randomisation

Benefits of invasive species management for terrestrial biodiversity are widely expected and promoted in New Zealand. Evidence for this is presented in policy and scientific reviews of the literature, but the robustness and repeatability of the underpinning evidence-base remains poorly understood. We evaluated the design of field-based studies assessing biodiversity responses to invasive species management in 155 peer-reviewed articles published in 46 journals from 2010–2019.

The primary aim of a scientific investigation is to find the most likely model for a situation out of a host of alternative explanations. The strength of evidence provided by anecdote, logical argument, mathematical modelling, observation, and designed studies (manipulative and observational) are discussed and the effectiveness of randomisation and orthogonal designs in separating hypotheses compared. Pseudoreplication is shown to be often misunderstood. It consists of two concepts: the importance of adequate replication and the independence of the sampling units.

Functional convergence of different communities in similar environments would be expected as an outcome of the operation of 'assembly rules'. At an ecological level, competitive exclusion would restrict the co-occurrence of species with similar niches. Repetition of competitive sorting on an evolutionary time scale might lead to character displacement.