WOULD WE RECOGNIZE A BROKEN-STICK COMMUNITY IF WE FOUND ONE

The Broken Stick distribution is a standard null model of community structure. It predicts the distribution of species' relative abundances (i.e. dominance/diversity relations) when resources are partitioned into niches at random. However, Pielou pointed out that since all possible abundance distributions are equiprobable under the model, it is difficult to recognise any particular community as a Broken Stick one. To determine whether this makes it impossible to recognise a Broken-Stick community in practical dominance/diversity studies, one thousand 'communities' were generated by computer as realisations of the Broken Stick model, and four common continuous-data dominance/diversity models fitted to each, to determine the best fit. With few species in a community, the community was unlikely to be recognised as having been produced by the Broken Stick mechanism. The probability of correctly identifying the community as a Broken Stick one rose with the number of species in the community, until with 40 or more species in the community correct identification was made in 75% of cases.