Transcribed, by permission, from Tuatara (1984) Vol. 27 (1): 49-66
(The following text should not be treated as an authoritative citation substitute for the original)

MAYR vs. CROIZAT: CROIZAT vs. MAYR AN ENQUIRY

By Leon Croizat*
Technical Director, Jardin Botanico Xerofito, Apdo. 7344, Coro, Venzuela.
[* This manuscript was submitted to TUATARA shortly before Croizat’s death. It has been slightly edited by R. C. Craw but the style of the original is retained.]

ABSTRACT

In this posthumous paper, Croizat responds to criticisms of panbiogeography made by Ernst Mayr in two 1982 publications. The response emphasizes some of the key features in his approach to evolutionary biology and biogeography, including his views on disjunctive distributions, the Darwinian concept of dispersal from centres of origin, differential rates of evolution and the role of taxonomy in biogeographical analysis. The distinction between panbiogeography and vicariance biogeography is stressed.

Keywords: biogeography, Croizat, Darwin, evolution, Mayr, panbiogeography, vicariance.

INTRODUCTION

Anyone assuming that the literature of biogeography is necessarily scientific is in for a surprise, when learning that this literature is all to often subservient to strictly human foibles of conceit, obstinacy, illogical reasoning, etc. it is imperative that young students be informed of this because, if not, they will find it impossible to judge correctly what the press and their surrounding offer for their attention.

When I began in the 1940’s to take a positive interest in the field of the biogeographic distribution of animals and plants, I did not know that I was stepping into a field of research already dominated by a formidable duo: Drs. G. G. Simpson and Ernst Mayr, firmly entrenched at the time in the American Museum of Natural History. This due oater enrolled Dr. P. J. Darlington, Jr. of Harvard University and others. Being unable to see eye to eye with these luminaries, as I will presently explain, and quire ready to tell it to the world, I took almost unwillingly upon myself the task to fight, as a nearly unarmed David, the fury of a touchy heavily armed Goliath.

The zoogeography heralded by Simpson, Mayr, Darlington, Dobzansky, etc. needs not to be minutely picked apart for the benefit of the reader, when its very nature is made clear by the following opinion of Mayr:

“The distances between the various Antilles are so much shorter than the well substantiated jumps made by Pacific birds. I would not hesitate to accept transoceanic dispersal for the whole Antillean bird fauna without any major change of the present geological contours.” (Mayr; in Bond, 1948:208. c.f. Croizat, 1976:315; 1981:509).

The audacity of this fiat struck me on the spots as the most remarkable, in no way compatible with the little I had already observed of the distribution of a number of plants in and outside the Antilles. If what Mayr was so unceremoniously handing be correct, zoogeography and phytogeography, respectively, must be antithetic sciences; a postulate that I rejected as if by instinct. If the whole of the biogeography of the Caribbean region could be reduced to a series of jumps (by no means “well substantiated” whether in the New or Old World, contrary to Mayr’s extraordinary claim) dispersal as a science of causes and effects had no long reason to exist. Its most intricate problems could be disposed of with the affirmation that, e.g. Magnolia and Catharus have “jumped” from the Greater to the Lesser Antilles (or vice versa, who could say), using “means of dispersal” that, if absurd on the fact of it could always be excused as “mysterious”.

To cut it short, to ask Mayr, Simpson, Darlington, etc. for light in point of dispersal mean to ask them for bread and fish recalling the Biblical dictum of Matthew 7.9 but receiving in return stones and serpents. Left thus in the lurch by the luminaries of the day, who struck me repeatedly as but misguided theorists, I “invented” the “panbiogeography”. I can take little credit for such a discovery, because I was merely refurbishing the METHOD that four centuries before my time, had put Kepler in the condition of bringing down to earth the law of the skies. This method it is by no means of THEORY (notice the difference please!) consists purely and simply in accumulating fact, finding a way to render them graphic by orbits of tracks, finally comparing them on a statistical basis in order to abstract the causes and rules of their being what they FACTUALLY happen to be. Naturally, even this method will not work if left in the hands of parties lacking disciplined imagination, and a certain amount of general culture qualifying its beneficiary to distinguish as between mere details and basic essentials and the will to take pains in the execution of a promising pain. Anyhow, whatever the case be in details, the METHOD stands, and triumph it shall against or manner of theories.

The panbiogeographic method PANBIOGEOGRAPHY for short had me convinced in less than a month from the start that, as an instrument of investigation and positive knowledge it was infinitely superior to the zoogeographic theories trumpeted in the name of Darwinian “respectability” by Mayr, Simpson, Darlington etc. The case of these gentlemen rested on the notion of a centre of origin of the “species” out of which the “species” would emerge migrating by particular means of dispersal. This notion did not survive for me even causal consideration, and I promptly rejected it feeling what Ball was privileged to experience some thirty years later than my beginnings, and to express in neat words as follows:

“For me, Croizat’s contribution is one of liberation. Once we have escaped from the necessity of seeking restricted centres of origin, and from the necessity of plotting routes of dispersal from the centres, and once we have seen the possibilities unfolded by concepts of vicariance and differential form-making then a new world of ideas opens up for us.” (Ball, 1976:422).

Never has my lifework received a higher praise than in these few lines by Ball. Of course, they mean noting particular for those who are not al all interested in new worlds of ideas, and cling like ousters to “Darwinian tradition” and its supposed respectability.

Sure of my grounds, and ready to continue my work, I did not scruple taking issue in a spirit faithful to the form of convention with certain weighty statements by Mayr such as:

“Dealing with the origin of the bird-fauna of Hawaii, an ornithologist (Mayr 1943:47) writes as follows, “There is not a single serious modern student (I use the term serious advisedly) who believes in the former existence of land bridges between America and Hawaii, or between Polynesia and Hawaii.” (Croizat, 1952: 12).

Three years later, this author (Mayr 1946:12,36) submits a diagram intended to elucidate the components of the bird-world of the Americas…, and explains that favorable conditions were lacking for tropical life to pass freely between Asia and America in the latitude of the Aleutians. This explanation is followed by a statement to the effect that.

“The close relationship between the Old and New World members of the Pantropical element, whose ranges are now widely discontinuous, proves that such a faunal exchange must have taken place, and this places the zoogeographer in a real quandary. The customary solution for the problem is to ignore it…In view of the improbably of North Atlantic land connection, various attempts have been made of find new routes for the transpacific migration. I Mayr shall refrain from a discussion of the various proposed transpacific landbridges. They are faunistically possible, but find no geological support. There is, however, some evidence for considerable recent tectonic activity in and south of the Aleutian island region, as well as for a pronounced lowering of the floor of the Pacific as a whole.” (Mayr, 1946).

So far for my comment on Mayr’s zoogeography, to which I was careful to add:

“It is not our intention (Croizat’s), in quoting these statements and bringing forth this map, to imply that the author in question Mayr is glaringly inconsistent. Consistency as it has been shrewdly remarked may indeed be a more synonym of obstinacy”. (Croizat, 1952).

All in all, I felt that not even so exalted a figure as Dr. Ernst Mayr could be offended by what I have just quoted. True, its substance was devastating and the method it heralded hard indeed to refute, but so is science, ever changing, as it might seem, for the better. If Mayr, Simpson etc., obviously stood mired in quandaries that their theories could not avoid, shy should not Croizat bet welcome in producing a notable breakthrough fit to help everybody around?

Thus anticipating a lively, readily constructive discussion for and against the nascent panbiogeography - surely at that time particularly, a less than perfect doctrine in every detail - I was greatly mistaken. All I heard after a time from friendly sources was that Croizat was being made the object of an active whispering campaign unfavourable to his character, manner of working, etc. None of the zoogeographic luminaries of the day came out to refute my viewpoints, to dismiss the panbiogeography as a brainstorm, but - now it can be told (see Abele, 1982) - Simpson let it be known that Croizat wrote from an insane asylum, and Mayr had him dismissed as a contributor formally and substantially of prose so remote from science that no serious student could entertain Croizat at all. The strategy against my work and person was indeed murderous: the very name Croizat was taboo, must not be mentioned, and some 10,000 pages of my work should be treated as non-existent. Had I been made of less resilient and durable material, I should take my scientific life as ended in 1952 and - why not? - induced to commit suicide.

Such having been the situation, for at least a quarter century may the reader imagine how great was my surprise when learning that Dr. Ernst Mayr had printed in this very year 1982, two works, one a full fledged book, the other review; rigorously keeping up the old ant-Croizat taboo in the book, but throwing it out of the window in the review. I could hardly believe my eyes, all the more so in that Simpson and Darlington to the best of my knowledge still unflinchingly refuse to recognize that a certain Croizat ever was born to the light of this rather poor world. It was as if the Pope in the person of Dr Ernst Mayr had sold out the Vatican and turned Lutheran.

The first of these two titles is, The Growth of Biological Thought, with subtitle, Diversity, Evolution and Inheritance, (1982b). Pages 448-455 essentially cover the part of the opus dealing with biogeography. The second title is the review by Mayr of, Vicariance Biogeography, by Nelson & Rosen 1981, (1982a).

In the Growth of Biological Thought Mayr clings to his old taboo forbidding even to mention the name Croizat. Not so at all in the Review in which Mayr relents to the extent of repeatedly naming Croizat and “Croizatians”!

From the standpoint of psychology these two titles, dated of the same year stand as a priceless document of the manner in which Mayr things. It is easy to see by comparing the two that, with our without the burden of the anti-Croizat taboo, Mayr labors under the heavy liability of showing the world that he was right even when wrong. His writings are accordingly eminently forensic (forensic is mild) and as such they must be understood.

In view of the unusual nature of the Mariana I intend to bring before my reader, I will present the evidence in two major sections referring in one to Mayr under the anti-Croizat taboo, the other when free from it. In both sections, I will quite first Mayr’s own texts and then immediately append by own comments. I thus propose to liquidate a situation which has stood in the way of a normally progressive advance of biogeographic knowledge during the last forty years. Doctor Ernst Mayr may be anything and everything to everybody, but in my deliberate opinion at least he has no title to pose as a genuine biogeographer quite as much in 1948, when teaching Bond how to “understand” the ways and manner of dispersal in Antillean range (see my introductory page of the present article), as today.