Estuarine, Coastal and Shelf Science 58S (2003) 93–104

Comparative diversity analysis in sandy littoralecosystems of the western Mediterranean

I. Colombinia,*, M. Fallacia, F. Milanesia, F. Scapinia, L. Chelazzib

aDipartimento di Biologia Animale e Genetica ‘‘Leo Pardi’’, Via Romana 17, 50125 Florence, ItalybIstituto per lo Studio degli Ecosistemi del CNR, Via Romana 17, 50125 Florence, Italy

Received 23 October 2001; accepted 31 July 2002

Abstract

A comparative faunal analysis was carried out in sandy littoral localities differing both morphologically and in human impact.The study sites were located in the western Mediterranean basin along the coasts of Morocco, Tunisia, the Maltese Islands and Italy.These were typical beach–dune ecosystems more (Smir, Morocco; Zouara, Tunisia; Burano, Italy) or less (Ir-Ramla tat-Torri, Malta

and Ir-Ramla l-Hamra, Gozo) structurally developed accordingly.Species richness was evaluated using standard trapping techniques with pitfall traps along the transects perpendicular to the

shoreline. Only isopods and coleopterans were used in the analysis. In each locality, an analysis was conducted on both the beachand the dune separately, and on the entire ecosystem in the two seasons (spring and autumn). Species were studied both

quantitatively and qualitatively using ecological coefficients (relative abundance) and Fisher’s diversity index. To evaluate theevenness of the community, Shannon–Weaver index was calculated and compared with Brillouin index. For both indices, themaximum values were computed and were used to obtain the evenness of the community through Pielou index. In addition,

Simpson’s dominance index was considered. Percentages of similarities between localities were analysed in the two seasons and intotal using the Renkonen index. The overall analysis showed that general trends could be found for both orders that were studiedand gave indications on habitat quality. The study showed that when monitoring was carried out systematically both in space and

time, arthropods could be used as important tool to assess beach health.� 2003 Elsevier Ltd. All rights reserved.

Keywords: arthropods; diversity indices; beach–dune ecosystem; beach health; Mediterranean Sea

1. Introduction

Species richness and diversity are commonly used forconservation purposes and to assess ecosystem fitness.Monitoring determines the status of biological diversityat one or more ecological levels and assesses changes overtime and space. Ecological studies concerning more�natural� areas (coastal environments, forests etc.) showthat species diversity is strongly correlated with habitatdiversity. Furthermore, environmental heterogeneity inspace and time is important for species diversity and isrelated to disturbance regimes. Homogeneous landscapes(pinewood plantation on dunes, agricultural systems)are valuable to loss of habitat, and as fragmentation

* Corresponding author. E-mail address: chelazzi@ise.cur.it.

E-mail address: scapini@dbag.unif.it (F. Scapini).

0272-7714/03/$ - see front matter � 2003 Elsevier Ltd. All rights reserved

doi:10.1016/S0272-7714(03)00035-0

increases, patch size and isolation aggravate the effect ofhabitat loss (Niemela, 2000). The increasing homogeni-sation of the world’s landscape is one of the major causesof rapid loss of species. In the Mediterranean basin, thehistorical load of human land use and occupation isperhaps the over-riding ecological factor to be consideredand is of paramount importance when interpretingstructure, composition and functioning of any ecosystem(Le Floc’h et al., 1998). Diversity monitoring generallyuses the distribution and abundance of organisms andtheir associations with the physical environment todetermine the status or changes in diversity over timeand space. To achieve this information, diversitymonitoring may be conducted on a vast range ofecological scales using a variety of techniques (surveying,cataloguing, quantifying) andmapping entities (Niemela,2000; Stork & Samways, 1995).

.

94 I. Colombini et al. / Estuarine, Coastal and Shelf Science 58S (2003) 93–104

In most ecosystems, arthropods are a major faunacomponent; thus, they are generally used to assess levelsof diversity. In the past, Mediterranean beach–dunesystems have been over-exploited or destroyed byhumans not only for recreational purposes, but also byurbanisation and industrial and/or agricultural en-croachment. Furthermore, in some cases, negligenceand ignorance have transformed these environmentsinto dumping areas, as people were convinced thatbeaches were devoid of valuable faunal components.This general tendency has caused most Mediterraneansandy beach ecosystem to become degraded environ-ments and impoverished in species. One of the mainobjectives of the research was to provide baselineinformation on the present state of the beaches throughthe study of species assemblages and, in particular, ofterrestrial arthropod communities of beach environ-ments. A comparative study of several beaches carriedout seasonally over a relatively short period of time (2years), using the same sampling techniques, representeda new approach for the Mediterranean basin.

In the literature, concerning Mediterranean areas,there is an extensive comparative study (DelamareDebouteville, 1960) of several beaches along the coastsof Algeria, Tunisia, France and Italy; but this workmainly compared the intertidal macrobenthic commu-nities. Very few studies have been undertaken onterrestrial macrofauna of sandy beaches, (Angelier,1950; Bigot, Picard, & Roman, 1982; Binaghi, 1964;Fallaci, Colombini, & Chelazzi, 1994; Gimenez Casal-duero & Esteve Selma, 1994; Ponel, 1983), and thesehave mainly considered single localities with no com-parisons being made between beaches.

The aim of the present research was to comparespecies richness over a range of beach–dune systems ofthe western Mediterranean in order to provide baselineinformation for future monitoring of impacts and toanalyse which are the most important physical factorsaffecting diversity in temperate areas with negligibletidal regimes and relatively small wave action.

2. Materials and methods

2.1. Study sites

The study sites were located in the west of theMediterranean basin along the coasts of Morocco,Tunisia, the Maltese Islands and Italy (Fig. 1). Thesewere typical beach–dune ecosystems, more (Smir,Morocco; Zouara, Tunisia and Burano, Italy) or less(Ir-Ramla tat-Torri, Malta and Ir-Ramla l-Hamra,Gozo) structurally developed accordingly.

2.1.1. Restinga Smir (Morocco)The study area of Restinga Smir lies on the northern

coast of Tetouan and consists of Smir lagoon with

Kabyla beach seawards and a dam inland with anartificial lake that conveys the waters of Oued Smir. Theonly area that still conserved the original beach–dunefeatures was located to the south of the Restinga Smirport. This area, chosen as our study site, presenteda beach with a supralittoral (about 30m) provided withabundant pioneer plants. The dune was characterised bytypical vegetation (foredune: Ammophila arenaria, Pan-cratium maritimum, Elytrigia juncea, Eryngium mariti-mum, Cakile maritima and Mesembryanthemum sp.;dune: Juniperus phoenicea, Helichrysum stoechas, Pista-cea lentiscus and Elytrigia juncea; landwards: Eucalyptussp.).

2.1.2. Zouara (Tunisia)In the northwestern coast of Tunisia, in a region

between Tabarka and Cap Negro, there is an extensivebeach–dune system interrupted in several points by theriver mouths, of which the most important is the OuedZouara. The fluvial valley of the Oued Zouara flows intothe sea at the Zouara beach, a well-developed beach,which is backed by high coastal dunes. The site chosenfor the study was located at about 3 km west from themouth of the Oued Zouara. The beach (eulittoral)devoid of vegetation was backed by a high dune belt.The vegetation cover of the supralittoral and duneincluded many species typical of this environment.Dominant species of the dune were Ammophila arenaria,Eryngium maritimum and Euphorbia paralias.

2.1.3. Ir-Ramla tat-Torri (Malta)This site was the northernmost sandy beach on the

island of Malta and was located on the Marfa Peninsula.This locality presented a small pocket beach. The dunewas extremely low and its foredune was covered bydominant pioneer species, such as Elymus farctus andEryngium maritimum. Dune species also includedPancratium maritimum, Otanthus maritimus and Eu-phorbia spinosa. A small number of Tamarix africanashrubs formed the climax community on the upperreaches of the dune. During the two sampling periods,

0 500 km

12

3

5

4

40 N

0

40 N

0

N

Fig. 1. Map of the study sites in the Mediterranean basin. (1) Restinga

Smir (Morocco), (2) Zouara (Tunisia), (3) Ir-Ramla tat-Torri (Malta),

(4) Ir-Ramla l-Hamra (Gozo), (5) Burano (Italy).

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the beach was covered by enormous quantities ofwracks, mainly composed of Posidonia oceanica.

2.1.4. Ir-Ramla l-Hamra (Gozo)This beach was located in the north of Gozo Island

and represented the best-preserved example of a sand–dune ecosystem in the Maltese Islands. It lay at themouth of a water-eroded valley between two plateaux.During the rainy season, a temporary stream bisectedthe beach and deposited large amounts of sediment intothe sea. To the east of the beach, there was a portion ofthe original beach–dune system, fairly well conserved,where typical pioneer plants were found (Cakilemaritima, Sporobolus arenarius, Pancratium maritimum,Echinophora spinosa, Eryngium maritimum, Otanthusmaritimus, Medicago marina). At the back of the dune,a perennial shrub of Tamarix africana grew thickly.

2.1.5. Burano (Italy)Between the sea and the Burano Lagoon (Capalbio,

Grosseto) lies a sand bar, where two dunes covered byvegetation can be clearly distinguished. The beach–dunesystem was subdivided into three different zonesaccording to the morphology, exposure and vegetationcover. The eulittoral zone included the part of the beachthat was devoid of vegetation, where beach debris wasstranded by the sea. The supralittoral zone extendedabout 20m and formed the foredune with pioneerplants, such as Cakile maritima, Pancratium maritimum,Echinophora spinosa, Otanthus maritimus, Medicagomarina and Ammophila arenaria. The extralittoral zone,covered by a Mediterranean maquis (Juniperus phoeni-cea, Juniperus oxycedrus macrocarpa, Pistacea lentiscus),was investigated to the summit of the second dune belt.

2.2. Sampling procedures

During April and October 1999, field studies wereconducted in Tunisia at the site of Zouara. In May andOctober 2000, the Moroccan site was surveyed, whereasthe Maltese sites were visited during April andNovember. The data of the Italian locality are basedon the months of May and November of a 1-yearsampling campaign that was conducted in 1986. In eachlocality, the same sampling effort, i.e. same methods andsame trapping period, was made.

The general procedures consisted in placing tworeplicate transects perpendicular to the shoreline tointercept crawling arthropods. These consisted of pitfalltraps placed at a distance of 5m from each other fromthe high water line to the backdune. The traps weremade with plastic cups (20 cm high and 10 cm indiameter) pushed in the sand to their rim and connectedto one another by fibreglass bands (10 cm high and 5mlong). At sites where beach–dune systems were quite

wide (Smir, Ir-Ramla l-Hamra, Burano), continuoustransects were replaced with tetra-directional pitfallcross traps placed at equivalent distances from oneanother or according to vegetation cover and/or habitatchanges. The number of these traps varied according tothe width of the different beaches. Transects were keptactive for 72 consecutive hours, during which recognis-able taxa were counted. These animals were thenreleased at the end of the sampling period. All othersamples were fixed in 75% alcohol and stored in thelaboratory. Only isopods and coleopterans were chosenand sorted. Individuals were sorted with the criteria ofthe morphologically recognisable taxonomic units(RTUs) (Kruger & McGavin, 1997). This methodconsisted in subdividing each order at family level andthen in grouping the different species of each family withconventional names (family name 1, 2, 3 etc.).

Beach–dune profile and orientation were registered incorrespondence to the transects. Sand samples weretaken at each trap to evaluate grain size according toFolk and Ward (1957). Mean tidal excursions of eachlocality were calculated using Admiralty Tide Tables.

2.3. Data analysis

Ecological coefficients such as relative abundancemay be used to provide an estimate of how thecommunity is structured (Bigot & Bodot, 1973; Ponel,1983; Van Heerdt & Morzer-Bruyns, 1960). These in-volved estimating the abundance of individual species, asa function of the total number of individuals gathered ina particular zone or season. Species were consideredabundant if greater or equal to 5% of captures.

Diversity indices were calculated for the differentlocalities and were used to identify species richness. Theanalysis was carried out on a seasonal basis both on thebeach and on the dune. The a diversity index of Fisher,Corbet, and Williams (1943) was used, and confidencelimits were calculated using the standard error given inWilliams (1947). To analyse the evenness of thecommunity, Pielou’s (1978) evenness index throughBrillouin (1962) index was used instead of the Shannonand Weaver’s (1949) index. To express the abundance ofthe commonest species as a fraction of the total numberof individuals, Simpson’s (1949) dominance index wascalculated. For a quantitative and qualitative analysesof the different zones, seasons and localities, Renkonen’s(1938) percentage similarity was computed.

Simple linear regression analysis (Zar, 1984) wasapplied to correlate beach features (beach orientation,exposure rate, length, width and slope of the beach,grain size, dune height, and tidal excursion) with adiversity indices of the coleopterans and isopods.Significant levels of probability were considered whenp < 0:05.

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3. Results

3.1. Beach characteristics

Beach–dune features of the five study sites arereported in Table 1. The localities showed differentcharacteristics, with Zouara being the most exposed,with the lowest beach slope and the highest dune.Contrarily, the two Maltese sites were pocket beacheswith low dune elevation and fine grain size. The Italiansite presented the longest extension, an SE exposure,highest beach slope and coarser sand size.

3.2. Abundance analysis

At Smir, during the entire study period, 1014coleopterans, belonging to 47 species, were collected.Abundance analysis calculated for the total of the twostudy periods showed that the Tenebrionidae Phaleriaacuminata was the most abundant species (34.0%). Ofthe 47 species, 36 were sampled in May and 29 inOctober. In spring, three species, belonging to theTenebrionidae family, were classified as abundant: P.acuminata, Erodius sp. and Te8. In October, there wasan increase in abundant species, with the CurculionidaeCur25, the Staphylinidae Phytosus nigriventris, theCryptophagidae Cryptophagus sp. followed by P.acuminata, the Carabidae of the genus Amara and theTenebrionidae Xanthomus pallidus. For the isopods,9152 individuals belonging to six species were sampled.In May, five species occurred, whereas in October onlythree. In both seasons, the most abundant species wasTylos europaeus.

At Zouara, a total of 6148 coleopterans, belonging to63 species, was collected and Phytosus nigriventris wasthe most abundant species (56.5%). Of these species, 44were present in April and 34 in October. During April,the most abundant coleopteran species was P. nigri-ventris together with an Anthicidae (Anthicus fenestra-tus), a Histeridae Hi1 and Phaleria acuminata. In

October, the latter species became the most abundantfollowed by Xantomus pallidus, a Scarabaeidae (Geo-trupes stercorarius), a Carabidae (Eurynebria compla-nata) and a Tenebrionidae (Pseudoseriscius olivieri). Forthe isopods, a total number of 12,440 individuals weresampled. These belonged to three species, with Tyloseuropaeus being the most abundant in both seasons(99.9%).

At Ir-Ramla tat-Torri, a total of 2141 coleopteransbelonging to 60 species were collected, with Phaleriabimaculata being the most abundant species (43.8%). Ofthese, 47 species were collected in April and 25 inNovember. In spring, the most abundant species wasP. bimaculata followed by Cryptophagus sp. and thetenebrionids Phaleria acuminata and Trachyscelis sp.In autumn, the number of species was reduced to almosthalf, with Cryptophagus sp. that remained an abundantspecies, but increased to 64% of captures. This specieswas followed by the Ptiliidae Acrotrichis sp. For theisopods, a total number of 212 individuals weresampled. These belonged to seven different species thatwere present altogether in April and reduced to three inNovember. In spring, the most abundant species wereAgabiformius obtusus and Porcellio laevis that werecaptured on the entire beach–dune system. In Novem-ber, the three species found were all classified asabundant. Ligia italica and Stenophiloscia zosterae weretypical of the beach zone, whereas A. obtusus was caughton the dune.

At Ir-Ramla l-Hamra, a total of 6542 coleopteransbelonging to 62 species were collected. Of these, 54species were collected in April and 19 in November. Thetotal of the two study periods showed that Phaleriaacuminata was the most abundant species (43.4%).In April, again the most abundant species wasP. acuminata. This was followed by a Cryptophagidae(Cr1), an Elateridae Cardiophorus sp. and Anthicusfenestratus. In November, the number of abundantspecies increased, but P. acuminata still remained themost abundant. Also a carabid (Ca15), a cryptophagid

Table 1

Beach–dune features are shown in the five study localities

Smir Zouara Torri Hamra Burano

Co-ordinates N 35�429550 N 37�009410 N 35�599330 N 36�039430 N 42�239500

W 05�209050 E 08�539260 E 14�219550 E 14�179080 E 11�229400

Beach orientationa 350�–170� (N) 220�–40� (N) 195�–15� (N) 270�–90� (N) 105�–285� (S)

Exposure rateb 12.5 16 10.5 9.5 11.5

Beach length (km) 20 25 0.120 0.450 60

Beach width (m) 55 50 20 20 35

Beach slope (%) 9 3 6.5 11 24.5

Mz (U) 1.413 1.438 1.842 1.945 1.295

Dune height (m a.s.l.) 7 20 2 4 8

Tide excursion (cm)c 30–70 10–20 0–20 10–20 10–30

a N, sea towards north; S, sea towards south.b According to McLachlan, 1980.c Differences between mean high and low tides of neap and spring tides, respectively.

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(Cr1), Xantomus pallidus, Pseudoseriscius olivieri andanother carabid (Ca4) were all classified as abundantspecies. Regarding the isopods, 14,619 individualsbelonging to four species were found. Tylos europaeuswas the only species found abundantly in both seasons(99.6 and 100%).

At Burano, a total of 340 coleopterans belonging to68 species were collected, with Anthicus fenestratus beingthe most abundant species (14.7%). Of these, 56 specieswere collected in May and 15 in November. In May,A. fenestratus, the Staphylinidae Atheta amicula and theCurculionidae Brachytemnoides filum were all classifiedas abundant species. In November, the number ofabundant species increased and the ChrysomelidaePsylliodes pallidipennis was the most abundant. Thiswas followed by Eurynebria complanata, Xantomuspallidus and the Staphylinidae Othius laeviusculus. Re-garding the isopods, a total of 1205 individualsbelonging to two species were found, of which onlyfour individuals were found in May. Again, Tyloseuropaeus was the most abundant.

3.3. Ecological indices

In general, for the coleopteran community, Fisher’sdiversity index (Table 2) was higher in spring than inautumn at all sites, except for Zouara, where theopposite occurred. Furthermore, these values werehigher on the dune than on the beach (except for Ir-Ramla tat-Torri). There are, however, exceptions tothese general trends when the values were calculated forthe beach and the dune in each season separately. AtSmir, the highest diversity index was obtained on thedune in October instead of May. At Zouara, the lowesta value was recorded on the beach in April, and atIr-Ramla l-Hamra, on the dune in November instead ofon the beach in autumn. The value of a for the entirebeach–dune system was highest at Burano and lowest atIr-Ramla l-Hamra.

Fisher’s diversity index for the isopod community(Table 3) presented general trends similar to those of thecoleopterans. In fact, a values were higher, on the dunewith respect to the beach, in spring than in autumn. Inthis case, the exception was Ir-Ramla tat-Torri, wherethe opposite occurred. In particular, calculating these

values for the beach and the dune in each seasonseparately revealed that again Ir-Ramla tat-Torri wasthe exception together with Smir, which presented thelowest a value on the beach in May instead of October.The isopod community presented quite low a values forthe entire beach–dune system, with a maximum at Ir-Ramla tat-Torri and minimum at Burano.

The index of evenness, estimated for the coleopteransover the entire beach–dune system by means of thePielou–Brillouin method (Table 4), was highest atBurano and lowest at Ir-Ramla l-Hamra. This valuewas higher in autumn than in spring, except for Burano,where trends were opposite and for Ir-Ramla tat-Torri,where similar values were obtained. Generally, highervalues were found for the dune compared with the beach.In particular, lower values were obtained on the beach inspring at all sites, whereas higher ones in autumn on thedune for three of the five localities. Burano was thelocality that registered the highest index of evenness onthe dune in spring, whereas the lowest occurred at Ir-Ramla l-Hamra on the beach again in spring.

The equivalent values of evenness for the isopodcommunity over the same beach–dune systems (Table 5)were extremely low, reaching 0.004 for Zouara. Only Ir-Ramla tat-Torri presented a value over 0.5. In general,in spring and on the beach, the values of evenness werelower than in autumn and on the dune. However,Zouara and Burano did not follow the seasonal trendand an opposite tendency was obtained. On the otherhand, Ir-Ramla tat-Torri did not follow the spatialtrend. In particular, the lowest value was obtained onthe beach during spring at Ir-Ramla l-Hamra, whereasthe highest at Smir on the dune during the same season.In many cases, values were not calculated because of thepresence of only one species.

The overall Simpson’s dominance index calculatedfor the coleopterans in the different sites (Table 6) washighest at Zouara and lowest at Burano. Moredominant species were found in spring than in autumn,but Ir-Ramla tat-Torri and Burano were the exceptions.Furthermore, a greater number of dominant specieswere found on the beach than on the dune. In particular,the highest dominance index was found at Smir in Mayon the beach, whereas the lowest at Burano on the dunein the same month.

Table 2

Fisher’s diversity indices calculated for the coleopterans of the five localities in the different seasons, zones and on the total

Spring Autumn

Beach Dune Beach Dune Spring Autumn Beach Dune Total N N species

Smir 4.19 6.42 3.26 7.19 8.06 7.75 5.37 9.17 10.20 1014 47

Zouara 3.31 8.50 5.55 4.83 6.56 7.22 5.90 10.38 9.77 6148 63

Torri 2.74 11.95 2.69 8.93 8.90 5.91 3.77 15.94 11.46 2141 60

Hamra 5.05 6.41 4.11 3.49 8.12 4.71 6.32 7.11 9.48 6542 62

Burano 14.73 17.33 4.52 6.18 20.55 7.61 17.40 22.12 25.56 340 68

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Table 3

Fisher’s diversity indices calculated for the isopods of the five localities in the different seasons, zones and on the total

Spring Autumn

Beach Dune Beach Dune Spring Autumn Beach Dune Total N N species

Smir 0.09 3.18 0.20 0.53 0.55 0.32 0.19 2.26 0.63 9152 6

Zouara 0.09 1.59 0.09 0.56 0.32 0.19 0.08 0.92 0.28 12,440 3

Torri 1.70 0.76 1.59 0.80 1.40 2.39 1.66 0.75 1.39 212 7

Hamra 0.20 1.13 0.09 0.38 0.43 0.09 0.18 1.50 0.38 14,619 4

Burano 0.80 0.80 0.11 0.64 1.59 0.23 0.11 0.60 0.23 1205 2

For the isopods, Simpson’s dominance index for theentire beach–dune system (Table 7) was extremely highand reached values close to 1 in almost all localities. Thisvalue remained more or less the same during the twoseasons at Smir, Zouara and Ir-Ramla l-Hamra,whereas it was higher and lower in spring at Ir-Ramlatat-Torri and Burano, respectively. In general, thedominance index was higher on the beach than on thedune, except for Ir-Ramla tat-Torri, where the oppositeoccurred. Low dominance values were obtained at thelatter locality in spring on both beach and dune, and atSmir on the dune.

3.4. Regression analysis

Of the eight local beach features (Table 1 excludingco-ordinates) that were tested with a diversity indices ofthe coleopterans and of the isopods, significant positivecorrelation were obtained only between the diversityindices of the coleopterans with beach slope (r ¼ 0:918,p ¼ 0:027).

3.5. Renkonen’s percentage similarity

The community of coleopterans collected at thedifferent study sites was compared with Renkonen’spercentage similarity in the two seasons (Fig. 2a) andbetween localities (Fig. 2b). Ir-Ramla tat-Torri pre-sented the highest percentage of similarity betweenseasons (24.5%) (Fig. 2a). This was followed by Smir,with percentage of similarity 20.1%, Zouara with16.7%, Ir-Ramla l-Hamra with 4.9% and Burano with4.7%. The highest percentage of similarity was obtainedbetween Smir in spring and Zouara in autumn (43.1%),

whereas the lowest between Burano in autumn and thetwo Maltese beaches in spring (0.2%). On the total (Fig.2b), the localities that presented the most similarcoleopteran fauna were Smir and Ir-Ramla tat-Torri,with percentage of similarity of 23.9%. The lowestsimilarity was instead found between Ir-Ramla l-Hamraand Burano (2.6%). Burano was most similar to Ir-Ramla tat-Torri (5.3%).

Comparing the isopod fauna between the two seasons(Fig. 2c), Smir was the locality that presented the highestpercentage of similarity (85.8%). This was followed byZouara with 67.8%, Ir-Ramla l-Hamra with 62.8%,Ir-Ramla tat-Torri with 4.7% and Burano with 0.6%.The highest percentage of similarity was found betweenSmir in autumn and Zouara in spring (96.3%). Highsimilarities were also found when the isopod fauna ofIr-Ramla l-Hamra of spring was compared with that ofSmir in both seasons and with Zouara in spring.Furthermore, the isopod fauna of Ir-Ramla l-Hamraof autumn was similar to that of Zouara in autumn.Comparing the isopod community of Burano with thatof other localities in the two seasons, the highestpercentage of similarity was found between Smir andBurano during autumn (46.3%). On the total (Fig. 2d),the localities that presented the most similar isopodfauna were Zouara and Ir-Ramla l-Hamra, witha percentage of similarity of 91.9%. High similaritieswere also found between Smir and Zouara and betweenSmir and Ir-Ramla l-Hamra. Ir-Ramla tat-Torri differedthe most in its isopod fauna when compared with theother study localities. Here, again Burano was mostsimilar to Smir (23%), and this was due to the similaramount of Tylos europaeus that were found in bothlocalities.

Table 4

Evenness indices, according to Pielou–Brillouin, calculated for the coleopterans of the five localities in the different seasons, zones and on the total

Spring Autumn

Beach Dune Beach Dune Spring Autumn Beach Dune Total

Smir 0.319 0.540 0.733 0.714 0.530 0.721 0.475 0.655 0.628

Zouara 0.351 0.631 0.470 0.713 0.381 0.599 0.360 0.679 0.422

Torri 0.396 0.628 0.424 0.778 0.439 0.453 0.462 0.634 0.466

Hamra 0.242 0.400 0.510 0.773 0.373 0.712 0.238 0.431 0.384

Burano 0.785 0.827 0.782 0.723 0.833 0.793 0.796 0.832 0.839

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Table 5

Evenness indices, according to Pielou–Brillouin, calculated for the isopods of the five localities in the different seasons, zones and on the total

Spring Autumn

Beach Dune Beach Dune Spring Autumn Beach Dune Total

Smir – 0.860 0.013 – 0.008 0.014 0.006 0.914 0.008

Zouara – 0.774 – 0.450 0.007 0.003 – 0.609 0.004

Torri 0.568 0.615 0.774 – 0.487 0.910 0.644 0.612 0.518

Hamra 0.007 0.533 – – 0.019 – 0.003 0.728 0.007

Burano – – – 0.724 1 0.073 – 0.669 0.084

4. Discussion

The comparative study of the different beachecosystems along the Mediterranean basin showed thatgeneral common trends could be found in the faunalcommunities even when the chosen localities presenteddifferent beach characteristics. First of all, there wasa general decrease in the number of coleopteran speciesand in capture numbers from spring to autumn. Anincrease in species number and abundance was alsoreported by Colombini, Aloia, Fallaci, Pezzoli, andChelazzi (1998) between dry and wet seasons of a sandybeach ecosystem along the coast of Somalia, i.e. whenmore favourable conditions for the arthropod commu-nity appeared. On Mediterranean beaches, the reductionof the total number of coleopteran species that weresampled during autumn months was generally associ-ated with an increase in the number of species classifiedas abundant. This was true for all localities except for Ir-Ramla tat-Torri, where the decrease in species numberwas associated with a decrease in the abundant species.This peculiar result found for the Maltese beach wasprobably related to the heavy human impact that thebeach undergoes during summer months. Abundantspring tenebrionid species, such as Phaleria bimaculata,Phaleria acuminata and Stenosis sp., were greatlyreduced in autumn months. It could be argued thatthese changes could have been related to the beetles’ lifecycles, but this does not appear to be the case sincecomparisons with three other localities (Smir, Zouaraand Ir-Ramla l-Hamra) showed P. acuminata to be anabundant species in both seasons. Human disturbancewas probably the major cause of the tenebrionds’reduction on the beach, as it was observed that therewas a tendency of beetles to shift their zonation from thebeach to the dune during autumn months.

Another general feature that appears for the co-leopteran community is that some beaches support moreTenebrionidae than Staphylinidae, as was the case ofSmir and of the two Maltese beaches, whereas at Zouaraand in other beaches of tropical areas, beach–dunecommunities were dominated by fungivorous andpredator Staphylinoidea (Colombini et al., 1998; Co-lombini, Aloia, Fallaci, Pezzoli, & Chelazzi, 2000),respectively. By contrast, Burano was dominated byAnthicidae when analysed in the two seasons, but whenthis analysis was carried out for the entire year, theTenebrionidae family was again dominant (Fallaci et al.,1994). The seasonal abundance analysis of Smir andZouara beaches showed opposite trends. At Smir duringspringtime, Tenebrionidae were most abundant, whereasduring autumn, Staphylinidae together with Curcu-lionidae were the most represented. At Zouara, in springand in autumn, the most abundant species were theStaphylinidae and Tenebrionidae species, respectively.

The abundance analysis made on the isopods showedsimilar trends with those found for the coleopterans. Asa matter of fact, the number of species was again higherin spring compared with autumn, even if speciesnumbers were always very low. In each locality, Tyloseuropaeus was always the most abundant species in bothseasons, except for Ir-Ramla tat-Torri, where thisspecies was totally absent. In addition, the number ofindividuals captured was always extremely high in eachlocality where T. europaeus was found. In the beacheswhere this species occurred, capture numbers increasedfrom spring to autumn months, and this was due to thepresence of the new generation that generally reaches itshighest numbers in autumn months (Fallaci, Colombini,Taiti, & Chelazzi, 1996). At Ir-Ramla tat-Torri, therewas no species that could be considered equivalent innumbers to T. europaeus. In April, beach zones were

Table 6

Dominance indices, according to Simpson, calculated for the coleopterans of the five localities in the different seasons, zones and on the total

Spring Autumn

Beach Dune Beach Dune Spring Autumn Beach Dune Total

Smir 0.645 0.330 0.185 0.179 0.271 0.125 0.403 0.180 0.166

Zouara 0.540 0.153 0.364 0.160 0.434 0.192 0.458 0.107 0.344

Torri 0.469 0.182 0.505 0.172 0.321 0.433 0.345 0.174 0.259

Hamra 0.578 0.332 0.470 0.156 0.298 0.155 0.574 0.307 0.287

Burano 0.114 0.092 0.225 0.273 0.059 0.152 0.094 0.074 0.048

100 I. Colombini et al. / Estuarine, Coastal and Shelf Science 58S (2003) 93–104

Table 7

Dominance indices, according to Simpson, calculated for the isopods of the five localities in the different seasons, zones and on the total

Spring Autumn

Beach Dune Beach Dune Spring Autumn Beach Dune Total

Smir 1 0.25 0.997 1 0.997 0.996 0.999 0.236 0.997

Zouara 1 0.5 1 0.801 0.998 1 1 0.577 0.999

Torri 0.419 0.479 0.5 1 0.446 0.267 0.371 0.482 0.431

Hamra 0.999 0.638 1 1 0.992 1 1 0.405 0.998

Burano 1 1 1 0.637 0.333 0.982 1 0.675 0.979

principally occupied by the terrestrial Porcellionidaespecies with wide habitat occupancy, whereas in dunezones, littoral and psammophilous species, such asArmadillidium granulatum and Leptotrichus panzerii,were present together with the Porcellionidae species.In November, the great reduction in capture numberscan again be associated to human disturbance.

Analysing capture numbers spatially, there wasa general decrease in abundance from the beach to thedune, in both the coleopteran and isopod communities.This was particularly evident for those beaches whereTylos europaeus was the dominant species. The onlybeach that presented an opposite trend was Ir-Ramlatat-Torri, where isopods were more abundant on thedune than on the beach.

The overall results of the diversity indices calculatedfor the coleopteran and isopod communities of eachlocality showed that in the two communities similartrends were present. For the coleopterans, a diversitywas higher in spring than in autumn, except for Smirand Zouara, where no significant differences occurred.This same tendency was found for the isopods of alllocalities, except for Ir-Ramla tat-Torri, where theopposite occurred. Furthermore, a diversity increasedfrom beach zones to dune areas, and this was true evenwhen seasons were analysed separately. This confirmsMcLachlan’s (1991) statements, according to whichfaunal responses change along the gradients from thebeach landwards, and insect diversity, in particular,increases from beach to dune areas.

Generally, the richest beetle community was foundon the beach–dune system of Burano, where theenvironment was well preserved and where the beach–dune system presented the longest extension. Here, thevegetation cover of the dune was intact and highlydiverse due to the presence of the Mediterraneanmaquis. These conditions created a great number ofmicrohabitats that were exploited by a higher number ofspecies. In contrast, the beaches of Zouara and Ir-Ramla l-Hamra presented the lowest values of a, andthis was due to a greater uniformity of the environment.The beach–dune ecosystem of Zouara presented duneformations covered with cut pinewood to prevent eoliansand transportation and retrodunal areas with plantedAcacia trees. The absence of a typical Mediterraneanmaquis probably was the major cause of the low index

value. At Ir-Ramla l-Hamra, the causes were slightlydifferent. Here, the low diversity was probably due todisturbance factors on behalf of the continuous tram-pling of the beach by visitors and cars and by the dailycleaning of the beach–dune areas from litter and all thestranded organic debris. Surprisingly, Ir-Ramla tat-Torri presented the highest diversity values of thecoleopteran and isopod communities when comparedwith the other North African beaches. It is generallyknown that small pocket beaches are often impoverishedin species (McLachlan, 2001). In this specific case, thehigher diversity level found at Ir-Ramla tat-Torri wasprobably caused by the presence of another species nottypical of beach–dune systems. In fact, this beach,particularly degraded and heavily impacted duringsummer months, probably attracted, through non-removal of trash, a great number of inland species thatgenerally did not occur on beaches. The different resultsobtained by Deidun, Azzopardi, Saliba, and Schembri(2003) for the diversity of the Maltese beach wereprobably in relation to the different trapping design thatwas applied.

Another important trend indicated by the results wasthat species richness of coleopterans communities in-creased as the beach slope increased. This positivecorrelation was due to the fact that in Mediterraneanareas, with low tidal excursions and with relatively smallbeach widths, a higher beach slope is more favourablefor the establishment of pioneer vegetation. Hesp (1991)stated that in Mediterranean ecosystems, maximumplant species richness occurs where foredunes are morestable and these attract an associated faunal community.In the case of Burano, where beach slope was higher,a higher diversity value was found when compared withNorth African beaches that present dunes with a lowernumber of plant species (Hesp, 1991). Furthermore, it ishighly probable that other environmental parameters,such as latitude and beach length, are important forspecies richness over Mediterranean regions, but a largernumber of beaches must be analysed.

Comparing the evenness of the coleopteran commu-nity of the entire beach–dune system, Burano was thelocality in which the coleopteran species were mostuniformly distributed. The lowest value was insteadfound for Ir-Ramla l-Hamra, where few, very abundantspecies were found associated with many species with

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few individuals. This again can be due to the humandisturbance cause by beach cleaning.

Comparing the evenness of the coleopteran commu-nity in the two seasons for each locality, the highervalues found in autumn are in accordance with the lowerdominance values in this season. Furthermore, in all fivelocalities, a greater uniformity was obtained on the

Fig. 2. Renkonen’s percentage of similarity, between the different

localities, for coleopterans in the two seasons (a) and in the total (b)

and for the isopods in the two seasons (c) and in the total (d). Ss, Smir

in spring; Sa, Smir in autumn; Zs, Zouara in spring; Za, Zouara

in autumn; Ts, Ir-Ramla tat-Torri in spring; Ta, Ir-Ramla tat-Torri in

autumn; Hs, Ir-Ramla l-Hamra in spring; Ha, Ir-Ramla l-Hamra in

autumn; Bs, Burano in spring; Ba, Burano in autumn; S, Smir; Z,

Zouara; T, Ir-Ramla tat-Torri; H, Ir-Ramla l-Hamra; B, Burano.

dune, and, consequently, higher dominance indices werefound on the beach. In particular, the high dominanceindex found in spring on the beach at Smir was due toPhaleria acuminata, while at Zouara this was caused bythe massive presence of Phytosus nigriventris. Inautumn, in the latter locality, the higher dominancefound on the beach was instead due by the massivepresence of P. acuminata. At Ir-Ramla tat-Torri, thehigher dominance value on the beach, in April, was dueto Phaleria bimaculata, while in November, it was due tothe cryptophagid Cr1. On the dune in autumn, the latterspecies was present together with other three species(Ca16, Ca1 and Te21), and for this reason, the value ofthe index was lowered. At Ir-Ramla l-Hamra, thehighest value, obtained on the beach in both seasons,was again because of the great amount of P. acuminatasampled. At Burano, more dominant species were foundin autumn on the dune, where Psylliodes pallidipenniswas the most representative. In May, the higher value onthe beach was in relation to a great number of Anthicusfenestratus and Atheta amicula found in this area.

In accordance with the evenness values, Simpson’sdominance index was lowest at Burano, whereas atZouara, it reached its highest value. In the latter locality,Phytosus nigriventris was definitively a dominant speciesand prevailed over the others. At Ir-Ramla tat-Torri, anintermediate situation occurred, while at Ir-Ramlal-Hamra, even though the evenness of the communitywas found to be the lowest, the dominance index pre-sented an intermediate value between Ir-Ramla tat-Torriand Zouara. This was probably due to the fact that inthis locality, the majority of species were scarcelyrepresented.

For the isopod community, the high dominancevalues obtained on the beach were in relation to thepresence of Tylos europaeus, which mainly inhabited thisarea. Only for Ir-Ramla tat-Torri, the latter species wasnot found and an opposite tendency was obtained. Inthis case, Agabiformius obtusus was the dominant speciesof the dune and was captured mostly during springtime.The lowest dominance value obtained in April on thebeach was because of the presence of six isopod speciesthat were captured in this zone. At Ir-Ramla l-Hamra,in April, the higher dominance index found on the beachthan on the dune was related to the very high occurrenceof T. europaeus associated to a very low presence ofLeptotrichus panzerii on the beach and to the presence ofother three isopod species slightly more evenly distrib-uted on the dune. The maximum value obtained inNovember on both beach and dune was caused by thepresence of only T. europaeus. At Burano, the lowerdominance values found on the dune in autumn was alsodue to the presence of L. panzerii found associated withthe dominant species T. europaeus.

Thus, the evenness and dominance indices calculatedfor the isopod community were entirely in relation to the

102 I. Colombini et al. / Estuarine, Coastal and Shelf Science 58S (2003) 93–104

presence or absence of Tylos europaeus. At the sites,where this species was sampled, it was always dominantand typical of lower eulittoral areas. Consequently, thelocalities, with this species in common, showed similarspatial and temporal trends. The absence of T. euro-paeus at Ir-Ramla tat-Torri was in relation to severalconstraints, such as the presence of a quite superficialrocky platform underneath the beach surface thatprevented deep burrowing behaviour, very fine grainsands that generally are not preferred by this species(personal observations) and by human disturbance dueto the total removal of stranded beach wracks. At thissite, the overall isopod community was quite uniform,most of its species being evenly distributed both on thebeach and dune. Also, Deidun et al. (2003) reported theabsence of T. europaeus on all beaches of the MalteseIslands, except for Ir-Ramla l-Hamra, confirming ourresults.

Using Renkonen’s percentage similarity, the overallsimilarity of the coleopteran community between Smirand Ir-Ramla tat-Torri was principally due to thepresence of tenebrionids and, in particular, of Phaleriaacuminata that was an abundant species in bothlocalities. Contrarily, the lowest similarity found be-tween Burano and the two Maltese beaches was relatedto the fact that the faunal spectrum of Ir-Ramla tat-Torri and Ir-Ramla l-Hamra had only 16 and 11 speciesin common with Burano on a total of 112 and 119species captured, respectively. With a more detailedanalysis of the coleopteran community, the greatestsimilarity found between Smir in spring and Zouarain autumn was due to the numerical similarity ofP. acuminata and Phytosus nigriventris in these twoseasons. This was caused by the fact that P. acuminatadid not vary numerically in time, whereas P. nigriventris,extremely abundant at Zouara during springtime,reached Smir’s values only during autumn months.The presence of such a high quantity of P. nigriventris atZouara during spring was probably in relation to thedifferent quality of food cast ashore at the two sites.

The higher percentage of similarity found for most ofthe sites for the isopod community with respect to thecoleopteran community was related to the lower numberof isopod species compared with the coleopteran speciesand to the presences of Tylos europaeus that, where everpresent, was always the dominant species.

From this work, general patterns appear, bothtemporally and spatially, for faunal communities ofbeach–dune ecosystems of the Mediterranean basin.These trends have been summarised in Fig. 3.

4.1. From a temporal point of view (Fig. 3a)

For coleopteran and isopod communities, speciesrichness decreased from spring to autumn, and forcoleopterans, this decrease was associated with an

increase in the number of abundant species in autumn.In those beaches where isopods were mainly representedby Tylos europaeus, the number of abundant species wasequivalent in the two seasons, whereas in those beacheswhere T. europaeus was absent, the number of abundantspecies increased in autumn. For coleopterans andisopod communities without T. europaeus, capturenumbers decreased from spring to autumn, whereasan opposite trend occurred in those beaches whereT. europaeus was present. High numbers were generallyassociated with only few species. The a diversity for bothcoleopteran and isopod communities was higher inspring than in autumn. The evenness of coleopteransand isopod communities without T. europaeus wasgreater in autumn than in spring. Consequently, a higherdominance occurred in spring than in autumn. Beacheswhere T. europaeus was present, the evenness of thecommunity decreased from one season to the other, andthis was associated with equivalent dominance indices inthe two seasons.

4.2. From a spatial point of view (Fig. 3b)

For coleopterans and isopod communities with Tyloseuropaeus, species richness and the number of abundantspecies increased from the beach to the dune. For isopodcommunities without T. europaeus, an opposite trendoccurred for species richness, whereas a similar numberof abundant species was obtained in the two zones. Forcoleopterans and isopod communities with T. europaeus,capture numbers decreased from beach to dune areas,whereas the opposite occurred for isopod communitieswithout T. europaeus. The a diversity for both co-leopteran and isopod communities with T. europaeuswas higher on the dune than on the beach, whereas theopposite occurred for isopod communities withoutT. europaeus. The evenness of coleopterans and isopodcommunities with T. europaeus was greater on the dunethan on the beach. Equivalent values of evenness wereobtained for isopod communities without T. europaeus.Consequently, higher dominance values were found onthe beach than on the dune in all cases, except for isopodcommunities without T. europaeus.

Even though general trends for beach–dune systemsover the Mediterranean could be found, the resultsindicate that the community structure of the fauna at thedifferent sites largely depended on the local beachfeatures (vegetation, slope, exposure, human impactetc.). Isopod communities without Tylos europaeusshowed trends similar to coleopterans when analysedseasonally, whereas isopod communities with T. euro-paeus presented similarities with coleopterans whenanalysed spatially. This means that the presence of thisparticular species influences the community structure ofisopods, both temporally and spatially. The absence ofT. europaeus on beach ecosystems is a quite rare

103I. Colombini et al. / Estuarine, Coastal and Shelf Science 58S (2003) 93–104

Fig. 3. General patterns, both temporally (a) and spatially (b), for faunal communities of beach–dune ecosystems of the Mediterranean basin.

Decreasing, increasing and equivalent values from one season or zone to the other are shown for coleopterans and isopods in localities with and

without Tylos europaeus.

phenomenon in the Mediterranean and seems to beassociated not only with physical constraints, but alsowith human disturbance.

This work provides baseline information for futuremonitoring of impacts. The ecological indices applied onthe two different classes (isopods and coleopterans)substantially showed that both classes were goodindicators of beach state. In fact, the presence of typicalspecies (namely Tylos europaeus, Phaleria spp., Euryne-bria complanata, Erodius spp. etc.) or their absenceassociated with the invasion of non-specific species (e.g.Ir-Ramla tat-Torri) indicated the quality of the envi-ronment. However, beach ecosystems being highlydynamic and continuously changing over space andtime, these indices become useful only if data arecollected according to a certain criterion (standard

techniques) and analysed in space and time. Only withthis new perspective will the understanding of beachecosystem be enhanced and more realistic.

Acknowledgements

This research was funded by the European Commu-nity within INCO-DC IV programmes (MECO ProjectERB IC-18-CT98-0270) and by the Istituto per lo Studiodegli Ecosistemi of CNR of Florence. The studiesconducted in the five localities comply with the currentlaws of the different countries. We would like to thankthe local Authorities and the partner Universities inTunisia, Morocco and Malta for their assistance, andDr Stefano Taiti who identified the isopod species.

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