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Wessinger CA. How the switch to hummingbird pollination has greatly contributed to our understanding of evolutionary processes. THE NEW PHYTOLOGIST 2024; 241:59-64. [PMID: 37853523 PMCID: PMC10843001 DOI: 10.1111/nph.19335] [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: 08/04/2023] [Accepted: 09/30/2023] [Indexed: 10/20/2023]
Abstract
The evolutionary switch to hummingbird pollination exemplifies complex adaptation, requiring evolutionary change in multiple component traits. Despite this complexity, diverse lineages have converged on hummingbird-adapted flowers on a relatively short evolutionary timescale. Here, I review how features of the genetic basis of adaptation contribute to this remarkable evolutionary lability. Large-effect substitutions, large mutational targets for adaptation, adaptive introgression, and concentrated architecture all contribute to the origin and maintenance of hummingbird-adapted flowers. The genetic features of adaptation are likely shaped by the ecological and geographic context of the switch to hummingbird pollination, with implications for future evolutionary trajectories.
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Affiliation(s)
- Carolyn A Wessinger
- Department of Biological Sciences, University of South Carolina, Columbia, SC, 29208, USA
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2
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Evolution of mixed mating: effects of among-parent variation in early-acting inbreeding depression coupled with overproduction of ovules. J Theor Biol 2022; 550:111241. [DOI: 10.1016/j.jtbi.2022.111241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 06/06/2022] [Accepted: 08/01/2022] [Indexed: 11/19/2022]
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Christie K, Doan JP, Mcbride WC, Strauss SY. Asymmetrical reproductive barriers in sympatric jewelflowers: are floral isolation, genetic incompatibilities and floral trait displacement connected? Biol J Linn Soc Lond 2021. [DOI: 10.1093/biolinnean/blab027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
Floral visitors influence reproductive interactions among sympatric plant species, either by facilitating assortative mating and contributing to reproductive isolation, or by promoting heterospecific pollen transfer, potentially leading to reproductive interference or hybridization. We assessed preference and constancy of floral visitors on two co-occurring jewelflowers [Streptanthus breweri and Streptanthus hesperidis (Brassicaceae)] using field arrays, and quantified two floral rewards potentially important to foraging choice – pollen production and nectar sugar concentration – in a greenhouse common garden. Floral visitors made an abundance of conspecific transitions between S. breweri individuals, which thus experienced minimal opportunities for heterospecific pollen transfer from S. hesperidis. In contrast, behavioural isolation for S. hesperidis was essentially absent due to pollinator inconstancy. This pattern emerged across multiple biotic environments and was unrelated to local density dependence. S. breweri populations that were sympatric with S. hesperidis had higher nectar sugar concentrations than their sympatric congeners, as well as allopatric conspecifics. Previous work shows that S. breweri suffers a greater cost to hybridization than S. hesperidis, and here we find that it also shows asymmetrical floral isolation and floral trait displacement in sympatry. These findings suggest that trait divergence may reduce negative reproductive interactions between sympatric but genetically incompatible relatives.
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Affiliation(s)
- Kyle Christie
- Department of Evolution and Ecology, University of California Davis, One Shields Avenue, Davis, CA, USA
- Center for Population Biology, University of California Davis, One Shields Avenue, Davis, CA, USA
| | - Jonathan P Doan
- Department of Evolution and Ecology, University of California Davis, One Shields Avenue, Davis, CA, USA
| | - Wendy C Mcbride
- Deaver Herbarium, Northern Arizona University, Flagstaff, AZ, USA
| | - Sharon Y Strauss
- Department of Evolution and Ecology, University of California Davis, One Shields Avenue, Davis, CA, USA
- Center for Population Biology, University of California Davis, One Shields Avenue, Davis, CA, USA
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Nelson TC, Stathos AM, Vanderpool DD, Finseth FR, Yuan YW, Fishman L. Ancient and recent introgression shape the evolutionary history of pollinator adaptation and speciation in a model monkeyflower radiation (Mimulus section Erythranthe). PLoS Genet 2021; 17:e1009095. [PMID: 33617525 PMCID: PMC7951852 DOI: 10.1371/journal.pgen.1009095] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 03/11/2021] [Accepted: 01/22/2021] [Indexed: 12/20/2022] Open
Abstract
Inferences about past processes of adaptation and speciation require a gene-scale and genome-wide understanding of the evolutionary history of diverging taxa. In this study, we use genome-wide capture of nuclear gene sequences, plus skimming of organellar sequences, to investigate the phylogenomics of monkeyflowers in Mimulus section Erythranthe (27 accessions from seven species). Taxa within Erythranthe, particularly the parapatric and putatively sister species M. lewisii (bee-pollinated) and M. cardinalis (hummingbird-pollinated), have been a model system for investigating the ecological genetics of speciation and adaptation for over five decades. Across >8000 nuclear loci, multiple methods resolve a predominant species tree in which M. cardinalis groups with other hummingbird-pollinated taxa (37% of gene trees), rather than being sister to M. lewisii (32% of gene trees). We independently corroborate a single evolution of hummingbird pollination syndrome in Erythranthe by demonstrating functional redundancy in genetic complementation tests of floral traits in hybrids; together, these analyses overturn a textbook case of pollination-syndrome convergence. Strong asymmetries in allele sharing (Patterson's D-statistic and related tests) indicate that gene tree discordance reflects ancient and recent introgression rather than incomplete lineage sorting. Consistent with abundant introgression blurring the history of divergence, low-recombination and adaptation-associated regions support the new species tree, while high-recombination regions generate phylogenetic evidence for sister status for M. lewisii and M. cardinalis. Population-level sampling of core taxa also revealed two instances of chloroplast capture, with Sierran M. lewisii and Southern Californian M. parishii each carrying organelle genomes nested within respective sympatric M. cardinalis clades. A recent organellar transfer from M. cardinalis, an outcrosser where selfish cytonuclear dynamics are more likely, may account for the unexpected cytoplasmic male sterility effects of selfer M. parishii organelles in hybrids with M. lewisii. Overall, our phylogenomic results reveal extensive reticulation throughout the evolutionary history of a classic monkeyflower radiation, suggesting that natural selection (re-)assembles and maintains species-diagnostic traits and barriers in the face of gene flow. Our findings further underline the challenges, even in reproductively isolated species, in distinguishing re-use of adaptive alleles from true convergence and emphasize the value of a phylogenomic framework for reconstructing the evolutionary genetics of adaptation and speciation.
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Affiliation(s)
- Thomas C. Nelson
- Division of Biological Sciences, University of Montana, Missoula, Montana, United States of America
| | - Angela M. Stathos
- Division of Biological Sciences, University of Montana, Missoula, Montana, United States of America
| | - Daniel D. Vanderpool
- Division of Biological Sciences, University of Montana, Missoula, Montana, United States of America
| | - Findley R. Finseth
- Division of Biological Sciences, University of Montana, Missoula, Montana, United States of America
| | - Yao-wu Yuan
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, Connecticut, United States of America
| | - Lila Fishman
- Division of Biological Sciences, University of Montana, Missoula, Montana, United States of America
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von Witt CG, Anderson B, Durbach IN, Johnson SD. Breeding systems of floral colour forms in the Drosera cistiflora species complex. PLANT BIOLOGY (STUTTGART, GERMANY) 2020; 22:992-1001. [PMID: 33448582 DOI: 10.1111/plb.13159] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 07/02/2020] [Indexed: 06/12/2023]
Abstract
Variation in plant breeding systems has implications for pollinator-mediated selection on floral traits and the ecology of populations. Here we evaluate pollinator contribution to seed production, self-compatibility and pollen limitation in different floral colour forms of Drosera cistiflora sensu lato (Droseraceae). These insectivorous perennial plants are endemic to fynbos and renosterveld vegetation in the Cape Floristic Region of South Africa, and the species complex includes five floral colour forms (pink, purple, red, white and yellow), some of which are known to be pollinated by beetles. Controlled hand-pollination experiments were conducted in 15 populations of D. cistiflora s.l. (two to four populations per floral colour form) to test whether the colour forms vary in their degree of self-compatibility and their ability to produce seeds through autonomous self-fertilization. Yellow-flowered forms were highly self-incompatible, while other floral colour forms exhibited partial self-compatibility. Seed set resulting from autonomous selfing was very low, and pollinator dependence indices were high in all populations. Since hand cross-pollination resulted in greater seed set than open pollination in 13 of the 15 populations, we inferred that seed production is generally pollen-limited. Drosera cistiflora s.l. typically exhibits high levels of pollinator dependence and pollen limitation. This is unusual among Drosera species worldwide and suggests that pollinators are likely to mediate strong selection on attractive traits such as floral colour and size in D. cistiflora s.l. These results also suggest that the floral colour forms of D. cistiflora s.l. which are rare and threatened are likely to be vulnerable to local extinction if mutualisms were to collapse indefinitely.
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Affiliation(s)
- C G von Witt
- Centre for Functional Biodiversity, School of Life Sciences, University of KwaZulu-Natal, Scottsville, Pietermaritzburg, South Africa
| | - B Anderson
- Department of Botany and Zoology, Stellenbosch University, Matieland, South Africa
| | - I N Durbach
- Centre for Research into Ecological and Environmental Modelling, University of St Andrews, St Andrews, Scotland
- Centre for Statistics in Ecology, the Environment, and Conservation, Department of Statistical Sciences, University of Cape Town, Rondebosch, South Africa
| | - S D Johnson
- Centre for Functional Biodiversity, School of Life Sciences, University of KwaZulu-Natal, Scottsville, Pietermaritzburg, South Africa
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Pollinator divergence and pollination isolation between hybrids with different floral color and morphology in two sympatric Penstemon species. Sci Rep 2020; 10:8126. [PMID: 32415216 PMCID: PMC7229217 DOI: 10.1038/s41598-020-64964-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 04/27/2020] [Indexed: 11/08/2022] Open
Abstract
Differential visitation of pollinators due to divergent floral traits can lead to reproductive isolation via assortative pollen flow, which may ultimately be a driving force in plant speciation, particularly in areas of overlap. We evaluate the effects of pollinator behavioral responses to variation of intraspecific floral color and nectar rewards, on reproductive isolation between two hybrid flower color morphs (fuchsia and blue) and their parental species Penstemon roseus and P. gentianoides with a mixed-pollination system. We show that pollinators (bumblebees and hummingbirds) exhibit different behavioral responses to fuchsia and blue morphs, which could result from differential attraction or deterrence. In addition to differences in color (spectral reflectance), we found that plants with fuchsia flowers produced more and larger flowers, produced more nectar and were more visited by pollinators than those with blue flowers. These differences influenced the foraging behavior and effectiveness as pollinators of both bumblebees and hummingbirds, which contributed to reproductive isolation between the two hybrid flower color morphs and parental species. This study demonstrates how differentiation of pollination traits promotes the formation of hybrid zones leading to pollinator shifts and reproductive isolation. While phenotypic traits of fuchsia and red flowers might encourage more efficient hummingbird pollination in a mixed-pollination system, the costs of bumblebee pollination on plant reproduction could be the drivers for the repeated shifts from bumblebee- to hummingbird-mediated pollination.
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Leal RLB, Moreira MM, Pinto AR, de Oliveira Ferreira J, Rodriguez-Girones M, Freitas L. Temporal changes in the most effective pollinator of a bromeliad pollinated by bees and hummingbirds. PeerJ 2020; 8:e8836. [PMID: 32257647 PMCID: PMC7102499 DOI: 10.7717/peerj.8836] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Accepted: 03/02/2020] [Indexed: 11/20/2022] Open
Abstract
A generalist pollination system may be characterized through the interaction of a plant species with two or more functional groups of pollinators. The spatiotemporal variation of the most effective pollinator is the factor most frequently advocated to explain the emergence and maintenance of generalist pollination systems. There are few studies merging variation in floral visitor assemblages and the efficacy of pollination by different functional groups. Thus, there are gaps in our knowledge about the variation in time of pollinator efficacy and frequency of generalist species. In this study, we evaluated the pollination efficacy of the floral visitors of Edmundoa lindenii (Bromeliaceae) and their frequency of visits across four reproductive events. We analyzed the frequency of the three groups of floral visitors (large bees, small bees, and hummingbirds) through focal observations in the reproductive events of 2015, 2016, 2017, and 2018. We evaluated the pollination efficacy (fecundity after one visit) through selective exposure treatments and the breeding system by manual pollinations. We tested if the reproductive success after natural pollination varied between the reproductive events and also calculated the pollen limitation index. E. lindenii is a self-incompatible and parthenocarpic species, requiring the action of pollinators for sexual reproduction. Hummingbirds had higher efficacy than large bees and small bees acted only as pollen larcenists. The relative frequency of the groups of floral visitors varied between the reproductive events. Pollen limitation has occurred only in the reproductive event of 2017, when visits by hummingbirds were scarce and reproductive success after natural pollination was the lowest. We conclude that hummingbirds and large bees were the main and the secondary pollinators of E. lindenii, respectively, and that temporal variations in the pollinator assemblages had effects on its reproductive success. Despite their lower pollination efficacy, large bees ensured seed set when hummingbirds failed. Thus, we provide evidence that variable pollination environments may favor generalization, even under differential effectiveness of pollinator groups if secondary pollinators provide reproductive assurance.
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Affiliation(s)
| | - Marina Muniz Moreira
- Jardim Botânico do Rio de Janeiro, Rio de Janeiro, Brazil.,Centro de Ciências Agrárias, Universidade Federal do Espírito Santo, Alegre, Espírito Santo, Brazil
| | - Alessandra Ribeiro Pinto
- Programa de Pós-Graduação em Ecologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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Kostyun JL, Gibson MJS, King CM, Moyle LC. A simple genetic architecture and low constraint allow rapid floral evolution in a diverse and recently radiating plant genus. THE NEW PHYTOLOGIST 2019; 223:1009-1022. [PMID: 30972773 DOI: 10.1111/nph.15844] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 04/02/2019] [Indexed: 06/09/2023]
Abstract
Genetic correlations among different components of phenotypes, especially those resulting from pleiotropy, can constrain or facilitate trait evolution. These factors could especially influence the evolution of traits that are functionally integrated, such as those comprising the flower. Indeed, pleiotropy is proposed as a main driver of repeated convergent trait transitions, including the evolution of phenotypically similar pollinator syndromes. We assessed the role of pleiotropy in the differentiation of floral and other reproductive traits between two species - Jaltomata sinuosa and J. umbellata (Solanaceae) - that have divergent suites of floral traits consistent with bee and hummingbird pollination, respectively. To do so, we generated a hybrid population and examined the genetic architecture (trait segregation and quantitative trait locus (QTL) distribution) underlying 25 floral and fertility traits. We found that most floral traits had a relatively simple genetic basis (few, predominantly additive, QTLs of moderate to large effect), as well as little evidence of antagonistic pleiotropy (few trait correlations and QTL colocalization, particularly between traits of different classes). However, we did detect a potential case of adaptive pleiotropy among floral size and nectar traits. These mechanisms may have facilitated the rapid floral trait evolution observed within Jaltomata, and may be a common component of rapid phenotypic change more broadly.
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Affiliation(s)
- Jamie L Kostyun
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA
- Department of Plant Biology, The University of Vermont, Burlington, VT, 05405, USA
| | | | - Christian M King
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA
- Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, OH, 43210, USA
| | - Leonie C Moyle
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA
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