Taxonomic notes on the New Zealand flora:×Carpophyma mutabilis and ×Carpophyma pallida (Aizoaceae), new names for two wild intergeneric hybrids

Abstract

New names are provided in ×Carpophyma for two wild intergeneric hybrids between the New Zealand indigenous Disphyma australe subsp. australe and two naturalized species of Carpobrotus. Hybrids between D. australe subsp. australe and Carpobrotus edulis subsp. edulis are named and described as ×Carpophyma mutabilis and hybrids between D. australe subsp. australe and Carpobrotus chilensis are named and described as ×Carpophyma pallida. ×Carpophyma mutabilis is the more common of these hybrids, being known from several localities in the South Island and North Island. ×Carpophyma pallida is known from Canterbury and Chatham Islands. These intergeneric hybrids are robust, vigorously growing plants that are morphologically intermediate between the parents. Furthermore, their pollen is sterile and they do not produce fruit or seeds.

Keywords:

• Aizoaceae
• Disphyma australe subsp. australe
• Carpobrotus edulis subsp. edulis
• Carpobrotus chilensis
• ×Carpophyma
• ×Carpophyma mutabilis
• ×Carpophyma pallida
• intergeneric hybrid
• New Zealand flora

Introduction

New Zealand has two indigenous species of Disphyma, with D. papillatum Chinnock being endemic to Chatham Islands and D. australe (W.T.Aiton) N.E.Br. indigenous to New Zealand (Chinnock 1971; Webb et al. 1988). Disphyma australe is also subdivided into two taxa, with D. australe subsp. stricticaule Chinnock being endemic to the Kermadec Islands and the autonym, D. australe subsp. australe, occurring on North, South, Stewart, and Chatham islands (Chinnock 1976). The Australian Disphyma clavellatum (Haw.) Chinnock occurs in Southland and Otago, and although considered naturalized by Webb et al. (1988) it may have arrived in the area naturally and therefore should perhaps be treated as indigenous (de Lange et al. 2009).

Two naturalized species of Carpobrotus (C. edulis (L.) N.E.Br. and C. chilensis (Molina) N.E.Br.) are conspicuous plants that occur in mainly coastal parts of New Zealand, often in association with D. australe subsp. australe. Chinnock (1972) identified but did not formally name intergeneric hybrids between the naturalized Carpobrotus and the indigenous Disphyma, recognizing two hybrid combinations. The most common of these is D. australe subsp. australe×C. edulis (L.) N.E.Br. subsp. edulis, which is widespread in both the North and South islands. By contrast, the second hybrid combination D. australe subsp. australe×C. chilensis (Molina) N.E.Br. (=C. aequilaterus (Haw.) N.E.Br.) is known from far fewer sites. Chinnock (1972) provided a detailed study of the morphology and cytology of these hybrids. Indeed, his morphometric analyses of 12 vegetative and floral characters clearly demonstrated their hybrid origins and confirmed the parentage, and this was independently supported by the hybrids having a chromosome number of 2n=27 which is intermediate between the putative parents (D. australe, 2n=36; C. edulis and C. chilensis 2n=18). Furthermore, both of these hybrid combinations are completely sterile as the pollen lacks a cytoplasm and they fail to produce seed (Chinnock 1972; PBH & WRS personal observation).

Interspecific hybrids are also known in Carpobrotus. In California (USA), for example, the introduced C. edulis hybridizes with C. chilensis (Albert et al. 1997; Gallagher et al. 1997) to produce fertile hybrid swarms. Hybrids between C. chilensis and C. edulis have not been recorded between these two naturalized species in New Zealand, although these two species often occur together. Recently, Carpobrotus glaucescens (Haw.) Schwantes has also been collected in the wild in North Auckland and, as it is considered to have arrived in New Zealand naturally, should be treated as indigenous (de Lange et al. 2009).

The nomenclature of the two wild intergeneric hybrids in New Zealand is unsatisfactory. Rowley (1980) proposed the intergeneric name ×Carpophyma G.D.Rowley for intergeneric hybrids between Carpobrotus and Disphyma, but he did not provide any interspecific hybrid names. Therefore, the two wild intergeneric hybrids identified by Chinnock (1972) are without formal names. Here we provide two new interspecific hybrid names for intergeneric hybrids between the naturalized Carpobrotus edulis subsp. edulis and C. chilensis and the indigenous Disphyma australe subsp. australe.

Taxonomy

× Carpophyma G.D.Rowley, Name that succulent, 199 (1980)

PARENTAGE: Carpobrotus N.E.Br.×Disphyma N.E.Br.

× Carpophyma mutabilis Heenan & Sykes, nothosp. nov.

Diagnosis: Hybrida intergenerica e Carpobroto eduli subsp. eduli et Disphymato australi subsp. australi, a specie utraque caulibus suis obtuse biangulis, magnitudine foliorum florumque intermedia (foliis usque ad 60 cm longis, floribus usque ad 60 mm diametro), tubo calycis marginibus acute vel subacute biangulis, floribus primo flavis, aetate albidis vel pallidissime roseo-flavis, stylis aurantiacis vel aurantiaco-rubris, inopia pollinis viabilis, et fructu nullo distinguenda.

Holotype: New Zealand, Canterbury Land District, Port Hills, Whitewash Head (above Sumner), near vertical cliff edge above sea, exposed site, with low vegetation, W.R. Sykes 374/98, 26 Oct 1998, CHR 532491.

Description: Stems prostrate, obtusely 2-angled, 4–7 mm in diam., smooth, rooting at nodes; internodes up to 50 mm long. Leaves up to 40–60(–100) mm long, ventral side 4–9 mm wide, green, opposite, triquetrous, connate towards base, clasping stem, margins entire or weakly denticulate near apex, tip acute and often mucronate, dorsal keel well developed. Flowers 40–60 mm in diam. Pedicel 20–40 mm long, subterete to slightly angular, smooth. Calyx-tube obconical, smooth, 10–18 mm in diam. below sepals, acutely or subacutely 2-angled; sepals 5–6, 2 distinctly longer, (10–)15–30 mm long, leaf-like, dorsal keel smooth; 3–4 smaller sepals with whitish membranous margins and a reduced fleshy portion. Petals 3–5-seriate, 10–30 mm long, 2.0–2.6 mm wide towards apex, linear to linear–oblanceolate, shiny; initially pale pink or salmon-pink, ageing deep pink and proximally yellow or initially yellow ageing to whitish or very pale pink–yellow; apex obtuse, bifid or unevenly toothed. Stamens 3–5-seriate, numerous; filaments 4–6 mm long, pale yellow to cream, clad in dense moniliform hairs towards base, except in the outermost row. Anthers 1.0–1.5 mm long, yellow, pollen stainability 0%. Styles 6–10, plumose, subulate, stigmatic to base on adaxial side, orange or orange–red on adaxial side. Ovary 7–11 mm deep, mucilage abundant, top flat or shallowly convex. Nectary ring 1.0–1.5 mm high, green, crenulate. Fruit not developed. Chromosome number 2n=27.

REPRESENTATIVE SPECIMENS: NORTH AUCKLAND: Whangarei Heads, R.J. Chinnock, Sep 1970, CHR 225621. TARANAKI: Paritutu Beach, New Plymouth, M.R. Boase, May 1982, CHR 389616. WELLINGTON: Point Jerningham, Wellington Harbour, R.J. Chinnock, Nov 1969, CHR 225630; Owhiro Bay, Wellington, R.J. C[hinnock], 22 Mar 1969, CHR 226132. CANTERBURY: Gore Bay, W.R. Sykes 541/99, 14 Nov 1999, CHR 568802; Kaituna, Lake Ellesmere, R.J. Chinnock, Dec 1969, CHR 225620; Kaituna, P.J. Garnock-Jones 1767 & E.M. Harnett, 18 Dec 1983, CHR 416035; Diamond Harbour, H.D. Wilson & W.R. Sykes, 1 Oct 1986, CHR 439464; Sumner, W.R. Sykes 240/90, 27 Nov 1990, CHR 473552; Sumner, W.R. Sykes 108/08, 22 Nov 2008, CHR 595934; Banks Peninsula, W.R. Sykes 322/93, 2 Nov 1993, CHR 494018. OTAGO: Oamaru Harbour, A.J. Healy, 54/245, 28 Aug 1955, CHR 91509; Nugget Point, B.H. Macmillan 85/34 & E.W.D. Freeman, 12 Feb 1985, CHR 401318; Otago Peninsula, P.N. Johnson, 11 Oct. 1981, CHR 364129.

DISTRIBUTION: Occurs in coastal areas of the North Island and South Island.

PARENTAGE: Carpobrotus edulis (L.) N.E.Br. subsp. edulis×Disphyma australe (W.T.Aiton) N.E.Br. subsp. australe.

NOTHO-SPECIFIC EPITHET: The epithet mutabilis (changeable) refers to the petal colour of this hybrid as it is variable and changes with age.

× Carpophyma pallida Sykes & Heenan, nothosp. nov.

DIAGNOSIS: Hybrida intergenerica e Carpobroto chilensi et Disphymato australi subsp. australi, a specie utraque caulibus suis obtuse biangulis, magnitudine foliorum florumque intermedia (foliis usque ad 60 cm longis, floribus usque ad 60 mm diametro), tubo calycis marginibus obtuse biangulis, floribus primo pallide roseo-malvinis, aetate purpureo-roseis vel malvino-roseis, stylis aurantiacis, inopia pollinis viabilis, et fructu nullo distinguenda.

HOLOTYPE: New Zealand, Christchurch, end of Linwood Avenue (canal reserve), embankment, J.B. Moss, Oct 1970, CHR 215229.

DESCRIPTION: Stem prostrate, obtusely 2-angled, rooting at nodes, 4–7 mm in diam., smooth. Internodes 20–40 mm long. Leaves up to 40–60 mm long, ventral side 4–8 mm wide, light green, opposite, triquetrous, connate towards base, clasping stem, margins entire or sometimes weakly denticulate near apex, tip acute and often mucronate, dorsal keel well developed. Flower (40–)50–60 mm in diam. Pedicel 10–15 mm long, subterete to slightly angular, smooth. Calyx-tube obconical, smooth, 9–18 mm in diam. below sepals, obtusely 2-angled; sepals 5, 2 distinctly longer, 12–22 mm long, opposite, leaflike, sometimes with minute teeth near apex, 3 smaller ones with whitish membranous margins and a reduced fleshy portion. Petals 3–5-seriate, 15–25 mm long, 1.8–2.6 mm wide towards apex, linear to linear–oblanceolate, initially pink–mauve, ageing to purple–pink to mauve–pink, lower third white; apex obtuse, bifid or unevenly toothed. Stamens 3–5-seriate, numerous; filaments 4–5 mm long, white, clad in dense moniliform hairs towards base, except in the outermost row. Anthers 1.2–1.4 mm long, pale yellow, pollen stainability 0%. Styles 6–10, plumose, subulate, stigmatic to base on adaxial side, orange on adaxial side. Ovary 10–13 mm deep, mucilage abundant, top flat or shallowly convex. Nectary ring 1.5–2.0 mm high, green, crenulate. Fruit not developed. Chromosome number 2n=27.

REPRESENTATIVE SPECIMENS: CANTERBURY: Ferrymead, W.R. Sykes 107/08, 22 Nov 2008, CHR 604293. CHATHAM ISLANDS: Flower Pot, Pitt Island, P.B. Heenan & P.J. de Lange, 28 Nov 2008, CHR 604533.

DISTRIBUTION: Restricted in distribution being known from Pitt Island (Chatham Islands) and Christchurch (Canterbury).

PARENTAGE: Carpobrotus chilensis (Molina) N.E.Br.×Disphyma australe (W.T.Aiton) N.E.Br. subsp. australe. Carpobrotus chilensis appears to be the correct name for New Zealand plants previously referred to C. aequilaterus (e.g. Webb et al. 1988). Carpobrotus aequilaterus has a restricted distribution in Australia and has been misapplied to C. chilensis (Australian Plant Name Index, http://www.anbg.gov.au/apni/ accessed Feb 2009; Toelken 1996). New Zealand plants are considered to be conspecific with those of C. chilensis naturalised in Australia. Carpobrotus chilensis occurs in North and South America, and in California has been considered to be ‘presumably native … appears to be unique to California but is of unknown origin’ (Vilà et al. 1998). However, the native distribution of C. chilensis is uncertain (Schierenbeck et al. 2005), and whether it is indigenous to California or Chile is not resolved (Bicknell & Mackey 1988; Gallagher et al. 1997).

NOTHO-SPECIFIC EPITHET: The epithet pallida (pale) refers to the lighter colour of the petals in comparison to those of C. chilensis.

Recognition

×Carpophyma mutabilis and ×C. pallida are distinguished from their putative parents by a range of vegetative and flower characters, with the most useful diagnostic characters presented in Table 1. The parental species of the intergeneric hybrids differ substantially in size, with D. australe subsp. australe being much smaller in vegetative and flower characters than either C. chilensis or C. edulis subsp. edulis. The two hybrids, ×Carpophyma mutabilis and ×C. pallida, are difficult to tell apart as they have very similar diagnostic characters to each other and both are intermediate between their putative parents. Further difficulties in identification can be encountered with regard to plant vigour, as robust and vigorous growing hybrids can have dimensions similar to either C. edulis subsp. edulis or C. chilensis, and likewise depauperate specimens of the hybrids can have similar dimensions to D. australe subsp. australe. For D. australe subsp. australe, in addition to the small size of its vegetative and floral parts, the terete stems and rounded and/or obscurely angled calyx provide reliable diagnostic characters. Carpobrotus edulis subsp. edulis and C. chilensis are best distinguished by their stems being acutely 2-angled, calyx tube being acutely 2-angled, calyx width, flower diameter, corolla colour, and filament colour (Table 1).

TABLE 1. Characters distinguishing×Carpophyma mutabilis and×C. pallida and their putative parents.

Character	Carpobrotus edulis subsp. edulis	×Carpophyma mutabilis	Disphyma australe subsp. australe	×Carpophyma pallida	Carpobrotus chilensis
Stems	Acutely 2-angled	Obtusely 2-angled	Terete	Obtusely 2-angled	Acutely 2-angled
Leaves: width of ventral side	10–16(–18) mm	(4–)5–8(–9) mm	4–7(–9) mm	(4–)5–6(–8) mm	(5–)10–17 mm
Leaves: maximum length	80–110 mm	40–60(–100) mm	20–40 mm	40–60 mm	85–110 mm
Flower diameter	65–100 mm	40–60 mm	20–42 mm	(40–)50–60 mm	30–60 mm
Calyx: length of longest 2 sepals	25–65 mm	(10–)15–25(–30) mm	7–12 mm	12–22 mm	30–60 mm
Calyx: width of tube apex	25–30 mm	10–18 mm	9–10 mm	9–18 mm	20–30 mm
Calyx tube lateral margin	Acutely 2-angled	Acutely or subacutely 2-angled	Rounded and/or obscurely angled	Obtusely 2-angled	Acutely 2-angled
Corolla colour	Initially light yellow, ageing to pink or pink–orange	Initially pale pink or salmon pink, ageing deep pink and proximal yellow; or initially yellow, ageing to whitish or very pale pink-yellow	Initially pale pink, ageing to pink; sometimes always white	Initially pink–mauve, ageing to purple–pink or mauve–pink, lower third white	Initially and ageing rose or rose-magenta
Petal length	25–40 mm	10–30 mm	10–30 mm	15–25 mm	20–50 mm
Filament colour	Yellow or orange	Pale yellow or cream	White	White	Yellow or orange
Anther colour	Yellow	Yellow	Cream	Pale yellow	Yellow or pale yellow
Style colour on adaxial surface	Green or green–yellow	Orange or orange-red	Yellow–brown	Orange	Green–yellow

×Carpophyma mutabilis and ×C. pallida are best distinguished from their putative parents by stem shape, flower diameter, calyx width, style colour and corolla colour (Table 1). Corolla colour is also the best character to separate these hybrids as the petals of ×C. mutabilis are pale pink or yellow and ageing to paler colours. In comparison, the petals of ×C. pallida are pink–mauve and remain with purple or mauve colours as the flowers age. Otherwise the calyx tube lateral margin being acutely or subacutely 2-angled in ×C. mutabilis and obtusely 2-angled in ×C. pallida seems to be the most reliable diagnostic character separating them.

Acknowledgements

This article is a contribution towards clarifying the taxonomic and nomenclatural status of New Zealand plants for the plant names database (Nga Tipu Aoteoroa – http://nzflora.landcareresearch.co.nz/) and the electronic Flora of New Zealand.

We thank Dr H. Toelken for helpful comments on the taxonomy of Carpobrotus; Clayson Howell and Darren Foxwell for providing plant material; Peter de Lange for discussion; Mark Garland for providing the Latin diagnoses; and David Glenny, Ines Schonberger and Christine Bezar for comments on the draft manuscript. PBH was supported by the New Zealand Foundation for Research, Science and Technology through the Defining New Zealand's Land Biota OBI.