The panbiogeograpy of hagfishes: a reply to Briggs’s anachronistic criticism

Authors


Abstract

Briggs’s (2009) criticisms of Cavalcanti & Gallo’s (2008) panbiogeographical study of hagfishes are shown to be either supportive of the criticized paper’s main findings or trivial, arising from an incomplete understanding of the panbiogeographical method and synthesis and of methodological prejudice against this conceptual framework.

Briggs (2009) has criticized the paper ‘Panbiogeographical analysis of distribution patterns in hagfishes (Craniata: Myxinidae)’ by Cavalcanti & Gallo (2008) on the basis that it used what he deemed to be ‘an antiquated method of analysis’ that therefore would invalidate any findings reported in the paper. In his criticism, Briggs seems to resort more to rhetoric than to plain, sound facts, and shows an incomplete understanding of the basic tenets of the ‘antiquated’ methodology (panbiogeographical track analysis) he attempts to criticize. Here I will briefly address his criticisms, suggesting that they arise more from Briggs’s methological prejudice than from any fatal flaws of the criticized paper.

Briggs starts by stating that ‘most’ biogeogaphers do not use panbiogeography and presents a portrayal of panbiogeography as having been ‘superseded’ as a result of its combination with Hennig’s phylogenetic systematics to give rise to vicariance (cladistic) biogeography. However, many biogeographers (even those not especially tied to Croizat’s panbiogeography) recognize that panbiogeography (Croizat, 1958, 1964) stands clearly as an independent research programme (Craw & Weston, 1984; Morrone & Crisci, 1995; Craw et al., 1999), with many contributions, especially over the last decade (see Cavalcanti & Alperin, 2008). In the same context, he claims that ‘the modern approach to biogeography is an eclectic one, recognizing the importance of both vicariance and dispersal’; however, ‘modern’ biogeography has no unique, uniform approach, being instead divided up into a large number of independent paradigms and methodological approaches that may indeed characterize a discipline amidst a Kuhnian scientific revolution (Crisci, 2001).

He then criticizes the use of online databases, arguing that the identification of species may not always be correct. However, taxonomic correctness is a general problem with biological databases, affecting even GenBank (Page, 2006, 2008). Notwithstanding, large-scale online databases of museum specimen data are an increasingly important resource in biodiversity research (Canhos et al., 2004) and can hardly be deemed ‘antiquated’.

Briggs asserts that it is ‘obvious’ that hagfishes are Tertiary or more recent in age. But the only support he offers for this is that of fossil-calibrated molecular clocks, which logically can give only minimum ages. In fact, clock studies in general show that the fossil record is often inaccurate by tens of millions of years (Heads, 2005a,b).

He points out that most fishes show allopatric speciation and hagfishes are no different. This is correct – and is, indeed, a clear indication of the importance of vicariance in shaping the evolutionary history of marine organisms (Heads, 2005a; Parenti, 2007). Briggs also criticizes the trans-Atlantic classical track displayed by one of the hagfish species on the basis that ‘more than 100 fish species have trans-Atlantic distributions, most of them having apparently [my emphasis] migrated from west to east’. However, it is precisely these repeated distribution patterns that make ‘chance dispersal’ highly unlikely and demand a more general explanation, based on a common cause.

Last, but surely not least, Briggs claimed that, because of its many flaws, there would be ‘little justification for publication of the paper’, notwithstanding that it has passed the scrutiny of a peer-review process. Anyway, no idea or conceptual framework is made ‘antiquated’ simply by being proclaimed so.

Editor: Robert McDowall

Ancillary