Ancestral area analysis of Nothofagus (Nothofagaceae) and its congruence with the fossil record

Abstract

The evolutionary centre of origin of Nothofagus (Nothofagaceae) remains an open question. Competing hypotheses suggest either a South American or Australasian source area for Nothofagus. Antarctica, once part of Gondwana and densely vegetated in the Cretaceous, was certainly important for the diversification of the genus but cannot be included in current modelling due to its lack of extant species. By using Bremer’s (1992), Ronquist’s (1994) and Hausdorf’s (1998) methods, all based on cladistic philosophy, analyses of the modern areas of endemism being part of the ancestral area of Nothofagus were undertaken. Southern South America was distinctly identified as the likely ancestral area by Bremer’s and Hausdorf’s methods. This result is supported by the current fossil record. Ronquist’s method was not decisive and yielded ambiguous results, suggesting a larger, combined ancestral area. These results do not favour Australasia, or parts thereof, being an important area for Nothofagus origin. Bremer’s and Hausdorf’s methods identified New Zealand as the second most plausible source area, a result partly supported by the fossil record.