Ecological Modelling

We constructed empirical model that combine together the data about species richness, indices saprobity S and DAIpo with information Shannon index of more than 2,500 algal and cyanobacteria communities from diverse water bodies in Eurasia on the base of our large experience and available references. The fields of the data points in coordinates of Index Saprobity and Index Shannon, and Index Saprobity and Species richness in the model are represent the major succession trends with the trophic base increasing. We define the community parameters that reflect natural undisturbed community, self-purified ecosystem range of variables as well as critical parameters up to variables in which the ecosystem can collapsed. The main successional stages in the model coincided with the self-purification zones. Empirical model can be used as a prognostic instrument for the large period for any aquatic ecosystem. It makes possible to work on assessing the state of any possible within the parameters in which the aquatic ecosystem can exist and predict its development.

Studies of complex networks show that nodes with high centrality scores are important to network structure and stability. Following this rationale, centrality measures can be used to (i) identify keystone species in ecological networks, a major issue in community ecology, and (ii) differentiate the keystone
species concept, e.g. species may play a key role in a network for different topological reasons. In 34 pollination communities we examine the relationship between the generalization level of species (ND) and two complementary centrality indices: closeness (CC) and betweenness centrality (BC). CC measures the proximity of a species to all other species in the community, while BC describes the importance of a species as a connector. Most networks had a linear ND–CC relationship with a minimum CC value of 0.41.
Hence, species were close to each and will be likely to be rapidly affected by disturbances. Contrarily, in most networks, the ND–BC relationships were power-law distributed with exponents larger than one. Only 59% of the species were connectors (BC > 0). In particular, there was a connector threshold value of ND = 0.46. Species above this threshold represent 40%, almost all of which were connectors. These results indicate that in pollination systems the most generalized species are usually network keystone species, playing at least two roles: (i) interact closely with most other species (high CC) and (ii) connect otherwise unconnected subnetworks (high BC). We discuss the implications of centrality measures to community-based conservation ecology.