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Makowski H, Lamb K, Galloway LF. Support for Baker's law: Facultative self-fertilization ability decreases pollen limitation in experimental colonization. AMERICAN JOURNAL OF BOTANY 2024; 111:e16351. [PMID: 38812263 DOI: 10.1002/ajb2.16351] [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: 12/29/2023] [Revised: 03/13/2024] [Accepted: 03/14/2024] [Indexed: 05/31/2024]
Abstract
PREMISE The ability to self-fertilize is predicted to provide an advantage in colonization because a single individual can reproduce and establish a next generation in a new location regardless of the density of mates. While there is theoretical and correlative support for this idea, the strength of mate limitation as a selective agent has not yet been delineated from other factors that can also select for self-fertilization in colonization of new habitats. We used known mating-system variation in the American bellflower (Campanula americana) to explore how plants' ability to self-fertilize can mitigate density-dependent reproduction and impact colonization success. METHODS We created experimental populations of single individuals or a small number of plants to emulate isolated colonization events. These populations were composed of plants that differed in their ability to self-fertilize. We compared pollen limitation of the single individuals to that of small populations. RESULTS Experimental populations of plants that readily self-fertilize produced consistent seed numbers regardless of population size, whereas plants with lower ability to self-fertilize had density-dependent reproduction with greater seed production in small populations than in populations composed of a single individual. CONCLUSIONS We experimentally isolated the effect of mate limitation in colonization and found that it can select for increased self-fertilization. We show the benefit of self-fertilization in colonization, which helps to explain geographic patterns of self-fertilization and shows support for Baker's law, a long-held hypothesis in the field of mating-system evolution.
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Affiliation(s)
- Hanna Makowski
- Department of Biology, University of Virginia, PO Box 400328, Charlottesville, 22904, Virginia, USA
- Black Rock Forest, 65 Reservoir Road, Cornwall, New York, 12518, USA
| | - Keric Lamb
- Department of Biology, University of Virginia, PO Box 400328, Charlottesville, 22904, Virginia, USA
| | - Laura F Galloway
- Department of Biology, University of Virginia, PO Box 400328, Charlottesville, 22904, Virginia, USA
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2
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Burnette TE, Eckhart VM. Evolutionary divergence of potential drought adaptations between two subspecies of an annual plant: Are trait combinations facilitated, independent, or constrained? AMERICAN JOURNAL OF BOTANY 2021; 108:309-319. [PMID: 33524185 PMCID: PMC7986167 DOI: 10.1002/ajb2.1607] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 10/14/2020] [Indexed: 05/17/2023]
Abstract
PREMISE Whether drought-adaptation mechanisms tend to evolve together, evolve independently, or evolve constrained by genetic architecture is incompletely resolved, particularly for water-relations traits besides gas exchange. We addressed this issue in two subspecies of Clarkia xantiana (Onagraceae), California winter annuals that separated approximately 65,000 years ago and are adapted, partly by differences in flowering time, to native ranges differing in precipitation. METHODS In these subspecies and in recombinant inbred lines (RILs) from a cross between them, we scored traits related to drought adaptation (timing of seed germination and of flowering, succulence, pressure-volume curve variables) in common environments. RESULTS The subspecies native to more arid environments (parviflora) exhibited slower seed germination in saturated conditions, earlier flowering, and greater succulence, likely indicating superior drought avoidance, drought escape, and dehydration resistance via water storage. The other subspecies (xantiana) had lower osmotic potential at full turgor and lower water potential at turgor loss, implying superior dehydration tolerance. Genetic correlations among RILs suggest facilitated evolution of some trait combinations and independence of others. Where genetic correlations exist, subspecies differences fell along them, with the exception of differences in succulence and turgor loss point. In that case, subspecies difference overcame genetic correlations, possibly reflecting strong selection and/or antagonistic genetic correlations with other traits. CONCLUSIONS Clarkia xantiana subspecies' differ in multiple mechanisms of drought adaptation. Genetic architecture generally does not seem to have constrained the evolution of these mechanisms, and it may have facilitated the evolution of some of trait combinations.
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Affiliation(s)
- Timothy E. Burnette
- Division of Biological SciencesUniversity of MontanaMissoulaMT59802USA
- Department of BiologyGrinnell CollegeGrinnellIA50112USA
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3
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Akiyama R, Milosavljevic S, Leutenegger M, Shimizu-Inatsugi R. Trait-dependent resemblance of the flowering phenology and floral morphology of the allopolyploid Cardamine flexuosa to those of the parental diploids in natural habitats. JOURNAL OF PLANT RESEARCH 2020; 133:147-155. [PMID: 31925575 PMCID: PMC7026219 DOI: 10.1007/s10265-019-01164-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Accepted: 12/08/2019] [Indexed: 05/24/2023]
Abstract
Allopolyploids possess complete sets of genomes derived from different parental species and exhibit a range of variation in various traits. Reproductive traits may play a key role in the reproductive isolation between allopolyploids and their parental species, thus affecting the thriving of allopolyploids. However, empirical data, especially in natural habitats, comparing reproductive trait variation between allopolyploids and their parental species remain rare. Here, we documented the flowering phenology and floral morphology of the allopolyploid wild plant Cardamine flexuosa and its diploid parents C. amara and C. hirsuta in their native range in Switzerland. The flowering of C. flexuosa started at an intermediate time compared with those of the parents and the flowering period of C. flexuosa overlapped with those of the parents. Cardamine flexuosa resembled C. hirsuta in the size of flowers and petals and the length/width ratio of petals, while it resembled C. amara in the length/width ratio of flowers. These results provide empirical evidence of the trait-dependent variation of allopolyploid phenotypes in natural habitats at the local scale. They also suggest that the variation in some reproductive traits in C. flexuosa is associated with self-fertilization. Therefore, it is helpful to consider the mating system in furthering the understanding of the processes that may have shaped trait variation in polyploids in nature.
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Affiliation(s)
- Reiko Akiyama
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrase 190, 8057, Zurich, Switzerland
| | - Stefan Milosavljevic
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrase 190, 8057, Zurich, Switzerland
| | - Matthias Leutenegger
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrase 190, 8057, Zurich, Switzerland
| | - Rie Shimizu-Inatsugi
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrase 190, 8057, Zurich, Switzerland.
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Chang H, Sun F. Temporal Distinction between Male and Female Floral Organ Development in Nicotiana tabacum cv. Xanthi (Solanaceae). PLANTS (BASEL, SWITZERLAND) 2020; 9:E127. [PMID: 31963844 PMCID: PMC7020162 DOI: 10.3390/plants9010127] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 01/16/2020] [Accepted: 01/17/2020] [Indexed: 01/13/2023]
Abstract
Early floral developmental investigations provide crucial evidence for phylogenetic and molecular studies of plants. The developmental and evolutionary mechanisms underlying the variations in floral organs are critical for a thorough understanding of the diversification of flowers. Ontogenetic comparisons between anthers and pistil within single flowers were characterized over time in Nicotiana tabacum cv. Xanthi. The ages of 42 tobacco flower or flower primordia were estimated using corolla growth analysis. Results showed that the protodermal layer in carpel primordia contributes to carpel development by both anticlinal and periclinal divisions. Periclinal divisions in the hypodermal layer of the placenta were observed around 4.8 ± 1.3 days after the formation of early carpel primordia (ECP) and ovule initiation occurred 10.0 ± 0.5 days after ECP. Meiosis in anthers and ovules began about 8.9 ± 1.1 days and 14.4 ± 1.3 days after ECP, respectively. Results showed an evident temporal distinction between megasporogenesis and microsporogenesis. Flower ages spanned a 17-day interval, starting with flower primordia containing the ECP and anther primordia to the tetrad stage of meiosis in megasporocytes and the bicellular stage in pollen grains. These results establish a solid foundation for future studies in order to identify the developmental and molecular mechanisms responsible for the mating system in tobacco.
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Affiliation(s)
- Hongli Chang
- Shaanxi Key Laboratory for Animal Conservation, School of Life Sciences, Northwest University, Xi’an 710069, China;
| | - Fengjie Sun
- School of Science and Technology, Georgia Gwinnett College, Lawrenceville, GA 30043, USA
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5
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Malagon DA, Roche MD, McElderry RM, Kalisz S. Pollen performance decreases with plant age for outcrosser but not selfer: evidence for cost of male performance. AMERICAN JOURNAL OF BOTANY 2019; 106:1271-1278. [PMID: 31442320 DOI: 10.1002/ajb2.1346] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2019] [Accepted: 06/19/2019] [Indexed: 06/10/2023]
Abstract
PREMISE Declines in reproductive capabilities with increasing age are common across the tree of life. However, in plants, mating system traits have rarely been tested for signs of senescence. Since reproduction is often resource limited, we might expect outcrossing and selfing taxa to allocate these resources differently, especially as a plant ages. Compared with selfers, outcrossers are expected to produce showy, rewarding flowers that attract pollinators and high-quality pollen that can successfully compete for ovules. Yet, this resource-intensive strategy of outcrossers may result in declines in floral allocation and pollen performance metrics, relative to selfers. METHODS To explore age-related changes in reproduction, we measured flower size and pollen germinability over the flowering period for multiple populations of an annual sister species pair, Collinsia linearis (outcrosser) and C. rattanii (selfer), in a growth chamber experiment. RESULTS We found that flower size decreased significantly with age in both species. The outcrosser expressed a significant and dramatic (88%) decline in pollen germinability with age, while the selfer's pollen germinability decline was non-significant and low (17%). CONCLUSIONS Our results support the idea that the higher total cost of reproduction in outcrossers can deplete available resources more rapidly than in selfers, manifesting as a decline in male performance with plant age.
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Affiliation(s)
- Daniel A Malagon
- Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Tennessee, 37996, USA
| | - Morgan D Roche
- Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Tennessee, 37996, USA
| | - Robert M McElderry
- Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Tennessee, 37996, USA
| | - Susan Kalisz
- Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Tennessee, 37996, USA
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Emms SK, Hove AA, Dudley LS, Mazer SJ, Verhoeven AS. Could seasonally deteriorating environments favour the evolution of autogamous selfing and a drought escape physiology through indirect selection? A test of the time limitation hypothesis using artificial selection in Clarkia. ANNALS OF BOTANY 2018; 121:753-766. [PMID: 29351591 PMCID: PMC5853010 DOI: 10.1093/aob/mcx197] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Accepted: 12/08/2017] [Indexed: 05/25/2023]
Abstract
BACKGROUND AND AIMS The evolution of selfing from outcrossing may be the most common transition in plant reproductive systems and is associated with a variety of ecological circumstances and life history strategies. The most widely discussed explanation for these associations is the reproductive assurance hypothesis - the proposition that selfing is favoured because it increases female fitness when outcross pollen receipt is limited. Here an alternative explanation, the time limitation hypothesis, is addressed, one scenario of which proposes that selfing may evolve as a correlated response to selection for a faster life cycle in seasonally deteriorating environments. METHODS Artificial selection for faster maturation (early flowering) or for low herkogamy was performed on Clarkia unguiculata (Onagraceae), a largely outcrossing species whose closest relative, C. exilis, has evolved higher levels of autogamous selfing. Direct responses to selection and correlated evolutionary changes in these traits were measured under greenhouse conditions. Direct responses to selection on early flowering and correlated evolutionary changes in the node of the first flower, herkogamy, dichogamy, gas exchange rates and water use efficiency (WUE) were measured under field conditions. KEY RESULTS Lines selected for early flowering and for low herkogamy showed consistent, statistically significant responses to direct selection. However, there was little or no evidence of correlated evolutionary changes in flowering date, floral traits, gas exchange rates or WUE. CONCLUSIONS These results suggest that the maturation rate and mating system have evolved independently in Clarkia and that the time limitation hypothesis does not explain the repeated evolution of selfing in this genus, at least through its indirect selection scenario. They also suggest that the life history and physiological components of drought escape are not genetically correlated in Clarkia, and that differences in gas exchange physiology between C. unguiculata and C. exilis have evolved independently of differences in mating system and life history.
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Affiliation(s)
- Simon K Emms
- Department of Biology, University of St. Thomas, Saint Paul, MN, USA
| | - Alisa A Hove
- Department of Biology, Warren Wilson College, Asheville, NC, USA
| | - Leah S Dudley
- Department of Biology, University of Wisconsin-Stout, Menomonie, WI, USA
| | - Susan J Mazer
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA
| | - Amy S Verhoeven
- Department of Biology, University of St. Thomas, Saint Paul, MN, USA
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Mazer SJ, Hendrickson BT, Chellew JP, Kim LJ, Liu JW, Shu J, Sharma MV. Divergence in pollen performance between Clarkia sister species with contrasting mating systems supports predictions of sexual selection. Evolution 2018; 72:453-472. [PMID: 29359333 DOI: 10.1111/evo.13429] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Revised: 01/07/2018] [Accepted: 01/09/2018] [Indexed: 12/22/2022]
Abstract
Animal taxa that differ in the intensity of sperm competition often differ in sperm production or swimming speed, arguably due to sexual selection on postcopulatory male traits affecting siring success. In plants, closely related self- and cross-pollinated taxa similarly differ in the opportunity for sexual selection among male gametophytes after pollination, so traits such as the proportion of pollen on the stigma that rapidly enters the style and mean pollen tube growth rate (PTGR) are predicted to diverge between them. To date, no studies have tested this prediction in multiple plant populations under uniform conditions. We tested for differences in pollen performance in greenhouse-raised populations of two Clarkia sister species: the predominantly outcrossing C. unguiculata and the facultatively self-pollinating C. exilis. Within populations of each taxon, groups of individuals were reciprocally pollinated (n = 1153 pollinations) and their styles examined four hours later. We tested for the effects of species, population, pollen type (self vs. outcross), the number of competing pollen grains, and temperature on pollen performance. Clarkia unguiculata exhibited higher mean PTGR than C. exilis; pollen type had no effect on performance in either taxon. The difference between these species in PTGR is consistent with predictions of sexual selection theory.
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Affiliation(s)
- Susan J Mazer
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California 93106
| | - Brandon T Hendrickson
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California 93106
| | - Joseph P Chellew
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California 93106
| | - Lynn J Kim
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California 93106
| | - Jasen W Liu
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California 93106
| | - Jasper Shu
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California 93106
| | - Manju V Sharma
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California 93106
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8
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Lankinen Å, Hydbom S. Effects of soil resources on expression of a sexual conflict over timing of stigma receptivity in a mixed-mating plant. OIKOS 2016. [DOI: 10.1111/oik.03749] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Åsa Lankinen
- Plant Protection Biology; Swedish Univ. of Agricultural Sciences; PO Box 102 SE-230 53 Alnarp Sweden
| | - Sofia Hydbom
- Plant Protection Biology; Swedish Univ. of Agricultural Sciences; PO Box 102 SE-230 53 Alnarp Sweden
- Dept of Biology; Lund University; Ecology Building Lund Sweden
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Ivey CT, Dudley LS, Hove AA, Emms SK, Mazer SJ. Outcrossing and photosynthetic rates vary independently within two Clarkia species: implications for the joint evolution of drought escape physiology and mating system. ANNALS OF BOTANY 2016; 118:897-905. [PMID: 27443300 PMCID: PMC5055815 DOI: 10.1093/aob/mcw134] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 05/19/2016] [Indexed: 05/11/2023]
Abstract
Background and Aims Mating systems of plants are diverse and evolutionarily labile. Abiotic environmental factors, such as seasonal drought, may impose selection on physiological traits that could lead to transitions in mating system if physiological traits are genetically correlated with traits that influence mating system. Within Clarkia, self-fertilizing taxa have higher photosynthetic rates, earlier flowering phenology, faster individual floral development and more compressed flowering periods than their outcrossing sister taxa, potentially reducing the selfing taxa's exposure to drought. In theory, this contrast in trait combinations between sister taxa could have arisen via correlated evolution due to pleiotropy or genetic linkage. Alternatively, each trait may evolve independently as part of a life history that is adaptive in seasonally dry environments. Methods To evaluate these hypotheses, we examined relationships between photosynthetic rates (adjusted for plant height and leaf node position) and outcrossing rates (estimated by allozyme variation in progeny arrays) during two consecutive years in multiple wild populations of two mixed-mating Clarkia taxa, each of which is sister to a derived selfing taxon. If the negative association between photosynthetic rate and outcrossing previously observed between sister taxa reflects correlated evolution due to a strong negative genetic correlation between these traits, then a similarly negative relationship would be observed within populations of each taxon. By contrast, if the combination of elevated photosynthetic rates and reduced outcrossing evolved independently within taxa, we predicted no consistent relationship between photosynthetic rate and outcrossing rate. Key Results We found no significant difference in outcrossing rates within populations between groups of plants with high versus low photosynthetic rates. Conclusions Overall, these results provide support for the hypothesis that the joint divergence in photosynthetic rate and mating system observed between Clarkia sister taxa is the result of independent evolutionary transitions.
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Affiliation(s)
- Christopher T. Ivey
- California State University, Chico, CA 95929-0515, USA
- *For correspondence. E-mail
| | - Leah S. Dudley
- University of Wisconsin, Stout, Menomonie, WI 54751, USA
| | - Alisa A. Hove
- Warren Wilson College, Asheville, NC 28815-6217, USA
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Poullet N, Vielle A, Gimond C, Carvalho S, Teotónio H, Braendle C. Complex heterochrony underlies the evolution of Caenorhabditis elegans
hermaphrodite sex allocation. Evolution 2016; 70:2357-2369. [DOI: 10.1111/evo.13032] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 07/30/2016] [Accepted: 08/02/2016] [Indexed: 12/21/2022]
Affiliation(s)
- Nausicaa Poullet
- Université Nice Sophia Antipolis, CNRS, Inserm; IBV; Parc Valrose 06100 Nice France
| | - Anne Vielle
- Université Nice Sophia Antipolis, CNRS, Inserm; IBV; Parc Valrose 06100 Nice France
| | - Clotilde Gimond
- Université Nice Sophia Antipolis, CNRS, Inserm; IBV; Parc Valrose 06100 Nice France
| | - Sara Carvalho
- Instituto Gulbenkian de Ciência; Apartado 14 P-2781-901 Oeiras Portugal
| | - Henrique Teotónio
- Institut de Biologie; École Normale Supérieure; CNRS UMR 8197, INSERM U1024 F-75005 Paris France
| | - Christian Braendle
- Université Nice Sophia Antipolis, CNRS, Inserm; IBV; Parc Valrose 06100 Nice France
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Schneider HE, Mazer SJ. Geographic variation in climate as a proxy for climate change: Forecasting evolutionary trajectories from species differentiation and genetic correlations. AMERICAN JOURNAL OF BOTANY 2016; 103:140-152. [PMID: 26744480 DOI: 10.3732/ajb.1500108] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Accepted: 10/06/2015] [Indexed: 06/05/2023]
Abstract
PREMISE OF THE STUDY Climate change models for California predict a warmer, drier future, potentially resulting in shorter growing seasons. If phenotypic differences between closely related species currently distributed across a moisture and temperature gradient represent adaptations to their abiotic environment, then as conditions become warmer and drier, populations presently adapted to cooler and wetter conditions may evolve to become more similar to those adapted to warmer and drier conditions. Two sister species, Clarkia unguiculata and C. exilis, are distributed across a moisture and temperature gradient in the southern Sierra Nevada, providing an opportunity to predict how this process may occur. METHODS In a greenhouse experiment using wild-collected seeds from 11 populations in the southern Sierra Nevada, we examined relationships among elevation, climatic conditions, and population means for each trait, then evaluated bivariate relationships among maternal family means, using raw values and controlling for population and seed mass effects on phenotype. KEY RESULTS Clarkia exilis occupied warmer, drier conditions, typically at lower elevations, than C. unguiculata did and flowered earlier and faster, producing smaller flowers with lower herkogamy. In C. unguiculata, petal area, herkogamy, and the rate of flower production were positively correlated with days to first flower. CONCLUSIONS If selection favors earlier flowering, smaller petals, or faster flower production in C. unguiculata, then the genetic correlations among these traits should reinforce their joint evolution. Moreover, the correlations between these traits and herkogamy may promote the evolution of self-fertilization as an indirect response to selection, a previously unrecognized potential outcome of climate change.
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Affiliation(s)
- Heather E Schneider
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California 93106 USA
| | - Susan J Mazer
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California 93106 USA
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12
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Pannell JR, Auld JR, Brandvain Y, Burd M, Busch JW, Cheptou PO, Conner JK, Goldberg EE, Grant AG, Grossenbacher DL, Hovick SM, Igic B, Kalisz S, Petanidou T, Randle AM, de Casas RR, Pauw A, Vamosi JC, Winn AA. The scope of Baker's law. THE NEW PHYTOLOGIST 2015; 208:656-67. [PMID: 26192018 DOI: 10.1111/nph.13539] [Citation(s) in RCA: 110] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 05/27/2015] [Indexed: 05/13/2023]
Abstract
Baker's law refers to the tendency for species that establish on islands by long-distance dispersal to show an increased capacity for self-fertilization because of the advantage of self-compatibility when colonizing new habitat. Despite its intuitive appeal and broad empirical support, it has received substantial criticism over the years since it was proclaimed in the 1950s, not least because it seemed to be contradicted by the high frequency of dioecy on islands. Recent theoretical work has again questioned the generality and scope of Baker's law. Here, we attempt to discern where the idea is useful to apply and where it is not. We conclude that several of the perceived problems with Baker's law fall away when a narrower perspective is adopted on how it should be circumscribed. We emphasize that Baker's law should be read in terms of an enrichment of a capacity for uniparental reproduction in colonizing situations, rather than of high selfing rates. We suggest that Baker's law might be tested in four different contexts, which set the breadth of its scope: the colonization of oceanic islands, metapopulation dynamics with recurrent colonization, range expansions with recurrent colonization, and colonization through species invasions.
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Affiliation(s)
- John R Pannell
- Department of Ecology and Evolution, University of Lausanne, 1015, Lausanne, Switzerland
| | - Josh R Auld
- Department of Biology, West Chester University, West Chester, PA, 19383, USA
| | - Yaniv Brandvain
- Department of Plant Biology, University of Minnesota, St Paul, MN, 55108, USA
| | - Martin Burd
- School of Biological Sciences, Monash University, Melbourne, VIC, 3800, Australia
| | - Jeremiah W Busch
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Pierre-Olivier Cheptou
- CEFE UMR 5175, CNRS, Universite de Montpellier, Université Paul-Valery Montpellier, EPHE, CEFE 34293, Montpellier Cedex 05, France
| | - Jeffrey K Conner
- Kellogg Biological Station and Department of Plant Biology, Michigan State University, Hickory Corners, MI, 49060, USA
| | - Emma E Goldberg
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St Paul, MN, 55108, USA
| | | | | | - Stephen M Hovick
- Department of Evolution, Ecology, and Organismal Biology, The Ohio State University, Columbus, OH, 43210, USA
| | - Boris Igic
- Department of Biological Sciences, University of Illinois at Chicago, 840 W Taylor St, M/C 067, Chicago, IL, 60607, USA
| | - Susan Kalisz
- Department of Biology, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Theodora Petanidou
- Laboratory of Biogeography and Ecology, Department of Geography, University of the Aegean, 81100 Mytilene, Lesvos, Greece
| | - April M Randle
- Department of Environmental Science, University of San Francisco, San Francisco, CA, 94117-1049, USA
| | - Rafael Rubio de Casas
- CEFE UMR 5175, CNRS, Universite de Montpellier, Université Paul-Valery Montpellier, EPHE, CEFE 34293, Montpellier Cedex 05, France
- Departmento Ecología, Facultad de Ciencias, Universidad de Granada, UGR, 18071, Granada, Spain
- Estación Experimental de Zonas Áridas, EEZA-CSIC, Carretera de Sacramento s/n, La Cañada de San Urbano, EEZA 04120, Almeria, Spain
| | - Anton Pauw
- Department of Botany and Zoology, Stellenbosch University, Stellenbosch, 7602, South Africa
| | - Jana C Vamosi
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N1N4, Canada
| | - Alice A Winn
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA
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Vamosi JC, Armbruster WS, Renner SS. Evolutionary ecology of specialization: insights from phylogenetic analysis. Proc Biol Sci 2015; 281:rspb.2014.2004. [PMID: 25274367 DOI: 10.1098/rspb.2014.2004] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
In this Special feature, we assemble studies that illustrate phylogenetic approaches to studying salient questions regarding the effect of specialization on lineage diversification. The studies use an array of techniques involving a wide-ranging collection of biological systems (plants, butterflies, fish and amphibians are all represented). Their results reveal that macroevolutionary examination of specialization provides insight into the patterns of trade-offs in specialized systems; in particular, the genetic mechanisms of trade-offs appear to extend to very different aspects of life history in different groups. In turn, because a species may be a specialist from one perspective and a generalist in others, these trade-offs influence whether we perceive specialization to have effects on the evolutionary success of a lineage when we examine specialization only along a single axis. Finally, how geographical range influences speciation and extinction of specialist lineages remains a question offering much potential for further insight.
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Affiliation(s)
- Jana C Vamosi
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada T2L 0Z3
| | - W Scott Armbruster
- School of Biological Sciences, University of Portsmouth, Portsmouth PO1 2DY, UK Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99709, USA Department of Biology, NTNU, Trondheim 7491, Norway
| | - Susanne S Renner
- Systematic Botany and Mycology, Department of Biology, University of Munich (LMU), Munich 80638, Germany
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Anderson JT, Eckhart VM, Geber MA. Experimental studies of adaptation inClarkia xantiana. III. Phenotypic selection across a subspecies border. Evolution 2015; 69:2249-61. [DOI: 10.1111/evo.12745] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 06/11/2015] [Accepted: 07/08/2015] [Indexed: 11/30/2022]
Affiliation(s)
- Jill T. Anderson
- Department of Genetics; University of Georgia; Athens Georgia 30602
| | | | - Monica A. Geber
- Ecology and Evolutionary Biology Department; Corson Hall, Cornell University; Ithaca New York 14853
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Dudley LS, Hove AA, Emms SK, Verhoeven AS, Mazer SJ. Seasonal changes in physiological performance in wild Clarkia xantiana populations: Implications for the evolution of a compressed life cycle and self-fertilization. AMERICAN JOURNAL OF BOTANY 2015; 102:962-972. [PMID: 26101420 DOI: 10.3732/ajb.1400557] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Accepted: 05/05/2015] [Indexed: 06/04/2023]
Abstract
PREMISE OF THE STUDY One explanation for the evolution of selfing, the drought escape hypothesis, proposes that self-fertilization may evolve under conditions of intensifying seasonal drought as part of a suite of traits that enable plants to accelerate the completion of their life cycle, thereby escaping late-season drought. Here, we test two fundamental assumptions of this hypothesis in Clarkia xantiana: (1) that a seasonal decline in precipitation causes an increase in drought stress and (2) that this results in changes in physiological performance, reflecting these deteriorating conditions. METHODS We examined seasonal and interannual variation in abiotic environmental conditions (estimated by ambient temperature, relative humidity, predawn leaf water potentials, and carbon isotope ratios) and physiological traits (photosynthesis, conductance, transpiration, instantaneous water-use efficiency, ascorbate peroxidase and glutathione reductase activities, quantum yield of photosystem II, PSII potential efficiency) in field populations of C. xantiana in 2009 and 2010. KEY RESULTS In both years, plants experienced intensifying drought across the growing season. Gas exchange rates decreased over the growing season and were lower in 2009 (a relatively dry year) than in 2010, suggesting that the temporal changes from early to late spring were directly linked to the deteriorating environmental conditions. CONCLUSIONS Seasonal declines in transpiration rate may have increased survival by protecting plants from desiccation. Concomitant declines in photosynthetic rate likely reduced the availability of resources for seed production late in the season. Thus, the physiological patterns observed are consistent with the conditions required for the drought escape hypothesis.
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Affiliation(s)
- Leah S Dudley
- Warren Wilson College, P.O. Box 9000, Asheville, North Carolina 28815 USA
| | - Alisa A Hove
- Warren Wilson College, P.O. Box 9000, Asheville, North Carolina 28815 USA
| | - Simon K Emms
- University of St. Thomas, 2115 Summit Ave., St. Paul, Minnesota, USA 5105
| | - Amy S Verhoeven
- University of St. Thomas, 2115 Summit Ave., St. Paul, Minnesota, USA 5105
| | - Susan J Mazer
- University of California, Santa Barbara, Santa Barbara, California 93106 USA
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The influence of pleiotropy between viability and pollen fates on mating system evolution. Theor Popul Biol 2014; 99:7-17. [PMID: 25448089 DOI: 10.1016/j.tpb.2014.10.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Revised: 10/13/2014] [Accepted: 10/18/2014] [Indexed: 11/23/2022]
Abstract
Floral displays are functionally and genetically integrated structures, so modifications to display will likely affect multiple fitness components (pleiotropy), including pollen export and self-pollination, and therefore selfing rate. Consequently, the great diversities of floral displays and of mating systems found among angiosperms have likely co-evolved. I extend previous models of mating system evolution to determine how pleiotropy that links viability (e.g., probability of survival to reproduction) and the allocation of pollen for export and selfing affects the evolution of selfing, outcrossing, and in particular, mixed mating. I show that the outcome depends on how pollen shifts from being exported, unused, or used for selfing. Furthermore, pleiotropy that affects viability can explain observations not addressed by previous theory, including the evolution of mixed mating despite high inbreeding depression in the absence of pollen-limitation. Therefore, pleiotropy may play a key role in explaining selfing rates for such species that exhibit otherwise enigmatic mating systems.
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17
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Weber A, Kolb A. Differences in heritable trait variation among populations of varying size in the perennial herb Phyteuma spicatum. CONSERV GENET 2014. [DOI: 10.1007/s10592-014-0620-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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18
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Armbruster WS. Floral specialization and angiosperm diversity: phenotypic divergence, fitness trade-offs and realized pollination accuracy. AOB PLANTS 2014; 6:plu003. [PMID: 24790124 PMCID: PMC4038416 DOI: 10.1093/aobpla/plu003] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 01/05/2014] [Indexed: 05/08/2023]
Abstract
Plant reproduction by means of flowers has long been thought to promote the success and diversification of angiosperms. It remains unclear, however, how this success has come about. Do flowers, and their capacity to have specialized functions, increase speciation rates or decrease extinction rates? Is floral specialization fundamental or incidental to the diversification? Some studies suggest that the conclusions we draw about the role of flowers in the diversification and increased phenotypic disparity (phenotypic diversity) of angiosperms depends on the system. For orchids, for example, specialized pollination may have increased speciation rates, in part because in most orchids pollen is packed in discrete units so that pollination is precise enough to contribute to reproductive isolation. In most plants, however, granular pollen results in low realized pollination precision, and thus key innovations involving flowers more likely reflect reduced extinction rates combined with opportunities for evolution of greater phenotypic disparity (phenotypic diversity) and occupation of new niches. Understanding the causes and consequences of the evolution of specialized flowers requires knowledge of both the selective regimes and the potential fitness trade-offs in using more than one pollinator functional group. The study of floral function and flowering-plant diversification remains a vibrant evolutionary field. Application of new methods, from measuring natural selection to estimating speciation rates, holds much promise for improving our understanding of the relationship between floral specialization and evolutionary success.
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Affiliation(s)
- W. Scott Armbruster
- School of Biological Sciences, University of Portsmouth, Portsmouth PO1 2DY, UK
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775-7000, USA
- Department of Biology, Norwegian University of Science & Technology, Trondheim N-7491, Norway
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19
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20
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Dudley LS, Hove AA, Mazer SJ. Physiological performance and mating system in Clarkia (Onagraceae): does phenotypic selection predict divergence between sister species? AMERICAN JOURNAL OF BOTANY 2012; 99:488-507. [PMID: 22396332 DOI: 10.3732/ajb.1100387] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
PREMISE OF THE STUDY The evolution of self-fertilization often occurs in association with other floral, life history, and fitness-related traits. A previous study found that field populations of Clarkia exilis (a predominantly autogamous selfer) and its sister species, Clarkia unguiculata (a facultative outcrosser) differ in mean photosynthetic rates and instantaneous water use efficiency (WUE(i)). Here, we investigate the strength and direction of selection on these traits in multiple populations of each taxon to determine whether natural selection may contribute to the phenotypic differences between them. METHODS In spring 2008, we measured instantaneous gas exchange rates in nine populations during vegetative growth (Early) and/or during flowering (Late). We conducted selection gradient analyses and estimated selection differentials within populations and across pooled conspecific populations to evaluate the strength, direction, and consistency of selection on each trait early and late in the season. KEY RESULTS The direction and relative strength of selection on photosynthetic rates in these taxa corresponds to the phenotypic difference between them; C. exilis has higher photosynthetic rates than C. unguiculata, as well as stronger, more consistent selection favoring rapid photosynthesis throughout the growing season. Patterns of selection on transpiration, WUE(i), and the timing of flowering progression are less consistent with phenotypic differences (or lack thereof) between taxa. CONCLUSIONS We detected several examples where selection was consistent with the phenotypic divergence between sister taxa, but there were also numerous instances that were equivocal or in which selection did not predict the realized phenotypic difference between taxa.
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Affiliation(s)
- Leah S Dudley
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, California 93106, USA.
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Jordan CY, Otto SP. FUNCTIONAL PLEIOTROPY AND MATING SYSTEM EVOLUTION IN PLANTS: FREQUENCY-INDEPENDENT MATING. Evolution 2012; 66:957-72. [DOI: 10.1111/j.1558-5646.2011.01513.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Karron JD, Ivey CT, Mitchell RJ, Whitehead MR, Peakall R, Case AL. New perspectives on the evolution of plant mating systems. ANNALS OF BOTANY 2012; 109:493-503. [PMID: 22210849 PMCID: PMC3278297 DOI: 10.1093/aob/mcr319] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
BACKGROUND The remarkable diversity of mating patterns and sexual systems in flowering plants has fascinated evolutionary biologists for more than a century. Enduring questions about this topic include why sexual polymorphisms have evolved independently in over 100 plant families, and why proportions of self- and cross-fertilization often vary dramatically within and among populations. Important new insights concerning the evolutionary dynamics of plant mating systems have built upon a strong foundation of theoretical models and innovative field and laboratory experiments. However, as the pace of advancement in this field has accelerated, it has become increasingly difficult for researchers to follow developments outside their primary area of research expertise. SCOPE In this Viewpoint paper we highlight three important themes that span and integrate different subdisciplines: the changes in morphology, phenology, and physiology that accompany the transition to selfing; the evolutionary consequences of pollen pool diversity in flowering plants; and the evolutionary dynamics of sexual polymorphisms. We also highlight recent developments in molecular techniques that will facilitate more efficient and cost-effective study of mating patterns in large natural populations, research on the dynamics of pollen transport, and investigations on the genetic basis of sexual polymorphisms. This Viewpoint also serves as the introduction to a Special Issue on the Evolution of Plant Mating Systems. The 15 papers in this special issue provide inspiring examples of recent discoveries, and glimpses of exciting developments yet to come.
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Affiliation(s)
- Jeffrey D Karron
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA.
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23
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Ivey CT, Carr DE. Tests for the joint evolution of mating system and drought escape in Mimulus. ANNALS OF BOTANY 2012; 109:583-98. [PMID: 21831854 PMCID: PMC3278286 DOI: 10.1093/aob/mcr160] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
BACKGROUND AND AIMS Self-fertilizing taxa are often found at the range margins of their progenitors, where sub-optimal habitats may select for alternative physiological strategies. The extent to which self-fertilization is favoured directly vs. arising indirectly through correlations with other adaptive life history traits is unclear. Trait responses to selection depend on genetic variation and covariation, as well as phenotypic and genetic responses to altered environmental conditions. We tested predictions of the hypothesis that self-fertilization in Mimulus arises through direct selection on physiological and developmental traits that allow seasonal drought escape. METHODS Phenotypic selection on mating system and drought escape traits was estimated in field populations of M. guttatus. In addition, trait phenotype and phenotypic selection were compared between experimental wet and dry soil in two greenhouse populations each of M. guttatus and M. nasutus. Finally, genetic variation and covariation for traits were compared between wet and dry soil treatments in a greenhouse population of M. guttatus. KEY RESULTS Consistent with predictions, selection for early flowering was generally stronger than for mating system traits, and selection for early flowering was stronger in dry soil. Inconsistent with predictions, selection for water-use efficiency was largely absent; selection for large flowers was stronger than for drought escape in the field; and most drought escape and mating system traits were not genetically correlated. A positive genetic correlation between flowering time and flower size, which opposed the adaptive contour, emerged only in wet soil, suggesting that variation in water availability may maintain variation in these traits. Plastic responses to soil moisture treatments supported the idea that taxonomic divergence could have been facilitated by plasticity in flowering time and selfing. CONCLUSIONS The hypothesis that plant mating systems may evolve indirectly via selection on correlated life history characteristics is plausible and warrants increased attention.
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Affiliation(s)
- Christopher T Ivey
- Department of Biological Sciences, California State University, Chico, CA 95929-0515, USA.
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Levin DA. Mating system shifts on the trailing edge. ANNALS OF BOTANY 2012; 109:613-20. [PMID: 21980190 PMCID: PMC3278285 DOI: 10.1093/aob/mcr159] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Accepted: 04/20/2011] [Indexed: 05/19/2023]
Abstract
BACKGROUND The trailing edges of species ranges are becoming a subject of increasing interest as the environment changes due to global warming. Trailing edge populations are likely to face extinction because of a decline in numbers and an inability to evolve new adaptations with sufficient speed. Discussions of character change in the trailing edge have focused on physiological, exomorphic and phenological traits. The mating pattern within populations has not been part of the discourse, in spite of the fact that the mating pattern may affect the ability of populations to respond to environmental change and to maintain their sizes. In this paper, the case is made that a substantial increase in self-fertilization rates may occur via plastic responses to stress. SCOPE AND CONCLUSIONS Small populations on the trailing edge are especially vulnerable to environmental change because of inadequate levels of cross-fertilization. Evidence is presented that a deficiency of cross-seed production is due to inadequate pollinator services and a paucity of self-incompatibility alleles within populations. Evidence also is presented that if plants are self-compatible, self-fertilization may compensate in part for this deficiency through a stress-induced increase in levels of self-compatibility and stress-induced alterations in floral morphology that elevate self-pollination. Whereas increased self-fertility may afford populations the time to adapt to their changing environments, it can be concluded that increased selfing is not a panacea for the ills of environmental change, because it will lead to substantial reductions in genetic diversity, which may render adaptation unlikely.
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Affiliation(s)
- Donald A Levin
- Section of Integrative Biology, University of Texas-Austin, TX 78713, USA.
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Eckhart VM, Geber MA, Morris WF, Fabio ES, Tiffin P, Moeller DA. The geography of demography: long-term demographic studies and species distribution models reveal a species border limited by adaptation. Am Nat 2011; 178 Suppl 1:S26-43. [PMID: 21956090 DOI: 10.1086/661782] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Potential causes of species' geographic distribution limits fall into two broad classes: (1) limited adaptation across spatially variable environments and (2) limited opportunities to colonize unoccupied areas. Combining demographic studies, analyses of demographic responses to environmental variation, and species distribution models, we investigated the causes of range limits in a model system, the eastern border of the California annual plant Clarkia xantiana ssp. xantiana. Vital rates of 20 populations varied with growing season temperature and precipitation: fruit number and overwinter survival of 1-year-old seeds declined steeply, while current-year seed germination increased modestly along west-to-east gradients in decreasing temperature, decreasing mean precipitation, and increasing variation in precipitation. Long-term stochastic finite rate of increase, λ(s), exhibited a fourfold range and varied among geologic surface materials as well as with temperature and precipitation. Growth rate declined significantly toward the eastern border, falling below 1 in three of the five easternmost populations. Distribution models employing demographically important environmental variables predicted low habitat favorability beyond the eastern border. Models that filtered or weighted population presences by λ(s) predicted steeper eastward declines in favorability and assigned greater roles in setting the distribution to among-year variation in precipitation and to geologic surface material. These analyses reveal a species border likely set by limited adaptation to declining environmental quality.
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Affiliation(s)
- V M Eckhart
- Department of Biology, Grinnell College, Grinnell, Iowa 50112, USA.
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Mazer SJ, Dudley LS, Delesalle VA, Paz H, Galusky P. Stability of pollen-ovule ratios in pollinator-dependent versus autogamous Clarkia sister taxa: testing evolutionary predictions. THE NEW PHYTOLOGIST 2009; 183:630-648. [PMID: 19500262 DOI: 10.1111/j.1469-8137.2009.02886.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
It has been proposed that natural selection should favor distinct temporal patterns of sex allocation in selfing vs pollinator-dependent taxa. In autogamous selfers in which pollen receipt is highly reliable, selection should favor genotypes that maintain low and stable pollen to ovule (P : O) ratios throughout flowering. By contrast, in outcrossers the optimum P : O ratio of an individual's flowers will depend on pollinator abundances and mating opportunities, both of which may vary over time. In this case, selection may favor temporal variation among flowers in the P : O ratio. An opposing prediction is that selfing taxa will be developmentally more unstable than outcrossers because of lower homeostasis caused by high homozygosity. We compared temporal changes in the P : O ratio in two pairs of sister taxa in the genus Clarkia. We examined hundreds of glasshouse-raised maternal families representing three wild populations each of the outcrossing, insect-pollinated Clarkia unguiculata, the facultatively autogamous Clarkia exilis and the outcrossing and selfing subspecies of Clarkia xantiana: ssp. xantiana and parviflora, respectively. Temporal change in the P : O ratio was significantly greater in both outcrossers than in their selfing sister taxa, although the proportional changes in the P : O ratio (relative to the first bud produced) did not differ significantly between sister taxa (0.07 < P < 0.10). Our results provide partial support for the hypothesis that the P : O ratio is more stable in selfing than in outcrossing taxa and reject the hypothesis that selfers are less stable.
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Affiliation(s)
- Susan J Mazer
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California, CA 93106, USA
| | - Leah S Dudley
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California, CA 93106, USA
| | | | - Horacio Paz
- Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México, Mexico, D.F.C.P. 04510
| | - Preston Galusky
- Life Science Department, Riverside Community College, Riverside, California, CA 92506, USA
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Delesalle VA, Mazer SJ. Size-dependent pollen:ovule ratios and the allometry of floral sex allocation in Clarkia (Onagraceae) taxa with contrasting mating systems. AMERICAN JOURNAL OF BOTANY 2009; 96:968-978. [PMID: 21628249 DOI: 10.3732/ajb.0800039] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Multiple field populations of two pairs of diploid sister taxa with contrasting mating systems in the genus Clarkia (Onagraceae) were surveyed to test predictions concerning the effects of resource status, estimated as plant size, on pollen and ovule production and on the pollen:ovule (P:O) ratio of flowers. Most theoretical models of size-dependent sex allocation predict that, in outcrossing populations, larger plants should allocate more resources to female function. Lower P:O ratios in larger plants compared to smaller plants have been interpreted as supporting this prediction. In contrast, we predicted that P:O ratio should not vary with plant size in predominantly selfing plants, in which each flower contributes to reproductive success equally through male and female function. We found that, in all four taxa, both ovule and pollen production per flower usually increased significantly with plant size and that the shape of this relationship was decelerating. However, ovule production either decelerated more rapidly than or at the same rate as pollen production with plant size. Consequently,the P:O ratio increased or had no relationship with plant size. This relationship was population-specific (not taxon-specific) and independent of the mating system. Possible explanations for the increasing maleness with plant size are discussed.
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DELESALLE VA, MAZER SJ, PAZ H. Temporal variation in the pollen:ovule ratios ofClarkia(Onagraceae) taxa with contrasting mating systems: field populations. J Evol Biol 2007; 21:310-323. [DOI: 10.1111/j.1420-9101.2007.01444.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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DUDLEY LS, MAZER SJ, GALUSKY P. The joint evolution of mating system, floral traits and life history in Clarkia (Onagraceae): genetic constraints vs. independent evolution. J Evol Biol 2007; 20:2200-18. [DOI: 10.1111/j.1420-9101.2007.01421.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Comparing Variational Properties of Homologous Floral and Vegetative Characters in Dalechampia scandens: Testing the Berg Hypothesis. Evol Biol 2007. [DOI: 10.1007/s11692-007-9006-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Anderson IA, Busch JW. Relaxed pollinator-mediated selection weakens floral integration in self-compatible taxa of Leavenworthia (Brassicaceae). AMERICAN JOURNAL OF BOTANY 2006; 93:860-867. [PMID: 21642148 DOI: 10.3732/ajb.93.6.860] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Natural selection should favor the integration of floral traits that enhance pollen export and import in plant populations that rely upon pollinators. If this is true, then phenotypic correlations between floral traits should weaken in self-fertilizing groups that do not require pollinator visitation to produce seed. We tested this hypothesis in Leavenworthia, a plant genus in which there have been multiple independent losses of the sporophytic self-incompatibility system found throughout the Brassicaceae. In particular, we conducted phylogenetically independent contrasts of floral trait correlations between two pairs of self-incompatible (SI) and self-compatible (SC) sister taxa. In support of the hypothesis that pollinator-mediated selection integrates floral traits, we found that both SC Leavenworthia taxa have weaker overall floral correlations in comparison to sister taxa that rely upon pollinators. The two independently derived SC Leavenworthia flowers have significantly weaker stamen-petal or pistil-petal correlations, respectively, whereas the stamen-pistil correlation remains constant. These patterns suggest that relaxation of pollinator-mediated selection weakens the integration of traits associated with pollen export and import. The retention of high stamen-pistil correlations in the SC taxa of Leavenworthia further implies that the integration of these traits is either constrained or maintained by selection favoring the successful transfer of pollen within flowers to secure self-pollination.
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Affiliation(s)
- Ingrid A Anderson
- Department of Biology, Indiana University, 1001 E. 3rd Street, Bloomington, Indiana 47405 USA
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Sargent RD, Mandegar MA, Otto SP. A MODEL OF THE EVOLUTION OF DICHOGAMY INCORPORATING SEX-RATIO SELECTION, ANTHER-STIGMA INTERFERENCE, AND INBREEDING DEPRESSION. Evolution 2006. [DOI: 10.1111/j.0014-3820.2006.tb01172.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Sargent RD, Mandegar MA, Otto SP. A MODEL OF THE EVOLUTION OF DICHOGAMY INCORPORATING SEX-RATIO SELECTION, ANTHER-STIGMA INTERFERENCE, AND INBREEDING DEPRESSION. Evolution 2006. [DOI: 10.1554/05-389.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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