Oncothecales

EMBRYOPSIDA Pirani & Prado

Gametophyte dominant, independent, multicellular, initially ±globular, not motile, branched; showing gravitropism; glycolate oxidase +, glycolate metabolism in leaf peroxisomes [glyoxysomes], acquisition of phenylalanine lysase* [PAL], flavonoid synthesis*, microbial terpene synthase-like genes +, triterpenoids produced by CYP716 enzymes, CYP73 and phenylpropanoid metabolism [development of phenolic network], xyloglucans in primary cell wall, side chains charged; plant poikilohydrous [protoplasm dessication tolerant], ectohydrous [free water outside plant physiologically important]; thalloid, leafy, with single-celled apical meristem, tissues little differentiated, rhizoids +, unicellular; chloroplasts several per cell, pyrenoids 0; centrioles/centrosomes in vegetative cells 0, microtubules with γ-tubulin along their lengths [?here], interphase microtubules form hoop-like system; metaphase spindle anastral, predictive preprophase band + [with microtubules and F-actin; where new cell wall will form], phragmoplast + [cell wall deposition centrifugal, from around the anaphase spindle], plasmodesmata +; antheridia and archegonia +, jacketed*, surficial; blepharoplast +, centrioles develop de novo, bicentriole pair coaxial, separate at midpoint, centrioles rotate, associated with basal bodies of cilia, multilayered structure + [4 layers: L1, L4, tubules; L2, L3, short vertical lamellae] (0), spline + [tubules from L1 encircling spermatid], basal body 200-250 nm long, associated with amorphous electron-dense material, microtubules in basal end lacking symmetry, stellate array of filaments in transition zone extended, axonemal cap 0 [microtubules disorganized at apex of cilium]; male gametes [spermatozoids] with a left-handed coil, cilia 2, lateral, asymmetrical; oogamy; sporophyte +*, multicellular, growth 3-dimensional*, cuticle +*, plane of first cell division transverse [with respect to long axis of archegonium/embryo sac], sporangium and upper part of seta developing from epibasal cell [towards the archegonial neck, exoscopic], with at least transient apical cell [?level], initially surrounded by and dependent on gametophyte, placental transfer cells +, in both sporophyte and gametophyte, wall ingrowths develop early; suspensor/foot +, cells at foot tip somewhat haustorial; sporangium +, single, terminal, dehiscence longitudinal; meiosis sporic, monoplastidic, MTOC [= MicroTubule Organizing Centre] associated with plastid, sporocytes 4-lobed, cytokinesis simultaneous, preceding nuclear division, quadripolar microtubule system +; wall development both centripetal and centrifugal, 1000 spores/sporangium, sporopollenin in the spore wall* laid down in association with trilamellar layers [white-line centred lamellae; tripartite lamellae]; plastid transmission maternal; nuclear genome [1C] <1.4 pg, main telomere sequence motif TTTAGGG, KNOX1 and KNOX2 [duplication] and LEAFY genes present, ethylene involved in cell elongation; chloroplast genome with close association between trnL_UAA and trnF_GAA genes [precursors for starch synthesis], tufA, minD, minE genes moved to nucleus; mitochondrial trnS(gcu) and trnN(guu) genes +.

Many of the bolded characters in the characterization above are apomorphies of more or less inclusive clades of streptophytes along the lineage leading to the embryophytes, not apomorphies of crown-group embryophytes per se.

All groups below are crown groups, nearly all are extant. Characters mentioned are those of the immediate common ancestor of the group, [] contains explanatory material, () features common in clade, exact status unclear.

POLYSPORANGIOPHYTA†

Sporophyte well developed, branched, branching dichotomous, potentially indeterminate; hydroids +; stomata on stem; sporangia several, terminal; spore walls not multilamellate [?here].

II. TRACHEOPHYTA / VASCULAR PLANTS

Sporophyte long lived, cells polyplastidic, photosynthetic red light response, stomata open in response to blue light; plant homoiohydrous [water content of protoplasm relatively stable]; control of leaf hydration passive; plant endohydrous [physiologically important free water inside plant]; PIN[auxin efflux facilitators]-mediated polar auxin transport; (condensed or nonhydrolyzable tannins/proanthocyanidins +); borate cross-linked rhamnogalactan II, xyloglucans with side chains uncharged [?level], in secondary walls of vascular and mechanical tissue; lignins +; roots +, often ≤1 mm across, root hairs and root cap +; stem apex multicellular [several apical initials, no tunica], with cytohistochemical zonation, plasmodesmata formation based on cell lineage; vascular development acropetal, tracheids +, in both protoxylem and metaxylem, G- and S-types; sieve cells + [nucleus degenerating]; endodermis +; stomata numerous, involved in gas exchange; leaves +, vascularized, spirally arranged, blades with mean venation density ca 1.8 mm/mm² [to 5 mm/mm²], all epidermal cells with chloroplasts; sporangia in strobili, sporangia adaxial, columella 0; tapetum glandular; sporophyte-gametophyte junction lacking dead gametophytic cells, mucilage, ?position of transfer cells; MTOCs not associated with plastids, basal body 350-550 nm long, stellate array in transition region initially joining microtubule triplets; archegonia embedded/sunken [only neck protruding]; embryo suspensor +, shoot apex developing away from micropyle/archegonial neck [from hypobasal cell, endoscopic], root lateral with respect to the longitudinal axis of the embryo [plant homorhizic].

[MONILOPHYTA + LIGNOPHYTA]

Sporophyte growth ± monopodial, branching spiral; roots endomycorrhizal [with Glomeromycota], lateral roots +, endogenous; G-type tracheids +, with scalariform-bordered pits; leaves with apical/marginal growth, venation development basipetal, growth determinate; sporangium dehiscence by a single longitudinal slit; cells polyplastidic, MTOCs diffuse, perinuclear, migratory; blepharoplasts +, paired, with electron-dense material, centrioles on periphery, male gametes multiciliate; nuclear genome [1C] 7.6-10 pg [mode]; chloroplast long single copy ca 30kb inversion [from psbM to ycf2]; mitochondrion with loss of 4 genes, absence of numerous group II introns; LITTLE ZIPPER proteins.

LIGNOPHYTA†

Sporophyte woody; stem branching axillary, buds exogenous; lateral root origin from the pericycle; cork cambium + [producing cork abaxially], vascular cambium bifacial [producing phloem abaxially and xylem adaxially].

SEED PLANTS† / SPERMATOPHYTA†

Growth of plant bipolar [plumule/stem and radicle/root independent, roots positively geotropic]; plants heterosporous; megasporangium surrounded by cupule [i.e. = unitegmic ovule, cupule = integument]; pollen lands on ovule; megaspore germination endosporic, female gametophyte initially retained on the plant, free-nuclear/syncytial to start with, walls then coming to surround the individual nuclei, process proceeding centripetally.

EXTANT SEED PLANTS

Plant evergreen; nicotinic acid metabolised to trigonelline, (cyanogenesis via tyrosine pathway); microbial terpene synthase-like genes 0; primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignin chains started by monolignol dimerization [resinols common], particularly with guaiacyl and p-hydroxyphenyl [G + H] units [sinapyl units uncommon, no Maüle reaction]; roots often ≥1 mm across, stele diarch to pentarch, xylem and phloem originating on alternating radii, cork cambium deep seated, gravitropism response fast; stem apical meristem complex [with quiescent centre, etc.], plasmodesma density in SAM 1.6-6.2[mean]/μm² [interface-specific plasmodesmatal network]; eustele +, protoxylem endarch, endodermis 0; wood homoxylous, tracheids and rays alone, tracheid/tracheid pits circular, bordered; mature sieve tube/cell lacking functioning nucleus, sieve tube plastids with starch grains; phloem fibres +; cork cambium superficial; leaf nodes 1:1, a single trace leaving the vascular sympodium; leaf vascular bundles amphicribral; guard cells the only epidermal cells with chloroplasts, stomatal pore with active opening in response to leaf hydration, control by abscisic acid, metabolic regulation of water use efficiency, etc.; branching by axillary buds, exogenous; prophylls two, lateral; leaves with petiole and lamina, development basipetal, lamina simple; sporangia borne on sporophylls; spores not dormant; microsporophylls aggregated in indeterminate cones/strobili; grains monosulcate, aperture in ana- position [distal], primexine + [involved in exine pattern formation with deposition of sporopollenin from tapetum there], exine and intine homogeneous, exine alveolar/honeycomb; ovules with parietal tissue [= crassinucellate], megaspore tetrad linear, functional megaspore single, chalazal, sporopollenin 0; gametophyte ± wholly dependent on sporophyte, development initially endosporic [apical cell 0, rhizoids 0, etc.]; male gametophyte with tube developing from distal end of grain, male gametes two, developing after pollination, with cell walls; embryo cellular ab initio, suspensor short-minute, embryonic axis straight [shoot and root at opposite ends], primary root/radicle produces taproot [= allorhizic], cotyledons 2; embryo ± dormant; chloroplast ycf2 gene in inverted repeat, trans splicing of five mitochondrial group II introns, rpl6 gene absent; ??whole nuclear genome duplication [ζ/zeta duplication event], 2C genome size (0.71-)1.99(-5.49) pg, two copies of LEAFY gene, PHY gene duplications [three - [BP [A/N + C/O]] - copies], 5.8S and 5S rDNA in separate clusters.

IID. ANGIOSPERMAE / MAGNOLIOPHYTA

Lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, apigenin and/or luteolin scattered, [cyanogenesis in ANA grade?], lignin also with syringyl units common [G + S lignin, positive Maüle reaction - syringyl:guaiacyl ratio more than 2-2.5:1], hemicelluloses as xyloglucans; root cap meristem closed (open); pith relatively inconspicuous, lateral roots initiated immediately to the side of [when diarch] or opposite xylem poles; epidermis probably originating from inner layer of root cap, trichoblasts [differentiated root hair-forming cells] 0, hypodermis suberised and with Casparian strip [= exodermis]; shoot apex with tunica-corpus construction, tunica 2-layered; starch grains simple; primary cell wall mostly with pectic polysaccharides, poor in mannans; tracheid:tracheid [end wall] plates with scalariform pitting, multiseriate rays +, wood parenchyma +; sieve tubes enucleate, sieve plates with pores (0.1-)0.5-10< µm across, cytoplasm with P-proteins, not occluding pores of plate, companion cell and sieve tube from same mother cell; ?phloem loading/sugar transport; nodes 1:?; dark reversal P_fr → P_r; protoplasm dessication tolerant [plant poikilohydric]; stomata randomly oriented, brachyparacytic [ends of subsidiary cells ± level with ends of guard cells], outer stomatal ledges producing vestibule, reduction in stomatal conductance with increasing CO₂ concentration; lamina formed from the primordial leaf apex, margins toothed, development of venation acropetal, overall growth ± diffuse, secondary veins pinnate, fine venation hierarchical-reticulate, (1.7-)4.1(-5.7) mm/mm², vein endings free; flowers perfect, pedicellate, ± haplomorphic, protogynous; parts free, numbers variable, development centripetal; P = T, petal-like, each with a single trace, outer members not sharply differentiated from the others, not enclosing the floral bud; A many, filament not sharply distinguished from anther, stout, broad, with a single trace, anther introrse, tetrasporangiate, sporangia in two groups of two [dithecal], each theca dehiscing longitudinally by a common slit, ± embedded in the filament, walls with at least outer secondary parietal cells dividing, endothecium +, cells elongated at right angles to long axis of anther; tapetal cells binucleate; microspore mother cells in a block, microsporogenesis successive, walls developing by centripetal furrowing; pollen subspherical, tectum continuous or microperforate, ektexine columellate, endexine restricted to the apertural regions, thin, compact, intine in apertural areas thick, orbicules +, pollenkitt +; nectary 0; carpels present, superior, free, several, spiral, ascidiate [postgenital occlusion by secretion], stylulus at most short [shorter than ovary], hollow, cavity not lined by distinct epidermal layer, stigma ± decurrent, carinal, dry; suprastylar extragynoecial compitum +; ovules few [?1]/carpel, marginal, anatropous, bitegmic, micropyle endostomal, outer integument 2-3 cells across, often largely subdermal in origin, inner integument 2-3 cells across, often dermal in origin, parietal tissue 1-3 cells across, nucellar cap?; megasporocyte single, hypodermal, functional megaspore lacking cuticle; female gametophyte lacking chlorophyll, four-celled [one module, egg and polar nuclei sisters]; ovule not increasing in size between pollination and fertilization; pollen grains bicellular at dispersal, germinating in less than 3 hours, siphonogamy, pollen tube unbranched, growing towards the ovule, between cells, growth rate (ca 10-)80-20,000 µm h^-1, tube apex of pectins, wall with callose, lumen with callose plugs, penetration of ovules via micropyle [porogamous], whole process takes ca 18 hours, distance to first ovule 1.1-2.1 mm; male gametophytes tricellular, gametes 2, lacking cell walls, ciliae 0, double fertilization +, ovules aborting unless fertilized; fruit indehiscent, P deciduous; mature seed much larger than fertilized ovule, small [<5 mm long], dry [no sarcotesta], exotestal; endosperm +, ?diploid [one polar nucleus + male gamete], cellular, development heteropolar [first division oblique, micropylar end initially with a single large cell, divisions uniseriate, chalazal cell smaller, divisions in several planes], copious, oily and/or proteinaceous, embryo short [<¼ length of seed]; plastid and mitochondrial transmission maternal; Arabidopsis-type telomeres [(TTTAGGG)_n]; nuclear genome [2C] (0.57-)1.45(-3.71) [1 pg = 10⁹ base pairs], ??whole nuclear genome duplication [ε/epsilon event]; ndhB gene 21 codons enlarged at the 5' end, single copy of LEAFY and RPB2 gene, knox genes extensively duplicated [A1-A4], AP1/FUL gene, palaeo AP3 and PI genes [paralogous B-class genes] +, with "DEAER" motif, SEP3/LOFSEP and three copies of the PHY gene, [PHYB [PHYA + PHYC]]; chloroplast IR expansions, chlB, -L, -N, trnP-GGG genes 0.

[NYMPHAEALES [AUSTROBAILEYALES [MONOCOTS [[CHLORANTHALES + MAGNOLIIDS] [CERATOPHYLLALES + EUDICOTS]]]]]: wood fibres +; axial parenchyma diffuse or diffuse-in-aggregates; pollen monosulcate [anasulcate], tectum reticulate-perforate [here?]; ?genome duplication; "DEAER" motif in AP3 and PI genes lost, gaps in these genes.

[AUSTROBAILEYALES [MONOCOTS [[CHLORANTHALES + MAGNOLIIDS] [CERATOPHYLLALES + EUDICOTS]]]]: phloem loading passive, via symplast, plasmodesmata numerous; vessel elements with scalariform perforation plates in primary xylem; essential oils in specialized cells [lamina and P ± pellucid-punctate]; tension wood + [reaction wood: with gelatinous fibres, G-fibres, on adaxial side of branch/stem junction]; anther wall with outer secondary parietal cell layer dividing; tectum reticulate; nucellar cap + [character lost where in eudicots?]; 12BP [4 amino acids] deletion in P1 gene.

[MONOCOTS [[CHLORANTHALES + MAGNOLIIDS] [CERATOPHYLLALES + EUDICOTS]]] / MESANGIOSPERMAE: benzylisoquinoline alkaloids +; sesquiterpene synthase subfamily a [TPS-a] [?level], polyacetate derived anthraquinones + [?level]; outer epidermal walls of root elongation zone with cellulose fibrils oriented transverse to root axis; P more or less whorled, 3-merous [?here]; pollen tube growth intra-gynoecial; extragynoecial compitum 0; carpels plicate [?here]; embryo sac monosporic [spore chalazal], 8-celled, bipolar [Polygonum type], antipodal cells persisting; endosperm triploid.

[CERATOPHYLLALES + EUDICOTS]: ethereal oils 0 [or next node up]; fruit dry [very labile].

EUDICOTS: (Myricetin +), asarone 0 [unknown in some groups, + in some asterids]; root epidermis derived from root cap [?Buxaceae, etc.]; (vessel elements with simple perforation plates in primary xylem); nodes 3:3; stomata anomocytic; flowers (dimerous), cyclic; protandry common; K/outer P members with three traces, ("C" +, with a single trace); A ?, filaments fairly slender, anthers basifixed; microsporogenesis simultaneous, pollen tricolpate, apertures in pairs at six points of the young tetrad [Fischer's rule], cleavage centripetal, wall with endexine; G with complete postgenital fusion, stylulus/style solid [?here], short [<2 x length of ovary]; seed coat?; palaeotetraploidy event.

[PROTEALES [TROCHODENDRALES [BUXALES + CORE EUDICOTS]]]: (axial/receptacular nectary +).

[TROCHODENDRALES [BUXALES + CORE EUDICOTS]]: benzylisoquinoline alkaloids 0; euAP3 + TM6 genes [duplication of paleoAP3 gene: B class], mitochondrial rps2 gene lost.

[BUXALES + CORE EUDICOTS]: mitochondrial rps11 gene lost.

CORE EUDICOTS / GUNNERIDAE: (ellagic and gallic acids +); leaf margins serrate; compitum + [one position]; micropyle?; γ genome duplication [allopolyploidy, 4x x 2x], x = 3 x 7 = 21, 2C genome size (0.79-)1.05(-1.41) pg, PI-dB motif +; small deletion in the 18S ribosomal DNA common.

[ROSIDS ET AL. + ASTERIDS ET AL.] / PENTAPETALAE / [SANTALALES, CARYOPHYLLALES, SAXIFRAGALES, DILLENIALES, VITALES, ROSIDAE, [BERBERIDOPSIDALES + ASTERIDAE]: root apical meristem closed; (cyanogenesis also via [iso]leucine, valine and phenylalanine pathways); flowers rather stereotyped: 5-merous, parts whorled; P = K + C, K enclosing the flower in bud, with three or more traces, odd K adaxial, C with single trace; A = 2x K/C, in two whorls, alternating, (many, but then usually fasciculate and/or centrifugal); pollen tricolporate; G [(3, 4) 5], when 5 opposite K, whorled, placentation axile, style +, stigma not decurrent, compitum + [one position]; endosperm nuclear/coenocytic; fruit dry, dehiscent, loculicidal [when a capsule]; floral nectaries with CRABSCLAW expression, RNase-based gametophytic incompatibility system present.

Phylogeny. Prior to the seventh version of this site asterids were part of a major polytomy that included rosids, Berberidopsidales, Santalales, and Caryophyllales, but then the order of branching below the asterids seemed to be stabilizing, perhaps with a clade [Berberidopsidales [Santalales [Caryophyllales + Asterids]]] while rosid relationships seemed to be [Saxifragales [Vitales + Rosids]]]. However, recent work suggests a polytomy is indeed probably the best way to visualize relationships around here at present. So for further discussion of relationships at the base of asterids and rosids, see the Pentapetalae node.

[BERBERIDOPSIDALES + ASTERIDAE]: ?

ASTERIDAE / ASTERANAE Takhtajan: nicotinic acid metabolised to its arabinosides; (iridoids +); tension wood decidedly uncommon; C enclosing A and G in bud, (connate [sometimes evident only early in development, petals then appearing to be free]); anthers dorsifixed?; if nectary +, gynoecial; G [2], style single, long; ovules unitegmic, integument thick [5-8 cells across], endothelium +, nucellar epidermis does not persist; exotestal [!: even when a single integument] cells lignified, esp. on anticlinal and/or inner periclinal walls; endosperm cellular.

[CORNALES + ERICALES] / Ericornids: ?

[LAMIIDAE/ASTERID I + CAMPANULIDAE/ASTERID II]] / CORE ASTERIDS / EUASTERIDS / GENTIANIDAE - [parent of Ericales] - Back to Main Tree

Plants woody, evergreen; ellagic acid 0, non-hydrolysable tannins not common; vessel elements long, with scalariform perforation plates; sugar transport in phloem active; inflorescence usu. basically cymose; flowers rather small [8> mm across]; C free or basally connate, valvate, often with median adaxial ridge and inflexed apex ["hooded"]; A = and opposite K or P, free, (basally adnate to C); G [#?]; ovules 2/carpel, apical, pendulous; fruit a drupe, (stone ± flattened, surface ornamented); seed single; duplication of the PI gene. - 15 orders, 75 families, 4,874 genera, 88,698 species.

Note: In all node characterizations, boldface denotes a possible apomorphy, (....) denotes a feature the exact status of which in the clade is uncertain, [....] includes explanatory material; other text lists features found pretty much throughout the clade. Note that the precise node to which many characters, particularly the more cryptic ones, should be assigned is unclear. This is partly because homoplasy is very common, in addition, basic information for all too many characters is very incomplete, frequently coming from taxa well embedded in the clade of interest and so making the position of any putative apomorphy uncertain. Then there are the not-so-trivial issues of how character states are delimited and ancestral states are reconstructed (see above).

Age. K. Bremer et al. (2004a) estimated an age of around 123 Ma for this node, Nylinder et al. (2012: suppl.) an age of 126.2-111.2 Ma, Soltis et al. (2008) ages of 124-106(-85) Ma, and Foster et al. (2016a: q.v. for details) an age of ca 109 My; Bell et al. (2010) suggested ages of (109-)100, 93(-85) Ma and (116-)108, 99(-93) Ma in the supplement, Tank and Olmstead (pers. comm.), Magallón et al. (2015) and Tank et al. (2015: Table S1) ages of around (131.2-)117.1(-102.9), ca 106.7 and 97.2/106.2 Ma respectively, Lemaire et al. (2011b) offered estimates of (125-)114(-101) Ma, (117-)112, 102(-97) Ma is the age in Wikström et al. (2001 and (123-)119(-113) Ma in Wikström et al. (2015), ca 119.5 Ma in C. Zhang et al. (2020). and J. Wang et al. (2020) are in this general ballpark. Rather younger ages are around 96.1 Ma (Naumann et al. 2013), N. Zhang et al. (2012) suggested (96-)83(-68) Ma and Xue et al. (2012) ages of 80.7-78.3 Ma. At ca 130 Ma the age in Z. Wu et al. (2014) is the oldest while C. Zhang et al. (2020: Oncothecaceae + the rest) suggested an age of ca 119.5 Ma.

Evolution: Divergence & Distribution. From fossil evidence Martínez-Millán (2010) suggested a late date of 55-33.9 Ma for diversification of most of the gentianid (= euasterid/asterid I + II/lamiid + campanulid clades) orders, i.e. around the Eocene. This estimate is about half the ages suggested by others, e.g. see Beaulieu et al. (2013) for the ages of the campanulid orders and also the dates immediately above.

In an analysis of floral morphospace in angiosperms, lamiids were found to be significantly different from all other groups, mostly having flowers with sepals and petals, the latter being united, and few stamens and united carpels; campanulids also fit here (c.f. in part Chartier et al. 2014b). The gentianids as a whole are notably speciose, although as is common with such generalizations it is more accurate to say that it is the more or less herbaceous and often florally flashy members of Lamiales, Gentianales, Solanales, Asterales and Apiales that are speciose and have high diversification rates (Magallón & Sanderson 2001; Magallón & Castillo 2009), while Boraginales and Dipsacales are rather smaller and other clades are mostly very small. Overall, then, this is 5 (7) large orders and 17 (19) large families out of 17 and 73 respectively - note that order number in particular is uncertain (as of vii.2022) but may well increase, and there will be more small orders (and this is all very subjective). Although Magallón and Sanderson (2001: c.f. dating) suggested that Asterales have the highest diversification rate, the honour went to Lamiales in Magallón and Castillo (2009), but whatever may be driving diversification, it is likely to be combinations of factors that are acting at different places on the tree rather than single factors. Furthermore, within Asterales, for example, although Asteraceae in particular are very speciose, it may be more accurate to say that it is Asteroideae that are particularly speciose, and in any event clarifications of relationships in Asteraceae (Mandel et al. 2019; Barnadesioideae sister to Calyceraceae?) will affect our ideas of diversification.

Endress (2011a) thought that haplostemony, adnation of stamens to petals, and unitegmic ovules were key innovations somewhere around here, but exactly where the last two features in particular are to be placed is unclear, as is also evident from his own work (Endress & Rapini 2014). Although Gasser and Skinner (2018) also suggested that unitegmic ovules could be placed here, they are provisionally placed at the asterid node, q.v. for a discussion of the character. Stull et al. (2018) also discuss possible apomorphies in this area.

Gentianids do seem rather different from other eudicots. Polyandry is more common in other eudicots, and often is independent of any changes in sepal, petal or carpel number; this has been called secondary or complex polyandry that is associated with features such as complex or ringwall androecial primordia and centrifugal androecial development (e.g. Ronse Decraene & Smets 1992b, 1998c; Endress 2013; Erbar 2010; Ronse De Craene 2016b; Remizowa 2019). The near absence of such kinds of increase in stamen number as well as the absence or primary polyandry (as in the ANA grade, etc.) in the gentianid clade may reflect a change in underlying floral organisation/development in the stem gentianids, reflected in the rather stereotypic (in terms of basic floral construction) flowers so common here.

Patterns of polyandry in the gentianids are indeed rather different from those in more basal clades, polyandry often being associated with anisomery. Along with the increase in stamen number, there are also increases in the numbers of perianth parts and/or carpels, the latter being in a single if somewhat bowed whorl. Thus some species of Plerandra s. str. and Tupidanthus (Araliales-Araliaceae), for example, have a kind of fasciation of the flower, and there are about as many stamens as carpels, with well over 100 of both (e.g. Sokoloff et al. 2007b; Nuraliev et al. 2014, esp. 2019); perhaps there has been an increase in the size of the floral meristem. Some Gentianaceae-Potalieae (Anthocleista and Potalia) and -Chironieae, with up to 24-merous flowers, Lamiaceae-Symphorematoideae (Lamiales), and Codonaceae, Hoplestigma (Cordiaceae) and Lennoa and relatives (Ehretiaceae), all Boraginales, but not immediately related to each other, are other examples. Dialypetalanthus and Theligonum, both Rubiaceae, have more numerous stamens than would be expected, but how their flowers are constructed is unclear, and this is true of the multistaminate flowers of Eucommia (Garryales). Paracryphiaceae (Paracryphiales) also show interesting variation in floral merosity. Outside the gentianids polyandry is achieved in an apparently similar way in Crassulaceae and Conostegia (Melastomataceae), both of which have similar stamen and carpel numbers (see Wanntorp et al. 2011 for this and some other examples), Actinidia, with many carpels in a single whorl and many stamens, and in some core Caryophyllales (Ronse de Craene 2013, see also 2016b). For further discussion of polyandry see Pentapetalae.

A recent analysis of the floral morphospace occupied by members of Ericales (Chartier et al. 2017), which, with Cornales (together, = ericornids), are sister to the gentianids, clarifies the considerable extent of floral variation in the first-mentioned. Although three quarters of Ericales have hermaphroditic flowers with five sepals and five petals, these are plesiomorphic characters (Chartier et al. 2017). Ericales and in particular the small family Lecythidaceae, show considerable androecial variation, somewhat less in the gynoecium and less in the perianth (Chartier et al. 2017). Meristicity varies considerably in Sapotaceae and increases in numbers of all or most parts of the flower are common, however, carpel and stamen number sometimes increase independently of any general changes in merosity (Kümpers et al. 2016). Comparing floral variation in Ericales (and in clades immediately basal to them, although more general analyses like that of Chartier et al. 2017 have not been carried out) with that in gentianids, it is evident that there is a considerable decrease in overall variation in gentianids, despite the fact that they include over seven times as many species as Ericales and there was some positive correlation between species number and general floral diversity in Ericales (Chartier et al. 2017; see also Mander 2016). Overall, rather like Orchidaceae, places in gentianids where there has been much speciation can be localized on the tree and there is indeed extensive floral variation there, but on a rather limited theme.

Ellagic acid is notably uncommon in the gentianids (but see Paracryphiales), although it is scattered throughout the rosid to ericornid part of the tree. This is perhaps to be expected, there being a correlation between woodiness and tannin frequency and a negative correlation between tannin (generalized defence) frequency and alkaloid and other secondary metabolites (specific defence) frequencies (e.g. Feeney 1976; Silvertown & Dodd 1996: given the information in Levin 1976 the correlation of alkaloid presence with other features should be re-examined). No large gentianid family has more than 50% tanniniferous species, only Rubiaceae and Caprifoliaceae, both with many woody members, being well represented (Mole 1993); the tannins involved are non-hydrolysable tannins. Flowers of Emmotum and fruits of Apodytes (Metteniusaceae, see below) are rich in tannins (Endress & Rapini 2014; Potgieter & van Wyk 1994b). Emission of isoprene gas shows a somewhat similar distribution, being known from Ericales, rosids, and also a few monocots and Magnoliales (see Kesselmeier & Staudt 1999; Sharkey et al. 2013: again, sampling). Using indices like the Sporne index and herbaceousness index in the context of variation in features of secondary chemistry, Rocha et al. (2015) found rather low values for Ericales, suggesting that it was "primitive".

The demise of the old Aquifoliaceae and particularly Icacinaceae may allow us to better understand the evolution of the gentianids as a whole. Icacinaceae s.l. make up all or most of four of the five orders at the base of the lamiids and campanulids: Icacinaceae s.l. = Cardiopteridales, Icacinaceae s. str., Metteniusales, Oncothecales (Pennantiaceae, here in Apiales, but see below, were also included); Garryales (the only order with genera that have not been in Icacinaceae) and Aquifoliales, whose circumscriptions, if somewhat surprising in the context of older ideas of relationship, are also in this area. Metteniusales and Icacinales (for their relationships and delimitation, see below) are successively sister to the clade [Garryales + other lamiids] (Stull et al. 2015, 2018). These clades are morphologically very different from the megadiverse gentianid clades, and to the extent that the old Icacinaceae s.l. could be characterised, their characters are turning out to be those of the gentianid node.

These small orders include 10 families, about 59 genera, and 811 species (but 405 of the latter belong to Ilex alone), yet they vary in many anatomical and floral characters classically considered to be of importance in delimiting major groups. Stull et al. (2018) examined the distribution and evolution of several characters in the gentianids in the context of these new relationships. All members of these orders are woody, nearly all have rather small flowers less than 8 mm across, most have fleshy fruits, commonly drupes with quite large seeds, one per loculus and usually only one per fruit (for seed size, see also Moles et al. 2005a). However, there is a dearth of basic knowledge about many potentially critical characters. Gynoecial evolution is particularly perplexing - or perhaps it only seems to be because so little is known about gynoecial development and morphology in this area (but see Endress & Rapini 2014 for the way forward). González and Rudall (2010) speculated that the bicarpelate gynoecium of Lamiales, Gentianales and Solanales was derived from the pseudomonomerous gynoecium of something like Metteniusa. However, carpel number and ovule number and morphology in Icacinaceae s.l. are unclear (see below, some taxa have ovules with parietal tissue and/or are bitegmic, e.g. Endress & Rapini 2014).

Beaulieu et al. (2013b) and Stull et al. (2018) discussed the evolution of plant habit in the old campanulids (inc. Aquifoliales s.l.); woodiness was plesiomorphic. Stull et al. (2018) also suggested that an inferior ovary might be an apomorphy at this node - or the next one up. Aquifoliales aside, note that Metteniusales, Bruniales, Desfontaineales, Escalloniales and Paracryphiales, all campanulids, are all (largely) woody and species-poor, as are basal Apiales. Of course, the clades into which the old Icacinaceae have been placed are also woody, have few species poor, and as we see these are in some reconstructions basal in the lamiids; include Oncothecaceae, and these features then are plesiomorphic in the gentianids as a whole.

There are some interesting correlations, for instance, valvate corolla aestivation and petals with pointed, incurved apices and median adaxial ridges (but not in Oncothecaceae). (A corolla with a similar combination of features is common in Apiaceae/Araliaceae, the valvate sepals of Rhamnaceae also have a longitudinal adaxial ridge, and the valvate petals common in Rubiaceae-Rubioideae at least sometimes are "hooded".) There is much variation in whether or not the corolla is fused - if it is, it is often only rather shortly connate, and anyhow corolla tube development is almost entirely unknown in this group - and whether or not the stamens are adnate to the corolla. Indeed, a strongly connate corolla with the stamens adnate some way up the tube is quite uncommon here, although it is found in a few taxa like Metteniusa (Metteniusaceae) and Leptaulus (Cardiopteridaceae). Gynoecial variation is very poorly understood (Kong et al. 2018).

One set of characters, nodal and wood anatomy, is quite well known thanks to the early work of Bailey and Howard (1941a-d) in particular, while Lens et al. (2008a) have begun to put the variation in a phylogenetic context. Variation of features such as vessel length is included in the characterizations here (see also Lens et al. 2008a: measurements from immature individuals excluded). There are correlations here, too, e.g. unilacunar nodes with simple perforation plates, versus tri- and pentalacunar nodes with scalariform perforation plates (see also Bailey & Howard 1941b). Features like vessel and fibre length also correlate with nodal anatomy, although not in quite such a simple fashion. Lens et al. (2008a) noted that some of these features such as long vessel elements with very scalariform perforation plates are part of up the primitive "Baileyan" wood-anatomical syndrome, although ecological connections are more likely. Icacinaceae from Eocene Wyoming grew in habitats where there was likely to be readily available water, a low chance of frost, and a multistratified forest (Allen et al. 2015), and extant taxa of these clades are mostly quite large-seeded trees or lianes in l.t.r.f. (not the habitat of Garryales, some Aquifoliales).

Lens et al. (2008a) drew attention to similarities in wood anatomy between the Icacinaceae s.l. and other woody clades, including Garryales, noting that the "primitive" wood characters they emphasized in the Icacinaceae s.l. were also to be found in woody families at the base of various campanulid clades. Lens et al. (2008a) mentioned Rousseaceae, sister to Campanulaceae and in turn sister to other Asterales (or sister to all Asterales); Carpodetus, also Rousseaceae, has a corolla superficially similar to that of Icacinaceae. Columelliaceae (Bruniales), Adoxaceae (Dipsacales), most Cornales (and c.f. flowers in Cornus, etc.), and Pennantia (perhaps Apiales-Pennatiaceae; again, c.f. flowers in many Apiales) are also involved. Although Ericaceae were also mentioned, they are deeply embedded in Ericales, but Tetrameristaceae-Tetrameristeae do have flowers similar to those of old Icacinaceae. Moreover, within Lamiales and Apiales in particular there are more or less species-poor basal pectinations made up largely of woody taxa. In Apiales, these plants (including Pennantiaceae) have fleshy and few-seeded fruits, while much of the diversity is in the predominantly herbaceous Apiaceae with small, dry, 2-seeded fruits (see also Nicolas & Plunkett 2014: position of Pennantiaceae not certain). Grubbiales, Escalloniales and Paracryphiales are small and overwhelmingly woody clades.

Phylogenetic reorganization will also affect how we think about floral evolution in the gentianids. The genes involved in the development of monosymmetric flowers in Senecio vulgaris (Asteraceae) are described as being homologous to those in Antirrhinum (Plantaginaceae), but they are regulated and expressed differently, growth in the adaxial part of the corolla being reduced and that in the abaxial part increased, the reverse of the process in Antirrhinum (Garcês et al. 2016). Although monosymmetry may not be a feature of the flowers in the basal clades just mentioned, understanding their floral development is something of a priority.

Ecology & Physiology. Leaf size shows a sharp decrease around here (Cornwell et al. 2014). Cornwell et al. (2008) found that litter decomposition of the forbs that predominate in the gentianids was faster than that of graminoids, and although he did not compare deciduous trees and forbs, breakdown of litter was faster in deciduous trees than in evergreen trees; such differences affect the rate of nutrient cycling.

In both campanulids and lamiids there are many annuals and herbaceous to shrubby perennials. The evolution of the rather short-lived herbaceous habit may be associated with thinner roots, with less biomass committed per length, and the loss of mycorrhizal associations (Ma et al. 2018), potentially far-reaching changes. Haig and Westoby (1991) discuss situations in which small seeds may be at an advantage; see also Igea et al. (2017). Many campanulids and lamiids have very small seeds of 10^-2 grams or less (Moles et al. 2005a; Linkies et al. 2010). Seed coats with a mechanical layer more than a single cell thick are scattered throughout BLAs, but gentianid seed coats are rather different, usually being only one or two cells across (Convolvulaceae are a notable exception). However, plants in the basal clades under discussion have rather larger seeds, and since the fruits of most are drupes, the seed coat is not well developed; large seeds are probably linked to their arborescent habit and predominantly rainforest habitat. For further discussion about seed size, see core lamiids and core campanulids.

The annual habit is quite common in euasterids, the vascular cambium being lost or its activity much reduced. Since this is connected with changes in gene expression and interaction networks, not loss of genes (c.f. monocots), secondary acquisition of woodiness is quite common (Davin et al. 2016; Roodt et al. 2019). There may also be different mechanisms of phloem transport, thus taxa with active phloem loading are particularly common here. Sugars, and sometimes also sugar alcohols, not in particularly high concentration in leaf tissues, are pumped into the phloem via a symplastic pathway by the metabolic activities of the plant, plasmodesmatal connections between the sieve tube and other cells being poorly developed (Rennie & Turgeon 2009; Turgeon 2010b; Fu et al. 2011). This may be associated with herbivore deterrence, the sugars causing dessication of the tissues of the herbivore, and/or cellular debris quickly clogs the sieve pores, sealing the phloem, and/or the plant economizes on sugar production (Turgeon 2010b; Fu et al. 2011). (Woody gentianids have "herbaceous" mechanisms of sugar transport, so the correlation may be phylogenetic and less immediately associated with plant habit.) A somewhat different focus on/classification of transport types suggests that one active transport mechanism, the synthesis and transport of raffinose family oligosaccharides, shows little correlation with plant habit but some correlation with climate, being relatively more common in plants from warmer parts of the world, and also with phylogeny, being restricted to Lamiales in the gentianids (Davidson et al. 2011). However, although the literature on this topic is quite extensive, it is not easy to follow. Thus the classifications of phloem transport types in Gamalei (1989) Davison et al. (2011) and Fu et al. (2011) are somewhat different, some types are still heterogeneous (Fu et al. 2011), and an "intermediate" type figures prominently (e.g. Gamalei 1989; Davidson et al. 2010). Family circumscriptions have also been changing over the last thirty years (e.g. c.f. Gamalei 1991; van Bel & Gamalei 1992; Davidson 2011), so genera should be assigned to their current families before being compared.

Conclusion of the first two sections. Much of the previous discussion is rather anecdotal, and ecological parallelisms must play a role in producing similarities between taxa. However, evolutionary patterns in the asterids as a whole need reappraisal in the light of the dissolution of the old Icacinaceae. All in all, the basal gentianid clades that now include the bulk of the old Icacinaceae are rather different from the other often much more speciose gentianid (campanulid and lamiid) clades; these latter clades include 87,878 of the 88,698 gentianid species. In some respects, including their preferred habitats, these basal clades are more similar to Ericales, rosids, and the like. However, phylogenetic relationships in fact seem to be very much up in the air - see Phylogeny below; if indeed relationships are as suggested in the Kew Tree of Life as of 9.ix.2024 (see below) most of what has just been written is worthless.

Genes & Genomes. For a possible duplication of the PI gene here or in the lamiids, see Viaene et al. (2009), but more detailed sampling is required to fully understand the pattern of duplication and loss of this gene; no duplication was recorded from Ilex. Studies on the duplication of the RPB2 gene show that the I copy persists in most of the lamiids almost alone in the Pentapetalae (see also discussion under Pentapetalae), as well as in Ericales (Oxelman et al. 2004b).

Chemistry, Morphology, etc.. In the following discussion, A = Aquifoliaceae, C = Cardiopteridaceae, I = Icacinaceae s. str., M = Metteniusaceae, O = Oncothecaceae and S = Stemonuraceae.

Variation in stamen morphology - number of thecae, their dehiscence, presence/absence of enothecium - is particularly noticeable in Metteniusales (D. R. Kong et al. 2022).

There are two ovules in the gynoecia of most Icacinaceae s.l., and it is commonly assumed that they are in a single carpel. Thus Fagerlind (1945) and Mauritzon (1936c) describe those Icacinaceae s.l. that they examined (S, C) as having a single fertile carpel with two ovules/carpel. However, González and Rudall (2010) described a single ovule developing in each of two small abaxial carpels in the five-carpelate Metteniusa (M). Since there are no septae, this is a form of parietal placentation, and given the findings of Endress and Rapini (2014) in Emmotum (M), this gynoecial morphology should be confirmed. Emmotum has three fertile carpels, each with 1-2 ovules, and these carpels seem to be the three abaxial members of a basically 5-carpelate flower (Endress & Rapini 2014). Poraqueiba (M) initially has three locules, but two are obliterated. Scattered throughout the old Icacinaceae are taxa with styles that are not terminal (Casimirella - I; this can have three styles), or the styles are asymmetric (Cardiopteris - C), or the single style has two bumps/reduced styles at the base (Raphiostylis - M; Citronella - C; Mappia - I). Indeed, sometimes the styles might better be called styluli, each coming from a single carpel (see González & Rudall 2010). Apodytes (M) appears to have two connate styles, while Sleumer (1971) described the style of Nothapodytes (I) as being dimorphic. Finally, Apodytes (M) and a group of genera including Medusanthera (S) have a very asymmetric ovary (see below).

Ovule morphology is little known, as is confirmed by the unexpected finding that the ovules of Emmotum and Pittosporopsis (M) are bitegmic (see González & Rudall 2010; D. R. Kong et al. 2022), Cassinopsis (M) and Phytocrene (I) are apically bitegmic, while the ategmic nature of the ovules of Cardiopteris (C: Kong et al. 2002, 2014; Kong & Schori 2014) seems to be the least of their oddities. Ovules may have parietal tissue or lack it, i.e. be crassinucellate or tenuinucellate, and there has been some discussion as to whether having a thin nucellus meant that the ovules were effectively tenuinucellate (e.g. Mauritzon 1936c; Fagerlind 1945a). Hardly surprisingly, the two ovules in Pittosporopsis differ substantially in morphology, but what is odd/unique is that some 9 vascular bundles occur in the raphe of the fertile ovule of Pittosporopsis (M) (Kong et al. 2022).

Fruits in general are single-seeded and drupaceous, although details of their morphology, sometimes rather complex, are poorly known (see Baillon 1874 for a few details). The fruits of Emmotum (M) are sometimes 3-seeded (Sleumer 1942). Although Oncotheca has five fertile carpels, each with two ovules, seed set is poor, there being usually only one, sometimes two or three, seeds per fruit (Dickison 1986). The fruits are often somewhat flattened and/or with a prominent vertical meridional ridge; they may be very asymmetric, as in Apodytes (M: a sterile carpel? - Potgieter & van Wyk 1994), or in Medusandra and relatives (S), but other taxa also have more or less curved fruits and the loculus of the seed sometimes has a large longitudinal inpushing. The testa is ruminate, especially in Pyrenacantha (I) and relatives.

Comparative phytochemical studies on Aquifoliales, Garryales, Metteniusales and Icacinales are much needed.

Phylogeny. Relationships at the base of the lamiid and campanulid clades have long been uncertain. Aquifoliaceae were included in the campanulids by Gustafsson et al. (1996) and B. Bremer (1996). However, the I copy of the duplicated RPB2 gene is retained in most of the lamiids as well as in Aquifoliaceae (other Aquifoliales?), and there is a comparable pattern in the loss of introns 18-23 in the d copy. This might suggest that Aquifoliales belong to the lamiids (Oxelman et al. 2004b). Both Garrya and Eucommia have only the d copy, perhaps a feature of Garryales in particular. Sampling needs to be improved, but optimisation of the persistence/loss of the I copy on the asterid tree will probably be difficult (Oxelman et al. 2004b). Aquifoliaceae also seem to lack the PI duplication of other gentianids (Viaene et al. 2009: no other Aquifoliales examined).

González et al. (2007) found the relationships [[Garryales + Icacinaceae] [Oncothecaceae [Metteniusa + other lamiids]]], but sampling was poor and support very weak. In an analysis of nuclear genes, N. Zhang et al. (2012) found an [Aquifoliales + Garryales] clade sister to the lamiids as did Zeng et al. (2017: also sometimes paraphyletic at base) but relationships here were not the focus of the latter study in particular. In one analysis using 18S/26S nuclear ribosomal data Maia et al. (2014) recovered a topology [Helwingiaceae [Cardiopteridaceae [Aquifoliaceae [Garryales + other lamiids]]]], but with little support; Icacinaceae, etc., were not included. Qiu et al. (2011) found the relationships [[paraphyletic Icacinaceae plus Garryales [Aquifoliaceae + lamiids]] [other campanulids]], although support was again weak. Sun et al. (2014: chloroplast data) found that Ilex and Garrya (the only members of their respective clades examined) switched positions in analyses of mitochondrial genome data, and the two formed a clade sister to the lamiids when nuclear data were examined. Note that several recent analyses (e.g. Sun et al. 2014; Barba-Montoya et al. 2018; H.-T. Li et al. 2019, 2021: all chloroplast data, latter two extensive plastome analyses) place Aquifoliales as sister to all other campanulids, and that was there position here until v.2020. Quite recently Stull et al. (2020) found that a 77-gene plastome analysis yielded the same position in campanulids, but an analysis of 307 nuclear genes placed Aquifoliales in the lamiids, relationships being [Metteniusales [[Garryales + Aquifoliales] [Icacinales + the rest]]]] or in an ASTRAL species tree [Metteniusales [Garryales [Aquifoliales [Icacinales + the rest]]]] - support for some of these relationships could be stronger, however, overall there was support for an [Icacinaceae + core lamiid] clade.

Although Garryales have often been found to be sister to (most of) the rest of the lamiids (e.g. Lens et al. 2008a: maximum parsimony analyses), the composition of any clades immediately basal to them has been unclear. Oncothecaceae have been placed in this area, but neither they nor the other taxa mentioned immediately below linked strongly with the lamiids (e.g. Kårehed 2001, 2002b; for the position of Oncothecaceae, see Cameron 2001, 2003; Olmstead et al. 2000; B. Bremer et al. 2002). Thus B. Bremer (2002) found [Oncotheca + Apodytes] and [Cassinopsis, Icacina, Pyrenacantha] clades, but neither was well supported. In a parsimony analysis of combined molecular and morphological data Lens et al. (2008a) found a clade [Oncothecaceae + some ex-Icacinaceae (taxa assigned to Metteniusaceae below, including Cassinopsis)] to be sister (72% bootstrap) to other lamiids, while in a Bayesian analysis this clade was joined by Garryales (but with little support for the enlarged clade); the other lamiids formed a clade with 1.0 p.p. support. Relationships remained unclear in a study that focussed on the large lamiid clades (Refulio-Rodriguez & Olmstead 2014), but sampling here was skimpy. Nazaire et al. (2014: Suppl. Fig. 4A) found that Oncothecaceae, Garryales and Icacinaceae formed a grade at the base of the lamiid clade, but support was weak. H.-T. Li et al. [2021] recovered a clade [Icacinaceae [Metteniusaceae + Oncothecaceae] at the base of the lamiids, but there was almost no support for relationships within that clade; Garryales was the next clade up the tree, but support for that position was poor

Some of the Icacinaceae had already moved. Thus Irvingbaileya and Gomphandra were placed with strong support in Aquifoliales s.l. (D. Soltis et al. 2000), and the group moving there was expanded by Kårehed (2001). Within Aquifoliales, there was strong support for the basic structure [[Cardiopteridaceae + Stemonuraceae] [Ilex [Phyllonoma + Helwingia]]] (Kårehed 2001; only 1 sp. of Ilex included; Lens et al. 2008b; Tank & Olmstead pers. comm.: 3/5 families included; H.-T. Li et al. 2021: plastome analyses). Cardiopteridaceae and Stemonuraceae are both very largely populated by ex-icacinaceous genera. Although a grouping [Cardiopteridaceae + Pentaphylacaceae] had weak support in an earlier single gene analysis (Savolainen et al. 2000b), the latter family is generally included in Ericales, as it is here.

Resolving the relationships of the genera that used to be in Icacinaceae has turned out to be critical. Pyrenacantha, Chlamydocarya, Sarcostigma, Iodes, and Icacina (here all Icacinaceae) formed a clade in the rbcL tree of Savolainen et al. (2000b), although placed (but with very little support) at the base of the rosids; these genera belong to Icacinaceae group III of Bailey and Howard (1941). There was initially only weak support for Icacinaceae in this position (D. Soltis et al. 2000), but Kårehed (2001) identified four ex-Icacinaceous groups associated with Garryales: Icacinaceae, and the Cassinopsis, Emmotum and Apodytes groups (here all Metteniusaceae: see also B. Bremer et al. 2002: 4 genera included). The Bayesian analysis of Soltis et al. (2007) recovered Icacina as sister to all other lamiid taxa included (0.99 pp), while Soltis et al. (2011) found very weak support for an association of Icacina with Garryales, but Oncotheca was not a member of this clade, although support for its position (the whole lot formed a paraphyletic assemblage at the base of the lamiids) was very weak. Icacinaceae s. str., strongly supported as being monophyletic, were consistently sister to a [Boraginales, Gentianales, Lamiales, Solanales] clade, but with appreciable support only when morphological data were added to the molecular data (Lens et al. 2008a). Icacina does not link with Garryales in the tree recovered by Bell et al. (2010), but joins the lamiid backbone at a node above. H.-T. Li et al. (2019, 2021) recovered strongly supported [Lamiid + Campanulid] and [Boraginales, Gentianales, Lamiales, Solanales] clades, but support of the two nodes immediately below the latter clade was weak (see also below). Relationships in Z.-D. Chu et al. (2016: Chinese taxa only) are [Metteniusaceae [[Icacinaceae + Garryaceae] [other lamiids]]], and although an extended Garryales that also included both Icacinaceae and Oncothecaceae was recovered by Luna et al. (2019) as the basal branch in the lamiids, the clade had little support, but relationships in this area were not the focus of their study.

In morphological phylogenetic analyses Metteniusa fitted quite comfortably into Cardiopteridaceae, ex Icacinaceae (Kårehed 2001), in Cardiopteridales and sister to all other lamiids. Petiole anatomy, carpel number, etc., of Metteniusa are similar to those of Oncothecaceae (Icacinales here prior to v.2020) in particular (González & Rudall 2007, esp. 2010; González et al. 2007), placed sister to other gentianids. In an analysis of chloroplast genomes with very good generic-level sampling, Stull et al. (2015) found two major clades. One included the well supported Apodytes, Emmotum and Calatola groups (= Metteniusales here); the distinctive Metteniusa itself is well embedded in the second group and is perhaps sister to Ottoschulzia. The other clade had the structure [Oncotheca [Cassinopsis + Icacinaceae s. str.]] that were all included in Icacinales here until x.2020), when the three ended up in separate orders. However, both Oncotheca and Cassinopsis moved in the nuclear analyses of Stull et al. (2020); Cassinopsis is sister to Metteniusaceae, and that seems a reasonable position for it. Perhaps more importantly Oncothecaceae moved immediately outside and sister to the entire campanulid clade - support was slight in the RAxML analysis although strong in the ASTRAL analyses - furthermore, 44 genes were concordant with this position, none in conflict, the others were uninformative.

Angulo et al. (2013) recovered a well supported Icacinaceae s. str., but relationships between the seven genera of ex-Icacinaceae in the study (Metteniusa was not included) and the position of Garryaceae varied in the analyses of ndhF and ndhF plus morphological data. Byng et al. (2014) found four clades, Icacinaceae s. str. and the Apodytes, Emmotum and Calatola groups, Cassinopsis was by itself, and relationships between all five were unclear. There was some Bayesian support for the grouping [Cassinopsis + Icacinaceae s. str.], and there was weak support for a clade [Oncotheca + the Apodytes group]. Just looking at Chinese taxa, Z.-D. Chen et al. (2016) recovered a very poorly supported grouping [Metteniusaceae [[Icacinaceae + Garryaceae] other lamiids]], and other odd groupings continued to appear, as in Barba-Montoya et al. (2018), although relationships in these groups were not the focus of their study.

Overall, relationships at the base of lamiids at the end of 2020 could be summarized as [Cardiopteridales [Garryales, Aquifoliales [Icacinales ...]]]. However, W. J. Baker et al. (2021a: see Seed Plant Tree) in their preliminary analysis of Angiosperms353 nuclear data found the relationships [Cardiopteridales [Aquifoliales [Hydroleaceae (ex Solanales) [Garryales [Icacinales [Montiniaceae (ex Solanales) [Vahliales ...]]]]]]] (ranks of these names changed to fit in with the discussion here), and with quite strong support except for the position of Vahliales. In the much extended i.2022 tree - but again, a preliminary analysis - relationships are [Cardiopteridales [[Garryales + Aquifoliales] [Icacinales [Hydroleaceae* [[Vahliales [Sphenocleaceae* + Lamiales]] [Boraginales [Montiniaceae* [Solanaceae* + Convolvulaceae*]]]]]]]] (asterisks - families that used to be Solanales, which had broken up here). And in the version of 9.ix.2024 we find [Oncotheca balansae (but no support) [O. humboldtiana [[Metteniusaceae [Garryaceae + Aquifoliaceae]] [Cardiopteridaceae + Stemonuraceae]]] as all basal in the campanulids; Bruniales were also in this area, but with weak support, and there was also a clade [Pennantiaceae [Dipsacales [Escalloniaceae + Paracryphiaceae]]]. [Icacinaceae [Hydroleaceae ...]] were basal in the lamiids. Specifically, there was a clade [O. humboldtiana [Metteniusa [Cassinopsis [Apodytes + Platea]]]], i.e. Metteniusaceae, then a [Garryales + Aquifoliales s. str., the other families to be mentioned were also placed in Aquifoliales], then [[Cardiopteris + Gonocaryum] [Citronella + Pseudobotrys]] (Cardiopteridaceae) and finally [[Lasianthera [Discophora [Medusanthera [Cardiocarpus +Grisollea]]]] [[Irvingbaileya [Gastrolepis + Hartleya]] [[Gomphandra [Whitmorea + Stemonurus]]]] (Stemonuraceae, only Cantleya not included) - in general support here was quite good.

Classification. Of the two major clades recovered by Stull et al. (2015) above, the first is recognized as Metteniusaceae-Metteniusales, and the second, made up of Oncothecaceae and Icacinaceae s. str., has been split into Oncothecales and Icacinales s. str., while Cassinopsis and Pittosporopsis, which used to be in Icacinaceae, have moved to Metteniusaceae (they also occur there in the i.2022 Seed Plant Tree). The overall topology at the base of the lamiids was thought to be something like [Cardiopteridales* [Garryales, Aquifoliales [Icacinales* [Gentianales, etc.]] and that at the base of the campanulids is [Metteniusales* [Bruniales [Asterales, etc.]]] - the orders with asterisks include erstwhile Icacinaceae s.l.; for orders and their contents, see also A.P.G. IV (2016) and Stull et al. (2018).

However, relationships suggested by C. Zhang et al. (2020) entailed the recognition of two more orders around here (and one more in the campanulids), the old Icacinaceae being split further. The recognition of Oncothecales seemed likely to H.-T. Li et al. (2021), although there its position was basal in the lamiids [[Icacinaceae [Metteniusaceae + Oncothecaceae]] [[Eucommiaceae + Garryaceae] ...]] while [[Stemonuraceae + Cardiopteridaceae] [Aquifoliaceae [Phyllonomaceae + Hellwingiacaeae]]] formed a clade sister to the campanulids. However, Zuntini et al. (2024) recovered the groups [Metteniusaceae + Oncothecaceae] sister to the campanulids and [[Stemonuraceae + Cardiopteridaceae] [[Icacinaceae [Garryaceae + Eucommiaceae]] [Aquifoliaceae [Phyllonomaceae + Hellwingiaceae]]] ...] at the base of the lamiids - note that the two species of Oncotheca examined in the Generic Tree of Seed Plants version ix.2024 are not immediately related... Indeed, it seems pretty much impossible to do much with higher-level relationships at the base of the lamiids and campanulids, a group of clades moving back and forth between the two; the most that can be said is that the circumscriptions of most families and some orders do seem to be settling down.

Previous Relationships. As will have become evident, many of the genera that until a few years ago made up Icacinaceae are now included in the lamiids, where they make up Icacinaceae s. str. (Icacinales) and Cardiopteridales, and they are also in the campanulids in Apiales as Pennantiaceae and as Metteniusales, and they form grouyps like Oncothecales (see below).

ONCOTHECALES Doweld - Back to Main Tree.

Just the one family, 1 genus, ?2 species.

Age. Wikström et al. (2015: note topology) estimate the age for this clade to be (117-)110(-100) Ma.

Includes: Oncothecaceae

ONCOTHECACEAE Airy Shaw - Oncotheca balansae anc="Oncothecaceae" Baillon - Back to Icacinales

Evergreen trees; chemistry?, tanniniferous cells +; cork cambium outer cortical; vessel elements [460-(868-)1229(-1757) µm long, fibres [820-(1100-)1597(-2080)-2370] µm long; nodes 5:5; petiole bundles arcuate, complex; astrosclereids +; stomatal accessory cells divided; plant glabrous; lamina vernation "convolute", margin with caducous glands, petiole short; inflorescences axillary, cymose, branched; K ± free, quincuncial, C ?imbricate, basally connate; A basally adnate to C, extrorse, anther thecae unisporangiate, tannins in connective, filaments shorter than anthers; pollen 3-colporate, small [10-13 μm long]; nectary?; G [5], opposite C, style +/± styluli, conduplicate, stigma punctate; ovules 2(-1)/carpel, epitropous, campylotropous, integument 4-7 cells across, "crassinucellate", funicle long; fruit not flattened, stone 1-3-seeded; endosperm copious, embryo long, cotyledons short; n = 25, x = ?12 (?9, ?8).

1 [list]/1. New Caledonia.

Evolution: Ecology & Physiology. Oncotheca balansae is a nickel hyperaccumulator (Brooks 1998; Gei et al. 2020).

Chemistry, Morphology, etc.. Measurements of fibre and vessel length above that are in square brackets come from Baas (1975) who provided two sets of non-overlapping measurements for each, but without comment. The stomata, perhaps modified paracytic, are distinctive.

Carpenter and Dickison (1976) described the stamens as being opposite the petals, but drew them as being opposite the sepals; the latter position is more likely (see also Dickison & Bittrich 2016). Oncotheca macrocarpa (McPherson et al. 1981, = O. humboldtiana) has stamens quite unlike those of O. balansae; the incurved, pointed connectives of stamens of the latter are responsible for the generic name. The ventral carpellary bundles of O. macrocarpa are distinct and opposite the loculi, those of O. humboldtiana are fused, separating only towards the top of the ovary and then running in the septal radii (Dickison 1986c).

Additional information is taken from Dickison (1982: anatomy), Lobreau-Callen (1977: pollen), and Carpenter (1975) and Dickison and Bittrich (2016: as Metteniusaceae), both general.

Oncothecaceae are embryologically unknown.

Previous relationships. The family was included in Theales by Cronquist (1981) and Takhtajan (1997), although relationships with Aquifoliaceae had been suggested (see Carpenter & Dickison 1976 for literature).