Download Interactions between competition and predation shape early growth

Virginia Commonwealth University
VCU Scholars Compass
Biology Presentations
Dept. of Biology
2010
Interactions between competition and predation
shape early growth and survival of two Neotropical
hylid tadpoles [poster]
Sergio C. Gonzalez
University of Florida
Justin C. Touchon
Boston University
James R. Vonesh
Virginia Commonwealth University, [email protected]
Follow this and additional works at: http://scholarscompass.vcu.edu/biol_present
Part of the Ecology and Evolutionary Biology Commons
Downloaded from
http://scholarscompass.vcu.edu/biol_present/4
This Presentation is brought to you for free and open access by the Dept. of Biology at VCU Scholars Compass. It has been accepted for inclusion in
Biology Presentations by an authorized administrator of VCU Scholars Compass. For more information, please contact [email protected].
Interactions between competition and predation shape early
growth and survival of two N eotropical hylid tadpoles
Sergio C. Gonzalez 1 ([email protected]), Justin C. Touchon2 ([email protected]), and James R. Vonesh3 ([email protected])
lUniversity of Florida, 2Boston University & STRI, 3Virginia Commonwealth University
Introduction
No predator
The relative importance of competition and predation
in shaping communities is a long standing question
in ecology. Past studies show that competition
typically has stronger effects on growth, whereas
predator presence has stronger effects on survival.
Further, predators often modify the effects of
competitors. The interaction of these factors is
particularly important for anuran larvae; predators
typically reduce the effect of competition on growth
and the presence of alternative prey may also alter
predation on focal taxa.
1.0
C
S
-
.0 0.8
• A. cal/idryas grew faster and o. ebraccatus slower
when they co-occurred in the absence of predators.
Aga/ychnis cal/idryas
c::::::::J Oendropsophus ebraccatus
0.8
0.6
0.6
~ 0.4
0.4
• Predators substantially reduced tadpole growth,
despite more than doubling per capita food avail
ability by consuming >60% of tadpoles
0.2
• Predation erased competitive asymmetry
0.0
• Mortality of both species with the predator was
reduced by the presence of the other species
-0..
ro
t
o
0.2
~
Question: What are the independent and combined
effects of competition and predation on the survival
and growth of tadpoles of two co-occurring hylid
frogs?
0.40
0.40
(])?
+-'
-t-'
roO>
s..... C
- Agalychnis cal/idryas: large mid-water filter feeder
- Oendropsophus ebraccatus: smaller algal grazer
•
Q)
~ .~
0.30
0.30
coc
O~
s.......c
Methods
u:::: a
0)0,
(])
c
No Predator Predator
Q)
>-
.cu 0.20
-t-' ._
• 2 x 3 randomized factorial design
• predator presence or absence
• 1 Anax amazili dragonfly larva
• tadpole species composition
• 50 A. cal/idryas
} All same
• 50 O. ebraccatus
oviposition
• 25 of each species
cohort
• 1: 1 mixture of suspended and benthic food
. 6 replicates in 400 L mesocosms over 8 days
• Main and interactive effects of species identity,
species composition, and predator presence
examined using GLM (mortality) and LM (growth)
Results
• Both species had similar growth when alone
1.0
.
pecles
t
o
o0..
s.....
Predator
• We show that predator effects can dominate both
survival and growth
• These results highlight the potential importance of
predators in shaping prey populations and aquatic
food web interactions in the tropics via both direct
(]):::.-
0:::8'
0.10
0.10
Single
A-. callidryas 0 and B. ebraccatus
tadpoles at start of experiment. ' _
Conclusions & Significance
0.20
ro:!:
- c
,
• No evidence of predator preference for prey type
Mixed
Single
Mixed
Figure 1. Mortality and growth rates of Agalychnis cal/idryas and
Oendropsophus ebraccatus tadpoles in single and mixed species
treatments in the presence and absence of predaceous Anax
amazili nymphs. Inset: Final size distribution of tadpoles in
predator and no predator treatments. Mortality - Pred: P < 0.001,
Composition: P < 0.001, Spp*Pred: P < 0.001 Growth - Pred:
P < 0.001, Spp*Composition: P < 0.001, Spp*Pred: P < 0.001
Acknowledgments
We thank Karen M. Warkentin, Venetia S. Briggs, Max A. Nickerson,
Christopher M. Asquith and the 2009 Vonesh-Warkentin Gamboa, Panama
research group. The Autoridad Nacional del Ambiente de Panama gave
permission to conduct this research (Permiso SE/A-41-08). This work was
funded by a National Science Foundation (USA) Research Experience for
Undergraduates (REU) supplement to DEB-0717220 (JRV), NSF
DEB-0716923 (KMW) , the Smithsonian Tropical Research Institute, Virginia
Commonwealth University, Boston University, and the University of Florida's
University Scholars Program.
Smithsonian Tropical Research Institute