Forschung

The body-size structure of natural food webs

Some key characteristics of natural ecosystems:


     (a) predators are on average larger than their prey ^1,2,

     (b) predator size and the mean size of their prey are positively correlated ^1,2 ,

     (c) predator size increases with trophic level ² ,

     (d) predator-prey body-mass ratios (body size of the predator divided by the

            average body size of the prey) decrease with trophic levels ² , and

     (e) with increasing body size of a species its generality (the number of links to prey)

            increases and its vulnerability (the number of links to predators) decreases ^3,4 .


These body-size characteristics provide the dynamic stability that is necessary to maintain the diversity and functioning of natural ecosystems ^3,5-10 .

Feeding interactions from a terrestrial food web. Nodes display populations, sticks display interactions. Image produced with FoodWeb3D, written by R.J. Williams and provided by the Pacific Ecoinformatics and Computational Ecology Lab (www.foodwebs.org, Yoon et al. 2004).

Current projects:

One striking finding of these projects is the general lack of highly resolved terrestrial belowground food webs. Aiming to fill this void, we have started several projects addressing the structure and dynamics of decomposer food webs of forest floor communities (under the DFG priority program “Biodiversity Exploratories”), agricultural fields (DFG research unit “Carbon flow in belowground food webs assessed by isotope tracers”), and tropical rainforests or plantations (DFG CRC Ecological and Socioeconomic Functions of Tropical Lowland Rainforest Transformation Systems (Sumatra, Indonesia)).

References for further reading (see publications section):

(1) Brose et al. 2006, Ecology

(2) Riede et al. 2011, Ecology Letters

(3) Otto et al. 2007, Nature

(4) Digel et al. 2011, Oikos

(5) Brose et al. 2006, Ecology Letters

(6) Rall et al. 2008, Oikos

(7) Berlow et al. 2008, PNAS

(8) Petchey et al. 2008 PNAS

(9) Brose 2008, Proc. Royal Soc. London B

(10) Brose 2010, Functional Ecology

Effects of body sizes on physiological rates and interaction strengths (functional responses)

Body masses of organisms and envirnmental temperature determine their physiological rates of respiration¹, production, growth amongst others and also the strength of feeding interactions² between predator-prey pairs. In laboratory projects, we address how consumer and resource body sizes^2-5, environmental temperature^6-8, habitat structure⁹, prey diversity¹⁰ and predator abundance⁸ affect respiration and interaction strengths.

References for further reading (see publications section):

(1) Ehnes et al. 2011, Ecology Letters

(2) Brose et al. 2008, Journal of Animal Ecology

(3) Vucic-Pestic et al. 2010, Journal of Animal Ecology

(4) Rall et al. 2011, Oikos

(5) Brose 2010, Functional Ecology

(6) Rall et al. 2010, Global Change Biology

(7) Vucic-Pestic et al. 2011, Global Change Biology

(8) Lang et al. in press, Journal of Animal Ecology

(9) Vucic-Pestic et al. 2010, Pedobiologia

(10) Kalinkat et al. 2011, Plos One

Predicting the consequences of species loss in complex networks

One of the greatest challenges in environmental biology is predicting how the loss of one species impacts the remaining community and the ecosystem goods and services it provides. In even the simplest natural ecosystems, all species are connected by complex webs of interdependence, in large part created by their universal need for energy in the form of food. Our lab is taking a variety of approaches (computer simulations, statistical analyses of empirical data, and manipulative experiments) to help increase our ability to predict the broader consequences of biodiversity loss in complex ecological networks^1-7.

References for further reading (see publications section):

(1) Brose et al. 2005, Ecology Letters

(2) Otto et al. 2008, Ecology

(3) Berlow et al. 2009, PNAS

(4) Brose 2011, Basic and Applied Ecology

(5) Curtsdotter et al. 2011, Basic and Applied Ecology

(6) Riede et al. 2011, Basic and Applied Ecology

(7) Binzer et al. 2011, Basic and Applied Ecology

Effects of global warming and nutrient enrichment on complex networks

Anthropogenic increases of the global temperature and enrichment cause an urgent need for a detailed understanding of their impacts on natural communities. Mathematical models enabled a mechanistic understanding how nutrient enrichment increases the biomasses of species but eventually leads to extinctions ("paradox of enrichment")¹. Ongoing projects in our lab address how enrichment and increases in environmental temperature influence population dynamics and the stability of complex food webs^2-5.

References for further reading (see publications section):

(1) Rall et al. 2008, Oikos

(2) Brose 2008, Proceedings of the Royal Society London B

(3) Rall et al. 2010, Global Change Biology

(4) Vucic-Pestic et al. 2011 Global Change Biology

(5) Petchey et al. 2010, Philosophical Transactions of the Royal Society