| Abstract |
The similarity between areas with dominant maquis vegetation in limestone substrate in eastern Mediterranean is remarkable. Thus, it is almost impossible to detect any difference between areas in continental Greece, islands of the Aegean, Cyprus, Middle East and Cyrenaika. Nevertheless, it still remains unknown if this identical picture is reflected to the faunal element of these areas.
Seeking an answer to the above question, the study group chosen was Coleoptera, the largest Order of insects and arthropods on Earth. Specifically, the families Carabidae and Tenebrionidae were studied, due to their dominance in Mediterranean-type ecosystems on the basis of biodiversity, abundance and biomass.
The aim of the study was to compare a specific ecosystem type in five areas of eastern Mediterranean through the Order of Coleoptera. The parameters of comparison which were analyzed were:
-The structure of the coleopteran fauna (families Carabidae and Tenebrionidae) in relation to the biogeography of species and the level of similarity of the study areas in relation ton their faunal element.
-The phenology of the two families and their species and the exploration of the patterns and the differences between them in relation to measured abiotic factors.
- The species richness of the families Carabidae and Tenebrionidae in the five study areas.
-The analysis of the community ecology of the two study groups and their species in space (between areas and microhabitat types in each area) and in time.
The study was made in five areas in eastern Mediterranean, which had in common the similarity and uniformity of vegetation, Juniperus phoenicea and Pistacia lentiscus being the dominant plant species, the same geological substrate (limestone), and topographic characteristics (e.g. altitude, slope). The areas were chosen so as to include the majority of the particularities of the palaeogeographic history of eastern Mediterranean. The study areas were:
- Agia Marina in eastern Attiki, which was always a continental area in the south part of the Balkan peninsula,
- Moutsouna in eastern Naxos, the largest island of the Cyclades in the central of Aegean archipelago with relatively old isolation,
- Psili Ammos in SE Samos, the closest island to Asia Minor which was recently separated from the Anatolian peninsula,
- Pacheia Ammos in eastern Crete, the largest island in the Aegean with very old isolation,
- Kourio in south Cyprus, an oceanic island, in contrast with the aforementioned three (islands), at the eastern edge of the Mediterranean.
The study lasted two years (May 2006-May 2008) and the pitfall trap method was used, the most commonly used method in ecological studies concerning arthropod diversity and abundance. Twenty pitfall traps were set in each study site with a 10m inter-trap distance in an arrangement of one single transect during the first year and three separate transects during the second sampling year, at a minimum distance of 50m between two of the three transects. The traps were placed in the centre of the maquis formations. Samples were collected bimonthly and abiotic measurements were made during the whole study (air temperature, air relative humidity, precipitation). The taxonomic separation of the samples per order and the identification of Carabidae and Tenebrionidae on species-level were made in the Arthopoda lab of the Natural History Museum of Crete, where most of the material is deposited. A small part is deposited to the Natural History Museum of Sofia in Bulgaria.
In total, 16 genera and 32 species of Carabidae were identified (12 new records for science; 10 for Samos, two for Naxos), as well as 20 genera and 31 species of Tenebrionidae (one new record for Naxos). The great level of difference in the taxonomic synthesis of the five communities for both families was expected, in relation to the distribution of the captured species, the representation of most genera by a single species and the high level of endemism of Tenebrionidae in the eastern Mediterranean.
On a biogeographic view, based on the chorotypes of the species, the Balkan element is mainly present in Attiki and Naxos, due to the connections of Naxos with continental Greece until late Pleitocene. The Anatolian element is mainly present in Samos, which was a part of the Anatolian peninsula during the late Pleistocene. The high percentages of endemism recorded in Crete were a result of the old isolation of the island from continental Greece to the west and Anatolia to the east. However, the presence of the Syro-Palaestinian and the Anatolian element in Cyprus is of great interest in relation to the palaeogeographic history of the island and the possibility of connections with the Levant or Anatolia, which have not been affirmed till today.
The transitional nature of the maquis habitats proved limitative for the species richness of Coleoptera. Tenebrionidae and Carabidae immmigrate from more xeric phryganic habitats to these habitats, when the climatic conditions become disturbing. The highest species richness was recorded in areas where abundance was the lowest (Carabidae: Cyprus, Tenebrionidae: Crete). The different responses of the two families to the abiotic factors prove that high species richness is not correlated to high air temperature, at least for Carabidae in all sites and Tenebrionidae in Crete, although it has been reported for both families.
The populations of Carabidae in Cyprus and Tenebrionidae in Crete are probably relict, because the structural differences compared to the rest indicate a different level of environmental pressure. The low precipitation in Cyprus and the phytochemical inhibition of Tenebrionidae from the differentiated Juniperus phoenicea in Crete are probably the main reasons of the impressively low abundance of Tenebrionidae in the aforementioned study sites.
The temporal turnover of species during the study varied between the study sites. It was low in the communities with a single dominant species with very high abundance and sharp phenology (Carabidae: Cyprus, Naxos, Samos; Tenebrionidae: Naxos, Samos), thus, highlighting the importance of relative abundance and periods of peak activity. The high temporal heterogeneity [high temporal β diversity (βt))] of both families and especially Tenebrionidae was not due to temporal variability in species composition, but the result of a well established community adapted to temporally changing Mediterranean conditions (drastic seasonality).
The sharp phenological patterns of Tenebrionidae in all study sites, with periods of peak abundance during late spring and early summer, are coincide with the primary productivity and specifically the period of litter fall of sclerophylle evergreen shrubs, such as Juniperus phoenicea, in Mediterranean-type ecosystems. On the contrary, phenological patterns of Carabidae were vaguer or even statistically not significant (Naxos), while the phenologies of Carabidae in Crete and Cyprus were statistically different from the respective phenologies in the other three sites.
The communities of the two families proved to have a random structure, except those of Carabidae in Attiki and Tenebrionidae in Cyprus (segregated pattern) and the community of Carabidae in Naxos (weak aggregated pattern). Non-random resource partition within the first two communities was proved by the constant body size ratio of the co-dominant species (four and three respectively) and the slight temporal differentiation of their phenologies. The microhabitat differentiation of the four dominant species of Carabidae in Attiki indicates the presence of competition, which is expected in a continental area, and specifically “diffuse competition”, due to the
intermediate species richness. The latter was not found for Tenebrionidae in Cyprus, and is very rare for saprophagus animals. The different strategies between large and small sized species Carabidae in Attiki was evident from the high slope in the Abundance-Weight Relation (AWR) and the statistical significance of the equation Abundance= a(Biomass)b , which was found only for the specific community.
The analyses with models based on abundance led to a pluralistic explanation of the abundances of Coleoptera. The interspecific relations or/and the responses of species to the changing environmental conditions are regulated by stochastic and deterministic processes, which interact to determine community assembly of Carabidae and Tenebrionidae. The deterministic patterns mainly depend on the spatial and temporal differentiation of the species of each community, while the stochastic patterns mainly depend on the distribution of their relative abundance.
The modified Lorenz curves (plot of cumulative abundance and cumulative body size) were concave for Carabidae in Crete and Cyprus, indicating the dominance of the smaller species, in contrast with the communities of Carabidae in the other three sites (convex curves). The pattern of the curves for the sites in Crete and Cyprus is similar to that in areas with high level of disturbance and degradation, such as communities in urban areas. This is the first case of such a revealed pattern in a natural ecosystem. On the contrary, the pattern for Tenebrionidae was convex curves for the communities in Crete and Cyprus. Though, it is probably the same response, because the most abundant Tenebrionidae species in natural ecosystems are the r-selected. The low abundance of Tenebrionidae in Crete and Carabidae in Cyprus, the relatively low abundance of Carabidae in Crete and the segregated pattern of the assemblies of Tenebrionidae (possible competition) in Cyprus are strong indications of a differential environmental pressure in these two sites, and probably higher compared to the other three study areas.
The synthesis of the communities is a result of historical procedures, with regard to the dispersal of species and the complex palaegeographic events in the eastern Mediterranean. Specifically, many of the captured Carabidae species are relict and probably are subject to the taxon pulse, and undergo a period of “contraction” of their distribution in the eastern Mediterranean region. Nevertheless, the temporal heterogeneity of biodiversity, the statistically different response of congeneric or even the same species to similar abiotic measurements and the structural differentiation of the communities in Crete and Cyprus are proof of the different level of environmental pressure and the adaptation to local conditions. The same goes for the distribution of body size of the species in relation to the respective distribution of their abundances in the communities. Consequently, the dynamics of the relation within local assemblages in relation to the variability of environmental conditions in the eastern Mediterranean, the available microhabitats and the level of environmental pressure are controlling factors of the structure of the communities.
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