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Tim C G Rich - One of the best experts on this subject based on the ideXlab platform.
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Versatility of reproductive modes and ploidy level interactions in Sorbus s.l. (Malinae, Rosaceae)
Botanical Journal of the Linnean Society, 2019Co-Authors: Martin Lepší, Petr Koutecký, Jana Nosková, Petr Lepší, Tomáš Urfus, Tim C G RichAbstract:Abstract This study focuses on the frequency of reproductive modes and the role of reproductive mode variation in diversification of the genus Sorbus s.l. and evolutionary success of individual taxa. Our sampling covers all four ploidies known in Sorbus and includes stabilized taxa and recently formed biotypes. We infer reproductive modes of 3660 seeds using the flow cytometric seed screen method; we also calculated ploidy of contributing pollen. Sorbus shows high variability in reproduction pathways (sexuality, apomixis, formation of BIII hybrids, haploid parthenogenesis). Diploids are sexual, whereas polyploids show predominantly pseudogamous apomixis. In half of the polyploids studied, several reproductive modes were present and even intra-individual variation was detected. Diploids, tetraploids and pentaploids are pollinated by conspecific pollen, whereas triploids are largely, but not fully, dependent on the pollen of other species. In pseudogamous seeds, fertilization of the central cell by both sperms is a dominant pathway of endosperm origin. Flow cytometry of pollen did not detect unreduced pollen at any ploidy. The principal mechanisms of diversification in Sorbus are residual sexuality in apomicts, production of triploid taxa from diploid–tetraploid crosses and production of BIII hybrids. Evolutionary success of Sorbus taxa is largely dependent on the breeding system and is determined by self-(in)compatibility and the interplay between stabilizing apomixis and variation-generating sexuality.
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British Sorbus (Rosaceae): six new species, two hybrids and a new subgenus
New Journal of Botany, 2014Co-Authors: Tim C G Rich, L. Houston, D. Green, M. Lepší, S. Ludwig, Jaume PellicerAbstract:Six new Sorbus species are described in Sorbus subgenus Aria; S. evansii T.C.G. Rich, sp. nov., S. greenii T.C.G. Rich, sp. nov., S. herefordensis D. Green, sp. nov., S. richii L. Houston, sp. nov., S. sellii T.C.G. Rich, sp. nov., and S. spectans L. Houston, sp. nov. The occurrence of two new subgeneric hybrids is noted – S. aucuparia × minima (subgenus Soraria) and a distinct member of subgenus Tormaria of unknown parentage – which do not merit binomials. Subgenus Triparens M. Lepsi & T.C.G. Rich is described to accommodate taxa that originated as crosses between Sorbus subgenus Aria, subgenus Sorbus and subgenus Torminaria.
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Sorbus liljeforsii a name for thes aucuparia intermediahybrid rosaceae
Nordic Journal of Botany, 2007Co-Authors: Tim C G RichAbstract:The uncommon spontaneous hybrid between Sorbus aucuparia L. and S. intermedia (Ehrh.) Pers (Rosaceae) is described and named as Sorbus×liljeforsii.
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Sorbus×liljeforsii, a name for theS. aucuparia×intermediahybrid (Rosaceae)
Nordic Journal of Botany, 2007Co-Authors: Tim C G RichAbstract:The uncommon spontaneous hybrid between Sorbus aucuparia L. and S. intermedia (Ehrh.) Pers (Rosaceae) is described and named as Sorbus×liljeforsii.
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Parentage of endemic Sorbus L. (Rosaceae) species in the British Isles: evidence from plastid DNA
Botanical Journal of the Linnean Society, 2007Co-Authors: Michael Chester, Robyn S. Cowan, Michael F. Fay, Tim C G RichAbstract:The parentage of polyploid Sorbus species in the British Isles was investigated using plastid DNA microsatellites. Four hundred and fifty-three samples from 30 taxa were screened using six microsatellite fragments, which gave 28 haplotypes. The haplotypes formed groups clearly related to the ancestral diploids Sorbus aria, Sorbus aucuparia, and Sorbus torminalis. Species in the Sorbus aria group all had Aria haplotypes (with the exception of one English S. aria), species in the Sorbus anglica group had an Aucuparia haplotype, and species in the Sorbus latifolia group had a Torminalis haplotype. Sorbus intermedia had an Aucuparia haplotype. This indicated that the hybridization events that led to the formation of species in the S. anglica and S. latifolia groups usually did so with S. aria s.l. as the pollen-donating (paternal) parent. The polyploids S. anglica, Sorbus bristoliensis, Sorbus croceocarpa, Sorbus decipiens, Sorbus devoniensis, Sorbus hibernica, Sorbus lancastriensis, Sorbus leptophylla, Sorbus leyana, Sorbus minima, Sorbus rupicola, Sorbus subcuneata, Sorbus vexans, Sorbus whiteana, Sorbus wilmottiana, and three unnamed taxa may each be derived from a single maternal lineage. The polyploids Sorbus eminens, Sorbus porrigentiformis, and S. latifolia have multiple maternal lineages. The two primary diploid hybrids S. × thuringiaca and S. × vagensis have arisen many times independently. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 154, 291–304.
U K Vogt - One of the best experts on this subject based on the ideXlab platform.
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hydraulic vulnerability vessel refilling and seasonal courses of stem water potential of Sorbus aucuparia l and sambucus nigra l
Journal of Experimental Botany, 2001Co-Authors: U K VogtAbstract:Differences in the seasonal variation in stem water potential between the two shrub species Sorbus aucuparia and Sambucus nigra were related with their vulnerability to xylem cavitation. It was also demonstrated indirectly that the two species differ in the extent to which they reverse cavitation. Seasonal variation in stem water potential was investigated during three growing seasons with in situ stem psychrometers. Sorbus experienced wide water potential variations and reached a minimum of -4.2 MPa during drought. Under the same microclimatic conditions, Sambucus experienced consistent stem water potentials with a minimum of -1.7 MPa. The relationship between percentage loss in hydraulic conductivity (PLC) and water potential (hydraulic vulnerability curve) of the two species differed in shape: a flat curve with nearly total loss of conductivity at -6 MPa was found for Sorbus: Sambucus showed a steep vulnerability curve with 90% loss conductivity at -2.2 MPa. Thus, Sambucus is extremely vulnerable to cavitation, but Sorbus is an almost invulnerable species. This different cavitation resistance adjusted the ranges of field stem water potential that the species experienced. Finally, seasonal courses of naturally occurring (native) embolism were compared with calculated PLC courses. This comparison indicates that Sorbus did not refill embolized xylem vessels whereas Sambucus reversed embolism. It was concluded that species which are highly vulnerable to cavitation and drought-induced embolism need refilling of embolized vessels as well as isohydric water potential patterns as two strategies of survival.
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stem water potential and leaf conductance a comparison of Sorbus aucuparia and sambucus nigra
Physics and Chemistry of The Earth Part B-hydrology Oceans and Atmosphere, 1999Co-Authors: U K Vogt, Robert LoschAbstract:Abstract Sorbus aucuparia is a pioneer wood which can naturally be found on extreme habitats, e.g. rocky slopes and mountain forests. Sambucus nigra is a species of flood-plain forests. The different strategies of survival of these two species were studied on planted shrubs which were exposed to the same microclimatic conditions in the outdoors of the Botanical Garden of Diisseldorf University. This situation - both species in direct neighbourhood - also exists where Sorbus aucuparia and Sambucus nigra are brought together by man in common habitats like hegerows. Measurements of stem water potential and leaf conductance were carried out on these planted shrubs during the growing season of 1995 under natural conditions. A hot dry period caused a decrease of stem water potential of Sorbus aucuparia below −4 MPa, while Sambucus nigra merely reached a minimum of −1.64 MPa. Sambucus had a lower maximum of leaf conductance than Sorbus and avoided a decrease of stem water potential by reducing leaf conductances early after the beginning of drought. By contrast Sorbus aucuparia showed high leaf conductance,; during one month of drought until water potentials of the shrub had been fallen below −4 MPa. These contrasting patterns of seasonal variations of water potential and stomatal control of transpiration confirm the classification of Sorbus aucuparia as a hydrolabile and Sambucus nigra as a hydrostabile species.
He Jiawei - One of the best experts on this subject based on the ideXlab platform.
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Studies on the quality standard of Sorbus tianschanica Rupr.
Journal of Xinjiang Medical University, 2013Co-Authors: He JiaweiAbstract:Objective To set up the quality control criteria of Sorbus tianschanica Rupr.and provide scientific basis for the utilization and development of Sorbus tianschanica Rupr..Methods Based on the Chinese Pharmacopeia(2010),thin layer chromatography(TLC)method was used for the identification of Hyperoside in Sorbus tianschanica Rupr.,and reversed phase high-performance liquid chromatography(RP-HPLC)method was established for the determination of Hyperoside and Amygdalin in Sorbus tianschanica Rupr.by gradient elution mode.Results The original identification of Sorbus tianschanica Rupr.was described and the TLC identification method was formulated with n-butyl alcohol-ethyl acetateice vinegar-water(9∶6∶3∶4)as developing solvent,temporarily formulating moisture was not over 8.0%,the total ashes was 9.0%,acid-insoluble ashes was 0.70%,the ethanol-soluble extract product was not less than 30%.Conclusion The experimental method is simple and accurate,it can be used for the quality control of Sorbus tianschanica Rupr.
Jaume Pellicer - One of the best experts on this subject based on the ideXlab platform.
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Apomixis and hybridization drives reticulate evolution and phyletic differentiation in Sorbus l.: Implications for conservation
Frontiers in plant science, 2018Co-Authors: Tracey J. Hamston, Jaume Pellicer, Michael F. Fay, Natasha De Vere, R. Andrew King, James E. Cresswell, Jamie R. StevensAbstract:Hybridisation and polyploidy are major forces in the evolution of plant diversity and the study of these processes are of particular interest to understand how novel taxa are formed and maintain genetic integrity. Sorbus is an example of a genus where active diversification and speciation are ongoing and, as such, represents an ideal model to investigate the roles of hybridisation, polyploidy and apomixis in a reticulate evolutionary process. To elucidate breeding systems and evolutionary origins of a complex of closely related Sorbus taxa, we assessed genotypic diversity and population structure within and among taxa, combining data from nuclear DNA microsatellite markers and flow cytometry. Clonal analysis and low genotypic diversity within the polyploid taxa suggest apomixis is obligate. However, genetic variation has led to groups of ‘clone-mates’ within apomictic taxa that strongly suggest mutation is responsible for the genotypic diversity of these apomictic lineages. In addition, microsatellite profiles and site demographics suggest hybridisation events among apomictic polyploid Sorbus may have contributed to the extant diversity of recognised taxa in this region. This research demonstrates that both macro- and micro-evolutionary processes are active within this reticulate Sorbus complex. Conservation measures should be aimed at maintaining this process and should therefore be prioritised for those areas of Sorbus species richness where potential for interspecific gene flow is greatest.
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multiple independent origins of intermediate species between Sorbus aucuparia and s hybrida rosaceae in the baltic region
Nordic Journal of Botany, 2018Co-Authors: Joel Levin, Jaume Pellicer, Mikael HedrenAbstract:Populations intermediate between the diploid and sexual Sorbus aucuparia and the tetraploid and facultative apomictic Sorbus hybrida are scattered in coastal regions of southern Scandinavia. Our aims were to investigate whether these populations were of local and independent origins, whether they were morphologically and molecularly distinct from each other and whether they could give rise to constant offspring by apomixis. Six intermediate populations from the Baltic Sea basin were studied for variation at nuclear and plastid microsatellite loci, for morphological differentiation patterns, and for ploidy level by flow cytometry. Seeds were sown to check for constancy with the mother plants. Three populations from Gotland and possibly the small population from Uppland were in each case fixed for a unique combination of genetic markers, had restricted variation in leaf shape and were morphologically divergent from each other. Flow cytometry analysis showed that the four genetically monomorphic populations were consistently triploid. Cultivation showed that offspring from trees within two of the monomorphic populations had leaf shapes closely similar to the mother individuals. In contrast, a population from Gotland and a population from Aland were variable at molecular marker loci and were variable in leaf shape. The three monomorphic Gotland populations and possibly also the Uppland population propagate asexually by apomixis, and they have independent origins. The two variable populations are apparently composed of hybrids that have been formed repeatedly and independently between individuals of the two parental species growing at the same sites. One of the Gotland apomicts has already been described as Sorbus teodori. Sorbus faohraei Hedren & J.Levin and Sorbus atrata Hedren & J.Levin are described as new apomictic species from Gotland. (Less)
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Data_Sheet_1_Apomixis and Hybridization Drives Reticulate Evolution and Phyletic Differentiation in Sorbus L.: Implications for Conservation.docx
2018Co-Authors: Tracey J. Hamston, Jaume Pellicer, Michael F. Fay, Natasha De Vere, James E. Cresswell, Andrew R. King, Jamie R. StevensAbstract:Hybridization and polyploidy are major forces in the evolution of plant diversity and the study of these processes is of particular interest to understand how novel taxa are formed and how they maintain genetic integrity. Sorbus is an example of a genus where active diversification and speciation are ongoing and, as such, represents an ideal model to investigate the roles of hybridization, polyploidy and apomixis in a reticulate evolutionary process. To elucidate breeding systems and evolutionary origins of a complex of closely related Sorbus taxa, we assessed genotypic diversity and population structure within and among taxa, combining data from nuclear DNA microsatellite markers and flow cytometry. Clonal analysis and low genotypic diversity within the polyploid taxa suggest apomixis is obligate. However, genetic variation has led to groups of ‘clone-mates’ within apomictic taxa that strongly suggest mutation is responsible for the genotypic diversity of these apomictic lineages. In addition, microsatellite profiles and site demographics suggest hybridization events among apomictic polyploid Sorbus may have contributed to the extant diversity of recognized taxa in this region. This research demonstrates that both macro- and micro-evolutionary processes are active within this reticulate Sorbus complex. Conservation measures should be aimed at maintaining this process and should therefore be prioritized for those areas of Sorbus species richness where the potential for interspecific gene flow is greatest.
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Polyploid wild service tree: first record of a triploid Sorbus torminalis (Rosaceae) in Britain
New Journal of Botany, 2015Co-Authors: Tracey J. Hamston, Jaume Pellicer, Michael F. FayAbstract:The genus Sorbus L. is known for its complex taxonomy involving many polyploid species. However, Sorbus torminalis (L.) Crantz has long been assumed to be uniformly diploid. An analysis of DNA content using flow cytometry revealed a triploid individual within 0.5 km of tetraploid S. devoniensis E.F. Warb. at South Tawton, Devon. The leaf morphology suggests the novel Sorbus to be a spontaneous S. torminalis triploid rather than the result of interspecific hybridisation.
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British Sorbus (Rosaceae): six new species, two hybrids and a new subgenus
New Journal of Botany, 2014Co-Authors: Tim C G Rich, L. Houston, D. Green, M. Lepší, S. Ludwig, Jaume PellicerAbstract:Six new Sorbus species are described in Sorbus subgenus Aria; S. evansii T.C.G. Rich, sp. nov., S. greenii T.C.G. Rich, sp. nov., S. herefordensis D. Green, sp. nov., S. richii L. Houston, sp. nov., S. sellii T.C.G. Rich, sp. nov., and S. spectans L. Houston, sp. nov. The occurrence of two new subgeneric hybrids is noted – S. aucuparia × minima (subgenus Soraria) and a distinct member of subgenus Tormaria of unknown parentage – which do not merit binomials. Subgenus Triparens M. Lepsi & T.C.G. Rich is described to accommodate taxa that originated as crosses between Sorbus subgenus Aria, subgenus Sorbus and subgenus Torminaria.
Ashley Robertson - One of the best experts on this subject based on the ideXlab platform.
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Breeding systems, hybridization and continuing evolution in Avon Gorge Sorbus.
Annals of botany, 2013Co-Authors: Shanna Ludwig, Libby Houston, Timothy C G Rich, Ashley Robertson, Milena Djordjevic, Radosav Cerović, Stephen Harris, Simon J. HiscockAbstract:†Background and Aims Interspecific hybridization and polyploidy are key processes in plant evolution and are responsible for ongoing genetic diversification in the genus Sorbus (Rosaceae). The Avon Gorge, Bristol, UK, is a world ‘hotspot’ for Sorbus diversity and home to diploid sexual species and polyploid apomictic species. This research investigated how mating system variation, hybridization and polyploidy interact to generate this biological diversity. †Methods Mating systems of diploid, triploid and tetraploid Sorbus taxa were analysed using pollen tube growth and seed set assays from controlled pollinations, and parent‐ offspring genotyping of progeny from open and manual pollinations. †Key Results Diploid Sorbus are outcrossing and self-incompatible (SI). Triploid taxa are pseudogamous apomicts and genetically invariable, but because they also display self-incompatibility, apomictic seed set requires pollen from other Sorbus taxa ‐ a phenomenon which offers direct opportunities for hybridization. In contrast tetraploid taxa are pseudogamous but self-compatible, so do not have the same obligate requirement for intertaxon pollination. †Conclusions The mating inter-relationships among Avon Gorge Sorbus taxa are complex and are the driving force for hybridization and ongoing genetic diversification. In particular, the presence of self-incompatibility in triploid pseudogamous apomicts imposes a requirement for interspecific cross-pollination, thereby facilitating continuing diversification and evolution through rare sexual hybridization events. This is the first report of naturally occurring pseudogamous apomictic SI plant populations, and we suggest that interspecific pollination, in combination with a relaxed endosperm balance requirement, is the most likely route to the persistence of these populations. We propose that Avon Gorge Sorbus represents a model system for studying the establishment and persistence of SI apomicts in natural populations.
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Starting a conservation collection of Sorbus pseudomeinichii – the Catacol Whitebeam
Sibbaldia: the Journal of Botanic Garden Horticulture, 2011Co-Authors: Heather Mchaffie, Natacha Frachon, Ashley RobertsonAbstract:There are three endemic Sorbus species on the Isle of Arran in Scotland: Sorbus arranensis, S. pseudofennica and S. pseudomeinichii. The latter is the most recently discovered and is represented in the wild by a single individual. Seed propagation and vegetative propagation by chip budding were initiated for all three species at the Royal Botanic Garden Edinburgh (RBGE). This has been successful and there are now conservation collections of these species growing at RBGE.
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Starting a conservation collection of Sorbus pseudomeinichii
Sibbaldia: the International Journal of Botanic Garden Horticulture, 2011Co-Authors: Heather Mchaffie, Natacha Frachon, Ashley RobertsonAbstract:There are three endemic Sorbus species on the Isle of Arran in Scotland: Sorbus arranensis, S. pseudofennica and S. pseudomeinichii. The latter is the most recently discovered and is represented in the wild by a single individual. Seed propagation and vegetative propagation by chip budding were initiated for all three species at the Royal Botanic Garden Edinburgh (RBGE). This has been successful and there are now conservation collections of these species growing at RBGE.
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hybridization and polyploidy as drivers of continuing evolution and speciation in Sorbus
Molecular Ecology, 2010Co-Authors: Ashley Robertson, Libby Houston, Timothy C G Rich, Stephen Harris, Alexandra M Allen, Cat Roberts, Jon R Bridle, Simon J. HiscockAbstract:Interspecific hybridization and polyploidy are pivotal processes in plant evolution and speciation. The fate of new hybrid and polyploid taxa is determined by their ability to reproduce either sexually or asexually. Hybrids and allopolyploids with odd chromosome numbers are frequently sterile but some establish themselves through asexual reproduction (vegetative or apomixis). This allows novel genotypes to become established by isolating them from gene flow and leads to complex patterns of variation. The genus Sorbus is a good example of taxonomic complexity arising from the combined effects of hybridization, polyploidy and apomixis. The Avon Gorge in South-west Britain contains the greatest diversity of Sorbus in Europe, with three endemic species and four putative endemic novel hybrids among its 15 native Sorbus taxa. We used a combination of nuclear microsatellite and chloroplast DNA markers to investigate the evolutionary relationships among these Sorbus taxa within the Avon Gorge. We confirm the genetic identity of putative novel taxa and show that hybridization involving sexual diploid species, primarily S. aria and S. torminalis and polyploid facultative apomictic species from subgenus Aria, has been responsible for generating this biodiversity. Importantly our data show that this creative evolutionary process is ongoing within the Avon Gorge. Conservation strategies for the rare endemic Sorbus taxa should therefore consider all Sorbus taxa within the Gorge and must strive to preserve this evolutionary process rather than simply the individual rare taxa that it produces.