Lophomyrtus ×ralphii – Cockayne’s natural Taranaki hybrid

 

 

Scientific name: Lophomyrtus ×ralphii (Lophomyrtus from the Greek meaning crested myrtle, ralphii after Doctor Thomas Shearman Ralph [1813 -1891] who collected specimens of the plant for naturalist J. D. Hooker [1817-1911] near the city of Wellington)

 

Common Name: Small-leaved ramarama

 

Family name: Myrtaceae

 

The complex history surrounding the recognition of this natural wild hybrid has a strong connection with several of New Zealand’s most notable botanists and with the Meeting of the Waters reserve in Taranaki.

 

Myrtus is the former name for a small group of shrubs and small trees two of which eventually became reclassified under the genus Lophomyrtus. When listed by T. Kirk (1889) in The Forest Flora of New Zealand and subsequently by T. F. Cheeseman (1925) in the Manual of New Zealand Flora the plant in question was considered a distinct species Myrtus ralphii, having been first described by J. D. Hooker (1835).

 

Myrtus ralphii as it was known then was described as an erect branching shrub of about 2 metres or more, sometimes becoming a small tree. It was considered closely allied to Myrtus bullata or ramarama but with smaller leaves and with fewer-seeded berries. Ramarama is an erect shrub or small tree reaching 8 metres with green to reddish brown ovate foliage up to 3 cm long that has a distinctive blistered appearance. The other  species in this former genus, Myrtus obcordata or rohutu is a more slender branching shrub  or small tree of up to 5 m with much smaller  and obcordate (inversely heart-shaped ) leaves, up to 1cm long, about one third the size of the ramarama leaves, and with berries (4-8 mm diameter), about half size of ramarama.

 

By the time the first volume of the Flora of New Zealand was published there was no species with the epithet ralphii listed. There were in fact only the two species recorded in this volume under the new genus name separated from Myrtus, these being Lophomyrtus bullata, ramarama and Lophomyrtus obcordata, rohutu. Allan (1961) noted under the heading ‘Hybridism’ (p. 330) that what was previously known as ‘Myrtus ralphi’ was in fact a hybrid (M. bullata × M. obcordata).

 

It was field work undertaken by another eminent botanist and ecologist, Leonard Cockayne (1918) that first led to the proposal that Myrtus ralphii was a hybrid between ramarama and rohutu. It is also at this point that the particular connection is made with Taranaki.  

 

Cockayne examined many specimens from near Wellington and New Plymouth, or more precisely from the Meeting of the Waters Scenic Reserve just south of New Plymouth, along with specimens from the East Coast collected by William Colenso (botanist and missionary 1811-1899). He concluded that the specimens previously placed under M. ralphii were in fact of hybrid origin (M. bullata × M. obcordata). Cockayne supported his hypothesis with a description of the natural distribution of the two species in relation to the occurrence of M. ralphii and demonstrated that in the field a polymorphic series of intermediary forms or hybrids were usually found where both the parents met or were common. Cockayne sent specimens to Cheeseman who initially would only concede that it gave a certain amount of support to the view that it might be a hybrid but gave an example where he believed the ‘species’ M. ralphii occurred yet both the ‘parents’ were absent.

 

Botanical history records this debate resolved in favour of Cockayne’s proposition. Allan (Genetica 11, 1929, 491) concurred with Cockayne illustrating some of the many forms found in a forest remnant near Feilding, where both parents were common. Also seedlings raised from an intermediate form were shown to produce a complete range from nearly pure ‘obcordata’ to nearly pure ‘bullata’, with several forms that matched the original M. ralphii specimens.

 

The Taranaki connection was cemented when Cockayne (1918) described how upon seeing the range of forms present at the Meeting of the Waters, he realized for the first time that ‘ralphii’ may in fact be a hybrid:

 

“At the Meeting of the Waters, near New Plymouth, there not in a wind-swept habitat, but in the moist, still atmosphere of the forest-interior, I saw an astonishing series of intermediates between M. bullata and M. obcordata present. It was seeing these plants, indeed, which first suggested the theory of hybrid origin, and which led me to carefully examine the plants of the Wellington wind-scrub.”

 

Cockayne was later sent sixty one individual plant specimens collected from the Meeting of the Waters by R. H. Rockwell which he used in his analysis.  Cockayne commented in regard to the those specimens that “a casual glance at the collection shows that my former word ‘astonishing’ used with regarded to the polymorphy of Myrtus ralphii in that locality (Meeting of the Waters) is no exaggeration.” Incidentally, Cockayne (1915) had also previously noted an abundance of the parasitic Dactylanthus taylorii, or wood rose, had been observed at the reserve, “the plants extended thickly over an area of more than one acre”; unfortunately none has been found here in recent times.

 

On visiting the Meeting of the Waters today you can still find both the Lophomyrtus parents and intermediate ‘polymorphic’ variations that Cockayne described. They are generally easily located near and on both sides of the Waiwhakaiho River and in the adjacent remnant forest, and particularly at the eastern end of the reserve. The variation in leaf colour, size and appearance is indeed remarkable; a feature of hybridization that has been well exploited commercially throughout the country with a wide range of nursery bred, selected and named cultivars that derive from the same parental stock. The former New Plymouth nursery Duncan Davies for example released cultivars with such names as ‘Indian Chief’, ‘Katherine’, ‘Purpurea’, ‘Technicolor’, ‘Sundae’ and the like, each with some distinct colour or character but all deriving one way or the other from Lophomyrtus hybrids.

 

The Meeting of Waters Scenic Reserve is a popular recreational area for picnics, swimming and canoeing. It is also known for the fine example of podocarp/broadleaf forest, numerous emergent conifers (matai, rimu, totara, miro and kahikatea), the best matai regeneration of all West Taranaki Reserves, and a habitat conducive to and populated by many native epiphytic orchid species. But not so widely known is the reserve’s significance in New Zealand botanical history linked to the occurrence of the hybrid swarm between L. bullata and L. obcordata. When next you visit this fascinating place, remember that the great ecologist and author of New Zealand Plants and Their Story (1910), renowned for his extensive botanizing, pioneer ecological work and field explorations throughout the country, has also walked alongside these waters.

 

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