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Opedal ØH, Hildesheim LS, Armbruster WS. Evolvability and constraint in the evolution of three-dimensional flower morphology. AMERICAN JOURNAL OF BOTANY 2022; 109:1906-1917. [PMID: 36371715 PMCID: PMC9827957 DOI: 10.1002/ajb2.16092] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 08/25/2022] [Accepted: 08/26/2022] [Indexed: 05/31/2023]
Abstract
PREMISE Flower phenotypes evolve to attract pollinators and to ensure efficient pollen transfer to and from the bodies of pollinators or, in self-compatible bisexual flowers, between anthers and stigmas. If functionally interacting traits are genetically correlated, response to selection may be subject to genetic constraints. Genetic constraints can be assessed by quantifying standing genetic variation in (multivariate) phenotypic traits and by asking how much the available variation is reduced under specific assumptions about phenotypic selection on functionally interacting and genetically correlated traits. METHODS We evaluated multivariate evolvability and potential genetic constraints underlying the evolution of the three-dimensional structure of Dalechampia blossoms. First, we used data from a greenhouse crossing design to estimate the G matrix for traits representing the relative positions of male and female sexual organs (anthers and stigmas) and used the G matrix to ask how genetic variation is distributed in multivariate space. To assess the evolutionary importance of genetic constraints, we related standing genetic variation across phenotypic space to evolutionary divergence of population and species in the same phenotypic directions. RESULTS Evolvabilities varied substantially across phenotype space, suggesting that certain traits or trait combinations may be subject to strong genetic constraint. Traits involved functionally in flower-pollinator fit and autonomous selfing exhibited considerable independent evolutionary potential, but population and species divergence tended to occur in phenotypic directions associated with greater-than-average evolvability. CONCLUSIONS These results are consistent with the hypothesis that genetic constraints can hamper joint trait evolution towards optimum flower-pollinator fit and optimum self-pollination rates.
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Affiliation(s)
| | | | - W. Scott Armbruster
- School of Biological SciencesUniversity of PortsmouthPortsmouthPO1 2DYUK
- Institute of Arctic BiologyUniversity of Alaska FairbanksFairbanksAK99775USA
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Jiménez-Lobato V, Núñez-Farfán J. Mating system of Datura inoxia: association between selfing rates and herkogamy within populations. PeerJ 2021; 9:e10698. [PMID: 33777507 PMCID: PMC7983856 DOI: 10.7717/peerj.10698] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Accepted: 12/13/2020] [Indexed: 11/20/2022] Open
Abstract
Plant mating system determines, to a great extent, the demographic and genetic properties of populations, hence their potential for adaptive evolution. Variation in plant mating system has been documented between phylogenetically related species as well between populations of a species. A common evolutionary transition, from outcrossing to selfing, is likely to occur under environmental spatial variation in the service of pollinators. Here, we studied two phenotypically (in floral traits) and genetically (in neutral molecular markers) differentiated populations of the annual, insect-pollinated, plant Datura inoxia in Mexico, that differ in the service of pollinators (Mapimí and Cañada Moreno). First, we determined the populations’ parameters of phenotypic in herkogamy, outcrossing and selfing rates with microsatellite loci, and assessed between generation (adults and seedlings) inbreeding, and inbreeding depression. Second, we compared the relationships between parameters in each population. Results point strong differences between populations: plants in Mapimí have, on average, approach herkogamy, higher outcrossing rate (tm = 0.68), lower primary selfing rate (r = 0.35), and lower inbreeding at equilibrium (Fe = 0.24) and higher inbreeding depression (δ = 0.25), than the populations of Cañada. Outcrossing seems to be favored in Mapimí while selfing in Cañada. The relationship between r and Fe were negatively associated with herkogamy in Mapimí; here, progenies derived from plants with no herkogamy or reverse herkogamy had higher selfing rate and inbreeding coefficient than plants with approach herkogamy. The difference Fe–F is positively related to primary selfing rate (r) only in Cañada Moreno which suggests inbreeding depression in selfing individuals and then genetic purging. In conclusion, mating system evolution may occur differentially among maternal lineages within populations of Datura inoxia, in which approach herkogamy favors higher outcrossing rates and low levels of inbreeding and inbreeding depression, while no herkogamy or reverse herkogamy lead to the evolution of the “selfing syndrome” following the purge of deleterious alleles despite high inbreeding among individuals.
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Affiliation(s)
- Vania Jiménez-Lobato
- Escuela Superior de Desarrollo Sustentable, Universidad Autónoma de Guerrero, Cátedras CONACYT, México.,Laboratorio de Genética Ecológica y Evolución, Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México, Ciudad de México, Distrito Federal, Mexico
| | - Juan Núñez-Farfán
- Laboratorio de Genética Ecológica y Evolución, Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México, Ciudad de México, Distrito Federal, Mexico
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Albertsen E, Opedal ØH, Bolstad GH, Pérez-Barrales R, Hansen TF, Pélabon C, Armbruster WS. Using ecological context to interpret spatiotemporal variation in natural selection. Evolution 2020; 75:294-309. [PMID: 33230820 DOI: 10.1111/evo.14136] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 09/20/2020] [Accepted: 10/03/2020] [Indexed: 12/14/2022]
Abstract
Spatiotemporal variation in natural selection is expected, but difficult to estimate. Pollinator-mediated selection on floral traits provides a good system for understanding and linking variation in selection to differences in ecological context. We studied pollinator-mediated selection in five populations of Dalechampia scandens (Euphorbiaceae) in Costa Rica and Mexico. Using a nonlinear path-analytical approach, we assessed several functional components of selection, and linked variation in pollinator-mediated selection across time and space to variation in pollinator assemblages. After correcting for estimation error, we detected moderate variation in net selection on two out of four blossom traits. Both the opportunity for selection and the mean strength of selection decreased with increasing reliability of cross-pollination. Selection for pollinator attraction was consistently positive and stronger on advertisement than reward traits. Selection on traits affecting pollen transfer from the pollinator to the stigmas was strong only when cross-pollination was unreliable and there was a mismatch between pollinator and blossom size. These results illustrate how consideration of trait function and ecological context can facilitate both the detection and the causal understanding of spatiotemporal variation in natural selection.
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Affiliation(s)
- Elena Albertsen
- Norwegian Institute for Bioeconomy Research, Trondheim, 7031, Norway.,Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, Trondheim, 7491, Norway
| | - Øystein H Opedal
- Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, Trondheim, 7491, Norway.,Department of Biology, Lund University, Lund, SE-22362, Sweden
| | - Geir H Bolstad
- Norwegian Institute for Nature Research (NINA), Trondheim, 7485, Norway
| | - Rocío Pérez-Barrales
- School of Biological Sciences, University of Portsmouth, Portsmouth, PO1 2DY, United Kingdom
| | - Thomas F Hansen
- Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, Oslo, 0316, Norway
| | - Christophe Pélabon
- Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, Trondheim, 7491, Norway
| | - W Scott Armbruster
- School of Biological Sciences, University of Portsmouth, Portsmouth, PO1 2DY, United Kingdom.,Institute of Arctic Biology, University of Alaska, Fairbanks, Alaska, 99775, USA
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Hildesheim LS, Opedal ØH, Armbruster WS, Pélabon C. Quantitative and qualitative consequences of reduced pollen loads in a mixed-mating plant. Ecol Evol 2019; 9:14253-14260. [PMID: 31938516 PMCID: PMC6953568 DOI: 10.1002/ece3.5858] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 10/16/2019] [Accepted: 10/23/2019] [Indexed: 12/25/2022] Open
Abstract
Greater pollination intensity can enhance maternal plant fitness by increasing seed set and seed quality as a result of more intense pollen competition or enhanced genetic sampling. We tested experimentally these effects by varying the pollen load from a single pollen donor on stigmas of female flowers of Dalechampia scandens (Euphorbiaceae) and measuring the effects on seed number and seed mass. Seed set increased rapidly with pollen number at low to moderate pollen loads, and a maximum set of three seeds occurred with a mean pollen load of 19 pollen grains. We did not detect a trade-off between the number of seeds and seed mass within a fruit. Seed mass increased with increasing pollen load, supporting the hypothesis of enhanced seed quality via increased pollen-competition intensity or genetic sampling. These results suggest that maternal fitness increases with larger pollen loads, even when the fertilization success is already high. Our results further highlight the importance of high rates of pollen arrival onto stigmas, as mediated by reliable pollinators. Comparing the pollen-to-seed response curve obtained in this experiment with those observed in natural populations suggests that pollen limitation may be more severe in natural populations than predicted from greenhouse studies. These results also indicate that declines in pollinator abundance may decrease plant fitness through lowered seed quality before an effect on seed set is detected.
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Affiliation(s)
- Laura S. Hildesheim
- Department of BiologyCentre for Biodiversity DynamicsNorwegian University of Science and TechnologyNTNUTrondheimNorway
- Department of Biological SciencesUniversity of BergenBergenNorway
| | - Øystein H. Opedal
- Department of BiologyCentre for Biodiversity DynamicsNorwegian University of Science and TechnologyNTNUTrondheimNorway
| | - W. Scott Armbruster
- School of Biological SciencesUniversity of PortsmouthPortsmouthUK
- Institute of Arctic BiologyUniversity of AlaskaFairbanksAKUSA
| | - Christophe Pélabon
- Department of BiologyCentre for Biodiversity DynamicsNorwegian University of Science and TechnologyNTNUTrondheimNorway
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Hildesheim LS, Opedal ØH, Armbruster WS, Pélabon C. Fitness costs of delayed pollination in a mixed-mating plant. ANNALS OF BOTANY 2019; 124:869-881. [PMID: 31504153 PMCID: PMC6868360 DOI: 10.1093/aob/mcz141] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 08/14/2019] [Indexed: 06/01/2023]
Abstract
BACKGROUND AND AIMS To predict the evolutionary consequences of pollinator declines, we need to understand the evolution of delayed autonomous self-pollination, which is expected to evolve as a mechanism of reproductive assurance when cross-pollination becomes unreliable. This involves estimating the costs of increased levels of selfing as well as those associated with floral senescence. METHODS We studied the mechanisms and costs of delayed self-pollination in the mixed-mating vine Dalechampia scandens (Euphorbiaceae) by first assessing among-population variation in herkogamy and dichogamy, which together determine the rate and timing of autonomous self-pollination. We then tested whether floral longevity responds plastically to delayed pollination. Finally, we assessed the costs of delayed self-pollination in terms of seed number and size, explicitly separating inbreeding depression from effects of floral senescence. KEY RESULTS Herkogamy varied extensively, while variation in dichogamy was more limited. Unpollinated blossoms increased their longevity, but seed quantity and quality decreased with increasing delays in pollination, independently of inbreeding depression. CONCLUSIONS In D. scandens, earlier autonomous selfing is facilitated by reduced herkogamy rather than reduced protogyny, providing reproductive assurance while maintaining the possibility for outcrossing events. Effective early autonomous self-pollination may evolve under reduced cross-pollination reliability in response to costs associated with floral senescence.
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Affiliation(s)
- Laura S Hildesheim
- Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, NTNU, Trondheim, Norway
| | - Øystein H Opedal
- Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, NTNU, Trondheim, Norway
- Research Centre for Ecological Change, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - W Scott Armbruster
- School of Biological Sciences, King Henry Building, King Henry I Street, University of Portsmouth, Portsmouth, UK
- Institute of Arctic Biology, University of Alaska, Fairbanks, AK, USA
| | - Christophe Pélabon
- Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, NTNU, Trondheim, Norway
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Opedal ØH, Albertsen E, Pérez-Barrales R, Armbruster WS, Pélabon C. No evidence that seed predators constrain pollinator-mediated trait evolution in a tropical vine. AMERICAN JOURNAL OF BOTANY 2019; 106:145-153. [PMID: 30625241 DOI: 10.1002/ajb2.1209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 10/15/2018] [Indexed: 06/09/2023]
Abstract
PREMISE OF THE STUDY Turnover in biotic communities across heterogeneous landscapes is expected to lead to variation in interactions among plants, their mutualists, and their antagonists. Across a fragmented landscape in northern Costa Rica, populations of the euphorb vine Dalechampia scandens vary widely in mating systems and associated blossom traits. Previous work suggested that populations are well adapted to the local reliability of pollination by apid and megachilid bees. We tested whether variation in the intensity of predispersal seed predation by seed weevils in the genus Nanobaris also contributes to the observed variation in blossom traits. METHODS We studied spatiotemporal variation in the relationships between floral advertisement and the probability of seed predation within three focal populations. Then we assessed among-population covariation of predation rate, pollination reliability, mating system, and blossom traits across 20 populations. KEY RESULTS The probability of seed predation was largely unrelated to variation in floral advertisement both within focal populations and among the larger sample of populations. The rate of seed predation was only weakly associated with the rate of cross-pollination (allogamy) in each population but tended to be proportionally greater in populations experiencing less reliable pollination. CONCLUSIONS These results suggest that geographic variation in the intensity of antagonistic interactions have had only minor modifying effects on the evolutionary trajectories of floral advertisement in plant populations in this system. Thus, pollinator-driven floral trait evolution in D. scandens in the study area appears not to be influenced by conflicting seed-predator-mediated selection.
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Affiliation(s)
- Øystein H Opedal
- Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, NTNU, 7491, Trondheim, Norway
| | - Elena Albertsen
- Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, NTNU, 7491, Trondheim, Norway
| | - Rocío Pérez-Barrales
- School of Biological Sciences, University of Portsmouth, King Henry Building, King Henry I Street, Portsmouth, PO1 2DY, UK
| | - W Scott Armbruster
- School of Biological Sciences, University of Portsmouth, King Henry Building, King Henry I Street, Portsmouth, PO1 2DY, UK
- Institute of Arctic Biology, University of Alaska, Fairbanks, Alaska, 99775, USA
| | - Christophe Pélabon
- Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, NTNU, 7491, Trondheim, Norway
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Intersexual conflict over seed size is stronger in more outcrossed populations of a mixed-mating plant. Proc Natl Acad Sci U S A 2018; 115:11561-11566. [PMID: 30282740 DOI: 10.1073/pnas.1810979115] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
In polyandrous species, fathers benefit from attracting greater maternal investment toward their offspring at the expense of the offspring of other males, while mothers should usually allocate resources equally among offspring. This conflict can lead to an evolutionary arms race between the sexes, manifested through antagonistic genes whose expression in offspring depends upon the parent of origin. The arms race may involve an increase in the strength of maternally versus paternally derived alleles engaged in a "tug of war" over maternal provisioning or repeated "recognition-avoidance" coevolution where growth-enhancing paternally derived alleles evolve to escape recognition by maternal genes targeted to suppress their effect. Here, we develop predictions to distinguish between these two mechanisms when considering crosses among populations that have reached different equilibria in this intersexual arms race. We test these predictions using crosses within and among populations of Dalechampia scandens (Euphorbiaceae) that presumably have experienced different intensities of intersexual conflict, as inferred from their historical differences in mating system. In crosses where the paternal population was more outcrossed than the maternal population, hybrid seeds were larger than those normally produced in the maternal population, whereas when the maternal population was more outcrossed, hybrid seeds were smaller than normal. These results confirm the importance of mating systems in determining the intensity of intersexual conflict over maternal investment and provide strong support for a tug-of-war mechanism operating in this conflict. They also yield clear predictions for the fitness consequences of gene flow among populations with different mating histories.
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The evolvability of herkogamy: Quantifying the evolutionary potential of a composite trait. Evolution 2017; 71:1572-1586. [DOI: 10.1111/evo.13258] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 04/21/2017] [Indexed: 12/18/2022]
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Opedal ØH, Albertsen E, Armbruster WS, Pérez-Barrales R, Falahati-Anbaran M, Pélabon C. Evolutionary consequences of ecological factors: pollinator reliability predicts mating-system traits of a perennial plant. Ecol Lett 2016; 19:1486-1495. [DOI: 10.1111/ele.12701] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 10/14/2016] [Indexed: 12/23/2022]
Affiliation(s)
- Øystein H. Opedal
- Centre for Biodiversity Dynamics; Department of Biology; Norwegian University of Science and Technology, NTNU; 7491 Trondheim Norway
| | - Elena Albertsen
- Centre for Biodiversity Dynamics; Department of Biology; Norwegian University of Science and Technology, NTNU; 7491 Trondheim Norway
| | - W. Scott Armbruster
- School of Biological Sciences; University of Portsmouth; King Henry Building, King Henry I Street Portsmouth PO1 2DY UK
- Department of Biology; Norwegian University of Science and Technology, NTNU; 7491 Trondheim Norway
- Institute of Arctic Biology; University of Alaska; Fairbanks AK 99775 USA
| | - Rocío Pérez-Barrales
- School of Biological Sciences; University of Portsmouth; King Henry Building, King Henry I Street Portsmouth PO1 2DY UK
| | - Mohsen Falahati-Anbaran
- School of Biology and Center of Excellence in Phylogeny of Living Organisms; University of Tehran; 14155-6455 Tehran Iran
| | - Christophe Pélabon
- Centre for Biodiversity Dynamics; Department of Biology; Norwegian University of Science and Technology, NTNU; 7491 Trondheim Norway
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