Biology Reference
In-Depth Information
corresponds closely to the period of rapid growth of human populations,
international trade, and urbanization in tropical regions. In fact, the great-
est diversification of the virus has occurred within the last century and
appears to be continuing at present.
The modern world is ideally suited as an evolutionary stage for viral
diseases that are able to move from animal reservoirs to humans. These
include the ebola virus of Africa and the SARS (sudden acute respiratory
syndrome) corona virus that appeared in China in 2003.
The Responses of Hosts and Vectors
Both plant and animal disease agents are capable of rapid evolution,
especially when introduced to new hosts and environments.The spread of
such agents to new geographical areas is a major concern for human
health, as well as the health of agricultural plants and animals and keystone
members of natural ecosystems. As we have indicated several times, how-
ever, the relation of disease agents to their hosts is coevolutionary; the host
as well as the disease agent is capable of evolution. In the next chapter, we
shall examine in more detail the evolutionary responses of plants to alien
diseases, as well as to introduced herbivores.
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