| Pleurothyrium | |
|---|---|
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Magnoliids |
| Order: | Laurales |
| Family: | Lauraceae |
| Genus: | Pleurothyrium Nees |
Pleurothyrium is a genus of plant in family Lauraceae. They are present in Laurel forest habitat and montane Cloud forest.
Contents |
Pleurothyrium is a genus of neotropical distribution occurring 40 species distributed from Guatemala to Bolivia, in Panama, Guatemala, Salvador, Honduras, Nicaragua, Costa Rica, Colombia, Venezuela, Ecuador, Peru, Bolivia... and extending to southern Brazil, of evergreen trees and bushes of the family of the Laurel in the great Lauraceae family. Its natural habitat are subtropical or tropical moist montanes where this genus have many Endemisms. In Brazil is represented by 13 species, and the State of Rio de Janeiro, only for P. amplifolium (Mez) Rohwer (Werff 1993).
They are monoecious trees reaching up to 30 m high; Hermaphrodites. The leaves are alternate, without papillae on the abaxial epidermis, elliptical, with acute base and apex, chartaceous, glabrous or minutely puberulous on the back. The genus have small flowers. The inflorescences are paniculate, thyrsus-paniculate, cymose last branching, densely and shortly pubescent, flowers 7 mm in diameter, creamy white, fragrant. Flowers monoclinic with hypanthium urceolate, not compressed below the tepals, tepals 6, usually erect or reflexed, equal, inner surface with or without papillae. Androecium with 9 stamens fertile, fillets generally thinner than the anthers, anthers quadrilocelares: 1st and 2nd series with three stamens each, anthers with a pair of loculi with dehiscence side and a pair introrse, 3rd series with three stamens, a pair of glands in basis of fillets, well developed, sometimes fused, in some species, the stamens of the 3 series fuse into a mass like a pillow. Anthers with a pair of locelos extrorse and a couple side-extrorse; 4th grade estaminodial present, reduced with 3 staminodes, or absent. The fruit is a berry ellipsoid, partially surrounded by a top margin simple, tepals deciduous or persistent. 2 cm long and 1.5 cm wide when dry, ca 5 mm dome deep, with large lenticels. The berry have 1 seed dispersed frequently by birds.
They have habitat preference by laurel forest, and altitudinal range from low evergreen tropical forest in Amazon region but also in tropical mountain cloud forest. Species in less humid environment are smaller or less robust, with less abundant and thinner foliage and have oleifera cells that give trees a more fragrant aroma. Some species live in symbiosis with ants. Pleurothyrium is present in tropical and montane rainforest, in the Andean mountain cloud forest, but grow also in evergreen lowlands tropical laurel forests. Pleurothyrium mostly consist of trees, occurring at low elevations, but some species are living top at 1900 m.[1]
The ecological requirements of the genus, are mostly those of fog moisture precipitating almost continuously in a natural habitat cloud-covered for much of the year. An ecosystem of great exuberance characterized by high humidity, no seasonal changes and with a wide variety of botanical and zoological species but also highly fragile against external aggressions. The genus require continuously moist soil, and do not tolerate drought. The most known trees are used by the timber industry. The fruit, a berry, is an important food source for birds. In some species the seed dispersal is carried out by monkeys, chipmunks, or fishes.
The Family Lauraceae was part of Gondwanaland flora and many genera also, migrated to South America via Antarctica in ocean landbridges by Paleocene time. There they spread over most of the continent. When the north American and south American tectonic plates joined in late Neogene, volcanic mountain building created island chains which later formed the meso-American landbridge. Pliocene elevation created new habitats for speciation. While some genera died out in increasingly xerophytic Africa, starting with the freezing of Antarctica about 20 million years ago and the formation of the Benguela current, others, like Beilschmiedia, and Nectandra, which also reached south and meso-America, are still surviving today in Africa in a number of species. The genus Pleurothyrium is related with Nectandra, where the species were beforly classified. The genus Persea, however, died out in Africa, except for Persea indica, surviving in the fog shrouded mountains of the Canary Islands, which with Madagascar constitutes Africa's Laurel forest plant refugia. In meso-America, the genus Nectandra proliferated into new species and the berries of some of them constitute a valuable food supply for the quetzal, that lives in the montane rainforests of meso-America. Since this habitat is constantly threatened by encroching agriculture, the laurel forest animal or vegetal species had already become rare in many of its former habitats and are threatened by habitat loss.
The quetzal favorite fruits are berries of relatives of the avocado family. Their differing maturing times in the Cloud forest determine the migratory movements of the quetzals to differing elevation levels in the forests. With a gape width of 21 mm, the quetzal swallows the small berries (aquacatillos) whole, which he catches while flying through the lower canopy of the tree, and then regurgitates the seed within 100 meters from the tree. Wheelright in 1983 observed that parent quetzals take far less time intervals to deliver fruits to the young brood than insects or lizards, reflecting the ease of procuring fruits, as opposed to capturing animal prey. Since the young are fed exclusively berries in the first 2 weeks after hatching, these berries must be of high nutritional value. Usually only the total percentage of water, sugar, nitrogen, crude fats and carbohydrates are reported by ornithologists[2]
It contains the following species (but this list may be incomplete):