Ordinal response regression models in ecology

Although ordinal data are not rare in ecology, ecological studies have, unt il now, seriously neglected the use of specific ordinal regression models. Here. we present three models - the Proportional Odds the Continuation Rati o and the Stereotype models - that can be successfully applied to ordinal d ata. Their differences and respective fields of application are discussed. Finally, as an example of application, PO models are used to predict spatia l abundance of plant species in a Geographical Information System. It shows that ordinal models give as good a result as binary logistic models for pr edicting presence-absence, but an additionally able to predict abundance sa tisfactorily.