Supervising team: Jana Eccard, Niels Blaum, Christian Voigt, Florian Jeltsch
Workplace: University of Potsdam
0. Brief expected profile of PhD student
Candidates must have a completed MSc in Ecology or related fields, e.g. Behavioural Ecology. The position requires the willingness to organize and perform field work. A solid background in experimental design and statistical modelling is important, further valuable skills are scientific writing and working in a team.
1. Short Abstract
In predator-prey systems many indirect effects of predation have evolved and prey individuals may reduce predation risk by avoiding movement at dangerous times or in dangerous habitats. This in turn creates specific exploitation patterns in prey assemblies, which may affect the local as well as landscape-wide biodiversity of prey. In this project we investigate a tri-trophic interaction of a predator potentially preying on a consumer, a consumer’s resulting movement processes while foraging, and the biodiversity of plant seeds, that are the consumer’s prey. The consumer in this constellation functions both as prey for the predator and as a predator (by foraging) on its own prey, the plant seeds. In a series of experiments we will manipulate the consumer’s landscape of fear (LoF), consisting of levels and spatial distribution of perceived predation risk. We will monitor LoF effects on two cascading variables, the movement processes of the consumer, and the alpha- and beta-diversity of the plant seed community. The project will shed light on movement mediated biodiversity patterns across multiple trophic levels, with consumers as movement process links and as equalizing and stabilizing agents.
2. Background and previous work
Evolutionary adaptation to the risk of predation has shaped diverse strategies of potential prey species to reduce this risk (1), including risk allocation (2), movement time or habitat shifts (3, 4) and adjustment of movement to a landscape of fear (5, 6). In food webs with three levels a cascading, indirect effect of top-predators on the biodiversity of a consumer’s prey community has been reported (5, 6). However, information on consumer’s movement as the missing process link between a LoF on the one hand, and biodiversity in the consumer’s prey assemblage on the other hand remains to be investigated (5, 6). In this project we are using small rodents as experimental consumers. In the animal ecology group (Eccard lab) we have ample experience with experimental manipulations of risk distribution and foraging patterns (7-10), for example by removing vegetation cover at seed trays (8) or distributing predator odour (11), and the monitoring of rodent movement by small-scale automated radio telemetry (12, 13).
3. Objectives/ Aims
We want to experimentally manipulate the consumer’s perceived LoF (thus manipulating the ghost of the highest trophic level), and observe effects on two cascading target variables: i) the consumer’s movement patterns, and ii) the giving-up-diversity in the lowest trophic level, i.e. how many seeds of which species the consumer has not consumed, which allows calculating alpha- and beta diversity of prey items of the consumer. This project aims at identifying movement mechanisms that are critically linked to species richness on alpha and beta diversity level.
4. Outline work program
In a first step the doctoral student will get acquainted with the experimental system and technical challenges.
As a second step, the doctoral student will conduct a series of short (few weeks) experiments on LoF of wild rodents, where the landscape will be manipulated, artificial seed banks will be offered to obtain estimates of giving-up-biodiversity, and movement processes will be monitored via radio telemetry.
Third, the doctoral student will refine the theoretical framework of tri-trophic effects of LoF on biodiversity via movement processes and publish the obtained results.
5. Linkage to ‘BioMove’ hypotheses, objectives and concepts
This project is part of the process-to-pattern (bottom-up) cluster, investigating the mobile process link leading to the observed biodiversity patterns. We can further dwell on the function of mobile consumers as equalizing-stabilizing agents among species in the experimental seed communities they forage upon. With a fear-matrix allowing the consumer to switch easily among patches they may act as an equalizing force through seed predation, reducing large average fitness differences between individuals of competing seed species and may thereby potentially contribute to stable coexistence of plants. Further, with consumers potentially developing preferences for most easily accessible or most profitable seeds, they may act as stabilising forces allowing for “increase-when-rare’ processes of less profitable seeds in foraged locations, i.e. when local plant populations have a positive effective growth rate at a low density.
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(2) Lima SL, Bednekov PA (1999) Temporal variation in danger drives antipredatory behaviour: the predation risk allocation hypothesis. Am Nat 153:649–659
(3) Brown JS (1988) Patch use as an indicator of habitat preference, predation, risk, and competition. Behav Ecol Sociobiol 22:37–47
(4) Abramsky Z, Strauss E, Subach A, Kotler BP, Riechmann A (1996) The effect of barn owls (Tyto alba) on the activity and microhabitat
selection of Gerbillus allenbi and G. pyramidum. Oecologia 105:313–319
(5) Ripple, JW et al. (2014) Status and elogical effects of the world’s largest carnivores. Science 343:1241484
(6) Suraci, JP, Clinchy, M, Dill, LM, Roberts, D, Zanette, LY (2016) Fear of large carnivores causes a trophic cascade. Nature communications
(7) Eccard JA, Liesenjohann T (2014) The importance of predation risk and missed opportunity costs for context-dependent foraging patterns. PLoS ONE 9(5): e94107. doi:10.1371/journal.pone.0094107
(8) Eccard, J. A., Pusenius, J., Sundell, J., Halle, S., & Ylönen, H. (2008). Foraging patterns of voles at heterogeneous avian and uniform mustelid predation risk. Oecologia, 157(4), 725-734
(9) Eccard, JA, Liesenjohann, T (2008) Foraging decisions in risk-uniform landscapes. PLoS ONE 3(10): e3438.
(10) Liesenjohann,T, Eccard, JA (2008) Foraging under uniform risk from different types of predators. BMC Ecology 8:19. http://dx.doi.org/10.1186/1472-6785-8-19
(11) Eccard JA, Meißner JK, Heurich M (2015) European Roe Deer Increase Vigilance When Faced with Immediate Predation Risk by Eurasian Lynx. Ethology 121:1-11
(12) Herde et al. (2018) Animal personality affecting space use and fitness (in prep.)
(13) Schirmer et al. (2018) Effects of animal personality on movement patterns and coexistence of species (in prep.)