Snapshots of Old Fish Phylogenies, Part I

Phylogenetics became a science with a consistent and objective methodology after the introduction of phylogenetic systematics, or cladistics, by Willi Hennig in the 1950s and 1960s (1, 2). As a life-long student of ichthyology and a scientist who specializes in phylogenetic methods, I have been interested in hypotheses and graphical depictions of phylogenetic relationships of ray-finned fishes that were published prior to the introduction of cladistics.

There is no longer much attention paid to these early views of fish phylogeny, which I think is unfortunate. There is an opinion that with the advent of cladistics, there is no need to study and understand these pre-cladistic hypotheses of fish relationships. However, it is important to note that most biologists in the 19^th Century immediately accepted Darwin’s fundamental thesis that all life on Earth shares common ancestry (3). Notable examples of ichthyologists that never accepted evolution include Louis Agassiz, a professor at Harvard University, and Albert K. L. G. Günther. The late 19^th and early 20^th Century ichthyologists that were thinking about how lineages of fishes were related to one another were explicitly attempting to create taxonomies that reflect hypothesized genealogical relationships. The problem is that prior to Hennig there was no standard method to infer these relationships, which meant that even when using the same type of information scientists could arrive at dramatically different conclusions about phylogeny.

Phylogeny of teleost fishes from E.D. Cope's book, Primary Factors of
Organic Evolution, 1896.

After starting to offer an ichthyology course at the University of Tennessee, and now at Yale University, I started to become interested in the history of the scientific study of fish phylogeny to augment and accentuate my lectures. My foray into pre-cladistic fish phylogenies was greatly helped by Colin Patterson’s masterly review that successfully demonstrates the influence fossil lineages had on the study of teleost relationships (4), with Patterson’s thesis that the most direct path to the inference of phylogeny is the study of living lineages (5).

It is not entirely clear to me what we can specifically learn by studying pre-cladistic efforts at fish phylogeny. Will we discover a hypothesis that is now again finding support in explicit post-Hennig phylogenetic analyses, or will we see reflections of both method and theory that will allow a more nuanced view of how we approach phylogeny inference in the 21^st Century? Even if there are no obvious undiscovered gems in these old phylogenetic trees, an understanding of this history will minimally allow us to appreciate the set of objective approaches shared by most comparative biologists interested in phylogeny, regardless of the group of organisms investigated. What I think we do see in these old trees is that the approach used by different scientists to infer relationships was idiosyncratic and often limited by the patterns of biological diversity exhibited in the specific organismal lineage.

Phylogeny of fishes from Gill's 1871 work,
Arrangement of the Families of Fishes, or
Classes Pisces, Marsipobranchii, and
Leptocardii

Among the earliest diagrammatic fish phylogenies are from 1866 (6) by Ernst Haeckel (1834-1919), who is credited with the introduction of the term “phylogeny.” One of the first comprehensive post-Darwin classifications of fishes was introduced by Edward D. Cope (7-9). Cope emphasized osteology as evidence for his conclusions on relationships of fishes (8, p. 446). Cope’s publications on ray-finned fish classification did not include any diagrammatic representation of phylogeny, but his work is noteworthy for the description of Actinopteri and the delimitation of Nematognathi that includes catfishes and sturgeons, and the decision to not recognize Müller’s Teleostei. Twenty-five years later Cope published a branching diagram that represented his views on relationships of what would encompass the teleosts in his book “Primary Factors of Organic Evolution (10).”

The earliest fish phylogeny shown here is from Theodore Gill’s very influential and informed classification of fishes that includes Cope’s Nematognathi and Müller’s Teleostei (11, p. xliii), which as mentioned above, was not recognized by Cope.

Phylogeny of ray-finned fishes from Dean's book

Fishes, Living and Fossil, 1895.

The next fish phylogeny shown here is from Bashford Dean’s (1867-1928) book “Fishes, living and fossil” published in 1895 (12). Dean does not discuss any specifics of this tree, but it appears to reflect Cope's classification because it shows a close relationship of catfish and sturgeons (Nematognathi). Dean was impressed with teleosts stating, “Teleosts have diverged most widely of all fishes from what seem to have been their primitive structural conditions.” Later, Dean notes that convergent evolution is pervasive among teleosts and this makes inferences regarding relationships within the group difficult, “Environment, like a mould, has impressed itself upon forms genetically remote, and in the end has place them side by side, apparently closely akin, similar in form and structure (12, p. 167).”

Part II will begin with George A. Boulenger.

References

1.  Hennig, W. 1950. Grundzüge einer Theorie der phylogenetischen Systematik. Berlin: Deutscher Zentralverlag.

2.  Hennig, W. 1966. Phylogenetic systematics. Urbana: University of Illinois Press.

3.  Darwin, C. 1859. On the origin of species. London: John Murray.

4.  Patterson, C. 1977. The contribution of paleontology to teleostean phylogeny, in Major patterns in vertebrate evolution, P.C. Hecht, P.C. Goody, and B.M. Hecht, Editors. Plenum Press: New York. p. 579-643.

5.  Patterson, C. 1981. Significance of fossils in determining evolutionary relationships. Annual Review of Ecology and Systematics. 12:195-223.

6.  Haeckel, E. 1866. Generalle morphologie der organismen. Berlin: G. Reimer.

7.  Cope, E.D. 1871. Observations on the systematic relations of the fishes. American Naturalist. 5:579-593.

8.  Cope, E.D. 1871. Contribution to the ichthyology of the Lesser Antilles. Transactions of the American Philosophical Society. N.S., 14:445-483.

9.  Cope, E.D. 1872. Observations on the systematic relations of the fishes. Proceedings of the American Society for the Advancement of Science. 20:317-343.

10.  Cope, E.D. 1896. Primary factors of organic evolution. Chicago: The Open Court Publishing Company.

11.  Gill, T.N. 1872. Arrangement of the families of fishes, or classes Pisces, Marsipobranchii, and Leptocardii. Smithsonian Miscellaneous Collections. 11:i-xlvi, 1-49.

12.  Dean, B. 1895. Fishes, living and fossil. New York: Columbia University Press.