The Australian and New Zealand Species of Pittosporum

Abstract

Many of the Australian and New Zealand species of Pittosporum have long been treasured in gardens of Australia, New Zealand, France, and England, for their flowers, foliage and sweet scent, and several are common hedge plants and ornamentals in California and Florida. In addition to an aesthetic appeal, the species have scientific interest and potential economic value.The most recent inclusive treatment of Pittosporum is in the treatment of the family Pittosporaceae by Pritzel,^ who found it was impossible to make a satisfactory arrangement or classification of the genus and relied upon the geographic distribution of the species. He wrote as follows:Etwa 160 Arcen in den Tropen und Subtropen der ostlichen Hemisphare von West-Afrika bis 2u den Inseln des Pazifik, Da eine befriedigende naturliche Gliederung der Gattung noch nicht gegeben werden kann, so bleibt nichts anderes ubrig, als sie nach ihrer Verbreitung zu behandeln. Ein kiinfciges System der Gattung wird sich vor allem auf die Frucht zu grunden haben, und diese ist bei vielen Arten noch nicht geniigend bekannt. He discussed and keyed the species separately of the following regions:

Evolution of Insular Pacific Pittosporum (Pittosporaceae): Origin of the Hawaiian Radiation

“…Nevertheless, the idea that Australia is a center of species diversity for Pittosporum is not new. Cooper (1956), for example, recognized nine genera of Pittosporaceae (of which Pittosporum is the largest and the only one found outside Australia), which include a total of 48 species endemic to Australia. Thus, identification of Australia as a center of origin is a viable hypothesis, but one that requires further testing.…”

“…The two sister taxa, P. rigidum and P. turneri, are divaricating shrubs (intertangled branches that spread at wide angles), a feature unique to the New Zealand species, whereas P. corni-39 EVOLUTION OF INSULAR Pittosporum folium exhibits a regular growth form and is generally epiphytic. P. turneri is unusual and presents a more complex life history in having a divaricating juvenile form and a nondivaricating adult form (Cooper, 1956), which may be the result of hybridization between divaricating and nondivaricating species (B. D. Clarkson, pers. comm.).…”

“…comm.). Previous authors (e.g., Allan, 1961;Cooper, 1956), based on morphological characters such as capsule number, presence of a papery endocarp, divaricating habit, and putative recent colonization events, have suggested that as many as four evolutionary lineages are represented in New Zealand. Despite these morphological observations, it remains unclear whether the New Zealand taxa are monophyletic on the basis of the current data set.…”

Biological flora of New Zealand 13.Pittosporum cornifolium, tāwhiri karo, cornel-leaved pittosporum

“…This species is one of four shrub epiphytes endemic to New Zealand, the others being P. kirkii, Brachyglottis kirkii and Griselinia lucida (Oliver 1930). Pittosporum cornifolium has a distinctive whorled leaf arrangement, reddish brown (Hooker 1832) to yellow flowers (Cooper 1956), which are typically unisexual in function (Petrie 1921), and capsules characteristic of the genus with seeds embedded in a sticky pitch substance (Gaertner 1788). The primary habitats of P. cornifolium are lowland and coastal ecosystems which, in recent times (B200 years), have been subjected to widespread clearance and fragmentation, resulting in major reductions to the species' potential population range (F.M.…”

“…Clarkson 2011). Despite habitat discontinuity, P. cornifolium occupies a wide geographic range which extends throughout the North Island, including numerous offshore islands, to the northern reaches of the South Island (Cooper 1956). Targeted scientific research specific to this inconspicuous epiphyte species has been very limited.…”