Book review: If the conceptual straitjacket fits, chances are, you’re already wearing it

Abstract

ISSN 1948-6596 news and update book review If the conceptual straitjacket fits, chances are, you’re already wearing it Molecular Panbiogeography of the Tropics. Michael J. Heads, 2012, University of California Press. 565 pp. $75.00, £52.00 (harback) ISBN: 9780520271968; http://www.cambridge.org This is part of a series of volumes aimed at, in the words of its editors, examining “the role of de- scriptive taxonomy, its fusion with cyber- infrastructure, its future within biodiversity stud- ies and its importance as an empirical science.” The author’s stated intention is to attempt to demonstrate “patterns of community immobilism leading to allopatric differentiation, as well as other patterns of mobilism, range expansion, and overlap of taxa.” It was with these themes in mind that I delved into Heads’ latest work. But first, in the spirit of full disclosure, I have encountered the author of this book, as well as several of his fellow panbiogeographers, from the New Zealand as well as the New York schools of the subdiscipline, which together comprise a vocal minority in biogeography. My interactions with the panbiogeographers have come via a number of academic exchanges, each of which has unofficially ended in an understood ‘agree to dis- agree’, intellectual truce. Receipt of this review request generated feelings of both hesitancy and curiosity. I was hesitant to spend time on this topic because each prior exchange with Heads and his associates has boiled down to the willingness on my part (and that of our colleagues in main- stream phylogeography), to approach bio- geographic data from a perspective that is open to both dispersal- and vicariance-based interpreta- tion. By contrast, panbiogeograpers strongly re- ject the significance of dispersal a priori, in any form. Based on past interactions and published exchanges with this group (e.g., Holland and Cowie 2006, Nelson 2006), a clear way forward in this dialogue has yet to materialize. My curiosity came from the chance to evaluate this recent of- fering, being due in part to my admitted lack of appreciation of the usefulness of panbiogeogra- phy, and the possibility that my views might change given the “new” panbiogeographic per- spective promised in the Preface. Perhaps a brief refresher on the nuts and bolts of the field is warranted, since panbio- geographic reasoning can be perplexing for a number of reasons, not the least of which is that its proponents have created their own terminol- ogy. The field was proposed by Leon Croizat in 1958, and furthered by M.J. Heads as well as R.C. Craw and J. Grehan. Panbiogeography was defined by Craw et al. (1999) as a method whereby known species distributions are first mapped and then extended by drawing connecting lines on maps. Lines are termed ‘tracks’ and are drawn such that they ‘connect’ collection localities or disjunct dis- tributions of a particular taxon. Multiple overlap- ping tracks for unrelated taxa form ‘generalized tracks’. The figures presented in the new book consist of dozens of black-and-white maps with lines and shapes superimposed to indicate distri- bution patterns. Croizat was correct and ahead of his time in realizing that speciation can occur after emer- gence of a barrier within the existing boundaries of a distribution, a phenomenon that ultimately became known as vicariance. But this somehow led him, and the panbiogeographic movement which followed, to vehemently deny, a priori, any role of dispersal in natural history. Croizat (1964) stated “I intend to destroy these notions (pertaining to ‘means of dispersal’) because they positively interfere with the advance of knowl- edge on far-reaching points of evolution over space, in time, by form” (p. vi). This vague notion of evolution in space and time by form is repeated frequently in panbiogeographic publications. Ac- cording to Cox and Moore (2005) “Even after the theory of plate tectonics had been well docu- mented and widely accepted, Croizat refused to accept it, and never integrated it into his method- ology” (p. 31). Heads also expresses a refusal to © 2012 the authors; journal compilation © 2012 The International Biogeography Society — frontiers of biogeography 4.4, 2012