Patterns and processes
In the given setup of abiotic conditions of a biotope species interactions between same (intraspecific) and different (interspecific) species are important drivers for biodiversity, as activity of any organisms affects the environment in which it lives. Within such a dynamic environment interactions like competition, predation, parasitism, mutualism, and detritivory moulding the composition of communities and populations take place.
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Biological systems are never static. Species continuously evolve due to mutation and complex interactions of selection and genetic drift. Genetic variation that is continuously passed on and mixed within populations by sexual reproduction is the raw material for microevolution, e.g. due to altered selection regimes like climate change. Evolution may also involve hybridization of previously separated species or populations, e.g. after introduction of alien species, or introgression of genes from crops into native species.
Species show a specific spatial pattern of occurrence, their range. This range is usually delimited by specific environmental (biotic and abiotic) parameters. Furthermore, not only species are characterised by a range but certain traits respond to specific environmental filters and hence vary in their composition. To better understand the relationships between both traits and species, we model their response to the environment. This is a prerequisite to asses impacts of climate change, land-use change or biological invasions on species and communities but also for developing adaptation and mitigation measures buffering against these pressures.
In ecology disturbance is a temporary change from average conditions, often resulting in the removal of large amounts of biomass. Disturbance events like fires, floodings, windstorms or insect outbreaks vary in spatial and temporal scales and cause pronounced changes in ecosystems, communities and populations. Disturbances generate conditions that favour the success of certain species and therefore facilitate the formation of specific ecosystems and communities. These communities may exist for much longer periods than the time span of the actual disturbance. However, without recurrent disturbances communities will develop back toward pre-disturbance conditions (succession). Overall a mosaic of communities at different successional stages facilitates high levels of biodiversity.
The success of certain species is closely linked to disturbances. For example, many shade-intolerant plant species rely on disturbances (e.g. removal of trees) for successful establishment. However, very view species are able to tolerate intense disturbance regimes. The intermeditate disturbance hypothesis suggests that diversity is highest when disturbances are neither too rare nor too frequent. With low disturbance, competitive exclusion by the dominant species decreases species richness, whereas with intense disturbance regimes, only species tolerant stress persist.