Journal of Biogeography (J. Biogeogr.) (2005) 32, 813–831

ORIGINAL The distribution of ground ARTICLE (Araneae, Gnaphosidae) along the altitudinal gradient of Crete, Greece: species richness, activity and altitudinal range M. Chatzaki1*, P. Lymberakis1, G. Markakis2 and M. Mylonas1,3

1Natural History Museum of Crete, University ABSTRACT of Crete, Irakleio, 2Technological Education Aim To study the altitudinal variation of ground spiders (Araneae, Gnaphosidae) Institute of Crete, Irakleio and 3Department of Biology, University of Crete, Irakleio, Greece of Crete, Greece, as far as species composition, species richness, activity and range of distribution are concerned. Location Altitudinal zones (0–2400 m) along the three main mountain massifs of the island of Crete. Methods Thirty-three sampling sites were located from 0 to 2400 m a.s.l. on Crete, and sampled using pitfall traps. Material from the high-activity period of Gnapho- sidae (mid-spring to mid-autumn) was analysed. Sampling sites were divided into five altitudinal zones of 500 m each. Statistical analysis involved univariate statistics (anova) and multivariate statistics, such as multidimensional scaling (MDS) and cluster analysis (UPGMA) using binomial data of species presence or absence. Results Species richness declines with altitude and follows a hump-shaped pattern. The activity pattern of the family, as a whole, is not correlated with altitude and is highly species-specific. In the highest zone, both species richness and activity decline dramatically. The altitudinal range of species distribution increases with altitude. On the Cretan summits live highly tolerant lowland species and isolated residents of the high mountains of Crete. Two different patterns of community structure are recorded. Main conclusions Communities of Gnaphosidae on Crete present two distinct structures following the altitudinal gradient, these being separated by a transitional zone between 1600 and 2000 m. This study supports previous results which show a hump-shaped decline in species richness of Gnaphosidae along altitudinal gradients, leading to a peak at 400–700 m, where an optimum of environmental factors exists. This makes this zone the meeting point of the often opportunistic lowland species with the older and most permanent residents of the island. Rapoport’s rule on the positive correlation of the altitudinal range of species distributions with altitude is also supported. The high activity recorded for the species that persist on the high mountains of Crete is indicative of a tolerant arachnofauna, and is considered to result from relaxation of competitive interactions with other species. This is related to a reduction in species numbers, shortening of the activity period on high mountains and the unique presence of high mountain species that thrive only there. As shown in our study, strategies to cope with altitude are species-specific. Therefore, there cannot exist one single model to describe how react to *Correspondence: M. Chatzaki, Natural the change in altitude, even under the same environmental conditions. History Museum of Crete, University of Keywords Crete, PO Box 2208, 71409 Irakleio, Crete, Greece. Activity, altitudinal gradient, altitudinal range, Crete, Gnaphosidae, ground E-mail: [email protected] spiders, Mediterranean, mountain ecology, pitfall traps, species richness.

ª 2005 Blackwell Publishing Ltd www.blackwellpublishing.com/jbi doi:10.1111/j.1365-2699.2004.01189.x 813 M. Chatzaki et al.

intermediate elevation (Bosmans et al., 1986; McCoy, 1990; INTRODUCTION Colwell & Hurtt, 1994; Rahbek, 1997; Fleishman et al., 1998; The effect of altitude on biodiversity has been a topic of great Sa´nchez-Cordero, 2001; Grytnes & Vetaas, 2002; Sanders, interest for many earlier and contemporary biogeographers. 2002) (for a detailed review see also Lomolino, 2001 and During the nineteenth century latitudinal and elevational Sanders, 2002). In insects, both patterns have been observed gradients in diversity were considered direct responses to (Sanders, 2002 and references therein). According to McCoy climatic changes and energy interactions in the environment (1990), the latter pattern is more pronounced in predomin- (see historical review in Lomolino, 2001). These were later antly, or totally, herbivorous insects, such as Coleoptera, interpreted as the species-energy theory by Wright (1983). Homoptera and Hemiptera. Recent researchers connected mountain ecology with the Apart from species richness, changes that occur in the species–area relationship of island biogeography (MacArthur, abundance of a species along altitudinal gradients are often 1972), because of the similar conditions prevailing for both similar to changes along its geographical range (Whittaker, types of ecosystems (small area, isolation, restricted spatial 1952; Hagvar, 1976; Claridge & Singhrao, 1978; Randall, 1982). heterogeneity). The negative effect of latitude on species Abundance appears to be higher at the centre of a species range richness and latitudinal range, or Rapoport’s rule (Stevens, and lower near the edges (Brown, 1984; Brussard, 1984; Brown 1989) has also been correlated with the same phenomenon et al., 1996). The pattern of abundance of a species along along altitudinal gradients (Stevens, 1992; Brown et al., 1996). altitudinal gradients must be highly species-specific, as it is The latter is explained as a result of the wider ecological related to many factors such as responses to climate changes, to tolerances of organisms at higher elevations, a crucial charac- food quantity and quality, to natural pressure of enemies and teristic which they have to possess in order to withstand the to interspecific competition (see Lawton et al., 1987 for wider climatic fluctuations to which they are exposed. Lawton detailed citations). et al. (1987) ascribed the effect of elevation on species richness Evidence for the value of Rapoport’s rule along elevation to the following reasons: (1) reduction in productivity with gradients emerges from surveys of plants, mammals, reptiles elevation; (2) reduction in the total area; (3) reduction in and insects (Stevens, 1992). More detailed surveys verify this resource diversity; and (4) harshness and unpredictability of rule for butterflies (Fleishman et al., 1998), grasshoppers the conditions prevailing at higher elevations. (Claridge & Singhrao, 1978), ants (Sanders, 2002) and partially Two more phenomena have been related to the negative isopods (Sfenthourakis, 1992). According to Brown et al. effect of altitude on species richness, the ‘mid-domain effect’ (1996), Rapoport’s rule is closely related to general factors (Colwell & Lees, 2000) or ‘ecotone effect’ (Lomolino, 2001), which limit the range of distributions along geographical or i.e. the peak in species richness at mid elevations, due to the ecological gradients, i.e. increasing physical stress in one increasing overlap of species ranges towards the centre of a direction, and increasing numbers and impacts of biological domain or minor peaks at transitions between elevational enemies in the other. Therefore, it is a very dynamic, species- communities, and the ‘rescue effect’ (Brown & Kodric-Brown, specific phenomenon, partly depending on global climatic 1977), i.e. the reduced likelihood of a population at higher changes and on human activities. elevations to be rescued by individuals dispersing from other Concerning spiders, not many detailed studies have been zones when compared with populations at lower elevations. carried out focusing on the relationship between species Stevens (1992) proposed the Rapoport-rescue hypothesis, richness and altitude or other of the above questions on a which is the extension of the previous idea to species level, species level. Maurer & Ha¨nggi (1991) presented the altitudinal suggesting that species richness is inflated in lower latitudes/ variation of species in Switzerland, reporting a more or altitudes by the emigration of high-altitude species at the less linear decline and an abrupt decrease in the number of margins of their ranges due to wider tolerance, while taxa from species above the timberline (only 7% of the total number of lower elevations cannot expand their upper limit of elevational species of the country occur above 2300 m). Although very few range. In total, this would mean that extinction rates of species species occupy the whole altitudinal range of the Swiss Alps increase with elevation and so does isolation, in contrast to (21 species), about half of the total arachnofauna have wide immigration rates, which decrease with elevation (Stevens, altitudinal range, their distribution extending from the valleys 1992; Lomolino, 2001). to the timberline. Referring to the invertebrate diversity Although the negative effect of altitude on diversity is (including spiders) at high altitudes of the Central Alps, broadly documented (Lawton et al., 1987; McCoy, 1990; Meyer & Thaler (1995) reported a gradual decline of species Stevens, 1992; Brown et al., 1996; Lomolino, 2001; Sanders, within the main life zones from 1800 to 3500 m and a stepwise 2002), the pattern of diversity decline is still controversial. decline of species at the main borders. Bosmans et al. (1986) One group of scientists favours a monotonic decrease in studied the spider communities along an altitudinal gradient in species richness with increasing elevation (Claridge & the French and Spanish Pyre´ne´es (700–2475 m), concentrating Singhrao, 1978; Lawton et al., 1987; Wolda, 1987; Fernandes mainly on the community structure and the zoogeographical & Price, 1988; Sfenthourakis, 1992; Stevens, 1992 and patterns formed by the geographical distributions of the references therein) and another group favours a hump-shaped spider species. Although not analysed, their results favour the pattern, where the peak of species richness occurs at an hump-shaped pattern of altitudinal distribution of the species

814 Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd Altitudinal distribution of ground spiders

(at the zone 1100–1500 m). An ecological survey of ground When referring to the main characteristics of the island, spiders along altitudinal gradients in Norway (Otto & Bonnefont (1972) reports the decrease in altitude from west to Svensson, 1982) demonstrated the same pattern of species east, and the great fragmentation and asymmetry between decline from 0 to 800 m altitude, a positive correlation of the the north and south coast of Crete, the former being more number of eurychronous species and of the range of altitudinal hospitable than the latter. The southern slopes of the main distribution, indicating the persistence of some widely distri- mountain massifs of Crete are much steeper, with very steep buted and easily dispersed species at high elevations. The slopes close to the coasts forming lots of gorges. abundance of spiders declines along altitudinal gradients of south Appalachian Mountains of North Carolina, Virginia and Climate Maryland (McCoy, 1990) with maximum abundance recorded at low (but not the lowest) elevations. Crete has a typical Mediterranean climate with 5–7 months of This study examined the distributional patterns (species arid, hot and dry summers, alternating with shorter periods of richness, activity, altitudinal range and community struc- rainy, mild winters. There are not sufficient meteorological ture) of the dominant family of ground spiders of Crete, data, especially for the high mountains. However, there is a Gnaphosidae, along the altitudinal gradient (0–2400 m) remarkable gradient of temperature, precipitation, winds and formed by three main mountain massifs, namely Lefka Ori, humidity across the main axes of the island, north to south, Psiloreitis and Dikti. It would seem that these ecological west to east and from the coasts inland and upwards. features are closely related to the history of the island and the South, east and inland lowlands are warmer than the rest of way of formation of its fauna. Therefore, associations the regions, both in summer and in winter, except for inland concerning the origin of the species occurring at different winters that are cooler than the coastal ones (Rackham & altitudinal zones and the possible ways they reached these Moody, 1996). Mean annual temperatures are 2 C lower in zones are also given. Patterns of the above-mentioned the south than in the north of Crete (Pennas, 1977) and they ecological factors are first analysed on a regional–altitudinal fall 6 C per 1000 m altitude (Grove et al., 1991). The range of base using altitude as a continuous parameter and then by temperatures is much narrower near the coast than in the dividing sites into five altitudinal zones of 500 m each. Details mountains, due to the more maritime character of the former of special features of each mountain massif are analysed (Strid, 1995). separately. Although there are no records for precipitation above 900 m, Rackham & Moody (1996) estimate that at the top of Lefka Ori the annual precipitation must be as high as MATERIALS AND METHODS 2000 mm. In southern Lefka Ori, snow fall above 1400 m a.s.l. can be several metres, but the resulting water disappears into Study area the porous crystalline limestone immediately after the snow melts in May. This harsh landscape forms the ‘high desert’, a Geomorphology term coined by Rackham & Moody (1996) to describe a unique Crete is the largest island of the south Aegean island arc and is environment that does not exist in the other two mountain situated at its centre (3450¢–3540¢ N latitude, 2330¢– massifs. 2620¢ E longitude). It is the fifth largest island of the Mediterranean after Sicily, Sardinia, Cyprus and Corsica, its Geological history total surface covering 8.261 km2. Because of the intense tectonic dynamics occurring in this area, Crete presents a The history of the south Aegean island arc dates back to the great geomorphological variation, being a ‘miniature contin- middle Miocene (15–11 Ma), when intense fragmentation and ent’ (Rackham & Moody, 1996). Within such a small surface, a the first subductions of the Hellenic arc started to take place, great variety of habitats and climatic factors are present, transforming the southern parts of ‘Aegaiida’ (the united land ranging from the insular character of the coasts to a fully mass comprising what is today the Hellenic peninsula and the continental character as one goes inland and approaches the Aegean Sea) into separated island forms (Dermitzakis & high altitudes of its mountains. Papanikolaou, 1981; Le Pichon & Angelier, 1981). More recent The main characteristic of the island geomorphology is the evaluations of the geodynamic evolution of the Aegean area high percentage of mountainous regions, 39% of its surface support the idea that such events that contributed to the being above 400 m, 12.5% above 800 m and 1.6% above separation of Crete initiated at least 26 Ma (Meulenkamp 1600 m. Three main mountain massifs are situated along et al., 1988). Although there is not full agreement about the Crete: Lefka Ori in the western part, Psiloreitis in the central periods and duration of land connections of Crete with part and Lasithiotika Ori (Dikti and Thrypti) in the eastern neighbouring continental areas, it is certain that Crete has been part. Although the highest summit is found in Psiloreitis fully isolated since 5 Ma. (2.456 m), the largest mountainous range is found in Lefka Cretan mountains are quite new in geological time. Until Ori: its highest summit is 2.453 m and there are another the early Pliocene (5 Ma) Crete was composed of a mosaic 56 summits over 2000 m. of landmasses that did not exceed the altitude of 500 m

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(Meulenkamp et al., 1988). The altitudinal zone above 1500 m brutia (P) is the dominant species up to 1200 m. This is the was formed as a result of pronounced uplifts that took place commonest forest formation of Crete, being found from sea after the Pleistocene (1.5 Ma) (Meulenkamp et al., 1994). level to such altitudes. The rest of the woodland types on Crete are very scarce: the Quercus coccifera forest on the southern slopes of Psiloreitis (area of Rouvas, psi1000a) and the Vegetation Cupressus sempervirens–Quercus coccifera–Acer sempervirens Phrygana is the most widespread formation on the island, formations on the southern slopes of Lefka Ori (area of although irregularly distributed and showing a specific altitu- Anopoli, lo1200) are among the most characteristic ones. Clear dinal zonation and ecological differentiations (Strid, 1995). altitudinal zonation, such as evergreen broadleaves–deciduous Phrygana are found from sea level to the highest summits, but forests–conifer trees, does not exist on Crete (Rackham & with the ratio of annual : perennial plant species decreasing Moody, 1996). from low to high altitudes. Lowland and middle altitude phrygana are composed of thorny aromatic shrubs such as: Methodology and statistical analysis Sarcopoterium spinosum, Coridothymus capitatus, Phlomis cre- tica, P. lanata, P. fruticosa, Cistus spp., Genista acanthoclada, A total of 33 sampling sites were selected along the island of Calicotome villosa, Euphorbia spp., Balota spp. and others. At Crete (Fig. 1) starting from sea level and reaching the highest higher altitudes other species (chamephytes) such as Berberis elevations of 2400 m. Sites include the most characteristic cretica, Rhamnus saxatilis, Prunus prostrata, Satureja spinosa habitat types of the island, i.e. phrygana, maquis, areas close to and Astragalus angustifolius dominate. Beyond the timberline, wetlands, pine, kermes oak and cypress forests, and sub-alpine only scarce vegetation composed of small cushion-like shrubs shrublands (see Appendix 1). Following the relative represen- exists. In the present study, habitats of this type are separated tation of these habitat types on Crete, the majority of sites are into phrygana near the coast (CP), inland phrygana (IP) and shrublands that are represented by different species associa- sub-alpine shrubs (SS), following the altitudinal gradient tions, depending on the altitudinal zone. No urban areas were (Appendix 1). sampled; therefore, habitat diversity of the lowlands is not fully Maquis (M) on Crete are often intermixed with phrygana, the represented in this study. limits between the two being vague (Rackham & Moody, 1996). In all sites material was collected by pitfall traps, using This is mainly due to overgrazing of the region. Apart from the ethylene glycol as a preservative. Pitfalls were set and changed above species, other typical maquis species are Ceratonia siliqua, at 2-month intervals except for the sites at Lefka Ori, where P. terebinthus, shrub-like Quercus coccifera, Pistacia lentiscus, they were changed each month (see Appendix 1). Collection Arbutus unedo, Juniperus phoenicea, J. oxycedrus, Erica arborea of material covered the period of high activity of the family and others usually reaching 1–2 m height, or even more. These Gnaphosidae, i.e. from mid-spring to mid-autumn. More formations may reach an altitude of c. 600 m. than two samples were collected at each site. Spiders of this The upper limits of forest growth reach altitudes from family were identified to species level and only mature 1600 m (southern slopes) to 1800 m (northern slopes). Pinus individuals were counted. Because pitfall traps register

Figure 1 Map of sampling sites on Crete.

816 Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd Altitudinal distribution of ground spiders

Table 1 Altitudinal zones on Crete: altitudinal limits, code species do not occur in the first altitudinal zone (Drassodes names, number of sites and number of species sampled to each oreinos, Gnaphosa bithynica, Haplodrassus minor, H. signifer, one of them Micaria dives, Poecilochroa senilis1, Scotophaeus scutulatus, Synaphosus palearcticus and Drassyllus sp.). Nine species can Altitudinal Code Number Number zone (m) name of sites of species be characterized as exclusively lowland species, occurring only up to 500 m (Berinda ensigera, Berlandina plumalis, 0–499 ZER 14 44 Leptodrassus hadjissaranti, L. manolisi, Micaria pygmaea, 500–999 LOW 6 39 Nomisia sp., Scotophaeus peninsularis, lyonneti, 1000–1499 MID 6 28 Z. nilicola). 1500–1999 TOP 4 19 Above 2000 m there are five species in total. Drassodes 2000–2400 PEAK 3 5 oreinos, a recently described species (Chatzaki et al., 2002b), and G. bithynica, being present only at Lefka Ori and Psiloreitis (Chatzaki et al., 2002a), are recorded on the Cretan mountains activity patterns of and are only partly affected by above 1200 m and 1600 m respectively. The remaining species the population size of taxa (Maelfait & Baert, 1975), – Z. creticus, Z. subterraneus and Z. labilis – occur at all quantitative data were not used for further statistical analysis. elevational zones of Crete, the first being Cretan endemic, the The effect of seasonality on activity patterns is the subject of second Palearctic and the third presenting unclear taxonomical another paper (M. Chatzaki et al., unpubl. data), therefore in status (Chatzaki et al., 2003). Among these species, G. bithynica the present study it was reduced by using mean values of and Z. creticus were not present at Dikti mountain. samples at each site. It is for this reason that winter material Apart from the above-mentioned differences, some species was not included in the analysis so that samples within the present deviations concerning the upper limit of their high-activity period of the family could be considered as distributions at the three main mountain massifs. For instance, equal sampling units as regards seasonality. In order to Pterotricha lentiginosa, Callilepis cretica, Zelotes caucasius and balance sampling effort for all sites, the number of individ- Z. subterraneus reach 1950 m in Psiloreitis and 1750 m in uals per sample was transformed to the number of individ- Dikti, but do not exceed 800 or 1600 m in Lefka Ori. uals per 100 trap days and the mean values of samples per site were used for each species (Appendix 2). The same Species richness transformation was used for the whole family, by summing the above mean values of all species at each site. Species collector curves were created using all sites together Sites were divided into five altitudinal zones of 500 m each, (Fig. 2) and each altitudinal zone separately (Fig. 3). The last starting from sea level. Table 1 shows the number of sites two zones were combined in one graph because the number of included in each of the above zones as well as the species sites at each zone was very limited. At the zones ZER and MID richness of each zone. Species collector curves were created with as well as when all sites are analysed together, the curves are EstimateS6b1a (version 6.5.6 for WindowsTM, 1985–2000). asymptotic and sampling may therefore be considered as Basic statistical tests were conducted with Statistica 6.0 (Statsoft saturated. At the zones LOW and TOP-PEAK a plateau of Inc., 1984–2001) and SPSS8 (SPSS Inc., 1989–1997, Standard species numbers is roughly reached. In all cases there is a version). Two-way anova was first used to test for the decrease in standard deviation of the number of species as significance of differences in species richness and activity the number of sites increases (SDALL SITES ¼ 4.97–0.48; among sites in relation to the mountain massif and the SDZER ¼ 5.22–1.02; SDLOW ¼ 7.86–1.61; SDMID ¼ 5.82– altitudinal zone they belong. Multidimensional scaling (MDS) 1.15; SDTOP-PEAK ¼ 4.93–2.12). (James & McCulloch, 1990) conducted with PRIMER5.2.2 Species richness at sites along the altitudinal gradient is (Primer-E Ltd, 2001) was used in order to visualize the presented in Fig. 4 and shows a hump-shaped decline with similarities among sites of the investigation based on the species altitude, which may be described by a quadratic equation. recorded on them. The ordination was based on the Bray–Curtis Pearson’s correlation indicates a significant negative correla- distance on presence-absence data. Cluster analysis (UPGMA), tion between the two variables (R ¼ )0.738, P < 0.001). The based on Jaccard’s coefficient of similarity (Krebs, 1998), was highest numbers of species are recorded at the sites between performed in order to detect in more detail the stability of 400 and 700 m. Species numbers decline continuously after patterns along the mountains of Crete and the ecological factors 1000 m altitude, and they fall abruptly after 2000 m to three or that influence faunal similarities among sites. four species per site. Species richness of Gnaphosidae was tested against the five altitudinal zones and the three mountain massifs (anova, RESULTS Table 3). Differences are significant among altitudinal zones, Species composition 1 Poecilochroa senilis is nevertheless recorded from other lowland sites Table 2 shows the species recorded at each altitudinal zone. In not included in this study. Similarly S. scutulatus is recorded from total, 54 species of ground spiders were recognized. Nine Gavdos island, south of Crete.

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Table 2 Species composition of the family Gnaphosidae for 60 each altitudinal zone on Crete 50 Species name ZER LOW MID TOP PEAK 40 Anagraphis pallens ++ + + 30 Berinda amabilis ++

Berinda ensigera + 20

Berlandina plumalis + Number of species Callilepis cretica ++ + + 10 Camillina metellus ++ + 0 Cesonia aspida ++ + 0 5 10 15 20 25 30 35 Cryptodrassus creticus ++ Number of sites Drassodes lapidosus ++ + Drassodes lutescens ++ + + Figure 2 Species collector curve. Data points represent average Drassodes oreinos +++ species numbers (from 100 replicates) computed for the given Drassodes serratichelis +++ number of sites. Drassyllus praeficus ++ + + Drassyllus pumiloides ++ + + Drassyllus sp. + but not among mountain massifs. Species numbers at the sites Gnaphosa bithynica ++ of each mountain massif are shown in Fig. 5. A quadratic Haplodrassus creticus ++ + + equation may describe the species richness decline in Haplodrassus dalmatensis ++ + + Psiloreitis. In the other two mountains, regression cannot Haplodrassus minor + be described by a similar equation, despite the significantly Haplodrassus signifer + negative correlation between number of species and altitude. Leptodrassus albidus ++ Leptodrassus femineus ++ Leptodrassus hadjissaranti + Activity Leptodrassus manolisi + Leptodrassus pupa ++ Mean activity of the family as a whole is not correlated with Micaria albovittata ++ + altitude (Pearson’s correlation R ¼ )0.083, P ¼ 0.323, Fig. 6). Micaria coarctata ++ + + However, when the sum of means of all species is divided by Micaria dives ++ the number of species present at each site, Pearson’s correla- Micaria pygmaea + tion becomes significant (R ¼ 0.645, P < 0.001). Contrary to Nomisia excerpta ++ + + species richness, mean activity per species is positively Nomisia ripariensis ++ correlated with altitude (Fig. 7). Nomisia sp. + There are no significant differences in family activity among Poecilochroa senilis + altitudinal zones or among mountain massifs (Table 3). The Pterotricha lentiginosa ++ + + Scotophaeus peninsularis + interaction of the two factors is not significant. Therefore sites Scotophaeus scutulatus + of the study area can be treated as a uniform geographical Setaphis carmeli ++ area. Synaphosus palearcticus + About half of the species (46%) present their maximum Synaphosus trichopus ++ activity [or potential midpoint, sensu Grytnes & Vetaas (2002)] Trachyzelotes adriaticus +++ at the first zone, although many of them have a wide Trachyzelotes barbatus ++ altitudinal range (see next paragraph, and Fig. 8). Testing the Trachyzelotes lyonneti + 25 most abundant species separately, the mean activity of most Trachyzelotes malkini ++ + of them is not significantly different at the five zones (Table 4). Zelotes caucasius ++ + + Four species show significant differences in their mean activity Zelotes creticus ++ + + + (i.e. A. pallens, D. oreinos, P. lentiginosa and Z. tenuis). Two of Zelotes daidalus ++ Zelotes cf. ilotarum ++ + them present their maxima at higher altitudes above 1000 m Zelotes labilis ++ + + + and are quantitatively more concentrated at these elevations Zelotes minous ++ than the rest of the species. Zelotes nilicola + Zelotes scrutatus ++ + + Range of distribution Zelotes solstitialis ++ Zelotes subterraneus ++ + + + Because there is no significant effect of the regional variation Zelotes tenuis ++ + on either species richness or activity (Table 3), analysis on the range of altitudinal distribution was conducted without taking into account regional subdivision.

818 Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd Altitudinal distribution of ground spiders

ZER LOW 50 35 45 30 40 35 25 30 20 25 20 15 15 10 10

Number of species Number of species 5 5 0 0 0 2 4 6 8 10121416 0246810 Number of sites Number of sites

MID TOP-PEAK 35 35 30 30 25 25 Figure 3 Species collector curve for each 20 20 altitudinal zone separately. Data points rep- 15 15 10 10 Number of species resent average species numbers (from 100 Number of species 5 5 0 0 replicates) computed for the given number of 0246810 0246810 sites. Number of sites Number of sites

25 Table 3 Two-way anova test for the comparison of mean values 2 y = –5E-06x + 0.0044x + 17.601 2 of species richness and activity of Gnaphosidae between sites R = 0.7194 20 belonging to different altitudinal zones and different mountain massifs (* ¼ significant at a ¼ 0.05)

15 Species richness Activity

10

Number of spp FP-value FP-value

5 Region (d.f. ¼ 2) 0.98 0.393 1.712 0.207 Altitude (d.f. ¼ 4) 4.38 0.017* 0.656 0.589

0 Interaction (region · 0.507 0.796 0.79 0.589 0 500 1000 1500 2000 2500 altitude, d.f. ¼ 6) Altitude (m)

Figure 4 Correlation graph of the number of Gnaphosidae spe- cies at the sites along the altitudinal gradient of Cretan mountains. positively correlated with altitude following a statistically ) The Pearson’s correlation coefficient is significant (R ¼ 0.738, significant linear equation (F1,54 ¼ 15.1, P < 0.001). P < 0.001). The quadratic equation is also statistically significant 2 (R ¼ 0.629, F2,28 ¼ 23.72, P < 0.001). Multivariate analyses In total, species that occur only at low (up to 500 m, 17%) Multidimensional scaling or mid-elevations (up to 1000 m, 30%) represent about half of the total fauna of this family (Fig. 8)2. The following two zones Ordination of sites using Bray–Curtis distance on binomial are the elevational limit for nine and 153 species (17% and 28% data is seen in Fig. 10 (stress ¼ 0.13). Sites in black circles of the total number of species respectively). Of the five species belong to the highest altitudinal zone and are clearly which reach the last zone, three have a wide altitudinal range separated from the rest of sites. Apparently this ordination (from sea level to 2400 m) and two present a narrower range. is mainly caused by the two mountain species D. oreinos and In total, 14 species were found at a single zone and another G. bithynica, which appear only at the sites of higher 15 were found at two (26–28% of the total number of species elevations and by the absence of most of the rest of species for each case). The remaining species were found in more than (see Appendix 2). Sites belonging to the other zones are two altitudinal zones, showing a greater range of altitudinal arranged in clusters of close vicinity, one after the other, tolerance. As seen in Fig. 9, altitudinal range of species is indicating a gradual replacement of species along the altitudinal gradient. 2 In this figure, discontinuities of the altitudinal range of distribu- tion (see Table 2) were not taken into account. Cluster analysis 3 In the zone 1500–1999 m, there is a sampling gap between 1650 For the calculation of similarity within and between sites and 1950 m, so that the limits of the altitudinal range of the species of each mountain massif, Jaccard’s index was used. In the recorded here are not necessarily the highest limit for this zone. However, four of the above species (H. dalmatensis, P. lentiginosa, dendrograms created by cluster analysis (UPGMA) (Fig. 11) Z. caucasius and M. coarctata) were found at 1800 m as well (data not five main clusters are observed at the level of 0.46–0.49 included in this analysis). similarity:

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Lefka Ori 25 24 22 20 20 18 16 15 14 12

10 10 8 Number of species 6 Individuals/100 trapdays 4 5 2 0 0 0 250 500 750 1000 1250 1500 1750 2000 2250 2500 0 500 1000 1500 2000 2500 Altitude (m) Altitude (m)

Psiloreitis 24 Figure 6 Sum of mean activity of Gnaphosidae species (total 22 number of individuals per 100 trap days) along the altitudinal 20 gradient of Cretan mountains. Pearson’s correlation coefficient is 18 ) 16 not significant (R ¼ 0.083, P ¼ 0.323). 14 12 10 3 8 Number of species 6 2.5 4

2 2 0 0 250 500 750 1000 1250 1500 1750 2000 2250 2500 1.5 Altitude (m)

1

Dikti Individuals/100 trapdays 24 22 0.5 20 18 0 0 500 1000 1500 2000 2500 16 Altitude (m) 14 12 10 Figure 7 Mean activity of Gnaphosidae species (total number of 8 individuals per 100 trap days divided by the number of species at Number of species 6 each site) along the altitudinal gradient of Cretan mountains. 4 2 Pearson’s correlation coefficient is significant (R ¼ 0.645, 0 P < 0.001). 0 250 500 750 1000 1250 1500 1750 2000

Altitude (m) 2500

Figure 5 Species richness of Gnaphosidae at the sites of the three Maximum activity main mountain massifs of Crete. Regression analysis shows that a 2000 quadratic equation is statistically significant only for the sites of 2 Psiloreitis (R ¼ 0.812, F2,10 ¼ 21.62, P < 0.001). Pearson’s cor- relation coefficient at all three mountains is statistically significant 1500

(RLO ¼ )0.637, P ¼ 0.033; RPSI ¼ )0.866, P < 0.001; RDIKT ¼ )0.642, P ¼ 0.031). 1000 Altitudinal zone (m)

500 (a) Most of the sites of the first (0–499 m or ZER) and some of the sites of the second zone (500–999 m or LOW), belonging 0 0 5 10 15 20 25 30 35 40 45 50 55 to the mountains Psiloreitis and Dikti. Species rank (b) Sites of the third (1000–1499 m or MID) and most of the sites of the second zone, belonging to the same mountains. Figure 8 Altitudinal range of Gnaphosidae species along the altitudinal gradient of Cretan mountains. This cluster also includes one site from Lefka Ori at 1200 m (lo1200). (c) Sites lo50, psi50 and psi1200 with no obvious regional or It is noteworthy that sites of Lefka Ori usually remain altitudinal association. outside the main clusters (for instance lo800, lo20, lo30). (d) Sites of the fourth zone (1500–1999 m or TOP). Although an analysis on the effect of habitat type on the sites (e) Sites of the fifth zone (2000–2400 m or PEAK). ordination could not be performed, because it is correlated

820 Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd Altitudinal distribution of ground spiders

Table 4 Mean activity per zone of the 25 most abundant gradient on Crete, in addition to the historical events that Gnaphosidae species occurring at least along three altitudinal zones. contributed to the formation of this fauna, the insular P-values (after Bonferroni correction for multiple comparison) of character of the study area, and the effect of human activities anova the test (d.f. ¼ 4, 28; * ¼ significant at a ¼ 0.05) on the island. Arguments for this effect, on each of the main Species ZER LOW MID TOP PEAK P-value issues of this study, are given below.

A. pallens 0.286 0.100 0.027 0.105 0 0.000* Community structure C. creticus 0.151 0.515 0.658 1.395 0 0.120 C. metellus 0.195 0.068 0.040 0 0 5.990 Along the altitudinal gradient of Crete, two main patterns of C. cretica 0.082 0.038 0.034 0 0 7.300 community structure are evident: (1) that of the first zone, D. lapidosus 0.037 0.170 1.434 0 0 0.260 from sea level to 1500 m, where there are many species with D. lutescens 0.167 0.379 0.274 0.045 0 4.220 similar activity, thus forming a well balanced fauna, and (2) D. oreinos 0 0 0.257 1.528 2.672 0.000* that of the higher zone, above 1600 m, where the number of D. praeficus 0.318 1.121 2.613 0.533 0 0.300 D. pumiloides 0.050 0.123 0.100 0.027 0 3.040 species declines considerably and very few species dominate. In D. serratichelis 0.025 0 0.040 0.042 0 5.830 between these two zones, there is an intermediate transitional H. creticus 0.041 0.167 0.371 0.550 0 1.740 zone, which in a stricter sense, extends further up to 2000 m, H. dalmatensis 0.095 0.012 0.133 0.160 0 6.270 leaving the summits forming an extreme community. As M. albovittata 0.040 0.036 0.010 0 0 7.100 shown by MDS (Fig. 10) and by cluster analysis (Fig. 11) this M. coarctata 0.287 0.112 0.056 0.074 0 2.150 N. excerpta 0.753 0.509 0.553 0.275 0 4.800

P. lentiginosa 1.012 1.433 4.418 4.274 0 0.010* 3000 T. adriaticus 0.155 0 0.030 0.080 0 8.570 T. malkini 0.610 0.630 0.218 0 0 1.250 2500 Z. caucasius 1.363 0.780 0.687 1.761 0 3.440 2000 Z. creticus 0.476 0.095 0.477 0.143 0.266 7.750

Z. cf. ilotarum 0.081 0.216 0.358 0.000 0 5.920 1500 Z. labilis 0.678 0.528 0.206 0.630 1.181 2.550 Z. scrutatus 0.518 0.331 0.043 0.027 0 0.280 1000

Z. subterraneus 1.308 0.836 0.425 0.590 0.383 2.150 Altitudinal range(m) 500 Z. tenuis 1.427 1.596 0.193 0 0 0.030* y = 0.5353x + 618.22 2 R = 0.2186 0 0 500 1000 1500 2000 2500 Altitude(m) with altitude (Pearson’s correlation coefficient R ¼ 0.771, P < 0.001), differences in habitat type of these sites may Figure 9 Altitudinal range of Gnaphosidae species along the explain their isolation (see Appendix 1). altitudinal gradient of Cretan mountains. Pearson’s correlation coefficient is significant (R ¼ 0.472, P < 0.001). Linear regression is also significant (F ¼ 15.1, P < 0.001). DISCUSSION 1,54

Gnaphosidae is one of the most diverse and the most abundant of the spider families on the ground floor in Crete and in ZER Mediterranean habitats in general. This is documented in all LOW arachnological studies in the area (Christophe, 1974; Assi, 1986; Deltshev & Blagoev, 1994; Urones et al., 1995; Chatzaki, PEAK 1998; Chatzaki et al., 1998; Majadas & Urones, 2002; Lymb- TOP erakis, 2003). Most species show a large distribution area, and they are more diverse in temperate climates and arid ecosys- tems. In these environments most species have wide ecological preferences forming quite homogenous communities, not Dimension 2 strongly related to habitat types. MID On Crete, most Gnaphosidae are xerophilous or present high tolerance to high temperatures and aridity and very few have narrower, more specialized niche (Chatzaki, 2003). Dimension 1 Therefore, most species are widespread along the island, Figure 10 MDS ordination based on the Bray–Curtis dissimi- despite its high heterogeneity in most ecological features larity matrix of species presence–absence. Filled circles: sites at (i.e. climate, humidity, geology, vegetation, and especially zone ‘PEAK’, triangles: sites at zone ‘TOP’, open circles: sites at geomorphology). Similarly, the character of this family, as zone ‘MID’, filled squares: sites at zone ‘LOW’, X: sites at zone described above, greatly affects its response to the altitudinal ‘ZER’.

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dik0a dik50 psi200a psi200b a dik300 psi300a si300bp psi750 lo30 dik350 psi1000b dik700 psi650 dik800 psi1000a b psi1000c dik1200 dik1450 lo1200 psi1650 lo50 psi50 c psi1200 lo800 dik0b lo20 psi0 lo1650 dik1750 d psi1950 Figure 11 Cluster analysis (UPGMA) using lo2000 lo2400 e Jaccard’s index of similarity among the sites psi2200

0.17 0.31 0.46 0.60 0.75 of the three mountain massifs of Crete: Lefka Coefficient Ori (lo), Psiloreitis (psi) and Dikti (dik). latter zone is very isolated and does not relate to any of the as far as species composition is concerned. Accordingly, in a other zones which form a smooth gradient of ecological similar study at the high altitudes of the Central Alps, Meyer & variation following the altitudinal gradient. In this sense, the Thaler (1995) concluded that the decrease in species diversity Cretan summits represent ecological islands. at the timberline is more drastic in phytotrophic, than in From 1000 m upwards species are gradually filtered out zootrophic and saprotrophic orders. depending on their tolerance to high mountain harshness, and, The reason why Gnaphosidae present a comparatively in most cases, they are not replaced by others. The fauna of the homogenous character along the altitudinal gradient, which two higher zones is formed by: (1) lowland species that can changes abruptly only above 2000 m, lies in the high tolerance hardly reach these elevations, and hence they are found at the of its species towards aridity and temperature extremes. margins of their distributional range (mostly Mediterranean Among the spider families mentioned above, Gnaphosidae is species, i.e. A. pallens, M. coarctata, N. excerpta, T. adriaticus, the only one that presents peaks of activity within the dry Z. caucasius, Z. scrutatus), (2) species with wide elevational season (M. Chatzaki et al., unpubl. data), the other families range, but with potential midpoint at higher elevations, and emerging earlier in springtime (Chatzaki et al., 1998). At least hence better adapted to the Cretan mountains (mostly some species are able to modify their annual cycle on the high endemic or palearctic species, i.e. C. cretica, D. lapidosus, mountains of Crete, with peaks of activity during the more D. serratichelis, D. praeficus, H. creticus, H. dalmatensis, predictable months (August/September), so they can easily P. lentiginosa, Z. creticus, Z. labilis, Z. subterraneus), and (3) adapt to the harsh conditions of this environment (M. Chatzaki species that dominate exclusively at the higher altitudes of et al., unpubl. data). Because they live on the ground, the Crete (D. oreinos and G. bithynica). change of vegetation above the timberline does not affect them For Gnaphosidae, the timberline does not always play an directly, but only through the decline of food availability important role for the community structure, as the main resulting from the reduction of habitat diversity and com- variation of this fauna occurs at higher elevations than 1600– plexity. Moreover, some authors (Swan, 1963; Mani, 1968, 1700 m. In cluster analysis (Fig. 11), sites at these elevations 1990; Edwards, 1987) emphasize the importance of wind- are sometimes clustered with those at lower elevations blown organic material for the survival of organisms at zones (Psiloreitis) and sometimes with those at higher elevations above the tree line. They postulate that at these elevations the (Lefka Ori and Dikti), clearly indicating the transitional abundance of this aeolian material is much greater than the character of the fauna at this zone. Sites at this zone share primary productivity so as to constitute the main food some of the most tolerant species with the lowland sites, and resource for alpine organisms. Swan (1963) attributed the the high-altitude species with the summits. presence and feeding of spiders of the family Salticidae at For other spider families on Crete, which are probably more 6700 m in Mt Everest to air-blown flies and collembolans. dependent on the vegetation type of their habitat due to their Being generalist predators, Gnaphosidae, apparently, can way of life and foraging, such as Linyphiidae, Salticidae and survive even if food quality changes, provided it is enough to Theridiidae, there is a better defined species replacement above support their survival. 1600 m as was demonstrated by Lymberakis (2003) in a study Cluster analysis shows that the main factor inducing faunal at Lefka Ori. At the same mountain, the effect of the timberline similarity within mountain sites is the close vicinity and is also proved for other taxa, such as isopods (Lymberakis geographical orientation of the sites. However, the overwhelm- et al., 2004), in which it separates two almost distinct faunas, ing factor which induces similarity is similar elevation rather

822 Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd Altitudinal distribution of ground spiders than close geographical location (Fig. 11). Despite their reduction, as, at least for some taxa (such as land snails), they statistical insignificance, minor differences in both, patterns may also introduce new species in a region (Mylonas, 1984). It of species richness decline (Fig. 5) and species composition, should be noted that in the present study, no habitats close to are probably related to more severe climatic conditions and the urban regions or to cultivations were analysed. The study of wildness of the landscape of Lefka Ori, leading to an earlier these environments might change our results in favour of a species decline and absence of the less tolerant species. pattern similar to the linear decline of species along altitudinal gradients. As mentioned previously, primary productivity does not Species richness seem to affect very much generalist predators; therefore, the The hump-shaped decline of species richness is verified for ‘middle is good’ hypothesis may not be a very robust factor in Gnaphosidae along the Cretan mountains. The same pattern is the present study. repeated in the Cretan flora (Lymberakis, 2003), although the Concerning the mid-domain effect, one has to consider the abrupt decline of species richness occurs at lower elevations way of formation of the Cretan mountain fauna and the char- associated with the timberline. Similar results are presented in acteristics of the family under investigation. Crete is the only other studies on spiders (Otto & Svensson, 1982; Bosmans insular system where such research is being carried out, all et al., 1986; McCoy, 1990) or other animals (McCoy, 1990; previous studies mentioned above, referring to old continental Colwell & Hurtt, 1994; Rahbek, 1997; Fleishman et al., 1998; areas. Due to its isolation, a less balanced and perhaps Sa´nchez-Cordero, 2001; Grytnes & Vetaas, 2002; Sanders, impoverished fauna is to be expected (Gillespie & Roderick, 2002). Data on several taxa studied until now on Crete 2002), especially in mountains, where a truly alpine fauna is such as Coleoptera (Trichas, 1996), land snails (Vardinoyannis, actually missing and has never been established. The period of 1994), Isopoda (Lymberakis et al., 2004), or on mountains of high altitude existence on Crete is very short for enhancing the continental Greece (Sfenthourakis, 1992) are not very helpful speciation of a great number of species, confined only to them. in revealing the pattern of species richness decline, either The exclusively high mountain species of Crete (i.e. Gnaphosa because the altitudinal gradient of sites starts from mid bithynica and Drassodes oreinos), probably reflecting distribu- elevations (above 500–600 m) or because data are combined tional relicts, are very few for creating a second peak of into zones: in both cases it cannot be deduced whether there is richness at higher elevations. Therefore, there cannot exist a a linear decline of species richness or there is a peak hidden clear ecotone effect, as for instance in the Pyre´ne´es where a within the first altitudinal zone. peak is observed at 1100–1500 m (Bosmans et al., 1986), The results of our study cannot be due to a sampling because there are not two distinct faunas, meeting at an artefact, because the study was conducted from sea level to the intermediate zone to form a peak of species diversity. highest points of the island, so no sampling error may have At the elevations where the peak of species richness is occurred due to restricted elevational range of the study area observed on Crete, there is an optimum of environmental (see McCoy, 1990 and Lomolino, 2001). factors that involves: (1) the relaxation of intense urbanization Sanders (2002) attributed the peak in species richness of ants and agricultural activities when compared with the lowest in western US to the increase of the area at mid elevations and zone, (2) good climatic equilibrium between temperature and to the increased overlap of species distributions at the same humidity, and (3) greater habitat diversity and stability of elevations (or ‘mid-domain’ effect, Colwell & Lees, 2000). climate when compared with the higher zones. These features McCoy (1990) and Fleishman et al. (1998) interpreted their make this zone the meeting point of the often opportunistic results on different groups of invertebrates by putting forward lowland species of the coastline with the older and most two biological hypotheses: (1) the prediction that ‘ends are permanent residents of the island. bad’ because of climatic severity and predation at lower Wolda (1987) and McCoy (1990) argued that sampling elevations, climatic severity and resource scarcity at upper regimes play an important role in the outcome of such a elevations, and (2) the prediction that ‘middle is good’, survey, suggesting that continuous sampling over long relating species richness to elevation via primary productivity, periods of time may lead to a monotonic pattern of species which is considered to peak at mid elevations (Janzen, 1973; decline, while short-term sampling may lead to mid-eleva- Janzen et al., 1976). A final hypothesis that cannot be tional peaks. McCoy (1990) also admits that his own results overlooked is the extent of human disturbance at lower would favour the monotonic pattern if his sampling had been elevations, which may reduce species diversity (Wolda, 1987; for a longer duration. The argument here is that, in lower McCoy, 1990; Sanders, 2002). elevations, climatic conditions permit wider temporal vari- In the case of Cretan Gnaphosidae, species richness is ation of species activity. Therefore, short-term sampling is maximized at the zone 400–700 m. To them the lower end is not sufficient to accumulate a high percentage of species ‘bad’ because of both the higher danger of predation and of the diversity, and so underestimates it, leading to an ‘artificial’ human disturbance. Sites below this elevation are greatly hump-shaped pattern. Our results show that even with long- changed by intense urbanization, which seems to have caused a term sampling, hump-shaped patterns define species richness, gradual degradation of the environment even in ‘natural’ at least when not all habitat types (including urban regions) habitats. Human activities are not definitely related to species are investigated.

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land snails. According to Lawton et al. (1987) …‘there is no Activity general tendency for species to increase in abundance at higher Mean activity of Gnaphosidae is not correlated with altitude, elevations’, and this must be related to the many factors contrary to the activity per species which is positively contributing to this parameter, i.e. species’ physiological correlated with altitude. This, in combination with the decline tolerances on the one hand and intensity of climate’s of species richness along altitudinal gradients of Crete, harshness, latitude and other local factors on the other. indicates that species which are able to reach higher altitudes can become very active and thrive at these elevations, thus Altitudinal range counterbalancing the differences in species numbers among altitudinal zones. The same phenomenon was observed in the Our results fully conform to Rapoport’s rule. Most of the spiders of the Central Alps (Meyer & Thaler, 1995). Reasons species present occupy a great range of altitudinal distribution that explain this are the following: (76% more than 500 m and 46% more than 1000 m). This is 1. Shortening of the favoured period for reproduction with related both to wide ecological tolerances of the family analysed altitude produces a concentration of the activity period here and to historical reasons, which favoured the formation of towards the warmer and most predictable months, i.e. summer the high-altitude fauna mainly by tolerant lowland species, and early autumn. As our data correspond to this period, it is rather than by truly alpine members of the family. The latter evident that higher numbers of individuals will be recorded, would represent a less thermophilous arachnofauna and would although not throughout the year. probably have narrower altitudinal ranges. In the absence of 2. Reduction in species numbers with altitude releases these species, the pattern observed by members of the family on competitive interactions among the remaining, tolerant species Crete is mainly a reflection of climate change along the which then find the optimum conditions to augment their altitudinal gradient. Under these circumstances, Rapoport’s population size (Brown et al., 1996). rule remains as the only logical consequence. 3. Presence of newly appearing high-altitude species at the higher zones (1200–1600 m), where there are still many of the CONCLUSIONS lowland representatives, causes an inflation of the total activity of the family. Gnaphosidae present a rather unique character along the McCoy (1990) reports a negative correlation in the abun- altitudinal gradients of Crete. They consist of a great number dance of spiders with altitude. As he used sweep nets as of species with wide ecological tolerances, so that they occupy sampling method, he collected spiders from the vegetation wide altitudinal ranges much more than any other spider layer and not from the ground floor (hence not Gnaphosidae). family in the same area. Rapoport’s rule and a hump-shaped Apparently, these spiders are more vulnerable to change of decline of species richness are the main characteristics of their vegetation with altitude (see Community structure) and that is altitudinal distribution. Two kinds of community structure are why they are not favoured at higher elevations. Instead, observed, one that characterizes lower elevations (up to Gnaphosidae seem to be the most tolerant among other spider 1000 m) and one that is observed at the summits. Activity of families as shown in a comparative analysis on a family level at the family as a whole does not correlate with altitude as it is Lefka Ori (Lymberakis, 2003). This is also reported by other highly species-specific. The ecological profile of Gnaphosidae, authors (Otto & Svensson, 1982) and may be due either to as well as historical components of the formation of the Cretan competitive release or to physiological/behavioural adaptations mountains are mainly responsible for these characteristics. The which allow members of this family to overcome harsh Mediterranean/insular character of the study area and the conditions at higher elevations. Moreover, some species continuous degradation, especially of the lowland areas near become even more abundant there (see Table 4). This the coasts, are thought to influence the composition and the ecological pattern is followed by species of some other families response of organisms there. that belong to the same guild (wandering spiders) such as The great variety of results among studies that deal with this Lycosidae, Philodromidae and Thomisidae (Lymberakis, topic indicates that the factors governing these phenomena are 2003). In all cases this is due to the new appearance of species not yet clear. Reasons which add to this controversy are the which occur above a certain altitude. Therefore, competitive following: use of different taxa, different latitudes at which interaction is probably the reason for the observed patterns. studies are carried out, special ecological or historical condi- The positive correlation between activity of invertebrate taxa tions prevailing at each study area, differences in sampling and altitude is not very common on Crete, as shown in method, the duration and the geographical range of the Lymberakis (2003). The author reports a positive correlation sampling in each survey (Lawton et al., 1987; McCoy, 1990; in some families of Coleoptera (such as Curculionidae and Lomolino, 2001). Our results add to this general idea that there Tenebrionidae), in Opiliones, Homoptera, Dictyoptera, Lepi- is not a single overriding factor which defines the response of doptera and Diptera, but a negative correlation in other organisms to environmental gradients, but rather a combina- families of Coleoptera (such as Carabidae and Scarabaeidae), tion of factors, the intensity of which depends largely on the in Hymenoptera and slugs. A less apparent pattern of activity is local conditions and the history of a region, and on the special documented for scorpions, diplopods, isopods, chilopods and characteristics of each taxon.

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826 Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd Altitudinal distribution of ground spiders

BIOSKETCHES

Maria Chatzaki’s research focuses on taxonomy and island biogeography of spiders. She is interested in recognizing the origins of the Greek spider fauna as a result of the interplay between palaeogeography and the special characteristics of the taxa under consideration. Petros Lymberakis is the curator of the vertebrate collection at the NHMC. His research focuses on ecology and biogeography of small vertebrates in the Eastern Mediterranean.

Georges Markakis is Associate Professor of Biostatistics in the Technological Education Institute of Crete. He has a PhD in probability and fuzzy logic and has also experience in many specialized statistical methods dealing with biological and ecological problems. He is interested in designing and applying expert systems for water management.

Moisis Mylonas is a Professor in the Department of Biology of the University of Crete and Director of the NHMC. He is mainly interested in evolutionary island ecology and conservation ecology.

Editor: Philip Stott

Appendix 1 Sites description: code names of sites and number of samplings at each one of them (in parentheses); period of each sampling; habitat type; altitudinal zone; number of active traps and active days for each sampling. Asterisks in the ‘Period’ column indicate cases in which the number of active days was considered as shorter than the total duration of sampling because of snow cover during winter time

Code names (number of samples/site) Period Habitat type Altitudinal zone Number of active days Number of active traps l020 (4) 25/4/96–26/6/96 CP ZER 62 18 26/6/96–25/8/96 59 17 25/8/96–29/10/96 66 16 13/3/97–7/5/97 55 18 l030 (3) 25/4/96–26/6/96 FW ZER 61 9 26/6/96–22/8/96 57 9 22/8/96–30/10/96 67 9 l050 (3) 25/4/96–25/6/96 FW ZER 54 11 25/6/96–20/8/96 56 15 20/8/96–30/10/96 69 14 10800 (7) 28/3/91–5/5/91 P LOW 38 33 5/5/91–8/6/91 34 35 8/6/91–6/7/91 28 36 6/7/91–4/8/91 28 37 4/8/91–8/9/91 36 35 8/9/91–5/10/91 27 35 9/3/92–5/4/92 28 25 l01200 (6) 28/3/91–5/5/91 M MID 38 39 5/5/91–8/6/91 34 37 8/6/91–6/7/91 28 35 6/7/91–4/8/91 28 38 4/8/91–8/9/91 36 39 8/9/91–5/10/91 27 37 l01600 (8) 29/7/90–1/9/90 SS TOP 35 24 1/9/90–17/10/90 46 24 28/3/91–5/5/91 39 34 5/5/91–8/6/91 34 34 8/6/91–6/7/91 28 31 6/7/91–4/8/91 28 37 4/8/91–8/9/91 35 37 8/9/91–5/10/91 28 40

Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd 827 M. Chatzaki et al.

Appendix 1 continued

Code names (number of samples/site) Period Habitat type Altitudinal zone Number of active days Number of active traps l02000 (6) 29/7/90–1/9/90 SS PEAK 35 32 1/9/90–16/10/90 45 34 8/6/91–6/7/91 29 28 6/7/91–4/8/91 29 27 4/8/91–7/9/91 34 28 7/9/91–6/10/91 29 28 l02400 (1) 29/7/90–1/9/90* SS PEAK 35 8 psio (3) 25/4/96–25/6/96 M ZER 61 14 25/6/96–26/8/96 60 14 26/8/96–31/10/96 67 14 psi50 (3) 25/4/96–25/6/96 CP ZER 60 10 25/6/96–26/8/96 60 10 26/8/96–31/10/96 67 10 psi200a (4) 22/4/00–6/7/00 IP ZER 75 16 6/7/00–14/9/00 70 16 14/9/00–7/11/00 54 13 12/3/01–8/5/01 57 16 psi200b (2) 20/4/99–30/6/99 IP ZER 71 20 30/6/99–1/9/99 63 20 psi300a (3) 24/2/99–20/4/99 FW ZER 71 19 20/4/99–30/6/99 63 18 30/6/99–1/9/99 65 19 psi300b (3) 16/3/99–20/5/99 FW ZER 65 18 20/5/99–26/7/99 67 18 26/7/99–30/9/99 66 18 psi650 (2) 19/4/99–10/6/99 IP LOW 52 19 10/6/99–18/8/99 69 20 psi750 (2) 19/4/99–10/6/99 IP LOW 52 18 10/6/99–18/8/99 69 18 psi1000a (3) 16/4/99–9/6/99 M MID 54 17 9/6/99–17/8/99 69 17 17/8/99–19/10/99 63 19 psi1000b (3) 16/4/99–9/6/99 IP MID 54 19 9/6/99–17/8/99 69 20 17/8/99–19/10/99 63 20 psi1000c (2) 19/4/99–10/6/99 M MID 52 16 10/6/99–18/8/99 69 17 psi1200 (2) 22/4/99–20/7/99 IP MID 89 19 20/7/99–29/9/99 70 19 psi1650 (4) 14/4/00–2/7/00 SS TOP 78 12 2/7/00–14/9/00 75 15 14/9/00–30/10/00 45 14 24/3/01–12/6/01 80 14 psi1950 (4) 14/4/00–2/7/00 SS TOP 78 18 2/7/00–14/9/00 75 17 14/9/00–30/10/00 45 17 24/3/01–12/6/01 80 18 psi2200 (2) 15/9/00–31/10/00 SS PEAK 47 14 31/10/01–13/6/01* 60 14 diktoa (3) 26/3/99–26/5/99 CP ZER 61 20 26/5/99–28/7/99 63 19 28/7/99–28/9/99 62 20 diktob (3) 3/3/99–4/5/99 FW ZER 62 17 4/5/99–22/7/99 79 19 22/7/99–22/9/99 61 16

828 Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd Altitudinal distribution of ground spiders

Appendix 1 continued

Code names (number of samples/site) Period Habitat type Altitudinal zone Number of active days Number of active traps dikt50 (3) 6/4/97–2/6/97 M ZER 57 14 2/6/97–7/8/97 66 14 7/8/97–10/10/97 64 14 dikt300 (3) 21/4/00–12/7/00 IP ZER 82 10 12/7/00–11/10/00 91 13 9/3/01–6/5/01 58 8 dikt350 (2) 4/5/99–23/7/99 IP ZER 80 20 23/7/99–23/9/99 61 18 dikt700 (3) 15/4/99–8/6/99 IP LOW 54 19 8/6/99–4/8/99 57 18 4/8/99–28/9/99 55 18 dikt800 (2) 5/5/99–23/7/99 IP LOW 79 18 23/7/99–23/9/99 61 17 dikt1200 (2) 26/5/99–28/7/99 IP MID 63 19 28/7/99–28/9/99 62 19 dikt1450 (2) 11/5/00–5/8/00 SS MID 85 14 5/8/00–2/10/00 59 14 dikt1750 (2) 11/5/00–5/8/00 SS TOP 85 15 5/8/00–2/10/00 59 15

Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd 829 830 Chatzaki M.

Appendix 2 Mean number of individuals per 100 trap days at each site of the study area. Sites are coded by mountain massif (LO, Lefka Ori; PSI, Psiloreitis; DIK, Dikti) and by altitude

LO PSI DIK tal. et

20 30 50 800 1200 1600 2000 2400 0 50 200a 200b 300a 300 b 650 750 1000a 1000b 1000c 1200 1650 1950 2200 0a 0b 50 300 350 700 800 1200 1450 1750

A. pallens 0.10 0.19 0.23 0 0 0 0 0 0.23 0.33 0.24 0.15 0.40 0.4 1 0.12 0.08 0 0.23 0 0.08 0.11 0.31 0 0.453 0.12 0.32 0.52 0.30 0.17 0.08 0 0 B. amabilis 0.45 0 0.20 0.50 0 0 0 0 0.30 0.33 0 0.07 0 0 0 0 0 0 0 0 0 0 0 0.58 0 0.11 00000 0 0 B. ensigera 0 0.30 0.24 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.27 0 00000 0 0 B. plumalis 00000 0 0 0 000 0 0 0 000 0 0 0 0 0 0 0 0000000 0 0 Cal. cretica 0.21 0 0 0 0.22 2.53 0 0 0.24 0.49 0.46 0.16 0.21 0 0.48 1.17 0.86 0.07 0.09 0.38 2.91 0.14 0 0 0.12 0.22 0 0 0.40 0.98 0.75 1.66 0 Cam. metellus 0 0.19 0 0.24 0 0 0 0 0 0 1.42 0.22 0 0 0.09 0.08 0 0 0.24 0 0 0 0 0 0 0.76 0.15 0000 0 0 Ces. aspida 0.23 0 0 0.23 0.21 0 0 0 0.61 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.18 0.12 0000 0 0 Crypt. creticus 00000 0 0 0 000 0 0 0 00.11 0 0 0 0 0 0 0 0 0.08 0 0.12 0000 0 0 D. lapidosus 0 0.19 0.34 0.43 0 0 0 0 0 0 0 0 0 0 0 0.09 4.72 0 0.09 0.24 0 0 0 0 0 0 0 0 0.34 0.15 3.14 0.42 0 D. lutescens 0.27 0 0.74 0 0 0 0 0 0 0.17 0.41 0.07 0.15 0.08 0.14 0 0 0.29 0.82 0.24 0.18 0 0 0.167 0.07 0.13 0 0.09 1.66 0.19 0.59 0 0 D. oreinos 00000.31 0.28 5.09 1.04 0 0 0 0 0 0 0 0 0 0 0 0 1.17 2.65 1.89 0 0 0 00000.51 0.73 2.01 D. serratichelis 00000 0.17 0 0 0 0.17 0 0.07 0 0 0 0 0 0 0.12 0.12 0 0 0 0 0 0.11 00000 0 0 D. pumiloides 0 0 0 0.12 0.10 0 0 0 0 0 0 0 0.37 0 0.07 0.09 0.26 0 0.24 0 0.11 0 0 0.081 0 0.13 0.12 0 0.24 0.21 0 0 0 D. praeficus 0 0.55 0.56 0 0 0 0 0 0 0 0 0.07 1.04 1.91 0.71 1.28 8.12 1.46 0.52 4.20 2.13 0 0 0 0 0 0.26 0.06 1.66 1.62 2.01 0.84 0 ora fBiogeography of Journal G. bithynica 00000 1.62 3.29 0.52 0 0 0 0 0 0 0 0 0 0 0 0 0 1.82 0.41 0 0 0 00000 0 0.95 H. creticus 0.10 0 0 0.41 0.10 0.98 0 0 0 0.17 0 0 0 0 0.10 0 1.96 0 0 0 1.22 0 0 0 0.09 0 0.22 0 0.49 0 0.08 0.08 0 H. dalmatensis 0.30 0.55 0 0 0 0 0 0 0.12 0 0 0 0 0 0 0 0 0 0 0.57 0 0.64 0 0 0.36 0 0 0 0 0.07 0.08 0.14 0 H. minor 00000 0 0 0 000 0 0 0 000 0 0 0 0 0 0 0 00000.10 0 0 0 0 H. signifer 00000 0 0 0 000 0 0 0 000 0 0 0.24 0 0 0 0 0 0 00000 0.17 0 L. albidus 00000 0 0 0 000 0 0 0 00.11 0 0 0 0 0 0 0 0 0.07 0 0 0 0.10 0 0 0 0 L. femineus 0.09 0 0 0 0 0 0 0 0 0 0 0 0 0 0.07 0.75 0 0.08 0 0 0 0 0 0 0 0 0 0 0.10 0.07 0 0 0 L. hadjissaranti 00000 0 0 0 000 0.08 0 0.08 0 0 0 0 0 0 0 0 0 0 0.08 0 00000 0 0 32 L. manolisi 00000 0 0 0 000 0 0.07 0.08 0 0 0 0 0 0 0 0 0 0 0 0 00000 0 0 813–831, , L. pupa 00000 0 0 0 000 0 0 0.08 0 0.08 0 0 0 0 0 0 0 0.161 0 0 00000 0 0 M. albovittata 00000 0 0 0 00.17 0 0 0.22 0.17 0 0.21 0 0 0 0.06 0 0 0 0 0 0 00000 0 0 M. coarctata 0.20 0 0.49 0 0 0.14 0 0 0.60 0.58 0.08 0.14 0.07 1.33 0.36 0 0.26 0.07 0 0 0 0 0 0.163 0.07 0.11 0.10 0.09 0.10 0.14 0.08 0 0.16

ª M. dives 00000 0 0 0 000 0 0 0 00.21 0.09 0.19 0 0 0 0 0 0 0 0 0 0 0.10 0 0 0.42 0

05BakelPbihn Ltd Publishing Blackwell 2005 M. pygmaea 00000 0 0 0 000 0 0 0 000 0 0 0 0 0 0 0 0.09 0 00000 0 0 N. excerpta 2.09 0 2.31 1.09 0.28 0.20 0 0 0.12 2.83 0.61 0.36 0.15 0.38 0.87 0.47 0.51 0.20 0.48 1.66 0.90 0 0 0.329 0 0.54 0.56 0.28 0.33 0.10 0.17 0.23 0 N. ripariensis 00000 0 0 0 0.12 0.50 0 0.07 0.07 0 0 0.08 0 0 0 0 0 0 0 0 0.27 0 00000 0 0 P. senilis 00000 0 0 0 000 0 0 0 0.10 0 0 0 0 0 0 0 0 0 0 0 00000 0 0 P. lentiginosa 1.08 0.19 0.14 0.10 2.99 2.86 0 0 0 2.99 4.50 1.97 0.08 0.84 2.55 2.81 2.87 1.73 0.24 5.86 4.24 2.84 0 0.1655 0 0.34 1.76 0.13 1.34 0.07 5.91 8.65 7.15 S. peninsularis 0.09 0000 0 0 0 000 0 0 0 000 0 0 0 0 0 0 0 0000000 0 0 S. scutulatus 00000 0 0 0 000 0 0 0 000 0 0 0 0 0 0 0 000000.07 0 0 0 S. carmeli 0 0 0 0.23 0 0 0 0 0 0.50 0 0 0 0.09 0 0 0 0.10 0 0 0 0 0 0 0 0.13 00000 0 0 S. palearcticus 00000 0 0 0 000 0 0 0 000 0 0 0.06 0 0 0 0 0 0 00000 0 0 S. trichopus 00000 0 0 0 000 0 0.53 1.51 0 0 0 0.38 0 0 0 0 0 0 0 0 00000 0 0 ora fBiogeography of Journal T. adriaticus 0 0 0.34 0000001.83 0 0 00000000.18 0.32 0 0 0 000000000 T. barbatus 0 1.22 0 0.18 0 0 0 0 0.12 0 0 0 000000000000 000000000 T. lyonneti 00.19000000000.08 0.07 0 0.37 0 0 0 0000001.5605 0.62 0 0.12 0 0 0000 T. malkini 0 0 1.85 0.15 0 0 0 0 0.53 0.33 0.52 0.49 1.38 0.33 0.39 0.52 0.15 0.28 0.60 0 0 0 0 0.369 0.20 2.08 0.45 0 1.80 0.63 0.17 0.39 0 Z. aerosus 000000000000000000000000 000000000 Z. caucasius 0.97 0.37 0.57 0.13 0.33 0.95 0 0 0.12 3.33 0.63 4.71 3.56 1.08 1.17 1.19 1.46 0.68 0.17 1.27 0.30 0.82 0 0 0.47 0.33 2.83 0.13 0.81 0.69 0.29 0.59 4.97 Z. cf. ilotarum 00.50000000000000.63 0 0 0 0.77 000000 00000.5302.15 0 0 Z. creticus 0 0 1.25 0.57 1.94 0.57 0.80 0 0.84 2.75 0 0 1.83 0000000.92 0 0 0 0 000000000 32

813–831, , Z. daidalus 0.14 0 0 0.14 0 0 0 0 0 0 0.25 0.14 0.07 0.08 0 0.08 0 0000000 00.11 0.35 0 0 0000 Z. labilis 0.61 0.19 0 0.33 0.18 0.30 0.96 2.59 0 0.67 1.51 1.42 1.06 2.32 0.84 0.48 0.18 0.43 0.09 0.13 0.44 0.91 0 0.332 0.13 0.22 0.86 0.17 0.68 0.40 0.13 0.54 0.86 Z. minous 0 0 0 0.12 0 0 0 0 0 0 0.17 0 000000000000 00.11 0.63 0 0 0000 Z. nilicola 000000000000000000000000 0.47 00000000

ª Z. scrutatus 0.18 0.77 0.14 0000001.17 0.81 1.37 0.44 1.25 0.31 0.45 0 0.96 0 0.18 0.11 0 0 0.1235 0.15 0.22 0.56 0.08 0.19 0.07 0.08 0 0 05BakelPbihn Ltd Publishing Blackwell 2005 Z. solstitialis 00000000000.09 0.08 1.21 1.43 0 0.08 0 0000000.241 0.85 0.11 0 0 0 0000 Z. subterraneus 3.31 0 0.96 2.18 0 0 0 0 0 2.84 2.28 0.28 1.90 0.78 0.20 0.53 0.29 0.47 0.51 0.37 0.84 1.14 1.15 0.322 0.40 2.94 1.40 0.90 0.57 1.06 0.25 1.13 0.38 Z. tenuis 0.46 1.65 3.25 1.70 0.21 0 0 0 1.26 0.50 1.32 0.47 2.62 1.17 2.61 0.24 0.17 0.75 0.78 0 0 0 0 3.528 0.72 0.99 0.39 1.66 3.16 1.12 0 0 0 liuia itiuino rudspiders ground of distribution Altitudinal 831