Biodiversity and ecosystem function: the consumer connection

Abstract

Minireviews provides an opportunity to summarize existing knowledge of selected ecological areas, with special emphasis on current topics where rapid and significant advances are occurring. Reviews should be concise and not too wide-ranging. All key references should be cited. A summary is required. Proposed links between biodiversity and ecosystem processes have generated intense interest and controversy in recent years. With few exceptions, however, empirical studies have focused on grassland plants and laboratory aquatic microbial systems, whereas there has been little attention to how changing animal diversity may influence ecosystem processes. Meanwhile, a separate research tradition has demonstrated strong top-down forcing in many systems, but has considered the role of diversity in these processes only tangentially. Integration of these research directions is necessary for more complete understanding in both areas. Several considerations suggest that changing diversity in multi-level food webs can have important ecosystem effects that can be qualitatively different than those mediated by plants. First, extinctions tend to be biased by trophic level: higher-level consumers are less diverse, less abundant, and under stronger anthropogenic pressure on average than wild plants, and thus face greater risk of extinction. Second, unlike plants, consumers often have impacts on ecosystems disproportionate to their abundance. Thus, an early consequence of declining diversity will often be skewed trophic structure, potentially reducing top-down influence. Third, where predators remain abundant, declining diversity at lower trophic levels may change effectiveness of predation and penetrance of trophic cascades by reducing trait diversity and the potential for compensation among species within a level. The mostly indirect evidence available provides some support for this prediction. Yet effects of changing animal diversity on functional processes have rarely been tested experimentally. Evaluating impacts of biodiversity loss on ecosystem function requires expanding the scope of current experimental research to multi-level food webs. A central challenge to doing so, and to evaluating the importance of trophic cascades specifically, is understanding the distribution of interaction strengths within natural communities and how they change with community composition. Although topology of most real food webs is extremely complex, it is not at all clear how much of this complexity translates to strong dynamic linkages that influence aggregate biomass and community composition. Finally, there is a need for more detailed data on patterns of species loss from real ecosystems (community ''disassembly'' rules). MINI-REVIEW

Does urbanization explain differences in interactions between an insect herbivore and its natural enemies and mutualists?

“…Urban management techniques such as treading, bird feeding, mowing and pesticide application negatively impact predacious beetles and hemipterans (Morris and Rispin 1987;Helden and Leather 2004;Orros and Fellowes 2012;Jones and Leather 2012;Orros et al 2015;Bennett and Lovell 2014;Smith et al 2015). Human-induced extinctions and local extirpations are often biased towards higher trophic levels (Pauly et al 1998;Jackson et al 2001;Duffy 2002;Byrnes et al 2005), and that losses of even one or two species that belong to higher trophic levels can cause cascading effects on species present on basal trophic levels (Paine 2002;Schmitz 2003) and critically affect ecosystem processes (Tilman et al 1997;Byrnes et al 2005;Hooper et al 2005).…”

Human transformations of the Wadden Sea ecosystem through time: a synthesis

“…4;van den Hoek et al 1979;Asmus et al 1998). Reduced functional diversity and the loss of higher trophic levels result in reduced niche use, reduced efficiency of energy use and transfer, higher leakage, and as a consequence reduced secondary productivity and biomass (Duffy 2002). Two studies have illustrated the reduction of upper trophic level biomass for the North Sea and North Atlantic.…”

Biodiversity and Resilience of Ecosystem Functions

“…An analogy of this situation is the difference between monitoring 63 whether a bridge is either standing (i.e. providing its function) or collapsed, prompting need 64 for a re-build, as opposed to monitoring and repairing damage to prevent the collapse from 65 ever happening. In environmental science, attempts have been made to identify this 'safe 66 operating space' at a global level to ensure that boundaries are not crossed that could lead 67 to rapid losses in ecosystem functions [10,11].…”