Basically, a certain habitat for dwelling of organisms can be regarded as biodiversity hotspot when there is large amount various organisms in one place. In other words, the habitat would be steaming with orgainisms that are of different species. There are instances where a particular habitat is predominately dominated by one onrganism, but biodiversity hotspot is not like that.
Another noticeable characteristics of biodiversity hotspot is the rate of competition among the diverse organisms. The habitat would be governed by the law of survival of the fittest, as each organism would have to fight for every available resources for them to survive. It's obvious that the weaker organisms would be preyed upon by the much stronger ones, which are the predators.
For instance, lion will eat up the antelope, just as the snake will eat up rabbit. This will also make the tolerance among the organisms to be very low, as they would find it difficult to coexist together in competitive habitat.