Indicator value analysis as a group prediction technique in community classification

Using woody communities in a South African game reserve as an example, we have developed a group prediction technique based on total indicator value to aid in the interpretation of a TWINSPAN analysis. Our total indicator value method TIVM is based on Dufrêne and Legendre's indictor value method (IVM). IVM is widely used to identify indicator species and to calculate corresponding indicator values (IV). In TIVM sites are each given a total indicator value which is the sum of indicator values multiplied by abundance for all indicator species in that site. This value is in effect a summary of the indicator values for the total site. We show how this new method, total indicator value analysis, can be used in testing the precision of groupings suggested by a TWINSPAN classification, and secondly, in providing a quick way to identify the group (vegetation type) to which an unknown sample site, not used in the original classification, would belong.