Biodiversity hotspots are important places where there is more biological diversity than average, especially in the number of unique species and species combinations.
Except biodiversity is always uneven. There will always be places with more with components [genes, species, ecosystems] than others. And no two places will have the same biological attributes [diversity, abundance, composition]. In fact, components and attributes of biodiversity are always patchy.
This 'uneveness' a rule of nature that we don’t often see but it helps to ensure the efficiency and resilience of nature. We would be lost without it. And a consequence is that some places will be biologically 'hotter' than others.
This is not the usual explanation of hotspots. That has been taken by environmentalism and conservationists to mean places where there is especially rich biodiversity. Most importantly where there are many species that are endemic [species that evolve in that place] or are found nowhere else.
At the largest scale Australia is a biodiversity hotspot because it has such a high proportion of unusual species found nowhere else in the world. This is a consequence of its isolation and age.
Back when the continents were joined together as Gondwana each species could potentially spread far and wide. Then, some 180 million years ago the continents that we recognise began to form and drift across the earths crust. Australia drifted away on its own, separate from other land masses for a very long time.
Isolation allows for sympatric speciation [when populations of a species that share the same habitat become reproductively isolated from each other] and plenty of time for allopatric speciation [when a population is separated geographically, restricting the gene flow between the subpopulations]. Whole lineages of species, such as the marsupials, had time to evolve in isolation separate from mixing or competition.
In short, lots of time away with modest disturbance will create a hotspot.
There are three important pieces of information needed to detect a hotspot.
This gives us local species richness, a measure of endemism and an ability to compare to see if the region or area is richer in biodiversity that we would expect.
For a long time this information itself was patchy.
We still lack full species inventories for many important animal and microbial groups, notably the invertebrates, bacteria and fungi.
This means that the biodiversity hotspots we have identified tend to be for richness and endemism of plants [eg the cape fynbos] and/or the better-known animal groups [e.g. the marsupials of Australia]
Australian marsupial, Brushtail possum, NSW
Hotspots are really a large-scale expression of universal patchiness caused by the uneven distribution of organisms.
There are very few places where species are evenly spaced across the landscape. And even when we see uniformity that can be deceptive. Biodiversity is always patchy.
We measure this species difference across the landscape as beta diversity [turnover in composition from place to place]. Hotspots are an expression of this patchiness and we have latched onto them as worthy of special attention. Except that it is the patchiness itself that is important, not just specific, particularly unusual patches.
Biodiversity hotspots will continue as a focus of conservation effort as protection rewards the effort. It is worth remembering that they are an expression of patchiness that is everywhere and vital to how nature works.
the Okavango delta in northern Botswana typifies the patchiness of biodiversity with seasonally flooded plains and wooded islands — ironically the Okavango is not a hotspot of endemism as it is recent in evolutionary terms
If you would like to find out more, click on the authors below that link to some scientific papers on this topic...
Jepson, P., & Canney, S. (2001). Biodiversity hotspots: Hot for what? Global Ecology and Biogeography, 10(3), 225–227.
Reid, W. V. (1998). Biodiversity hotspots. Trends in Ecology and Evolution, 13(7), 275–280.
The links go to the websites of the publishers of this material. In some cases it is possible to find out more and even a PDF of the publication by entering the title of the paper into Google Scholar.
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marsupials are classic Australian animals including the grey kangaroo and the swamp wallaby [below]
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