New Zealand’s plants have a bit of a reputation for pronounced promiscuity. There is supposedly a high rate of hybridisation, or individuals of one species breeding with individuals of a different species.
I’m not entirely sure that this reputation is nationally deserved. Nevertheless, a striking example of hybridisation occurs in Pseudopanax, which is one of the groups I am researching; indeed, their hybridisation is what attracted me to them!
Two of the species – Pseudopanax crassifolius, horoeka, lancewood, and Pseudopanax lessonii, houpara, coastal five-finger – hybridise wherever they occur together, be this in the wild or in cultivation.
There are several other five-finger and lancewood Pseudopanax species in New Zealand. However, despite their very different appearance, most of the hybridisation I have seen appears to be between lancewood and coastal five-finger, and we are using genetic analyses to determine just how much gene-flow occurs between them.
Some of the hybrids are easy to identify, but others closely resemble one or other of the parental species. Any individual with leaves that look like those of lancewood but with two or more leaflets is actually a hybrid. Coastal five-finger always has broad leaflets.
Wellington’s Otari-Wilton’s Bush has a garden display of lancewood, coastal five-finger, and their hybrids, for 2009.
Lancewood occurs naturally throughout New Zealand. Coastal five-finger and the hybrids are native only to the coasts of the northern North Island (about Raglan and Gisborne northwards), but are frequently cultivated elsewhere. Coastal five-finger and the hybrids have escaped from cultivation, effectively becoming weeds, in many places outside their native distribution. They can be very invasive.