Methods in molecular biogeography: The case of New Caledonia

Abstract

AbstractAimTo examine the different methods currently used in molecular biogeography. Methods of interpreting evolution in space (ancestral‐area algorithms) always find a centre of origin for a group in the region of a paraphyletic basal grade, although regionally restricted basal grades can also be generated by simple vicariance. Current analyses of the timeline of evolution are usually based on the conversion of fossil‐calibrated ages (minimum clade ages) into maximum clade ages by imposing arbitrary, subjective priors. Thus, methods of analysing both space and time in evolution are flawed in theory. They are also inefficient in practice, as indicated by recent papers on the history of the New Caledonian biota, examined here as a case‐study. Work using current methods has left the phenomena as unexplained ‘conundrums’ and ‘enigmas’.LocationNew Caledonia and surrounding areas.TaxonVarious plants and animals.MethodsThe method favoured here is a synthesis of biogeography and geology. Tectonic features that coincide spatially with phylogenetic breaks (nodes) are identified. Fossils are used to provide estimates of minimum clade age, while the age of the tectonic features provides estimate of actual clade age. If the sequence of nodes in the phylogeny and the chronological sequence of the tectonic events match, a coherent sequence of vicariance events is indicated.ResultsSeveral critical studies on New Caledonian biogeography have been published in the last 5 years. The results from these can be analysed using revised methodology and integrated to give an alternative model of regional history.Main ConclusionsThe synthesis of geology and biology suggests a new interpretation of the New Caledonian biota, one in which the key processes are tectonic history, vicariance and metapopulation dynamics, rather than chance dispersal (as a mode of speciation), adaptation and radiation. The new model recognises the autochthonous, Mesozoic roots of many New Caledonian lineages.