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1955 The Lepidopterists' News 199
ON THE PHYLOGENETIC RELATIONS IN THE BISTONINiE (GEOMET-RID^E), WITH SPECIAL REGARD TO PCECILOPSIS
by Dalibor Povolny and Josef Nosek
In our recent work (Povolny & Nosek, 1954) we tried to illustrate the position of Poecilopsis isabellce Harrison and its zoogeographic character. This was possible only in simultaneous comparison of several groups of the geometrid subfamily Bistoninae, which resulted in some important viewpoints on the phylogenetical relations of this group. To illustrate them with special regard to the genus Poecilopsis Harrison is the theme of this study. It is an agreeable duty to thank Dr. T. N. Freeman for providing us the single non-European species of Poecilopsis—P. rachelce Hulst—which we could not obtain in European institutions and for his very kind help in our work.
HARRISON was the first author pointing to the great heterogeny of the old genus Biston Leach, towards the beginning of this century. In 1915 PROUT (in Seitz) gave a more progressive systematical conception of the Bistoninae, if we compare it with that one of the older authors ( Staudinger, Spuler, and others), though he does not include P. isabellce. This conception by PROUT was based mostly upon external morphology (venation, legs and their spines, palpi, proboscis, etc.), and in limited dimension also upon anatomical criteria, though Pierce has in 1914 already published a good analysis of the genitalia of the British Bistoninae. Pointing to the work mainly of HARRISON, PIERCE, and of other authors, similarly as to our own study, we do not intend to give once more a detailed morphological description of the single species, but we shall instead discuss the known facts from the viewpoint of phylogeny.
It is evident that the present Bistoninae consist substantially of two large groups of genera and species. The first group contains older and mostly isolated species and genera. They all have a bifurcated ending of the uncus and mostly differentiated male genitalia. Two branches can be distinguished in this group. The first contains the forms related to Biston strataria Hfn. and Amphidasis betularia L., the second being certainly congeneric with the first. It seems very probable that these are simultaneously the forms connecting the Bistoninae with the Ennominae (through Gonodontis), as indicated in 1913. This is shown in the presence of the wings in both sexes, and in the ecology, as Biston appear much later than other Bistoninae, which appear mostly in the early spring. The other branch of the first group is represented by genera and species such as Phigalia (pedaria F.), Macrobiston, and Apocheiwia (hispidaria Schiff.). These belong to the true Bistoninae and represent their older forms.
The second group is represented by the relatively very homogeneous forms of monophyletic origin, which must be also much younger than the first group. This is shown in their surprising morphological uniformity and simple genitalia. These forms are concentrated in three genera representing the single branches of development of this group. These genera are Lycia Hbn., Nyssia Dup. (Ithysia Hbn.) and Poecilopsis, of which many forms are of strictly European origin. The close relation of this group is shown not only in morphology but also genetically, because most species tend to rich hybridization.
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Vol.9: no.6
In contrast to the first group, whose members are distributed on the enormous Palearctic area and penetrate also northern America, the distribution of many members of the second group is more limited, and some are strictly European.
Top, P. lapponaria; second, P. pomonaria; third, P. isabellce; bottom, P. rachelce. (Female signum bur see left; male genitalia right.)
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1955
The Lepidopterists' News
201
Ecologically the two groups also differ greatly. Whereas members of the first group feed only on trees, those of the second are in their majority adapted to herbaceous plants. The first group are, indeed, forest-forms; in the second group inhabitants of prairies prevail. The oldest forms of the second group are contained in the genus Lycia {hirtaria and ursaria) representing the surviving branch of the primitive early Bistoninas. The second two branches (Nyssia and Pcecilopsis) are the youngest genera of the Bistoninas. HARRISON (1913) considered Poecilopsis younger than Nyssia, but it is very difficult to decide exactly the relative age of these two groups. Much more, it seems that they are both young, independent parallel branches of the Bistoninae.
Poecilopsfs
/pv Nyssia
X^QLycia
Rpocheima Phiqalia
OBiston Gonodonto Ennomos
The species of Nyssia are decided inhabitants of herbaceous growth and centered in central Europe, whereas Lycia and Biston (s. str.) are of Siberian origin. HARRISON (1913) considered Nyssia zonaria Schiff. the most specialized Nyssia. It is to point, however, that this species has a wider distribution than all other Nyssia and is rather polyphagous. The circumstances show that N. zonaria is an eurytopic species, whereas the other Nyssia are specialised stenotopic forms of the Alps and of the mountains of the Balkans. Some of them are in statu nascendi, representing plastic and recently originating forms.
Poecilopsis contains four species (pomonaria Hbn., isabellce, lapponaria Boisd., and rachelce), P. pomonaria being original and comparatively isolated. Morphologically the species are very close, but evidently P, pomonaria is closely related to P. isabellce, whereas P. lapponaria and P. rachelce are in development. In contrast to Nyssia, which are oligophagous, Poecilopsis are substantially polyphagous forms inhabiting various trees of forests and plants in the boreal prairies. Though we can see the tendency to foodplant specialization in some of them, it is evident that they must have been polyphagous, as most of them they can be reared on Betula, Cratcegus, Salix, etc. The broadest polyphagy is seen in P. pomonaria, feeding mostly various forest trees (Quercus, Cratcegus,
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202 POVOLNY & NOSEK: Poecilopsis Vol.9: no.6
but also Malm, etc.), whereas P. isabellce is specialised on Larix. P. lapponaria feeds on various herbs {Erica, Calluna), but also trees (Betula, Crataegus), and about P. rachelce Harrison writes that this species "has a similar weakness for dwarf willows on the prairies". It seems that P. pomonaria is the derivate of the ancestral Pcecilopsis-iorm living in the Eurasiatic forest-zone of mild climate. The specialization of these forms in the European region on the deciduous conifer Larix produced P. isabellce. The populations of the boreal forests developed to P. lapponaria in Europe and to P. rachelce in northern America.
Some authors have presumed that P. lapponaria and P. isabellce in Europe are of boreoalpine history and of postglacial origin. Respecting not the fact that P. isabellce Harr. is related more with P. pomonaria Hbn. than with P. lapponaria Boisd., we see further convincing facts showing the contrary. Beirne (1947) proved that even much longer periods than Holocene (about 20,000 years) were not sufficient for developing species by the isolation of P. lapponaria and Nyssia zonaria in the British Isles, where the presence of P. lapponaria is from the first wiirm-stadial (120,000 years) and of N. zonaria from the first wiirm-interstadial age (80,000 years), building races differing little from the continental populations. P. isabellce is closely dependent upon the European Larix, which has nothing to do with the European glacial-period, and their histories are in common. P. isabellce was carried beyond the original area of the European Larix by the activity of the man, and in certain secondary habitats it may cause great damage on its foodplant. It is to be decided, finally, what route brought P. rachelce to its present native country. The close relationship between P. lapponaria and P. rachelce, and the present known distribution of P. lapponaria suggest the possible historical connection through the presumed continental bridge of Iceland and the present islands of the northern Atlantic. However, the eastern distribution of P. lapponaria and its limits in Europe or Asia, and the western distribution of P. rachelce in Canada are not known.
It is to be concluded that Bistoninae are of Angarian origin. The diffe-renciation of the first group (Biston, Phigalia, Apocheima) must have been finished in the upper Pliocene there. Towards its end the mighty stream of the Angarian fauna was drawn westwards by the climatic changes of the starting glacial and in the European region the specialization and development of the Bistoninse was continued in the Pleistocene by the origin of Nyssia and Poecilopsis. The first of them developed by specialisation to the herbaceous vegetation in the Alps and Balkans. The second originated in the forests of central and northern Europe. The origin and distribution of Poecilopsis rachelce requires further study.
References
Beirne B.P., 1947. The origin and history of the British Macro-Lepidoptera. Trans.
Royal Ent. Soc. London 98: 273-372. Harrison J.W.H., 1913- The hybrid Bistoninae Etudes hep. Comp. 7: 343-482. Nosek, J., & D. Povolny, 1954. Vvznamny skudce modfinu Poecilopsis isabellce Harr.
\Po3cilopsis isabellce Harr. als Larchenschadling]. Folia Zool. Ent. 3(17): 13-36
[contains the complete references to this work].
Institute of Applied Entomology, Zem£delska 1, Brno, CZECHOSLOVAKIA