For example, a spatially explicit neutral model has shown that disturbance increases time to extinction and can delay (or prevent) mono-dominance ( Gardner & Engelhardt 2008). More recently, neutral models ( sensu Bell 2000 Hubbell 2001) have also begun to be used to assess the ecological effects of disturbance. A complete review of disturbance in ecological theory is beyond the scope of this paper, but some examples include: patch dynamics models ( Shugart & Seagle 1985 White & Pickett 1985), fluctuation-mediated coexistence ( Chesson & Warner 1981) and life-history trade-offs ( Tilman 1994). Therefore, in this paper, I compare effects of different ecological disturbances for biodiversity (see below under definition of disturbance).ĭisturbance has since become a prevalent feature in ecological theory. These inconsistent results may be partly driven by the variety of events that are included under the umbrella of disturbance, and their differences in ecological consequences. Numerous studies have empirically validated this hypothesis, however, a meta-analysis revealed that conflicting and non significant patterns are common ( Mackey & Currie 2001). This unimodal relationship between species richness and disturbance has become an ecological paradigm ( Wilkinson 1999). This hypothesis proposes that species richness should be maximized under intermediate levels of disturbance because at low levels of disturbance superior competitor species monopolize resources and exclude other species, whereas at high disturbance levels only the most resistant species survive. The progressive realization of the roles of grazing and predation on delaying competitive exclusion led to the formulation of the intermediate disturbance hypothesis ( Grime 1973 Connell 1978). The importance of disturbance in this context is that it leads to secondary succession and sometimes prevents communities from reaching their climax state. Early views focused on succession, which took communities from the colonization of barren space by pioneer species, to highly complex and diverse climax communities ( Clements 1916). Developing general guidelines to predict when and how biodiversity patterns should change following a disturbance is a crucial matter for this purpose.įrom a historical perspective, disturbance has long been present in ecological theory. This large body of literature is largely fuelled by the need to quantify effects of disturbance (typically of anthropogenic nature) on communities, in order to guide conservation efforts and the management of ecological resources. A search in web-of-science with keywords diversity and disturbance finds over 6500 publications. The types of disturbance involved include everything from single tree-falls ( Brokaw 1985) to ecological catastrophes ( Hughes 1994). ![]() 2009) and ecosystem functioning ( Hotes et al. 2007) to primates ( Bicknell & Peres 2010) and at multiple levels of organization including molecular pathways ( Spagnuolo et al. 2009), a range of organisms extending from bacteria ( Binh et al. Effects of disturbance on biodiversity have been studied in a great variety of ecosystems ranging from tundra communities ( Jorgenson et al. The role of disturbance in shaping biodiversity is widely recognized. Importantly, regardless of disturbance type, community isolation enhances the negative consequences and hinders the positive effects of disturbances. Consequences of composite DBK disturbances are more complex than any of the three types of disturbance, with unimodal relationships along a disturbance gradient arising when D, B and K are negatively correlated. K disturbance has the most severe effects, followed by D disturbance, and B disturbance has nearly negligible effects. The patterns of change in biodiversity metrics are consistent among different types of disturbance. I use simulations of neutral communities and examine species richness, total abundance and species abundance distributions. ![]() The consequences of D, B and K disturbances, as well as of composite DBK disturbances are examined by comparing metrics before and after a disturbance, in disturbed and undisturbed communities. Numerous composite disturbances can be defined including any combination of these three types of ecological effects. I define three main types of disturbance effects: D disturbance (shifts in mortality rate), B disturbance (shifts in reproductive rates) and K disturbance (shifts in carrying capacity). Here, I investigate how disturbances with different ecological effects change biodiversity metrics. ![]() Understanding how disturbance affects biodiversity is important for both fundamental and applied reasons.
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