Cladistic biogeography of waratahs (Proteaceae, Embothrieae) and their allies across the pacific

Abstract

The Proteaceae are often said to be a 'relict Gondwanan group' because they are disjunctly distributed over several southern continental blocks. Such distributions are shown by 12 different taxa above species-level in the family, which is thus potentially useful in cladistic studies of Southern Hemisphere biogeography.

We have produced well-corroborated cladograms for the subtribe Embothriinae and its sister-taxon, Lomatia. These taxa have almost identical distributions within eastern Australia and western South America. Distributions of most species of Embothriinae are relatively narrow and we have used them to define areas of endemism for analysis.

We analysed the biogeographic relationships of these areas under Assumptions 1 and 2 of Nelson and Platnick and Assumption 0 of Zandee and Roos, using R.D.M. Page's program COMPONENT. When analysed separately, Embothriinae and Lomatia share no area-cladograms under any assumption. The similarity between the two suites of area-cladograms, obtained in turn under each assumption, was assessed in terms of the symmetric difference of triplets. Under Assumptions 0 and 2 at least, the similarity between area-cladograms of Lomatia and Ernbothriinae appeared higher than would be expected due to chance. We took this as a fair indication that the two groups share congruent area-patterns, which justified analysing them as a single group.

When analysed as a whole, the {Lomatia + Ernbothriinae} clade yielded a single most parsimonious cladogram under the 'items of error' parsimony criterion (Assumption 1) and the same cladogram plus several others under the 'Wagner' parsimony criterion (Assumption 0).

The single cladogram on which these analyses agree seems to be consistent with conventional geological theories, assuming a history of vicariance events caused by continental break-up and climatic change.