Projects / Programmes source: ARRS

Impact of multispecies interactions on the structure of assemblages in ecosystems

Research activity

Code Science Field Subfield
1.03.03  Natural sciences and mathematics  Biology  Ecosystems 

Code Science Field
B280  Biomedical sciences  Animal ecology 
interspecific interactions, competition, predation, indirect interactions, assemblage, ecosystem, predator guild, ecological experiment, ornithology, entomology, speleobiology
Evaluation (rules)
source: COBISS
Researchers (1)
no. Code Name and surname Research area Role Period No. of publications
1.  21502  PhD Al Vrezec  Biology  Principal Researcher  2007 - 2008  1,001 
Organisations (1)
no. Code Research organisation City Registration number No. of publications
1.  0105  National Institute of Biology  Ljubljana  5055784  13,222 
One of the basic elements in natural assemblage structuring, species composition and abundance of species are interspecific interactions. These are fundamental in the studies of function and structure of ecosystems, which are research priorities of the 6th EU Framework Programme. Some recent studies have shown great impact of indirect interspecific interactions on the structure of assemblages in ecosystems. In some cases indirect interactions are even more important than direct one since they lead into a complete exclusion of species from the system. The main goal of these studies was assessing negative indirect interactions, especially between species from different trophic levels. On the other hand, positive indirect interactions are poorly known and they were even not experimentally proved yet. The proposed postdoc research project is dealing with a broad approach in the study of direct and indirect interspecific interactions in predator assemblages. The structure of predator assemblages is particularly influenced by negative interspecific interactions, which can even result in competitive exclusion between species. According to our preliminary studies positive indirect interactions influence the structure of predator assemblages as well. These are mainly a result of a synergistic complex of several negative direct interactions. In the research proposal three kinds of methodological approaches are planned: (1) comparative ecological study of forest owls (Strigidae) predator guild, (2) experimental study of artificial diving beetles (Dytiscidae) predator guild, and (3) the analysis of predator guilds in natural ecosystems in the case of cave carabid beetles (Carabidae), where expression of the interaction patterns and mechanisms in assemblage structuring of size-structured predator guilds will be tested. In the proposal we set up the relevance of the study, which opens a completely new field of positive indirect interactions in ecological science. The results will be also an important contribution in entomological and speleobiological science. The application of research results is possible particularly in preservation of ecosystems and biodiversity, and in management of the sustainable use of natural especially biotic resources.
Significance for science
Within the concluded project we described the first positive indirect interaction found within a top predator community in the relationship between Ural and Tengmalm’s Owl. The interaction fits well the concept of protective mutualisms in which one species shields the other from the effects of natural enemies or competitors. This indirect interaction can thus be regarded only in the context of a two-species association with the third, which acts as mediator species. In top predators, protective mutualisms have been described in cases of nest defence effect, when the breeding success of a species from lower trophic level is increased in the immediate vicinity of a top predator nest. In the present case a positive effect results from the interspecific territory defence of the Ural Owl against Tawny Owl, and is restricted just to the species of the same predator guild, what is new in the studies of indirect interspecific interactions. To confirm indirect positive interactions in predator guilds as a general ecological phenomena we have additionally found the evidences in other predator assemblages, e.g. in water beetles (Dytiscidae), where abundance relationship between larger and smaller predators is turned from negative in low diversity assemblages to positive in high diversity assemblages. Our study supports the idea in which multispecies mutualisms that modify competitive environment play a critical role in determining species diversity at the community level. We have shown that such interactions are not important only on the intertrophic level as indirect interaction between two prey species with common predator or parasite, but acts also on the intratrophic level and even within the same guild. The research is in the scope of studies of structure and function of ecosystems and its results will be important for implementation in modelling for processes with predator assemblages and for identification of so called key species which have essential importance in structuring of natural assemblages and consequently on stability of the given ecosystems. Questions that have been opened with this study are focused in mechanisms that support multispecies mutualisms in predator guilds. If between owl species this mechanism appeared to be interspecific territoriality, it is not clear what kind of mechanism acts in other predator assemblages. For predator guild of water beetles we partly answered this question with laboratory experiment, where chemical interspecific repulsion seemed to play an important role. However, this issue are in need to be investigated in future studies.
Significance for the country
In Slovenia two out three selected predator guilds, forest owls and cave carabid beetles, are of great conservation importance. As top predators owls are important indicator of ecological condition of forest ecosystems, and two discussed species are even species of international conservation importance listed in European Union Bird Directive (Council Directive 79/409/EEC). We have shown the importance of the need of overall conservation of predator assemblages and indirectly pointed out consequences if the largest predator in the guild became extinct, in our case the Ural Owl. With systematically collected field data of this project we got better view on spatial distribution of species of conservation importance in Slovenia and can be used in supplementing current groundwork for Natura 2000 network with missing quantified population data. On the other hand the cave carabid beetles are extremely important part of Slovenian biodiversity due to the large number of endemic species, what gives Slovenian natural heritage a global importance. Collected population and faunistic data can be directly used in conservation activities for these species. Currently in Slovenia most of speleobiological studies are focused on freshwater ecosystems and less in ecology of terrestrial subterranean ecosystems part of which are also cave carabid beetles. Also when considering overall the entomological studies in Slovenia the majority of studies are focused on taxonomy, faunistic, biogeography, bioacoustics, physiology and cenology, and less in ecology including interspecific interactions, population biology, habitat selection etc., which were topic of this project. Therefore the contribution of this study is in development of insect ecology in Slovenia with special focus given on quantification of insect populations. The insect conservation in Slovenia, especially in the case of subterranean beetles, is set only arbitrary since ecological characteristics and potential threat parameters are not known. Conservation guidelines are therefore insufficient. Since one of the aims of this project was to collect data on ecological characteristics of cave carabid beetles, e.g. habitat parameters, we supposed that this data will be an important background for development of effective conservation measures for conservation of this important part of Slovenian biodiversity.
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