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The breeding systems of the 110+ species of Coprosma J.R. Forst. & G. Forst. across the Pacific are largely considered dioecious, with male and female flowers occurring on separate plants (oliver 1935). However, for many species, particularly of New Zealand, the dioecious breeding system is leaky. Coprosma species exhibiting leaky dioecy are primarily dioecious, with male and female flowers on separate plants, but individuals occasionally develop apparently functional bisexual flowers, which sporadically occur among an abundance of unisexual flowers. A putative monoecious Coprosma taxon was once reported for the Macquarie Island individuals of C. perpusilla Colenso (= C. pumila Hook.f.), but later dispelled as being dioecious (lloyd & Horning 1979).

In March 2016, the first author of this paper embarked on an archipelago-wide tripof the Hawaiian Islands aiming to collect and observe multiple populations of all endemic Hawaiian species of Coprosma (Rubiaceae). As a result, four confirmed cases of monoecious individuals were documented for Hawaiian Coprosma for the first time. Three additional instances may represent either monoecious or leaky dioecious observations. The collection results are detailed below. All specimens are deposited at BISH and duplicates were either sent to PTBG or US herbaria. Figure 1 depicts photos of monoecious individuals collected in the field.


Records of the Hawaiian Biological Survey



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