1. non-additive effect of predators.
(left) predator combinations may result in more
(a) or less (b) prey mortality, with a corresponding
change in decomposition. Prey behaviour (c) may
be affected independently of density (left).
(above) mean and 95% bootstrap confidence
intervals for predator non-additive effects,
calculated as mean(monoculture) - mean
(polyculture)
The effect of predator functional diversity on
ecosystem function in a bromeliad food web
A. Andrew M. MacDonald1
, Diane S. Srivastava1
and Gustavo Q. Romero2
1. Department of Zoology, University of British Columbia, BC, Canada; 2.
Main question:
How does predator
phylogenetic diversity (PD)
alter the prey community, and
in turn affect ecosystem
function?
Leptagrion
Insecta
Bilateria
Diverse predator combinations result in less mortality but not less decompositon
Methods and study system:
Bromeliads (Quesnelia arvensis) contain
a diverse community of invertebrates,
forming a mostly detritus-based food
web.
Predators in this system range from damselflies
(Odonata) in the genus Leptagrion, to fly larvae
(Diptera:Tabanidae) and leeches.
We stocked bromeliads with a standard prey
community containing all major functional
groups, forming a processing chain.
Neither the presence nor the diversity of predators affects nitrogen cycling
NMDS ordination of
surviving prey
communities. There is
little evidence for a distinct
diet difference between the
predator compinations
Predator treatments included single-species
monocultures and two-species polycultures
of increasing phylogenetic diversity
Effects on nitrogen cycling:
(above) Nitrogen cycling, measured as
the amount of N15
transferred into
bromeliad leaf tissue from labelled
leaves, differs little among treatments.
(left) there is no evidence for
nonadditive effects of predators.
L.elongatumL.androm
ache
Tabanid
Leech
Conclusions
Polycultures of predators show a negative, non-additive effect on predation when PD his high.
This is possibly due to an increase in interference or intraguild predation.
There is little evidence for predator-mediated increase in Nitrogen cycling; however
decomposition was also low in all treatments.
Thank you!
Aline Nishi, Robin LeCraw, Alathea Letaw
Paula Omena and grad students of the Romero Lab
a
b
c