Geoscience Reference
In-Depth Information
Asian-Pacific rainforests look similar and fill similar niches. The Neotropical
agouti and Asian deer mouse are also similar in appearance. Toucans and hornbills
show remarkable similarities. Yet none of these animals are related. Figure 1.3 pro-
vides some additional examples of this phenomenon.
Adaptations for a Tropical Life
Plants and animals in the Tropical Forest Biomes, with millions of years of isola-
tion and long periods of climatic stability, have evolved interesting strategies to
respond to the environment. Adaptation is the way in which a plant or animal fits
into its surroundings. The better adapted an organism is, the more likely it will sur-
vive. Adaptations are influenced by myriad stresses and demands encountered by
the organism. Temperature, light, shade, water, food, shelter, as well as predation,
competition, and reproduction are all opportunities for adaptations. Evolutionary
adaptations have allowed tropical plants to flourish amid these many stresses.
Organisms within the tropical forests have evolved to maximize their probability of
survival and reproduction. As the world within the tropics has changed, so have
the organisms that inhabit it. When an organism is no longer able to adapt to its
changing environment, its chances of long-term survival are limited.
Stresses on tropical forest vegetation include high sun intensity; high rainfall;
unseasonable and episodic droughts; high frequency of tropical storms, hurricanes,
or typhoons; lightning strikes; severe wind events; and susceptibility to fire. Nutri-
ent poor soils and supersaturated soils lead to the leaching of minerals and organic
matter, as well as soil erosion. Tropical rainforests typically have no opportunity
for seasonal recovery from these saturated conditions. Tropical Seasonal Forests
can suffer from extreme events and can be stressed by either an abundance or total
lack of moisture.
Adaptations evident in plants include variations in physical characteristics such
as tree architecture, root structures, bark texture and thickness, variable leaf shape
and size, seed shape and size, as well as pollination and germination strategies.
Physiological strategies such as differences in photosynthetic rates, uptake of
nutrients and wood density, as well as chemical strategies that discourage preda-
tion are all types of adaptation found in tropical plants. Many of these adaptations
are described later in this volume.
The faunal composition of the Tropical Forest Biomes is similar within their
tropical regions. Larger mammals and birds often migrate between the two biomes.
Animals have developed unique evolutionary traits within each regional expres-
sion of the biome—strategies to travel through the forest, to take advantage of the
many and varied food resources available, to attract mates, and to discourage pre-
dation. These adaptations are evident in vertebrates and invertebrates alike. In
Australasia, there has been a full diversification of marsupial mammals in the
region. These include adaptations to life in the trees or on the forest floor. Specific
