Geographic Patterns

Diversity
Geography of Threatened Species
Endemism

Global patterns of amphibian diversity are dramatically illustrated in Figure 2. This diversity map clearly shows certain areas of high global diversity, including tropical South America and tropical West Africa. In contrast to the usual pattern of high species diversity occurring in the tropics, the southeastern United States is a global center for amphibian diversity, being particularly rich in salamanders. The problem of uneven survey efforts around the world, however, complicates interpretation of this map. Regions such as Indonesia, New Guinea and the Congo Basin are especially likely to be underrepresented on this map due to lack of adequate surveys.

Figure 2. Global Diversity of Amphibian Species

Looking at amphibian diversity from a country perspective, Brazil, with at least 751 species, has the greatest number of amphibians of any country on Earth, followed closely by Colombia. Table 3 lists the 20 most diverse countries and reveals some interesting findings. For instance, Colombia traditionally has been considered to be the richest country for amphibians, but has recently been surpassed by Brazil. Overall, though, these results must be considered in relation to the level of survey effort. Both Colombia and Brazil have received extensive survey efforts in recent decades, and although both countries can be expected to add significantly to their totals, the level of increase is likely to be less than in some of the other highly diverse countries. In South America, Peru in particular is relatively poorly sampled and is almost certain to rise very substantially in its species total, and can be predicted to pass the level of Ecuador. The diversity in Ecuador is, however, remarkable for such a small country.

Table 3. Countries with Most Amphibian Species

Among the Old World countries, the level of survey effort is often much lower than in the Americas. Indonesia can be predicted to be the richest country outside the Americas, but it is doubtful if even half of its species are yet known. It may end up with a level of diversity comparable with Brazil and Colombia. The situation in India is set to change dramatically with over 100 species in the process of description. Very large increases in species totals can also be predicted for Papua New Guinea and the Democratic Republic of Congo, the latter country having received almost no amphibian survey work in the last 40 years.

Countries that are not far behind that are set to pass the 200 species mark include Malaysia, Cameroon, Tanzania, Panama, Costa Rica and Tanzania. The United States of America and Australia can be predicted to fall down the ranking over time, though the former will remain the most important country for salamanders, with the possible exception of Mexico.

To view a summary of the data for all countries entitled "Global Amphibian Assessment Summary Data for All Countries," click here.

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Geography of Threatened Species

A map showing the global distribution of threatened amphibians (Figure 3) reveals patterns very different from depictions of overall species diversity. The greatest concentration of such species—including well over half of the currently known threatened amphibians—is in a relatively limited area running from southern Mexico south to Ecuador and Venezuela, and in the Greater Antilles (details in Figure 4). This region is dominated by species with small ranges, often living in montane areas. Many of these species have been subjected to severe habitat loss, and exposure to the fungal disease chytridiomycosis.

Figure 3. Global Distribution of Threatened Amphibians

Click map for larger image.

Other important concentrations of threatened species are in the Atlantic Forests of southern Brazil (Figure 5), the Upper Guinea forests of western Africa, the forest of western Cameroon and eastern Nigeria (Figure 6), the Albertine Rift of central Africa, the Eastern Arc Mountains of Tanzania (Figure 7), Madagascar (details shown in Figure 7), the Western Ghats of India, Sri Lanka (Figure 8), central and southern China, Borneo (Figure 9), the Philippines (Figure 9) and eastern Australia.

Figure 4. Distribution of Threatened Amphibians in Central America, Northern South America, and the Caribbean. [Click for Figure 4]

Figure 5.Distribution of Threatened Amphibians in the Atlantic Forest of Brazil. [Click for Figure 5]

Figure 6. Distribution of Threatened Amphibians in Cameroon and West Africa. [Click for Figure 6]

Figure 7. Distribution of Threatened Amphibians in Madagascar and Eastern Africa. [Click for Figure 7]

Figure 8. Distribution of Threatened Amphibians in Southern India and Sri Lanka. [Click for Figure 8]

Figure 9. Distribution of Threatened Amphibians in Borneo and the Philippines. [Click for Figure 9 ]

Table 4 lists the 20 countries with the highest number of threatened amphibians. These countries are in many cases different from those listed in Table 3, suggesting that either amphibians in some countries are more susceptible to threats, that threats vary between countries, or that there are other factors influencing the distribution of threatened species.

Table 4. Countries with Highest Number of Threatened Amphibians

The countries listed in Table 3 have a particularly great responsibility for protecting the world’s threatened amphibians. Colombia, the second-most diverse country, has the highest number of threatened species. The major threats to amphibians in Colombia are habitat loss although there have been many as yet unexplained declines also occurring, and the dramatic topography of the Andes means that many of the amphibians have very restricted ranges making them more vulnerable to threatening processes. Brazil, the most diverse country, is ranked only fourth for number of species threatened, most of which are in the Atlantic Forest region, and has a significantly lower percentage of its amphibians threatened than the global average* (see note below.).

Considering the percentage of a country’s amphibian fauna that is threatened provides a stark contrast to the previous table, which focuses on the number of threatened species. Table 5 lists the countries with the highest percentage of threatened amphibians.

Table 5. Countries with Highest Percentage of Threatened Amphibians

Note: only countries with 10 or more species are included.

The top five countries are all in the Caribbean, and at least 70% of all the amphibians in these countries are threatened. Compared to other regions, the Caribbean stands out as the region with by far the highest percentage of threatened species. This is mostly a result of extensive habitat loss as well as some incidents of disease, in particular in Puerto Rico.

In Mexico, ranked fifth for diversity, but second for the number of threatened species, more than 50% of amphibians are threatened. Severe habitat loss as well as disease outbreak in some regions are the main threats. Most of the other countries in Table 5 are in Central or South America. The main causes of threat here also being disease and habitat loss.

To view a summary of the data for all countries click here.

* It should be noted that for certain species endemic to Brazil, it has not yet been possible to reach agreement on the Red List Categories between the GAA Coordinating Team, and the experts on the species in Brazil. The Red List Categories displayed for individual species are those that were agreed at the GAA Brazil workshop in April 2003. However, in the subsequent consistency check conducted by the GAA Coordinating Team, many of these were found to be inconsistent with the approach adopted elsewhere in the world. Under the notes on Red Listing for each species, the likely consistent Red List Category is given for these species, and it is these consistent Red List Categories that are used in the analyses presented here.

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The number and percentage of endemic amphibians by country shows some important patterns. Table 6 lists the 20 countries with the largest numbers of endemic species (i.e., occurring in no other countries), while Table 7 lists the twenty countries with the highest percentage of endemism.

Table 6. Countries with the Most Endemics

Table 7. Countries with the Highest Percentage of Endemics

To a considerable extent, the countries with the largest number of endemic species ( Table 6) match those with the largest total diversity of species ( Table 3), which is not surprising. However, it is noteworthy that several island countries that do not appear in Table 3 do appear in Table 6: Sri Lanka; the Philippines; and Cuba. Brazil and Colombia have many more endemics than any other countries, with Mexico, Madagascar and Australia each having 200 or more endemics.

The percentage of endemism ( Table 7) shows a very different pattern, with six island countries each having 100% endemism (none of these with very diverse amphibian faunas). Of the countries with high amphibian diversity ( Table 3), Madagascar and Australia (both essentially very large islands) stand out with by far the highest levels of endemism.

To view a summary of the data for all countries click here.

In Figure 10, a preliminary look at Endemic Amphibian Areas is provided. This map is based on the same approach adopted by BirdLife International in defining Endemic Bird Areas (EBAs). We define an Endemic Amphibian Area as any place where at least two species with ranges of less than 50,000 km2 overlap. About 70% of amphibians have ranges of less than 50,000 km² compared with just 25% of bird species.

Figure 10. Endemic Amphibian Areas

Figure 10 looks remarkably similar to the global map of Endemic Bird Areas (and also to other priority-setting mechanisms such as Conservation International’s Hotspots). Clearly, amphibians with small ranges are concentrated in generally the same areas as birds. Preliminary results for mammals reveal a very similar pattern as well, suggesting some fundamental biogeographic patterns that tend to span diverse taxonomic groups, with different life history patterns, and different alpha-beta diversity tendencies. These fundamental patterns are clearly key to guiding the development of conservation strategies in the future. A few differences are apparent, though, the most notable being the Appalachian Mountains in the eastern United States of America, which are the world’s center of salamander diversity and endemism, and are also extremely rich in other aquatic life forms, such as freshwater fishes, turtles, mussels, and crayfishes.

Our analysis of Endemic Amphibian areas includes Data Deficient species, which perhaps should have been omitted, since these include a number of species currently known only from their type localities, but which may be more widespread. We suspect that if these Data Deficient species are removed, some of the Endemic Amphibian Areas in places such as the Amazon and Congo basins would disappear, resulting in a map even more similar to that of Endemic Bird Areas.

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