowering stage suffered slighter PL than those from the other two stages. Nevertheless, some of the floral traits displayed similar spatial and temporal patterns to the PL, while the others only varied among the populations spatially. The results indicated that the performance of floral traits in a particular spatial-temporal situation shows they are well adapted to the corresponding pollination environment, which might help plants to optimize their reproductive fitness under different abiotic factors.
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Affiliation(s)
- Wenkui Dai
- College of Horticulture and Landscape Architecture, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan 430074, China
| | - Anne Christine Ochola
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan 430074, China
| | - Yongquan Li
- College of Horticulture and Landscape Architecture, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China
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Diller C, Castañeda‐Zárate M, Johnson SD. Why honeybees are poor pollinators of a mass-flowering plant: Experimental support for the low pollen quality hypothesis. AMERICAN JOURNAL OF BOTANY 2022; 109:1305-1312. [PMID: 35844034 PMCID: PMC9545086 DOI: 10.1002/ajb2.16036] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Revised: 06/22/2022] [Accepted: 06/22/2022] [Indexed: 06/15/2023]
Abstract
PREMISE Honeybees dominate the flower-visitor assemblages of many plant species, yet their efficiency in terms of the quality of pollen delivered to stigmas is largely unknown. We investigated why honeybees are poor pollinators of Aloe ferox, a self-incompatible succulent treelet with large numbers of flowers. Honeybees are very frequent visitors to flowers of this species, yet contribute very little to seed production. METHODS We assessed pollen loads on honeybees, studied their visitation behavior, selectively excluded birds from plants to determine direct effects of bees on pollen deposition, seed set, and ovule abortion, and used a novel "split-pollinator" method to test whether honeybees deposit mainly low-quality self pollen. For the latter, we captured honeybees, and with their existing pollen loads, used them to either pollinate virgin flowers on the plant on which they were caught or to pollinate virgin flowers on different plants. RESULTS Honeybees cumulatively deposit as much pollen on stigmas as do birds, but our experiments showed that the pollen deposited by honeybees is mostly low-quality self pollen that leads to substantial ovule discounting and depressed seed set. CONCLUSIONS Lack of movement among A. ferox plants during individual honeybee foraging bouts is the most likely explanation for their deposition of low-quality self pollen on stigmas. The "split-pollinator" method is a simple and cost-effective technique to test the quality of pollination.
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Affiliation(s)
- Carolina Diller
- Centre for Functional Biodiversity, School of Life SciencesUniversity of KwaZulu‐NatalP. Bag X01ScottsvillePietermaritzburg3209South Africa
| | - Miguel Castañeda‐Zárate
- Centre for Functional Biodiversity, School of Life SciencesUniversity of KwaZulu‐NatalP. Bag X01ScottsvillePietermaritzburg3209South Africa
| | - Steven D. Johnson
- Centre for Functional Biodiversity, School of Life SciencesUniversity of KwaZulu‐NatalP. Bag X01ScottsvillePietermaritzburg3209South Africa
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Castilla AR, Garrote PJ, Żywiec M, Calvo G, Suárez-Esteban A, Delibes M, Godoy JA, Picó FX, Fedriani JM. Genetic rescue by distant trees mitigates qualitative pollen limitation imposed by fine-scale spatial genetic structure. Mol Ecol 2019; 28:4363-4374. [PMID: 31495974 DOI: 10.1111/mec.15233] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 07/17/2019] [Accepted: 07/22/2019] [Indexed: 11/26/2022]
Abstract
Restricted seed dispersal frequently leads to fine-scale spatial genetic structure (i.e., FSGS) within plant populations. Depending on its spatial extent and the mobility of pollinators, this inflated kinship at the immediate neighbourhood can critically impoverish pollen quality. Despite the common occurrence of positive FSGS within plant populations, our knowledge regarding the role of long-distance pollination preventing reproductive failure is still limited. Using microsatellite markers, we examined the existence of positive FSGS in two low-density populations of the tree Pyrus bourgaeana. We also designed controlled crosses among trees differing in their kinship to investigate the effects of increased local kinship on plant reproduction. We used six pollination treatments and fully monitored fruit production, fruit and seed weight, proportion of mature seeds per fruit, and seed germination. Our results revealed positive FSGS in both study populations and lower fruit initiation in flowers pollinated with pollen from highly-genetically related individuals within the neighbourhood, with this trend intensifying as the fruit development progressed. Besides, open-pollinated flowers exhibited lower performance compared to those pollinated by distant pollen donors, suggesting intense qualitative pollen limitation in natural populations. We found positive fine-scale spatial genetic structure is translated into impoverished pollen quality from nearby pollen donors which negatively impacts the reproductive success of trees in low-density populations. Under this scenario of intrapopulation genetic rescue by distant pollen donors, the relevance of highly-mobile pollinators for connecting spatially and genetically distant patches of trees may be crucial to safeguarding population recruitment.
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Affiliation(s)
- Antonio R Castilla
- Instituto Superior of Agronomy, Centre for Applied Ecology "Prof. Baeta Neves"/INBIO, University of Lisbon, Lisbon, Portugal.,Departamento de Ecología Integrativa, Estación Biológica de Doñana (EBD), Consejo Superior de Investigaciones Científicas (CSIC), Sevilla, Spain
| | - Pedro J Garrote
- Instituto Superior of Agronomy, Centre for Applied Ecology "Prof. Baeta Neves"/INBIO, University of Lisbon, Lisbon, Portugal.,Departamento de Biología de la Conservación, Estación Biológica de Doñana, Consejo Superior de Investigaciones Científicas (CSIC), Sevilla, Spain
| | - Magdalena Żywiec
- Instituto Superior of Agronomy, Centre for Applied Ecology "Prof. Baeta Neves"/INBIO, University of Lisbon, Lisbon, Portugal.,W. Szafer Institute of Botany, Polish Academy of Sciences, Krakow, Poland
| | - Gemma Calvo
- Departamento de Biología de la Conservación, Estación Biológica de Doñana, Consejo Superior de Investigaciones Científicas (CSIC), Sevilla, Spain
| | - Alberto Suárez-Esteban
- Departamento de Biología de la Conservación, Estación Biológica de Doñana, Consejo Superior de Investigaciones Científicas (CSIC), Sevilla, Spain
| | - Miguel Delibes
- Departamento de Biología de la Conservación, Estación Biológica de Doñana, Consejo Superior de Investigaciones Científicas (CSIC), Sevilla, Spain
| | - José A Godoy
- Departamento de Ecología Integrativa, Estación Biológica de Doñana (EBD), Consejo Superior de Investigaciones Científicas (CSIC), Sevilla, Spain
| | - F Xavier Picó
- Departamento de Ecología Integrativa, Estación Biológica de Doñana (EBD), Consejo Superior de Investigaciones Científicas (CSIC), Sevilla, Spain
| | - Jose M Fedriani
- Instituto Superior of Agronomy, Centre for Applied Ecology "Prof. Baeta Neves"/INBIO, University of Lisbon, Lisbon, Portugal.,Departamento de Biología de la Conservación, Estación Biológica de Doñana, Consejo Superior de Investigaciones Científicas (CSIC), Sevilla, Spain.,Centro de Investigaciones sobre Desertificación CIDE, CSIC-UVEG-GV, Moncada, Spain
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6
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Teixido AL, Aizen MA. Reproductive assurance weakens pollinator-mediated selection on flower size in an annual mixed-mating species. ANNALS OF BOTANY 2019; 123:1067-1077. [PMID: 30778517 PMCID: PMC6589515 DOI: 10.1093/aob/mcz014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 01/14/2019] [Indexed: 06/09/2023]
Abstract
BACKGROUND AND AIMS In animal-pollinated plants, direct and indirect selection for large and small flowers in predominantly outcrossing and selfing species, respectively, is a common consequence of pollen limitation (PL). However, many hermaphroditic species show a mixed-mating system known as delayed selfing, which provides reproductive assurance (RA) only when outcrossing is not realized. Although RA is expected to reduce pollinator-mediated selection towards larger flowers, the consequences of delayed selfing for selection on flower size in mixed-mating species remain overlooked. We investigated whether RA weakens selection on flower size in Tuberaria guttata, a mixed-mating annual herb. METHODS We related pollinator visitation rates to flower size and measured seed production in emasculated, hand cross-pollinated and intact (control) flowers in three natural populations. For each population, we estimated variation in PL and RA across individuals differing in flower size and phenotypic selection on this trait. KEY RESULTS Pollinator visitation increased and RA decreased with flower size in all populations. Increasing RA diminished but did not fully alleviate PL, because of early-acting inbreeding depression. In the least-visited and most pollen-limited population, RA increased seed production by >200 %, intensely counteracting the strong pollinator-mediated selection for larger corollas. In the most-visited population, however, RA increased seed production by an average of only 9 %. This population exhibited the largest fraction of individuals that showed a decrease in seed production due to selfing and the weakest pollinator-mediated selection on flower size. CONCLUSIONS The results suggest that the balance between the extent of RA and outcrossing contributes to determine flower size in mixed-mating systems. Pollinator-mediated selection favours larger flowers by increasing outcrossed seeds, but the benefits of RA greatly lessen this effect, especially under severe conditions of pollen limitation. Our findings also indicate that a mixed-mating system can represent an 'evolutionary trap' under an adequate pollinator supply.
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Affiliation(s)
- Alberto L Teixido
- Área de Biodiversidad y Conservación, Universidad Rey Juan Carlos, Madrid, Spain
| | - Marcelo A Aizen
- Grupo de Ecología de la Polinización, Universidad Nacional del Comahue and INIBIOMA-CONICET, Río Negro, Argentina
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7
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Misaki A, Itagaki T, Matsubara Y, Sakai S. Intraflower variation in nectar secretion: Secretion patterns and pollinator behavior in male- and female-phase flowers. AMERICAN JOURNAL OF BOTANY 2018; 105:842-850. [PMID: 29893413 DOI: 10.1002/ajb2.1099] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 02/21/2018] [Indexed: 06/08/2023]
Abstract
PREMISE OF THE STUDY Plants that secrete abundant nectar attract many pollinator visits, potentially leading to a high frequency of geitonogamous pollination. However, intraflower variation in nectar volume might enhance early departure from the flower or inflorescence, reducing geitonogamy. To examine the adaptive significance of multiple nectar-producing spurs within flowers, we related intraflower variation in nectar characteristics to pollinator foraging behavior and plant reproductive success in protandrous Aquilegia buergeriana var. oxysepala. METHODS We investigated if nectar volume and sugar mass relate to spur length and if intraflower variation in nectar characteristics differ between male- and female-phase flowers. Because male function requires more pollinator visits than female function, male-phase flowers are expected to have greater nectar volume and lower intraflower variation in nectar volume than female-phase flowers. We used intraflower variation in spur length as an indicator of variation in nectar characteristics and investigated how spur length variation affects pollinator behavior, pollen removal, and seed production. KEY RESULTS Male-phase flowers had greater nectar volume and lower intraflower variation in nectar volume than female-phase flowers. Intraflower variation in spur length reduced the duration of bumblebee visits. Short visits reduced seed production, but increased pollen removal. CONCLUSIONS Our results suggest that high intraflower variation in nectar production rate can reduce geitonogamy and potentially increase the genetic diversity of pollen received. Such pattern of nectar secretion within and among flowers may allow flowers to ensure effective pollen transfer or high seed production.
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Affiliation(s)
- Ando Misaki
- Graduate School of Life Sciences, Tohoku University, 6-3 Aoba, Sendai, 980-8578, Japan
| | - Tomoyuki Itagaki
- Graduate School of Life Sciences, Tohoku University, 6-3 Aoba, Sendai, 980-8578, Japan
| | - Yutaka Matsubara
- Graduate School of Life Sciences, Tohoku University, 6-3 Aoba, Sendai, 980-8578, Japan
| | - Satoki Sakai
- Graduate School of Life Sciences, Tohoku University, 6-3 Aoba, Sendai, 980-8578, Japan
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Rodger JG, Ellis AG. Distinct effects of pollinator dependence and self-incompatibility on pollen limitation in South African biodiversity hotspots. Biol Lett 2016; 12:rsbl.2016.0253. [PMID: 27277954 DOI: 10.1098/rsbl.2016.0253] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2016] [Accepted: 05/13/2016] [Indexed: 11/12/2022] Open
Abstract
Global synthesis indicates that limitation of plant fecundity by pollen receipt (pollen limitation) is positively related to regional plant diversity and is higher for self-incompatible than self-compatible species. While self-incompatible species are always dependent on pollinating agents, self-compatible species may be pollinator-dependent or autofertile. This should cause variation in pollen limitation among self-compatible species, with lower pollen limitation in autofertile species because they do not depend on pollinators. We hypothesized that the intensity of pollen limitation in self-incompatible compared with pollinator-dependent self-compatible species should depend on whether pollen limitation is determined more by quantity than quality of pollen received. We compared pollen limitation between these three groups using a dataset of 70 biotically pollinated species from biodiverse regions of South Africa. Comparison with a global dataset indicated that pollen limitation in the South African biodiversity hotspots was generally comparable to other regions, despite expectations of higher pollen limitation based on the global plant diversity-pollen limitation relationship. Pollen limitation was lowest for autofertile species, as expected. It was also higher for pollinator-dependent self-compatible species than self-incompatible species, consistent with increased pollen-quality limitation in the former group due to negative consequences of pollinator-mediated self-pollination. However, there was a higher frequency of plants with zygomorphic flowers, which were also more pollen-limited, among pollinator-dependent self-compatible species. Thus, we could not attribute this difference in pollen limitation exclusively to a difference in pollen quality. Nevertheless, our results indicate that comparative studies should control for both pollinator dependence and self-incompatiblity when evaluating effects of other factors on pollen limitation.
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Affiliation(s)
- James G Rodger
- Department of Botany and Zoology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa
| | - Allan G Ellis
- Department of Botany and Zoology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa
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Arceo-Gómez G, Ashman TL. Patterns of pollen quantity and quality limitation of pre-zygotic reproduction inMimulus guttatusvary with co-flowering community context. OIKOS 2014. [DOI: 10.1111/oik.01309] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Gerardo Arceo-Gómez
- Dept of Biological Sciences; Univ. of Pittsburgh; 4249 Fifth Avenue Pittsburgh PA 15260-3929 USA
| | - Tia-Lynn Ashman
- Dept of Biological Sciences; Univ. of Pittsburgh; 4249 Fifth Avenue Pittsburgh PA 15260-3929 USA
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10
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A temporal dimension to the influence of pollen rewards on bee behaviour and fecundity in Aloe tenuior. PLoS One 2014; 9:e94908. [PMID: 24755611 PMCID: PMC3995886 DOI: 10.1371/journal.pone.0094908] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 03/20/2014] [Indexed: 11/19/2022] Open
Abstract
The net effect of pollen production on fecundity in plants can range from negative – when self-pollen interferes with fecundity due to incompatibility mechanisms, to positive – when pollen availability is associated with increased pollinator visitation and fecundity due to its utilization as a reward. We investigated the responses of bees to pollen and nectar rewards, and the effects of these rewards on pollen deposition and fecundity in the hermaphroditic succulent shrub Aloe tenuior. Self-pollinated plants failed to set fruit, but their ovules were regularly penetrated by self-pollen tubes, which uniformly failed to develop into seeds as expected from ovarian self-incompatibility (or strong early inbreeding depression). Bees consistently foraged for pollen during the morning and early afternoon, but switched to nectar in the late afternoon. As a consequence of this differential foraging, we were able to test the relative contribution to fecundity of pollen- versus nectar-collecting flower visitors. We exposed emasculated and intact flowers in either the morning or late afternoon to foraging bees and showed that emasculation reduced pollen deposition by insects in the morning, but had little effect in the afternoon. Despite the potential for self-pollination to result in ovule discounting due to late-acting self-sterility, fecundity was severely reduced in artificially emasculated plants. Although there were temporal fluctuations in reward preference, most bee visits were for pollen rewards. Therefore the benefit of providing pollen that is accessible to bee foragers outweighs any potential costs to fitness in terms of gender interference in this species.
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Li XX, Zou Y, Xiao CL, Gituru RW, Guo YH, Yang CF. The differential contributions of herkogamy and dichogamy as mechanisms of avoiding self-interference in four self-incompatible Epimedium species. J Evol Biol 2013; 26:1949-58. [PMID: 23848603 DOI: 10.1111/jeb.12193] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 04/23/2013] [Accepted: 05/03/2013] [Indexed: 11/30/2022]
Abstract
Self-interference is one of the most important selective forces in shaping floral evolution. Herkogamy and dichogamy both can achieve reductions in the extent of self-interference, but they may have different roles in minimizing self-interference in a single species. We used four self-incompatible Epimedium species to explore the roles of herkogamy and dichogamy in avoiding self-interference and to test the hypothesis that herkogamy and dichogamy may be separated and become selected preferentially in the taxa. Two species (E. franchetii and E. mikinorii) expressed strong herkogamy and weak protogyny (adichogamy), whereas another two species (E. sutchuenense and E. leptorrhizum) expressed slight herkogamy and partial protandry. Field investigations indicated that there was no physical self-interference between male function and female function regarding pollen removal and pollen deposition in all species. Self-pollination (autonomous or facilitated) was greater in species with slight herkogamy than in those with strong herkogamy. Artificial pollination treatments revealed that self-pollination could reduce outcrossed female fertility in all species, and we found evidence that self-interference reduced seed set in E. sutchuenense and E. leptorrhizum in the field, but not in E. franchetii and E. mikinorii. These results indicate that well-developed herkogamy is more effective compared with dichogamy in avoiding self-interference in the four species. In genus Epimedium, herkogamy instead of dichogamy should be selected preferentially and evolved as an effective mechanism for avoiding self-interference and might not need to evolve linked with dichogamy.
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Affiliation(s)
- X-X Li
- College of Life Sciences, Wuhan University, Wuhan, China
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12
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Brys R, Geens B, Beeckman T, Jacquemyn H. Differences in dichogamy and herkogamy contribute to higher selfing in contrasting environments in the annual Blackstonia perfoliata (Gentianaceae). ANNALS OF BOTANY 2013; 111:651-61. [PMID: 23408833 PMCID: PMC3605963 DOI: 10.1093/aob/mct031] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 01/07/2013] [Indexed: 05/23/2023]
Abstract
BACKGROUND AND AIMS The establishment of plant populations in novel environments may generate pronounced shifts in floral traits and plant mating systems, particularly when pollinators are scarce. In this study, floral morphology and mating system functioning are compared between recently established and older populations of the annual plant Blackstonia perfoliata that occur in different pollinator environments. METHODS Hand-pollination and emasculation experiments were conducted to assess the extent of pollinator-mediated pollen deposition and pollen limitation, and the contribution of autonomous selfing to total seed production. Detailed measurements of key floral traits were performed to compare the flower morphology and mating system functioning between plants from both pollination environments. KEY RESULTS Pollinator-mediated pollen deposition was about twice as low in the recently colonized and pollinator-poor environment compared with the old and pollinator-rich sites, but total seed set was little affected by any type of pollen limitation. The contribution of autonomous selfing to total seed production was higher in the pollinator-poor sites than in the pollinator-rich sites (index of reproductive assurance = 0·56 and 0·17, respectively), and seed production was only poorly affected by selfing, whereas in the pollinator-rich populations selfing reduced total reproductive output by about 40 % compared with outcross pollination. Plants originating from pollinator-poor environments produced smaller flowers that showed significantly lower levels of dichogamy (i.e. protogyny) and herkogamy. These reductions resulted in a 2-fold higher capacity for autonomous selfing under pollinator-free conditions (index of autonomous selfing = 0·81 and 0·41 in plants originating from the pollinator-poor and pollinator-rich environment, respectively). CONCLUSIONS The results illustrate that plant populations colonizing novel environments can differ markedly in floral morphology and mating system functioning. Due to a temporal shift in the male phase, the breeding system of B. perfoliata shifted from delayed selfing under pollinator-rich conditions towards competing selfing in recently established populations, providing greater reproductive assurance when pollinators and/or reproductive partners are limited.
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Affiliation(s)
- Rein Brys
- Division of Plant Ecology and Systematics, Biology Department, University of Leuven, Belgium.
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Duffy KJ, Patrick KL, Johnson SD. Emasculation increases seed set in the bird-pollinated hermaphrodite Kniphofia linearifolia (Xanthorrhoeaceae): evidence for sexual conflict? AMERICAN JOURNAL OF BOTANY 2013; 100:622-7. [PMID: 23445825 DOI: 10.3732/ajb.1200531] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
PREMISE OF THE STUDY Hermaphroditism in plants can lead to gender conflicts, such as pollen discounting-the loss of siring opportunities following self-pollination, and ovule discounting-the loss of seed production opportunities when self-pollen tubes disable ovules through early inbreeding depression or late-acting self-incompatibility. If ovules are discounted by self-pollination, it can be predicted that emasculation (removal of self-pollen) should increase seed production, as long as pollinators are not deterred by emasculation. • METHODS Using the hermaphroditic Kniphofia linearifolia, which belongs to a lineage known to possess late-acting self-incompatibility, we performed hand-pollinations with either self- or cross-pollen and recorded pollen tube growth and seed production. We paired experimentally emasculated plants with non-emasculated controls and quantified pollinator visitation rates, fruit, and seed set in both groups. • KEY RESULTS Ovules penetrated by tubes from self-pollen uniformly failed to develop into seeds, as expected from ovarian self-incompatibility (or strong early inbreeding depression). Experimental emasculation had no effect on the rate of visitation by birds, the primary pollinators of this species, but led to increased rejection by bees, which are secondary pollinators. Despite reducing visitation by some pollinators, emasculation led to increased seed production and reduced rates of seed abortion. • CONCLUSIONS These results show that female performance in hermaphroditic flowers can be enhanced when flowers are emasculated, even if the overall number of pollinator visits is decreased. The most likely explanation for this effect of emasculation is that it reduces ovule discounting arising from pollinator-mediated self-pollination.
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Affiliation(s)
- Karl J Duffy
- School of Life Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville, Pietermaritzburg 3209, South Africa.
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Ida TY, Harder LD, Kudo G. Demand-driven resource investment in annual seed production by a perennial angiosperm precludes resource limitation. Ecology 2013; 94:51-61. [DOI: 10.1890/12-0619.1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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15
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Morales CL, Traveset A, Harder LD. Sterile flowers increase pollinator attraction and promote female success in the Mediterranean herb Leopoldia comosa. ANNALS OF BOTANY 2013; 111:103-11. [PMID: 23131298 PMCID: PMC3523656 DOI: 10.1093/aob/mcs243] [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: 05/04/2023]
Abstract
BACKGROUND AND AIMS Large floral displays have opposing consequences for animal-pollinated angiosperms: they attract more pollinators but also enable elevated among-flower self-pollination (geitonogamy). The presence of sterile flowers as pollinator signals may enhance attraction while allowing displays of fewer open fertile flowers, limiting geitonogamy. The simultaneous contributions of fertile and non-fertile display components to pollinator attraction and reproductive output remain undetermined. METHODS The simultaneous effects of the presence of sterile flowers and fertile-flower display size in two populations of Leopoldia comosa were experimentally assessed. Pollinator behaviour, pollen removal and deposition, and fruit and seed production were compared between intact plants and plants with sterile flowers removed. KEY RESULTS The presence of sterile flowers almost tripled pollinator attraction, supplementing the positive effect of the number of fertile flowers on the number of bees approaching inflorescences. Although attracted bees visited more flowers on larger inflorescences, the number visited did not additionally depend on the presence of sterile flowers. The presence of sterile flowers improved all aspects of plant performance, the magnitude of plant benefit being context dependent. During weather favourable to pollinators, the presence of sterile flowers increased pollen deposition on stigmas of young flowers, but this difference was not evident in older flowers, probably because of autonomous self-pollination in poorly visited flowers. Total pollen receipt per stigma decreased with increasing fertile display size. In the population with more pollinators, the presence of sterile flowers increased fruit number but not seed set or mass, whereas in the other population sterile flowers enhanced seeds per fruit, but not fruit production. These contrasts are consistent with dissimilar cross-pollination and autonomous self-pollination, coupled with the strong predispersal inbreeding depression exhibited by L. comosa populations. CONCLUSIONS Sterile flowers enrich pollination quality by promoting pollen export and import, while limiting the mating costs of geitonogamy associated with large fertile displays.
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Affiliation(s)
- Carolina L Morales
- Laboratorio Ecotono, INIBIOMA (UNCOMA-CONICET), Bariloche, Río Negro, Argentina.
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16
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Fernández JD, Bosch J, Nieto-Ariza B, Gómez JM. Pollen limitation in a narrow endemic plant: geographical variation and driving factors. Oecologia 2012; 170:421-31. [PMID: 22492167 DOI: 10.1007/s00442-012-2312-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Accepted: 03/15/2012] [Indexed: 10/28/2022]
Abstract
Pollen limitation may have important consequences for the reproduction and abundance of plant species. It may be especially harmful to endangered and endemic plants with small populations. In this study, we quantify the effect of pollen limitation on seed production and seedling emergence in an endangered narrow endemic crucifer, Erysimum popovii. We conducted a pollen addition experiment across the entire geographic distribution of the species, and explored the effect of pollinator assemblage, plant population size and density, and other habitat variables on pollen limitation intensity in 13 populations. We supplemented flowers in 20 plants per population with allogamous pollen. To account for potential resource reallocation, we used two types of control untreated flowers: internal control flowers from the same individual as the supplemented flowers, and external control flowers from other individuals. Our results indicate that E. popovii is pollen-limited in most of the populations studied, but only through seed production, since pollen supplementation did not enhance seedling emergence. Beefly abundance was associated with among-population differences in pollen limitation intensity. Populations in which beeflies were more abundant were less pollen-limited. In contrast, the abundance of other flower visitors, such as large bees or butterflies, was not associated with pollen limitation. Annual rainfall and bare soil cover were associated with the intensity of pollen limitation across populations.
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Affiliation(s)
- Juande D Fernández
- Department of Ecology, Facultad de Ciencias, University of Granada, Granada, Spain.
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17
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Hargreaves AL, Harder LD, Johnson SD. Floral traits mediate the vulnerability of aloes to pollen theft and inefficient pollination by bees. ANNALS OF BOTANY 2012; 109:761-72. [PMID: 22278414 PMCID: PMC3286288 DOI: 10.1093/aob/mcr324] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Accepted: 12/09/2011] [Indexed: 05/30/2023]
Abstract
BACKGROUND AND AIMS Pollen-collecting bees are among the most important pollinators globally, but are also the most common pollen thieves and can significantly reduce plant reproduction. The pollination efficiency of pollen collectors depends on the frequency of their visits to female(-phase) flowers, contact with stigmas and deposition of pollen of sufficient quantity and quality to fertilize ovules. Here we investigate the relative importance of these components, and the hypothesis that floral and inflorescence characteristics mediate the pollination role of pollen collection by bees. METHODS For ten Aloe species that differ extensively in floral and inflorescence traits, we experimentally excluded potential bird pollinators to quantify the contributions of insect visitors to pollen removal, pollen deposition and seed production. We measured corolla width and depth to determine nectar accessibility, and the phenology of anther dehiscence and stigma receptivity to quantify herkogamy and dichogamy. Further, we compiled all published bird-exclusion studies of aloes, and compared insect pollination success with floral morphology. KEY RESULTS Species varied from exclusively insect pollinated, to exclusively bird pollinated but subject to extensive pollen theft by insects. Nectar inaccessibility and strong dichogamy inhibited pollination by pollen-collecting bees by discouraging visits to female-phase (i.e. pollenless) flowers. For species with large inflorescences of pollen-rich flowers, pollen collectors successfully deposited pollen, but of such low quality (probably self-pollen) that they made almost no contribution to seed set. Indeed, considering all published bird-exclusion studies (17 species in total), insect pollination efficiency varied significantly with floral shape. CONCLUSIONS Species-specific floral and inflorescence characteristics, especially nectar accessibility and dichogamy, control the efficiency of pollen-collecting bees as pollinators of aloes.
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Affiliation(s)
- Anna L Hargreaves
- Department of Biological Sciences, University of Calgary, Alberta, Canada.
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Alonso C, Herrera CM, Ashman TL. A piece of the puzzle: a method for comparing pollination quality and quantity across multiple species and reproductive events. THE NEW PHYTOLOGIST 2012; 193:532-542. [PMID: 22007922 DOI: 10.1111/j.1469-8137.2011.03932.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
• Understanding how pollination affects plant reproductive success and how changes in pollination service affect plant populations, communities and ecosystems is of increasing concern. Yet supplemental hand-pollination traditionally used to assess pollen limitation is prohibitive for large-scale comparative work. Moreover, it does not differentiate between quality and quantity aspects of pollen limitation, and it may suffer from confounds of post-pollination processes such as resource availability to fill seeds. • Here, we highlight pollen tubes as the functional link between pollen arrival and seed production and suggest that consideration of pollen tubes leads to a better depiction of limitation at the pre-zygotic (pollination) phase of sexual reproduction. • We assessed the rigor of piecewise regression to analyze the relationship between the numbers of pollen grains and pollen tubes observed in nonmanipulated wilted flowers. We illustrate how parameters obtained from this analysis provide quantitative insight into the relative relevance of the quantity and quality of pollen receipt in limiting natural pollination success, and can facilitate comparisons among data sets. • This nonmanipulative method opens up new opportunities for rigorous assessment of the relative importance of the quantity and quality of pollination in limiting plant reproduction, especially from a community-wide perspective.
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Affiliation(s)
- Conchita Alonso
- Estación Biológica de Doñana, Consejo Superior de Investigaciones Científicas (CSIC), Sevilla, Spain.
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19
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Fisogni A, Cristofolini G, Rossi M, Galloni M. Pollinator directionality as a response to nectar gradient: promoting outcrossing while avoiding geitonogamy. PLANT BIOLOGY (STUTTGART, GERMANY) 2011; 13:848-856. [PMID: 21972840 DOI: 10.1111/j.1438-8677.2011.00453.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Plants with multiple flowers could be prone to autonomous self-pollination and insect-mediated geitonogamy, but physiological and ecological features have evolved preventing costs related to autogamy. We studied the rare perennial herb Dictamnus albus as a model plant, with the aim of describing the plant-pollinator system from both plant and pollinator perspectives and analysing features that promote outcrossing in an entomophilous species. The breeding system and reproductive success of D. albus were investigated in experimental and natural conditions, showing that it is potentially self-compatible, but only intra-inflorescence insect-mediated selfing is possible. Nectar analysis showed gender-biased production towards the female phase, which follows the male phase, and during flowering, full blooming is found in flowers at the bottom of the raceme. Among a wide spectrum of insect visitors, three genera (Bombus, Apis, Megachile) were found to be principal pollinators. A study of insect behaviour showed a tendency towards bottom-to-top flights for the most important pollinators Bombus spp. and Apis mellifera: upward movements on the racemes could be explained by foraging behaviour, from more to less rewarding flowers. In accordance with the 'declining reward hypothesis', bumblebees and honeybees leave the plant when gain of reward is low, after which few flowers are visited, reducing the chance of self-pollen transfer among flowers. Intra-flower self-pollination is prevented in D. albus by protandry and herkogamy, while the nectar-induced sequential pattern of pollinator visits avoids geitonogamy and tends to maximise pollen export, promoting outcrossing. All these features for preventing selfing benefit plant fitness and population genetic structure.
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Affiliation(s)
- A Fisogni
- Dipartimento Biologia Evoluzionistica Sperimentale, Università di Bologna, Bologna, Italy
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Duffy KJ, Johnson SD. Effects of pollen reward removal on fecundity in a self-incompatible hermaphrodite plant. PLANT BIOLOGY (STUTTGART, GERMANY) 2011; 13:556-60. [PMID: 21489109 DOI: 10.1111/j.1438-8677.2011.00445.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The pollen of hermaphrodite plants is often utilised by flower-visiting animals. While pollen production has obvious benefits for plant male fitness, its consequences for plant female fitness, especially in self-incompatible hermaphrodite species, are less certain. Pollen production could either enhance seed production though increased pollinator attraction, or reduce it if ovules are discounted by deposition of self pollen, as can occur in species with late-acting self-incompatibility. To test the effects of pollen reward provision on female fitness, we artificially emasculated flowers in two populations of the succulent Aloe maculata (Asphodelaceae), which has a late-acting self-incompatibility system, over the course of its flowering period. Flowers of this species are visited by sunbirds (for nectar) and native bees (for pollen and nectar). We measured floral visitation rates, floral rejection rates, pollen deposition on stigmas and fruit and seed set in both emasculated and non-emasculated plants. We found that flowers of emasculated plants suffered reduced visitation and increased rejection (arrival without visitation) by bees, but not by sunbirds; had fewer pollen grains deposited on stigmas and showed an overall decrease in fruit set and seed set. Rates of seed abortion were, however, greatly reduced in emasculated flowers. This study shows that pollen rewards can be important for seed set, even in self-incompatible plants, which have been assumed to rely on nectar rewards for pollinator attraction. Seed abortion was, however, increased by pollen production, a result that highlights the complexity of selection on pollen production in hermaphrodite flowers.
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Affiliation(s)
- K J Duffy
- School of Biological and Conservation Sciences, University of KwaZulu-Natal, Scottsville, Pietermaritzburg, South Africa.
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Dai C, Galloway LF. Do dichogamy and herkogamy reduce sexual interference in a self‐incompatible species? Funct Ecol 2010. [DOI: 10.1111/j.1365-2435.2010.01795.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Laura F. Galloway
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904‐4328, USA
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Vaughton G, Ramsey M, Johnson SD. Pollination and late-acting self-incompatibility in Cyrtanthus breviflorus (Amaryllidaceae): implications for seed production. ANNALS OF BOTANY 2010; 106:547-55. [PMID: 20647225 PMCID: PMC2944973 DOI: 10.1093/aob/mcq149] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 06/01/2010] [Accepted: 06/18/2010] [Indexed: 05/20/2023]
Abstract
BACKGROUND AND AIMS Animal pollination is typically an uncertain process that interacts with self-incompatibility status to determine reproductive success. Seed set is often pollen-limited, but species with late-acting self-incompatibility (SI) may be particularly vulnerable, if self-pollen deposition results in ovule discounting. Pollination is examined and the occurrence of late-acting SI and ovule discounting assessed in Cyrtanthus breviflorus. METHODS The pollination system was characterized by observing floral visitors and assessing nectar production and spectral reflectance of flowers. To assess late-acting SI and ovule discounting, growth of self- and cross-pollen tubes, and seed set following open pollination or hand pollination with varying proportions of self- and cross-pollen, were examined. KEY RESULTS Native honeybees Apis mellifera scutellata pollinated flowers as they actively collected pollen. Most flowers (≥70 %) did not contain nectar, while the rest produced minute volumes of dilute nectar. The flowers which are yellow to humans are visually conspicuous to bees with a strong contrast between UV-reflecting tepals and UV-absorbing anthers and pollen. Plants were self-incompatible, but self-rejection was late-acting and both self- and cross-pollen tubes penetrated ovules. Seed set of open-pollinated flowers was pollen-limited, despite pollen deposition exceeding ovule number by 6-fold. Open-pollinated seed set was similar to that of the cross + self-pollen treatment, but was less than that of the cross-pollen-only treatment. CONCLUSIONS Flowers of C. breviflorus are pollinated primarily by pollen-collecting bees and possess a late-acting SI system, previously unknown in this clade of the Amaryllidaceae. Pollinators of C. breviflorus deposit mixtures of cross- and self-pollen and, because SI is late-acting, self-pollen disables ovules, reducing female fertility. This study thus contributes to growing evidence that seed production in plants with late-acting SI systems is frequently limited by pollen quality, even when pollinators are abundant.
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Affiliation(s)
- Glenda Vaughton
- Botany, University of New England, Armidale, NSW 2351, Australia.
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