1
|
Barbot E, Dufaÿ M, Tonnabel J, Godé C, De Cauwer I. On the function of flower number: disentangling fertility from pollinator-mediated selection. Proc Biol Sci 2022; 289:20221987. [PMID: 36448279 PMCID: PMC9709571 DOI: 10.1098/rspb.2022.1987] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 11/03/2022] [Indexed: 12/03/2022] Open
Abstract
In animal-pollinated angiosperms, the 'male-function' hypothesis claims that male reproductive success (RS) should benefit from large floral displays, through pollinator attraction, while female RS is expected to be mainly limited by resource availability. As appealing as this theory might be, studies comparing selection strength on flower number in both sexes rarely document the expected asymmetry. This discrepancy could arise because flower number impacts both pollinator attraction and overall gamete number. In this study, we artificially manipulate floral displays to disentangle the fertility versus pollinator attraction components of selection, both in terms of mating and RS. In females, flower number was under strong fertility selection, as predicted in the absence of pollen limitation. By contrast, in males, flower number was mainly under sexual selection, which in turn increased male RS. However, these selection patterns were not different in males with artificially increased floral displays. This suggests that sexual selection acting on flower number in males does not occur because flower number increases pollinator attraction, but rather because more pollen is available to disperse on more mates. Our study illustrates the power of disentangling various components of selection with potentially sex-specific effects for understanding the evolution of sexual dimorphism.
Collapse
Affiliation(s)
- Estelle Barbot
- Univ. Lille, CNRS, UMR 8198 - Evo-Eco-Paleo, F-59000 Lille, France
- ISEM, Univ. Montpellier, CNRS, IRD, Montpellier, France
| | - Mathilde Dufaÿ
- CEFE, Univ. Montpellier, CNRS, Univ. Paul Valéry Montpellier 3, EPHE, IRD, Montpellier, France
| | - Jeanne Tonnabel
- ISEM, Univ. Montpellier, CNRS, IRD, Montpellier, France
- CEFE, Univ. Montpellier, CNRS, Univ. Paul Valéry Montpellier 3, EPHE, IRD, Montpellier, France
| | - Cécile Godé
- Univ. Lille, CNRS, UMR 8198 - Evo-Eco-Paleo, F-59000 Lille, France
| | | |
Collapse
|
2
|
Simón‐Porcar VI, Muñoz‐Pajares AJ, de Castro A, Arroyo J. Direct evidence supporting Darwin's hypothesis of cross-pollination promoted by sex organ reciprocity. THE NEW PHYTOLOGIST 2022; 235:2099-2110. [PMID: 35596603 PMCID: PMC9546006 DOI: 10.1111/nph.18266] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 05/09/2022] [Indexed: 05/28/2023]
Abstract
The floral phenotype plays a main role in the attraction and fit of pollinators. Both perianth traits and the positioning of sex organs can be subjected to natural selection and determine nonrandom mating patterns in populations. In stylar-polymorphic species, the Darwinian hypothesis predicts increased mating success between individuals with sex organs at equivalent heights (i.e. with higher reciprocity). We used paternity analyses in experimental populations of a stylar-dimorphic species. By comparing the observed mating patterns with those expected under random mating, we tested the effects of sex organ reciprocity and perianth traits on mating success. We also analysed phenotypic selection on perianth traits through female and male functions. The (dis)similarity of parental perianth traits had no direct effects on the mating patterns. Sex organ reciprocity had a positive effect on mating success. Narrow floral tubes increased this effect in upper sex organs. Perianth traits showed little signs of phenotypic selection. Female and absolute fitness measures resulted in different patterns of phenotypic selection. We provide precise empirical evidence of the Darwinian hypothesis about the functioning of stylar polymorphisms, demonstrating that mating patterns are determined by sex organ reciprocity and only those perianth traits which are critical to pollinator fit.
Collapse
Affiliation(s)
| | - A. Jesús Muñoz‐Pajares
- Department of GeneticsUniversity of GranadaE‐18071GranadaSpain
- Research Centre in Biodiversity and Genetic Resources (CIBIO)Campus Agrário de Vairão4485‐661VairãoPortugal
| | - Alejandra de Castro
- Department of Plant Biology and EcologyUniversity of SevilleE‐41080SevilleSpain
| | - Juan Arroyo
- Department of Plant Biology and EcologyUniversity of SevilleE‐41080SevilleSpain
| |
Collapse
|
3
|
Bee-Mediated Selection Favors Floral Sex Specialization in a Heterantherous Species: Strategies to Solve the Pollen Dilemma. PLANTS 2020; 9:plants9121685. [PMID: 33271837 PMCID: PMC7760250 DOI: 10.3390/plants9121685] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 11/27/2020] [Indexed: 12/15/2022]
Abstract
Animal-pollinated plants show a broad variation in floral morphology traits and gametophyte production within populations. Thus, floral traits related to plant reproduction and sexuality are usually exposed to pollinator-mediated selection. Such selective pressures may be even stronger in heterantherous and pollen flowers, in which pollen contributes to both bee feeding and pollination, overcoming the “pollen dilemma” or the inability to perform both functions simultaneously. We describe the phenotypic gender and sexual organ morphology of flowers in two populations of Macairea radula (Melastomataceae), a heterantherous and buzz-pollinated species with pollen flowers. We estimated selection gradients on these traits through female and male fitness components. Both populations showed sizeable phenotypic gender variation, from strict hermaphrodites to increased femaleness or maleness. We found a continuous variation in style and stamen size, and this variation was correlated with corresponding shape values of both sexual organs. We detected bee-mediated selection towards short and long styles through seed number and towards intermediate degrees of heteranthery through pollen removal in one population, and selection towards increased maleness through pollen dispersal in both populations. Our results suggest that bee-mediated selection favors floral sex specialization and stylar dimorphism in M. radula, optimizing reproductive success and solving the pollen dilemma.
Collapse
|
4
|
Weitemier K, Straub SC, Fishbein M, Bailey CD, Cronn RC, Liston A. A draft genome and transcriptome of common milkweed ( Asclepias syriaca) as resources for evolutionary, ecological, and molecular studies in milkweeds and Apocynaceae. PeerJ 2019; 7:e7649. [PMID: 31579586 PMCID: PMC6756140 DOI: 10.7717/peerj.7649] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 08/09/2019] [Indexed: 02/06/2023] Open
Abstract
Milkweeds (Asclepias) are used in wide-ranging studies including floral development, pollination biology, plant-insect interactions and co-evolution, secondary metabolite chemistry, and rapid diversification. We present a transcriptome and draft nuclear genome assembly of the common milkweed, Asclepias syriaca. This reconstruction of the nuclear genome is augmented by linkage group information, adding to existing chloroplast and mitochondrial genomic resources for this member of the Apocynaceae subfamily Asclepiadoideae. The genome was sequenced to 80.4× depth and the draft assembly contains 54,266 scaffolds ≥1 kbp, with N50 = 3,415 bp, representing 37% (156.6 Mbp) of the estimated 420 Mbp genome. A total of 14,474 protein-coding genes were identified based on transcript evidence, closely related proteins, and ab initio models, and 95% of genes were annotated. A large proportion of gene space is represented in the assembly, with 96.7% of Asclepias transcripts, 88.4% of transcripts from the related genus Calotropis, and 90.6% of proteins from Coffea mapping to the assembly. Scaffolds covering 75 Mbp of the Asclepias assembly formed 11 linkage groups. Comparisons of these groups with pseudochromosomes in Coffea found that six chromosomes show consistent stability in gene content, while one may have a long history of fragmentation and rearrangement. The progesterone 5β-reductase gene family, a key component of cardenolide production, is likely reduced in Asclepias relative to other Apocynaceae. The genome and transcriptome of common milkweed provide a rich resource for future studies of the ecology and evolution of a charismatic plant family.
Collapse
Affiliation(s)
- Kevin Weitemier
- Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR, USA
| | | | - Mark Fishbein
- Department of Plant Biology, Ecology, and Evolution, Oklahoma State University, Stillwater, OK, USA
| | - C. Donovan Bailey
- Department of Biology, New Mexico State University, Las Cruces, NM, USA
| | - Richard C. Cronn
- Pacific Northwest Research Station, USDA Forest Service, Corvallis, OR, USA
| | - Aaron Liston
- Department of Botany & Plant Pathology, Oregon State University, Corvallis, OR, USA
| |
Collapse
|
5
|
Koski MH, Ison JL, Padilla A, Pham AQ, Galloway LF. Linking pollinator efficiency to patterns of pollen limitation: small bees exploit the plant-pollinator mutualism. Proc Biol Sci 2019; 285:rspb.2018.0635. [PMID: 29875304 DOI: 10.1098/rspb.2018.0635] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 05/14/2018] [Indexed: 11/12/2022] Open
Abstract
Seemingly mutualistic relationships can be exploited, in some cases reducing fitness of the exploited species. In plants, the insufficient receipt of pollen limits reproduction. While infrequent pollination commonly underlies pollen limitation (PL), frequent interactions with low-efficiency, exploitative pollinators may also cause PL. In the widespread protandrous herb Campanula americana, visitation by three pollinators explained 63% of the variation in PL among populations spanning the range. Bumblebees and the medium-sized Megachile campanulae enhanced reproductive success, but small solitary bees exacerbated PL. To dissect mechanisms behind these relationships, we scored sex-specific floral visitation, and the contributions of each pollinator to plant fitness using single flower visits. Small bees and M. campanulae overvisited male-phase flowers, but bumblebees frequently visited female-phase flowers. Fewer bumblebee visits were required to saturate seed set compared to other bees. Scaling pollinator efficiency metrics to populations, small bees deplete large amounts of pollen due to highly male-biased flower visitation and infrequent pollen deposition. Thus, small bees reduce plant reproduction by limiting pollen available for transfer by efficient pollinators, and appear to exploit the plant-pollinator mutualism, acting as functional parasites to C. americana It is therefore unlikely that small bees will compensate for reproductive failure in C. americana when bumblebees are scarce.
Collapse
Affiliation(s)
- Matthew H Koski
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Jennifer L Ison
- Department of Biology, The College of Wooster, Wooster, OH 44691, USA
| | - Ashley Padilla
- Department of Biology, The College of Wooster, Wooster, OH 44691, USA
| | - Angela Q Pham
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Laura F Galloway
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| |
Collapse
|
6
|
Bawa KS. Kin selection and the evolution of plant reproductive traits. Proc Biol Sci 2017; 283:rspb.2016.0789. [PMID: 27852800 PMCID: PMC5124086 DOI: 10.1098/rspb.2016.0789] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 06/24/2016] [Indexed: 11/12/2022] Open
Abstract
Competition among developing seeds and sibling rivalry within multiovulated ovaries can be deleterious for both the maternal parent and the siblings. Increased genetic relatedness of seeds within the ovary may foster kin selection and reduce the deleterious consequences of sibling competition. The pollen parent may also be selected for siring all progeny within a fruit. I propose a series of hypotheses to explain the evolution of a number of reproductive traits in angiosperms in the context of kin selection and sibling rivalry within the ovaries of angiosperms. I present evidence to show that a single-pollen parent, indeed, often sires seeds within multiovulated ovaries. Various types of pollen aggregations and transfer of such pollen masses to the stigmas of flowers by specialized pollinators make this increased genetic relatedness possible. An alternative mode to reduce sibling rivalry may be the reduction of ovule number to one, an evolutionary trend that has independently occurred many times in flowering plants. Finally, I build on previously established correlations to predict two sets of correlations among reproductive traits. In the first case, large showy flowers, transfer of pollen en masse by specialized pollinators, and multiovulated ovaries and multisided fruits seem to be correlated. In the second case, the previously established correlations among small and inconspicuous flowers, pollination by wind, water or generalist insects, flowers and fruits with few or single ovules and seeds, respectively, may also include monoecy or dioecy. Although correlations among many of these traits have been established in the past, I invoke kin selection and sibling competition to explain the evolution of correlated traits as two distinct evolutionary pathways in angiosperms.
Collapse
Affiliation(s)
- Kamaljit S Bawa
- Department of Biology, University of Massachusetts, Boston, MA 02125-3393, USA .,Ashoka Trust for Research in Ecology and the Environment, Bangalore, Karnataka 560064, India
| |
Collapse
|
7
|
Emms SK, Stratton DA, Snow AA. THE EFFECT OF INFLORESCENCE SIZE ON MALE FITNESS: EXPERIMENTAL TESTS IN THE ANDROMONOECIOUS LILY, ZIGADENUS PANICULATUS. Evolution 2017; 51:1481-1489. [PMID: 28568611 DOI: 10.1111/j.1558-5646.1997.tb01471.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/1996] [Accepted: 05/16/1997] [Indexed: 11/26/2022]
Abstract
We studied the relationship between inflorescence size and male fitness in the andromonoecious lily Zigadenus paniculatus, using experimentally manipulated inflorescences to eliminate possible correlations between flower number, resource availability, and other floral traits. Allozyme markers were used to determine the siring success of large versus small plants in 14 arrays of plants, each array containing five large and five small plants. The inflorescence size of small plants was held constant both within and among arrays; the size of large plants was held constant within an array but was varied among arrays. Large plants sired more than half the seeds in 12 of the 14 arrays, and significantly more than half in six of these 12. However, in eight of the arrays, large plants sired significantly fewer seeds than expected on the basis of their size advantage. Furthermore, there was no significant relationship between relative size and relative siring success in comparisons among arrays. A maximum-likelihood model estimated that 28% of seeds were sired by imported pollen, with 95% confidence limits of 13% and 50%. Within these limits, high import rates tended to mask the relative success of large plants in several arrays. These results suggest that the evolution of inflorescence size in Z. paniculatus is at least partly driven by selection for increased male success, assuming genetic variation for flower number. However, the data also support a growing body of evidence that estimates of male fitness in plants can be highly variable. We discuss the sources of this variability and the possible effects of inflorescence design on the relationship between inflorescence size and fitness.
Collapse
Affiliation(s)
- S K Emms
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, 08544-1003.,Department of Plant Biology, Ohio State University, 1735 Neil Avenue, Columbus, Ohio, 43210-1293
| | - D A Stratton
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, 08544-1003
| | - A A Snow
- Department of Plant Biology, Ohio State University, 1735 Neil Avenue, Columbus, Ohio, 43210-1293
| |
Collapse
|
8
|
McCartney MA. SEX ALLOCATION AND MALE FITNESS GAIN IN A COLONIAL, HERMAPHRODITIC MARINE INVERTEBRATE. Evolution 2017; 51:127-140. [DOI: 10.1111/j.1558-5646.1997.tb02394.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/1995] [Accepted: 09/17/1996] [Indexed: 11/29/2022]
Affiliation(s)
- Michael A. McCartney
- Section of Evolution and Ecology Center for Population Biology University of California Davis California 95616
| |
Collapse
|
9
|
Mitchell RJ. ADAPTIVE SIGNIFICANCE OF
IPOMOPSIS AGGREGATA
NECTAR PRODUCTION: OBSERVATION AND EXPERIMENT IN THE FIELD. Evolution 2017; 47:25-35. [DOI: 10.1111/j.1558-5646.1993.tb01196.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/1992] [Accepted: 05/17/1992] [Indexed: 11/28/2022]
Affiliation(s)
- Randall J. Mitchell
- Department of Biology University of California Riverside CA 92521 USA
- Rocky Mountain Biological Laboratory Crested Butte CO 81224 USA
| |
Collapse
|
10
|
Meagher TR. THE QUANTITATIVE GENETICS OF SEXUAL DIMORPHISM IN SILENE LATIFOLIA (CARYOPHYLLACEAE). II. RESPONSE TO SEX-SPECIFIC SELECTION. Evolution 2017; 48:939-951. [PMID: 28564465 DOI: 10.1111/j.1558-5646.1994.tb05284.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/1992] [Accepted: 06/24/1993] [Indexed: 11/29/2022]
Abstract
A well-established theoretical relationship exists between genetic correlations between the sexes and the dynamics of response to sex-specific selection. The present study investigates the response to sex-specific selection for two sexually dimorphic traits that have been documented to be genetically variable, calyx diameter and flower number, in Silene latifolia. Following the establishment of a base generation with a known genetic background, selection lines were established and two generations of sex-specific selection were imposed. Calyx diameter responded directly to sex-specific selection, and the positive genetic correlation between the sexes was reflected in correlated responses in the sex that was not the basis for selection within a particular line. Flower number showed a more erratic response to sex-specific selection in that selection in some lines was initially in the wrong direction, that is, selection for a decrease in flower number resulted in an increase. These erratic responses were attributable to genotype-environment interaction as reflected in significant heteroscedasticity in variance among families. Correlated responses to selection in the sex that was not the immediate basis for selection indicated the possible existence of a negative genetic correlation between the sexes for this trait. These results test for the first time the impact of genetic correlations between the sexes on the evolutionary dynamics of sexually dimorphic traits in a plant species.
Collapse
Affiliation(s)
- Thomas R Meagher
- Department of Biological Sciences, Rutgers University, P.O. Box 1059, Piscataway, New Jersey, 08855-1059
| |
Collapse
|
11
|
Devlin B, Clegg J, Ellstrand NC. THE EFFECT OF FLOWER PRODUCTION ON MALE REPRODUCTIVE SUCCESS IN WILD RADISH POPULATIONS. Evolution 2017; 46:1030-1042. [DOI: 10.1111/j.1558-5646.1992.tb00617.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/1991] [Accepted: 02/24/1992] [Indexed: 11/27/2022]
Affiliation(s)
- B. Devlin
- Division of Biostatistics Laboratory of Epidemiology and Public Health, Yale University P.O. Box 3333 New Haven CT 06510 USA
| | - Janet Clegg
- Department of Botany and Plant Sciences and Program in Genetics University of California, Riverside Riverside CA 92521 USA
| | - N. C. Ellstrand
- Department of Botany and Plant Sciences and Program in Genetics University of California, Riverside Riverside CA 92521 USA
| |
Collapse
|
12
|
Broyles SB, Schnabel A, Wyatt R. EVIDENCE FOR LONG‐DISTANCE POLLEN DISPERSAL IN MILKWEEDS (
ASCLEPIAS EXALTATA
). Evolution 2017; 48:1032-1040. [DOI: 10.1111/j.1558-5646.1994.tb05291.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/1992] [Accepted: 07/02/1993] [Indexed: 11/30/2022]
Affiliation(s)
- Steven B. Broyles
- Department of Biological Sciences SUNY College at Cortland Cortland New York 13045
| | | | - Robert Wyatt
- Department of Botany University of Georgia Athens Georgia 30602
| |
Collapse
|
13
|
Conner JK, Rush S, Kercher S, Jennetten P. MEASUREMENTS OF NATURAL SELECTION ON FLORAL TRAITS IN WILD RADISH (RAPHANUS RAPHANISTRUM). II. SELECTION THROUGH LIFETIME MALE AND TOTAL FITNESS. Evolution 2017; 50:1137-1146. [PMID: 28565276 DOI: 10.1111/j.1558-5646.1996.tb02354.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/1995] [Accepted: 01/26/1996] [Indexed: 11/28/2022]
Abstract
It has often been suggested that selection on floral traits in hermaphroditic plants should occur primarily through differences in male fitness. However, measurements of selection on floral traits through differences in lifetime male fitness have been lacking. We measured selection on a variety of wild radish floral traits using lifetime male fitness measures derived from genetic paternity analysis. These male fitness estimates were then combined with estimates of lifetime female fitness of the same plants to produce measurements of selection based on lifetime total fitness. Contrary to the prediction above, there was no strong evidence for selection on floral morphology through male fitness differences in any of the three years of the study, but there was strong selection for increased flower size through female fitness differences in one year. The main determinant of both male and female fitness in all years was flower number; this lead to moderately positive correlations between male and female fitness in all three years.
Collapse
Affiliation(s)
- Jeffrey K Conner
- Department of Ecology, Ethology, and Evolution, University of Illinois, Shelford Vivarium, 606 East Healey Street, Champaign, Illinois, 61820
| | - Scott Rush
- Department of Ecology, Ethology, and Evolution, University of Illinois, Shelford Vivarium, 606 East Healey Street, Champaign, Illinois, 61820
| | - Suzanne Kercher
- Department of Ecology, Ethology, and Evolution, University of Illinois, Shelford Vivarium, 606 East Healey Street, Champaign, Illinois, 61820
| | - Peter Jennetten
- Department of Ecology, Ethology, and Evolution, University of Illinois, Shelford Vivarium, 606 East Healey Street, Champaign, Illinois, 61820
| |
Collapse
|
14
|
Nakamura RR, Wheeler NC. POLLEN COMPETITION AND PATERNAL SUCCESS IN DOUGLAS‐FIR. Evolution 2017; 46:846-851. [DOI: 10.1111/j.1558-5646.1992.tb02093.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/1990] [Accepted: 08/28/1991] [Indexed: 11/27/2022]
Affiliation(s)
- Robert R. Nakamura
- Department of Botany, KB‐15 University of Washington Seattle WA 98195 USA
| | - Nicholas C. Wheeler
- Weyerhaeuser Company Centralia Research Center P.O. Box 420 Centralia WA 98531 USA
| |
Collapse
|
15
|
La Rosa RJ, Conner JK. Floral function: effects of traits on pollinators, male and female pollination success, and female fitness across three species of milkweeds (Asclepias). AMERICAN JOURNAL OF BOTANY 2017; 104:150-160. [PMID: 28104591 DOI: 10.3732/ajb.1600328] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 12/19/2016] [Indexed: 06/06/2023]
Abstract
PREMISE OF THE STUDY Central questions in plant reproductive ecology are whether the functions of floral traits in hermaphrodites create conflict between sexes that could slow evolution, and whether individual floral traits function in pollinator attraction, efficiency, or both. We studied how floral traits affect pollinator visitation and efficiency, and how they affect male and female function and female fitness within and across three Asclepias species that differ in floral morphology. METHODS Using separate multiple regressions, we regressed pollen removal, deposition, and fruit number onto six floral traits. We also used path analyses integrating these variables with pollinator visitation data for two of the species to further explore floral function and its effects on fruit production. KEY RESULTS Most traits affected male pollination success only, and these effects often differed between species. The exception was increased slit length, which increased pollinia insertion in two of the species. There were no interspecific differences in the effects of the traits on female pollination success. All traits except horn reach affected pollination efficiency in at least one species, and horn reach and two hood dimensions were the only traits to affect pollinator attraction, but in just one species. CONCLUSIONS Traits tended to function in only one sex, and more traits affected function through pollinator efficiency than through attraction. There was no significant link between female pollination success and female fitness in any of the three species; this pattern is consistent with fruit production not being limited by pollen deposition.
Collapse
Affiliation(s)
- Raffica J La Rosa
- W. K. Kellogg Biological Station, Department of Plant Biology, and Program in Ecology, Evolutionary Biology and Behavior, Michigan State University, 3700 E. Gull Lake Dr., Hickory Corners, Michigan 49060
| | - Jeffrey K Conner
- W. K. Kellogg Biological Station, Department of Plant Biology, and Program in Ecology, Evolutionary Biology and Behavior, Michigan State University, 3700 E. Gull Lake Dr., Hickory Corners, Michigan 49060
| |
Collapse
|
16
|
Howard AF, Barrows EM. Self-pollination rate and floral-display size in Asclepias syriaca (Common Milkweed) with regard to floral-visitor taxa. BMC Evol Biol 2014; 14:144. [PMID: 24958132 PMCID: PMC4080991 DOI: 10.1186/1471-2148-14-144] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Accepted: 05/20/2014] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Animals fertilize thousands of angiosperm species whose floral-display sizes can significantly influence pollinator behavior and plant reproductive success. Many studies have measured the interactions among pollinator behavior, floral-display size, and plant reproductive success, but few studies have been able to separate the effects of pollinator behavior and post-pollination processes on angiosperm sexual reproduction. In this study, we utilized the highly self-incompatible pollinium-pollination system of Asclepias syriaca (Common Milkweed) to quantify how insect visitors influenced male reproductive success measured as pollen removal, female reproductive success measured as pollen deposition, and self-pollination rate. We also determined how floral-display size impacts both visitor behavior and self-pollination rate. RESULTS Four insect taxonomic orders visited A. syriaca: Coleoptera, Diptera, Hymenoptera, and Lepidoptera. We focused on three groups of visitor taxa within two orders (Hymenoptera and Lepidoptera) with sample sizes large enough for quantitative analysis: Apis mellifera (Western Honey Bee), Bombus spp. (bumble bees) and lepidopterans (butterflies and moths). Qualitatively, lepidopterans had the highest pollinator importance values, but the large variability in the lepidopteran data precluded meaningful interpretation of much of their behavior. The introduced A. mellifera was the most effective and most important diurnal pollinator with regard to both pollen removal and pollen deposition. However, when considering the self-incompatibility of A. syriaca, A. mellifera was not the most important pollinator because of its high self-pollination rate as compared to Bombus spp. Additionally, the rate of self-pollination increased more rapidly with the number of flowers per inflorescence in A. mellifera than in the native Bombus spp. CONCLUSIONS Apis mellifera's high rate of self-pollination may have significant negative effects on both male and female reproductive successes in A. syriaca, causing different selection on floral-display size than native pollinators.
Collapse
Affiliation(s)
- Aaron F Howard
- Department of Biology, Georgetown University, Box 571229, Washington, DC 20057-1229, USA
| | - Edward M Barrows
- Department of Biology, Georgetown University, Box 571229, Washington, DC 20057-1229, USA
- Center for the Environment, Georgetown University, Box 571229, Washington, DC 20057-1229, USA
| |
Collapse
|
17
|
Pannell JR, Labouche AM. The incidence and selection of multiple mating in plants. Philos Trans R Soc Lond B Biol Sci 2013; 368:20120051. [PMID: 23339242 DOI: 10.1098/rstb.2012.0051] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Mating with more than one pollen donor, or polyandry, is common in land plants. In flowering plants, polyandry occurs when the pollen from different potential sires is distributed among the fruits of a single individual, or when pollen from more than one donor is deposited on the same stigma. Because polyandry typically leads to multiple paternity among or within fruits, it can be indirectly inferred on the basis of paternity analysis using molecular markers. A review of the literature indicates that polyandry is probably ubiquitous in plants except those that habitually self-fertilize, or that disperse their pollen in pollen packages, such as polyads or pollinia. Multiple mating may increase plants' female component by alleviating pollen limitation or by promoting competition among pollen grains from different potential sires. Accordingly, a number of traits have evolved that should promote polyandry at the flower level from the female's point of view, e.g. the prolongation of stigma receptivity or increases in stigma size. However, many floral traits, such as attractiveness, the physical manipulation of pollinators and pollen-dispensing mechanisms that lead to polyandrous pollination, have probably evolved in response to selection to promote male siring success in general, so that polyandry might often best be seen as a by-product of selection to enhance outcross siring success. In this sense, polyandry in plants is similar to geitonogamy (selfing caused by pollen transfer among flowers of the same plant), because both polyandry and geitonogamy probably result from selection to promote outcross siring success, although geitonogamy is almost always deleterious while polyandry in plants will seldom be so.
Collapse
Affiliation(s)
- John R Pannell
- Department of Ecology and Evolution, University of Lausanne, Biophore Building, Lausanne 1015, Switzerland.
| | | |
Collapse
|
18
|
Hodgins KA, Barrett SCH. Natural selection on floral traits through male and female function in wild populations of the heterostylous daffodil Narcissus triandrus. Evolution 2008; 62:1751-1763. [PMID: 18419752 DOI: 10.1111/j.1558-5646.2008.00404.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Measurements of natural selection in hermaphrodite populations require the analysis of performance through both female and male sex functions. Here, we investigate selection on three floral traits: flower number, flower length, and corona width through both sex functions in natural populations of the tristylous daffodil Narcissus triandrus. Selection through female function was examined in six populations, and in two of these we also estimated male selection gradients using multilocus microsatellite genotyping of parents and offspring. We detected significant directional selection for flower number through female function, and significant stabilizing selection for corona width and flower length through male function. Variation in male reproductive success was strongly influenced by the distance between mates and was significantly higher than variation in female reproductive success in one population, a result consistent with Bateman's principle. However, variation through both sex functions was similar in the other population and there was a significant negative correlation between female and male fitness indicating sex-specific trade-offs in reproductive success. Selection on floral design in N. triandrus was stronger through male than female function probably because floral morphology plays an important role in promoting effective cross-pollen transfer in populations of this heterostylous species.
Collapse
Affiliation(s)
- Kathryn A Hodgins
- Department of Ecology & Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, Canada.
| | | |
Collapse
|
19
|
Gérard PR, Klein EK, Austerlitz F, Fernández-Manjarrés JF, Frascaria-Lacoste N. Assortative mating and differential male mating success in an ash hybrid zone population. BMC Evol Biol 2006; 6:96. [PMID: 17107611 PMCID: PMC1660552 DOI: 10.1186/1471-2148-6-96] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2006] [Accepted: 11/15/2006] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND The structure and evolution of hybrid zones depend mainly on the relative importance of dispersal and local adaptation, and on the strength of assortative mating. Here, we study the influence of dispersal, temporal isolation, variability in phenotypic traits and parasite attacks on the male mating success of two parental species and hybrids by real-time pollen flow analysis. We focus on a hybrid zone population between the two closely related ash species Fraxinus excelsior L. (common ash) and F. angustifolia Vahl (narrow-leaved ash), which is composed of individuals of the two species and several hybrid types. This population is structured by flowering time: the F. excelsior individuals flower later than the F. angustifolia individuals, and the hybrid types flower in-between. Hybrids are scattered throughout the population, suggesting favorable conditions for their local adaptation. We estimate jointly the best-fitting dispersal kernel, the differences in male fecundity due to variation in phenotypic traits and level of parasite attack, and the strength of assortative mating due to differences in flowering phenology. In addition, we assess the effect of accounting for genotyping error on these estimations. RESULTS We detected a very high pollen immigration rate and a fat-tailed dispersal kernel, counter-balanced by slight phenological assortative mating and short-distance pollen dispersal. Early intermediate flowering hybrids, which had the highest male mating success, showed optimal sex allocation and increased selfing rates. We detected asymmetry of gene flow, with early flowering trees participating more as pollen donors than late flowering trees. CONCLUSION This study provides striking evidence that long-distance gene flow alone is not sufficient to counter-act the effects of assortative mating and selfing. Phenological assortative mating and short-distance dispersal can create temporal and spatial structuring that appears to maintain this hybrid population. The asymmetry of gene flow, with higher fertility and increased selfing, can potentially confer a selective advantage to early flowering hybrids in the zone. In the event of climate change, hybridization may provide a means for F. angustifolia to further extend its range at the expense of F. excelsior.
Collapse
Affiliation(s)
- Pierre R Gérard
- Laboratoire Ecologie, Systématique, Evolution, UMR ENGREF-CNRS 8079, Bât. 360, Université Paris-Sud, 91405 Orsay Cedex, France
| | - Etienne K Klein
- Unité de Biométrie, INRA, Domaine St-Paul, Site Agroparc, 84914 Avignon cedex 9, France
| | - Frédéric Austerlitz
- Laboratoire Ecologie, Systématique, Evolution, UMR ENGREF-CNRS 8079, Bât. 360, Université Paris-Sud, 91405 Orsay Cedex, France
| | - Juan F Fernández-Manjarrés
- Laboratoire Ecologie, Systématique, Evolution, UMR ENGREF-CNRS 8079, Bât. 360, Université Paris-Sud, 91405 Orsay Cedex, France
| | - Nathalie Frascaria-Lacoste
- Laboratoire Ecologie, Systématique, Evolution, UMR ENGREF-CNRS 8079, Bât. 360, Université Paris-Sud, 91405 Orsay Cedex, France
| |
Collapse
|
20
|
Trapnell DW, Hamrick JL. Floral display and mating patterns within populations of the neotropical epiphytic orchid,Laeliarubescens (Orchidaceae). AMERICAN JOURNAL OF BOTANY 2006; 93:1010-1018. [PMID: 21642166 DOI: 10.3732/ajb.93.7.1010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Pollinator behavior plays a central role in determining patterns of pollen-mediated gene movement in zoophilous angiosperms. A species' floral display can strongly influence the behavior of its pollinators and thereby affect its evolutionary pathway. We used paternity analysis to directly measure and describe mating patterns within 15 populations of the epiphytic orchid, Laelia rubescens, in Costa Rican dry forest. Strict correlated mating by orchids allows inference of the precise multilocus diploid genotype of the pollen parents. Our data show that mean effective population sizes were small (11.2 in 1999 and 11.8 in 2000) relative to the number of flowering genets (63 and 56, respectively). Fewer genets were reproductively successful as females than males. The relationship between reproductive success (RS) and floral display within three cluster size classes was consistent between years, with large (>30 inflorescences) and small (≤10 inflorescences) clusters often having significantly lower RS than expected, while the RS of medium-sized clusters (11-30 inflorescences) often significantly exceeded expectations. Paternity analysis allowed us to take advantage of the pollination biology of L. rubescens to provide unusually detailed insights into mating patterns, pollen-mediated gene movement and RS for populations of this epiphytic orchid, an herbaceous perennial, distributed in three-dimensional space.
Collapse
Affiliation(s)
- Dorset W Trapnell
- Department of Plant Biology, University of Georgia, Athens, Georgia 30602 USA
| | | |
Collapse
|
21
|
Verdú M, Gleiser G. Adaptive evolution of reproductive and vegetative traits driven by breeding systems. THE NEW PHYTOLOGIST 2006; 169:409-17. [PMID: 16411943 DOI: 10.1111/j.1469-8137.2005.01586.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The evolution of inflorescence size, a key trait in reproductive success, was studied in the genus Acer under a perspective of adaptive evolution. Breeding systems, hypothesized to indicate different levels of mating competition, were considered as the selective scenarios defining different optima of inflorescence size. Larger inflorescences, which increase male fitness by generating larger floral displays, were hypothesized to be selected under scenarios with higher competition with unisexuals. An identical approach was used to test if the same selective regimes could be driving the evolution of leaf size, a vegetative trait that was found to be correlated with inflorescence size. A Brownian motion model of inflorescence/leaf-size evolution (which cannot distinguish between changes caused by pure drift processes and changes caused by natural selection in rapidly and randomly changing environments) was compared with several adaptive Ornstein-Uhlenbeck (OU) models, which can quantify the effects of both stochasticity and natural selection. The best-fitting model for inflorescence/leaf-size evolution was an OU model with three optima that increased with the level of mating competition. Both traits evolved under the same selective regimes and in the same direction, confirming a pattern of correlated evolution. These results show that a selective regime hypothetically related to the evolution of a reproductive trait can also explain the evolution of a vegetative trait.
Collapse
Affiliation(s)
- Miguel Verdú
- Centro de Investigaciones sobre Desertificación (CSIC-UV-GV), Camí de la Marjal s/n Apartado Oficial, 46470 Albal (Valencia), Spain.
| | | |
Collapse
|
22
|
Mitchell RJ, Karron JD, Holmquist KG, Bell JM. Patterns of multiple paternity in fruits of Mimulus ringens (Phrymaceae). AMERICAN JOURNAL OF BOTANY 2005; 92:885-890. [PMID: 21652470 DOI: 10.3732/ajb.92.5.885] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Multiply sired fruits provide unambiguous evidence that pollen from two or more donors was deposited on a stigma and successfully fertilized ovules. Such multiple paternity within fruits can have important consequences for both parental and offspring fitness, but little is known about the frequency of multiple paternity or the mechanisms causing it. In this study we quantify the extent of multiple paternity in replicate experimental arrays of Mimulus ringens (square-stem monkeyflower) and use observations of pollinator behavior to infer mechanisms generating multiply sired fruits. In each array, floral displays were trimmed to two, four, eight, or 16 flowers per plant to span the range of display sizes observed in nature. In our sample of 204 fruits, more than 95% had two or more outcross pollen donors. The number of sires per fruit averaged 4.63 ± 0.10 (mean ± 1 SE), including selfs, and did not vary significantly with floral display treatment. Patterns of bumble bee foraging, combined with limited pollen carryover, suggest that observed levels of multiple paternity cannot be fully explained by single probes that deposited mixed pollen loads. Multiple probes to flowers, each delivering pollen from 1-3 different sires, are more likely to have caused the observed patterns. These sequential visits may reduce the potential for pollen competition and female choice based on pollen tube growth rate.
Collapse
|
23
|
Finer MS, Morgan MT. Effects of natural rates of geitonogamy on fruit set in Asclepias speciosa (Apocynaceae): evidence favoring the plant's dilemma. AMERICAN JOURNAL OF BOTANY 2003; 90:1746-1750. [PMID: 21653351 DOI: 10.3732/ajb.90.12.1746] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The role of geitonogamy in the evolution of inflorescence design is not well understood. The plant's dilemma hypothesis proposes that evolution of larger inflorescences is driven by selection for greater pollinator attraction, but constrained by higher rates of geitonogamy experienced by larger inflorescences. Here we investigate the role of geitonogamy on fruit set in natural populations of Asclepias speciosa. We compared fruit set from three pollination treatments: (1) inflorescences bagged before and after receiving 6 hand outcross pollinia (Bag), (2) inflorescences unbagged and receiving 6 hand outcross pollinia (Open), and (3) naturally pollinated inflorescences (Control). The Bag and Open treatments initiated significantly more fruits than the Control. Bag aborted significantly fewer fruits than Open or Control. Fruit set was significantly higher in Bag than Open, and Open had significantly higher fruit set than Control. From these results, we conclude that (1) high rates of geitonogamy significantly increase fruit abortion and reduce fruit set in natural populations of A. speciosa and (2) natural populations are compatible pollen limited. Both findings are consistent with the plant's dilemma hypothesis.
Collapse
Affiliation(s)
- Matthew S Finer
- School of Biological Sciences, Washington State University, Pullman, WA, 99164-4236
| | | |
Collapse
|
24
|
Fritz AL, Nilsson LA. How pollinator-mediated mating varies with population size in plants. Oecologia 1994; 100:451-462. [PMID: 28306934 DOI: 10.1007/bf00317867] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/1994] [Accepted: 06/26/1994] [Indexed: 11/29/2022]
Abstract
In most higher plants sexual interactions are mediated by animal pollinators that affect the number and differential reproductive success of mates. The number and sex of breeding individuals in populations are central factors in evolutionary theory, but the quantitative effect of plant population size on pollinator-mediated mating is understudied. We investigated variation in pollen removal (male function) and fruit set (female function) among flowering populations of different size of two bumblebee-and one butterfly-pollinated, rewardless, pollen-limited, hermaphroditic orchid species in Sweden. As the amount of pollen removed from plants by insects (either absolute or proportional) increased, so did the number of pollinations, whereas the proportions of plants with different pollinator-designated functional sex (male, female, hermaphrodite) depended primarily on the ratio between the amount of fruit set and pollen removed within populations. A larger population size was found to have several effects: (1) the total numbers of pollinia removed and fruits set increased; (2) the proportion of pollen removed from plants decreased; (3) the proportion of flowers pollinated decreased in the butterfly-but was not affected in the bumblebee-pollinated species; (4) the ratio between fruits set and pollinia removed increased linearly in the bumblebee-pollinated species but reached a maximum at c. 80 individuals in the butterfly-pollinated species; (5) the numbers of pollinator-designated pure male and hermaphrodite individuals increased; and (6) the variance in pollinium removal, but not fruit set, increased among individuals. These findings empirically verify the basic importance of population size for the mating structure of outcrossing plants, and indicate that selection for female sexual traits is reinforced when population size is smaller while selection for male sexual traits is reinforced when population size is larger.
Collapse
Affiliation(s)
- Anna-Lena Fritz
- Department of Systematic Botany, Villavägen 6, S-752 36, Uppsala, Sweden
| | - L Anders Nilsson
- Department of Systematic Botany, Villavägen 6, S-752 36, Uppsala, Sweden
| |
Collapse
|
25
|
Ashman TL, Galloway LF, Stanton ML. Apparent vs. effective mating in an experimental population of Raphanus sativus. Oecologia 1993; 96:102-107. [PMID: 28313759 DOI: 10.1007/bf00318036] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/1992] [Accepted: 07/15/1993] [Indexed: 11/29/2022]
Abstract
Effective mating in plant populations need not occur during periods of peak pollinator activity and flowering. We measured seasonal and diurnal patterns of pollinator activity, pollen and ovule availability, and seed production in an experimental population of Raphanus sativus to infer the times of reproductively effective mating. On a seasonal scale, we found that most "effective matings", those resulting in mature seeds, occurred very early in the season, well before the peak of flowering and pollinator activity. At a finer scale, diurnal schedules of flower opening, stigma saturation with pollen, and pollen removal indicated that most effective matings occurred before noon, even though pollinator activity increased later in the day. These patterns may be most common in populations that are not pollen limited, but other ecological factors (e.g. seed predation, resource depletion) could weaken the correspondence between pollination and effective mating.
Collapse
Affiliation(s)
- Tia-Lynn Ashman
- Botany Department, University of California, 95616, Davis, CA, USA
| | - Laura F Galloway
- Botany Department, University of California, 95616, Davis, CA, USA
| | | |
Collapse
|