BIOL 1911 Chapter 54.5: 54.5 – Pathogens alter community structure locally and globally
29 Apr 2018
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54.5 – Pathogens alter community structure locally and
globally
• Pathogens – disease causing microorganism, viruses, viroids or prions
o Have universal effects in structuring ecological communities
• Pathogens provide clear effects when they are introduced into new habitats
o Can be particularly virulent in a new habitat because new host population have not had a
chance to become resistant to the pathogen through natural selection
o Ex: chestnut blight fungus had far stronger effect on the American chestnut than it had on
An n p n n’ n
Pathogens and Community Structure
• Ecological importance of disease can be highlighted by how pathogens have affected coral reef
communities
o White-band diseases (unknown pathogen) kills corals by causing their tissue to slough off in a
band from the base to the tip of the branches
o Staghorn coral has virtually disappeared from the Caribbean since the 1980s as. Result
o Corals provide key habitat for lobsters, snappers and other fish species
o When corals die, they are quickly overgrown by algae
o Herbivores come to dominate the fish community -> corals topple -> reef disappears ->
diversity plummets
• Pathogens and community structure in terrestrial ecosystems
o Sudden oak death (caused by a protist) killed more than a million oaks from California to
Oregon
o Loss of the oaks ahs led to the decreased abundance of at least five bird species that rely on
oaks for food and habitat
o Scientists have recently sequenced the genome of the pathogen in hopes of finding a way to
fight it
• Human activities are transporting pathogens around the world at unprecedented rates
o Protist that causes SOD likely came to North America from Europe through horticulture trade
o H1N1 spread around the world when infected individuals flew on airplanes to other countries
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