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Corresponding author: Ilya A. Gavrilov-Zimin ( coccids@gmail.com ) Academic editor: Nina Bulatova
© 2020 Ilya A. Gavrilov-Zimin.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Gavrilov-Zimin IA (2020) Homologous series by Nikolai Vavilov in the phylogeny of Homoptera. Comparative Cytogenetics 14(4): 589-596. https://doi.org/10.3897/CompCytogen.v14.i4.60894
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The paper briefly discusses the most impressive examples of the Nikolai Vavilov’s “Law of homologous series” in the evolution of one of the largest animal groups, homopterous insects, which comprise about 65,000 recent species in the world fauna. Different taxonomic and phylogenetic characters (morpho-anatomical, cytogenetic, reproductive and others) are considered at the taxonomic ranks of the order, suborder, superfamily and family.
Aphids, cicadas, homologous variability, parallel evolution, psyllids, scale insects, whiteflies
The famous geneticist and evolutionist Nikolai I. Vavilov (1887–1943) manifested his “Law of homologous series in variation” one hundred years ago (
The present paper will briefly describe Vavilov’s Law of homologous series in the evolution of one of the largest animal groups, homopterous insects. The order Homoptera comprises about 65,000 recent species in the world fauna. It is subdivided into five recent suborders: Aphidinea (about 6,000 species), Coccinea (8,000 species), Psyllinea (3,500 species), Aleyrodinea (1,500 species) and Cicadinea (47,000 species). More detailed information about general classification and nomenclature of these taxonomic groups can be found, for example, in the monographs of
Some authors (for example,
Reconstruction of the phylogeny of Homoptera and related insects, placed on geochronological scale (after
On the other hand, the presence of the fields of wax glands, well-studied on large material in all archaic groups of Homoptera as well as in many younger groups of this order (see, for example,
Another phylogenetically important question is the origin of the filter chamber in the digestive tract of Homoptera (see the review in
Phylogenetic relationships among suborders of Homoptera are more or less understood now and the differences between synapomorphies and parallelisms are rather clear. It seems that all modern specialists (irrespective of their general theoretical views) agree with the close relationships in the following combination: Coccinea + Aphidinea, Psyllinea + Aleyrodinea and separately Cicadinea. The sequence of the evolutionary origin of these groups as well as the possible origin of one group within another still remain debatable among taxonomists (see, for example, discussion in
Several examples of Vavilov’s Law at this taxonomic level could be mentioned: cytogenetic and ontogenetic parallelisms as a larval meiosis (known in scale insects, aphids and whiteflies, but unknown in psyllids) (Fig.
In accordance with Vavilov’s law, the number of homologous series increases significantly at lower taxonomic ranks. That is why, only examples primarily based on biology of scale insects, the group which is more familiar to the author, will be provided. The evolutionary advanced scale insect superfamily Coccoidea (so-called “neococcids”) is characterized by a peculiar heterochromatinization of paternal haploid set of chromosomes in males (Fig.
We (
In many scale insect families, the whole “cycles of homologous variability” are to be observed in the accordance to the predictive modeling, based on Vavilov’s Law (1920). Thus, for example, the originally oviparous scale insects, evolved into marsupial or pseudomarsupial groups, already inside of the family Margarodidae s.l., which, in turn, gave the rise to the groups with a complete obligate ovoviviparity and then with an incomplete facultative ovoviviparity, when the oviposition of the slightly developed eggs occurs in the external wax ovisacs; in such a case, the secondary oviposition is almost restored in the course of evolution (
It is impossible to include all other homologous characters representing the evolution of wax glands, morphology of the anal apparatus, chaetotaxy, etc. in various scale insect families and genera; such comparison will require monographic treatment of numerous taxa. Many additional illustrations could be found, for example, in bi-volume book “Palaearctic mealybugs…” (
To conclude, even this very brief review demonstrates difficulty in distinguishing Vavilov’s homologies from the cladistic synapomorphies in the order Homoptera. In some cases, the differences are clear and easily arguable, whereas in other examples, the hypothetical assumptions, basing on the current, often very limited knowledge of the subject, could only be provided. Taking this into consideration, Vavilov’s Law becomes a very uncomfortable factor in the practical work of the phylogeneticists and taxonomists, especially those who work in the field of the cladistic paradigm. Ideally, the researcher, when introducing a new character in phylogenetic analysis, should demonstrate not only the apomophic condition of this character in the putative sister taxa, but also he or she should prove that the character evolved only once in the hypothetical common ancestor, but not as a result of homologous variation in the related taxa. Such an approach would need long-time comprehensive study of each potential phylogenetic character in the numerous (ideally in all) species and genera of the analyzed higher taxon, which is, unfortunately, impossible in the frame of short-time projects, dominant now in modern day biology.
Financial support for this study was provided by the grant no. 19-54-18002 from the Russian Foundation for Basic Research. The work with the collection of the Zoological Institute, Russian Academy of Sciences was realized according to the state project AAAA-A19-119020790106-0. The author thanks Dr. D.A. Dmitriev and Dr. R. Angus for the linguistic corrections of the text.