Coprosma and its near relatives

New Zealand has about 60 species of Coprosma (the number is uncertain because of undescribed entities). There are between 5 and 13 species in New Guinea, 8 species in Australia, and c. 13 species in Hawai'i.

The nearest relatives of Coprosma are Nertera, a widespread genus that includes 8 New Zealand species; Leptostigma, a smaller genus that includes one New Zealand species, Leptostigma setulosa; Durringtonia, a genus of one Australian species; and Normandia, a genus of one New Caledonian species (Markey et al. 2004 conference abstract).

In New Zealand, Coprosma is distinguished from Nertera and Leptostigma by being woody. Those other two genera lack woody tissue. All three genera have opposite leaves and the distinctive interpetiolar stipule which is the feature that best distinguishes Coprosma species from other New Zealand shrubs that have opposite leaves.

DNA studies (Markey et al. 2004 conference abstract) indicate that the Western Nelson endemic Coprosma talbrockiei, does not belong in Coprosma and is most closely related to Australian Durringtonia. It is retained in this key as Coprosma because it has not yet been assigned to another genus. It is the only species in the key which has leaves in threes, not in pairs.

Wild hybrids in New Zealand Coprosma

Coprosma is a genus in which many wild hybrids are known and a few of these are quite common. Where a plant proves difficult to identify because it lacks the right combination of characters for the species it keys to, the possibility that it is a hybrid should be considered. The only hybrid that has been included in the key is C. xcunninghamii, because it is the most commonly collected hybrid and because it is distinctive enough to key out.

Herbarium records give some indication of the relative frequency of wild hybrids, and this may assist with assessing whether a specimen is a hybrid. Below is a list of putative hybrids based on herbarium records. We have not critically examined these specimens and so the list should only be used as a general guide. Frequency, indicated by number of stars (* = 1 or 2 specimens, ** = 3–5 specimens, *** = 10–49 specimens, **** = 50 or more specimens), is assigned on the basis of numbers of specimens at CHR.

Note that Coprosma propinqua is the species most frequently involved in hybridisation, it is a parent with 14 other species. Coprosma dumosa is a parent in 5 crosses. Coprosma repens, C. ciliata, and C. robusta are parents in 3 crosses, the other species are parents involved in only 1 or 2 crosses. Some species have not been suspected of hybridising with others, e.g., C. areolata, C. petriei, C. rotundifolia, C. spathulata, C. virescens, and C. wallii.

C. xcunninghamii (= C. propinqua x robusta) ****

C. xkirkii (= C. acerosa x repens) ***

C. acerosa x rugosa **

C. acerosa x propinqua **

C. arborea x parviflora **

C. arborea x rhamnoides *

C. chathamica x propinqua var. martinii **

C. cheesemanii x dumosa **

C. cheesemanii x pseudociliata ***

C. ciliata x foetidissima **

C. ciliata x propinqua **

C. ciliata x rugosa *

C. colensoi x dumosa ***

C. crassifolia x rigida *

C. depressa x pseudociliata *

C. crenulata x serrulata *

C. crenulata x foetidissima *

C. dumosa x elatirioides *

C. dumosa x propinqua ***

C. dumosa x rigida *

C. dumosa x tenuicaulis *

C. ciliata x propinqua *

C. crassifolia x depressa *

C. crassifolia x propinqua *

C. foetidissima x propinqua *

C. linariifolia x propinqua *

C. lucida x propinqua *

C. macrocarpa x propinqua ***

C. macrocarpa x rhamnoides *

C. macrocarpa x robusta *

C. sp. (o) x dumosa ***

C. petriei x rugosa **

C. propinqua x repens *

C. propinqua x tenuifolia ***

C. pseudociliata x rigida **

C. repens x rhamnoides ***

C. robusta x rugosa **

C. robusta x tenuifolia **