What are biodiversity hotspots, and why are they important?
Interactive Study Guide
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Guiding Question 10.4
What are biodiversity hotspots, and why are they important?
Why You Should Care
Biodiversity hotspots are parts of the world that have a particularly high level of biodiversity and endemism (having species that only occur in one area or a particular habitat that is itself rare). These areas are of high concern for all the reasons that you have already learned make biodiversity important, and because many of them are in areas with high human population density. Probably the most famous and emblematic example of an extinction from a biodiversity hotspot is the dodo. The dodo was a flightless bird related to the pigeon, the size of a medium-sized dog and lived only on the island of Mauritius, in the Indian Ocean far off the coast of Madagascar. Within 80 years of Mauritius’s discovery by Europeans in the early 1600s, every last dodo had been eaten by sailors and the animals they brought with them. This was probably the first time that the possibility that a species could go extinct was contemplated by the western world, and the dodo has entered our language in set phrases like "dead as a dodo" or "gone the way of the dodo" meaning dead, gone, and never to return.
Test Your Vocabulary
Choose the correct term for each of the following definitions:
Term
Definition
Describes a species that is locally extinct in one or more areas but still has some individual members in other areas.
Describes a species that is native to a particular area and is not naturally found elsewhere.
An area that contains a large number of endemic but threatened species.
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1.
Biodiversity hotspots do NOT contain:
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2.
Which of the following terrestrial ecosystems would you expect to have the most endemic species?
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3.
Which of the following is FALSE about endemic species?
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4.
Examine the map above. Most biodiversity hotspots are:
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5.
The largest individual hotspots are in:
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Most of the smallest and most isolated hotspots are:
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7.
Thought Question: Why are many biodiversity hotspots on islands?
Islands are isolated from the mainland and species have difficulty reaching them in large numbers. This means that a few species can end up evolving into new species that fill unoccupied niches.
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Thought Question: There is often tension between developed and developing countries about protecting biodiversity, especially if those developing countries contain hotspots. Can you predict why this is? Do you know any examples?
In general, developing countries consider it their right to develop as they see fit. Furthermore, they see developed countries, which have in the past all had policies that were not protective of biodiversity, to be hypocritical. As mentioned in the text, many developing tropical countries have strict customs laws that prevent the export of plants, animals, and other material out of their countries. This is to prevent biodiversity resources in their country from being used to profit firms in other countries.
Infographic 10.6: Isolation Can Affect Populations
9.
Where would you expect genetic diversity within a population of any given species to be lowest?
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Correct. Since it is not likely for any species to reach an isolated island, it is also unlikely for many individuals of the same species to arrive there and therefore the founding populations of species on isolated islands are often small. This in turn means that genetic diversity will be low.
Incorrect. Since it is not likely for any species to reach an isolated island, it is also unlikely for many individuals of the same species to arrive there and therefore the founding populations of species on isolated islands are often small. This in turn means that genetic diversity will be low.
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Where would you expect to find the fewest endemic species?
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Correct. Endemism results from isolation leading to speciation, so a mainland area where individuals from different populations can mix freely would have fewer localized species.
Incorrect. Endemism results from isolation leading to speciation, so a mainland area where individuals from different populations can mix freely would have fewer localized species.
11.
A classic model of the effect both isolation and size on the diversity of islands is depicted graphically below. Essentially, the number of species that can colonize or establish on an island depends on the isolation of that island and the number of species already there. The rate of extinction of species on the islands depends on their size and how many species are there. For any given island, the total number of species it can support should be where the function representing its colonization rate intersects the curve representing its extinction rate. The two establishment curves on the left represent two levels of isolation and the two extinction curves represent rates for large and small islands.
Which of the population sizes indicated below would represent a less isolated, large island?
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Correct. Small isolated islands would have the highest extinction rates and the lowest colonization rates so they would have the lowest population size. The opposite is true of large, less isolated islands.
Incorrect. Small isolated islands would have the highest extinction rates and the lowest colonization rates so they would have the lowest population size. The opposite is true of large, less isolated islands.
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Thought Question: Which of the two extinction curves represents small islands? Explain your answer.
The upper extinction curve (the top blue one) represents small islands. The more species there are on an island, the fewer niches and resources are available. This effect would be more dramatic on a small island where there are fewer niches and resources.
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Thought Question: Which of the two establishment/colonization curves represents near or less-isolated islands?
The higher yellow curve represents near islands. It’s easier for species to reach near islands, so they would have a higher establishment rate when the species richness on the island is low (represented by the left side of the graph) compared to more isolated islands.
Infographic 10.7: Biodiversity in Samoa
14.
If a species of plant only grew on two mountaintops, but the entire population died out on one of the mountains, you would best describe that population as:
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Endemic species are put at risk of extinction and extirpation by all of the following EXCEPT:
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Internet Exercise: Use this biodiversity hotspot website maintained by the organization Conservation International to search for threatened and endangered species in other hotspots. Make sure to compare threatened and endangered species on islands and continents. Then answer the following questions:
A) Do you see any pattern in the kinds of species listed as threatened?
B) Do you see a difference in the number or kind of threatened species on mainlands versus islands? Can you explain this pattern?
A) There could be many possible answers. Here are a few examples: Flightless birds Birds in general Butterflies Certain kinds of plants, such as orchids
B) There are typically more threatened species on islands. Often, this is because species evolving in isolation lose defenses crucial to survival against the larger variety of predators on mainland continents.
