Aiphanes
Aiphanes is a genus of spiny palms which is native to tropical regions of South and Central America and the Caribbean. There are about 26 species in the genus, ranging in size from understorey shrubs with subterranean stems to subcanopy trees as tall as. Most have pinnately compound leaves ; one species has entire leaves. Stems, leaves and sometimes even the fruit are covered with spines. Plants flower repeatedly over the course of their lifespan and have separate male and female flowers, although these are borne together on the same inflorescence. Although records of pollinators are limited, most species appear to be pollinated by insects. The fruit are eaten by several birds and mammals, including at least two species of amazon parrots.
Carl Ludwig Willdenow coined the name Aiphanes in 1801. Before that, species belonging to the genus had been placed in Bactris or Caryota. The name Martinezia had also been applied to the genus, and between 1847 and 1932 it was generally used in place of Aiphanes. Max Burret resurrected the name Aiphanes in 1932 and laid the basis for the modern concept of the genus. Aiphanes is most closely related to several other genera of spiny palms—Acrocomia, Astrocaryum, Bactris and Desmoncus. Two species are widely planted as ornamentals and the fruit, seeds or palm heart of several species have been eaten by indigenous peoples of the Americas for millennia.
Description
Aiphanes is a genus of spiny palms ranging from tall subcanopy trees to small shrubs with subterranean stems growing in the forest understorey. Its name combines the Ancient Greek ai, meaning "always", with phaneros, meaning "evident", "visible" or "conspicuous". In their 1996 monograph on the genus, botanists Finn Borchsenius and Rodrigo Bernal pointed out that "ironically, species of Aiphanes are generally very hard to spot and find in dense vegetation and, accordingly, are among the most poorly collected neotropical palms".Stems
While some species are single-stemmed, others form multi-stemmed clumps. Coupled with variation in stem size, this produces a diversity of growth forms in the genus—solitary palms that grow into the subcanopy of the forest, solitary or caespitose palms that grow in the forest understorey and acaulescent palms which lack an aboveground stem.Two species are characterised by an acaulescent growth habit—A. acaulis and A. spicata. Two other species—A. ulei and A. weberbaueri—occur in both acaulescent populations and those which produce above-ground stems. Several species are single-stemmed understorey palms, an unusual growth form. Aiphanes grandis and A. minima are single-stemmed palms which grow to be more than tall, while the remainder are multi-stemmed understorey species. Multi-stemmed palms range from plants with a single main stem and a few basal suckers to caespitose clumps of 20 densely packed stems. A variety of growth forms can exist within a single species and this appears to be influenced by habitat and environmental conditions.
Leaves
The leaves of Aiphanes species are usually pinnately divided—rows of leaflets emerge on either side of the axis of the leaf in a feather-like or fern-like pattern. The sole exception to this is A. macroloba which has entire leaves. They are usually spirally arranged, but some species have a distichous leaf arrangement, a condition that is normal in palm seedlings but uncommon among adults. Old leaf bases detach cleanly from the stem, except in A. hirsuta subsp. fosteriorum, which often has old leaf bases attached to the newer portions of the stem.Leaves are spiny but the degree varies both within and among species. Leaf sheaths are always densely spiny, but the spines usually become smaller and sparser towards the ends of the leaves.
Spines
are characteristic of Aiphanes and other members of the subtribe Bactridinae. They are found almost everywhere on the plants and are especially well-developed on the stem, leaf bases, and the peduncle. In Aiphanes, the spines are formed from the outer tissues of the plant and are not derived through the modification of other plant organs. They range from less than to more than long.Flowers
Aiphanes species are pleonanthic—they flower repeatedly over the course of their lifespan—and monoecious, meaning that there are separate male and female flowers, but individuals plants bear both types of flowers. In Aiphanes, male and female flowers are borne together on the same inflorescence. Usually only a single inflorescence is borne at each node, although A. gelatinosa often bears then in groups of three at a single node. The inflorescence usually consists of a main axis consisting of a peduncle and a rachis. The rachis bears rachillae, which are smaller branches which themselves bear the flowers, while the peduncle is the main stalk connecting the rachis with the stem of the plant. In some species there is second-order branching—the rachillae themselves are branched and the flowers are borne on these branches.Flowers are usually borne in groups of three—one female flower together with two male flowers. In some species groups of four flowers have been reported. At the far end of the inflorescence, away from the axis of the tree, pairs of male flowers replace the triads of male and female flowers. Flower colour is poorly known. It must be recorded from live plants, since preserved flowers lose their colour over time, and records of these species in the wild are incomplete. Male flowers tend to fall into two groups—those with cream or yellow flowers and those with some amount of purple in the flowers. Female flowers are even less well known than male flowers.
Pollen grains are usually spherical to ellipsoid in shape, sometimes triangular, about 20 to 30 micrometres along their long axis and 20 to 30 μm in diameter. They are typically monosulcate, meridionosulcate or more rarely trichotomosulcate. The sulcus is a furrow which runs along the surface of the pollen grain and is usually the site at which pollination occurs. Monosulcate pollen has a single furrow that runs along the pole of the pollen grain. Meridionosulcate pollen have a furrow that runs along the equator of the pollen grain. Trichotomosulcate pollen, on the other hand, has three furrows. The outer layer of the pollen is covered to a greater or lesser extent with ridges, spines or warts. This "sculpting" tends to be more pronounced in species that are fly-pollinated and less pronounced in those that are pollinated by beetles or bees.
Fruit
The fruit of Aiphanes species is usually a red, spherical, single-seeded drupe. A thin skin, which can be either smooth or spiny, covers the fleshy mesocarp, which is typically orange and sweet. The mesocarp of A. horrida has one of the highest reported carotene contents of any plant product and is also rich in protein. The endocarp, which encases the seed, is brown or black and very hard at maturity. Seeds are light brown with a thin seed coat and white endosperm, which is sweet and tastes somewhat like coconut.Karyotype
Published chromosome counts exist for two species, Aiphanes minima and A. horrida; haploid chromosome counts vary from 15 to 18. Borchsenius and Bernal report that it is difficult to get accurate chromosome counts in palms and that differences in chromosome counts may reflect these difficulties.Taxonomy
Aiphanes is placed in the subfamily Arecoideae, the tribe Cocoseae and the subtribe Bactridinae, together with the genera Desmoncus, Bactris, Acrocomia and Astrocaryum.In his 1932 revision of the genus, German botanist Max Burret recognised 32 species. Seventeen of these were new species, mostly based on collections made by German botanist Wilhelm Kalbreyer in northern Colombia between 1877 and 1881. Working with a very narrow species concept, and not being familiar with the variation present in natural populations, Burret placed almost every specimen into a distinct species. The bombing of the Berlin Herbarium during the Second World War destroyed the only known collections for 13 of these 32 species, further complicating the situation.
The International Code of Botanical Nomenclature requires each species to be represented by a type collection. The destruction of Burret's type collections left many species only known from his original descriptions, which generally lacked illustrations. Other specimens were designated to replace these, either by Rodrigo Bernal and colleagues in 1989 or by Borchsenius and Bernal in their 1996 monograph of the genus. Bernal and colleagues attempted to retrace Kalbreyer's travels in northern Colombia and collect specimens from as close as possible to the location of the original collections.
Burret divided Aiphanes into two subgenera, Brachyanthera and Macroanthera. Eleven species were placed in Macroanthera, while the remainder were placed in Brachyanthera. In their 1996 monograph, Borchsenius and Bernal questioned the applicability of these subgenera. They recognised that if Macroanthera was reduced to three species it could form a viable grouping, but that this would leave Brachyanthera overly heterogeneous. Consequently, they abandoned Burret's use of subgenera.
In the three decades following Burret's delimitation of the genus a further 15 species were described, bringing the total species count to 47. Borchsenius and Bernal determined that many of these names were synonyms, although American botanist George Proctor disagreed with their decision to lump A. acanthophylla into A. minima. Borchsenius and Bernal also described one new species, Aiphanes spicata, bringing the total number of accepted species to 22. In two cases the destruction of the only known collections made it impossible to be absolutely certain that a name was a synonym. The current World Checklist of Selected Plant Families, maintained by Rafaël Govaerts at the Royal Botanic Gardens, Kew, recognises 26 species, including four species described since the publication of Borchsenius and Bernal's monograph.
Burret divided Aiphanes into two subgenera, Brachyanthera and Macroanthera. Eleven species were placed in Macroanthera, with the remainder in Brachyanthera. In their 1996 monograph, Borchsenius and Bernal questioned the applicability of these subgenera. They recognised that if Macroanthera was reduced to three species it could form a viable grouping, but that this would leave Brachyanthera overly heterogeneous. Consequently, they abandoned Burret's use of subgenera.