Palm Articles   Spiny Palms

As a group of plants, the spiny palms can specifically be regarded as those palms which have true spines on either or both the trunk and leaves - which excludes leaf-bases, petioles, rhachis and leaflets - and for most cases having spines on the flowering parts - including bracts, spathes, seed stalks - and in a few cases even the fruits (Astrocaryum and Acrocomia species). They have no botanical standing as a related group, even though the spiny palms are restriced to only three sub-families within the Arecacea, namely the Oncosperma alliance of the Arecoids, the Bactris alliance of the Cocoids and the Calamus , Salacca , Eugeissona and Korthalsia alliances of the Lepidocaryoid Palms.

True spines, as opposed to the spikes, needles and teeth of the Fan Palms, have developed only on pinnate leaved palms. They are independant lignified epidermal outgrowths, some-what like a human hair or fingernail, composed of cells which differ from the surrounding tissue's cells in which they are embedded and from which they project. They can be isolated growths appearing at random, singularly or in patterns of circles or whorls, pointing upwards or downwards. At their first emergence, they contain moist vascular cells but as the spines reach their maximum length, they dry up and become hard and in many cases brittle. Their growth is basal as are all other parts of palms.

They take a few basic forms. The typical spine is circular in cross-section, straight, tapering to a very sharp point, varying in length from under one centimetre to over fifteen centimetres (Aiphanes ). Some species of the Bactris alliance (Astrocaryum and Acrocomia in particular) have two sided blade-shaped spines on their trunks and flower spathes.

Many of the spiny climber's spines are united at the base to form a crest and in species of Plectocomia and Daemonorops in particular may be large enough to encircle the stem or petiole.

As an impliment of armament, the spines are potentially used as a protective device to ward off herbivores which may find the apical growths to their liking as well as to guard the ovules, pollen and seeds from the same or similar herbivores. The spines may also help in camouflaging insects which may be carrying out pollination for the palms - a symbiotic exchange for a safe home or breeding ground.

Oddly enough, there are no Fan Palms which have true spines on either the trunks or leaves. Their spines (or should they be referred to as spikes, needles or teeth?) are usually an appendage, mainly a leaflet, which has been reduced or transformed into a sharpened object, for example, the petiole spines (teeth) of Livistona or Washingtonia are more than likely leaflet's midveins which have either not developed or have been reduced sometime in their evolutionary past. In fact all the teeth, bumps and other projections on the edges of the petioles, leaf-bases and lamina edges of the Fan Palms bear some relationship to the formation or reduction of leaflets whether to be developed or reduced within their next evolutionary stage.

The other spines (?) of Fan Palms, those projecting from the trunk (Zombia ) and from the leaf bases (Rhapidophyllum ) are the remnants of the vascular fibres which once made up parts of the supporting structures of the leaf-bases. When the old leaves eventually fall, these skeletal structures remain behind still attached to the trunk.

The Fan Palms are a recent development in plant form. Very few of them have been immortalised in stone as fossils, being sparsely found in the Eocene deposits of 65 million years ago, whereas the Pinnate Palms history can be traced back to the Upper Cretaceous Period of 136 million years ago and possibly the Jurassic of 195 million years ago. We may presume therefore that the spiny palms are dramatic variants of the descendants of an ancient pinnate leafed form, having developed their spines as a response to the needs of survival, a response which has proven successful to their continued existence.

Their geographical distribution is mainly restricted to islands, as are most palms. The Islands of the West Indies and nearby continental Central and South America (Aiphanes, Acrocomia Bactris Gastrococos Astrocaryium and Desmoncus). The Islands of the Western Indian Ocean - Maruitius (Tectiphiala and Acanthophoenix ) the Seychelles (Phoenicophorium , Nephrosperma , Deckenia , Verschaffeltia Roscheria and Acanthophoenix ), Sri Lanka (Oncosperma and Calamus ), Malay Archipelago (Oncosperma , Calamus , Korthalsia , Salacca , Eugeissona , Daemonorops , Cornera , Myrialepis , Plectocomia andPlectocomiopsis ), Australasia (Calamus and Schizospathe ) and West Africa (Ancistrophyllum ).

Of particular interest from an evolutionary standpoint, is that no spiny members of the Arecoids are found east of Wallaces' Line. In 1867, Alfred Russel Wallace, a co-author of the theory of evolution with Charles Darwin, proposed a line of demarcation, the theory of which was based on the now proven fact that the Malay Archipelago is divided into two distant biospheres of evolutionary action. There are some overlappings of genera, mainly the flora (consider Calamus of the Lepidocaryoids) but generally there is quite a distinct difference between the adjoining areas. The "Line" extends northward from east of Bali, between Borneo and Sulawesi, to east of the Philippines.

To confuse things a little, the Lepidocaryoids have some genera which straddle Wallaces' Line - these being Calamus Korthalsia and Daemonorops but most of the spiny Lepidocaryoid genera do not extend eastward of the "Line", these being Salacca , Eugeissona , Plectocomia , Plectocomiopsis , Ceratolobus , Myrialepis and Cornera , with the exception of Salacca and Eugeissona all being climbing palms.

The islands of the Malay Archipelago are the centre of the Arecoid Palm evolution in the Eastern Hemisphere. Stretching westward from the Philippines, through Indonesia and Malaysia, to Sri Lanka, the Seychelles, to terminate in Mauritius, is an imaginary path through which the palms have migrated westward from this centre. Other unique plant groups are also found on this westward directed path. For example, the Pandanus - they reach most prolific numbers in south-east Asia but there are outpost species in the Seychelles, the Mascarene Islands and one solitary species in Madagascar. Exactly the same can be said of the Nepenthes (Carnivorous Pitcher Plants) with approximately 70 species centred in Borneo (30 species) there is but a single species in Sri Lanka (Nepenthes distillatoria ) the Seychelles (N. pervillei ) and Madagascar (N. madagascariensis ). Orchids of the Vandeae Tribe centred in the Malay Archipelago have outpost genera in Sri Lanka (Vanda and Rhyncostylis ) the Seychells (Oeoniella ) and Madagascar and adjacent islands (Aeranthes ), but the ability of the orchids to adapt and diversify is much greater than Palms which has resulted in large numbers of species within each genus.

But to return to palms - the unique features displayed by the spiny palms of the Seychelles and Mauritius are a fantastic evolutionary jigsaw puzzle. We can only wonder how such diverse growths have evolved from what must have been a single species (?) similar to the modern Oncospermas becoming isolated by rising waters and having to settle down to compete with the other forms of flora for survival. It can be said that the Palms of the Seychelles are what turtles are the Galapagos Islands.

To find the evolutionary centre of the spiny Cocoid palms in the western Hemisphere is not as straightforward as in south-east Asia. There is one very large genus, Bactris with around 240 species, three smaller ones but still large by palm standards, Aiphanes with 38 species, Astrocaryum with 47 speices, Acrocomia with 26 species, one monotypic genus, Gastrococos which is very closely related to Acrocomia and Desmoncus the climbing palms, with 40 species. It would be suspected that they originated in a continental area, perhaps Costa Rica or Venezuela, and from there migrated to the numerous islands within the West Indies where they developed there specific characteristics and peculiarities.

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