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Lee Y, Kato S, Kim JY, Shimono Y, Shiga T. Two lineages of Lemna aequinoctialis (Araceae, Lemnoideae) based on physiology, morphology, and phylogeny. JOURNAL OF PLANT RESEARCH 2024; 137:359-376. [PMID: 38349478 DOI: 10.1007/s10265-023-01509-w] [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: 04/24/2023] [Accepted: 11/08/2023] [Indexed: 05/12/2024]
Abstract
Lemna aequinoctialis Welw. is a widely spread species that has diverse physiological and molecular properties. Flower characteristics are important factors in deducing taxonomical status; however, owing to the rarity of flowering observations in Lemna, studying them has been a prolonged challenge. In this study, physiological and morphological analyses were conducted by inducing flowering, and molecular analysis was done based on the two chloroplast DNA loci (matK, atpF-atpH intergeneric spacer) of L. aequinoctialis sensu Landolt (1986) from 70 strains found in 70 localities in Japan, Korea, Thailand, and the US. In total, 752 flowering fronds from 13 strains were observed based on axenic conditions. Two different trends in flower organ development-protogyny and adichogamy-were detected in these strains. Their physiological traits were divided into two groups, showing different morphological features based on frond thickness, root cap, and anther sizes. Molecular analysis showed two lineages corresponding to two physiological groups. These were identified as L. aequinoctialis sensu Beppu et al. (1985) and L. aoukikusa Beppu et Murata based on the description of the nomenclature of L. aoukikusa. These were concluded as independent taxa and can be treated as different species. Furthermore, the distribution of L. aoukikusa is not only limited to Japan.
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Affiliation(s)
- Yuri Lee
- Graduate School of Science and Technology, Niigata University, Ikarashi Ninocho, Nishi-ku, Niigata, 950-2181, Japan
- Faculty of Education, Niigata University, Ikarashi Ninocho, Nishi-ku, Niigata, 950-2181, Japan
| | - Syou Kato
- Faculty of Education, Niigata University, Ikarashi Ninocho, Nishi-ku, Niigata, 950-2181, Japan
| | - Jae Young Kim
- Division of Horticulture and Medicinal Plant, Andong National University, Andong, 36729, Republic of Korea
| | - Yoshiko Shimono
- Graduate School of Agriculture, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Takashi Shiga
- Graduate School of Science and Technology, Niigata University, Ikarashi Ninocho, Nishi-ku, Niigata, 950-2181, Japan.
- Faculty of Education, Niigata University, Ikarashi Ninocho, Nishi-ku, Niigata, 950-2181, Japan.
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Zhang D, Li YY, Zhao X, Zhang C, Liu DK, Lan S, Yin W, Liu ZJ. Molecular insights into self-incompatibility systems: From evolution to breeding. PLANT COMMUNICATIONS 2024; 5:100719. [PMID: 37718509 PMCID: PMC10873884 DOI: 10.1016/j.xplc.2023.100719] [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: 03/29/2023] [Revised: 08/18/2023] [Accepted: 09/13/2023] [Indexed: 09/19/2023]
Abstract
Plants have evolved diverse self-incompatibility (SI) systems for outcrossing. Since Darwin's time, considerable progress has been made toward elucidating this unrivaled reproductive innovation. Recent advances in interdisciplinary studies and applications of biotechnology have given rise to major breakthroughs in understanding the molecular pathways that lead to SI, particularly the strikingly different SI mechanisms that operate in Solanaceae, Papaveraceae, Brassicaceae, and Primulaceae. These best-understood SI systems, together with discoveries in other "nonmodel" SI taxa such as Poaceae, suggest a complex evolutionary trajectory of SI, with multiple independent origins and frequent and irreversible losses. Extensive exploration of self-/nonself-discrimination signaling cascades has revealed a comprehensive catalog of male and female identity genes and modifier factors that control SI. These findings also enable the characterization, validation, and manipulation of SI-related factors for crop improvement, helping to address the challenges associated with development of inbred lines. Here, we review current knowledge about the evolution of SI systems, summarize key achievements in the molecular basis of pollen‒pistil interactions, discuss potential prospects for breeding of SI crops, and raise several unresolved questions that require further investigation.
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Affiliation(s)
- Diyang Zhang
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Yuan-Yuan Li
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Xuewei Zhao
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization, Fujian Agriculture and Forestry University, Fuzhou 350002, China; College of Forestry, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Cuili Zhang
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Ding-Kun Liu
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization, Fujian Agriculture and Forestry University, Fuzhou 350002, China; College of Forestry, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Siren Lan
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Weilun Yin
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization, Fujian Agriculture and Forestry University, Fuzhou 350002, China; College of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, China.
| | - Zhong-Jian Liu
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
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Simón-Porcar V, Escudero M, Santos-Gally R, Sauquet H, Schönenberger J, Johnson SD, Arroyo J. Convergent evolutionary patterns of heterostyly across angiosperms support the pollination-precision hypothesis. Nat Commun 2024; 15:1237. [PMID: 38336937 PMCID: PMC10858259 DOI: 10.1038/s41467-024-45118-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 01/12/2024] [Indexed: 02/12/2024] Open
Abstract
Since the insights by Charles Darwin, heterostyly, a floral polymorphism with morphs bearing stigmas and anthers at reciprocal heights, has become a model system for the study of natural selection. Based on his archetypal heterostylous flower, including regular symmetry, few stamens and a tube, Darwin hypothesised that heterostyly evolved to promote outcrossing through efficient pollen transfer between morphs involving different areas of a pollinator's body, thus proposing his seminal pollination-precision hypothesis. Here we update the number of heterostylous and other style-length polymorphic taxa to 247 genera belonging to 34 families, notably expanding known cases by 20%. Using phylogenetic and comparative analyses across the angiosperms, we show numerous independent origins of style-length polymorphism associated with actinomorphic, tubular flowers with a low number of sex organs, stamens fused to the corolla, and pollination by long-tongued insects. These associations provide support for the Darwinian pollination-precision hypothesis as a basis for convergent evolution of heterostyly across angiosperms.
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Affiliation(s)
- Violeta Simón-Porcar
- Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, E-41080, Sevilla, Spain.
- School of Life Sciences, University of KwaZulu-Natal, P Bag X01, Scottsville, Pietermaritzburg, 3209, South Africa.
| | - Marcial Escudero
- Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, E-41080, Sevilla, Spain
| | | | - Hervé Sauquet
- National Herbarium of New South Wales, Royal Botanic Gardens and Domain Trust, Sydney, NSW, Australia
| | - Jürg Schönenberger
- Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, 1030, Vienna, Austria
| | - Steven D Johnson
- School of Life Sciences, University of KwaZulu-Natal, P Bag X01, Scottsville, Pietermaritzburg, 3209, South Africa
| | - Juan Arroyo
- Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, E-41080, Sevilla, Spain.
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Ferrer MM, Vásquez-Cruz M, Hernández-Hernández T, Good SV. Geographical and life-history traits associated with low and high species richness across angiosperm families. FRONTIERS IN PLANT SCIENCE 2023; 14:1276727. [PMID: 38107007 PMCID: PMC10722503 DOI: 10.3389/fpls.2023.1276727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/12/2023] [Accepted: 10/26/2023] [Indexed: 12/19/2023]
Abstract
Introduction The phenomenal expansion of angiosperms has prompted many investigations into the factors driving their diversification, but there remain significant gaps in our understanding of flowering plant species diversity. Methods Using the crown age of families from five studies, we used a maximum likelihood approach to classify families as having poor, predicted or high species richness (SR) using strict consensus criteria. Using these categories, we looked for associations between family SR and i) the presence of an inferred familial ancestral polyploidization event, ii) 23 life history and floral traits compiled from previously published datasets and papers, and iii) sexual system (dioecy) or genetically determined self-incompatibility (SI) mating system using an updated version of our own database and iv) geographic distribution using a new database describing the global distribution of plant species/families across realms and biomes and inferred range. Results We find that more than a third of angiosperm families (65%) had predicted SR, a large proportion (30.2%) were species poor, while few (4.8%) had high SR. Families with poor SR were less likely to have undergone an ancestral polyploidization event, exhibited deficits in diverse traits, and were more likely to have unknown breeding systems and to be found in only one or few biomes and realms, especially the Afrotropics or Australasia. On the other hand, families with high SR were more likely to have animal mediated pollination or dispersal, are enriched for epiphytes and taxa with an annual life history, and were more likely to harbour sporophytic SI systems. Mapping the global distribution of georeferenced taxa by their family DR, we find evidence of regions dominated by taxa from lineages with high vs low SR. Discussion These results are discussed within the context of the literature describing "depauperons" and the factors contributing to low and high biodiversity in angiosperm clades.
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Affiliation(s)
- Miriam Monserrat Ferrer
- Departamento de Manejo y Conservación de Recursos Naturales Tropicales, Universidad Autónoma de Yucatán, Mérida Yucatán, Mexico
| | | | | | - Sara V. Good
- Department of Biology, The University of Winnipeg, Winnipeg, MB, Canada
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Nyadanu D, Lowor ST, Pobee P, Dogbatse JA, Akpertey A, Brarko-Marfo M. Heterosis patterns and sources of self-compatibility, cross-compatibility and key nut traits within single and double hybrid crosses of kola [Cola nitida (Vent) Schott and Endl.]. Sci Rep 2023; 13:8036. [PMID: 37198219 DOI: 10.1038/s41598-023-30485-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 02/23/2023] [Indexed: 05/19/2023] Open
Abstract
Sexual incompatibility among kola genotypes accounted for over 50% yield loss. Compatible and high yielding varieties are in demand to develop commercial orchards. The objective of this study was to assess self-compatibility and cross-compatibility of kola (C. nitida) genotypes within self, single and double hybrid crosses and to determine heterosis pattern in the resulting hybrids for sexual compatibility and key nut yield and quality traits. Crosses among kola genotypes from three field gene banks (JX1, GX1, MX2) and one advanced germplasm (Bunso progeny) in Ghana were evaluated along their parents for sexual compatibility, nut yield and nut quality. Data were collected on pod set, pseudo-pod set, pod weight, number of nuts per pod, nut weight, brix, potential alcohol and nut firmness. Significant (P < 0.001) differential pod set was observed within Bunso progeny, JX1, GX1 and MX2 crosses; while pseudo-pod set differed only within JX1 and MX2 crosses (P < 0.001). Very large prevalence of mid-parent, heterobeltiosis, and economic heterosis was observed for sexual compatibility, outturn and brix for the single and double hybrid crosses. Heterosis was prominent among the double hybrid crosses as compared to the single hybrid crosses suggesting that recurrent selection of compatible varieties from advanced generations could result in genetic gain in kola improvement. The top five crosses with best heterosis for sexual compatibility and an appreciable positive heterosis for outturn and brix were B1/11 × B1/71 × B1/157 × B1/149, B1/11 × B1/71 × B1/296 × B1/177, GX1/46 × GX1/33 × B1/212 × B1/236, JX1/90 × JX1/51 and JX1/51 × JX1/36. These materials could serve as sources of beneficial alleles for improving Ghanaian kola hybrids and populations for yield and sexual compatibility.
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Affiliation(s)
- Daniel Nyadanu
- Cocoa Research Institute of Ghana, P. O. Box 8, Akim Tafo, Ghana.
| | | | - Prince Pobee
- Cocoa Research Institute of Ghana, P. O. Box 8, Akim Tafo, Ghana
| | | | - Abraham Akpertey
- Cocoa Research Institute of Ghana, P. O. Box 8, Akim Tafo, Ghana
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Cisternas-Fuentes A, Dwyer R, Johnson N, Finnell L, Gilman J, Koski MH. Disentangling the components of pollen limitation in a widespread herb with gametophytic self-incompatibility. AMERICAN JOURNAL OF BOTANY 2023; 110:e16122. [PMID: 36571452 DOI: 10.1002/ajb2.16122] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 12/12/2022] [Accepted: 12/14/2022] [Indexed: 06/17/2023]
Abstract
PREMISE Seed production is frequently limited by the receipt of insufficient or low-quality pollen, collectively termed "pollen limitation" (PL). In taxa with gametophytic self-incompatibility (GSI), incompatible pollen can germinate on stigmas but pollen tubes are arrested in styles. This allows for estimates of pollen performance before, during, and after self-recognition, as well as insight into the factors underlying pollen quality limitation in GSI taxa. METHODS We scored pollen performance following self and outcross pollinations in Argentina anserina to identify the location of self-recognition and establish the relationship between pollen tubes and seed production. We then estimated quantity and quality components of PL from >3300 field-collected styles. We combined our results with other studies to test the prediction that low pollen quality, but not quantity, drives higher PL in self-incompatible (SI) taxa than in self-compatible taxa (SC). RESULTS Self and outcross pollen germinated readily on stigmas, but 96% of germinated self-pollen was arrested during early tube elongation. Reproduction in the field was more limited by pollen quality than by quantity, and pollen failure near the location of self-recognition was a stronger barrier to fertilization than pollen germination. Across 26 taxa, SI species experienced stronger pollen quality, but not quantity, limitation than SC species. CONCLUSIONS Evaluating pollen performance at multiple points within pistils can elucidate potential causes of pollen quality limitation. The receipt of incompatible pollen inhibits fertilization success more than insufficient pollen receipt or poor pollen germination in A. anserina. Likewise, pollen quality limitation drives high overall PL in other SI taxa.
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Affiliation(s)
- Anita Cisternas-Fuentes
- Department of Biological Sciences, 132 Long Hall, Clemson University, Clemson, South Carolina, 29634, USA
| | - Roslynn Dwyer
- Department of Biological Sciences, 132 Long Hall, Clemson University, Clemson, South Carolina, 29634, USA
| | - Nicole Johnson
- Department of Biological Sciences, 132 Long Hall, Clemson University, Clemson, South Carolina, 29634, USA
| | - Lindsay Finnell
- Department of Biological Sciences, 132 Long Hall, Clemson University, Clemson, South Carolina, 29634, USA
| | - Jeffrey Gilman
- Department of Biological Sciences, 132 Long Hall, Clemson University, Clemson, South Carolina, 29634, USA
| | - Matthew H Koski
- Department of Biological Sciences, 132 Long Hall, Clemson University, Clemson, South Carolina, 29634, USA
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7
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Pollinator Communities of Planted and Feral Pyrus calleryana. ECOLOGIES 2022. [DOI: 10.3390/ecologies4010001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Pyrus calleryana was intentionally introduced to North America from east Asia in the early 1900s as rootstock for the edible pear tree, Pyrus communis. It was identified as an ideal decorative, agricultural, and horticultural tree because of its small stature, early spring flowering, fire blight resistance and inoffensive fruits. P. calleryana escaped cultivation and is now considered an invasive species, typically found on roadsides, prairies, and fields. The aim of this study is to characterize pollinator community diversity from planted and feral trees, as well as diversity as it compares to expected communities derived from research-grade iNaturalist observations. Pollinators were collected by hand on planted and feral P. calleryana trees in April 2018–2022. A total of 14 taxa of insect pollinator were collected from P. calleryana flowers, with similar levels of diversity of pollinator taxa collected from planted and feral trees, and Apis mellifera and Andrena spp. the most common taxa observed. The sampled pollinator community did not differ from the expected pollinator communities generated using the iNaturalist data on either the planted or feral P. calleryana.
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Heywood JS, Michalski JS, McCann BK, Andres KJ, Hall AR, Hartman AD, Middleton TC, Chiles A, Dewey SE, Miller CA. The potential for floral evolution in response to competing selection pressures following the loss of hawkmoth pollination in Ruellia humilis. AMERICAN JOURNAL OF BOTANY 2022; 109:1875-1892. [PMID: 36063430 DOI: 10.1002/ajb2.16063] [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: 01/05/2022] [Revised: 07/26/2022] [Accepted: 07/27/2022] [Indexed: 06/15/2023]
Abstract
PREMISE In the absence of hawkmoth pollinators, chasmogamous (CH) flowers of Ruellia humilis self-pollinate by two secondary mechanisms. Other floral visitors might exert selection on CH floral traits to restore outcrossing, but at the same time preferential predation of CH seeds generates selection to increase the allocation of resources to cleistogamous (CL) flowers. METHODS To assess the potential for an evolutionary response to these competing selection pressures, we estimated additive genetic variances ( σ A 2 ${\sigma }_{{\rm{A}}}^{2}$ ) and covariances for 14 reproductive traits and three fitness components in a Missouri population lacking hawkmoth pollinators. RESULTS We found significant σ A 2 ${\sigma }_{{\rm{A}}}^{2}$ for all 11 floral traits and two measures of resource allocation to CL flowers, indicating the potential for a short-term response to selection on most reproductive traits. Selection generated by seed predators is predicted to increase the percentage of CL flowers by 0.24% per generation, and mean stigma-anther separation is predicted to decrease as a correlated response, increasing the fraction of plants that engage in prior selfing. However, the initial response to this selection is opposed by strong directional dominance. CONCLUSIONS The predicted evolutionary decrease in the number of CH flowers available for potential outcrossing, combined with the apparent preclusion of potential diurnal pollinators by the pollen-harvesting activities of sweat bees, suggest that 100% cleistogamy is the likely outcome of evolution in the absence of hawkmoths. However, rare mutations with large effects, such as delaying budbreak until after sunrise, could provide pathways for the restoration of outcrossing that are not reachable by gradual quantitative-genetic evolution.
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Affiliation(s)
- John S Heywood
- Biology Department, Missouri State University, 901 S National Ave., Springfield, MO, 65897, USA
| | - Joseph S Michalski
- Biology Department, Missouri State University, 901 S National Ave., Springfield, MO, 65897, USA
| | - Braden K McCann
- Biology Department, Missouri State University, 901 S National Ave., Springfield, MO, 65897, USA
| | - Kara J Andres
- Biology Department, Missouri State University, 901 S National Ave., Springfield, MO, 65897, USA
- Department of Ecology and Evolutionary Biology, Cornell University, 215 Tower Rd., Ithaca, NY, 14853, USA
| | - Allison R Hall
- Biology Department, Missouri State University, 901 S National Ave., Springfield, MO, 65897, USA
| | - Amber D Hartman
- Biology Department, Missouri State University, 901 S National Ave., Springfield, MO, 65897, USA
| | - Tessa C Middleton
- Biology Department, Missouri State University, 901 S National Ave., Springfield, MO, 65897, USA
| | - Amelia Chiles
- Biology Department, Missouri State University, 901 S National Ave., Springfield, MO, 65897, USA
| | - Sarah E Dewey
- Biology Department, Missouri State University, 901 S National Ave., Springfield, MO, 65897, USA
| | - Cay A Miller
- Biology Department, Missouri State University, 901 S National Ave., Springfield, MO, 65897, USA
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Lizamore D, Bicknell R, Winefield C. Elevated transcription of transposable elements is accompanied by het-siRNA-driven de novo DNA methylation in grapevine embryogenic callus. BMC Genomics 2021; 22:676. [PMID: 34544372 PMCID: PMC8454084 DOI: 10.1186/s12864-021-07973-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 09/03/2021] [Indexed: 11/10/2022] Open
Abstract
Background Somatic variation is a valuable source of trait diversity in clonally propagated crops. In grapevine, which has been clonally propagated worldwide for centuries, important phenotypes such as white berry colour are the result of genetic changes caused by transposable elements. Additionally, epiallele formation may play a role in determining geo-specific (‘terroir’) differences in grapes and thus ultimately in wine. This genomic plasticity might be co-opted for crop improvement via somatic embryogenesis, but that depends on a species-specific understanding of the epigenetic regulation of transposable element (TE) expression and silencing in these cultures. For this reason, we used whole-genome bisulphite sequencing, mRNA sequencing and small RNA sequencing to study the epigenetic status and expression of TEs in embryogenic callus, in comparison with leaf tissue. Results We found that compared with leaf tissue, grapevine embryogenic callus cultures accumulate relatively high genome-wide CHH methylation, particularly across heterochromatic regions. This de novo methylation is associated with an abundance of transcripts from highly replicated TE families, as well as corresponding 24 nt heterochromatic siRNAs. Methylation in the TE-specific CHG context was relatively low over TEs located within genes, and the expression of TE loci within genes was highly correlated with the expression of those genes. Conclusions This multi-‘omics analysis of grapevine embryogenic callus in comparison with leaf tissues reveals a high level of genome-wide transcription of TEs accompanied by RNA-dependent DNA methylation of these sequences in trans. This provides insight into the genomic conditions underlying somaclonal variation and epiallele formation in plants regenerated from embryogenic cultures, which is an important consideration when using these tissues for plant propagation and genetic improvement. Supplementary Information The online version contains supplementary material available at 10.1186/s12864-021-07973-9.
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Affiliation(s)
| | - Ross Bicknell
- Plant and Food Research Ltd, Lincoln, Canterbury, New Zealand
| | - Chris Winefield
- Department Wine, Food and Molecular Biosciences, Lincoln University, Canterbury, New Zealand.
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Hughes PW. The means of reproduction: Book Review of Fusco, G. and A.Minelli. 2019. The Biology of Reproduction. Cambridge University Press, Cambridge, UK. xviii + 472 pp. ISBN: 978‐1‐10‐8758970. $47 USD. Evolution 2020. [DOI: 10.1111/evo.14053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- P. William Hughes
- Department of Ecology, Environment, and Plant Sciences Stockholm University Stockholm Sweden
- SciLifeLab Stockholm Sweden
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11
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Durand E, Chantreau M, Le Veve A, Stetsenko R, Dubin M, Genete M, Llaurens V, Poux C, Roux C, Billiard S, Vekemans X, Castric V. Evolution of self-incompatibility in the Brassicaceae: Lessons from a textbook example of natural selection. Evol Appl 2020; 13:1279-1297. [PMID: 32684959 PMCID: PMC7359833 DOI: 10.1111/eva.12933] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 01/25/2020] [Accepted: 01/29/2020] [Indexed: 12/14/2022] Open
Abstract
Self-incompatibility (SI) is a self-recognition genetic system enforcing outcrossing in hermaphroditic flowering plants and results in one of the arguably best understood forms of natural (balancing) selection maintaining genetic variation over long evolutionary times. A rich theoretical and empirical population genetics literature has considerably clarified how the distribution of SI phenotypes translates into fitness differences among individuals by a combination of inbreeding avoidance and rare-allele advantage. At the same time, the molecular mechanisms by which self-pollen is specifically recognized and rejected have been described in exquisite details in several model organisms, such that the genotype-to-phenotype map is also pretty well understood, notably in the Brassicaceae. Here, we review recent advances in these two fronts and illustrate how the joint availability of detailed characterization of genotype-to-phenotype and phenotype-to-fitness maps on a single genetic system (plant self-incompatibility) provides the opportunity to understand the evolutionary process in a unique perspective, bringing novel insight on general questions about the emergence, maintenance, and diversification of a complex genetic system.
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Affiliation(s)
| | | | - Audrey Le Veve
- CNRSUniv. LilleUMR 8198 ‐ Evo‐Eco‐PaleoF-59000 LilleFrance
| | | | - Manu Dubin
- CNRSUniv. LilleUMR 8198 ‐ Evo‐Eco‐PaleoF-59000 LilleFrance
| | - Mathieu Genete
- CNRSUniv. LilleUMR 8198 ‐ Evo‐Eco‐PaleoF-59000 LilleFrance
| | - Violaine Llaurens
- Institut de Systématique, Evolution et Biodiversité (ISYEB)Muséum national d'Histoire naturelleCNRS, Sorbonne Université, EPHE, Université des Antilles CP 5057 rue Cuvier, 75005 ParisFrance
| | - Céline Poux
- CNRSUniv. LilleUMR 8198 ‐ Evo‐Eco‐PaleoF-59000 LilleFrance
| | - Camille Roux
- CNRSUniv. LilleUMR 8198 ‐ Evo‐Eco‐PaleoF-59000 LilleFrance
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Levin DA. Has the Polyploid Wave Ebbed? FRONTIERS IN PLANT SCIENCE 2020; 11:251. [PMID: 32211006 PMCID: PMC7077508 DOI: 10.3389/fpls.2020.00251] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 02/18/2020] [Indexed: 05/13/2023]
Abstract
There was a wave of whole genome duplications (WGD) during and subsequent to the K-Pg interface, which was followed by an increase in the proportion of species that were polyploid. I consider why this wave of polyploid speciation has continued to rise through the divergent evolution of polyploid lineages, and through rounds of homoploid and heteroploid chromosomal change. I also consider why the polyploid speciation wave is likely to rise in the next millennium. I propose that the speed of polyploid genesis through ploidal increase and through diversification among polyploids likely will be greater than the speed of diploid speciation. The increase in polyploid diversity is expected to lag well behind episodes of WGD, owing to the very long period required for species diversification either by lineage splitting or additional rounds of polyploidy, in addition to the long period of genomic adjustment to higher ploidal levels in neopolyploids.
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Affiliation(s)
- Donald A. Levin
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, United States
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Alagna F, Caceres ME, Pandolfi S, Collani S, Mousavi S, Mariotti R, Cultrera NGM, Baldoni L, Barcaccia G. The Paradox of Self-Fertile Varieties in the Context of Self-Incompatible Genotypes in Olive. FRONTIERS IN PLANT SCIENCE 2019; 10:725. [PMID: 31293602 PMCID: PMC6606695 DOI: 10.3389/fpls.2019.00725] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 05/16/2019] [Indexed: 05/09/2023]
Abstract
Olive, representing one of the most important fruit crops of the Mediterranean area, is characterized by a general low fruit yield, due to numerous constraints, including alternate bearing, low flower viability, male-sterility, inter-incompatibility, and self-incompatibility (SI). Early efforts to clarify the genetic control of SI in olive gave conflicting results, and only recently, the genetic control of SI has been disclosed, revealing that olive possesses an unconventional homomorphic sporophytic diallelic system of SI, dissimilar from other described plants. This system, characterized by the presence of two SI groups, prevents self-fertilization and regulates inter-compatibility between cultivars, such that cultivars bearing the same incompatibility group are incompatible. Despite the presence of a functional SI, some varieties, in particular conditions, are able to set seeds following self-fertilization, a mechanism known as pseudo-self-compatibility (PSC), as widely reported in previous literature. Here, we summarize the results of previous works on SI in olive, particularly focusing on the occurrence of self-fertility, and offer a new perspective in view of the recent elucidation of the genetic architecture of the SI system in olive. Recent advances in research aimed at unraveling the molecular bases of SI and its breakdown in olive are also presented. The clarification of these mechanisms may have a huge impact on orchard management and will provide fundamental information for the future of olive breeding programs.
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Affiliation(s)
- F. Alagna
- Dipartimento Tecnologie Energetiche (DTE), Centro Ricerche Trisaia, ENEA Agenzia nazionale per le nuove tecnologie, l’energia e lo sviluppo economico sostenibile, Rotondella, Italy
| | - M. E. Caceres
- Dipartimento di Scienze Bio Agroalimentari (DiSBA), Istituto di Bioscienze e Biorisorse (IBBR), Consiglio Nazionale Delle Ricerche (CNR), Perugia, Italy
| | - S. Pandolfi
- Dipartimento di Scienze Bio Agroalimentari (DiSBA), Istituto di Bioscienze e Biorisorse (IBBR), Consiglio Nazionale Delle Ricerche (CNR), Perugia, Italy
| | - S. Collani
- Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, Umeå, Sweden
| | - S. Mousavi
- Dipartimento di Scienze Bio Agroalimentari (DiSBA), Istituto di Bioscienze e Biorisorse (IBBR), Consiglio Nazionale Delle Ricerche (CNR), Perugia, Italy
| | - R. Mariotti
- Dipartimento di Scienze Bio Agroalimentari (DiSBA), Istituto di Bioscienze e Biorisorse (IBBR), Consiglio Nazionale Delle Ricerche (CNR), Perugia, Italy
| | - N. G. M. Cultrera
- Dipartimento di Scienze Bio Agroalimentari (DiSBA), Istituto di Bioscienze e Biorisorse (IBBR), Consiglio Nazionale Delle Ricerche (CNR), Perugia, Italy
| | - L. Baldoni
- Dipartimento di Scienze Bio Agroalimentari (DiSBA), Istituto di Bioscienze e Biorisorse (IBBR), Consiglio Nazionale Delle Ricerche (CNR), Perugia, Italy
- *Correspondence: L. Baldoni,
| | - G. Barcaccia
- Laboratorio di Genomica, Dipartimento di Agronomia, Animali, Alimenti, Risorse naturali e Ambiente (DAFNAE), Università di Padova, Legnaro, Italy
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14
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Freyman WA, Höhna S. Stochastic Character Mapping of State-Dependent Diversification Reveals the Tempo of Evolutionary Decline in Self-Compatible Onagraceae Lineages. Syst Biol 2018; 68:505-519. [DOI: 10.1093/sysbio/syy078] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 11/05/2018] [Accepted: 11/13/2018] [Indexed: 11/13/2022] Open
Affiliation(s)
- William A Freyman
- Department of Integrative Biology, University of California, Berkeley, 3040 Valley Life Sciences Building #3140, CA 94720, USA
| | - Sebastian Höhna
- Division of Evolutionary Biology, Ludwig-Maximilians-Universität München, Geschwister-Scholl-Platz 1, 80539 Munich, Germany
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15
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Niu SC, Huang J, Xu Q, Li PX, Yang HJ, Zhang YQ, Zhang GQ, Chen LJ, Niu YX, Luo YB, Liu ZJ. Morphological Type Identification of Self-Incompatibility in Dendrobium and Its Phylogenetic Evolution Pattern. Int J Mol Sci 2018; 19:E2595. [PMID: 30200389 PMCID: PMC6163613 DOI: 10.3390/ijms19092595] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Revised: 08/29/2018] [Accepted: 08/29/2018] [Indexed: 11/20/2022] Open
Abstract
Self-incompatibility (SI) is a type of reproductive barrier within plant species and is one of the mechanisms for the formation and maintenance of the high diversity and adaptation of angiosperm species. Approximately 40% of flowering plants are SI species, while only 10% of orchid species are self-incompatible. Intriguingly, as one of the largest genera in Orchidaceae, 72% of Dendrobium species are self-incompatible, accounting for nearly half of the reported SI species in orchids, suggesting that SI contributes to the high diversity of orchid species. However, few studies investigating SI in Dendrobium have been published. This study aimed to address the following questions: (1) How many SI phenotypes are in Dendrobium, and what are they? (2) What is their distribution pattern in the Dendrobium phylogenetic tree? We investigated the flowering time, the capsule set rate, and the pollen tube growth from the representative species of Dendrobium after artificial pollination and analysed their distribution in the Asian Dendrobium clade phylogenetic tree. The number of SI phenotypes exceeded our expectations. The SI type of Dendrobium chrysanthum was the primary type in the Dendrobium SI species. We speculate that there are many different SI determinants in Dendrobium that have evolved recently and might be specific to Dendrobium or Orchidaceae. Overall, this work provides new insights and a comprehensive understanding of Dendrobium SI.
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Affiliation(s)
- Shan-Ce Niu
- Shenzhen Key Laboratory for Orchid Conservation and Utilization, The National Orchid Conservation Center of China and The Orchid Conservation and Research Center of Shenzhen, Shenzhen 518114, China.
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
- University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Jie Huang
- Shenzhen Key Laboratory for Orchid Conservation and Utilization, The National Orchid Conservation Center of China and The Orchid Conservation and Research Center of Shenzhen, Shenzhen 518114, China.
| | - Qing Xu
- Shenzhen Key Laboratory for Orchid Conservation and Utilization, The National Orchid Conservation Center of China and The Orchid Conservation and Research Center of Shenzhen, Shenzhen 518114, China.
| | - Pei-Xing Li
- Shenzhen Key Laboratory for Orchid Conservation and Utilization, The National Orchid Conservation Center of China and The Orchid Conservation and Research Center of Shenzhen, Shenzhen 518114, China.
| | - Hai-Jun Yang
- Shenzhen Key Laboratory for Orchid Conservation and Utilization, The National Orchid Conservation Center of China and The Orchid Conservation and Research Center of Shenzhen, Shenzhen 518114, China.
- College of Forestry and Landscape Architecture, Center of Experimental Teaching for Common Basic Courses, South China Agricultural University, Guangzhou 510640, China.
| | - Yong-Qiang Zhang
- Shenzhen Key Laboratory for Orchid Conservation and Utilization, The National Orchid Conservation Center of China and The Orchid Conservation and Research Center of Shenzhen, Shenzhen 518114, China.
| | - Guo-Qiang Zhang
- Shenzhen Key Laboratory for Orchid Conservation and Utilization, The National Orchid Conservation Center of China and The Orchid Conservation and Research Center of Shenzhen, Shenzhen 518114, China.
| | - Li-Jun Chen
- Shenzhen Key Laboratory for Orchid Conservation and Utilization, The National Orchid Conservation Center of China and The Orchid Conservation and Research Center of Shenzhen, Shenzhen 518114, China.
| | - Yun-Xia Niu
- University of Chinese Academy of Sciences, Beijing 100049, China.
- Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing 100093, China.
| | - Yi-Bo Luo
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
| | - Zhong-Jian Liu
- Shenzhen Key Laboratory for Orchid Conservation and Utilization, The National Orchid Conservation Center of China and The Orchid Conservation and Research Center of Shenzhen, Shenzhen 518114, China.
- College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510640, China.
- College of Landscape Architecture, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
- The Center for Biotechnology and BioMedicine, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China.
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16
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Vasconcelos TNC, Lucas EJ, Faria JEQ, Prenner G. Floral heterochrony promotes flexibility of reproductive strategies in the morphologically homogeneous genus Eugenia (Myrtaceae). ANNALS OF BOTANY 2018; 121:161-174. [PMID: 29267929 PMCID: PMC5786242 DOI: 10.1093/aob/mcx142] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 10/28/2017] [Indexed: 05/28/2023]
Abstract
BACKGROUND AND AIMS Comparative floral ontogeny represents a valuable tool to understand angiosperm evolution. Such an approach may elucidate subtle changes in development that discretely modify floral architecture and underlie reproductive lability in groups with superficial homogeneous morphology. This study presents a comparative survey of floral development in Eugenia (Myrtaceae), one of the largest genera of angiosperms, and shows how previously undocumented ontogenetic trends help to explain the evolution of its megadiversity in contrast to its apparent flower uniformity. METHODS Using scanning electron microscopy, selected steps of the floral ontogeny of a model species (Eugenia punicifolia) are described and compared with 20 further species representing all ten major clades in the Eugenia phylogenetic tree. Additional floral trait data are contrasted for correlation analysis and character reconstructions performed against the Myrtaceae phylogenetic tree. KEY RESULTS Eugenia flowers show similar organ arrangement patterns: radially symmetrical, (most commonly) tetramerous flowers with variable numbers of stamens and ovules. Despite a similar general organization, heterochrony is evident from size differences between tissues and structures at similar developmental stages. These differences underlie variable levels of investment in protection, subtle modifications to symmetry, herkogamic effects and independent androecium and gynoecium variation, producing a wide spectrum of floral display and contributing to fluctuations in fitness. During Eugenia's bud development, the hypanthium (as defined here) is completely covered by stamen primordia, unusual in other Myrtaceae. This is the likely plesiomorphic state for Myrteae and may have represented a key evolutionary novelty in the tribe. CONCLUSIONS Floral evolution in Eugenia depends on heterochronic patterns rather than changes in complexity to promote flexibility in floral strategies. The successful early establishment of Myrteae, previously mainly linked to the key innovation of fleshy fruit, may also have benefitted from changes in flower structure.
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Affiliation(s)
- Thais N C Vasconcelos
- Comparative Plant and Fungal Biology Department, Jodrell Laboratory, Royal Botanic Gardens Kew, Richmond, UK
| | - Eve J Lucas
- Comparative Plant and Fungal Biology Department, Jodrell Laboratory, Royal Botanic Gardens Kew, Richmond, UK
| | - Jair E Q Faria
- Departamento de Engenharia Florestal, Universidade Federal do Vale do Jequitinhonha e Mucuri, Diamantina, MG, Brazil
| | - Gerhard Prenner
- Comparative Plant and Fungal Biology Department, Jodrell Laboratory, Royal Botanic Gardens Kew, Richmond, UK
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17
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Castillo DM, Gibson AK, Moyle LC. Assortative mating and self-fertilization differ in their contributions to reinforcement, cascade speciation, and diversification. Curr Zool 2016; 62:169-181. [PMID: 29491904 PMCID: PMC5804227 DOI: 10.1093/cz/zow004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 01/07/2016] [Indexed: 11/14/2022] Open
Abstract
Cascade speciation and reinforcement can evolve rapidly when traits are pleiotropic and act as both signal/cue in nonrandom mating. Here, we examine the contribution of two key traits-assortative mating and self-fertilization-to reinforcement and (by extension) cascade speciation. First, using a population genetic model of reinforcement we find that both assortative mating and self-fertilization can make independent contributions to increased reproductive isolation, consistent with reinforcement. Self-fertilization primarily evolves due to its 2-fold transmission advantage when inbreeding depression (d) is lower (d < 0.45) but evolves as a function of the cost of hybridization under higher inbreeding depression (0.45 < d < 0.48). When both traits can evolve simultaneously, increased self-fertilization often prohibits the evolution of assortative mating. We infer that, under specific conditions, mating system transitions are more likely to lead to increased reproductive isolation and initiate cascade speciation, than assortative mating. Based on the results of our simulations, we hypothesized that transitions to self-fertilization could contribute to clade-wide diversification if reinforcement or cascade speciation is common. We tested this hypothesis with comparative data from two different groups. Consistent with our hypothesis, there was a trend towards uniparental reproduction being associated with increased diversification rate in the Nematode phylum. For the plant genus Mimulus, however, self-fertilization was associated with reduced diversification. Reinforcement driving speciation via transitions to self-fertilization might be short lived or unsustainable across macroevolutionary scales in some systems (some plants), but not others (such as nematodes), potentially due to differences in susceptibility to inbreeding depression and/or the ability to transition between reproductive modes.
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Affiliation(s)
- Dean M. Castillo
- Department of Biology, 1001 East Third Street, Indiana University, Bloomington, IN 47405, USA
| | - Amanda K. Gibson
- Department of Biology, 1001 East Third Street, Indiana University, Bloomington, IN 47405, USA
| | - Leonie C. Moyle
- Department of Biology, 1001 East Third Street, Indiana University, Bloomington, IN 47405, USA
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18
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Lora J, Hormaza JI, Herrero M. The Diversity of the Pollen Tube Pathway in Plants: Toward an Increasing Control by the Sporophyte. FRONTIERS IN PLANT SCIENCE 2016; 7:107. [PMID: 26904071 PMCID: PMC4746263 DOI: 10.3389/fpls.2016.00107] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 01/20/2016] [Indexed: 05/06/2023]
Abstract
Plants, unlike animals, alternate multicellular diploid, and haploid generations in their life cycle. While this is widespread all along the plant kingdom, the size and autonomy of the diploid sporophyte and the haploid gametophyte generations vary along evolution. Vascular plants show an evolutionary trend toward a reduction of the gametophyte, reflected both in size and lifespan, together with an increasing dependence from the sporophyte. This has resulted in an overlooking of the importance of the gametophytic phase in the evolution of higher plants. This reliance on the sporophyte is most notorious along the pollen tube journey, where the male gametophytes have to travel a long way inside the sporophyte to reach the female gametophyte. Along evolution, there is a change in the scenery of the pollen tube pathway that favors pollen competition and selection. This trend, toward apparently making complicated what could be simple, appears to be related to an increasing control of the sporophyte over the gametophyte with implications for understanding plant evolution.
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Affiliation(s)
- Jorge Lora
- Department of Subtropical Fruit Crops, Instituto de Hortofruticultura Subtropical y Mediterránea La Mayora – University of Málaga – Consejo Superior de Investigaciones CientíficasMálaga, Spain
| | - José I. Hormaza
- Department of Subtropical Fruit Crops, Instituto de Hortofruticultura Subtropical y Mediterránea La Mayora – University of Málaga – Consejo Superior de Investigaciones CientíficasMálaga, Spain
| | - María Herrero
- Department of Pomology, Estación Experimental Aula Dei, Consejo Superior de Investigaciones CientíficasZaragoza, Spain
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19
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Thomas CD. Rapid acceleration of plant speciation during the Anthropocene. Trends Ecol Evol 2015; 30:448-55. [DOI: 10.1016/j.tree.2015.05.009] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 05/27/2015] [Accepted: 05/28/2015] [Indexed: 11/26/2022]
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20
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Donoghue MJ, Sanderson MJ. Confluence, synnovation, and depauperons in plant diversification. THE NEW PHYTOLOGIST 2015; 207:260-274. [PMID: 25778694 DOI: 10.1111/nph.13367] [Citation(s) in RCA: 117] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 01/14/2015] [Indexed: 05/02/2023]
Abstract
We review the empirical phylogenetic literature on plant diversification, highlighting challenges in separating the effects of speciation and extinction, in specifying diversification mechanisms, and in making convincing arguments. In recent discussions of context dependence, key opportunities and landscapes, and indirect effects and lag times, we see a distinct shift away from single-point/single-cause 'key innovation' hypotheses toward more nuanced explanations involving multiple interacting causal agents assembled step-wise through a tree. To help crystalize this emerging perspective we introduce the term 'synnovation' (a hybrid of 'synergy' and 'innovation') for an interacting combination of traits with a particular consequence ('key synnovation' in the case of increased diversification rate), and the term 'confluence' for the sequential coming together of a set of traits (innovations and synnovations), environmental changes, and geographic movements along the branches of a phylogenetic tree. We illustrate these concepts using the radiation of Bromeliaceae. We also highlight the generality of these ideas by considering how rate heterogeneity associated with a confluence relates to the existence of particularly species-poor lineages, or 'depauperons.' Many challenges are posed by this re-purposed research framework, including difficulties associated with partial taxon sampling, uncertainty in divergence time estimation, and extinction.
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Affiliation(s)
- Michael J Donoghue
- Department of Ecology and Evolutionary Biology, Yale University, PO Box 208106, New Haven, CT, 06520, USA
| | - Michael J Sanderson
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, 85721, USA
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21
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De Vos JM, Joppa LN, Gittleman JL, Stephens PR, Pimm SL. Estimating the normal background rate of species extinction. CONSERVATION BIOLOGY : THE JOURNAL OF THE SOCIETY FOR CONSERVATION BIOLOGY 2015; 29:452-62. [PMID: 25159086 DOI: 10.1111/cobi.12380] [Citation(s) in RCA: 154] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Accepted: 06/22/2014] [Indexed: 05/25/2023]
Abstract
A key measure of humanity's global impact is by how much it has increased species extinction rates. Familiar statements are that these are 100-1000 times pre-human or background extinction levels. Estimating recent rates is straightforward, but establishing a background rate for comparison is not. Previous researchers chose an approximate benchmark of 1 extinction per million species per year (E/MSY). We explored disparate lines of evidence that suggest a substantially lower estimate. Fossil data yield direct estimates of extinction rates, but they are temporally coarse, mostly limited to marine hard-bodied taxa, and generally involve genera not species. Based on these data, typical background loss is 0.01 genera per million genera per year. Molecular phylogenies are available for more taxa and ecosystems, but it is debated whether they can be used to estimate separately speciation and extinction rates. We selected data to address known concerns and used them to determine median extinction estimates from statistical distributions of probable values for terrestrial plants and animals. We then created simulations to explore effects of violating model assumptions. Finally, we compiled estimates of diversification-the difference between speciation and extinction rates for different taxa. Median estimates of extinction rates ranged from 0.023 to 0.135 E/MSY. Simulation results suggested over- and under-estimation of extinction from individual phylogenies partially canceled each other out when large sets of phylogenies were analyzed. There was no evidence for recent and widespread pre-human overall declines in diversity. This implies that average extinction rates are less than average diversification rates. Median diversification rates were 0.05-0.2 new species per million species per year. On the basis of these results, we concluded that typical rates of background extinction may be closer to 0.1 E/MSY. Thus, current extinction rates are 1,000 times higher than natural background rates of extinction and future rates are likely to be 10,000 times higher.
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Affiliation(s)
- Jurriaan M De Vos
- Institute of Systematic Botany, University of Zurich, Zollikerstrasse 107, 8008, Zürich, Switzerland; Department of Ecology and Evolutionary Biology, Brown University, Box G-W, Providence, RI, 02912, U.S.A
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22
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Pimm SL, Jenkins CN, Abell R, Brooks TM, Gittleman JL, Joppa LN, Raven PH, Roberts CM, Sexton JO. The biodiversity of species and their rates of extinction, distribution, and protection. Science 2014; 344:1246752. [PMID: 24876501 DOI: 10.1126/science.1246752] [Citation(s) in RCA: 1108] [Impact Index Per Article: 110.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Recent studies clarify where the most vulnerable species live, where and how humanity changes the planet, and how this drives extinctions. We assess key statistics about species, their distribution, and their status. Most are undescribed. Those we know best have large geographical ranges and are often common within them. Most known species have small ranges. The numbers of small-ranged species are increasing quickly, even in well-known taxa. They are geographically concentrated and are disproportionately likely to be threatened or already extinct. Current rates of extinction are about 1000 times the likely background rate of extinction. Future rates depend on many factors and are poised to increase. Although there has been rapid progress in developing protected areas, such efforts are not ecologically representative, nor do they optimally protect biodiversity.
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Affiliation(s)
- S L Pimm
- Nicholas School of the Environment, Duke University, Box 90328, Durham, NC 27708, USA.
| | - C N Jenkins
- Instituto de Pesquisas Ecológicas, Rodovia Dom Pedro I, km 47, Caixa Postal 47, Nazaré Paulista SP, 12960-000, Brazil
| | - R Abell
- Post Office Box 402 Haverford, PA 19041, USA
| | - T M Brooks
- International Union for Conservation of Nature, IUCN, 28 Rue Mauverney, CH-1196 Gland, Switzerland
| | - J L Gittleman
- Odum School of Ecology, University of Georgia, Athens, GA 30602, USA
| | - L N Joppa
- Microsoft Research, 21 Station Road, Cambridge, CB1 2FB, UK
| | - P H Raven
- Missouri Botanical Garden, Post Office Box 299, St. Louis, MO 63166-0299, USA
| | - C M Roberts
- Environment Department, University of York, York, YO10 5DD, UK
| | - J O Sexton
- Global Land Cover Facility, Department of Geographical Sciences, University of Maryland, College Park, MD, 20742, USA
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23
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Hipsley CA, Müller J. Beyond fossil calibrations: realities of molecular clock practices in evolutionary biology. Front Genet 2014; 5:138. [PMID: 24904638 PMCID: PMC4033271 DOI: 10.3389/fgene.2014.00138] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Accepted: 04/27/2014] [Indexed: 01/22/2023] Open
Abstract
Molecular-based divergence dating methods, or molecular clocks, are the primary neontological tool for estimating the temporal origins of clades. While the appropriate use of vertebrate fossils as external clock calibrations has stimulated heated discussions in the paleontological community, less attention has been given to the quality and implementation of other calibration types. In lieu of appropriate fossils, many studies rely on alternative sources of age constraints based on geological events, substitution rates and heterochronous sampling, as well as dates secondarily derived from previous analyses. To illustrate the breadth and frequency of calibration types currently employed, we conducted a literature survey of over 600 articles published from 2007 to 2013. Over half of all analyses implemented one or more fossil dates as constraints, followed by geological events and secondary calibrations (15% each). Vertebrate taxa were subjects in nearly half of all studies, while invertebrates and plants together accounted for 43%, followed by viruses, protists and fungi (3% each). Current patterns in calibration practices were disproportionate to the number of discussions on their proper use, particularly regarding plants and secondarily derived dates, which are both relatively neglected in methodological evaluations. Based on our survey, we provide a comprehensive overview of the latest approaches in clock calibration, and outline strengths and weaknesses associated with each. This critique should serve as a call to action for researchers across multiple communities, particularly those working on clades for which fossil records are poor, to develop their own guidelines regarding selection and implementation of alternative calibration types. This issue is particularly relevant now, as time-calibrated phylogenies are used for more than dating evolutionary origins, but often serve as the backbone of investigations into biogeography, diversity dynamics and rates of phenotypic evolution.
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Affiliation(s)
- Christy A. Hipsley
- Museum für Naturkunde, Leibniz-Institut für Evolutions- und BiodiversitätsforschungBerlin, Germany
| | - Johannes Müller
- Museum für Naturkunde, Leibniz-Institut für Evolutions- und BiodiversitätsforschungBerlin, Germany
- Berlin-Brandenburg Institute of Avanced Biodiversity ResearchBerlin, Germany
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24
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de Vos JM, Hughes CE, Schneeweiss GM, Moore BR, Conti E. Heterostyly accelerates diversification via reduced extinction in primroses. Proc Biol Sci 2014; 281:20140075. [PMID: 24759859 DOI: 10.1098/rspb.2014.0075] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The exceptional species diversity of flowering plants, exceeding that of their sister group more than 250-fold, is especially evident in floral innovations, interactions with pollinators and sexual systems. Multiple theories, emphasizing flower-pollinator interactions, genetic effects of mating systems or high evolvability, predict that floral evolution profoundly affects angiosperm diversification. However, consequences for speciation and extinction dynamics remain poorly understood. Here, we investigate trajectories of species diversification focusing on heterostyly, a remarkable floral syndrome where outcrossing is enforced via cross-compatible floral morphs differing in placement of their respective sexual organs. Heterostyly evolved at least 20 times independently in angiosperms. Using Darwin's model for heterostyly, the primrose family, we show that heterostyly accelerates species diversification via decreasing extinction rates rather than increasing speciation rates, probably owing to avoidance of the negative genetic effects of selfing. However, impact of heterostyly appears to differ over short and long evolutionary time-scales: the accelerating effect of heterostyly on lineage diversification is manifest only over long evolutionary time-scales, whereas recent losses of heterostyly may prompt ephemeral bursts of speciation. Our results suggest that temporal or clade-specific conditions may ultimately determine the net effects of specific traits on patterns of species diversification.
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Affiliation(s)
- Jurriaan M de Vos
- Institute of Systematic Botany, University of Zürich, , Zollikerstrasse 107, 8008 Zürich, Switzerland, Department of Ecology and Evolutionary Biology, Brown University, , 80 Waterman Street, Box G-W, Providence, RI 02912, USA, Department of Botany and Biodiversity Research, University of Vienna, , Rennweg 14, Vienna 1030, Austria, Department of Evolution and Ecology, University of California, , Davis, 1 Shields Avenue, CA 95616, USA
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25
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Castric V, Billiard S, Vekemans X. Trait transitions in explicit ecological and genomic contexts: plant mating systems as case studies. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 781:7-36. [PMID: 24277293 DOI: 10.1007/978-94-007-7347-9_2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Plants are astonishingly diverse in how they reproduce sexually, and the study of plant mating systems provides some of the most compelling cases of parallel and independent evolutionary transitions. In this chapter, we review how the massive amount of genomic data being produced is allowing long-standing predictions from ecological and evolutionary theory to be put to test. After a review of theoretical predictions about the importance of considering the genomic architecture of the mating system, we focus on a set of recent discoveries on how the mating system is controlled in a variety of model and non-model species. In parallel, genomic approaches have revealed the complex interaction between the evolution of genes controlling mating systems and genome evolution, both genome-wide and in the mating system control region. In several cases, major transitions in the mating system can be clearly associated with important ecological changes, hence illuminating an important interplay between ecological and genomic approaches. We also list a number of major unsolved questions that remain for the field, and highlight foreseeable conceptual developments that are likely to play a major role in our understanding of how plant mating systems evolve in Nature.
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Affiliation(s)
- Vincent Castric
- Laboratoire de Génétique et Evolution des Populations Végétales (GEPV), UMR 8198; CNRS, Université Lille 1, Sciences et Technologies, Cité Scientifique, Villeneuve d'Ascq, France,
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Martínez-Peralta C, Márquez-Guzmán J, Mandujano MC. How common is self-incompatibility across species of the herkogamous genus Ariocarpus? AMERICAN JOURNAL OF BOTANY 2014; 101:530-538. [PMID: 24607514 DOI: 10.3732/ajb.1400022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
PREMISE OF THE STUDY Self-incompatibility (SI), the most effective mechanism to prevent selfing, may limit the number of compatible mates in populations. The seven species of Ariocarpus are endangered and predominantly outcrossers but fruit set may reach 1-20% after selfing. We aimed to determine whether SI is the underlying mechanism influencing mating in Ariocarpus species. METHODS We characterized the presence/absence of SI using pollination treatments (self-pollination, cross-pollination, natural pollination) in one population per species. We assessed SI using epifluorescence and generalized linear models (GLMs) to compare the presence of pollen tubes in the stigma, stylar transmitting tissue, and ovary among self- and cross-pollinated pistils 48 h after pollination. Following the same treatments, production of fruit set was noted and related to pollen tube growth. KEY RESULTS Pollen tubes were found more frequently in the ovaries of natural and cross-pollinated flowers than in ovaries of self-pollinated. Stylar rejection of self-pollen indicated gametophytic SI, although pollen tubes reached the ovaries in six species (4-33% of pistils). Fruit set was lower after hand-pollinations than expected from pollen tube observations. CONCLUSIONS The low percentages of self-compatibility in all species in pollen tube growth and pollination experiments indicated that no species had complete self-sterility, suggesting the presence of partial SI. Reduced fruit set relative to pollen tube production could result from a threshold of insufficient pollination, early-acting inbreeding depression, or resource limitation. The origin of partial SI in Ariocarpus could respond to pressures such as pollen limitation and population size.
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Affiliation(s)
- Concepción Martínez-Peralta
- Departamento de Ecología de la Biodiversidad, Laboratorio de Genética y Ecología, Instituto de Ecología, Universidad Nacional Autónoma de México, Apartado Postal 70-275, Ciudad Universitaria, México, D. F., México
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de Vos JM, Wüest RO, Conti E. Small and ugly? Phylogenetic analyses of the "selfing syndrome" reveal complex evolutionary fates of monomorphic primrose flowers. Evolution 2014; 68:1042-57. [PMID: 24325205 DOI: 10.1111/evo.12331] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 11/18/2013] [Indexed: 01/10/2023]
Abstract
One of the most common trends in plant evolution, loss of self-incompatibility and ensuing increases in selfing, is generally assumed to be associated with a suite of phenotypic changes, notably a reduction of floral size, termed the selfing syndrome. We investigate whether floral morphological traits indeed decrease in a deterministic fashion after losses of self-incompatibility, as traditionally expected, using a phylogeny of 124 primrose species containing nine independent transitions from heterostyly (heteromorphic incompatibility) to homostyly (monomorphic self-compatibility), a classic system for evolution of selfing. We find similar overall variability of homostylous and heterostylous species, except for diminished herkogamy in homostyles. Bayesian mixed models demonstrate differences between homostylous and heterostylous species in all traits, but net effects across species are small (except herkogamy) and directionality differs among traits. Strongly drift-like evolutionary trajectories of corolla tube length and corolla diameter inferred by Ornstein-Uhlenbeck models contrast with expected deterministic trajectories toward small floral size. Lineage-specific population genetic effects associated with evolution of selfing may explain that reductions of floral size represent one of several possible outcomes of floral evolution after loss of heterostyly in primroses. Contrary to the traditional paradigm, selfing syndromes may, but do not necessarily evolve in response to increased selfing.
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Affiliation(s)
- Jurriaan M de Vos
- Institute of Systematic Botany, University of Zürich, Zollikerstrasse 107, 8008 Zürich, Switzerland; Department of Ecology and Evolutionary Biology, Brown University, 80 Waterman St., Box G-W, Providence, Rhode Island, 02912.
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Blanco-Pastor JL, Vargas P. Autecological traits determined two evolutionary strategies in Mediterranean plants during the Quaternary: low differentiation and range expansion versus geographical speciation in Linaria. Mol Ecol 2013; 22:5651-68. [PMID: 24134639 DOI: 10.1111/mec.12518] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 08/24/2013] [Indexed: 01/18/2023]
Abstract
The evolutionary patterns of the Mediterranean flora during the Quaternary have been relatively well documented based on phylogenetic and biogeographic analyses, but few studies have addressed the evolutionary traits that determined diversification and range expansion success during this period. We analysed previously published and newly generated sequences of three plastid noncoding regions (rpl32-trnL(UAG) , trnS-trnG and trnL-trnF), the nuclear ribosomal internal transcribed spacer (ITS) and a low-copy nuclear gene intron (AGT1) of Linaria sect. Supinae, a group of angiosperms that diversified in the Quaternary. The origin and recent colonization dynamics of closely related lineages were inferred by biogeographic reconstruction and phylogeographic analyses, while breeding system experiments coupled with ecological and morphological data were used to test association with range expansion and diversification. A combination of traits, including selfing, short lifespan and the ability to tolerate a wide variety of substrates, were key factors underlying range expansion after long-distance dispersal throughout the Mediterranean basin. By contrast, self-incompatibility may have promoted higher diversification rates in narrow ranges of the Iberian Peninsula. We argue that a few traits contributed to the adoption of two contrasting strategies that may have been predominant in the evolution of Mediterranean angiosperms.
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Affiliation(s)
- J L Blanco-Pastor
- Real Jardín Botánico de Madrid (RJB-CSIC), Plaza de Murillo, 2, 28014, Madrid, Spain
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Barrett SCH. The evolution of plant reproductive systems: how often are transitions irreversible? Proc Biol Sci 2013; 280:20130913. [PMID: 23825207 PMCID: PMC3712442 DOI: 10.1098/rspb.2013.0913] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 06/03/2013] [Indexed: 11/12/2022] Open
Abstract
Flowering plants are characterized by striking variation in reproductive systems, and the evolutionary lability of their sexual traits is often considered a major driver of lineage diversification. But, evolutionary transitions in reproductive form and function are never entirely unconstrained and many changes exhibit strong directionality. Here, I consider why this occurs by examining transitions in pollination, mating and sexual systems, some of which have been considered irreversible. Among pollination systems, shifts from bee to hummingbird pollination are rarely reversible, whereas transitions from animal to wind pollination are occasionally reversed. Specialized pollination systems can become destabilized through a loss of pollinator service resulting in a return to generalized pollination, or more commonly a reliance on self-pollination. Homomorphic and heteromorphic self-incompatibility systems have multiple origins but breakdown to self-compatibility occurs much more frequently with little evidence for subsequent gains, at least over short time-spans. Similarly, numerous examples of the shift from outcrossing to predominant self-fertilization are known, but cases of reversal are very limited supporting the view that autogamy usually represents an evolutionary dead-end. The evolution of dioecy from hermaphroditism has also been considered irreversible, although recent evidence indicates that the occurrence of sex inconstancy and hybridization can lead to the origin of derived sexual systems from dioecy. The directionality of many transitions clearly refutes the notion of unconstrained reproductive flexibility, but novel adaptive solutions generally do not retrace earlier patterns of trait evolution.
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Affiliation(s)
- Spencer C H Barrett
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada.
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Wright SI, Kalisz S, Slotte T. Evolutionary consequences of self-fertilization in plants. Proc Biol Sci 2013; 280:20130133. [PMID: 23595268 PMCID: PMC3652455 DOI: 10.1098/rspb.2013.0133] [Citation(s) in RCA: 277] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 03/22/2013] [Indexed: 01/17/2023] Open
Abstract
The transition from outcrossing to self-fertilization is one of the most common evolutionary changes in plants, yet only about 10-15% of flowering plants are predominantly selfing. To explain this phenomenon, Stebbins proposed that selfing may be an 'evolutionary dead end'. According to this hypothesis, transitions from outcrossing to selfing are irreversible, and selfing lineages suffer from an increased risk of extinction owing to a reduced potential for adaptation. Thus, although selfing can be advantageous in the short term, selfing lineages may be mostly short-lived owing to higher extinction rates. Here, we review recent results relevant to the 'dead-end hypothesis' of selfing and the maintenance of outcrossing over longer evolutionary time periods. In particular, we highlight recent results regarding diversification rates in self-incompatible and self-compatible taxa, and review evidence regarding the accumulation of deleterious mutations in selfing lineages. We conclude that while some aspects of the hypothesis of selfing as a dead end are supported by theory and empirical results, the evolutionary and ecological mechanisms remain unclear. We highlight the need for more studies on the effects of quantitative changes in outcrossing rates and on the potential for adaptation, particularly in selfing plants. In addition, there is growing evidence that transitions to selfing may themselves be drivers of speciation, and future studies of diversification and speciation should investigate this further.
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Affiliation(s)
- Stephen I. Wright
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
| | - Susan Kalisz
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Tanja Slotte
- Department of Evolutionary Biology, Evolutionary Biology Centre (EBC), Uppsala University, Uppsala, Sweden
- Science for Life Laboratory, Uppsala University, Uppsala, Sweden
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Weber JJ, Weller SG, Sakai AK, Tsyusko OV, Glenn TC, Domínguez CA, Molina-Freaner FE, Fornoni J, Tran M, Nguyen N, Nguyen K, Tran LK, Joice G, Harding E. THE ROLE OF INBREEDING DEPRESSION AND MATING SYSTEM IN THE EVOLUTION OF HETEROSTYLY. Evolution 2013; 67:2309-22. [DOI: 10.1111/evo.12123] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Accepted: 03/20/2013] [Indexed: 11/30/2022]
Affiliation(s)
- Jennifer J. Weber
- Department of Ecology and Evolutionary Biology; University of California; Irvine California 92697
| | - Stephen G. Weller
- Department of Ecology and Evolutionary Biology; University of California; Irvine California 92697
| | - Ann K. Sakai
- Department of Ecology and Evolutionary Biology; University of California; Irvine California 92697
| | - Olga V. Tsyusko
- Department of Plant and Soil Sciences; University of Kentucky; Lexington Kentucky 40546
| | - Travis C. Glenn
- Environmental Health Sciences; University of Georgia; Athens Georgia 30602
| | - César A. Domínguez
- Departamento de Ecología Evolutiva, Instituto de Ecología; Universidad Nacional Autónoma de México; Apartado Postal 70-275, México Distrito Federal 04510 México
| | - Francisco E. Molina-Freaner
- Departamento de Ecología de la Biodiversidad, Estación Regional del Noroeste, Instituto de Ecología; Universidad Nacional Autónoma de México; Apartado Postal 1354 Hermosillo 83000 Sonora México
| | - Juan Fornoni
- Departamento de Ecología Evolutiva, Instituto de Ecología; Universidad Nacional Autónoma de México; Apartado Postal 70-275, México Distrito Federal 04510 México
| | - Mike Tran
- Department of Ecology and Evolutionary Biology; University of California; Irvine California 92697
| | - Nhu Nguyen
- Department of Ecology and Evolutionary Biology; University of California; Irvine California 92697
| | - Karen Nguyen
- Department of Ecology and Evolutionary Biology; University of California; Irvine California 92697
| | - Lien-Khuong Tran
- Department of Ecology and Evolutionary Biology; University of California; Irvine California 92697
| | - Greg Joice
- Department of Plant and Soil Sciences; University of Kentucky; Lexington Kentucky 40546
| | - Ellen Harding
- Department of Plant and Soil Sciences; University of Kentucky; Lexington Kentucky 40546
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Hazzouri KM, Escobar JS, Ness RW, Killian Newman L, Randle AM, Kalisz S, Wright SI. Comparative population genomics in Collinsia sister species reveals evidence for reduced effective population size, relaxed selection, and evolution of biased gene conversion with an ongoing mating system shift. Evolution 2013; 67:1263-78. [PMID: 23617907 DOI: 10.1111/evo.12027] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 11/15/2012] [Indexed: 10/27/2022]
Abstract
Selfing species experience reduced effective recombination rates and effective population size, which can lead to reductions in polymorphism and the efficacy of natural selection. Here, we use illumina transcriptome sequencing and population resequencing to test for changes in polymorphism, base composition, and selection in the selfing angiosperm Collinsia rattanii (Plantaginaceae) compared with its more outcrossing sister species Collinsia linearis. Coalescent analysis indicates intermediate species divergence (500,000-1 million years) with no ongoing gene flow, but also evidence that the C. rattanii clade remains polymorphic for floral morphology and mating system, suggesting either an ongoing shift to selfing or a potential reversal from selfing to outcrossing. We identify a significant reduction in polymorphism in C. rattanii, particularly within populations. Analysis of polymorphisms suggests an elevated ratio of unique nonsynonymous to synonymous polymorphism in C. rattanii, consistent with relaxed selection in selfing lineages. We additionally find higher linkage disequilibrium and differentiation, lower GC content at variable sites, and reduced expression of genes important in pollen production and pollinator attraction in C. rattanii compared with C. linearis. Together, our results highlight the potential for rapid shifts in the efficacy of selection, gene expression and base composition associated with ongoing evolution of selfing.
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Affiliation(s)
- Khaled M Hazzouri
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
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