| Helichrysum lanceolatum | |
|---|---|
 | |
Scientific classification  | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Asterids |
| Order: | Asterales |
| Family: | Asteraceae |
| Genus: | Helichrysum |
| Species: | H. lanceolatum |
| Binomial name | |
| Helichrysum lanceolatum (Buchanan) Kirk [1] | |
| Synonyms [2] | |
| |
Helichrysum lanceolatum, commonly known as niniao, is a species of plant endemic to New Zealand. [3] [4] [5]
Helichrysum lanceolatum is a member of the daisy family (Asteraceae) which is the most widely distributed and successful flowering family of plants in the world. [6] H. lanceolatum is among a significant number of New Zealand Helichrysum species, nine of which are endemic to New Zealand. [4] Many of these species grow into shrubs or trees and are woody, thus being termed tree daisy. [7] The New Zealand endemic Helichrysum species are heterogeneous, meaning they are not uniform and have distinctive traits. [8]
Helichrysum lanceolatum is a tangled, much branched, interlacing shrub, growing up to 3 m in height. [9] It has light brown bark with slightly grooved branches and alternate leaves. [5] Young branchlets are finely hairy [9] and evolve from dark brown to lighter brown with dark streaks as the wood thickens and ages. [10] The leaves are green/grey in colour and are pointed or rounded, [9] smaller on flowering branches, [11] and are arranged alternately along branches. [10] The upper surface of the leaf is smooth, [11] the tip is silver, and the underside is grey and downy. [9]
The flower heads consist of abundant clusters of very small, up to 1 cm diameter, creamy white, scented flower heads. [5] These can be confused with the furry galls induced by Cecidomyiidae larvae. [10] The composite or compound flowers, [7] resembling a single flower, [12] are made up of multiple small flowers bordered by rows of discreet bracts; [13] the whole structure termed a capitulum. [8]
Morphological differences are strongly linked to habitat and soil substrate with much smaller leaves found on plants growing in full sun and in rocky soil. [14]
Helichrysum lanceolatum contains the following varieties: [3]
Helichrysum lanceolatum is endemic to New Zealand, so only occurs in Aotearoa/New Zealand. [15]
The genus Helichrysum has 500–600 species in Africa, Madagascar, the Mediterranean basin, Macaronesia, western and central Asia, and India. [16]
Helichrysum lanceolatum is found throughout New Zealand and is widespread. [5] It is termed morphologically variable, meaning it has differing forms depending on habitat and geographical location. [14] Its New Zealand range is from the Northland Peninsula to the south of the South Island from sea level to about 900m. [17] It is also found on Great Barrier Island [18] and the Chatham Islands. [19]
Helichrysum lanceolatum grows well in dry soil [5] and prefers open, sunny aspects and rocky ground. [9] Historically thought to grow only in rocky habitats [20] it now appears to grow well in ecologically disturbed sites, [14] forest margins, [17] as well as dry and humid and open forest ecosystems [21] and coastal habitats. [22] It is one of several native shrubby understory species in pōhutukawa/kānuka dominant forest on Great Barrier Island. [18]
Helichrysum lancoelatum has composite flowers which encourages pollination. [7] Many flowers can be pollinated by a single visiting insect, [7] even though only 2–3 florets within a cluster of 8–12 are female. [5]
Insects are attracted by nectar-secreting glands on the inner base of each single flower, [7] a strategy for mass pollination by a single insect visit. [7]
Following successful fertilisation, flowers wither and drop off, allowing seeds to develop within achenes. Achenes are hard-shelled casings for a single seed [23] and are covered with fine, downy hairs that act as parachutes [7] aiding wind dispersal function. [24]
Aaron Wilton's research in 1997 suggests that most native Helichrysum species are pollinated by a wide range of insects, though more research is needed on pollination or phenology of New Zealand Helichrysum species. [8] H. lanceolatum flowers from October to January [17] with seeds ripening in February [5] and fruit developing in December. [9]
Helichrysum lanceolatum prefers rocky soils and full sun [9] and grows well in dry soil and can tolerate low rainfall. [5] It is also one of many native shrubs within the coastal, mid-dune plant community, so can tolerate a sandy soil substrate. [22] Interestingly, a 2004 study showed the H. lanceolatum populations of Central Otago, a drastically modified environment, to be more susceptible to fire and drought, perhaps due to the sparse vegetation cover and disturbed ecology of the area. [25]
While not unpalatable, a 2002 study showed Helichrysum lanceolatum to be less palatable to introduced ungulates than other native species. [26]
H. lanceolatum is a host plant to some species in the native gall fly family Cecidomyiidae, whose larvae induce a large gall on the developing flower head. [27] More research is needed to understand the relationship between these species.
Other examples of moth species whose larvae feed on H. lanceolatum are the Pseudocoremia rudisata, and the Celama parvitis, a rare small moth, occurring in eastern and inland South Island shrublands whose larvae feed on the foliage of H. lanceolatum. [28] The larvae of another moth species, Helastia siris, may be associated with H. lanceolatum though more research is needed. [29]
A subsequent study has highlighted the association between the moth species Helastia triphragma and H. lanceolatum on Ōtamahua/Quail Island in Whakaraupō/Lyttelton Harbour and suggests that increasing plantings of H. lanceolatum may help to keep populations of this moth stable and attract other native moths like Asterivora chatuidea. [30]
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The Latin derivation for Helichrysum comes from the Greek word, helios, the sun; chrysos, gold [15] and lanecolatum, lance shaped; from the Latin lancea, light lance, spear. [15] The Māori name niniao means glowing as dawn. [5]
H. lanceolatum has many historical synonyms and has been named both Helichrysum glomeratum and Helichrysum aggregatum, both describing the ball-shaped flower heads. [17]
In New Zealand Flora Vol. 1, H.H Allan, 1982, recognised three varieties due to different growing habits, distribution, and leaf size and shape; Helichrysum glomeratum, and var lanceolatum and var majus. The species Helichrysum glomeratum var lanceolatum was soon found to already be named Helichrysum lanceolatum, [11] and var majus not specifically distinct from H. lanecolatum, thus Helichrysum lanceolatum remained the official scientific name. [11]
A DNA sequencing study in 2007 of H. lanceolatum and Anaphalioides bellioides, previously Helichrysum bellioides, [31] showed intergeneric hybridisation (crossing of genes between two distinct species within the same genus), occurring between these endemic species. [32] Both species belong to the Gnaphieae tribe (Asteraceae family). [31] The study looked at species from two distant Banks Peninsula populations, at Gibraltar Rock in the southern Port Hills and Long Bay Road in the remote eastern bays; [32] the hybrids studied showed many distinctive traits, of particular note, serrated leaves, a trait of neither parent plant and they demonstrated lower fertility. [32] The hybrid species has been named Helichrysum purdiei. [33]
Hybrids between Helichrysum lanceolatum and Ewartiothamnus sinclairii (Hook.f.) have also been reported. [32]
The late botanist Tony Druce noted that plants from Paerutu (Surville Cliffs), in Te Paki Ecological District on the Northern most point of the North Island [34] might be a distinct species due to their trailing growth habit. [35] This population also has fewer side branches, and smaller leaves than other North Island populations. [14] Druce also identified a large round-leaved form from Hick's Bay and recognized this species as having distinctive characteristics. [2] More recent studies have shown little genetic variation between populations, but some variability between geographically distant populations. [36]