Just as the proof of the pudding is in the eating, so it is in science that the testing of hypotheses is at the core of the development of theory. As set out in this book’s Introduction (Chapter 1), most ecological theory has been developed outside Australasia; this biogeographical region thus provides an excellent case study for investigating whether the generally accepted hypotheses from ecological theory really are applicable in a different context. Furthermore, many excellent observational studies have been carried out in Australasia; the history of invasions in that region can be viewed as a series of experimental tests of ecological theory. Indeed, the Australian native flora and fauna was so different from that of the rest of the world, that Darwin (before he became an atheist) asked himself in his diaries whether there had been two Creators instead of one (see Chapter 1).

In Chapter 1, we explained the reasoning behind the selection of the hypotheses that are reviewed in the main chapters in this book. At the beginning of this project all the authors were asked to formulate hypotheses, to give their feedback on the hypotheses, the way they were formulated and whether the hypotheses could be assessed by them; as a result of this collective effort authors could agree on assessing this present set of hypotheses. The hypotheses are derived from general ecological theory (see Chapter 1) but the material at hand cannot be viewed simply as ‘data’ such that the hypotheses can be tested as a part of statistical inference. This type of inference is familiar and easy for most scientists to address, and that is where most authors of this book clearly felt more secure than when they had to arrive at judgements from observations or from historical reconstructions. The overall conclusions, based on a meta-analysis of the assessment/testing of the 11 hypotheses by the authors of the chapters on species that moved into or out of Australasia as presented in the following tables, are clear: after weighing up the evidence many of the authors of chapters in this book concluded that there was no support for the individual hypothesis, or that they had to reject the hypothesis.