Paratrophis is a genus of trees and shrubs in the mulberry family (Moraceae), order Rosales, native to New Zealand and the broader Pacific region. The genus comprises around 12 species of dioecious woody plants characterised by alternate leaves, small spike-like inflorescences, and fleshy drupaceous fruit. Within Moraceae, Paratrophis belongs to the tribe Moreae.
Members of the genus display a notable degree of heterophylly: juvenile plants often bear leaves that are deeply lobed or fiddle-shaped (pandurate), while adult foliage is comparatively simple and ovate. Leaf size varies widely between species — the large-leaved milk tree (Paratrophis banksii) carries adult leaves up to 85 mm long, whereas the small-leaved milk tree (Paratrophis microphylla) has adult leaves of only 8–25 mm. Flowers are small and inconspicuous, borne in catkin-like spikes; fruit are fleshy drupes ripening to red.
The genus has a complex taxonomic history. New Zealand species were long treated under the genus Streblus following Corner (1962), but a comprehensive phylogenomic study of tribe Moreae by Gardner et al. (2021) demonstrated that Paratrophis is distinct from a re-circumscribed Streblus, leading to worldwide reinstatement of the name.
The two most prominent New Zealand species — P. banksii (ewekuri or large-leaved milk tree) and P. microphylla (small-leaved milk tree), both known by the Māori name tūrepo — are endemic to Aotearoa New Zealand. P. banksii grows up to 12 m tall in coastal and lowland forests on fertile soils and is classified At Risk – Relict under the New Zealand Threat Classification System, its mainland populations reduced by browsing mammals and rodent predation. P. microphylla is more widespread and currently Not Threatened.
Etymology
The genus name Paratrophis is derived from Greek roots. The specific epithets of the two best-known species reflect key traits: banksii honours Sir Joseph Banks (1743–1820), the English naturalist and botanical patron, while microphylla means "small-leaved" in Greek, referring to the species' characteristically tiny foliage.
Distribution
Paratrophis is endemic to New Zealand, with P. banksii distributed across the North Island (from Kaitaia to East Cape, the Hauraki Gulf islands, and south to the Wellington region) and the northern South Island (Marlborough Sounds, Abel Tasman, Golden Bay). P. microphylla has a broader New Zealand distribution. Both species occur in coastal and lowland forests from sea level to approximately 200 m.
Ecology
Species of Paratrophis grow in coastal and lowland forests, typically favouring deep, fertile, often alluvial soils. On offshore islands they tolerate drier conditions and skeletal soils, and may colonise cliff faces, rock ledges, or cobble beaches. All species are dioecious, meaning male and female flowers are borne on separate trees. The two New Zealand species hybridise where their ranges overlap, producing intermediate populations that are difficult to assign to either species.
Conservation
Paratrophis banksii is classified At Risk – Relict under the New Zealand Threat Classification System (NZTCS 2023). Its mainland populations are sparse and threatened by possum and goat browsing, and by rodents that consume fruit, seeds, and seedlings. Because the genus is dioecious, small isolated populations are vulnerable to sex-ratio imbalance. Where rodents have been eradicated from offshore islands, the species has responded rapidly and positively.
Paratrophis microphylla is assessed as Not Threatened (NZTCS 2023).
Taxonomy Notes
Paratrophis was long subsumed into the genus Streblus: Corner (1962) transferred the New Zealand species, and Webb (in Connor & Edgar 1987) completed the move. The name Paratrophis was reinstated following a phylogenomic study of tribe Moreae (Gardner et al. 2021, Taxon 70: 946–88), which demonstrated that Paratrophis is phylogenetically distinct from a re-circumscribed Streblus. This revision is now followed worldwide. Key synonyms include Streblus banksii (Cheeseman) C.Webb and Streblus heterophyllus (Blume) Corner.
Propagation
Paratrophis banksii is easily grown from fresh seed and can be propagated from semi-hardwood cuttings, though cutting success varies. It is fast-growing and responds well to clipping, making it suitable as a specimen tree or hedge. It prefers deep, free-draining, fertile soil and becomes very drought-tolerant once established.
