Ant Plants
Ant Plants (Myrmecophytes) and Myrmecophily
Myrmecophily describes the close ecological relationship between plants and ants. In these associations, plants provide ants with shelter or food, while benefiting in return through protection from herbivores, the input of nutrients, or the dispersal of their seeds. This symbiosis is most highly developed in myrmecophytic plants, commonly known as ant plants, which produce specialized hollow structures (domatia) that serve as nesting sites for ants. Such mutualistic relationships have evolved independently many times throughout evolutionary history and represent a striking example of convergent evolution. Myrmecophytic plants occur in the families Rubiaceae, Melastomataceae, Fabaceae, Polygonaceae, and Apocynaceae, the latter including the genera Dischidia and Hoya, as well as among the fern genera Platycerium, Lecanopteris, Microgramma, and Solanopteris. Depending on the plant lineage and habitat, the structure of the domatia, the associated ant species, and the ecological significance of the symbiosis vary considerably. Despite their independent evolutionary origins, all of these systems are based on a mutually beneficial relationship between plant and ant.
Anthorrhiza bracteosa (Normanby, PNG)
Anthorrhiza bracteosaAnthorrhiza bracteosa Huxley & Jebb is an epiphytic species of the family Rubiaceae, which is found on the D’Entrecasteaux Islands and on Woodlark Island in eastern Papua New Guinea. It grows in rainforests from sea level up to an altitude of approximately 1,600 m . On Normanby Island, it also colonises low-growing vegetation on nutrient-poor soils, where it grows alongside Anthorrhiza areolata and Hydnophytum species. The cavities of the caudex are only occasionally inhabited by ants, but more frequently by cockroaches, beetles and other invertebrates.Characteristic of the species is the flattened spherical to cylindrical, spine-less caudex with numerous small entry holes. The few square shoots bear lanceolate to obovate leaves. The species name bracteosa refers to the strikingly large, papery to leathery bracts, which largely cover the sunken inflorescences and constitute a unique identifying feature of the species. The flowers are white, the fruits red.
Anthorrhiza camilla (Garassa, PNG)
Anthorrhiza camillaAnthorrhiza camilla Jebb is an epiphytic species of the Rubiaceae family, known exclusively from the Morobe Province in eastern Papua New Guinea. It grows as a low-growing epiphyte in shady, moss-rich montane rainforests at altitudes of 1,600–2,000 m. Unlike the other heavily spiny species of the genus, it prefers to inhabit the interior of the forest and sheltered locations. The species was named after Camilla Huxley-Lambrick , who, together with M. H. P. Jebb, described the genus Anthorrhiza .A characteristic feature of the species is a spherical caudex densely covered with golden-brown, star-shaped, branched spines. The shoots, which are also heavily spined, bear narrow, lanceolate leaves arranged in a terminal rosette. The small, sunken inflorescences have papery bracts that fall off early – an important distinguishing feature from Anthorrhiza chrysacantha. The flowers are whitish-green with yellow anthers; the fruits are yellow-orange. Among the spiny species, A. camilla particularly A. chrysacantha, but it also differs in having shorter spines and smaller inflorescences.
Anthorrhiza chrysacantha (Mt Kaindi, PNG)
Anthorrhiza chrysacanthaAnthorrhiza chrysacantha Huxley & Jebb is an epiphytic species of the family Rubiaceae, found in the montane rainforests of Central and Eastern Papua (Papua New Guinea). It grows in disturbed Nothofagus forests at altitudes of around 1,200–2,200 m, usually high up in the canopy, and is frequently sympatrous with Anthorrhiza caerulea . The caudices are regularly colonised by the ant Iridomyrmex scrutator .A characteristic feature of the species is a flat caudex that lies close to the substrate, bearing dense, conspicuous golden-brown, multi-branched, star-shaped spines. As the plant matures, several sturdy, densely spined and branched shoots emerge from the caudex, bearing lanceolate to obovate, leathery leaves. The depressed inflorescences are surrounded by a narrow, spiny margin of tissue and bear white flowers with long, narrowly tapering corolla lobes. In comparison to A. caerulea A. chrysacantha larger, golden-brown spines, smaller leaves with less conspicuous venation, and white rather than turquoise-blue flowers. The fruits are spherical, yellowish-orange berries.This species is absolutely breathtaking!It forms huge plants that grow on isolated trees at the summit of Mt Kaindi in Papua New Guinea. At first glance, the plants appear very similar to Anthorrhiza caerulea, but they are much larger, and the leaves are smaller and not wavy. Furthermore, A. chrysacantha plants produce several shoots per plant. In my opinion, this species is in a league of its own alongside Myrmecodia lamii, Hydnphytum kajewskii and Squamellaria major when it comes to its bizarre appearance!
Anthorrhiza echinella (Perikles Pass, PNG)
Anthorrhiza echinellaAnthorrhiza echinella Huxley & Jebb is an epiphytic species of the family Rubiaceae, found in the montane rainforests of eastern Papua New Guinea. It grows at medium to high altitudes as an epiphyte on forest trees and forms a spherical, densely spiny caudex with a system of cavities inhabited by ants.A characteristic feature of this species is the grey caudex, up to about 25 cm wide, with numerous irregularly star-shaped branches of spines. The species name echinella is derived from the Greek echinos (‘sea urchin’) and refers to the strikingly spiny appearance of the caudex. The sparsely branched shoots bear large, lanceolate to obovate, dark green leaves with a distinctly prominent midrib. In contrast to most other spiny species of the genus, the spines on the shoots are largely confined to the inflorescences. The depressed inflorescences bear whitish-green flowers. The fruits are orange to red-coloured berries.
Anthorrhiza recurvispina (?) (Missima Island, PNG)
Anthorrhiza recurvispinaAnthorrhiza recurvispina Huxley & Jebb is an epiphytic species of the family Rubiaceae, found in the Louisiade Archipelago in eastern Papua New Guinea. It has been recorded on the islands of Misima, Rossel and Sudest and grows in lowland rainforests and open hillside woodlands from sea level up to an altitude of around 300 m. The species’ locus classicus is on Rossel Island. The plants usually grow singly or in small groups alongside Hydnophytum and are regularly colonised by the ant Iridomyrmex scrutator . With a caudex up to 35 cm in diameter, A. recurvispina one of the largest species in the genus. The population on Misima Island differs from the populations on Rossel in several morphological characteristics and may possibly represent a previously undescribed species.A characteristic feature of the species is the spherical to slightly flattened caudex with numerous hook-shaped, star-shaped spines, to which the species name recurvispina (‘with recurved spines’). The sturdy shoots bear large, ovate to obovate leaves with long petioles. In contrast to Anthorrhiza echinella , the caudex is only sparsely spined, has significantly more entry openings, and the smaller inflorescences bear a few sturdy, slightly curved spines. The flowers are white, the anthers strikingly blue, and the fruits are red.
Anthorrhiza recurvispina (Rossel Island, PNG)
Anthorrhiza recurvispinaAnthorrhiza recurvispina Huxley & Jebb is an epiphytic species of the family Rubiaceae, found in the Louisiade Archipelago in eastern Papua New Guinea. It has been recorded on the islands of Misima, Rossel and Sudest and grows in lowland rainforests and open hillside woodlands from sea level up to an altitude of around 300 m. The species’ type locality is on Rossel Island. The plants usually grow singly or in small groups alongside Hydnophytum and are regularly colonised by the ant Iridomyrmex scrutator . With a caudex up to 35 cm in diameter, A. recurvispina to the largest species in the genus.A characteristic feature of the species is the spherical to slightly flattened caudex with numerous hook-shaped, star-shaped spines, to which the species name recurvispina (‘with recurved spines’). The sturdy shoots bear large, ovate to obovate leaves with long petioles. In contrast to Anthorrhiza echinella , the caudex is only sparsely spined, has significantly more entry openings, and the smaller inflorescences bear a few sturdy, slightly curved spines. The flowers are white, the anthers a striking blue, and the fruits are red.
Hydnophytum cf. petiolatum (heavily thickened nodes, unknown origin)
This lovely species belonging to the Hydnophytum petiolatum group. Its thickened nodes (leaf joints) are particularly striking.New!
Hydnophytum dentrecastense (Normanby Island, PNG)
Hydnophytum dentrecastenseHydnophytum dentrecastense Jebb & C.R. Huxley is a terrestrial species of the family Rubiaceae, known exclusively from Normanby Island in the D’Entrecasteaux Archipelago (Papua New Guinea). It inhabits open woodlands and scrub on ultramafic soils at altitudes of approximately 400–600 m. The cavities in the caudex are not colonised by ants, but often contain rainwater and are regularly inhabited by cockroaches.A characteristic feature of this species is the relatively small, irregularly spherical caudex with strikingly large, conical entry openings. The shoots are quadrangular and bear lanceolate leaves with a strikingly silvery-green upper surface and distinctly rolled-back leaf margins. The inflorescences, arranged in pairs, are sessile to short-stalked and bear white, heterostylous flowers with a ring of hairs at the throat of the corolla tube. The fruits are small, red berries. The combination of quadrangular shoots, the silvery-green upper leaf surface, the rolled-back leaf margins and the large entry openings of the caudex constitutes the most important identifying characteristics of the species.In cultivation, the plants grow well in coarse peat substrate, although in the wild they have been found on ultramafic soils.
Hydnophytum ferrugineum (Australia)
A relatively new species from Australia.
Hydnophytum mamberamoense (or related species - possibly new genus)
I believe, this is the elusive Hydnophytum mamberamoense or a related species. Unfortunately, the type specimen is quite incomplete, so I am a bit reluctant to call it H. mamberamoense.However having seen the species in the field, I am quite sure that this is neither a Hydnophytum, nor a Myrmecodia but rather belongs into a yet to be described new genus of Hydnophytinae!This strange species from the southern coast of Irian Jaya does not really fit into any of the other genuses of Hydnophytinae. At first sight, the caudex looks Myrmecodia-like but appears to be less organanized and very irregular. The inflorescence does not fit into Myrmecodia either. Very interesting!
Hydnophytum moseleyanum Type 1 (Wasior, Irian Jaya)
The caudex of this form is significantly flatter than that of Hydnophytum moseleyanum Type 2 (Wasior, Irian Jaya) and has numerous small openings.
Hydnophytum moseleyanum Type 2 (Wasior, Irian Jaya)
Unlike Type 1 from the Wasior area, this type has a more upright caudex with larger holes and darker, glossier leaves. Quite atypical for Hydnophytum moseleyanum!
Hydnophytum radicans (flat caudex)
This form is characterised by its rather flat caudex in old age.In Jebb's monograph, a large number of forms are grouped together under Hydnophytum radicans, which were originally described as separate species. This underlines the wealth of forms in this interesting group!
Hydnophytum radicans (lowlands, PNG, border region with Irian Jaya)
Hydnophytum radicansHydnophytum radicans Becc. is an epiphytic species of the family Rubiaceae, found in the lowland rainforests of New Guinea. It grows on tree trunks and branches in humid forests and forms a tuber-like caudex with a branched system of cavities. Unlike many other members of the Hydnophytinae, the cavities are predominantly inhabited not by ants, but by various invertebrates and, occasionally, small reptiles.Characteristic features of H. radicans are the round, unbranched shoots, the large, broadly elliptical to obovate, leathery leaves with a distinctly prominent midrib, and the paired, profusely branched inflorescences. These highly branched inflorescences are the most important identifying feature of the Radicans group within the genus Hydnophytum.A lowland form of this fairly widespread and highly variable species.
Hydnophytum radicans (Mt. Hagen, Papua New Guinea)
A highland form of this fairly widespread and highly variable species.The stems of this highland form are significantly thicker and fleshier than other forms I have seen so far.The inflorescences of this form are directed upwards towards the tip of the shoot.
Hydnophytum radicans (Timika, Irian Jaya)
Hydnophytum radicansHydnophytum radicans Becc. is an epiphytic species of the Rubiaceae family, found in the lowland rainforests of New Guinea. It grows on tree trunks and branches in humid forests and forms a tuber-like caudex with a branched system of cavities. Unlike many other members of the Hydnophytinae, the cavities are predominantly inhabited not by ants, but by various invertebrates and, occasionally, small reptiles.Characteristic features of H. radicans are the round, unbranched shoots, the large, broadly elliptical to obovate, leathery leaves with a distinctly prominent midrib, and the paired, profusely branched inflorescences. These highly branched inflorescences are the most important identifying feature of the Radicans group within the genus Hydnophytum. Another characteristic of some specimens is the formation of small secondary caudices along the roots, which allows the plant to spread vegetatively.Plants of this form appear to be particularly well-adapted to dry periods, and the caudex shrinks drastically during drought, so that the plant appears almost dead. The unripe berries remain orange for a long time and only turn red when fully ripe. The leaves are relatively large, leathery and always hang down. The inflorescences are extremely compact and the caudex is rather small.Another interesting feature of this form is that the aforementioned daughter tubers can form on the roots!
Hydnophytum spec. D (spathulatum group, Moluccas)
A whole series of extremely interesting and attractive Hydnophytum species have been found in the Moluccas in recent years, all of which fit roughly into the concept of Hydnophytum spathulatum. In the end, I think the whole group around Hydnophytum ovatum (which also includes H. spathulatum) should be revised in order to clarify the situation. Unfortunately, the exact origin of many collections is unclear.This species is extremely peculiar. The caudex of older plants is very finely ribbed, almost black and the shoot is strongly winged. In younger plants, fine warts predominate on the caudex.The berries are very small. The leaves have extremely fine velvety pubescence.I think this is one of the most interesting species to come into cultivation recently.
Hydnophytum spec. Malaybalay (Mindanao, Philippines)
Beautiful dark green, glossy leaves. The caudex is strikingly ribbed and covered in numerous warts. Judging by its growth habit, one might mistake this lovely species for a highland variety.Very attractive and easy to care for! However, the species grows rather slowly.
Hydnophytum spec. Malaysia, Peninsula
This is a beautiful small growing species. The plants form cushion-shaped caudices and dense small bushes. Highly recommended!
Hydnophytum spec. roundish caudex (Wondiwoi, Irian Jaya)
Very vigorous intermediate species.It bears a certain resemblance to the Hydnophytum radicans group, but is much smaller than all other members of the group known to me. The caudex is elongated when young and becomes rounder with age, with very conspicuous, large, edged holes.A beautiful species!As it is very vigorous, it is advisable to prune the branches from time to time.
Hydnophytum spec. shiny lanceolate leaves "M" (Nabire, Irian Jaya)
A very nice new introduction from the area near Nabire on the north coast of Irian Jaya.The plants have shiny lanceolate leaves and a rather irregularly shaped caudex. The branches and internodes are quite long.
Hydnophytum spec. Small Leaves, Siasiada
A very attractive new introduction. The plants form numerous wiry shoots with small heart-shaped leaves. The species occurs in the lowlands on a fairly low hill near Siasiada Village (Milne Bay) in Papua New Guinea.
Hydnophytum spec. Timika (wavy embossed leaves)
A very beautiful species with strangely uneven embossed to wavy leaves and slight pubescence.
Hynophytum spec. Doormans Top 1200m (narrow, tapering leaves)
Very nice! A spherical caudex and tapering, leathery leaves. The plant is considerably more compact than the species found at 1,000 metres, which also has significantly narrower leaves.