Astrocaryum alatum is a species of palm with edible nuts, a flowering plant in the family Arecaceae. It is a common species found many types of rainforests and swamps in Honduras, Costa Rica, Nicaragua and Panama.
It is locally known as the coquillo or coquito in Costa Rica.
Description Astrocaryum alatum is the most common, least spiny and smallest of the three species of Astrocaryum in Costa Rica.
It is a solitary palm, it does not form a cluster of trunks. The trunk grows up to six metres in height, often just two to four metres. It is fast-growing, faster than other Astrocaryum species.
The ripe fruit are some 3.8–5 cm long and 3.2-3.8 cm in width. Typically, this species has fruit which are densely spiny on the end half, but smooth in the basal half where it connects to the rachis. The fruit are more-or-less obovoid, greenish brown to yellow-brown and have a small beak at their end. They are borne in compact, spicate clusters. The rachillae develop entirely from staminate tissue, and break easily or naturally when the fruit are fully ripe. The flesh is white, firm, and a few millimetres thick.
Similar species In Costa Rica there are three species of Astrocaryum, and the other two species, A. confertum and A. standleyanum, are uncommon and restricted in range, although both are sympatric with A. alatum. This is the smallest, most common and least spiny species. It is the only species to have large fruit with spines on their distal ends, which are not a bright orange colour. It is also the only species to have leaves with unevenly divided leaflets which are arranged on a single plane, as opposed to multiple planes in the other two species, which gives their leaves a plumose appearance. The inflorescence of A. confertum is held erect, even when it is eventually covered in ripe fruit.
A. mexicanum is the most similar species, so similar that in 1995 some experts noted the two taxa might be conspecific. Jean-Christophe Pintaud and colleagues provided a table of differences in anatomical leaf characteristics in 2008, which are rather subtle and require a microscope. The key provided notes the following differences: A. mexicanum has a thinner trunk without persistent leaf bases, but armed with rings or groups of flattened spines; smaller flowers with a proportionally smaller calyx and distinct, tooth-like staminodes (as opposed to staminodes merged into a ring); fruit with more but shorter spines; and the nut with the three pores positioned close to the apex (as opposed to up to a third of the distance from it).
Acrocomia species are other palms which are similar enough to be confused with this species, and the clustering Manicaria saccifera is superficially similar. Cryosophila species are also large palms and also have big trunk spines, but have fan-shaped leaves and forked spines. Several Bactris species have sharp trunk spines, but are often smaller trees. Astrocaryum species in general can be told apart from these and other palm genera by the whitish or silvery undersides of the leaves.
Common names The Spanish name coyolillo is a diminutive of coyól. The name is attested from Costa Rica in 1908, and said to also be used for different species of palm. The word coyól itself is derived from the Nahuatl language word coyolli, and originally means a type of round bell.
Taxonomy Astrocaryum alatum was first described in 1939 by Harold F. Loomis, an agronomist working at the U.S. Plant Introduction Garden, Coconut Grove, Florida (and also an important millipede expert). The 1939 article itself remarks that it is strange such a large, common and obvious plant in a well-known region had only attracted the attention of a taxonomist so late in history. This is because it was, in fact, known before. The pioneer ethnobiologist Henri François Pittier discussed the species using the name A. polystachyum. This name had apparently first appeared in a 1885 publication by William Hemsley in the series Biologia Centrali-Americana, but attributed to the German palm expert Hermann Wendland, and said to grow in Costa Rica, citing a type kept in Kew which was collected along the Sarapiquí River. There appears to be some confusion here: Wendland had never described a A. polystachyum, but instead had named a A. confertum from Costa Rica (absent in Hemsley's work). A. polystachyum is now considered a synonym of A. confertum, but Pittier is clearly referring to A. alatum in his work, based on his description and the range he gives.
As such an author of 1939 article had stayed at the town of El Cairo, Costa Rica, in 1937 and 1938, collecting specimens and seeds of the palm and calling it A. polystachyum. The seeds had been exported to the USDA in the US, and from there been distributed to interested plant growers in Florida with the Plant Introduction number 123380 under the name A. polystachyum. It was noticed however, that neither Hemsley nor Wendland had properly described the species, thus Loomis decided to rename the taxon A. alatum.
Typification Loomis did not designate a single holotype, it is difficult to fit all the representative organs of a large palm on a single herbarium sheet, but a type series of sheets of palm parts, stored at the United States National Herbarium, collected "along the Río Hondo near the fields of Santa Clara" by Orator F. Cook and C. B. Doyle in 1903. see also 1, 2, 3, 4, 5 and 6.
Classification A. mexicanum is very similar. Palm expert Andrew James Henderson and colleagues noted in their 1995 Field Guide to the Palms of the Americas that it was so similar, it might even be conspecific. Max Burret had classified A. mexicanum in a segregate genus Hexopetion in 1934, and when Loomis described A. alatum in 1939 he neglected comparing the two taxa, but none of the important publications on Neotropical palm taxonomy which were published in the rest of the 20th century followed Burret. Jean-Christophe Pintaud and colleagues placed A. alatum in Hexopetion in their 2008 paper, re-describing Hexopetion in the process to allow for the inclusion, although few seem to have followed their taxonomic interpretation.
In 2011 a group containing some of the previous authors published a study which looked at the differences between related palms in a number of plastid DNA and nuclear markers in order to elucidate their phylogeny. This study found strong evidence that A. alatum and A. mexicanum form a monophyletic group sister to the remaining Astrocaryum species.
Distribution Astrocaryum alatum is a widespread and common species found in eastern Honduras (Gracias a Dios Department), Costa Rica, eastern Nicaragua and western Panama. It occurs on both coasts of Costa Rica, although the IUCN claims it mostly occurs on the Caribbean side (although the distribution map as well as the list of national parks provided by the same website contradicts this).
In Panama it occurs in the provinces of Bocas del Toro, Coclé, Colón, San Blas and Veraguas, as well as the formerly US controlled Panama Canal Zone. Henderson et al. state that the Panama Canal appears to mark its eastern limit, but San Blas lies to the east of the Canal. It is common near the Canal around the town of Santa Rita and in Bocas del Toro.
In Nicaragua it occurs in the departments of Río San Juan and Zelaya.
As of 2022 the Plants of the World Online website claims it occurs in Colombia, but this is referenced to a source (Catálogo de plantas y líquenes de Colombia) which does not mention this species at all. Other older sources also state it occurs in Colombia.
Ecology Habitat Astrocaryum alatum occurs from sea level to an altitude of 1,000 metres, or 15 to 400 metres in Nicaragua, or 0 to at least 800 metres in Costa Rica. It is not a habitat specialist in general. Although it occurs in numerous habitats, it is particularly abundant in swamp forests. It can germinate and survive in soft, watery mud, as well as firm soil, but avoids constantly submerged ground. It is also common in disturbed, cleared forest land, mature secondary woodland and deforested pastures. This species also occurs in higher altitude upland rainforest, but in this habitat it occurs as an understory palm at relatively low densities, whereas it is often found in very high abundance in swamps. It does have some specific microclimate preferences in swamp forests, its distribution is primarily aggregated in two specific phytosociological associations, a specific type of inundated palm swamp and a mixed hardwood swamp dominated by Pterocarpus officinalis (this is locally called sangrillo). The habitats often intergrade to some extent. Although it is a very common species in both habitats, it not a dominant species in either.
There are a number of different types of palm swamp forests in Central America. A. alatum enjoys a particular low-biodiversity, high-density Manicaria saccifera-dominated swamp which is inundated up to a meter deep at times, although the ground is drained a number of times a year. The ground is covered in water most of the year, but usually the water table is very close to soil level. M. saccifera is a superficially very similar palm. The water is often brackish. This swamp-type is very densely planted with hundreds of trees a hectare, many of them hardwoods. Most of this habitat is found in the lowlands along the Caribbean coast, and it is very common within Barra del Colorado Wildlife Refuge and Tortuguero National Park in Costa Rica, extending deep into central eastern Nicaragua, but also is recorded to occur in Caño Negro Wildlife Refuge, and along the Pacific coast in the Osa Peninsula in the Sierpe region (Térraba-Sierpe National Wetlands). M. saccifera shares this habitat with the palms A. alatum and Euterpe spp., with the most common broad-leaf trees being Calophyllum brasiliense, Symphonia globulifera, Carapa guianensis and Dialium guianense. Astrocaryum mexicanum takes the place of A. alatum in otherwise extremely similar Manicaria swamp in Belize to the north of the range of A. alatum. Manatees often move into the deeper channels found in these swamps in order to feed on aquatic plants (Ludwigia and Hydrilla). There are no species endemic to such habitats, overall herpetofauna biodiversity is low and similar to surrounding lands, but larger mammals may frequently briefly forage in these areas when the ground dries.
Sangrillo swamp forests are one of the most common habitats in Costa Rica. The land is flat, near sea level and often floods. Soils are alluvial, black in colour and rich in organic material. Fresh water covers the land for up to nine months a year, it drains continuously but the ground is always wet. Trees usually have buttress roots. In this forest type, A. alatum is the third most common species by basal area, after Pterocarpus officinalis and then Carapa guianensis, but these statistics are exactly opposite when one looks at mature individuals per hectare, with A. alatum being present at an average density of 143 stems/ha. Less commonly found trees here are Pentaclethra macroloba and Virola multiflora. In these forests A. alatum is part of the canopy. The palms share the land with giant herbaceous plants such as Heliconia spp. and Maranta spp. There is ample ground-cover. It grows together with Virola sebifera in the lowland forest of Barbilla National Park in Costa Rica.
A 2002 World Bank report classified and mapped Central America into some 90 ecosystems/ecoregions. In this system A. alatum is a frequent species, but never a dominant, in four main types of lowland forests, including the two ecosystems discussed above. The other mentioned ecosystems are well-drained, and moderately drained, tropical evergreen broad-leaved lowland rainforest.