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 19th 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 19th and early 20th 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.
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 21st 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
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.
Part II will begin with George A. Boulenger.
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.