Βιογεωγραφία και στοιχεία οικολογίας των εδαφικών κολεόπτερων σε βουνά της Πελοποννήσου

Abstract

This dissertation concerns the study of the response of edaphic coleopteran communities (familiesCarabidae and Tenebrionidae) to changes of abiotic and biotic parameters that are produced along changes inaltitude. The study was carried out in 5 representative mountains of the Peloponnese, namely Chelmos,Erymanthos, Mainalo, Parnonas and Taygetos. Each one of these has a different geographic position withinthe Peloponnese. Three vegetational zones are evident in these mountains according to altitude:Mediterranean-type, forest and subalpine. They form three altitudinal classes that are related to the effect ofthe various biotic parameters. Carabidae and Tenebrionidae are ideal organisms for such studies that arecarried out along environmental gradients. They show significant differences in dispersal ability as well as indietary preferences.Sampling took place in 3 consecutive years in Chelmos, 2 in Mainalo and 1 in the remainingmountains. A total of 22 sampling stations were surveyed using pitfall traps in three linear transects thatbelonged to 7 different types of biotope (subalpine, fir forests, mixed coniferous forests, pine forests,deciduous forests, maquis and phrygana). The traps were changed every season, while at the same time, soilrelative humidity and pH were measured. Sorting of Carabidae and Tenebrionidae was carried out in thelaboratory, and it was followed by identification at the species level using appropriate literature andidentification keys. In total, 82 species of Carabidae and 41 species of Tenebrionidae were identified. All the specimens of Carabidae and Tenebrionidae that were collected and identified, were counted, and the contentsof each trap were transformed to number of individuals per 100 trap-days and to a scale of log10(x+1).In order to study the effect of the type of biotope and the different linear transects on the abundanceof individuals and species richness, Nested Design Analysis of Variance, Variance Components Analysis andone way ANOVA were used. In order to study the differences between the abundance and the varioussampling stations, we used NMDS using the Bray-Curtis index of similarity, and PCA. In order to check thesignificance of the differences in the structure of the assemblages of edaphic Coleoptera that came out ofNMDS, we used ANOSIM, while the linear regression was used to correlate the environmental factors thatwere measured in the study areas with the environmental gradient that was produced from the values of thePCA axes. Finally, in order to estimate the effect of each environmental variable, including geographicalparameters, on the structure and composition of the communities of edaphic Coleoptera, we used the CCA.The gradient of climatic conditions in conjunction with the ecological parameters that are producedby the composition and the structure of the vegetation, are the main factors that affect the distribution ofspecies along the altitudinal gradients. However, the way that they affect abundance, richness, and thecomposition and structure of communities differs from group to group as a result of the interaction of theenvironmental parameters with the ecological requirements and with the natural history of the group under study. In the subalpine areas, a high diversity of species and a high abundance of individuals wereobserved, both for Tenebrionidae and for Carabidae, and especially for herbivore species. Temperature,humidity and soil pH are the most important factors that influence their distribution. The combination of lowtemperatures and increase of rainfall and snow along the altitudinal gradients, affects the composition andstructure of vegetation, the diversity of plant species and the primary productivity at the soil level. Thediversity of plant species, the increased primary productivity at the soil level and the spatial heterogeneity inresource distribution, influence initially, in a positive manner, the diversity and abundance of herbivorousspecies (through the diversity of food) and consequently the predators, through a variety of trophicrelationships that develop in the food webs of the ecosystems. At the same time, the presence ofmicrohabitats and refuges allows the organisms to avoid the unfavourable conditions such as ultravioletradiation, desiccation and wind intensity.In the middle altitudinal class, the microclimate of forests is shady, more cold and wet than that ofthe open areas such as meadows, maquis and phrygana, while the soil pH has acidic values. These factorshave affected the members of the two groups in a different way, and this difference is related to the differenttrophic preferences and ecological requirements. The characteristic species of forest Carabidae prefer highhumidity values in relation to the species of the Mediterranean-type ecosystems that prefer dry habitats. Thecarnivorous Carabidae, although having a positive relationship with pH, in this study, showed high abundances, and their communities form a significant component of forest soil fauna. Forests, having a“three-dimensional structure”, consist of ecosystems that are characterized by high productivity, however,the plant cover as well as the productivity on ground level are much less. The carnivorous Carabidae aregeneralized predators and contribute to the saprobiotic food chains of forest ecosystems. The herbivores havefew representatives in forest ecosystems and have low abundances. The acid values of pH, the low primaryproductivity and the presences of resins in coniferous forests are the main factors that limit abundances andspecies richness of their species. The same factors have affected negatively the presence and abundance ofTenebrionidae species, which are mostly characteristic of open and dry areas.In the ecosystems of the low altitudinal zones, in maquis and especially in phygana, the high valuesof temperature and aridity have significantly differentiated the assemblages of both groups compared to theforest and subalpine areas. Many thermophilous and xerophilous species of Tenebrionidae were limited tothese formations and have produced high abundances. In Carabidae, the presence of young grasses hasincreased the percentage of herbivore species, as in the open subalpine areas. Their ability to modify theseasonal and daily phenology in order to find favourable conditions of humidity and temperature, and toexploit refuges that are offered by the vegetation in order to avoid high temperatures and aridity, have allowed the Carabidae communities to play a significant role in the function of Mediterranean-typeformations.The ordination methods have shown that the main factors that affect the structure and composition ofthe Carabidae and Tenebrionidae communities are altitude and the basic structure of vegetation, i.e. forest vs.open. Species with a low tolerance for gradients of environmental parameters that arise from the various types of biotopes and altitudes, limit their distribution to specific biotopes or altitudes and are replaced byothers, therefore, changing the composition and structure of assemblages along the altitudinal gradients ofthe five mountains. The most important factors are the variation in air temperature and relative humidity , aswell as the parameters that arise from the structure and composition of vegetation such as shade, pH and therelative humidity of soil. Within each altitudinal class, the largest differences were observed between theforests. The composition of the forest species of trees and especially of pines that produce resins, the valuesof pH and the gradient of soil humidity from north to south, are the main factors that affect the compositionand the structure of forest communities. Even species with increased tolerance to the variation ofenvironmental variables which are produced as we go higher, allowing them to expand widely and increasethe percentage of overlap between assemblages in different altitudes and different types of biotopes, differedin their abundances, showing a preference for specific types of biotope and altitudes.The range of species distributions is determined by their tolerance to the variation of environmentalparameters and to the flexibility and adaptability to the exploitation of resources. The trophic ecology of thespecies was an important parameter for the differentiation between the various types of biotopes and therange of altitudinal gradients where the study took place. The carnivorous Carabidae showed the highestoverlap between the composition of their communities, both among different altitudes and different types ofbiotopes. The majority were brachypterous species with a limited capacity for flight in comparison with the herbivorous species of this family that usually have functional wings. However, the limited ability fordispersal within the narrow geographical scale of this study is compensated by the higher ability ofsettlement in different types of biotopes because of their ability to exploit a larger variety of food resources,since they participate in both plant and saprobiotic food webs. On the contrary, the herbivorous Carabidaeand Tenebrionidae have shown a larger degree of dependence from certain plants or vegetation types, as wellas a bigger sensitivity to parameters that are related to the type of vegetation, such as pH and the presence ofresins. As a result, their distribution is limited to a large degree, to specific altitudes or type of biotope.The limited dispersal ability of carnivorous Carabidae resulted in the presence of a large number oflocal endemic species as opposed to the herbivorous species. The endemism of a region or a type of biotopedepends on the degree of isolation which is related to the dispersal ability of the species under study. Theherbivorous Carabidae have not exhibited high levels of endemism because of their high dispersal ability andtheir ability to colonize unstable environments that are in the first stage of ecological succession, in relationto the mild climate of subalpine areas and the relatively low altitude. The highest percentages of endemismwere observed in the carnivorous Carabidae of the middle and high altitudinal class. However, although thedegree of isolation increases with altitude, the presence of endemic species especially at the level of abundance, is higher in forest formations of the middle altitudinal class. This is related to the stability of thehabitat that favours brachyptery and increases the level of isolation of forest biotopes.