Distribution Map
Decaisnina congesta Barlow, Brunonia 5 (1983) 204. - Type:
Gray 1168 (holo QRS; iso CANB), Queensland, State Forest
Reserve 607, Bridle Logging Area, 16059' S 145037' E, l.xii.1978.
For description and synonymy see Barlow, Flora of Australia 22 (1984) 75. Apart from the relatively long flowerless basal part of the inflorescence axis, Decaisnina congesta has few specialized characters, and thus presents a relatively generalized facies for the genus. The species can be identified locally by its combination of distinctly petiolate, relatively small, weakly bifacial leaf laminas 5-8 cm long, obtuse to rounded with a small mucro at the apex, inflorescence with 1-3 pairs of triads crowded near the end of the axis, and corolla 23-30 mm long. The flower colour has been recorded as red in the lower part and green above.
Decaisnina congesta is distributed in New Guinea and Queensland, Australia (Fig. 4; 9 collections seen), recorded at elevations from sea level to 250 m in Queensland and at 1875 m in New Guinea. It occurs in open forests and rain forests, parasitic on various hosts; those recorded include Alstonia, Engelhardtia, and Morus.
The species is probably related to the more widespread D. triflora, with which it has an adjoining area, and may be a local differentiate of this stock. It differs from D. triflora in its greatly reduced inflorescence and weakly bifacial leaves. See notes under D. celebica on inflorescence structure and D. pedicellata on possible relationships.
Decaisnina congesta was
previously thought to be endemic to Australia (Barlow, 1984),
and the specimen from New Guinea represents a significant range
extension. The range disjunction across Torres Strait suggests
that the species may have differentiated in New Guinea and reached
Australia as part of the floristic exchange resulting from Tertiary
climatic cycles (see notes under D. angustata and D.
triflora). Other loranth species with similar areas in New
Guinea and north Queensland include Amyema conspicuum, A. queenslandicum,
Cecarria obtusifolia and Dendrophthoe falcata.
Photographs
Queensland, Australia. Photo by Gerhard Glatzel.
Decaisnina congesta (DLN 2797). Sterile specimen growing on Casuarina, showing epicortical roots. Barron River, S. Mareeba, Queensland, Australia. Photo by Dan Nickrent.
Decaisnina congesta
updated 18 January 2007