CLAUDI.O CHEMINl (CClllro .:It Erologw AlpiJhl. Viote M.unte Brmdofle, Tren/o)

BIOGEOGRAPHIC PATIERNS IN THE OPILTONIDS OF (Arachnida: OpiJionesJ

ABSTRACT. The biogeography of the 123 o()ilionid species hitherto known (rom Ir.aJy is analysed by clustering the Jisrributions imo few main range panerns. Specie::; richness de­ creases (rom north to south, showing a strong peninsula effect. European (sJ.l ranges are dominam, bur [hey .strongly dt:"cre

Key words: biogeography, Araclmida, Opiliones, Italy.

IUASSUNTO. Crtl'otteriSliche hiogeografiche degli opilioni ilaliani. La biogeografia deUe 123 specie di opilioni auua!meme note per l'haM e anamata raggruppwdo le disrribuzioni in pochi cororipi priru.:ipali... I..ot diversita di sp~cie diminuisce fortemente cia nord a sud, ~viden· ziando un forte effeuo penisola. Prevalgono i corotipi e:uropei (5J.), che tutcavia dcdinano forremente a sud; i corotipi meditcrranei (s.U aumcnr.ano percenmalmenre a sud e sopratnlt­ to in Sicilia e Sardegna. Le specie endemiche rappresentano il })% del totale, con un elevaco numero di ennemiti ncUe Alpi meridionali; la componemc endemica liumenta percentual­ mente yerso il sud e le isole. La maggior parte deUe specie presenta lIreali ristretti; ne risulta una clevara variazionc faunlsuca lungo gr-aclienti geografici Le specie dominanti localmeme hanno di regola distrihuzioni memo·ampie, ma anche alcune specie ad areale cistretto eviden­ ziano elevate abbonetanze locati.

Parole chiave: biogeografia, Arachnida, Opiliones, ltalia.

The recent increase of interest in biogeography results from the at­ tention devoted to the problems of preservation of the biological di­ versity. the need for monitoring the effects of global changes on natural systems, 1~nd also from the fruits of the biotechnological revolution enjoyed by biogeography and [elated disciplines (Haydon ei al., 1994). Besides. [here appears to be an increasing awareness that studies on community ecology have to take into consideration the roles of biolo­ gical processes, but also of regional. historical and stochastic processes. At last, there seems to be an end to that "eclipse of history" which . CL\UDlO CHEMIN! 532 BIOGEOGRAI'I Lie PAlTER'JS IN THE OPILlONlDS OF ITAI.Y 533 forced the study of diversity illto the ecological discipline only (Ricklefs, heterogeneity. Cemral [tall' includes the highest moumains of the 1987). Apennine chain and the Tyrrhenian and Adriatic coasts. Southern Italv Biogeographical analyses still have to face a series of difficulties. A includes rhe southern Apennines and rhe south-Adriatic, Ionian and general problem is rhe lack of sound descriptive data, to be compared sourh-Tyrrhenian coasts. and analysed [0 test general hypotheses (Hengeveld, 1990). Biogeo­ graphical data and analyses are often so specialistic and punctiform, with regard both to geographical and taxonomic levels, that they are not RANGE PAlTERN, easily suitable to broader scale analysis and to general theories or models, especially considering regions and faunas reflecting a complex Italy constitutes a heterogeneus biogeographical area, running from physical history. the Alpine glaciers to the Mediterranean coasts, with wide gradients of La Greca (1964) gave a basic analysis of the biogeographic patterns actual environmental conditions and with a complex physical history, of the Italian fauna. Vigna et al. (1992) proposed a revised classification covering tectonic and eustatic events, glacial and interglacial periods, and nomenclature of the range patterns of the W-Palaearctic fauna, in land-bridge emersion and submersion. order to provide biogeographers dealing with the Italian fauna with Most opilionids of the Iralian fauna show geographically restricted more general and comparable chorotypes. distributions, covering only a small part of Europe or of the Medi­ In the present paper, an attempt is made to cluster the data on the terranean; many ranges have their centre in Italy, and often they are biogeographic patterns of the Italian opilionids into easily inrerpretable restricted to a part of Italy. categories, in order to contribute to a general hiogeographical knowl­ The species with an Alpine range panern are numerous; in some edge of the taxon and of the region. Fine·scale biogeographical analyses cases this range pattern shows extensions towards the Apennines or the on the opilionids from restricted Italian areas can be found in a series of , or towards central or west Europe. The Italian Alps are works by Marcellino (e.g. 1986, q.v. for further references). The bio­ reached also by distributions which appear to be marginal with regard geography of the opilionids from the whole Alp chain was analysed by to the Italian territory (e.g., west European species in the western Alps Martens (1978). or east European species in the eastern Alps). There is a sizeable group The opilionid fauna of Italy, as listed by Chemini (1995), consisted of of Apennine species, some of which range southward to Sicily. The 120 species. Three species of Holoscotolemon, recently described by Mediterranean species arc mostly west Mediterranean, only few species Tedeschi & Sciaky (1994), have been added to such checklist. The two are trans·Ionian. The European ranges are mostly south European, subspecies of Dasylobus argentatus are considered here as differenr sometimes central European, rarely easr· or west-European ones. The biogeographical units, so 124 units are treated in all. The present ar­ number of geographically widespread species, as Palaearctic or Ho. rangement would require some taxonomic and distrihutional amend­ laretic ones, but also of species widely dispersed in Europe or in the ments and addenda, but it is a reasonahle picture of the real status of rhe Mediterranean, is low; yet, some widespread species have a great local Italian opilionid fauna. frequency of occurrence and are dominant species in many opilionid' All three traditional suborders of Opiliones occur in Italy. Three conununities from Italy. species belong to Cyphophthalmi (a "Gondwanaland" group), II to The geographical distributions of the Italian opilionids were grouped Laniatores (a mainly tropical group), the remaining 109 to Palpatores (a into few basic range patterns, which are suitable to be analysed and cosmopolitan group, dominant in temperate areas). companjd with those of other taxa within the Western Palaearctic re­ The territory of Italy was considered as a whole and as articulated gion. Most species were referable to European (s.I.) or Mediterranean into 5 areas: northern, central and , and the islands of (s.1.) patterns; the distinction between southern European and Medi­ Sicily and Sardinia (Fig. 4). includes the Italian Alps and terranean patterns was difficult in some cases, and it was performed the northern part of the Apennines, the plain of the Po Valley, Ligurian taking into account the distributional trend of the species under con­ and north-Adriatic coasts; the area is characterized by strong climatic sideration and that of related species. 534 CLAUDIO CHEMINI BIOGEOGRAPIIIC PATIERNS IN THE OPIUONIDS OF ITALY 535

The results (fig. 1) show a dominance of European species (44 %, GEOGRAPHICAL GRADIENTS mostly south European species), a lower number of Mediterranean species {l7%l, and the great percentage of halian endemics (35%). lIaly spans over several degrees of latitude (47°_35" N), thus resulting The distributions of the endemic species are illustrated in fig. 2. in a north-soUIh trend with regard to number and composition of Alpine endemism is numerically prevailing (37%), with a high number species and to range patterns. of species restricred to the pa rt of the chain running from Lombardia to As for the variation in the numbers of species recorded from the 5 . It is remarkable the group of narrow endemics recorded from pans of Italy under consideration, a strong peninsula effect is evident the mountains near I3ergamo, which appear to be a restricted centre of (Fig. 4), with decrease in the diversity from north ro south, especially in endemism for several families, representing all three suborders (Sir­ the shifting from continental Italy to peninsular Italy; decrease in di­ onidae, Cladonychiidae, Nemasromatidae, Ischyropsalididae, Pha­ versity is stronger in the Islands. langiidae). Two endemic species occur in the area western Alps­ The faunal similarities among the 5 considered areas were analysed northern Apennines, 11 in the Apennines, 4 in the southern Apennines by using SvHensen's index (clustering by WPGMA method). The results and Sicily. Nine endemic species are restricted to Sicily (5) or Sardinia (Fig. 3l show the high similarity between the 2 parts of the peninsular (4). One species Uschyropsalis adamiz1 shows a Tyrrhenian distribution Italy (central and southern Italy), which differ clearly from the northern (coasts of north-western Italy, central and southern Italy, Sardinia). Italy fauna, and the peculiarities of Sicily and Sardinia. Besides the latitudinal effect (affecting both composition and number WlO of species), the Italian opilionid fauna shows a longitudinal effect (af­

SICllY fecting mainly the species composition). 111is is evident in the Alps, with ALPS range patterns restricted to eastern, or central, or western parts of the

ENO .lOl TYRRHEI'.1AN Chain, resulting in some species replacement along an east-west gra­ dient. Peninsular Italy divides the Mediterranean in two parts, east and APENH:+SICI.Y west, where the biogeographic patterns reflect complex dispersal and geophysical events. In the opilionids. the west-Mediterranean range 1 2 . patterns seem to prevail over the east-Mediterranean ones, which are -..- - ,... ,. limited mainly to few trans-Ionic units. MED APENNINES The percent differences of the distribution patterns in the 5 parts of Italy are illustrated in Fig. 4. The latitudinal variation is striking: de- Fig. I . Basic range patterns of rhe Italian opilionids (EUR European, MED Medirerranean. END endemic, WIn widespread species), Fig. 2 . Geographical distributions of rhe endemic opilionids of Italy. o p p p p p p p p p ... (JJ - - " '" .. '" " '" Italian endemic species can be referred to the two basic distribution c patterns (European and Mediterranean) on the grounds of historical, S ecological and taxonomic evaluations. Sixteen endemic species appear to have a southern European gravitation, 27 a Mediterranean one. After N , • this splitting of the endemics, the percentages of European and Medi­ ,• SA terranean units in the whole opilionid fauna of Italy reach 57 % and SI 39% respectively. The endemics with European range pattern occur in northern Italy (Alps); Mediterranean endemics are distributed along the Fig. , - Dendrogram of similarity (S0rensen'~ index, W"PGMA method) of [he peninsular Italy and in the Islands, with some occurrence also in opilionid f,unas from northern (N), central (Cl. ,ou,hem Italy (5), Sicily (S!) and northern Italy (Maritime Alps, Ligurian coast, northern Apennines). Sacdinia-(SM 536 CLAumo CHEMINI BIOG£O(~RAPH[C PATfERNS IN THE OPILlONlDS or ITALY 5>7

'MO Most opilionid species have small ranges, which results in a re­ placement of species and range patterns along geographical gradients. Northern [wly, widely connected to European continent. shelters 75% of the Ttalian species; it collects the ranges of numerous species with European (s.l.) distributions, and also Mediterranean ranges. SOllth­ ward, along the Apennine Italy and in the Islands, most of these species disappear. there is a faunal replacement and the diversity decreases, even though in presence of interesting endemics.

LOCAL AJ!UNDANCE AND RANGE SIZE

Species compositions and range patlerns of the Italian opilionids "'0 reflect a long history of geophysical events (tectonics, eustacy, glacia­ lions): likely, the build-up of local opilionid faunas results mainly from regional processes. An analysis of the correlations between local abundance and range size of the species shows that most abundant species have large ranges. ENO @ The dominant species in most opilionid communities from mountain belts is Mitopus morio, one of the very few Holarctic species. Other widespread species with great frequency of occurrence in Italy are Trogulus I/epae!ormis. Phalal/gium opiba, LAcinius horridus and Odiellus spinosus. Lophopilio palpinalis, widely diffused in central Europe, is WOO frequent in northern Italy; Metaphalangium propillquum, a species with a large Mediterranean range, is very abundant in the Mediterranean

END . Italy. High local abundances are shown also by some species with Italian gravitation but with extension of the ranges northward (central Europe) ...0 and/or southward (Mediterranean lands), resulting from a wide ecolo­ "EO gical tolerance (Nemastoma dentigerum, Nelima semproni, Opilia canestrillii, Dasylobus grani!erus). In northern Italy a great frequency of Fig. 4 - Basic range patterns of the opilionid faWlas from northern, central, southern Italy, Sicily and Sardinia (EUR European, MED Mediterrwean. END endemics. occurrence is shown by some species with range centre in the Alps but Will widespread species), Numbers of species are indicated in circles on the map. with some dispersal to central Europe (Platybunus bucephalus, Platy­ bunm pinetarum, Paranemastama quadripunctatum, Leiobunum lim­ crease of European species from 59% to zero, increase of Mediterra­ batum), or to the Balkans (Hislneostama dentipalpe, Ami/enus our­ nean species from 11 % to 63%. Endemics are 25% of the opilionids of antiacus)., _Also geographically restricted species can show local abun­ northern Italy and reach a maximum of 41 % in Sicily. The percentages dances, ds' Dasylobus cavannae in the central and southern Apennines, of widespread species are low everywhere. Trogu/us martensi in wet and low alritude habitats of north-eastern Italy, Considering absolute numbers rather than percentages, the strong or Megabunus bergomas in the Alps near ; other endemic decrease in diversity running from north to the Islands dilutes the evi­ species, on the contrary, are undoubtedly rare (e,g., Mitostoma ar­ dence of the increase in Mediterranean range patterns. obicuml. A great local abundance can be shown by species with small 5)8 CLAUDlO CHEMIN] range but forming, with closely related and vicariant species, a group having largcr distribution and wider ecological tolcrance: this is the case of Astrobunus helleri, very abundant in its east-Alpine range, with the vicariant lhtrobunus kochi, which occurs from the Maritime Alps to southern Apennines.

ACKNOWLEOGEMENTS

I am gratcful to Pro£. Alessandro Minelli for helpful comments and suggestions on the manuscript. I thank Dr. PaoIo Bonavita for technical assi,tance and comments.

REFERENCES

CHEMINI C. 1995. Amchnidl1: Scorpiones. Palpigradi, Solifugae. Opiliones. In: MINELLI A., RUfFO S. & LA PaSTA S. (Eds.l, Checklist delle specie della fauna ttahana. 21. Calderini. Bologna. HAYDON D.T., CROTHER a.I. & PIANKA E.R.. 1994. New directions in biogoo~raphy? Trend, Eml Evol. 9 OOi: 403-406 I--l.ENGEVELD R., 1990. Dynamic biogeography. Cambridge University Press. xiv + 249 pp. LA GRECA M.. 1964. Le caregorie corologiche degli dementi faunisrici iraIiani. Mf'm. Soc. entom. ildl., 4;: 147-165. Mi\RCELLlNO I.. 1986. OpiJioni deU'Appcnnmo meridionale (Arachnida, Opilionesl. Biogeu· gf<'ph,u, 10: 361-377. MARTENS J., 1978. Spinnen'iere, Arachnida: Weberknechte. Opiliones. Die Tierwe1t DeulSchlands, vol. 64. G. Fisehcr, Jena, 464 pp. Rrf:KLEFS R.E.. 1987. Community diversity: relative role of local and regional processes. Science. 235: 167·171.

TEDESCHI M. &. SClAKY R., 1994. Three new Italian species of the genus Holoscotolemon (Arachnida Opiliones Erebomastridael. Boil. Mu,. ciu. 5/. na/. Verona. 18: 1-10. VIGNA TAGLIANTI A., AUDlSIO P.A. et aI., 1992. Riflessioni d.i gruppo sui corotipi fonda­ mentali della fawla W-paleartica ed in parricolare italiana. Biogeographia, 14: 159-179.

Author's address: CLAUDIO CHEMINI - Centra di Eoologia Alpina . Vime Monte Bondone· 38040 Sardagna tTrenrol, Italy.

FlI1ito di stampare if JI ottobre 1996.