Community reassembly: a test using limestone grassland in New Zealand

To examine community reassembly, we sampled grasslands on calcareous soil ( 4%-24% CaCO3) in New Zealand that were largely composed of species introduc ed from Britain. We tested whether the British species had reassembled on N ew Zealand limestone into the same communities as they form on limestone in Britain. The vegetation of six New Zealand sites was sampled, each with te n 2 x 2 m quadrats that followed the standard methodology of the British Na tional Vegetation Classification (NVC). Analysing species presence and cove r using program TableFit with the full database of British species, the New Zealand species assemblages gave poor to moderate fits (40%-72%) to the co mmunities of the NVC, and even then not to calcareous grassland, though one site did fit to a calcareous spring community. The poor fits can be partly attributed to the absence from New Zealand of many British calcareous-spec ialist species. On omitting from the NVC database all species not present i n New Zealand, the fits increased somewhat to 48%-77%. Using this modified database, two sires fitted British calcareous grassland communities. These two sites are on thinner soil (<10 cm depth), under lower rainfall. Where f its were obtained to calcareous communities, the environment of the communi ty in Britain matched very well that of the New Zealand site. It is conclud ed that environmental and perhaps biotic filtering has been strong enough i n some sites to assort alien species into the same species assemblages as t hey form in their native range, indicating the Deterministic model of commu nity structure. However, the absence of some species has prevented full rea ssembly.