Gareth Nelson

From Candolle to Croizat: comments on the history of biogeography.

Biogeography is a strange discipline. In general, there are no institutes of biogeography; there are no departments of it. There are no professional biogeographers no professors of it, no curators of it. It seems to have few traditions. It seems to have few authoritative spokesmen. It is my belief, however, that there is a coherent history of the discipline. There are some general ideas some principles and some general problems. Some of them were defined in the early part of the nineteenth century, particularly in an essay by A. P. de Candolle.1 Because of the recent revival of interest in biogeography, occasioned in part by the development of the theory of plate tectonics, a consideration of the early history of the discipline is timely. Candolles essay was not an obscure article that no one read. It was an early, but neither the first nor the last, review of the new and growing field of phytogeography. It was soon read, assimilated, and

Three-taxon statements : a more precise use of parsimony?

Abstract— Binary characters can be represented in data matrices by the three‐taxon statements they imply. Transforming characters into three‐taxon statements may increase the sensitivity of parsimony to differences in the fit of data to alternative cladograms. Extrapolation of the technique to multistate features allows semi‐additive characters to be coded accurately. In many cases, analysis of the transformed data produces fewer equally parsimonious solutions than does analysis of the raw data. In other cases, additional equally parsimonious solutions, or even different solutions, may be produced; in those cases, the results appear to accommodate information from a larger number of characters than do the results from raw data.

OUTGROUPS AND ONTOGENY

Abstract— Common themes in some recent expositions of character phylogeny are attempts to prove that outgroup comparison is a method of the greatest generality, and that the ontogenetic criterion reduces to outgroup comparison. Another common theme is that pattern cladistics is wrongheaded in suggesting that ontogenetic data have a unique value for studies of character phylogeny. Analysis of particular examples that have been offered as proof of the themes shows them to be flawed and without significance. Arguments against pattern cladistics and the relevance of ontogeny stem from a concern for ideological purity and not for objective appraisal of relevant evidence.

IS FARRIS OPTIMIZATION PERFECT?: THREE-TAXON STATEMENTS AND MULTIPLE BRANCHING

Abstract — The three‐taxon approach to phylogenetic analysis separates the universe of cladograms into a larger number of classes of solutions showing decreasing degrees of fit to data than does conventional Farris optimization. The three‐taxon approach applies to character analysis Nelson and Platnicks interpretation 2 of multiple branching in cladograms.

Subtree Analysis, Nothofagus and Pacific Biogeography

, and one fungal taxon, analysed using the programCOMPONENT version 2.0 (Page, 1993). Their cladog-ram is: (Mad (Afr, E SAm)) (S SAm (NZ (NC (NG,Aust)))), relating Madagascar (Mad) to Africa (Afr)and north-eastern South America (E SAm) on the onehand, and southern South America (S SAm) to NewZealand (NZ), New Caledonia (NC), New Guinea(NG) and Australia (Aust) on the other (Fig. 1A). Ofspecial interest is their conclusion that New Zealandand Australia are related more closely to each otherthan to South America, in contrast with cladogramsrelating South America and Australia (e.g. Brundin,1966 and others listed in Linder and Crisp, 1995).

REPLY TO HARVEY

Harvey (1992) views, and thereby distorts, three-item analysis as a “character weighting scheme”, and as a “data transformation scheme”. Accordingly, he finds the “three-taxon method of dubious value” and “an abuse of parsimony”. III justification he offers comment on findings of Nelson and Platnick (1991), and results of parsimony analysis of his own hypothetical data. He reports no results of three-item analysis of his data, nor indication that he did three-item analvsis of anv data, hypothetical or otherwise. For his nine data sets [his fig. 4(A)-(I) each with six binary characters] his trees and those from three-item analysis may be compared (where trees found are more than one, the tree shown is strict consensus):

The Purposes of Biological Classification

All biologists use classifications to one degree or another, and those of us who work on classifications use the results of all other biologists to one degree or another, so you might reasonably expect that biologists in general would share some common conception of how classifications should be constructed and how they can be used. Certainly one might expect that all taxonomists, at least, would share such a perspective. But this is not the case; in fact, the theory of taxonomy is at present a very controversial subject, with much of the controversy revolving around the question of how to go about constructing an ideal classification.

WHY, AFTER ALL, MUST IT?

For decades cladists have been accused of being narrow-minded and doctrinal, when in fact these qualities belonged for the most part to the accusers. Even now, when cladists have achieved credibility in the scientific world, accusations nevertheless continue. A case in point is a recent piece by Szalay and Bock (1991). Apparently the piece is not addressed to the readers of this journal (of which the authors’ only citation is Saether, 1986), but to a more general and naive audience. Thinking to comment on the piece, of a nature unusual if not unique in the history of scientific prose, I soon realized that it precluded a rational summary. Struck by the frequent use of the word “must”, I listed the sentences in which the word occurs, sensing that the resulting accumulation might suffice as a summary, and even render superfluous much of my intended comment. Five sentences describe cladistics: