Niche apportionment or random assortment: species abundance patterns revisited

Attempts to give coherence to a range of niche apportionment models. Niche apportionment can be categorized through the sequential breakage process of total niche, including the MacArthur Broken-Stick model which has traditionally been envisaged as a simultaneous breakage model. Five niche apportionment models (Geometric Series, Dominance Preemption, Random Fraction, MacArthur Fraction and Dominance Decay) are contrasted to a model where no conventional niche apportionment is assumed, ie Random Assortment model which may relate to a highly dynamic community under a variable environment. In addition, Composite model is proposed which combines niche apportionment and random assortment. Species-abundance data from a community of epiphytic chironomids were used. Random Fraction and Random Assortment both successfully fitted the data based on the number of individuals. Only Random Assortment successfully fitted the biomass data. The epiphytic chironomid community represents a highly dynamic system which is not structured through the process of niche apportionment envisaged here. -from Author