1. Family: Malvaceae Juss.
    1. Genus: Dombeya Cav.
      1. Dombeya gautieri Dorr & Skema

        This species is accepted, and its native range is NE. Madagascar.

    [KBu]

    Skema, C. & Dorr, L.J. 2010. Dombeya gautieri (Dombeyaceae), a remarkable new species from Madagascar. Kew Bulletin 65: 305. DOI: https://doi.org/10.1007/s12225-010-9212-5

    Habit
    Shrub 2.5 m tall, d.b.h. 2.5 cm in diam
    Stem
    Stems dark reddish-brown, either highly condensed with very short (<2 mm) internodes (brachyblasts) or expanded with longer (>10 mm) internodes, new growth densely stellate-pubescent with long-armed hairs, older growth sparsely stellate-pubescent to glabrescent, the bases of stellate hairs initially persisting as dark papillate-like structures
    Leaves
    Leaves alternate (sometimes appearing whorled on brachyblasts), petioles 2 – 3 mm long, densely stellate-pubescent; leaf blades ovate to narrowly ovate, 3.3 – 5.7 × 2.0 – 2.9 cm, pinnatipartite and appearing “querciform,” margin sinuate, base obtuse to rounded (lowermost lobes unequal, weakly to strongly asymmetric), apex acute to obtuse or rounded, sparingly pubescent above with simple, setose or 2-armed hairs and more densely pubescent on veins with multi-armed stellate hairs, sparingly stellate-pubescent below with multi-armed stellate hairs especially on 1° and 2° veins; pocket domatia below in the form of a fine web-like membrane in the axils of 1° and 2° veins, 1 – 2 mm in length
    Stipules
    Stipules 2 – 3 mm long on expanded shoots, <1 mm long on brachyblasts, briefly triangular at base, subulate above, densely to moderately stellate-pubescent becoming glabrescent
    Inflorescences
    Inflorescences axillary simple cymes, (1 –) 2 – 3-flowered; peduncles less than 1 mm long, pedicels 6 – 10 mm long, densely stellate-pubescent
    Epicalyx
    Epicalyx of 3 bracts directly subtending flower, bracts acicular, 0.5 – 1 mm long, stellate-pubescent
    Flowers
    Flower buds spherical, c.1 × 1 mm, sepals valvate, sepal apices connate
    Calyx
    Calyx 5-parted, fused for less than 1 mm, then free for 2.5 – 3 mm in length, externally heterotrichous with a bed of smaller shorter-armed hairs beneath longer-armed stellate hairs, internally glabrous except for a zone of papillate (probably nectariferous) tissue where the sepals are adpressed to the corolla
    Corolla
    Corolla obovate, strongly asymmetric, 2.5 – 3 × 3.5 – 4 mm, glabrous, white
    Androecium
    Androecium fused into a very short tube, c.0.5 mm tall; stamens 5, free filaments less than 0.5 mm long, anthers basifixed, 0.5 – 1 mm long, connective not prolonged; staminodes 5, petaloid, spathulate narrowing to rounded-acute apices, 3 – 3.5 mm long, white
    Pollen
    Pollen spherical, spiny (visible at 10× magnification)
    Gynoecium
    Gynoecium minute, c.0.25 × 0.5 mm, eusyncarpous, 2-carpellate, with a prominent apical paracarpous zone; septa each including a large mucilage duct; ovules 2 per carpel, with basal-axile placentation, erect, anatropous, apotropous (abaxially curved); style c.0.6 – 0.8 mm long (in bud), deeply divided (bipartite); stigmatic surface not well-demarcated, presumably the interior apical portion of each style branch
    Fruits
    Fruit and seed unknown
    Distribution
    Endemic to Madagascar, where it evidently is restricted to the Solaniampilana-Maroadabo forest northwest of Daraina.
    Ecology
    The type was collected in one of a series of forested massifs situated between the Loky and Manambato rivers in northeast Madagascar. Gautier et al. (2006) describe the whole region as being underlain by Precambrian crystalline rock with a few volcanic intrusions and the Solaniampilana-Maroadabo forest as being a 1726 ha remnant of dry forest (“forêt dense sèche”) at 100 m altitude with a tree canopy 10 – 20 m in height.
    Conservation
    Data Deficient (DD) (IUCN 2001). This species is only known from one collection.
    Note
    etymology. The species is named in honour of the collector of the type and only known material, the Swiss botanist Laurent Gautier (b. 1960). notes. Although Pentapetaceae has priority over Dombeyaceae, the proposal by Doweld & Reveal (2007) to conserve the latter name was recently approved by the Committee for Vascular Plants (Brummitt2009). We assume that this action will be ratified by the General Committee at the next International Botanical Congress and therefore adopt the more widely used family name. A number of characters associated with Dombeya gautieri are remarkable for being either unique or uncommon amongst the Dombeyaceae. Amongst the 20 genera included in the family, only Dombeya as presently construed can accommodate this new species. The pinnatipartite leaves of D. gautieri are striking and otherwise unknown amongst the Dombeyaceae. Indeed, the foliage is so remarkable that we are surprised that D. gautieri has escaped notice until now and suspect it must be quite localised in its distribution. Deeply lobed adult leaves occur in only a few other species of Dombeyaceae and invariably the lobing is palmate. In Madagascar, leaves of D. palmatisectaHochr. are 5 – 9-palmatipartite, those of D. roseifloraArènes are 3 – 5-palmatilobed, and some leaves of the heterophyllous D. urenoidesHochr. (= D. acutangulasensuSeyani) are 5-palmatipartite. In the Mascarene Islands, Ruiziacordata Cav., D. populnea (Cav.) Baker, and D. acutangula Cav. (Friedmann 1987) are heterophyllous and the profound lobing in each species is associated with the juvenile leaves only. This clearly is not the case with D. gautieri and we see no close relationship amongst these genera and species. The abaxial leaf surfaces of Dombeya gautieri have distinctive pocket domatia that consist of web-like flaps of tissue (Figs 1B and 3A). Similar but less well-developed and less conspicuous domatia occur in several African species of Dombeya, notably D. autumnalis I. Verd. and D. cymosaHarv. (Seyani1991). Domatia also occur in most, but not all species of NesogordoniaBaill. (Barnett 1988a), where they consist of tufts of hairs without the web-like flaps of tissue. There is no survey of domatia (either presence or type) within the Dombeyaceae, but we suspect that even if such data existed they likely would not be informative about generic relationships. The androecium of Dombeya gautieri is remarkable in that the fertile stamens are reduced to five in number, each one alternating with a petaloid staminode. Within the genus Dombeya, only D. lokohensisArènes and D. marojejyensisArènes have a similar androecial pattern; five fertile stamens alternating with five staminodes. In both of these species, however, the staminodes are ligulate (not petaloid), the leaves are undivided (not pinnatipartite) and the vestiture is lepidote (not stellate). Five fertile stamens alternating with five petaloid staminodes is characteristic of the related genus MelhaniaForssk., and the small, acicular epicalyx of D. gautieri also is reminiscent of the epicalyx found in Melhania sect. Broteroa (K. Schum.) Arènes. A close relationship with Melhania, however, is ruled out since the ovary in the latter genus is invariably 5-carpellate. In addition, the petals of Melhania are without exception yellow (not white). The petaloid staminodes of Dombeya gautieri (Figs 1F, H and 2) are similar to those of Helmiopsis H. Perrier, a Malagasy endemic, and the colour of the petals (white) is also a shared character (Fig. 2). However, Helmiopsis has 10 – 30 (versus 5) fertile stamens and a 3 – 5-carpellate (versus 2-carpellate) ovary. It would be difficult to accommodate D. gautieri within Helmiopsis without radically recircumscribing the latter genus. The gynoecium of Dombeya gautieri is minute and 2-carpellate (Fig. 3C, D). Among the Dombeyaceae, only species of Dombeya subgen. Xeropetalum and Paradombeyasinensis Dunn also have 2-carpellate gynoecia. (All species of Dombeya subgen. Dombeya and the other two species of ParadombeyaStapf have 5-carpellate gynoecia). Both species of the African genus Harmsia K. Schum. appear to be 2-carpellate, but their gynoecia have a false septum and are in fact unilocular (Jenny et al. 1999). Irrespective of carpel number Paradombeya differs from D. gautieri in usually having 15 (versus 5) fertile stamens, yellow (versus white) petals, and a very briefly divided (versus bipartite) style. Bayer & Kubitzki (2003), presumably based on personal observation, described Paradombeya as having (1 –) 3 (– 5) stamens per bundle. We have not been able to verify that species or specimens of Paradombeya diverge from the general plan of 15 stamens in five bundles. The style of Dombeya gautieri is distinctive; it is 2-parted with each branch free to the base (Fig. 3B). Few species of Dombeya or other genera of Dombeyaceae have style branches that are completely divided. Arènes (1958) described a series Brevicolumnae that includes several species (e.g., D. halapoArènes or D. punctata subsp. ficulnea (Baill.) Arènes) with style branches divided to the base, but all the species in the series are 5-carpellate. The only species of Dombeya that is 2-carpellate and approaches having a completely divided style is D. apikyensisArènes (Arènes1958), which also has undivided leaves and a completely glabrous gynoecium. Friedmann (1987) noted that the style branches of Ruiziacordata Cav. are essentially free (“pratiquementlibres”) and that those of AstiriaroseaLindl. are briefly united at the base (“faiblementsoudés à la base”). One intron and four intergenic spacers of chloroplast DNA of Dombeya gautieri have been sequenced and the results included in an ongoing study of the phylogeny of Dombeyaceae (Skemaunpubl.). These molecular data, beyond placing D. gautieri within a broadly construed Dombeya, are uninformative about the best placement of this species but provide evidence of the need for a reevaluation of generic boundaries in this group. At present, we believe this remarkable new species is best placed in Dombeya.

    Distribution

    Native to:

    Madagascar

    Dombeya gautieri Dorr & Skema appears in other Kew resources:

    First published in Kew Bull. 65: 305 (2010)

    Accepted by

    • Applequist, W.L. (2014). A taxonomic revision of Dombeya sect. Decastemon (Malvaceae) Annals from the Missouri Botanical Garden 99: 553-619. MBG press.

    Literature

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    Sources

    Kew Backbone Distributions
    The International Plant Names Index and World Checklist of Selected Plant Families 2019. Published on the Internet at http://www.ipni.org and http://apps.kew.org/wcsp/
    © Copyright 2017 World Checklist of Selected Plant Families. http://creativecommons.org/licenses/by/3.0

    Kew Bulletin
    Kew Bulletin
    http://creativecommons.org/licenses/by-nc-sa/3.0

    Kew Names and Taxonomic Backbone
    The International Plant Names Index and World Checklist of Selected Plant Families 2019. Published on the Internet at http://www.ipni.org and http://apps.kew.org/wcsp/
    © Copyright 2017 International Plant Names Index and World Checklist of Selected Plant Families. http://creativecommons.org/licenses/by/3.0