Carabus - Morphocarabus and Eucarabus in Serbia

Populations of subgenus Morphocarabus and Eucarabus in Serbia, their morphology, diversity, distribution and speciation level.

The genital apparatus, of such importance in taxonomy and systematics of other insect groups, is poorly researched in genus Carabus Lineus, 1758. If we except studies of Ishikawa (1973, 1978, 1979, 1984), contributions in this sense are almost symbolical, especially when European authors are concerned. Thus the monograph published by Breuning (1932-1937) is still the most significant work dealing with taxonomy and systematics of Palearctic Carabus species.

The genital apparatus of the male, i.e. its internal structure endophallus with all its specialised structures represents the significant morphological characteristic for determination of the taxonomic status of species. Phylogenetically, endophallus as morphological characteristic clearly groups similars species within a single taxon. In literature, such an group of similar species is treated as subgenus, although similarity and stability of endophallus morphology suggest that these taxons could be treated as separate genera. It seems that the separation of Carabus into several genera would introduce more order in systematics of these insects. On the other hand, Carabus species as distinctly terricolous insects have diminished possibility of dispersion due to unfunctional wings, most often present in these insects in rudimentary form. The consequence is great species diversity which in some species results in formation of a great number of subspecies with clear geographical distribution. Diversity is not necessarily present in all populations of a species, but is more often distinct in areas labeled as refugial. This seems to be one of the reasons why diversity of certain species of Central and Northern Europe is less present when compared with the same species in the Balkans region. Therefore, the study of endophallus morphology as an objective morphological characteristic of these insects would surely advance taxonomy and systematics of Carabus species. In literature, the taxonomic status of a species, relationship between species and the status of their populations, is often the fruit of author's subjective attitude, while the methodological way of reaching the conclusions can not be followed.

This site aims to use World Wide Web to present the problem of the taxonomic status of some Carabus species populations in the Balkans region, speciation degree of populations within Morphocarabus subgenus (type species Carabus monilis), and pronounced diversity of Carabus (Eucarabus) ullrichi.

The basis of this presentation is its author's 1990 study entitled "Betraig zur Kenntnis der serbischen Population der Gattung Morphocarabus Gehin, 1885 (Coleoptera, Carabidae). Acta Mus. Maced. Sci. nat., 19, 4/157:85-110". In this paper Morphocarabus populations on the territory of the former Yugoslavia were treated as a subspecies of monilis species and classified - on the basis of the collected and reviewed material - as 5 subspecies and several nations.

Morphocarabus monilis ssp. simulator Kraatz, 1876
Morphocarabus monilis ssp. praecellens Palliardi, 1825
Morphocarabus monilis ssp. illigeri Dejean, 1826
Morphocarabus monilis ssp. bjelasnicensis Apfelbeck, 1902
Morphocarabus monilis ssp. semetrica Kraatz, 1878

This classification was, in a way, the result of trends present in literature from 70's and 80's mainly based on contributions of Mandl 1965, Machard 1979 and Ivanovs 1981.

Later additional research of morphological characteristics of endophallus in these populations showed that differentiation and the speciation degree of above quoted subspecies are developed up to the level of bona species. Thus the concept of C. (Morphocarabus) monilis as a singular species with important number of subspecies in this region is untenable. A disproportion in divergence of external morphological characteristics and endophallus morphology is striking. It is evident that monilis species populations originating in France have pronounced diversity of external morphology of elytra which is not followed by the morphological differentiation on endophallus level. On the contrary, the external morphology diversity in East and South-East Europe is often symbolical, but the differentiation in endophallus morphology is exceptionally pronounced. In the material concerning Morphocarabus population in Serbia, the morphological differentiation of endophallus in neighbouring populations was observed (stable and constant for each of populations studied). In geographical sense, these populations occupied clearly defined distribution areals.

Although phenotypically very close, all above mentioned populations manifested difference in form of endophallus. This difference was significant even in very similar populations where differences in sculpture of elytrae - as the most significant element in comparison of external morphology - was not so pronounced. Endophallus, as a morphological characteristic clearly systematized the populations studied into separate taxons. Great diversity of Carabus (Morphocarabus) monilis species is well known in literature, while the species nomenclature comprises 186 names (Deuve, 1994), whose taxonomic status is still not clear. Findings of stable characteristics in endophallus morphology in species of this subgenus suggest the differentiation of these species on the level of bona species for the Balkans populations.

Similar situation can be observed in Romanian Morphocarabus populations. It is certain that the intensive spetiation process occured in near past, so that they cling, in geographical sense, to their strict distribution areals; up to now the sympatricity of neighbouring species was not confirmed. Over long enough time period geographical barriers divided these populations so that the stability of endophallus morphology - representing potential mechanical isolation during mating - is evidently genotypically determined. Also, each population in its own distribution areal manifests different degrees of diversity in regard to the populations of the neighbouring taxon. The case of Balkans Morphocarabus populations thus represents a example of geographical (allopatric) speciation. Therefore, we maintain it is justified to treat thus differentiated taxons as bona species:

In spite of pronounced differences in endophallus morphology of Balkans Morphocarabus populations, phenotypically, differences between these species are not especially significant. On the contrary, in Eucarabus subgenus the species are, phenotypically clearly differentiated, while endophallus morphology seems sigificant only on the level of species. Although populations of these species manifest considerable diversity (Battony & Breuning, 1970; Pavicevic & Tosevski, 1988), clear changes of endophallus morphology were not observed even in the populations which are geographically distant and, phenotypically, significantly different. In the Serbian fauna, from the species of this subgenus only is Carabus (Eucarabus) ullrichi Germar, 1824 present. This species is widely distributed and occupies very different types of habitats, while Morphocarabus populations are local and occupy very narrowly defined eco-systems.

Basic differences observable in Serbian populations of ullrichi species are diffrences in elytra sculpture and colour. These differences are sometimes very pronounced in neighbouring populations, but can also be very discrete; therefore it is, methodologically, difficult to establish an objective model that could be clearly applicable in determination of their taxonomical status. Even in highly homogeneous populations, according to observed taxonomic characteristics (e.g. arrogans, gornjakensis, jaroslawi), can be found specimens (most frequently < 10%) which differ from the general habitus of the population observed. In this sense it can be said that each such population on the areal border with the neighbouring population represents a very heterogenous whole wherein predominate specimens possessing common taxonomic characteristics of both populations. Such transitory populations are most frequent, and they inhabit the greatest part of areal. Populations homogenously differentiated in regard to habitus are commonly encountered in a very limited geographical area.

If we accept Mayer's definition of subspecies as "an aggregate of phenotypically similar populations inhabiting a geographical subdivision of the range of that species and differing taxonomically from other populations of that species", then, generally speaking, colour of population is the only characteristic which determines the main phenotypical characteristics of populations so that they can be divided into monochromatic and polychromatic. Completely blue coloured specimens are genotypic characteristic of individua and probably are dominantly-recessively inherited. Blue colour is characteristic of some populations in the eastern part of distribution areal of ullrichi species. In Serbia, such specimens are present only in n. jarosawi and n. transdiernae.

This division seems most acceptable as the whole corpus of ullrichi species could be divided into two subspecies: nominal (monochromatic) ssp. ullrichi Germar, 1824 and polychromatic ssp. fastuosus Palliardi, 1825. Numerous populations within these subspecies with all their differences, commonly observable in the quality of elytrae sculpture, nevertheless possess only infraspecific characteristic and the most acceptable procedure is to treat them as nations, although from the standpoint of valid ICZN they are of no taxonomic significance. Pronounced diversity within populations, particularly visible in East Serbia is significant and objectively present, but insufficient to treat some of these populations as a separate taxon on the level of subspecies. This is the most sensitive of the decision a taxonomist makes when faced with a similar case: should such populations be proclaimed a subspecies, thereby meeting ICZN criteria or should the present diversity be shown in a manner that objectively reflects the field situation. In that context, a nation represents a population or a group of populations (which can be dispersed within the areal) with their own taxonomic characteristics but belongs to an agregate of phenotypically similar populations marked as subspecies, possessing a clear geographical distribution. In a geographical sense, there is a distinct border of areal inhabited by monochromatic and polychromatic populations. Such a clear geographical demarcation is drastically manifest in Gornjak Gorge where two nations, two different subspecies are sharply separated by a small mountain river.

Literature:

Battoni, S. & Breuning, S., 1970. Una nuova natio di Carabus ullrichi Germ. della Serbia Orientale. Bullettino della Societa Entomologica Italiana. Volume 102: 9-10. Genova.
Breuning, S. 1932-1937. Monographie der Gattung Carabus L.- Bestimmungstabellen der europäischen Coleopteren, 104-110, ed. Troppau.
Deuve T., 1994. Une classification de Genre Carabus. Vol. 5, pp. 296. ed. Sciences Nat.
Ishikawa, R., 1973. Notes on some basic problems in the taxonomy and the phylogeny of the subtribe Carabina (Coleoptera, Carabidae). Bull. Natn. Sci. Mus. Tokyo. 191-215.
Ishikawa, R., 1978. A revision of the higher taxa of the subtribe Carabina (Coleoptera, Carabidae). Bull. Natn. Sci. Mus. Ser. A (Zool.), (1):45-68.
Ishikawa, R., 1979. A preliminary revision of the Carabogenici of the subtribe Carabina (Coleoptera, Carabidae). Bull. Natn. Sci. Mus. Serr. A (Zool.), 5(2):95-114.
Ishikawa, R., 1984. Phylogeny and Subgeneric classification of the Genus Chaetocarabus (Coleoptera Carabidae). Kontyu. Tokio (1):94-109.
Pavicevic D., & Tosevski I., 1988. Einige neue nationes von Carabus (Eucarabus) ullrichi fastuosus Palliardi aus Nordost-Serbien (Coleoptera, Carabidae). Fragmenta Balcanica, Vol.13:113-118.
Tosevski I., 1990. Betraig zur Kenntnis der serbischen Population der Gattung Morphocarabus Gehin, 1885 (Coleoptera, Carabidae). Acta Mus. Maced. Sci. nat., 19, 4/157:85-110.