I Coleotteri Carabidi delle Alpi occidentali (Coleoptera, Carabidae)

Abstract

BIOGEOGHAPHIA — vol. XVI — 1992 {Pubb/icato il 31 dioembre 1992) ll popolamento delle Alpi Occidental] I Coleotteri Carabidi delle Alpi occidentali e centro—occidental:i (Coleoptera, Carabidae)(qq) ACHILLE CASALE(q“q) e AUGUSTO VIGNA TAGLIANTI( ) (”“q) Istzfzzto dzq Zoologzkz (le[[’U/zz'z2er5z't(2, Vzkz Mzzrom, 25 — 07100 Szzsszzri '9 Dz'pmqtz'/7zem‘0 512' Biologzkz Aiziimzle e de[[’Uo/720 (Zoologzkz), U/zz'vers1‘t:i 511' Roma «La Szzpielzza», Viale 5/e[[’U27z'versz'tci, 32 - 00185 Roma SUMMARY A tentative synthesis of the Carabid fauna of the Western] Alps, from a biogeographical, ecological. and historical point of view, is presented. Only the Italian side of the Western part of the Alpine chain is considered: from the Ligurian Alps (Colle di Cadibona) to the Ossola valley (basin of the Toce river), including the Maritime, Cottian, Graian, Pennine and Western Lepontine Alps. Main features of the landscape are: 1. strong geological, geo-morphological and orogenetic complexity, with the presence of the main premesozoic, external cristalline massifs and of the highest peaks of the whole Alpine chain (several more than 4000 m); 2. almost total absence of limestone, lacking a prealpine belt. Only the Ligurian Alps (object of a previous biogeographical analysis by the same authors, 1985) are entirely calcareous and well Carsified, with deep and large hypogean systems (also at high altitude); 3. the geographic position, bet- ween central Europe and the Padanian plain, not far from the Mediterranean sea in the Western part (Ligurian and Maritime Alps); 4. finally, a puzzled climate situation, \vith xero-thermic areas (500-700 mm of rain per year) also in some intra-alpine sectors. like the Susa and Aosta valleys, close to highly rainy areas (2500-3000 mm per year). Thus, sub-mediterranean vegetation types, close to «cool-moist» forests (Czzrm/lea, Fagz/5, Betzrla, Picea, Al:/‘ex, L:/rix), coexist with alpine environments above the timber line. In our opinion, these facts explain the eterogeneity, the richness, the variety, and the interest of the Carabicl fauna of the area: the high number of species (426 ascertained so far, about 1/3 of the whole Italian Carabid fauna), the high number of euri- or stenoendemites (126, about 30% of the species), and the complex origins and/or affinities of different taxa. A relatively large number of species (127, i.e. 29.81%) belongs to European chorotypes, and even more (166, i.e. 38.96%) of Holarctic (Holarctic, Palaearctic, West-Palaearctic, Asiatic-European, Siberian-European, Central-Asiatic-European, Central- Asiatic—European«Mediterranean, Turanic—Eur0pean, Turanic—Eur0pean-Mediterranean, European—Mediter— ranean) chorotypes, from Northern or North—Eastern cold forests or Steppes, during climatic changes in the Plio-Pleistocene. Only few species are boreal—orophilous elements (Nebr/21 I'£lf€IE(:‘/II, A/zmm erI't1/fat and A/mim qt/eme- /2'); many orophilous, forest—dwelling, riparian and hygrophilous species, are also of northern origin. A small, but interesting group of elements (belonging to the genera Liciizzu, C://at/J1/X, and several Harpalini), originally from the Mediterranean area or temperate Steppes, during the hypsothermic periods of the Olocene, reached the \Western Alps and persist in xerotherrnic biotopes. Finally, others, tied to grasslands, sometimes sperrnophagous, of the genera Op/Jo/ms, Harpzz/1/3, Cy/m’/It/ix, recently increased their range of distribution as a consequence of human activities in agricultural use, overgrazing and deforestation. The most important group of species, however, is represented by the large number (126, i.e. 29.57%) of endemics, either euriendemics to VY/estern Alps, or stenoendemics both to single sectors and to very small biotopes: the «famous» Ca/‘almr nly//Ipiae and C. cyr/Jroit/ex, the high altitude C_iic/Jrm‘ and Tree/Jz/1‘ species, the subterranean Trechini of the genera Dztvzzlizu, Agostilzia, D0der0z‘I'eC/mi‘, many Pterostichini, and others. Most of them must be considered as’, pre—Qu-aternarian elements, with affinities either in (qq') Ricerche effettuate con contributi del C.N.R. («Modelli storici e dinamici in zoogeografia e loro basi tassonomiche e corologiche») e del M.U.R.S.T. 40% («Componenti extrapaleartiche della fauna italia- na e mecliterranea») e 60% (Universita di Sassari).