Cecropia
Cecropia is a Neotropical genus consisting of 61 recognized species with a highly distinctive lineage of dioecious trees.
The genus consists of pioneer trees in the more or less humid parts of the Neotropics, with the majority of the species being myrmecophytic. Berg and Rosselli state that the genus is characterized by some unusual traits: spathes fully enclosing the flower-bearing parts of the inflorescences until anthesis, patches of dense indumenta producing Müllerian bodies at the base of the petiole, and anthers becoming detached at anthesis. Cecropia is most studied for its ecological role and association with ants. Its classification is controversial; in the past, it has been placed in the Cecropiaceae, Moraceae, or Urticaceae. The modern Angiosperm Phylogeny Group system places the "cecropiacean" group in the Urticaceae.
The genus is native to the American tropics, where it is one of the most recognizable components of the rainforest. The genus is named after Cecrops I, the mythical first king of Athens. Common local names in Venezuela include yarumo or yagrumo, or more specifically yagrumo hembra to distinguish them from the similar-looking but unrelated Didymopanax. In English, these trees are occasionally called pumpwoods or simply Cecropias. Spanish-speaking countries in Central America, Mexico, the Caribbean, Colombia, Ecuador commonly use the vernacular name, guarumo.
Taxonomic history
Cecropia was first recognized and accounted for by Marcgrave and Piso, the latter including an illustration with characteristic features. Loefling coined the generic name Cecropia. In 1759, Linnaeus described Cecropia peltata which he applied to many species. Willdenow created C. palmate, which was also applied to a various species. Over the next decade, additional species were added by Bertoloni, Martius, and Liebmann. Mixing of specimens was very common and a problem arose, which continues today, with many collections of Cecropia. Many species were also described by Hemsley, Richter, Donnell Smith, Rusby, Huber, Robinson, Pittier, Bailey, and the most extensive number by Snethlage. Additional species were recognized by Burret, Mildbread, Standly, Macbride, Diels, Standley & Steyermark, and Stadley & Williems.Hans Melchior placed Cecropia in the Urticales and Moraceae because of its woody bark. Later based on the floral characters, most notably the basal ovule and gynoecium, which appears to be formed from a single carpel, Thorne moved it to the Malvanae- Urticales, family Urticaceae. Berg, however, placed it in its own family Cecropiaceae. When phylogenetic data became available, Cecropia was then moved back into the Urticaceae.
Description
The genus is easily identified by its large, circular, palmately lobed leaves, about 30–40 cm in diameter and deeply divided into 7–11 lobes. The trees consist of very few branches, usually with candelabrum-like branching system. In Costa Rica, three-toed sloths are often spotted easily in Cecropia trees because of their open, leafless branches compared to other trees. Berg and Roselli state, “Branch development is often initiated in seedlings, even in the axils of the first formed leaves; prophylls are formed, and often the development of the first leaf begins but is arrested. In the axils of the leaves formed during later development, the axillary branch primordia do not produce more than one or two prophylls and a bud.” The branches of C. garciae and C. hispidissima occur at a height of 0.6 to 1 m and the branches depart at acute angles. In most species of Cecropia, the branches depart at obtuse angles and the crown has a distinct umbrella shape.High variation is seen in the morphology of Cecropia species, but most form small to medium-sized trees, 5–15 m tall. Although some species grow much taller, as large as 40 m, and some rarely surpass 5 m. The high degree of variation can be attributed to regional habitat differences and longevity.
The family Cecropiaceae is characterized by having adventitious roots, and in Cecropia, they become stilt-roots, which are a common feature of large trees, especially living near rivers or marshes. Cecropia spp. are usually full of vines, but not normally overgrown by them. Most species have internodes that are hollow and contain whitish pith. These internodes provide a nesting area for the Azteca ants that inhabit the trees.
When the branches are cut, they release a watery, often mucilaginous sap, which turns black when it is exposed to the air. To prevent inhabitation by ants and occupation and damage by herbivorous insect larvae, the terminal buds and upper internodes are filled with mucilage. Several species' leafy twigs are covered by a waxy layer, making them bluish.
Berg and Rosselli describe in detail six types of trichomes that can be recognized on Cecropia and more information on each can be found in their paper. They are: thick unicellular hairs, thin unicellular hairs, pluricellular trichomes, cystolith hairs, pearl glands, and Müllerian bodies.
Parts of the Cecropia such as the stipules, the spathes, and the main veins of the lamina have red-coloring substances. The concentration of the substances varies, even within species, and some parts can be green, bluish, pale pink, dark red, dark purple, and even blackish. The color may fade with age, and can be deposited equally or in patterns such as longitudinal stripes.
The leaves of adult Cecropia species are large and peltate, almost circular in circumference. The lamina is attached to the petiole, the venation is radiate, and the lamina is radially incised between the radiating main veins. Variation is high in the number of lobes or leaf segments, ranging from five to more than 20.
Similar species
Pourouma bicolor is very similar in appearance to the Cecropia, with its umbrella-shaped leaves, stilt roots, large leaves with wide lobes, and whitish color on the underside. The distinctions between the two, however, are: the petiole attaches at the base of the leaf rather than at the center of the leaf like Cecropia and Pourouma has leaf lobes that are triangular and pointed at the tip, whereas most Cecropia are rounded.Habitat and distribution
Between 40 and 50% of the 61 species of Cecropia are montane or submontane Andean, with the majority of species in the northern part of the Andes, in Colombia and Ecuador. The Andean region is regarded as the center of species richness and speciation because of the additional 25% of lowland taxa that reach the eastern or western foothills of the Andes. Therefore, only about 25% of the species occur outside of the Andean region. A map of the distribution of Cecropia can be found in the article written by Berg and Rosselli, 2005. Most species of Cecropia are lowland humid/rainforest species occurring from sea level to 1,300 m in altitude, while submontane species occupy an altitudinal range from 1,300-2,000 m, and montane species are found in cloud forest from 2,000-2,600 m. Many species have a narrow altitudinal and ecological niche, with certain species specializing in specific habitats, such as seasonally inundated habitats, rocky slopes, swamps, natural or man-made clearings, etc.Species in the genus Cecropia are some of the most abundant pioneer tree species in natural tree-fall gaps inside primary forests. Its geographic distribution extends along the Pacific and Atlantic Mexican coasts and in Central and South American forests, and are found over an elevation range of 0 to 2,600 m. Cecropia species are among the most abundant pioneers of other neotropical forests. It is native to the Neotropics and occurs as an introduced exotic plant elsewhere. In most low-elevation, wet regions of the Neotropics, Cecropia trees are ubiquitous and important invaders of man-made clearings.
The species C. pachystachya and C. peltata are invasive species in Old World localities including Singapore, Cameroon, Java, Malaysia, Ivory Coast, French Polynesia, and Hawaii. C. peltata has been nominated as one of the “100 of the World’s Worst Invasive Alien Species” by the Global Invasive Species Database. C. peltata was introduced to the Singapore Botanic Gardens in 1902 and has spread widely throughout Singapore along with C. pachystachya, which was introduced in the 1960s. The species is successful as an invasive species because of its ability to pollinate without the need for pollinators, the possible preferential liking for its fruits by frugivorous birds, and its lack of natural predators.