Kunzea salterae de Lange, 2014

de Lange, Peter J., 2014, A revision of the New Zealand Kunzea ericoides (Myrtaceae) complex, PhytoKeys 40, pp. 1-185 : 45-49

4. Kunzea salterae de Lange sp. nov.

A K. tenuicauli foliis constanter longioribus angustioribus lineo-lanceaceolatis, hypanthio maiore glabrato anguste obconico vel infundibuliforme, stigmate plano anguste capitato, lobisque antherae profunde sulcatis non testiculatis differt.

Holotypus

(Fig. 21). New Zealand: North Island, Bay of Plenty, Moutohora (Whale Island), McEwans Bay, 37°51'26"S, 176°58'57"E, 20m a.s.l. 'Occasional on sand dunes well away from active or senescent thermal areas’. P. J. de Lange 6471 & P. B. Cashmore, 15 Apr 2005, AK 289816! Isotype: AD!

Etymology.

The specific epithet salterae commemorates my colleague and botanical illustrator for this monograph Josh Salter (1946-), whose critical attention to detail when illustrating specimens of Kunzea salterae proved invaluable in deciding on an appropriate taxonomic rank.

Description

(Figs 22, 23, 24). Growth habit shrubs to small trees 0.1-6(-10) × 2-4(-6) m with broad, spreading to somewhat pendulous crowns, rarely plants completely decumbent, sprawling across ground. Trunk usually multi-trunked from base, up to 0.3 m d.b.h., these mostly widely spreading to suberect, flexuose, often basally buttressed, branches frequent from base in exposed sites, otherwise naturally thinning in the lower half of the trunk. Bark early bark brown, initially firm, somewhat sinuous-fluted, elongate, over time cracking transversely (especially on branch flanges), and with apices gradually detaching and raising to present as small lunate (in profile) flakes, old grey-brown bark flaking readily in small, somewhat irregular tabular shards, often with small lunate secondary peeling; somewhat corky to chartaceous. Branches Two to many, suberect to widely spreading, rarely ascending, mostly pendulous, branchlets numerous and very leafy, rather slender, initially subterete soon becoming quadrangular; sericeous, indumentum initially copious rarely glabrate to glabrous, hairs on young rapidly growing apices, copious, sericeous, straight, antrorse-appressed up to 0.55 mm, these soon falling; other mostly divergent hairs long persistent, (especially opposite leaf buds and expanding foliage), 0.04-0.08(-0.1) mm, hyaline to translucent (appearing white when young maturing grey), apices ± curled, often admixed (particularly toward branchlet apices and near decurrent leaf bases) with deciduous antrorse-appressed, straight to somewhat sinuous hairs up to 0.28 mm. Vegetative buds inconspicuous at resting stage 0.5-1.0 mm diam.; scales deciduous; (0.6-)1.2-2.3 mm long, stramineous to pale brown, initially broadly ovate to ovate-lanceolate grading through broadly lanceolate to narrowly lanceolate, midrib strongly keeled, prolonged to apiculate tip, with one prominent row of 4-10 oil glands on either side of midrib, margins, apex, apiculus and keel finely ciliate. Leaves ± spreading to patent; lamina (4-)10(-18) × (0.6-)1.2(-2.0) mm, bright glossy green, yellow-green, bronze-green to dark green; linear-lanceolate to narrowly oblanceolate, flat not recurved, apex acute to subacute, cuspidate, rarely obtuse to rounded; base attenuate; adaxial surface slightly concave to flat, finely glandular punctate; oil glands 180(-280), more evident when dry; midrib slightly raised to depressed near base otherwise depressed for entire length, initially densely covered in fine, antrorse-appressed silky hairs up to 0.22 mm, becoming glabrescent; abaxial surface slightly convex, finely glandular punctate, oil glands less obvious when fresh than when dry, up to 100, with the larger glands aligned longitudinally along midrib; midrib slightly raised, usually glabrous, sometimes with a fine weft of silky, deciduous, antrorse-appressed hairs near base; lamina margin sparsely to densely, finely sericeous, hairs mostly antrorse-appressed, up to 0.5 mm, hyaline to translucent, appearing as white to naked eye; hairs in 1-2 somewhat irregular rows just failing to meet short of cuspidate leaf apex. Perules scarious, basal ones usually persistent, 1.2-1.4 mm long, stramineous to brown, broadly to narrowly lanceolate, involute, midrib strongly keeled prolonged as a cuspidate apex, with one row of 4-8 oil glands on either side of midrib, lower two-thirds glabrous, upper one-third finely ciliate; remaining perules deciduous, chartaceous, 0.6-1.4 mm long, pale pink to pinkish-white when fresh, drying apricot to apricot-pink, broadly oval, ovate to rhomboid, finely and copiously ciliate, strongly keeled, keel prolonged, apiculate, margins and keel more distinctly ciliate. Inflorescence a (2-)4(-8)-flowered corymbiform botryum up to 45 mm long, usually on brachyblasts, rarely on long shoots in which case invariably terminal (only very rarely with terminal vegetative growth). Inflorescence axis densely invested with mostly divergent hairs. Pherophylls deciduous (falling very early), mostly squamiform, rarely foliose, spreading, 0.6-1.8 mm long; squamiform pherophylls brown or amber, sometimes pink, drying apricot-brown, broadly deltoid to oblong-ovate, margins involute especially in upper one-third, midrib strongly keeled prolonged as cuspidate apex, with one row of 4-8 oil glands on each side of midrib; glabrous except for the finely ciliate margin and apex; foliose pherophylls bright green, linear, margins and apex finely ciliate; both types grading into chartaceous, into perules and/or leaves at inflorescence terminus. Pedicels (1.1-)2.6(-3.0) mm long at anthesis and elongating slightly after anthesis, terete, finely invested in divergent to subantrorse sericeous hairs. Flower buds pyriform to clavate, apex domed with calyx valves not or scarcely meeting. Fresh flowers when fully expanded up (9-)10(-12) mm diam. Hypanthium (2.1-)2.2(-3.8) × (1.8-)2.2(-3.2) mm, with free portion 1.0-1.6 mm long, reddish-brown when fresh, drying resinous brown to grey; narrowly obconic to funnelform terminating in a slightly thicker rim bearing five persistent calyx lobes; surface smooth, finely glandular punctate, sparsely hairy to glabrate, with five rather weakly defined ridges leading up to calyx lobes (these becoming more distinct upon drying); hairs scattered, subantrorse to antrorse, flexuose. Calyx lobes 5, upright (not spreading), 0.6(-0.9) × 1.1(-1.3) mm, persistent, broadly to narrowly triangular, weakly and broadly keeled (the keel though ill-defined in fresh specimens recognisable as a dark pink to red, thicker central prolongation of the hypanthium ridges), margins cream to pale yellow, gland-dotted, subcoriaceous, glabrate except for distinctly ciliate apex. Receptacle dark red at anthesis. Petals 5, spreading, 1.4-1.6 × 1.4-1.6 mm, white, rarely basally flushed pink, orbicular to suborbicular, apex obtuse to rotund, margins usually finely crimped, oil glands colourless or rose-pink, scarcely evident when fresh. Stamens 28-36(-38) in 1-2 weakly defined whorls, adnate to receptacular rim, filaments white rarely tinged rose-pink toward base. Antipetalous stamens 3(-5) antisepalous 3(-4). Outermost antipetalous stamens strongly outcurved, on filaments 2.5-3.25 mm long, inner stamen 1.8-2.2 mm, outcurved, on occasion a further 1-2 incurved or outcurved, stamens 0.8-1.0 mm long, positioned at the base of the outermost antipetalous pair. Antisepalous stamens much shorter than antipetalous, 0.6-0.9(-1) mm, incurved, outcurved or in mixtures of both. Anthers dorsifixed, 0.11-0.16 × 0.10-0.14 mm, scutiform to ovoid, latrorse, each anther deeply and longitudinally furrowed, with one anther lobe in each pair fused at right angles along inner margin with adjoining anther lobe to form a prominent ‘pinched’ longitudinal ridge. Pollen white, (10.2-)14.7(-16.6) μm. Anther connective gland prominent, pale orange to pink when fresh, drying orange-brown, spheroidal, finely papillate, somewhat farinose. Ovary (3-)4 locular, each locule with 8-10 ovules in two rows on each placental lobe. Style 2.1-3.2 mm long at anthesis, white basally flushed with pink; stigma capitate, up to 1 × style diam., flat, abruptly broadened, pale cream, finely papillate rugulose. Fruits rarely persistent, (2.0-)2.2(-2.7) × (2.0-)2.9(-4.0) mm, light brown to grey, cupular to suburceolate, splits concealed by dried, erect, free portion of hypanthium. Seeds 0.80-1.00 × 0.45-0.48 mm, narrowly oblong, oblong, oblong-obovate to falcate-oblong or elliptic, curved near apex, laterally compressed, 2-3-angled with convex to flattened faces, apex rounded; base cuneate to oblique, ± flattened; testa semi-glossy, orange-brown; surface coarsely reticulate, ridges prominent, central portion of some cells furnished with short, tubular-spiny, protuberances. FL: Aug-Apr FT: Aug-Sep. Chromosome Number n = 11II, 2 n = 22 (AK 283253, P. B. Cashmore s.n., AK 298088, P. J. de Lange.

Representative specimens

(15 Sheets seen). Moutohora (Whale Island): P. Hynes s.n., 28 Aug 1970, (AK 185215); Sulphur Bay, Geothermal Area, P. B. Cashmore s.n., 4 Sep 2002, (AK 297561); Boulder Bay, P. B. Cashmore s.n., 4 Sep 2002, (AK 283250); Sulphur Bay, Thermal Area (Active), P. J. de Lange 6469 & P. B. Cashmore, 15 Apr 2005, (AK 289814); Pa Hill/Summit Hill Saddle, P. J. de Lange 6469 & P. B. Cashmore, 15 Apr 2005, (AK 289815); Summit Hill (southern slopes), P. J. de Lange 6472 & P. B. Cashmore, 15 Apr 2005, (AK 289817, Duplicate AD).

Distribution

(Fig. 7). Endemic, New Zealand, North Island, Bay of Plenty, Moutohora (Whale Island) (sea level to 220 m a.s.l.).

Recognition.

Kunzea salterae is recognised at species rank because it forms a true-breeding, morphologically stable population, recognised here by a combination of growth habit, branchlet hair and floral characters (see Table 1 ) as well as minor but consistent DNA sequence differences in the ETS marker region (Table 2 ; see also de Lange 2007; de Lange et al. 2010). It is further distinguished ecologically by its preference for sand dune and geothermal habitats (Fig. 24A-C), and also by its sympatry/syntopy with Kunzea robusta , from which it is isolated morphologically, and from which I saw no field evidence of hybridism (see below). The presence of Kunzea salterae on Moutohora, a small (143 ha) volcanic island estimated to be 36 000 years BP (see Ramsay and Hayward 1971) is as remarkable as it is unexpected. Whether the species evolved in situ, is a remnant population that persisted there following the extinction of other populations that had colonised the lowered shore line of the Bay of Plenty prior to the sea level rise that occurred at the end of the last glacial maximum, or has recently colonised the island from another as yet unrecognised mainland location remains to be determined.

In past literature Kunzea salterae has usually been recorded as Kunzea ericoides (e.g., Parris 1971 (as Leptospermum ericoides ); Ogle 1990; Smale 1994). However, plants found growing within the geothermally active part of the island have also been referred to Kunzea ericoides var. microflora (= Kunzea tenuicaulis of this revision) ( Wildlands Consultants Limited 2005) probably because of their low stature, apparent habitat preferences, and the widely held but largely mistaken belief (see Kunzea tenuicaulis ) that any decumbent Kunzea found near active fumaroles was that variety.

Kunzea salterae has some similarity to Kunzea tenuicaulis . In particular the ability to grow in geothermal habitats (Fig. 24C), the characteristically multi-trunked growth habit, broadly spreading canopy, and numerous rather fine, often pendulous branches and branchlets are typical of both species, while the abundance of short, divergent branchlet hairs (Fig. 23A-E) is shared otherwise only with the allied Kunzea serotina . Kunzea salterae , like Kunzea tenuicaulis , has a tendency to produce numerous semi-erect, somewhat trailing or completely decumbent plants in the vicinity of or around active fumaroles (Fig. 24C). From Kunzea tenuicaulis , Kunzea salterae is distinguished by its longer (up to 18 mm cf. up to 10 mm), linear-lanceolate (Fig. 22A, C-G) rather than oblanceolate to obovate leaves, by its slightly larger (range 2.1-3.8 mm long) and glabrate, rather than small (range 1.8-3.1 mm long) and puberulent, narrowly obconic to funnelform (Fig. 22I-J) rather than cupular to campanulate hypanthium, by its flat, narrowly capitate rather than slightly domed centrally depressed stigma (Fig. 22K), and by the non-testiculate, deeply furrowed thecae (Fig. 22L). Only one mitotic count was obtained from Kunzea salterae and this matched Kunzea tenuicaulis , Kunzea serotina and Kunzea toelkenii in having uniformly small chromosome complements. Further observations using different plants are needed to confirm this.

Aside from Kunzea tenuicaulis , the narrowly linear-lanceolate foliage of Kunzea salterae is similar to that of Kunzea linearis and Kunzea ericoides . However, the shorter glabrate leaves of Kunzea salterae are distinct from the leaves of Kunzea linearis , and branchlet hairs of Kunzea salterae are short and divergent rather than long, silky and antrorse. Further, the inflorescences of Kunzea salterae are corymbiform rather than spiciform, and the individual flowers are distinctly pedicellate, never sessile to subsessile. Both species are also allopatric, the nearest occurrence of Kunzea linearis to Kunzea salterae being the Tairua Peninsula on the eastern side of the Coromandel Peninsula some 145 km north-west of Moutohora.

Kunzea salterae can be distinguished from Kunzea ericoides by its copiously hairy branchlets furnished with much longer divergent hairs than are on Kunzea salterae branchlets. Further both species are allopatric and have different ITS and ETS sequences (Table 2 ).

On Moutohora, Kunzea salterae is sympatric with Kunzea robusta , (e.g., P. J. de Lange 6473 & P. B. Cashmore (AK 289818)), which grows locally on the southern slopes of Summit Hill. The typically multitrunked, pendulous growth habit, consistently narrow linear-lanceolate leaves, and abundance of short, divergent branchlet hairs easily distinguish Kunzea salterae from Kunzea robusta , which has long, silky, antrorse-appressed, branchlet hairs. Kunzea robusta is the less common of the two species on Moutohora, and is absent from sites of geothermal activity there.

Kunzea salterae appears to combine the narrow linear leaves typical of Kunzea linearis , with the growth habit of Kunzea tenuicaulis . Interestingly, artificial F1 hybrids (see de Lange et al. 2005) using Kunzea tenuicaulis as the pistillate parent, (e.g. P. J. de Lange 5816 (AK 285268)), are a close morphological match for Kunzea salterae . Based on current herbarium and field evidence, Kunzea linearis is not known from the Bay of Plenty (see above). Nevertheless, the extremely similar morphology exhibited between the aforementioned F1 hybrids and Kunzea salterae is rather striking. Further research into the possible hybrid origin of Kunzea salterae , particularly whether it is derived from past hybridism between Kunzea linearis and Kunzea tenuicaulis , would be worthwhile.

The rDNA ITS and ETS sequence data (Table 2 ) showed that Kunzea salterae was most similar to Kunzea tenuicaulis ( de Lange 2007). Otherwise, despite its narrow linear-leaves, it consistently clustered with the other ‘small-leaved’ Kunzea , Kunzea tenuicaulis , Kunzea toelkenii and Kunzea serotina ( de Lange 2007). ETS sequence data also indicated a relationship with Kunzea ericoides , Kunzea linearis , Kunzea tenuicaulis , Kunzea toelkenii , Kunzea serotina and Mt Egmont samples of Kunzea robusta all of which share a guanine/cytosine mix ( de Lange 2007; de Lange et al. 2010). Otherwise Kunzea salterae differs from all other Kunzea taxa within the Kunzea ericoides complex by having a unique cytosine/thiamine mix in its ITS-2 sequence (Table 2 ; see also de Lange 2007; de Lange et al. 2010).

The identity of Kunzea on Tuhua (Mayor Island) was discussed by de Lange (2007) who noted that one collection from the 'crater rim’ of that island (AK 262432, G. W. Mason s.n.), approached Kunzea salterae in general branching habit, leaf shape and size, and by the numerous small, corymbiform inflorescences. Although this specimen was in poor condition, de Lange (2007) noted that the branchlet indumentum comprised mainly fine, somewhat wispy, appressed antrorse hairs, and that the anthers lacked the deep furrow and fused ‘pinched’ ridge typical of Kunzea salterae . Subsequent field work on that island has shown that the Kunzea there forms a uniform population matching the 'eastern North Island variant’ of Kunzea robusta which is common on the adjacent eastern side of the Coromandel Peninsula (see below) ( Wilcox et al. 2012).

Ecology.

Kunzea salterae is a widespread and at times dominant woody shrub or tree of the coastal forest, geothermal field, cobble beach and sand dune vegetation of Moutohora (Fig. 24A-C). As Kunzea ericoides var. ericoides , Smale (1994) described in detail the vegetation associations, population structure and dynamics of Kunzea salterae . He concluded (p. 441) that this species 'may replace itself indefinitely on the unstable dunes on Whale [Moutohora] Island, where the community is still expanding’. Smale’s study was confined to Kunzea ‘heaths’ developed over sand dunes, and so he did not appraise the associations formed by Kunzea salterae within the geothermally active parts of Moutohora. From observations outside the sand dune habitat, I suggest that Kunzea salterae , being a species evidently favouring frequent disturbance, will also have a long standing presence in the geothermally active parts of Moutohora, where it is the dominant vascular plant species. Indeed, in its abundance and growth within the thermal areas on this island, it behaves very much as Kunzea tenuicaulis does in similar mainland habitats within the Taupo Volcanic Zone of the North Island ( Burns 1997). Kunzea salterae is currently often the dominant canopy cover outside the sand dune and geothermal areas of Moutohora (Fig. 24B), but it is expected to decline as the coastal forest regenerates and other larger, coastal forest species attain local dominance.

Smale (1994) observed that the sand dune vegetation dominated by Kunzea salterae was species poor, recording 29 vascular plant taxa within what he regarded as ‘older’ stands (i.e. ≥ 27 years of age). The same is the case for the thermal areas, where, aside from dense coverings of the mosses Isopterygium albescens (Hook.) A.Jaeger, Campylopus pyriformis , Dicranella dietrichiae ( Müll.Hal.) A.Jaeger, Philonotis tenuis (Taylor) Reichardt and Hypnum cupressiforme Hedw. var. cupressiforme ( Beever and Brownsey 1990), vascular plants (other than Kunzea ) are extremely scarce. Smale observed that inland from the dune systems his " Kunzea ericoides var. ericoides " stands changed from the multi-stemmed semi-prostrate growth habit (the Kunzea salterae of this treatment) to erect single-stemmed trees. From my observations this transition is not nearly as clear cut as he described, with Kunzea salterae growing in most situations across the island with a consistently multi-stemmed habit. However, occasional larger erect trees do occur toward the back of the dune systems at Boulder Bay and these are not Kunzea salterae but Kunzea robusta , a species that avoids thermal areas, and favours more stable habitats, overlying better developed soils, within the more mature successional coastal forest on the island.

Hybridism.

No putative wild hybrids have been observed on Moutohora, and putative hybrids were not evident in the 15 Kunzea herbarium specimens examined from that island. The distinctiveness of Kunzea salterae was recognised too late in this revision to include it in hybridisation experiments ( de Lange et al. 2005).

Vernacular name.

No specific name for Kunzea salterae has been recorded.

Conservation status.

Currently the species, as Kunzea aff. ericoides var. microflora has been appropriately assessed by de Lange et al. (2013b) as 'At Risk / Naturally Uncommon’ qualified ‘IE’ (Island Endemic) and ‘OL’ (One Location).