The Common Warthog and Its Parasites in the Free State Province (South Africa) Cannot be used to Test the ‘Enemy Release’ Hypothesis for an Introduced Species: The Value of Reference Point Information for Testing Hypotheses of Change

Abstract

Given the conservation concerns raised by invasive species, testing hypotheses dealing with invasion biology are crucial to understanding the mechanisms and drivers of invasiveness. Central to this though is a clear zoogeographical foundation regarding areas where a species is indigenous, and upon which an experimental design can be based. Recently Matthee et al. (2013) sampled ectoparasites of the common warthog, Phacochoerus africanus, in the Free State Province (South Africa), with the express intention of testing the hypothesis that 'non-indigenous species leave their natural parasites behind in their natural range, and would thus have lower parasite species richness in introduced [sic] areas' (Matthee et al. 2013: 260). Their experimental design rests on the assumption that the common warthog is an introduced species in the Free State. They base this assumption on two publications (D'Huart & Grubb 2001; Skead 2007), neither of which focus on warthogs in the Free State, and both of which have been superseded by a more recent and relevant study (Boshoff & Kerley 2013), which just postdates Matthee et al. (2013). This more recent work, however, has implications for the validity of the Matthee et al. (2013) study and these are addressed below.