Kunzea amathicola de Lange et Toelken
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|Kunzea amathicola de Lange et Toelken|
Taxon classification Plantae Myrtales Myrtaceae
A K. ericoides habitu heterophyllo, ramulis juvenilibus persistentibus plerumque fores efferentibus, indumento ramulorum persistenti longo sericeo antrorso appresso, indumento foliorum sericeo e vittis marginalibus et costis abaxialibus, inflorescentibus elongatis, bracteis floralibus oblongis vel late obovatis vel ellipticis differt. Etiam ordine rDNA ETS unico in sectione Niviferae recedit.
(Fig. 34). New Zealand, South Island, Puponga Farm Park, Wharariki Beach Road, road end, 40°30'S, 172°41'E, 5 m a.s.l. 'Dominant on sand dunes by roadside. Flowers in extended racemes, one flower per bract’. P. J. de Lange 4954, 10 Jan 2001, AK 286081! Isotypes: AD! BM! CHR! K! NSW!
The specific epithet amathicola meaning 'sand dwelling’, alludes to the mainly sand-dominated habitat preferentially occupied by this species.
(Figs 35, 36, 37, 38).Growth habit Shrubs or trees up to 15 m tall; heterophyllous (bearing distinct juvenile and adult foliage types). Those with persistent juvenile foliage mostly present in exposed conditions and unstable habitats, or at the margins of adult stands, usually forming domed, spreading shrubs up to 2 × 3 m with numerous erect to ascending, often interwoven branches; those with adult foliage forming single to multi-trunked trees up to 18 × 8 m, with very broad, spreading canopies. Irrespective of growth habit, plants flowering at a young age (1-2 years old). Trunk 1(-2) in juveniles usually branched from or close to base, in adults usually devoid of branches in lower 30-50%; 0.10 –0.60(– 0.85) m d.b.h., initially erect but soon arching outwards; basal portion covered with firm to semi-detached, tessellated, short to long, tabular to ± irregularly tabular lengths of corky-coriaceous bark. Bark early bark chartaceous to subcoriaceous, grey or grey-brown, ± elongate, usually bearing a few transverse cracks (especially on branch flanges and decurrent leaf bases) otherwise remaining firmly attached, margins elongate sinuous, ± entire with scarcely any flaking; old bark similar though distinctly corky-coriaceous, usually tessellated, firmly attached, detaching basally with age, and peeling upwards along trunk in broad, tabular strips, margins ± entire to weakly irregular; upper surface often deeply corrugated and cracked but not peeling; margins somewhat sinuous to ± straight; early and old bark flakes firm, not crumbling in hand, snapping with ± entire margin. Branches juvenile branches numerous, erect to suberect not spreading, often interwoven; adult branches usually confined to the upper 30-50% of trunk; initially suberect, soon arching and spreading, often weakly flexuose; branchlets numerous, slender, ± quadrangular to subterete, branchlet indumentum copious, persistent; hairs silky, antrorse-appressed, usually flexuose, (0.23 –)0.38(– 0.50) mm long, hyaline to translucent (appearing white when young, maturing grey). Juvenile branchlets numerous, erect to suberect, often interwoven, leaves ± evenly spaced along length or, in exposed situation, crowded toward apices; adult branchlets clustered toward branch ends, weakly flexuose, with leaves ± evenly spaced along length. Vegetative buds conspicuous; at resting stage 0.8-1.0 mm diam.; scales scarious, deciduous, 0.5-0.8 mm long, amber to red-brown, broadly ovate, ovate-deltoid to rostrate; midrib prominent, strongly keeled in upper half, prolonged to short cuspidate tip, lateral veins absent, oil glands few, scattered, colourless, drying dull yellow; scale margins, keel, and keel apex copiously covered in long, white, silky hairs. Leaves sessile to shortly petiolate, well-spaced to crowded along branchlets, spreading, sub erect to patent, strongly recurved in distal 30-50%, dark glossy green above, much paler beneath with margins and abaxial midrib distinctly white-coloured due to dense hair growth. Juvenile lamina (2.4 –)3.4(– 5.3) × (1.2 –)1.9(– 2.3) mm, ovate, broadly ovate, rhomboid to obovate, adult lamina (6.0 –)8.2(– 12.5) × (1.8 –)2.6(– 3.8) mm, oblong, oblong-obovate, broadly oblanceolate to broadly lanceolate; apex of both juvenile and adult lamina obtuse, rounded to subacute, rostrate, base attenuate to narrowly attenuate; adaxial surface convex, weakly plicate, or strongly v-shaped in distal recurved portion, oil glands not evident when fresh, midrib very slightly raised near base, otherwise not evident for rest of length, basally finely covered in antrorse-appressed, silky hairs, otherwise glabrous; abaxial surface slightly to prominently concave in distal recurved portion otherwise weakly concave, finely glandular punctate, oil glands sparse 80-200, more evident when dry; midrib slightly raised for entire length, prolonged slightly at apex, densely sericeous, hairs continuing to leaf apex, hairs weakly flexuose, antrorse, subappressed, up to 0.3 mm long, hyaline to translucent, appearing as white to naked eye; lamina margin completely obscured by a dense covering of antrorse-appressed hairs aligned in a thick, up to 0.6 mm wide, white, plumose band meeting with abaxial midrib hairs at the leaf apex. Perules deciduous, rarely persistent, squamiform; scales scarious, 0.5-0.8 mm long, amber to red-brown, broadly ovate, ovate-deltoid to rostrate; midrib prominent, strongly keeled in upper half, prolonged to short cuspidate tip, lateral veins absent, oil glands few, scattered, colourless, drying dull yellow, scale margins, keel, and keel apex copiously covered in long, white, silky hairs. Inflorescence Usually a well-spaced, elongate, (5 –)12(– 20)-flowered botryum up to 200 mm long, in adverse conditions sometimes becoming a condensed raceme 30-60 mm long, with the flowers shortly spaced and overlapping; in non-stressed conditions the terminal portion of the inflorescence comprising an indeterminate length of vegetative growth and sometimes a few undeveloped flowers. Inflorescence axis densely invested with silky, antrorse-appressed, weakly flexuose hairs. Pherophylls persistent, foliose, spreading, dark glossy green, oblong, oblong-obovate, broadly obovate to elliptic; strongly recurved, to about half of total length or flat; juvenile lamina (2.0 –)3.4(– 5.3) × (1.2 –)1.9(– 2.3) mm, adult lamina (4.1 –)5.4(– 6.0) × (1.6 –)2.3(– 3.1) mm; apex obtuse, cuspidate, base attenuate; adaxial surface usually convex to weakly plicate, oil glands not evident when fresh or dry, midrib slightly raised near base, otherwise not evident for rest of length, basally covered in a dense weft of antrorse-appressed, silky hairs; abaxial surface flat or weakly convex, glandular punctate, oil glands 20-40, more evident when dry; midrib raised for most of length, densely covered in antrorse-appressed, sericeous hairs to apex, lamina margin obscured by dense covering of antrorse-appressed hairs. Pedicels (1.3 –)3.4(– 4.9) mm long at anthesis, usually elongating slightly after anthesis, terete, sparsely to densely invested in antrorse-appressed, weakly flexuose, silky hairs. Flower buds pyriform to hemispherical, apex usually flat or weakly domed prior to bud burst; calyx valves not meeting. Fresh flowers when fully expanded (6.8 –)11.6(– 12.5) mm diam., usually reducing in size toward end of flowering season. Hypanthium (1.9 –)2.8(– 4.0) × (3.0 –)4.0(– 5.6) mm, with free portion 0.7-1.3 mm long, dark green or red-green, drying green-brown or red-brown; broadly obconic, turbinate to hemispherical, terminating in dark-green to red-green coriaceous rim bearing five persistent suberect to spreading calyx lobes; fresh hypanthium surface faintly ribbed and sparingly dotted with pink or colourless oil glands, these drying dull yellow, ribs and veins usually densely covered in silky, antrorse-appressed hairs, sometimes glabrous; dry hypanthium surface similar though with the ribs more strongly defined, clearly leading up to calyx lobes. Calyx lobes 5(-8), suberect to spreading, coriaceous, (0.6 –)1.2(– 1.4) × (0.6 –)1.0(– 1.8) mm, persistent, ovate, ovate-truncate to broadly obtuse, pale green to red-green, weakly to strong keeled, external face of keel usually obscured by a broad band of antrorse-appressed, silky, white hairs, otherwise glabrous; margins white, pale green often flushed pink, surface somewhat sparsely glandular punctate, oil glands ± colourless when fresh drying dull yellow, otherwise (aside from keel) glabrescent. Receptacle green at anthesis, consistently darkening to crimson after fertilisation. Petals 5(-8), (1.8 –)2.6(– 3.7) × (2.0 –)2.7(– 4.0) mm, white (often drying butter yellow), spreading, orbicular to broadly ovate, apex rounded, margins ± finely and irregularly denticulate or crimped 1-6 or more times, oil glands colourless, drying opaque. Stamens 38 –60(– 90) in 2(-3) weakly defined whorls, arising from receptacular rim, filaments white. Antipetalous stamens 3 –5(– 6) sometimes petaloid, antisepalous stamens (5 –)8(– 10). Outermost antipetalous stamens usually outcurved, sometimes weakly incurved or in mixtures of both on filaments 1.5-2.4 mm long, inner stamens usually at the base of the outermost antipetalous pair (0.6 –)0.8– 1.2 mm long, weakly incurved. Antisepalous stamens mostly shorter than outermost antipetalous stamens, sometimes of comparable length, generally 0.6-1.2 mm long, weakly to strongly incurved, very rarely a few outcurved. Anthers dorsifixed, 0.40-0.60 × 0.20-0.35 mm, ellipsoid, ovoid-ellipsoid or broadly scutiform, latrorse. Pollen white (9.9 –)14.8(– 18.9) μm. Anther connective gland prominent, deep golden-yellow to orange when fresh, drying orange to pink, spheroidal, rather finely papillate, sometimes absent. Ovary 5(-6) locular, each with 23 –28(– 42) ovules in two rows on each placental lobe. Style 2.0 –2.5(– 3.2) mm long at anthesis, elongating slightly after anthesis, white or pinkish-white; stigma broadly capitate, at least 1.5 × width of style, flat, greenish-white or pale pink, flushing red after anthesis, surface finely granular-papillate. Fruits long persistent, (2.4 –)3.9(– 4.8) × (3.6 –)4.8(– 6.0) mm, initially dark green to chesnut-brown fading with age to grey, broadly obconic, turbinate or hemispherical, rarely broadly cupular; veins and ribs conspicuous on drying, these finely hairy to glabrescent, hairs antrorse-appressed; calyx valves incurved, splits concealed by dried, erect, free portion of hypanthium. Seeds 1.2 –1.5(– 1.7) × 0.3 –0.4(– 0.6) mm, testa semi-glossy, orange-brown to dark brown, oblong, oblong-obovate, narrowly ellipsoid to cylindrical, ± curved near apex, laterally compressed, 2-3-angled with convex to flattened faces, apex rounded to subacute; base oblique, ± flattened. Surface coarsely reticulate. FL: ( Jul–)Nov–Jan(– Jun). FT: ( Aug–)Nov–Jan(– Jun). Chromosome Number n = 11II, 2n = 22 (see de Lange and Murray 2004).
(88 sheets seen).North Island. Te Aupouri Peninsula, Hukatere, K. G. Matthews s.n., 30 Aug 2005, (AK 293310); Ahipara, Shipwreck Bay, P. J. de Lange 4144, 17 Jan 2000, (AK 287967, Duplicate: AD); Hokianga, Outer South Head Walkway, P. J. de Lange 5397 & T. T. J. B. Armstrong, (AK 282676); Pouto, near Lake Whakaneke, L. J. Forester s.n., 16 Nov 2000, (AK 252352); Kaipara Harbour, Okahukura Peninsula, Kahutaewao Creek, P. J. de Lange 6709, T. J. de Lange & F. J. T. de Lange, 29 Sep 2006, (AK 297616); Woodhill, Kaipara, W. R. B. Oliver s.n., 26 Dec 1912, (WELT SP029495); Port Waikato, R. Cooper s.n., 13 Feb 1965, (AK 121924); Te Rere Farm Station, Taranaki Bluffs, south of Rengarenga Stream mouth, P. J. de Lange 6882, 7 Feb 2002, (AK 298389); Kawhia Harbour, Puti Point Scenic Reserve, P. J. de Lange 5293, 26 Jun 2001, (AK 254924, Duplicate; AD); Awakino River, near Awakino, P. J. de Lange 6328 & T. T. J. B. Armstrong, 14 Sep 2001, (AK 289178); Horowhenua, Hokio, Hokio Beach Road, P. J. de Lange 4895, 7 Jan 2001, (AK 289230, Duplicate: AD); Kapiti [Island], W. R. B. Oliver s.n., 16 Jan 1935, (WELT SP06700); Pautahanui Inlet, Plimmerton Hills, near Cambourne Walkway, P. J. de Lange 4902, 8 Jan 2001, (AK 289332, Duplicate; AD). South Island. Farewell Spit, Bush End Point, P. J. de Lange 5015 & G. M. Crowcroft, 15 Jan 2001, (AK 289243, Duplicate: AD, MEL); Farewell Spit, Lagoon Creek, P. J. de Lange 5016 & G. M. Crowcroft, 15 Jan 2001, (AK 289691); Puponga Farm Park, Stone Bridge, P. J. de Lange 4973, 11 Jan 2001, (AK 286080, Duplicate: AD); Whanganui Inlet, Kaihoka Lakes, P. J. de Lange 4911, 9 Jan 2001, (AK 286083, Duplicate: CHR); Aorere Inlet, P. J. de Lange 4981, 11 Jan 2001, (AK 289242); Wainui Bay, Takapou inlet, P. J. de Lange 4993, 12 Jan 2001, (AK 289688, Duplicate: AD); Anatori River Mouth, P. J. de Lange 4913, 9 Jan 2001, (AK 289235, Duplicate: AD).
(Fig. 39). Endemic, New Zealand, North and South Islands (sea level - 320 m a.s.l.). In the North Island Kunzea amathicola is found mainly in the west, locally from Unuwhao Bush, Te Paki, south to Wellington City. In the South Island Kunzea amathicola is common in north-west Nelson from Farewell Spit to the Whanganui Inlet, and along the tidal reaches of the Aorere River. South of there it is confined to the Kaihoka–Kahurangi coastline. Kunzea amathicola has also been collected along the eastern side of the Kaipara Harbour where it extends up the main river valleys a considerable distance. This species has also been collected once from Kawau Island (L. Esler s.n., AK 215754) and, from a tidal creek on the Hauraki Plains near Waitakaruru (e.g., R. Mason s.n., CHR 112646).
Kunzea amathicola differs from the other New Zealand Kunzea species by its heterophyllous habit (with different juvenile and adult foliage types and the tendency for apparent juveniles to flower and fruit (Fig. 38B, H)), by the obovate leaves with distinctly hairy leaf margins and midribs (with the hairs meeting at the leaf apex rather than just short of it), and distinctive elongate inflorescences (Figs 35-36, 38; Table 1). Kunzea amathicola usually has a larger flower than the other New Zealand species, and it may also be found in flower throughout the year. Some of these distinctions are shared with Kunzea linearis and Kunzea triregensis , species with which it seems to be morphologically allied. Phylogenetically, Kunzea amathicola is sister to the other New Zealand taxa ( de Lange 2007; de Lange et al. 2010). Indeed, the ITS sequence of Kunzea amathicola differs consistently (based on 15 samples spanning the species’ range) from all other Australian and New Zealand members of the Kunzea ericoides complex by one unique character (in ITS-1), a thiamine nucleotide at alignment position 671 (Table 2; see also de Lange 2007). Otherwise, at ITS-1 alignment position 742, Kunzea amathicola shares with Kunzea salterae and Kunzea tenuicaulis , a guanine/thiamine mix (Table 2). The ETS sequence of Kunzea amathicola has no unique characters. However, it shares a guanine nucleotide at position 68 with the Australian Niviferae subsect. Niviferae ( de Lange 2007) and a single sample of a New Zealand Kunzea of uncertain status from Lottin Point near East Cape (Table 2). It also shares a guanine nucleotide at position 269 with Kunzea sinclairii and Kunzea robusta ( de Lange 2007; de Lange et al. 2010).
Kunzea amathicola is widely sympatric (and often syntopic) with Kunzea ericoides (South Island, north-west Nelson only), Kunzea linearis (northern North Island only) and Kunzea robusta (throughout its range). Hybrids involving these species and Kunzea amathicola are uncommon in sites of sympatry, unless they are from places subjected to frequent disturbance, such as in areas of plantation forestry overlying dune fields, within coastal subdivisions or along roadsides,(see below). Throughout large parts of its range, particularly from the Waitakere coastline north to the northern end of the Pouto Peninsula, Kunzea amathicola is the dominant species of the sand country and associated peripheral hill country. In these areas Kunzea amathicola may exist in sometimes extensive, evidently self-perpetuating forests (see Smale et al. 1995 as Kunzea ericoides var. ericoides ).
Field and herbarium recognition of Kunzea amathicola is straight forward (Table 1). Irrespective of whether plants have juvenile or adult leaves, the species can be recognised by the distinctive obovate to broadly elliptic, yellow-green to dark green leaves which are consistently glossy above and paler beneath, and by the lamina margins and the abaxial (and sometimes adaxial midribs) which are densely covered in white, silky, antrorse-appressed, weakly flexuose hairs, which meet at the leaf apices (Figs 35-36, 38II; Table 1). The leaf shape coupled with the characteristically elongate inflorescences, and broadly obovate to elliptic, persistent, foliose pherophylls are also diagnostic (Fig. 35 A–B). The only other species to have consistently elongate inflorescences is the allopatric Three Kings endemic Kunzea triregensis , which has lanceolate to elliptic pherophylls, and inflorescences that may branch toward the base or near the apices into smaller elongate lateral or more rarely 3-flowered subcorymbiform botrya.
Kunzea amathicola is distinguished from the linear-leaved Kunzea linearis by its leaf shape, heterophyllous growth habit, elongate inflorescences and widely spaced, pedicellate flowers. In examples of Kunzea linearis where the spiciform inflorescence has become elongated, the long-pedicellate condition of Kunzea amathicola is a major distinction from the sessile to subsessile flowers of Kunzea linearis . The flowers of both species also differ, those of Kunzea amathicola have spreading rather than suberect petals, and antipetalous stamens that have markedly longer filaments than those of Kunzea linearis .
Kunzea amathicola is distinguished from Kunzea robusta by its leaf shape and indumentum and by the consistently elongate botryum. Although Kunzea robusta is an extremely variable species, its leaves are rarely obovate, being mostly oblanceolate to lanceolate or linear-lanceolate, and, although some populations (e.g., the upper Rangitikei Valley and Mt Egmont - eastern Taranaki area) are markedly heterophyllous, none have the small obovate leaves of juvenile Kunzea amathicola plants. While the leaf margins of Kunzea robusta are usually hairy, the hairs are aligned in 1 –2(– 3) irregular rows, rather than the thick band of plumose hairs seen in Kunzea amathicola , and they never meet at the leaf apex. Further, as the leaves of Kunzea robusta mature, these marginal hairs are progressively shed so that in most cases they are present only in the lower one-third of the leaf. The inflorescence of Kunzea robusta is also mostly corymbiform, though in good flowering years or shade plants these corymbiform botrya usually partially elongate but never to the extent seen in Kunzea amathicola . Corymbiform botrya are never seen in Kunzea amathicola , and, although occasional plants may have shorter more ‘condensed’ inflorescences than is usual for this species, the flowers are always subtended by a persistent leaf-like, narrowly to broadly obovate pherophyll. The pherophylls of Kunzea robusta , are both squamiform and foliose (Table 1), with foliose ones mostly oblanceolate, broadly lanceolate to lanceolate, rather than mostly oblong, oblong-obovate, to elliptic (only rarely broadly lanceolate, as in Kunzea amathicola ), and they are mostly shed during the early stages of flowering. Ecologically Kunzea robusta is a widely ranging species found from the coast through to montane areas, while Kunzea amathicola is mostly confined to coastal areas. Finally, Kunzea robusta is usually a tall forest tree commonly exceeding 20 m tall whereas Kunzea amathicola is a smaller tree or shrub rarely exceeding 12 m tall.
In the north-west Nelson part of its range, Kunzea amathicola is the only Kunzea species present from the tip of Farewell Spit to the northern end of the Whanganui inlet across to about Pakawau. South of there it is sympatric with Kunzea ericoides . While both species show some ecological partitioning, the hybrid Kunzea amathicola × Kunzea ericoides is common in more disturbed places where logging and past fires have significantly disrupted the vegetation (such as along roadsides, within coastal subdivisions, and along the north-eastern parts of the Whanganui Inlet). Distinction between Kunzea ericoides and Kunzea amathicola is straightforward (Table 1). Both species have markedly different branchlet indumentum. That of Kunzea amathicola is long, silky, antrorse-appressed and clearly visible to the naked eye, while Kunzea ericoides tends to be glabrate, the divergent hairs are minute and scarcely distinguishable without a 20 × magnification lens. Kunzea ericoides is homophyllous; it has linear to linear-lanceolate, glabrate leaves, glabrate to glabrous obconic hypanthia, and much smaller flowers (up to 16 mm diameter) than Kunzea amathicola , with consistently fewer stamens (up to 34, usually 18). Kunzea amathicola is heterophyllous; it has obovate to elliptic, hairy leaves, and very hairy obconic hypanthia. The flowers of this species are much larger (up to 20 mm diameter) and in the field they have consistently more stamens (usually more than 40 and up to 80, rather than mostly 18 rarely up to 34).
Kunzea amathicola is primarily a coastal species of mobile sand and, usually Pleistocene-aged, stable sand dune systems. In the south-western North Island and north-western South Island, however, it also colonises greywacke soils, calcareous rocks, coal measures and their associated clay soils (Fig. 38 A–B). It also colonises tidal river banks, coastal freshwater wetlands, estuaries (where it usually grows in the upper reaches of salt marshes with species such as Olearia solandri (Hook.f.) Hook.f. and Plagianthus divaricatus J.R.Forst. et G.Forst.), and may be prominent on exposed coastal headlands, cliff faces, and slip scars. More rarely it extends inland along river valleys where it colonises alluvial terraces. It reaches its maximum altitudinal limit on the windswept gumland scrub of the Ahipara Plateau where it has spread from the adjoining sand country up on to the figau. This habitat is probably more induced than truly natural, because at this location Kunzea amathicola is occupying ground that was once covered in kauri forest and which was burned repeatedly from the mid 1800s to early 1900s to facilitate better access for gum diggers ( Sale 1978).
Kunzea amathicola is often the dominant tree species of dune systems in the western part of the North and northern South Island, where it appears routinely to form a distinct, stable vegetation type. Kunzea amathicola is well adapted for the sand environment. Plants grow quickly to form a dense ball of branchlets with no obviously dominant stem. Plants bearing juvenile foliage and flowers and fruits have been collected on mobile sand, on exposed coastal headlands, or even as part of the shrub tier under adult stands of the same species (e.g., P. J. de Lange 4341 & A. J. Townsend (AK 289328)).
Kunzea amathicola is sometimes parasitised by the green mistletoe ( Ileostylus micranthus (Hook.f.) Tiegh.), dwarf mistletoe ( Korthalsella salicornioides ) and both species of taihoa ( Cassytha paniculata and Cassytha pubescens ).
Recognition of Kunzea amathicola × Kunzea ericoides and Kunzea amathicola × Kunzea linearis in the field or herbarium is easy because both Kunzea ericoides and Kunzea linearis have linear, linear-lanceolate to narrowly lanceolate leaves and the leaves of hybrids are intermediate between those species and Kunzea amathicola . Further, because Kunzea ericoides has glabrescent branchlets usually sparingly covered in divergent hairs, hybrids with the distinctly hairy Kunzea amathicola , whose branchlets are copiously covered in long, silky, antrorse-appressed hairs, are easily recognised by the obvious mixtures of both hair types on the branchlets. Also, the elongate inflorescences of Kunzea amathicola are carried through in the hybrid such that plants have mixtures of subcorymbiform to completely elongate botrya. The leaf margins of Kunzea amathicola × Kunzea ericoides are also distinctive, typically rather hairy at first but with the hairs soon shedding, and rarely (if ever) meeting at the leaf apex. Foliage colour in hybrids also tends to retain the bright green typical of Kunzea ericoides , rather than the glossy dark green more usual for Kunzea amathicola . Kunzea amathicola × Kunzea ericoides is common around the more modified parts of the South Island at Golden Bay and the northern Whanganui Inlet. In particular there are complex introgressed swarms around Waikato, (to the north of the Aorere Lagoon, north-west Nelson), and between Pakawau and the north eastern reaches of the Whanganui Inlet. Otherwise, this hybrid is rarely seen, mainly because Kunzea ericoides rarely reaches the coast within the South Island range of Kunzea amathicola , and in the majority of places where it does reach the coast, Kunzea amathicola is absent.
Leaf, pherophyll, flower and hypanthia offer a wealth of useful characters enabling hybrid recognition of Kunzea amathicola × Kunzea linearis . However, because both parents have similar branchlet indumentum and the normally condensed spiciform inflorescences of Kunzea linearis may elongate toward the end of the flowering season, recognition of hybrids can be difficult. The leaves of Kunzea amathicola × Kunzea linearis hybrids are narrow to broadly lanceolate, and less evenly spaced than in Kunzea amathicola and, like Kunzea linearis , they tend to be more crowded toward the branchlet apices. The shape of the pherophylls is also diagnostic. In Kunzea linearis they are linear to linear-falcate and ascending to spreading; in Kunzea amathicola they are usually oblong, oblong-obovate, or elliptic, (rarely broadly lanceolate) and recurved. In the hybrid they tend to be linear-oblong and spreading to weakly falcate. Another distinction is the flowers. As the flowers of Kunzea linearis are sessile to subsessile, and those of Kunzea amathicola distinctly long-pedicellate, the hybrid can be recognised by the mixtures of sessile, subsessile to shortly pedicellate flowers. The hypanthia of Kunzea amathicola is typically broadly obconic, turbinate to hemispherical, while the flowers are up to 12.5 mm diameter, with white, orbicular to broadly ovate, spreading petals up to 3.7 × 4.0 mm. The antipetalous stamens of Kunzea amathicola are spreading and typically longer than the antisepalous stamens, while the style of Kunzea amathicola is very broad, and the capitate stigma obviously wider than the style diameter. Kunzea linearis has barrel-shaped, cupular or narrowly campanulate hypanthia up to 4.0 × 4.1 mm, much smaller flowers (up to 5.7 mm diameter), and cream, narrowly ovate to suborbicular, suberect to slightly recurved petals up to 2.0 × 1.9 mm. The stamens are mostly of similar length and tend to be erect rather than spreading, while the style of Kunzea linearis is rather narrow and the capitate stigma scarcely wider than the style diameter. Hybrids consequently tend to have broadly obconic to narrowly obconic or cupular hypanthia, of intermediate size ranges, and equally intermediate flower diameters, and petal sizes. The flower colour tends toward cream with the petals suberect to spreading, and longer than those of Kunzea linearis , with weakly spreading to strongly spreading, unevenly sized antipetalous stamens. The stigma of hybrid plants, as is typical of Kunzea amathicola , is mostly broadly capitate. The calyx lobes of the fruits of both species are also useful in distinguishing the hybrid. In Kunzea linearis the calyx lobes are narrowly deltoid, erect, or basally incurved toward the style remnant, while those of Kunzea amathicola are broadly obtuse to rounded and apically incurved toward the style remnant. In the hybrid the calyx lobes tend to be narrowly obtuse, suberect to erect and, as in Kunzea amathicola , they are apically incurved toward the style remnant. In many respects Kunzea amathicola × Kunzea linearis look morphology similar to Kunzea triregensis , and, as discussed under that species, it is postulated that Kunzea triregensis may have a hybrid ancestry involving both these species.
Kunzea amathicola × Kunzea linearis is mainly found in the far north of the North Island from Waipapakauri south to the Ahipara Gumlands. Kunzea amathicola × Kunzea linearis can be difficult to recognise on the gumlands because a third species, Kunzea robusta , is also present, and, together with Kunzea amathicola and Kunzea linearis , it has contributed to a complicated hybrid swarm around the old gum workings and roadsides. This bewildering array of hybrids was first discovered by A. P. Druce, who thought that some of the extremes represented a potentially new species, calling these " Kunzea Ahipara" ( Druce 1993, CHR!). Further research using more discriminating molecular markers than that used for this study ( de Lange 2007) is needed to determine the extent of introgression that has gone on between Kunzea amathicola , Kunzea linearis and Kunzea robusta on the Ahipara Plateau.
Kunzea amathicola × Kunzea robusta is less easily recognised than the other two hybrids because both parents have similar growth habits, bark types, and leaves. Kunzea amathicola is most likely to hybridise with Kunzea robusta , because they were, at least until recently, widely sympatric throughout much of the North Island range of Kunzea amathicola . This hybrid is best recognised by the hairs of the leaf margins which, though of varying thickness, rarely reach the leaf apex. The hairs tend to be shed from the apex to the base (a feature of Kunzea robusta ) as the leaf matures, such that older leaves are either completely glabrous or only sparsely hairy. Leaf shape in some hybrids is distinctly narrowly oblanceolate to lanceolate, with an acute rather than obtuse to rounded apex. The pherophylls of the hybrid tend to be deciduous rather than persistent, and rather variable in size and shape, recalling the usual condition of Kunzea robusta . The inflorescences though elongated tend to be compact. In practice this serves as a good field character, although some specimens of Kunzea amathicola can have reduced inflorescences, in which case recourse to the shape and degree of persistence of the pherophylls and the leaf laminal hairs is needed. In most cases Kunzea amathicola can be recognised by its ecology, because Kunzea robusta tends to avoid the active sand and sand dune habitats it prefers. Further, in the majority of locations where Kunzea amathicola is present, it now occurs in complete isolation from Kunzea robusta as a result of habitat destruction. Nevertheless this is not the case along large parts of the Kaipara Harbour and western Waikato coastline, where both species grow together and where the habitats have, and most cases continue to be, severely disrupted. Thus it is possible that some plants collected from these areas that I have assigned to Kunzea amathicola may ultimately prove to be hybrids.
Beyond the ubiquitous ‘kanuka’ this species is known to Muriwhenua (Ngati Kuri and Te Rarawa) and Nga Puhi Maori as ‘manuka’ and ‘rawiritoa’. Rawiritoa serves to distinguish Kunzea amathicola from the allied ‘rawiri’ ( Kunzea linearis ) and ‘rawirinui’ ( Kunzea robusta ) (W. Murray, G. Neho, and L. Foley pers. comm.).
Kunzea amathicola as Kunzea aff. ericoides (a) (AK 286081; “sand”) is appropriately listed under Appendix 2 of the New Zealand threatened and uncommon plants as 'At Risk / Declining’ ( de Lange et al. 2013b).
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