Aust. J. Bot., 1974, 22, 531-621

A Revision of
the Loranthaceae of New Guinea and the Southwestern Pacific

B. A. Barlow

School of Biological Sciences, The Flinders University of South Australia, Bedford Park, S.A. 5042.

Abstract

The Loranthaceae of New Guinea and the southwestern Pacific comprise 12 genera, 59 species, 11 subspecies and 2 varieties. Of the species recorded, approximately onehalf are endemic to the New Guinea mainland. About 20 other species are endemic in the area dealt with, most having distributions in New Guinea and adjacent islands. Nine species also occur in Australia, and five species extend to Indomalaya.

Twelve species are described as new, viz. Amylotheca acuminatifolia, Lepeostegeres deciduus, A myema angulare, A. apodum, A. brassii, A. canaliculatum, A. dilatipes, A. involvens, A. kebarense, Sogerianthe cupuliformis, Dendrophthoe pelagica and D. trichanthera. Five subspecies are described as new, viz. Amyema conspicuum subsp. fulvicalyx, A. scandens subsp. crassifolium, A. seemenianum subsp. flexuosum and A. wichmannii subspp. purum and aggregatum. One variety is described as new, viz. Macrosolen cochinchinensis var. lanceolatus. There are 15 new combinations, viz. Decaisnina dlamuensis, D. micranthes, D. papuana, D. parvifolia, D. pedicellata, D. stenopetala, Amylotheca banksiana, Amyema scandens subsp. plicatulum, A. artense var. papuanum, A. seemenianum subsp. melastomifolium, A. squarrosum subsp. rhopalanthes, A. strongylophyllum subspp. rigidiflorum and barbellatum, A. tetraflorum and A. tetrapetalum.
Chromosome numbers are given where known.

Introduction

The present revision concludes a taxonomic study of the Loranthaceae of Australasia and the South Pacific. In a previous paper (Barlow 1966) the taxa of Australia and New Zealand were revised; in the present account the Loranthaceae of New Guinea and the remaining southwestern Pacific area are treated. Almost all of the South Pacific Loranthaceae are included in these two revisions; the only other species known in the South Pacific is Notanthera heterophylla (R. & P.) G. Don. This species occurs in Juan Fernandez and has been discussed by Barlow and Wiens (1973).

This work is intended primarily to facilitate identification of the genera and species. Synonymy has been confined to original references and to the few reference works on the Loranthaceae of the region (Danser 1929, 1931, 1934, 1935, 1936, 1938, 1940; Engler and Krause 1935; Barlow 1966). However, it includes references to published illustrations of the species dealt with. Details of type specimens are given, and have been seen in original or as photographs except where stated otherwise. Selection of lectotype has been made by the author except in cases where a reference is given. Details of specimens examined have been restricted in most cases to a few represen-tative specimens illustrative of the morphological variation and geographical range of the species or subspecies. A list of identifications by collector's numbers is given as Appendix 1, and is provided because the duplicates of many major New Guinea collectors are widely distributed and because many of these collections were previously undetermined. Chromosome numbers have been stated where known.
The descriptions are not always strictly comparable with regard to the attributes which are included. Many have been reduced to contain only the characters of most value in identification. This is because many characters in the Loranthaceae are uniform for most species of a genus, or for an entire genus or suite of related genera. For example, the great majority of species of Loranthaceae have opposite leaves, but in the genus Dendrophthoe alternate leaves predominate, and in the genus Amyema several species have verticillate leaves. Very considerable repetition in the species descriptions has been avoided by omitting to mention common states of particular attributes, and only the uncommon states are given. In such cases, however, the common attribute states are mentioned in the descriptions and discussions of the genera, which should be read in conjunction with the species descriptions.

The New Guinean species of some genera are no less difficult taxonomically than their Australian (Barlow 1966) or Indomalayan (Danser 1931, 1935) congeners (see below). The variability of many species has made it virtually impossible to produce comprehensive species descriptions which are still definitive, or keys that work for all specimens. The descriptions and keys therefore make allowance only for the most frequent variations within each species. For completeness, descriptions are given again for the relatively few taxa which also occur in Australia and have been described in the previous paper.

Notes on the occurrence of each species or subspecies include a statement of recorded geographical distribution illustrated by a spotmap drawn up from collection data. The broken lines on the spotmaps are included for ease of map reference and are not intended as accurate representations of geographic range. Statements on the ecological situation of each species include the available data on altitudinal range, which are often a good guide to the nature of the forest habitat. References to hosts have generally been omitted from the account, as they are of little ecological significance. This is because most tropical mistletoes occur in forests that have a large number of dominant tree species, and there is consequently very little host specialization.

Some observations on evolutionary trends and biogeographic history in the family have been published elsewhere (Barlow 1971b; Barlow and Wiens 1971, 1973), and further works are intended. It is felt that detailed discussion of phylogeny would be undesirable in this already long paper, and it has been avoided as far as possible. A conspectus of the genera has been given to indicate their probable relationships, and this has been used in determining the sequence of the genera. Within the genera, however, specific relationships are still not clear, and may often have a reticulate pattern. It is felt that attempts to arrange the species in a sequence intended to reflect their relationships would be of very doubtful value, and for this reason the species in each genus have been arranged alphabetically.

Criteria for the Distinction of Species and Subspecies

The general lack of high host specificity in tropical Loranthaceae implies the general absence of adaptation to the host as an ecological isolating mechanism. This is reflected in the very wide variability of many species, which is undoubtedly also maintained by a high degree of outbreeding. The species in this account have been circumscribed relatively broadly, in the belief that this accords with their biological situation. Many of the species described on the basis of a few early collections from New Guinea have been found to fall within the wide limits of variation of entities well represented in subsequent collections, and have been reduced to synonymy. Nevertheless, it has been necessary to distinguish several new species on the basis of one or a few collections because of their several very distinct or unique morphological characters.
In several cases it is possible to recognize distinct infraspecific entities, and these have been treated as subspecies. The geographical basis for their recognition is altitudinal in some cases; in others different areal patterns are involved.

FAMILY LORANTHACEAE JUSS.

Loranthaceae Juss. Ann. Mus. Hist. Nat. Paris 12: 292 (1808) ('Lorantheae'); D. Don, Prodr. Fl. Nepal. 142 (1825); Loranthaceae subfam. Loranthoideae Engl.Pfl. Fam. 3, 1:177 (1889); Engl.& Krause, Pfl. Fam. ed. 2 16b: 137 (1935). For other synonymy see Barlow, Proc. Linn. Soc. N.S.W. 89: 268 (1965).

Hemiparasitic terrestrial rootparasitic shrubs or trees, or more often aerial stemparasitic shrubs. Leaves mostly opposite. Flowers mostly more than 5 mm long, dichlamydeous, hermaphrodite or when unisexual mostly dioecious. Calyx reduced to a lobed or truncate limb at the apex of the ovary, without vascular bundles. Corolla choripetalous or gamopetalous, usually regular, 4 to 6 (to 9)merous, valvate. Stamens as many as and opposite the petals, epipetalous; anthers primarily 2 or 4locular (sometimes with transverse partitions), mostly basifixed, immobile and continuous with the filament but sometimes dorsifixed and then usually versatile, opening longitudinally; pollen mostly trilobate, rarely triangular or spherical. Ovary inferior, uni or plurilocular, with or without a central placental column (mamelon); ovules absent; sporogenous tissue massive, located in the mamelon or at the base of the ovarian cavity. Style and stigma simple. Fruit mostly baccate (rarely dry or drupaceous); yiscous layer (when present) outside the vascular bundles. Primary Basic Chromosome Number.-x =12.

A family of about 65 genera and 900 species, well represented in the tropics of both hemispheres and with fewer species in temperate regions. In the region considered here there are 12 genera. Only four are endemic, although another three genera have their major centres of development in the region. Most of the nonendemic genera extend westward in Indomalaya, and five of them also occur in Australia. Of the 59 species distinguished here 47 are endemic: only five species appear to be represented elsewhere in Indomalaya and nine species occur also in Australia.

Barlow Introduction

updated 20 January 2007