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Wessinger CA. From pollen dispersal to plant diversification: genetic consequences of pollination mode. THE NEW PHYTOLOGIST 2021; 229:3125-3132. [PMID: 33159813 DOI: 10.1111/nph.17073] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 11/02/2020] [Indexed: 06/11/2023]
Abstract
Pollinators influence patterns of plant speciation, and one intuitive hypothesis is that pollinators affect rates of plant diversification through their effects on pollen dispersal. By specifying mating events and pollen flow across the landscape, distinct types of pollinators may cause different opportunities for allopatric speciation. This pollen dispersal-dependent speciation hypothesis predicts that pollination mode has effects on the spatial context of mating events that scale up to impact population structure and rates of species formation. Here I consider recent comparative studies, including genetic analyses of plant mating events, population structure and comparative phylogenetic analyses, to examine evidence for this model. These studies suggest that highly mobile pollinators conduct greater gene flow within and among populations, compared to less mobile pollinators. These differences influence patterns of population structure across the landscape. However, the effects of pollination mode on speciation rates is less predictable. In some contexts, the predicted effects of pollen dispersal are outweighed by other factors that govern speciation rates. A multiscale approach to examine effects of pollination mode on plant mating system, population structure and rates of diversification is key to determining the role of pollen dispersal on plant speciation for model clades.
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Affiliation(s)
- Carolyn A Wessinger
- Department of Biological Sciences, University of South Carolina, Columbia, SC, 27708, USA
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Torres-Vanegas F, Hadley AS, Kormann UG, Jones FA, Betts MG, Wagner HH. The Landscape Genetic Signature of Pollination by Trapliners: Evidence From the Tropical Herb, Heliconia tortuosa. Front Genet 2019; 10:1206. [PMID: 31867039 PMCID: PMC6906188 DOI: 10.3389/fgene.2019.01206] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 10/31/2019] [Indexed: 12/19/2022] Open
Abstract
Animal-mediated pollination is essential for the maintenance of plant reproduction, especially in tropical ecosystems, where pollination networks have been thought to have highly generalized structures. However, accumulating evidence suggests that not all floral visitors provide equally effective pollination services, potentially reducing the number of realized pollinators and increasing the cryptic specialization of pollination networks. Thus, there is a need to understand how different functional groups of pollinators influence pollination success. Here, we examined whether patterns of contemporary pollen-mediated gene flow in Heliconia tortuosa are consistent with the foraging strategy of its territorial or traplining hummingbird pollinators. Territorial hummingbirds defend clumps of flowers and are expected to transfer pollen locally. In contrast, traplining hummingbirds forage across longer distances, thereby increasing pollen flow among forest fragments, and are thought to repeatedly visit particular plants. If trapliners indeed visit the same plants repeatedly along their regular routes, this could lead to a situation where neighboring plants sample genetically distinct pollen pools. To test this hypothesis, we genotyped 720 seeds and 71 mother plants from 18 forest fragments at 11 microsatellite loci. We performed TwoGener analysis to test pollen pool differentiation within sites (among neighboring plants within the same forest fragment: ΦSC) and between sites (among forest fragments: ΦCT). We found strong, statistically significant pollen pool differentiation among neighboring mother plants (ΦSC = 0.0506), and weaker, statistically significant differentiation among sites (ΦCT = 0.0285). We interpret this pattern of hierarchical pollen pool differentiation as the landscape genetic signature of the foraging strategy of traplining hummingbirds, where repeatable, long-distance, and high-fidelity routes transfer pollen among particular plants. Although H. tortuosa is also visited by territorial hummingbirds, our results suggest that these pollinators do not contribute substantially to successful pollination, highlighting differences in realized pollination efficiency. This cryptic reduction in the number of realized pollinators potentially increases the vulnerability of pollination success to the decline of populations of traplining hummingbirds, which have been shown to be sensitive to forest fragmentation. We conclude that maintaining habitat connectivity to sustain the foraging routes of trapliners may be essential for the maintenance of pollen-mediated gene flow in human-modified landscapes.
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Affiliation(s)
- Felipe Torres-Vanegas
- Department of Ecology and Evolutionary Biology, University of Toronto, Mississauga, ON, Canada
| | - Adam S Hadley
- Department of Ecology and Evolutionary Biology, University of Toronto, Mississauga, ON, Canada.,Forest Biodiversity Research Network, Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR, United States
| | - Urs G Kormann
- Swiss Ornithological Institute, Sempach, Switzerland
| | - Frank Andrew Jones
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, United States.,Smithsonian Tropical Research Institute, Panama, Panama
| | - Matthew G Betts
- Forest Biodiversity Research Network, Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR, United States
| | - Helene H Wagner
- Department of Ecology and Evolutionary Biology, University of Toronto, Mississauga, ON, Canada
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Grant EL, Conroy GC, Lamont RW, Reddell PW, Wallace HM, Ogbourne SM. Short distance pollen dispersal and low genetic diversity in a subcanopy tropical rainforest tree, Fontainea picrosperma (Euphorbiaceae). Heredity (Edinb) 2019; 123:503-516. [PMID: 31076650 PMCID: PMC6781113 DOI: 10.1038/s41437-019-0231-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 03/28/2019] [Accepted: 04/24/2019] [Indexed: 11/09/2022] Open
Abstract
Gene flow via pollen movement affects genetic variation in plant populations and is an important consideration in plant domestication. Fontainea picrosperma is a subcanopy rainforest tree that is of commercial interest because it is the source of tigilanol tiglate, a natural product used for the treatment of solid tumors. We identify patterns of pollen-mediated gene flow within natural populations of F. picrosperma and estimate genetic parameters and genetic structure between adult and juvenile groups using microsatellite markers. Our results show pollination events occur over much shorter distances than reported for tropical canopy species. At least 63% of seeds are sired by male trees located within 30 m of the mother. On average, 27% of the local male population contributed to successful reproduction of F. picrosperma with most fathers siring a single seed, however, the contributions to reproduction were uneven. Larger male trees with more flowers had greater reproductive success than those with less flowers (P < 0.05). There were comparatively low levels of genetic variation across the species (HE = 0.405 for adult trees and 0.379 for juveniles) and we found no loss of genetic diversity between adult and juvenile trees. Short distance pollen flow and low genetic diversity is theoretically a prelude to genetic impoverishment, however F. picrosperma has persisted through multiple significant climatic oscillations. Nevertheless, the remaining low genetic diversity is of concern for domestication programs which require maximal genetic diversity to facilitate efficient selective breeding and genetic improvement of this commercially significant species.
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Affiliation(s)
- Elektra L Grant
- GeneCology Research Centre, University of the Sunshine Coast, Sippy Downs, QLD, Australia
| | - Gabriel C Conroy
- GeneCology Research Centre, University of the Sunshine Coast, Sippy Downs, QLD, Australia
| | - Robert W Lamont
- GeneCology Research Centre, University of the Sunshine Coast, Sippy Downs, QLD, Australia
| | | | - Helen M Wallace
- GeneCology Research Centre, University of the Sunshine Coast, Sippy Downs, QLD, Australia
| | - Steven M Ogbourne
- GeneCology Research Centre, University of the Sunshine Coast, Sippy Downs, QLD, Australia.
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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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O'Connell MC, Castilla AR, Lee LX, Jha S. Bee movement across heterogeneous tropical forests: multi‐paternal analyses reveal the importance of neighborhood composition for pollen dispersal. Biotropica 2018. [DOI: 10.1111/btp.12603] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Megan C. O'Connell
- Department of Integrative Biology University of Texas at Austin 1 University Station Austin TX 78712 USA
| | - Antonio R. Castilla
- Department of Integrative Biology University of Texas at Austin 1 University Station Austin TX 78712 USA
- Centro de Ecologia Aplicada Prof. Baeta Neves/InBIO Universidade de Lisboa Tapada da Ajuda 1349‐017 Lisbon Portugal
| | - Leticia X. Lee
- Department of Integrative Biology University of Texas at Austin 1 University Station Austin TX 78712 USA
- Department of Earth and Environment Boston University 685 Commonwealth Avenue Boston MA 02215 USA
| | - Shalene Jha
- Department of Integrative Biology University of Texas at Austin 1 University Station Austin TX 78712 USA
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