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Joseph H Williams - One of the best experts on this subject based on the ideXlab platform.
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Open access - Research article THIS ARTICLE IS PART OF A SPECIAL ISSUE ENTITLED 'POLLEN - PISTIL INTERACTIONS' The evolution of pollen germination timing in flowering plants: Austrobaileya scandens (Austrobaileyaceae)
2020Co-Authors: Joseph H WilliamsAbstract:Background and aims The pollination to fertilization process (progamic phase) is thought to have become greatly abbreviated with the origin of flowering plants. In order to understand what developmental mechanisms enabled the speeding of fertilization, comparative data are needed from across the group, especially from early-divergent lineages. I studied the pollen germination process of Austrobaileya scandens, a perennial vine endemic to the Wet Tropics area of northeastern Queensland, Australia, and a member of the ancient angiosperm lineage, Austrobaileyales. Methodology I used in vivo and in vitro hand pollinations and timed collections to study development from late pollen maturation to just after germination. Then I compared the contribution of pollen germination timing to progamic phase duration in 131 angiosperm species (65 families). Principal findings Mature pollen of Austrobaileya was bicellular, starchless and moderately dehydrated—water content was 31.5 % by weight and volume increased by 57.9 % upon hydration. A callose layer in the inner intine appeared only after pollination. In vivo pollen germination followed a logarithmic curve, rising from 28 % at 1 hour after pollination (hap) to 97 % at 12 hap (R 2 ¼ 0.98). Sufficient pollen germination to fertilize all ovules was predicted to have occurred within 62 min. Across angiosperms, pollen germination ranged from 1 min to .60 h long and required 8.3+ 9.8 % of the total duration of the progamic phase.
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The Evolution of Pollen Germination Timing in Flowering Plants: Austrobaileya Scandens (Austrobaileyaceae)
Aob Plants, 2012Co-Authors: Joseph H WilliamsAbstract:Background and aims The pollination to fertilization process (progamic phase) is thought to have become greatly abbreviated with the origin of flowering plants. In order to understand what developmental mechanisms enabled the speeding of fertilization, comparative data are needed from across the group, especially from early-divergent lineages. I studied the pollen germination process of Austrobaileya scandens, a perennial vine endemic to the Wet Tropics area of northeastern Queensland, Australia, and a member of the ancient angiosperm lineage, Austrobaileyales.
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Developmental evolution of flowering plant pollen tube cell walls: callose synthase (CalS) gene expression patterns
EvoDevo, 2011Co-Authors: Jason M Abercrombie, Brian C O'meara, Andrew R Moffatt, Joseph H WilliamsAbstract:Background A number of innovations underlie the origin of rapid reproductive cycles in angiosperms. A critical early step involved the modification of an ancestrally short and slow-growing pollen tube for faster and longer distance transport of sperm to egg. Associated with this shift are the predominantly callose (1,3-β-glucan) walls and septae (callose plugs) of angiosperm pollen tubes. Callose synthesis is mediated by callose synthase (CalS). Of 12 CalS gene family members in Arabidopsis , only one ( CalS5 ) has been directly linked to pollen tube callose. CalS5 orthologues are present in several monocot and eudicot genomes, but little is known about the evolutionary origin of CalS5 or what its ancestral function may have been. Results We investigated expression of CalS in pollen and pollen tubes of selected non-flowering seed plants (gymnosperms) and angiosperms within lineages that diverged below the monocot/eudicot node. First, we determined the nearly full length coding sequence of a CalS5 orthologue from Cabomba caroliniana ( CcCalS5 ) (Nymphaeales). Semi-quantitative RT-PCR demonstrated low CcCalS5 expression within several vegetative tissues, but strong expression in mature pollen. CalS transcripts were detected in pollen tubes of several species within Nymphaeales and Austrobaileyales, and comparative analyses with a phylogenetically diverse group of sequenced genomes indicated homology to CalS5 . We also report in silico evidence of a putative CalS5 orthologue from Amborella . Among gymnosperms, CalS5 transcripts were recovered from germinating pollen of Gnetum and Ginkgo , but a novel CalS paralog was instead amplified from germinating pollen of Pinus taeda . Conclusion The finding that CalS5 is the predominant callose synthase in pollen tubes of both early-diverging and model system angiosperms is an indicator of the homology of their novel callosic pollen tube walls and callose plugs. The data suggest that CalS5 had transient expression and pollen-specific functions in early seed plants and was then recruited to novel expression patterns and functions within pollen tube walls in an ancestor of extant angiosperms.
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Pollination biology of basal angiosperms (ANITA grade)
American Journal of Botany, 2008Co-Authors: Leonard B. Thien, Peter Bernhardt, Margaret S. Devall, Zhiduan Chen, Liang-chen Yuan, Joseph H WilliamsAbstract:The fi rst three branches of the angiosperm phylogenetic tree consist of eight families with ~201 species of plants (the ANITA grade). The oldest fl ower fossil for the group is dated to the Early Cretaceous (115 - 125 Mya) and identifi ed to the Nymphaeales. The fl owers of extant plants in the ANITA grade are small, and pollen is the edible reward (rarely nectar or starch bodies). Unlike many gymnosperms that secrete " pollination drops, " ANITA-grade members examined thus far have a dry-type stigma. Copious secretions of stigmatic fl uid are restricted to the Nymphaeales, but this is not nectar. Floral odors, fl oral thermogenesis (a re- source), and colored tepals attract insects in deceit-based pollination syndromes throughout the fi rst three branches of the phylo- genetic tree. Self-incompatibility and an extragynoecial compitum occur in some species in the Austrobaileyales. Flies are primary pollinators in six families (10 genera). Beetles are pollinators in fi families varying in importance as primary (exclusive) to secondary vectors of pollen. Bees are major pollinators only in the Nymphaeaceae. It is hypothesized that large fl owers in Nympha- eaceae are the result of the interaction of heat, fl oral odors, and colored tepals to trap insects to increase fi tness.
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Microsatellite loci for the basal angiosperm Austrobaileya scandens (Austrobaileyaceae)
Molecular Ecology Notes, 2006Co-Authors: Joseph H Williams, Kimberly S. KennardAbstract:AbstractWe developed nine microsatellite loci for the basal angiosperm Austrobaileya scandens ,a vine endemic to northeastern Australia. High levels of polymorphism were detected in30 individuals from a single population, with an average of 14.78 alleles per locus and anaverage expected heterozygosity of 0.81. Historical inbreeding levels were significantlydifferent from zero ( f = 0.136), consistent with genetic evidence for self-parentage in open-pollinated progeny. The high exclusionary power of these loci (> 99.98%) indicates theywill be useful in future parentage analyses designed to explore mechanisms of mate choicein Austrobaileya . Keywords : Austrobaileya , Austrobaileyales, basal angiosperm, mating system, microsatellite loci,self-incompatibility, vine Received 3 August 2005; revision accepted 7 September 2005 The origin of the angiosperm reproductive syndrome hasbeen the subject of much discussion over the last century.Most recently, the debate has been fuelled by improvedanalyses of structural features of ancient fossil angiosperms(Friis
William E Friedman - One of the best experts on this subject based on the ideXlab platform.
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Prolonged embryogenesis in Austrobaileya scandens (Austrobaileyaceae): its ecological and evolutionary significance
New Phytologist, 2017Co-Authors: Juan M. Losada, Julien B. Bachelier, William E FriedmanAbstract:Summary The embryology of basal angiosperm lineages (Amborella, Nymphaeales and Austrobaileyales) is central to reconstructing the early evolution of flowering plants. Previous studies have shown that mature seeds in Austrobaileyales are albuminous, with a small embryo surrounded by a substantial diploid endosperm. However, little is known of seed ontogeny and seedling germination in Austrobaileya scandens, sister to all other extant Austrobaileyales. Standard histochemical techniques were used to study ovule/seed development and germination of Austrobaileya. Early development of the endosperm in Austrobaileya is ab initio cellular with pronounced cell proliferation. The nucellus transiently accumulates some starch, but is obliterated by expansion of a massive endosperm, where all embryo-nourishing reserves are ultimately stored. Twelve months elapse from fertilization to fruit abscission. Seeds are dispersed with a minute embryo, requiring 12 additional months for seedling establishment. The 2 yr required for seedling establishment is an apomorphic feature of Austrobaileya, probably related to germination in extremely dark understory conditions. Remarkably, although Austrobaileya seeds are nearly 50 times larger (by length) than the smallest seeds of extinct and extant members of early divergent angiosperm lineages, the embryo to seed ratio (E : S) falls squarely within the narrow range that characterizes the albuminous seeds of ancient flowering plant lineages.
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Seed development in Trimenia (Trimeniaceae) and its bearing on the evolution of embryo‐nourishing strategies in early flowering plant lineages
American Journal of Botany, 2013Co-Authors: William E Friedman, Julien B. BachelierAbstract:Seeds of most families in the ancient angiosperm lineage Austrobaileyales produce a full-fledged genetically biparental embryo-nourishing endosperm. However, seeds of fossil and extant Trimeniaceae have been described as having a perisperm, a maternal nutrient-storing and embryo-nourishing tissue derived from the nucellus of the ovule. Because perisperm is also found in Nymphaeales, another ancient angiosperm clade, the presence of a perisperm in Trimeniaceae, if confirmed, would be congruent with the hypothesis that the first angiosperms used a perisperm in addition to a minute (nutrient-transferring) endosperm. • Seed development was studied from fertilization through maturity/dormancy in Trimenia moorei and in maturing fruits of T. neocaledonica. • A persistent layer of nucellar tissue surrounds the endosperm but does not contain stored nutrients and does not function as a perisperm. The nutrient-storing and embryo-nourishing tissue in Trimenia seeds is an endosperm, as is the case in all other members of the Austrobaileyales studied to date. • The absence of a perisperm and the presence of a typical nutrient-storing and embryo-nourishing endosperm in Trimeniaceae may represent the ancestral condition for angiosperms. However, the combination of a copious nutrient-storing and embryo-nourishing perisperm with a minute endosperm, as in Nymphaeales, remains a plausible plesiomorphic condition for angiosperms as a whole. In either case, the developmental and functional biology of the diploid endosperm of Trimenia (and other Austrobaileyales) differs markedly from the diploid endosperm of Nymphaeales, and is fundamentally similar to the triploid endosperms of most other angiosperms.
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Female gamete competition in an ancient angiosperm lineage
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Julien B. Bachelier, William E FriedmanAbstract:In Trimenia moorei, an extant member of the ancient angiosperm clade Austrobaileyales, we found a remarkable pattern of female gametophyte (egg-producing structure) development that strikingly resembles that of pollen tubes and their intrasexual competition within the maternal pollen tube transmitting tissues of most flowers. In contrast with most other flowering plants, in Trimenia, multiple female gametophytes are initiated at the base (chalazal end) of each ovule. Female gametophytes grow from their tips and compete over hundreds of micrometers to reach the apex of the nucellus and the site of fertilization. Here, the successful female gametophyte will mate with a pollen tube to produce an embryo and an endosperm. Moreover, the central tissue within the ovules of Trimenia, through which the embryo sacs grow, contains starch and other carbohydrates similar to the pollen tube transmitting tissues in the styles of most flowers. The pattern of female gametophyte development found in Trimenia is rare but by no means unique in angiosperms. Importantly, it seems that multiple female gametophytes are occasionally or frequently initiated in members of other ancient angiosperm lineages. The intensification of pollen tube (male gametophyte) competition and enhanced maternal selection among competing pollen tubes are considered to have been major contributors to the rise of angiosperms. Based on insights from Trimenia, we posit that prefertilization female gametophyte (egg) competition within individual ovules in addition to male gametophyte (sperm) competition and maternal mate choice may have been key features of the earliest angiosperms.
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Reconstructing the ancestral female gametophyte of angiosperms: Insights from Amborella and other ancient lineages of flowering plants
American Journal of Botany, 2008Co-Authors: William E Friedman, Kirsten C. RyersonAbstract:For more than a century, the common ancestor of fl plants was thought to have had a seven-celled, eight-nucleate Polygonum-type female gametophyte. It is now evident that not one, but in fact three, patterns of female gametophyte development and mature structure characterize the common ancestors of the four most ancient clades of extant angiosperms: Amborellatype, Nuphar/Schisandra-type and Polygonum-type. The Amborella-type female gametophyte is restricted to a single extant species, Amborella trichopoda , and at maturity consists of eight cells and nine nuclei. Development of the Amborella-type gametophyte is essentially identical to the Polygonum-type except that there is an additional and asynchronous cell division at the micropylar pole prior to maturation that produces a third synergid and the egg cell. The Nuphar/Schisandra-type female gametophyte is four-nucleate and four-celled and at maturity contains a typical three-celled egg apparatus and a central cell with a single haploid polar nucleus. This type of gametophyte appears to be universal among extant members of the Nymphaeales (including Hydatellaceae) and Austrobaileyales. Based on explicit reconstruction of character distribution and evolution, the Polygonum-type female gametophyte is certain to be representative of the common ancestors of monocots, eudicots, magnoliids, Ceratophyllaceae, and Chloranthaceae. There are compelling biological reasons to suggest that the four-celled, four-nucleate female gametophyte (as found in Nymphaeales and Austrobaileyales) is ancestral among angiosperms, with transitions to Polygonum-type female gametophytes separately in the Amborellales and in the ancient angiosperm clade that includes all angiosperms except Amborella , Nymphaeales, and Austrobaileyales. Subsequent to the evolution of a seven-celled, eight-nucleate Polygonum-type female gametophyte in the Amborellales, we hypothesize that a peramorphic increase in egg apparatus cell number took place and led to the unique situation in which there are three synergids in Amborella trichopoda .
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the four celled female gametophyte of illicium illiciaceae Austrobaileyales implications for understanding the origin and early evolution of monocots eumagnoliids and eudicots
American Journal of Botany, 2004Co-Authors: Joseph H Williams, William E FriedmanAbstract:The recent consensus that Amborellaceae, Nymphaeales, and Austrobaileyales form the three earliest-diverging lineages of angiosperms has led comparative biologists to reconsider the origin and early developmental evolution of the angiosperm seven-celled/eightnucleate (Polygonum-type) female gametophyte. Illicium mexicanum(Illiciaceae; Austrobaileyales) develops a four-celled/four-nucleate female gametophyte. The ontogenetic sequence of the Illicium female gametophyte is consistent with that of all other Austrobaileyales and also with all Nymphaeales and is likely a plesiomorphy of angiosperms. A character analysis based on more than 250 embryological studies indicates that a transition from an ancestrally four-celled/four-nucleate Illicium-like female gametophyte to a seven-celled/eightnucleate female gametophyte occurred in the common ancestor of the sister group to Austrobaileyales (a clade that includes monocots, eumagnoliids, and eudicots). Comparative analysis of reconstructed ancestral female gametophyte ontogenies identifies specific early stages of ontogeny that were modified during this transition. These modifications generated two important angiosperm novelties—a set of three persistent antipodal cells and a binucleate central cell, which upon fertilization yields a triploid endosperm. Early angiosperms are anatomically quite diverse in these two features, although triploid endosperm, composed of one paternal genome and two maternal genomes, is a conserved feature of the overwhelming majority of angiosperms.
Peter K. Endress - One of the best experts on this subject based on the ideXlab platform.
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Ancestral traits and specializations in the flowers of the basal grade of living angiosperms
Taxon, 2015Co-Authors: Peter K. Endress, James A. DoyleAbstract:© International Association for Plant Taxonomy (IAPT) 2015. New morphological and phylogenetic data prompt us to present an updated review of floral morphology and its evolution in the basal ANITA grade of living angiosperms, Chloranthaceae, and Ceratophyllum. Floral phyllotaxis is complex whorled in Nymphaeales and spiral in Amborella and Austrobaileyales. It is unresolved whether phyllotaxis was ancestrally whorled or spiral, but if it was whorled, the whorls were trimerous. The flowers are probably ancestrally bisexual because in most families with unisexual flowers these flowers exhibit rudiments of the opposite sex. Carpels are largely ascidiate and the closure line is short, either transverse or longitudinal. A style is usually absent or, if present, generally short and not plicate. Angiospermy (carpel sealing) is by secretion, rather than postgenital fusion, except in large-flowered Nymphaeales and in Illicium, correlated with unusual fruits. Carpels with a single, median, pendent ovule are probably plesiomorphic. Chloranthaceae and Ceratophyllaceae have an unsettled phylogenetic position, but in some phylogenetic analyses they form a clade, which may be sister to the remaining mesangiosperms (Magnoliidae, monocots, eudicots). This position is supported by their carpel characters, which are similar to those of the ANITA grade and different from those of most other mesangiosperms.
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Integrating Early Cretaceous Fossils into the Phylogeny of Living Angiosperms: ANITA Lines and Relatives of Chloranthaceae
International Journal of Plant Sciences, 2014Co-Authors: James A. Doyle, Peter K. EndressAbstract:Premise of research. Discoveries of fossil flowers in Cretaceous rocks offer improved evidence for relationships with living clades, but for more secure inferences formal phylogenetic analyses are desirable. We extend previous analyses of magnoliids, monocots, and basal eudicots to Aptian, Albian, and Cenomanian fossils related to the basal “ANITA” lines and Chloranthaceae.Methodology. We performed parsimony analyses of a morphological data set of Recent angiosperms and published fossils, with the arrangement of Recent taxa constrained to backbone trees based primarily on molecular data.Pivotal results. Not only Monetianthus (as previously inferred) but also Carpestella is nested within Nymphaeaceae, while Pluricarpellatia may be a stem relative of Cabombaceae or Nymphaeaceae. Anacostia (with Similipollis pollen) is nested within Austrobaileyales. The position of Couperites (with Clavatipollenites pollen) is ambiguous: it may be on the stem lineage of Chloranthaceae (and Ceratophyllum, if this extant aqua...
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structure of the unusual explosive fruits of the early diverging angiosperm illicium schisandraceae s l Austrobaileyales
Botanical Journal of the Linnean Society, 2013Co-Authors: Mikhail S Romanov, Alexey Ch V F Bobrov, Peter K. EndressAbstract:All Illicium spp. have explosive fruits, which is a unique character among the basal grade of angiosperms. Illicium fruits consist of several ventrally dehiscing follicles developing from conduplicate carpels, with a prominent, slightly postgenitally fused ventral slit. The closure of the ventral slit is also secured by two mirror-symmetrical massive longitudinal sclerenchymatous bands in the mesocarp along the edges and by turgor pressure. The pericarp differentiates into a fleshy (or coriaceous) peripheral zone (exocarp and mesocarp) with numerous ethereal-oil-containing cells and a sclerenchymatous (single-layered, palisade) inner zone (endocarp). Dehydration of the fleshy zone of the pericarp and partial compression of the epidermal sclereids with U-shaped wall thickenings lining the ventral suture are instrumental in explosive fruitlet dehiscence. Generally, the fruit structure of Illicium differs dramatically from those in other early diverging angiosperms. Gynoecium and fruit structure (and a probable early Cretaceous divergence from the Schisandra-Kadsura clade) provide evidence for treatment of Illicium as separate from Schisandraceae s.s. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 171, 640–654.
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Perianth Biology in the Basal Grade of Extant Angiosperms
International Journal of Plant Sciences, 2008Co-Authors: Peter K. EndressAbstract:Perianth structure and behavior were studied comparatively in representatives of all families of the basalmost extant angiosperms (ANITA grade plus Chloranthaceae). In addition, data from the literature were reviewed. Tepal aestivation is spiral imbricate in Amborella and Austrobaileyales, with broadly overlapping flanks; aestivation is mainly contort within each of the two tepal whorls in Cabomba (but open within each whorl and imbricate only between whorls in Brasenia) and is whorled imbricate in Nymphaeaceae. Tepals are absent in Hydatellaceae, Chloranthaceae (other than Hedyosmum), and Ceratophyllaceae. In two genera of Nymphaeales (Cabomba and Nuphar), nectaries are present on inner tepals. Tepals are caducous during or at the end of anthesis in Austrobaileyales. Preformations of the tepal abscission zone in flowers with caducous tepals include a narrow tepal base, constriction as seen in median longitudinal sections, and small‐celled tissue. In contrast, the perianth organs of Amborella, Nymphaeales...
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Hydatellaceae identified as a new branch near the base of the angiosperm phylogenetic tree
Nature, 2007Co-Authors: Jeffery M. Saarela, Peter K. Endress, James A. Doyle, Sarah Mathews, Adam D. Marchant, Barbara G. Briggs, Sean W. GrahamAbstract:Although the relationship of angiosperms to other seed plants remains controversial^ 1 , great progress has been made in identifying the earliest extant splits in flowering-plant phylogeny, with the discovery that the New Caledonian shrub Amborella trichopoda , the water lilies (Nymphaeales), and the woody Austrobaileyales constitute a basal grade of lines that diverged before the main radiation in the clade^ 2 , 3 , 4 , 5 , 6 , 7 , 8 . By focusing attention on these ancient lines, this finding has re-written our understanding of angiosperm structural and reproductive biology, physiology, ecology and taxonomy^ 9 , 10 , 11 , 12 . The discovery of a new basal lineage would lead to further re-evaluation of the initial angiosperm radiation, but would also be unexpected, as nearly all of the ∼460 flowering-plant families have been surveyed in molecular studies^ 10 . Here we show that Hydatellaceae, a small family of dwarf aquatics that were formerly interpreted as monocots, are instead a highly modified and previously unrecognized ancient lineage of angiosperms. Molecular phylogenetic analyses of multiple plastid genes and associated noncoding regions from the two genera of Hydatellaceae identify this overlooked family as the sister group of Nymphaeales. This surprising result is further corroborated by evidence from the nuclear gene phytochrome C ( PHYC ), and by numerous morphological characters. This indicates that water lilies are part of a larger lineage that evolved more extreme and diverse modifications for life in an aquatic habitat than previously recognized. The Hydatellaceae are small aquatic plants living modest lives away from the limelight, and conventionally assumed to be monocotyledonous flowering plants related to grasses. Now they have been subjected to the latest molecular techniques, and they turn out to be close relatives of basal angiosperms such as water lilies, increasing their importance immensely. They belong to a previously unrecognized lineage branching near the root of the angiosperms — a radical addition to the three deepest branches discovered in 1999 that rekindled interest amongst molecular biologists in the origin of angiosperms, what Darwin called an “abominable mystery”.
Douglas E. Soltis - One of the best experts on this subject based on the ideXlab platform.
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Angiosperm phylogeny based on matK sequence information
American Journal of Botany, 2020Co-Authors: Khidir W. Hilu, Pamela S. Soltis, Douglas E. Soltis, Thomas Borsch, Kai F. Müller, Vincent Savolainen, Mark W. Chase, Martyn P. Powell, Lawrence A. Alice, Rodger C. EvansAbstract:Plastid matK gene sequences for 374 genera representing all angiosperm orders and 12 genera of gymnosperms were analyzed using parsimony (MP) and Bayesian inference (BI) approaches. Traditionally, slowly evolving genomic regions have been preferred for deep-level phylogenetic inference in angiosperms. The matK gene evolves approximately three times faster than the widely used plastid genes rbcL and atpB. The MP and BI trees are highly congruent. The robustness of the strict consensus tree supercedes all individual gene analyses and is comparable only to multigene-based phylogenies. Of the 385 nodes resolved, 79% are supported by high jackknife values, averaging 88%. Amborella is sister to the remaining angiosperms, followed by a grade of Nymphaeaceae and Austrobaileyales. Bayesian inference resolves Amborella 1 Nymphaeaceae as sister to the rest, but with weak (0.42) posterior probability. The MP analysis shows a trichotomy sister to the Austrobaileyales representing eumagnoliids, monocots 1 Chloranthales, and Ceratophyllum 1 eudicots. The matK gene produces the highest internal support yet for basal eudicots and, within core eudicots, resolves a crown group comprising Berberidopsidaceae/Aextoxicaceae, Santalales, and Caryophyllales 1 asterids. Moreover, matK sequences provide good resolution within many angiosperm orders. Combined analyses of matK and other rapidly evolving DNA regions with available multigene data sets have strong potential to enhance resolution and internal support in deep level angiosperm phylogenetics and provide additional insights into angiosperm evolution.
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The origin and diversification of angiosperms.
American Journal of Botany, 2020Co-Authors: Pamela S. Soltis, Douglas E. SoltisAbstract:The angiosperms, one of five groups of extant seed plants, are the largest group of land plants. Despite their relatively recent origin, this clade is extremely diverse morphologically and ecologically. However, angiosperms are clearly united by several synapomorphies. During the past 10 years, higher-level relationships of the angiosperms have been resolved. For example, most analyses are consistent in identifying Amborella, Nymphaeaceae, and Austrobaileyales as the basalmost branches of the angiosperm tree. Other basal lineages include Chloranthaceae, magnoliids, and monocots. Approximately three quarters of all angiosperm species belong to the eudicot clade, which is strongly supported by molecular data but united morphologically by a single synapomorphy-triaperturate pollen. Major clades of eudicots include Ranunculales, which are sister to all other eudicots, and a Glade of core eudicots, the largest members of which are Saxifragales, Caryophyllales, rosids, and asterids. Despite rapid progress in resolving angiosperm relationships, several significant problems remain: (1) relationships among the monocots, Chloranthaceae, magnoliids, and eudicots, (2) branching order among basal eudicots, (3) relationships among the major clades of core eudicots, (4) relationships within rosids, (5) relationships of the many lineages of parasitic plants, and (6) integration of fossils with extant taxa into a comprehensive tree of angiosperm phylogeny.
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Floral variation and floral genetics in basal angiosperms
American Journal of Botany, 2020Co-Authors: Pamela S. Soltis, Samuel F. Brockington, Ana Piedrahita, Maribeth Latvis, Michael J. Moore, Andre S. Chanderbali, Douglas E. SoltisAbstract:Recent advances in phylogeny reconstruction and fl oral genetics set the stage for new investigations of the origin and diversifi cation of the fl ower. We review the current state of angiosperm phylogeny, with an emphasis on basal lineages. With the surprising inclusion of Hydatellaceae with Nymphaeales, recent studies support the topology of Amborella sister to all other extant angiosperms, with Nymphaeales and then Austrobaileyales as subsequent sisters to all remaining angiosperms. Notable modifi cations from most recent analyses are the sister relationships of Chloranthaceae with the magnoliids and of Ceratophyllaceae with eudicots. We review “ trends ” in fl oral morphology and contrast historical, intuitive interpretations with explicit character-state reconstructions using molecular-based trees, focusing on (1) the size, number, and organization of florgans; (2) the evolution of the perianth; (3) fl oral symmetry; and (4) fl oral synorganization. We provide summaries of those genes known to affect fl oral features that contribute to much of fldiversity. Although most fl oral genes have not been investigated outside of a few model systems, suffi cient information is emerging to identify candidate genes for testing specifi c hypotheses in nonmodel plants. We conclude with a set of evo-devo case studies in which fl oral genetics have been linked to variation in flmorphology.
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Phylogeny and diversification of B-function MADS-box genes in angiosperms: evolutionary and functional implications of a 260-million-year-old duplication
American Journal of Botany, 2020Co-Authors: Victor A. Albert, Pamela S. Soltis, James S. Farris, Douglas E. SoltisAbstract:B-function MADS-box genes play crucial roles in floral development in model angiosperms. We reconstructed the structural and functional implications of B-function gene phylogeny in the earliest extant flowering plants based on analyses that include 25 new AP3 and PI sequences representing critical lineages of the basalmost angiosperms: Amborella, Nuphar (Nymphaeaceae), and Illicium (Austrobaileyales). The ancestral size of exon 5 in PI-homologues is 42 bp, typical of exon 5 in other plant MADS-box genes. This 42-bp length is found in PI-homologues from Amborella and Nymphaeaceae, successive sisters to all other angiosperms. Following these basalmost branches, a deletion occurred in exon 5, yielding a length of 30 bp, a condition that unites all other angiosperms. Several shared amino acid strings, including a prominent "DEAER" motif, are present in the AP3- and PI-homologues of Amborella. These may be ancestral motifs that were present before the duplication that yielded the AP3 and PI lineages and subsequently were modified after the divergence of Amborella. Other structural features were identified, including a motif that unites the previously described TM6 clade and a deletion in AP3-homologues that unites all Magnoliales. Phylogenetic analyses of AP3- and PI-homologues yielded gene trees that generally track organismal phylogeny as inferred by multigene data sets. With both AP3 and PI amino acid sequences, Amborella and Nymphaeaceae are sister to all other angiosperms. Using nonparametric rate smoothing (NPRS), we estimated that the duplication that produced the AP3 and PI lineages occurred approximately 260 mya (231-290). This places the duplication after the split between extant gymnosperms and angiosperms, but well before the oldest angiosperm fossils. A striking similarity in the multimer-signalling C domains of the Amborella proteins suggests the potential for the formation of unique transcription-factor complexes. The earliest angiosperms may have been biochemically flexible in their B function and "tinkered" with floral organ identity.
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An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG IV
Botanical Journal of the Linnean Society, 2016Co-Authors: K. Bremer, Pamela S. Soltis, Douglas E. Soltis, Mark W. Chase, J. L. Reveal, Peter F. StevensAbstract:A revised and updated classification for the families of the flowering plants is provided. Newly adopted orders include Austrobaileyales, Canellales, Gunnerales, Crossosomatales and Celastrales. Pertinent literature published since the first APG classification is included, such that many additional families are now placed in the phylogenetic scheme. Among these are Hydnoraceae (Piperales), Nartheciaceae (Dioscoreales), Corsiaceae (Liliales), Triuridaceae (Pandanales), Hanguanaceae (Commelinales), Bromeliacae, Mayacaceae and Rapateaceae (all Poales), Barbeuiaceae and Gisekiaceae (both Caryophyllales), Geissolomataceae, Strasburgeriaceae and Vitaceae (unplaced to order, but included in the rosids), Zygophyllaceae (unplaced to order, but included in eurosids I), Bonnetiaceae, Ctenolophonaceae, Elatinaceae, Ixonanthaceae, Lophopyxidaceae, Podostemaceae (Malpighiales), Paracryphiaceae (unplaced in euasterid II), Sladeniaceae, Pentaphylacaceae (Ericales) and Cardiopteridaceae (Aquifoliales). Several major families are recircumscribed. Salicaceae are expanded to include a large part of Flacourtiaceae, including the type genus of that family; another portion of former Flacourtiaceae is assigned to an expanded circumscription of Achariaceae. Euphorbiaceae are restricted to the uniovulate subfamilies; Phyllanthoideae are recognized as Phyllanthaceae and Oldfieldioideae as Picrodendraceae. Scrophulariaceae are recircumscribed to include Buddlejaceae and Myoporaceae and exclude several former members; these are assigned to Calceolariaceae, Orobanchaceae and Plantaginaceae. We expand the use of bracketing families that could be included optionally in broader circumscriptions with other related families; these include Agapanthaceae and Amaryllidaceae in Alliaceae s.l. , Agavaceae, Hyacinthaceae and Ruscaceae (among many other Asparagales) in Asparagaceae s.l. , Dichapetalaceae in Chrysobalanaceae, Turneraceae in Passifloraceae, Erythroxylaceae in Rhizophoraceae, and Diervillaceae, Dipsacaceae, Linnaeaceae, Morinaceae and Valerianaceae in Caprifoliaceae s.l. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 141 , 399‐436.
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Ancestral traits and specializations in the flowers of the basal grade of living angiosperms
Taxon, 2015Co-Authors: Peter K. Endress, James A. DoyleAbstract:© International Association for Plant Taxonomy (IAPT) 2015. New morphological and phylogenetic data prompt us to present an updated review of floral morphology and its evolution in the basal ANITA grade of living angiosperms, Chloranthaceae, and Ceratophyllum. Floral phyllotaxis is complex whorled in Nymphaeales and spiral in Amborella and Austrobaileyales. It is unresolved whether phyllotaxis was ancestrally whorled or spiral, but if it was whorled, the whorls were trimerous. The flowers are probably ancestrally bisexual because in most families with unisexual flowers these flowers exhibit rudiments of the opposite sex. Carpels are largely ascidiate and the closure line is short, either transverse or longitudinal. A style is usually absent or, if present, generally short and not plicate. Angiospermy (carpel sealing) is by secretion, rather than postgenital fusion, except in large-flowered Nymphaeales and in Illicium, correlated with unusual fruits. Carpels with a single, median, pendent ovule are probably plesiomorphic. Chloranthaceae and Ceratophyllaceae have an unsettled phylogenetic position, but in some phylogenetic analyses they form a clade, which may be sister to the remaining mesangiosperms (Magnoliidae, monocots, eudicots). This position is supported by their carpel characters, which are similar to those of the ANITA grade and different from those of most other mesangiosperms.
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Angiosperm Clades in the Potomac Group: What Have We Learned since 1977?
Bulletin of The Peabody Museum of Natural History, 2014Co-Authors: James A. Doyle, Garland R. UpchurchAbstract:Abstract In their 1977 study on Potomac Group angiosperms, Hickey and Doyle made only broad comparisons with living taxa. Newer data, especially discoveries of fossil flowers in the Potomac and coeval deposits and increasingly robust molecular phylogenies of living angiosperms, allow more precise phylogenetic placement of fossils. Hickey and Doyle compared most early Potomac leaves (Aptian—early Albian) with “magnoliids,” a paraphyletic group as then defined, but several clades can now be recognized. Leaves and dispersed cuticles share epidermal features with woody members of the basal ANITA grade, and in some cases crown group Austrobaileyales, whose presence is confirmed by flowers called Anacostia. Aptian—Albian flowers (Monetianthus, Carpestella) and whole plants (Pluricarpellatia) are nested in crown group Nymphaeales; Potomac reniform leaves could belong to this clade. Several Potomac leaves have chloranthoid teeth, venation, and opposite phyllotaxis consistent with Chloranthaceae, while Aptian to C...
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Integrating Early Cretaceous Fossils into the Phylogeny of Living Angiosperms: ANITA Lines and Relatives of Chloranthaceae
International Journal of Plant Sciences, 2014Co-Authors: James A. Doyle, Peter K. EndressAbstract:Premise of research. Discoveries of fossil flowers in Cretaceous rocks offer improved evidence for relationships with living clades, but for more secure inferences formal phylogenetic analyses are desirable. We extend previous analyses of magnoliids, monocots, and basal eudicots to Aptian, Albian, and Cenomanian fossils related to the basal “ANITA” lines and Chloranthaceae.Methodology. We performed parsimony analyses of a morphological data set of Recent angiosperms and published fossils, with the arrangement of Recent taxa constrained to backbone trees based primarily on molecular data.Pivotal results. Not only Monetianthus (as previously inferred) but also Carpestella is nested within Nymphaeaceae, while Pluricarpellatia may be a stem relative of Cabombaceae or Nymphaeaceae. Anacostia (with Similipollis pollen) is nested within Austrobaileyales. The position of Couperites (with Clavatipollenites pollen) is ambiguous: it may be on the stem lineage of Chloranthaceae (and Ceratophyllum, if this extant aqua...
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Evolutionary significance of granular exine structure in the light of phylogenetic analyses.
Review of Palaeobotany and Palynology, 2009Co-Authors: James A. DoyleAbstract:In 1973 Van Campo and Lugardon recognized granular structure as a third major type of exine structure in seed plants, in addition to columellar (restricted to angiosperms) and alveolar (restricted to other seed plants, such as cycads and saccate conifers). Because they found granular structure both in other seed plants (non-saccate conifers, Gnetales) and in angiosperms (some Magnoliales, monocots, and “Amentiferae”), they suggested it might be ancestral in angiosperms. This suggestion was elaborated by other workers and supported by studies of Le Thomas and Lugardon on Annonaceae (Magnoliales), which appeared to show origin of columellae by various modifications of granules. Phylogenetic (cladistic) analyses of seed plants based on morphological and molecular data modify this scheme considerably but reaffirm the systematic interest of granular structure. In conifers and Gnetales (which probably form a clade), granular structure appears to be derived from alveolar (as in Pinaceae, Podocarpaceae and extinct outgroups of conifers). Molecular analyses root the phylogenetic tree of angiosperms among Amborella, Nymphaeales, and Austrobaileyales, which have columellar and related exine structures, implying that granular exines were derived within angiosperms. This contradicts earlier views that granular structure provides evidence for a relationship between angiosperms and outgroups such as Gnetales and Bennettitales. Phylogenetic analyses indicate that granular structure was derived from columellar within Magnoliales and Laurales, in each of which it is an important synapomorphy of a major subgroup; the same may also be true for Fagales. However, phylogenetic analyses of Annonaceae confirm that granular structure is ancestral in this group and columellar is derived, essentially as a reversal to the ancestral state in angiosperms. In Fagales granular structure is associated with wind pollination, but not in Magnoliales and Laurales; however, in all three cases it may be correlated with reduction in exine thickness.
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Hydatellaceae identified as a new branch near the base of the angiosperm phylogenetic tree
Nature, 2007Co-Authors: Jeffery M. Saarela, Peter K. Endress, James A. Doyle, Sarah Mathews, Adam D. Marchant, Barbara G. Briggs, Sean W. GrahamAbstract:Although the relationship of angiosperms to other seed plants remains controversial^ 1 , great progress has been made in identifying the earliest extant splits in flowering-plant phylogeny, with the discovery that the New Caledonian shrub Amborella trichopoda , the water lilies (Nymphaeales), and the woody Austrobaileyales constitute a basal grade of lines that diverged before the main radiation in the clade^ 2 , 3 , 4 , 5 , 6 , 7 , 8 . By focusing attention on these ancient lines, this finding has re-written our understanding of angiosperm structural and reproductive biology, physiology, ecology and taxonomy^ 9 , 10 , 11 , 12 . The discovery of a new basal lineage would lead to further re-evaluation of the initial angiosperm radiation, but would also be unexpected, as nearly all of the ∼460 flowering-plant families have been surveyed in molecular studies^ 10 . Here we show that Hydatellaceae, a small family of dwarf aquatics that were formerly interpreted as monocots, are instead a highly modified and previously unrecognized ancient lineage of angiosperms. Molecular phylogenetic analyses of multiple plastid genes and associated noncoding regions from the two genera of Hydatellaceae identify this overlooked family as the sister group of Nymphaeales. This surprising result is further corroborated by evidence from the nuclear gene phytochrome C ( PHYC ), and by numerous morphological characters. This indicates that water lilies are part of a larger lineage that evolved more extreme and diverse modifications for life in an aquatic habitat than previously recognized. The Hydatellaceae are small aquatic plants living modest lives away from the limelight, and conventionally assumed to be monocotyledonous flowering plants related to grasses. Now they have been subjected to the latest molecular techniques, and they turn out to be close relatives of basal angiosperms such as water lilies, increasing their importance immensely. They belong to a previously unrecognized lineage branching near the root of the angiosperms — a radical addition to the three deepest branches discovered in 1999 that rekindled interest amongst molecular biologists in the origin of angiosperms, what Darwin called an “abominable mystery”.