Chapter 10. Chapter 10: Biodiversity

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.

Question Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term	Definition
yFYZ98IwCmwUrecfdQyNG6K0kMEoPcIvfC3E+E7RQkHEoEoLs1rl3Xvf2YX17y+g	Describes a species that is locally extinct in one or more areas but still has some individual members in other areas.
6uncIrzbmkmNZZXriPOt10cRTdNdgHSahlogiruPISRQn7o3b565yYX+6FWPpvMW	Describes a species that is native to a particular area and is not naturally found elsewhere.
GOb2iRYYJnqgHKiuKRxHgb7EY8fFVuCqPsa7sFztEscwSc30+5lhVlt36xKNlwky	An area that contains a large number of endemic but threatened species.

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Question 10.1

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Question 10.2

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Question 10.3

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Question 10.4

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Question 10.5

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Question 10.6

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Question 10.7

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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.

Question 10.8

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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

Question 10.9

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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.

Question 10.10

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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.

Question 10.11

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.

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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.

Question 10.12

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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.

Question 10.13

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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

Question 10.14

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Question 10.15

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Question 10.16

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:

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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.