Natural global range

Pennantia corymbosa is endemic to New Zealand, although other species that are in the Pennantiaceae family are found elsewhere, such as Pennantia cunninghamii which is found in Australia.^[6]

New Zealand range

Kaikōmako is found in the North Island, South Island and Stewart Island, and in some islands near New Zealand.^[6] Kaikōmako is less common in the northern part of New Zealand as it prefers colder temperatures, so it is more common further south where it is colder.^[7] Kaikōmako was also thought to be present on Great Barrier Island but Gardner^[7] disproved this, finding that the specimens that were found there were specimens of Melicytus micranthus and not Pennantia corymbosa.

Life cycle/Phenology

Kaikōmako has three stages; juvenile, intermediate and adult.^[3] Kaikomako can fruit in its intermediate stage and even in its juvenile stage; this is known as precocious fruiting.^[3] Kaikōmako is described as a divaricate juvenile (spread out) which has heteroblastic development.^[8] Heteroblastic development occurs when the plant undergoes an abrupt change which can be in its form and its function. In Kaikōmako, this heteroblastic development happens from its intermediate stage to its adult stage at about 2 metres (6.6 ft), when the leaves change colour, shape and size becoming its adult form.^[4] One stem will eventually take over, rising upward and producing the larger adult leaves. Once Kaikōmako grows past 2 m and enters its adult stage Kaikōmako can grow to be up to 10 metres (33 ft) tall.^[9] Many of the Kaikōmako trees that are in their adult stage will still feature lower-level juvenile leaves whilst having upper-level adult leaves. Kaikōmako is said to have this juvenile divaricate phase because it may enhance the plant's chance at capturing light, which would be advantageous to the plant as it grows in forests which can be covered by the canopy of larger trees.^[8] Kaikōmako flowers from November to February and fruits from January to May.^[5] The fruits of the Kaikōmako tree are usually black but Beddie wrote that the fruits are certainly purple when ripe in the Wellington region.^[3] Kaikōmako is dioecious, meaning it has female and male flowers. The female flower's anthers are shorter than the males, and the male flowers have a rudimentary ovary that doesn't have a stigma.^[10] Kaikōmako can fruit at any stage of its development.^[3] Beddie shows photos of Kaikōmako twigs which have adult, intermediate and juvenile foliage, yet they're all fruiting.^[3] Beddie discussed how a seed from a juvenile fruit was germinated, and grew into a seedling but didn't produce fruit.^[3] Beddie also mentioned that because of Kaikōmako's precocious fruiting, as it had confused a lot of early experienced botanists.^[3]

The genus Pennantia contains only four species.^[6] Maurin studied the phylogeny of the genus Pennantia and found that Pennantia cunninghamii, which is found in Australia, is the sister to the rest of the genus.^[6] Maurin also found that the species Pennantia baylisiana, which is from the Three Kings Islands and is known as Three Kings Island Kaikōmako, was sister to a clade formed by P. corymbosa and the species Pennantia endlicheri, which is found on Norfolk Island.^[6]

Predators, parasites, and diseases

The name Kaikōmako translates to food (kai) for the bellbird (kōmako).^[11] As the name suggests, Kaikōmako fruit is often eaten by bellbirds. As the Kaikōmako plant fruits from January to May, the bellbird eats the fruit of the plant during these times. Honey bees have been observed to nest above the ground and have been found to nest in large holes in Kaikōmako trees.^[12] Honey bees also feed on and collect the nectar of the Kaikōmako tree when it is flowering (November to February).^[12] The fruit of Kaikōmako can be eaten by possums and other introduced mammals.^[13] Thrips feed on old leaves of shrubs and trees, including the Kaikōmako tree. The adult and larva thrips both do this. This can cause leaf silvering and speckling on Kaikōmako.^[14]