The Flora of Costa Rica and the Entire Neotropics

This topic submitted by Catherine Dilley ( at 6:33 PM on 5/16/03.

A view of our boat at Gaulin Reef in the Bahamas

Tropical Field Courses -Western Program-Miami University

“Never does nature seem more bountiful than in the tropics” -John Krischer, A Neotropical Companion

The Flora of Costa Rica and the Entire Neotropics

The flora of the neotropics, specifically Costa Rica, provides a wealth of diversity unlike any other region of the world. The variety of ecosystems produced between the mountains and the seashore provide ideal homes for more plant species than the entire continent of Europe( These vast numbers of plants are highly specialized with intricately developed mutualistic relationships, complex reproductive cycles, and advanced methods for resource acquisition which enable them to survive in these extreme environments.
Within this wealth of diversity there is more than 9,000 species of “higher plants” and 70% of these plant species are trees( To get a sense of the number of plants that find their home in the neotropics think about these facts:
-There are about 800 species of ferns in Costa Rica, that is more than in all of North America, including Mexico(
-More than 1,000 varieties of orchids can be found in Costa Rica, that is more than any other place on Earth(
-At least 800 species of ferns have been identified in Costa Rica(
-Costa Rica has over 2,000 species of bromeliads, including the pineapple, that is the richest deposit of such flora on the isthmus(
-There are more than thirty species of heliconias, commonly known as the “birds of paradise”, which are members of the banana family(
-Five species of mangroves grow along the coasts of Costa Rica(
-In most mature forests of the tropics at least 80-200 woody species can be found in one hectare(
- There are twelve different ecosystems found in Costa Rica that provide the perfect conditions for a large number of plants to exist in this relatively small country(
These are a few of the known facts that display the unimaginable plant diversity living in the neotropics.
Most of these plants have well developed adaptations from which their successful existence in the tropics relies. Many of these adaptations have evolved around mutualistic relationships, which were created between the plant and fungi, insects, or animals. An adaptation that is easily observed is the markings on the petals of many flowers. Most notably are the lines and spots that can be observed on the flowers of many orchid species. These markings seem to be guides for insects species directing them to the precious nectar contained within the flower. While the insects are fulfilling themselves with nectar they are also picking up pollen grains, which will be delivered to their next source of nectar( Cauliflory is another phenomenon that often occurs in the tropics which aides the plant in the process of reproduction. This is when some or all of the flowers produced on the tree come directly off the trunk or the larger branches. Usually this adaptation helps to accommodate for the weight of very large fruit or allows animals easier access to the flowers and fruit(Merrill 94-96). This statement briefly expresses the specialization that some species have which creates a relationship with animals:
“The interactions between plants and animals are closely related through specialization of certain species. The older the habitat, the longer the evolutionary period for specialization and adaptations.”
A strange adaptation that occurs in some species of the coffee family (Rubiaceae), which are epiphytic is the presence of a swollen base which is filled with large passageways. These passageways have openings to the exterior creating perfect homes for small insects, usually ants. These insects then bring large amounts of detritus into these tunnels. Then in turn this organic matter becomes nourishment for these plants that are located high in the canopy that would otherwise have no access to the nutrients of decaying matter(Merrill 96-99). A relationship that is common amongst most tropical trees is with mycorrhiza. This compromise between the roots of trees and fungi has nearly depleted the need for root hairs. The mycorrhiza readily provides most of the nutrients and moisture while the tree produces most of the carbohydrates for the fungi. Many species are so dependent on this relationship that outside of it they will not survive(
Some common morphological features that are easily noticed in the tropics are:
-growth rings, if apparent, usually do not show the age of the tree(Richards 49)
-drip tips are common on leaves allowing for rapid runoff of rainwater(
-most flowers are very large, showy, and born on long stalks to attract animal pollinators(
these are just a few of the features that are abundant in the neotropics.
A common characteristic found among plants of the tropics is the ability to reproduce asexually. One of the most prominent of these methods is loosely called “vegetative reproduction”. The process is when a plant sends out horizontal roots just below the soil surface, which will then produce, vertical shoots from nodes. This is also considered a form of resource allocation where the plant becomes much larger, but is not limited to the location of the original seedling. With this sort of reproduction, or multiplication as some may call it, there may actually only be a small number of reproductive individuals in a plant population, but each has grown to the size of many hectares and may have multiple subdivisions. This form of asexual reproduction is thought to be popular in the tropics as a result of the ability to grow the entire year, the competitive species-rich area of vegetation, and the difficulty in seedling establishment that in turn will favor great longevity and size in the adults(Janzen 12-13).
The reproduction process of tropical plants closely follows the change of the seasons either with prime pollination taking place during the rainy or the dry season. Most trees flower during the dry season when less rain allows the insects to be active for longer periods of time, enhancing the chance for cross-pollination. There are some tree species that will time their flowering after downpours so that the numbers of pollinators are highly concentrated, increasing pollination efficiency. Dry season pollination is more advantages because it does allow for the germination at the onset of the rainy season ensuring initial growth. Many seeds that are produced during the rainy season will lay dormant until the ideal conditions return the following rainy season(Kricher 9).
Not unexpectedly the fruiting patterns follow seasonal influence with most fruiting following at the peak of the rainy season. Most pioneer species are shade intolerant causing them to need large amounts of light for seed germination. These plants germinate at the onset of the rainy season, when tree falls are most common and create gaps allowing adequate light for these species to establish. The typical time for new leaf growth is during the rainy season when there is less insect activity that might destroy the vulnerable leaves (Kricher 9,10).
Tropical plants have developed many methods for the acquisition of the necessary resources. Bromeliads are well known for their ability to hold large quantities of water and detritus in their whorled bases of tightly overlapping leaves( The strangler figs establish themselves in tree canopies as epiphytes where they have access to high amounts of sunlight. Then the fig sends down roots to the forest floor where it can start to develop a root system that will eventually fuse and become the trunk of the tree engulfing the original host tree(Merrill 94-95). Some plants such as the “pitcher plant” is capable of trapping insects and using them for nutrients when other forms of detritus are not readily available(Merrill 100-101).
Plants are very complicated organisms and even more so in the tropics. The biodiversity and extreme climates have developed unusual and effective methods of survival. The future looks very bleak for the well developed treasures of the neotropics, which are necessary to ensure the survival of the human species and for all life to continue successfully on this planet.

Works Cited, 2000

Janzen, Daniel H. Ecology of Plants in the Tropics. Edward Arnold Ltd. London,
U.K., 1975 p.12-13

Kricher, John. A Neotropical Companion. Princeton University Press. Princeton,
NJ. 1997 p.1-10

Merrill, Elmer D. Plant Life of the Pacific World. The Macmillan Company, NY.
1945 p.94-101, 2000-2003

Richards, P.W. The Tropical Rain Forest, Second Edition. Cambridge University
Press. New York, NY. 1996 p.49

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