27 species are endemic to the New Guinean mainland. Plants with photographs shown with a red asterisk (*).
Description from Barlow (1992)
Amyema Tieghern, Bull. Soc. Bot. France 41 (1894) 499. - Type: Amyema congener (Sieber ex Schultes & Schultes f.) Tieghern (lecto, designated by Barlow, Austtal. 1..Bot. 14, 1966, 452).
For descriptions and extensive synonymy see Danser, Bull. Jard. Bot. Buitenzorg III, 11 (1931) 318; Philipp. J. Sci. 58 (1935) 61; Barlow, Austral. J. Bot. 14 (1966) 452; ibid. 22 (1974) 561. Danser's descriptions do not cover the species he placed in Dicymanthes, which he treated as a distinct genus (see below).
A genus of 92 species distributed from the southeast Asian mainland to Australia and islands of the southwestern Pacific. Representation in southeast Asia is limited to a single species which occurs in Malaya and Thailand, and species richness increases eastwards from Sumatra and Borneo to the Philippines, and southwards to New Guinea and Australia, where most of the species are found. A few species extend into the Pacific, one reaching the Caroline Islands and Samoa.
The species are found in a wide range of habitats from closed humid forests to arid woodlands, with a correspondingly wide range of adaptive structural and physiological variations. Attachment to the host can be through secondary haustoria on extensive epicortical runners, or only through simple or complex primary haustoria which sometimes have longitudinal strands in the cortical or cambial layers of the host sterns. Leaf architecture varies from a simple bifacial pattern with pennate venation to thick isobilateral curvinerved leaves. Variations in inflorescence and flower structure apparently related to pollination and to protection from predation are numerous. Host specificity ranges from very low (usual in rain forest species) to very high (common in open and arid woodlands), and when high may be associated with remarkable vegetative mimicry of the host.
Infrafamilial classification of Loranthaceae is based mainly on ovary and seedling characters, but is seriously in need of revision. As a member of the informal group L31-39 'Amyemae' (Barlow et al., 1989), Amyema is characterized by an almost completely undifferentiated ovary with ovules totally absent (Maheshwari et aI., 1957; Bhatnagar & Johri, 1983), cotyledons not emerging on germination, and very large chromosomes (x = 9). Most of the readily observable external characters are derived from inflorescence and flower structure.
The basic inflorescence unit (uniflorescence) in Amyema is a simple dichasium (triad). The triads are often aggregated into conflorescences, and the plesiomorphic state for the genus is probably an axillary multi-rayed umbel of triads, which in tum may be a reduction from the raceme with whorls of triads which occurs in the related genus Dactyliophora Tieghem (Barlow, 1966, 1974, 1990). Vestigial structures and occasional aberrant developments indicate that the simpler inflorescence types which occur in some species of Amyema are derived by reduction. These include simple umbels (by reduction of triads to single flowers), umbels of dyads (through loss of the central flowers of the triads), capitula (through shonening of the umbel rays and flower pedicels), and solitary flowers.
The flowers in Amyema are hermaphrodite, 4- to 6-merous, and basically choripetalous, although in some species the petals remain coherent in the lower pan for some time after anthesis, and in some cases even are shortly fused. The epipetalous stamens have basifixed, immobile, introrse anthers with simple filaments.
Vegetative features are diverse. Phyllotaxy may be decussate, scattered or verticillate, or a combination of these. The leaves are simple, petiolate or sessile, bifacial or isobilateral, with penninerved to curvinerved venation. There is a general correlation between haustorial structure and habitat, the species of dense humid forests usually being scandent, having long epicortical roots (runners) which produce haustoria and new leafy stems, whilst species of open semi-arid communities often have only the primary haustorium, which may be structurally complex, sometimes producing strands which spread in the cambial or cortical zones of the host.
Amyema is the largest genus in its group, and one of the largest in the family. Most of the related genera are small, more homogeneous, and apparently derived. They are mostly sympatric with Amyema and are usually characterized by inflorescence and flower specializations which are probably adaptations for protection and pollination. In this sense, Amyema represents the core of variability of its subfamilial group, from which a number of satellite genera have differentiated.
Only two small genera in the group are possible exceptions to this pattern. Dactyliophora, a genus of two species in Papuasia, is probably close to the stem of the amyemoid stock, differing only in its more complex and possibly ancestral conflorescence structure (Barlow, 1974, 1990). The monotypic genus Cecarria, of eastern Malesia and northeastern Australia, exhibits some character states which are probably plesiomorphic for the family, and is probably a relict of the early Gondwanan history of the family (Barlow, 1983).
All of these other amyemoid genera will be discussed in more detail separately.
The loranths presumably originated in the mesic, warm to mild, closed forests of Gondwanaland, the parasitic habit arising not in response to water stress but to competition for nutrients in complex ecosystems. Four main lines of evolution apparently occurred independently in the Afro-Indian, Indian-Indosinian, Australasian-Papuasian, and South American regions of Gondwanaland, from genomically different basal stocks, and were isolated by the fragmentation of the supercontinent (Barlow, 1990). The Australasian-Papuasian line is represented by the amyemoid group of genera.
In Amyema there is considerable morphological diversity in New Guinea, including a significant retention of plesiomorphic characters. The origin of the genus was probably in mesic forests at the northern margin of the Australian tectonic plate, followed by radiation into areas of seasonal, arid and subalpine climates as they appeared. The species of Amyema which occur to the north and west of Charles's Line are presumably derived from stocks which reached there from an Australian-Papuasian source subsequent to the late Tertiary contact of the Australian and Sunda plates.
Like all loranths, dispersibility in Amyema is low, and the spread of the genus across Malesia to the Asian mainland has probably been mostly over exposed land surfaces. Although the convergence of the Australian and Sunda plates began in the mid-Miocene, it was probably not before latest Miocene or early Pliocene that a land migration route from Australia and New Guinea to Celebes and the Philippines was established (Audley-Charles, 1981). By the late Pliocene, lowered sea levels would have exposed extensive land on both sides of the contact boundary and dispersal of Amyema would have been facilitated.
Present-day species richness suggests that the eastern mesic forest block from New Guinea to the Philippines has been the main corridor for migration and speciation of Amyema in Malesia. There is a rapid decline in species numbers to the west, and many of the species represented there are widespread, occurring on more than one island. As in the genus Scurru/a (Barlow, 1991) the widespread species are lowland ones for which sea level minima could have provided migration opportunities. Many of the local endemics, especially in the Philippines, are derived upland species.
The few small, morphologically specialized genera which are derived from the amyemoid stock are all centred in New Guinea. They include Distrianthes (1 sp.), Papuanthes (1 sp.) and Sogerianthe (5 spp.). They are probably no older than the vertical uplift which has followed the emplacement of exotic terranes on the New Guinean margin of the Australian plate (Barlow, 1990). Whilst perhaps younger than the Miocene collision with Sundaland, they are Gondwanan in derivation and belong with the autochthonous subelement of the Australian flora.
In a genus as large as Amyema it would be usual for subgenera or sections to be distinguished. Recognition of such taxa would be a good indicator of phylogeny and species relationships. However, it is highly likely that any species groups distinguished on the basis of the morphological characters used in this study would be polyphyletic (see notes on Dicymanthes, for example). The Australian species, occupying perhaps the oldest pan of the territory of the genus, are mostly derived taxa adapted to the now extensive seasonally dry and arid environments, and have probably been derived in parallel from different ancestral groups of the primitive mesic forests. The secondary diversification of the genus in Malesia has probably also involved parallel development in different immigrant stocks. Infrageneric taxa have consequently not been distinguished, and the species have been arranged in alphabetical order. Notes on relationships, both phyletic and biogeographic, are given for species wherever possible.
The information sources for the study of the Malesian taxa have been herbarium specimens and earlier taxonomic concepts, notably those of Danser. In this respect, species circumscription employed here is conventionally morphological. However, earlier work on the Australian and New Guinean taxa has been based on extensive field work, supported by data on chromosome numbers and karyotype, pollination biology and genetic system. Field observations have contributed to knowledge of the dynamics of local populations and of hybridization. This experience has been used as a comparative base for the assessment of systematic status of the Malesian entities.
Herbarium material was assembled and sorted geographically for examination, if necessary with secondary altitudinal sorting. Among the sympatric entities so assembled for each area, internally homogeneous and distinct taxa were recognized as species. As in most large angiosperm genera, variability in Amyema is greatest in widespread lowland species, and application of taxonomic judgement was therefore most critical in the matching of the entities of adjoining geographic areas in order to determine the extent of conspecificity.
Satisfactory conclusions about con specificity of entities in different islands should take account of geophysical and palaeoclimatic history. For Amyema and other Loranthaceae, Danser's taxonomic concepts must be reviewed against this background. Danser made important theoretical contributions to the species concept, but in applications in his own systematic work he was probably influenced by contemporary views on historical biogeography of the Malesian region. He frequently accepted different species for each of the major islands of the region, often based on small quantitative differences, whereas our present knowledge of the amplitude and frequency of coastline and climate changes might have led him to different conclusions. The geographical integrity of a Malesian species, especially a lowland one, is not weakened by its occurrence on a number of islands, even when dispersibility is low. Application of taxonomic judgement based on experience with the family is most critical, therefore, in assessing the significance of morphological differences in isolated populations in terms of the most recent interruption to gene flow between them. Where entities on different islands are obviously very closely related and show quantitative character differences which may relate to local environment, both physical and biotic, I consider it preferable to treat them as conspecific.
In earlier work on the Australian species of Amyema, I recognized subspecies within a number of widespread species. These subspecies are ecogeographically discrete entities which are probably an outcome of the clinal differentiation which can occur in open vegetation systems in such a large land area. A few varieties have also been recognized to account for striking morphological variants lacking geographic or population integrity.
Differentiation of subspecies appears to be less usual in humid ttopical ecosystems. Further observation suggests that some of the subspecies I recognized in earlier work on New Guinean species may not have a sound biological basis. In this conspectus reference is given to the existence of subspecies, where appropriate, but emphasis is given primarily to the delineation of species. The only exception is in A. miraculosa, where well-defined subspecies already exist in Australia and the taxon in Timor must be placed in context with them.
Gender of Amyema
In his description of the genus, Van Tieghem (1894b) cited a derivation from the Greek a ('privatif') and m n e w ("j'enseigne") = "non encore enseigne." Van Tieghem had synthesized other genus names from Greek word roots, and apparently believing that he had done so in the case of 'amyema', accordingly determined the gender as feminine. In accordance with Article 76 of the International Code of Botanical Nomenclature, adopted in August 1987, the name retains the gender assigned by Van Tieghem, and in this treatment the adjectival epithets cited are accordingly feminine.
There is a word in classical Greek which on transliteration is 'amyema' and which means "those not yet initiated in eleusinian mysteries." The word is clearly derived from the same root as Van Tieghem used. Whilst Van Tieghem was undoubtedly an accomplished Greek scholar, and his intention in formulating the name and applying a gender can hardly be challenged, I have previously treated the genus name Amyema as neuter because of the existence of the Greek word, not noticed by Van Tieghem, with meaning conforming with that given by him. In so doing I followed a Recommendation which was valid at the time but which is now superseded.
Status of Danser's genus Dicymanthes
Numerous genus names attributable to Van Tieghem and other authors, and now placed in synonymy under Amyema, are reviewed and listed in earlier works (Danser, 1933; Barlow, 1974), and need no further discussion here. An exception is Danser's genus Dicymanthes, first placed in synonymy with Amyema by Barlow (1974). Most of the Malesian species placed by Danser in Dicymanthes appear to form a natural group, striking because of the capitate inflorescence formed from two sessile triads. However, the condensation of a two-rayed umbel of triads into a head through reduction of the rays is not a major variation in the genus, and is probably less significant than some of the other variations in inflorescence structure. Acceptance of a genus based on this character would remove the integrity of the residue left in Amyema.
In any case, the inflorescence structure in Dicymanthes is most probably polyphyletic. In addition to the Malesian species referred to above, it occurs in A. maidenii of arid and semi-arid Australia, and in A. tetrapetala of New Guinea, which Danser included in Dicymanthes. It also occurs in the related Australian genus Diplatia which is further distinguished by some highly specialized bract characters. Other species in Malesia show inflorescence reductions which closely approach Dicymanthes. All of these species have characters which suggest that they are not directly related to the core group of the genus. Dicymanthes is therefore retained in synonymy with Amyema. For further notes on the lack of a sharp discontinuity between Dicymanthes and Amyema, see note under A. tristis.
Generic Description from Barlow (1974)
Amyema Tiegh. Bull. Soc. bot. Fr. 41: 499 (1894); Dans. Bull. Jard. bot. Buitenz. 10: 293 (1929); 11: 318 (1931); Barlow, Aust. J. Bot. 14: 452 (1966); Loranthus sect. Amyema (Tiegh.) Engl. Pfl. Fam. Nachtr. 127 (1897); Blakely, Proc. Linn. Soc. N.S.W. 47: 391 (1922); Engl. & Krause, Pfl. Fam. ed. 2 16b: 149 (1935). Type Species-A. congener (Sieb. ex Schult. & Schult. f.) Tiegh. (lectotype, Barlow 1966).
Pilostigma Tiegh. Bull. Soc. bot. Fr. 41: 483, 488 (1894); Barlow, Proc. Linn. Soc. N.S.W. 87: 56 (1962); Loranthus sect. Pilostigma (Tiegh.) Engl. Pfl. Fam. Nachtr. 128 (1897); Engl. & Krause, Pfl. Fam. ed. 2 16b: 151 (1935). Type Species-P. sanguineum (F. Muell.) Tiegh.
Stemmatophyllum Tiegh. Bull. Soc. bot. Fr. 41: 499, 505 (1894); Loranthus sect. temmatophyllum (Tiegh.) Engl. Pfl. Fam. Nachtr. 128 (1897); Engl. & Krause, Pfl. Fam. ed. 2 16b: 150 (1935). Type Species-S. luzonensis (Presl) Tiegh.
Neophylum Tiegh. Bull. Soc. bot. Fr. 41: 499, 508 (1894); Loranthus sect. Amyema subsect. Neophylum (Tiegh.) Engl. Pfl. Fam. Nachtr. 127 (1897); Engl. & Krause, Pfl. Fam. ed. 2 16b: 150 (1935). Type Species. N. scandens Tiegh. (lectosyntype selected from 13 species cited by Van Tieghem).
Rhizanthemum Tiegh. in Morot, J. de Bot. 15: 364 (1901). Type Species.-R. celebicum Tiegh.
Cleistoloranthus Merr. Philipp. J. Sci. 4:150 (1909). Type Species. C. verticillatus Merr.
Xylochlamys Domin, Bibl. Bot. 89: 56 (1921); Barlow, Proc. Linn. Soc. N.S.W. 87: 56 (1962). Type Species.-X. queenslandica Domin.
Dicymanthes Dans. Bull. Jard. bot. Buitenz. 11: 362 (1931); Loranthus sect. Ligulati Engl. & Krause, Pfl. Fam. ed. 2 16b: 147 (1935). Type Species.- D. caulfiora (Merr.) Dans.
Ungula Barlow, Proc. Roy. Soc. Qd. 75: 17 (1964). Type Species-U. tetraflora Barlow.
For further synonymy see Danser (1929, 1931).
Aerial stem-parasitic shrubs with or without runners (with runners in most of the species dealt with here); leaves opposite or verticillate (rarely scattered), penninerved to curvinerved. Inflorescences axillary, rarely internodous or in some species arising from the runners, consisting primarily of a pedunculate many-rayed umbel of dichasia (triads), but showing various kinds and degrees of reduction in some species (see Barlow 1966, Fig. 5); bracts single under each flower (rarely more in reduced inflores-cences). Corolla usually 4-, 5- or 6-merous; open flower actinomorphic, usually choripetalous but rarely gamopetalous in the lower part. Anthers basifixed, immobile, 2- or 4-locular; pollen trilobate. Style usually articulate at the base. Basic Chromosome Number.- x = 9.
A genus of about 90 species, ranging from Malaya and the Philippines to Australia and the western Pacific, the main centres of development being New Guinea and Australia. Of the 29 species dealt with here, 21 are endemic to the New Guinean mainland.
In a note preceding the treatment of the Australian species of Amyema (Barlow 1966), it was suggested that the delimitation of infrageneric taxa might be possible after full examination of the New Guinean material. The additional studies on the genus have confirmed that some species groups are distinct, and could perhaps be placed in separate sections or subgenera. They are characterized in the main by inflorescence reductions (to simple umbels, solitary flowers or capitate inflorescences) and in other cases by gamopetalous corollas. Nevertheless, it now seems that the recognition of infrageneric taxa would have little value, and such categories have therefore not been distinguished. Most of the categories which could be distinguished would be very small, and would represent extremes of variation in the genus, so that a single large typical subgenus or section would still remain. Furthermore, it is unlikely that many of the most readily circumscribed segregate taxa would be natural. Among the species with capitate inflorescences, for example, there are no indications that A. tetrapetalum (New Guinea) is closely related to A. maidenii (arid Australia), or to the Malesian species formerly placed in Dicymanthes. The Australian species with simple umbels, previously placed in the genus Pilostigma (Barlow 1962), do not appear to be closely related to the A. seemenianum-A. fasciculatum group from Cape York Peninsula, New Guinea and the Philippines.
Of the species with gamopetalous corollas, A. brassii and A. tetraflorum of New Guinea appear to have little else in common with the gamopetalous Philippine species. The author has previously taken the view (Barlow 1966) that the gamopetalous species could not be retained in Amyema. From the present study I have concluded that the few gamopetalous entities represent extremes of specialization of the Amyema stock, and that their generic distinction would have little merit. See note under A. brassii.
For other notes on Amyema, see Barlow (1966). See also note under Dactyliophora.
Amyema genus page
updated 22 January 2007