Download Species-specific Feeding Patterns Of Corixids (Hemiptera: Corixidae

Species-Specific Feeding Patterns Of
Corixids (Hemiptera: Corixidae) As
Indicated By Stable Isotope Analysis
Stephen Srayko, Iain Phillips,Tim Jardine and Doug Chivers
Outline
■ Introduction
Corixid Ecology and Diet
Stable Isotope Analysis
Objectives
■ Methods
■ Results and Discussion
Species Composition
Isotopic Signatures
Source Proportion
Estimates
Trophic Position Estimates
Future Work
■ Conclusion
Introduction: Corixid Ecology and Diet
■ Diverse family of aquatic Hemiptera
>130 species in North America (Brooks and Kelton, 1967)
■ Wide range of aquatic habitats (Brooks and Kelton, 1967)
■ Potential for a variety of feeding strategies
(Stonedahl and Lattin, 1986)
Male corixid foretarsi (pala)
■ Knowledge so far: observational studies, gut content analyses
Stable Isotope Analysis
δ= heavy:light isotope/standard, in ‰
■ δ13C : reflects carbon
sources at food web base
Δδ13C = 0.4 ‰ (Post, 2002)
Pelagic vs benthic δ13C
■ δ15N : can be used to
infer trophic position
Δδ15N= 3.4 ‰ (Post, 2002)
Hart and Lovvorn 2002
Objectives
■ To determine feeding patterns among different corixid species
■ Compare corixid δ13C and δ15N to primary consumer baselines:
zooplankton=pelagic sources
chironomids=benthic sources
■ δ13C: carbon source pathways
■ δ15N: trophic positions
Methods: Sample Collection
■ Study sites: wetlands near Saskatoon, Saskatchewan
Sample period: Aug 13-18, 2014
Saskatoon, SK
■ Corixids: D-net
■ Chironomids: D-net, Ekman dredge
■ Zooplankton: Wisconsin net
Methods: Sample Processing
■ Corixids: identified to species
■ Chironomids: representative samples to genus or species
■ Zooplankton: phototaxis (Burian et al. 2014)
■ All samples: frozen
■ Stable isotope sample prep: dried at >50oC for 24 hrs, ground up,
weighed and packed
Methods: Data Analysis
■ Lipid correction and extraction (Braun et al., 2014; Smyntek et al. 2007)
■ Carbon source proportions: Stable Isotope Analysis in R (SIAR)
(Parnell
et al. 2010)
■ Trophic position:
-Site specific values: SIAR source proportions, mixing model
(Post, 2002)
Δδ15N = 1.9 (Bunn et al., 2013)
■ Comparisons between species, and within species, between sites:
1-way ANOVAs
Results and Discussion: Species Id
Number Collected
350
300
250
200
150
100
50
0
■ Chironomids: Mostly Chironomus plumosus, also Glyptotendipes sp
■ Notonectids: Notonecta borealis, N. kirbyi, N. undulata
Male
Female
Isotope Values
12
Callicorixa audeni
11
Cenocorixa bifida
Cenocorixa dakotensis
10
Cymatia americana
δ15N
9
Hesperocorixa atopodonta
8
Hesperocorixa vulgaris
Sigara bicoloripennis
7
Sigara decoratella
6
Notonecta borealis
Notonecta kirbyi
5
Notonecta undulata
4
Chironomid
3
Zooplankton
-36
-34
-32
-30
δ13C
-28
■ Average isotope values from all sites ± 1SD
-26
-24
Baseline Isotope Values
12
10
y = 0.0076x2 + 0.3838x + 11.846
R² = 0.0456
δ15N
8
6
Zooplankton
4
Chironomids
2
0
-45
-40
-35
-30
δ13C
-25
-20
-15
Source Proportion Estimates
Proportion of Benthic Carbon
■ Mix of pelagic (POM), benthic (periphyton, detritus) pathways
■ More reliance on benthic (variable between sites)
■ H. atopodonta: complete pelagic reliance
1.2
1
0.8
0.6
0.4
0.2
0
Source Proportion Estimates
■ More reliance on benthic sources (variable between sites)
■ Benthic algae feeding: energy efficient, nutritious (Hecky and Hesslein, 1995; Bjorn and Winkelmann 2013)
■ Collectors: feed on benthic ooze: protozoa, metazoa, plant, animal material
(Hungerford, 1917)
■ Predatory feeding: bottom trawl (Popham et al.1984)
Trophic Position Estimates
■ Most species intermediate between primary consumer (trophic
level=2) and secondary consumer (trophic level=3) positions
4
Trophic Level
3.5
3
2.5
2
1.5
1
0.5
0
Feeding Patterns
Predation
■ Cymatia americana, Notonecta: predatory (Brooks and
Kelton, 1967; Reynolds, 1975; Popham et al., 1984)
■ Low trophic fractionation in predatory
invertebrates
-High nitrogen use efficiency (Vanderklift and Ponsard, 2003; Cremona et al.
2010)
■ Suctorial predators: low trophic fractionation
e.g. Cremona et al. 2010
δ15N values of different feeding groups:
1o Consumers= 8.31‰
Predators (all)= 9.53‰
Predators- suckers= 7.96‰
Cymatia americana pala (top)
Feeding on chironomid (bottom)
Feeding Patterns
Omnivory
■ Assimilation of algal carbon in predatory taxa (Lancaster et al., 2005)
■ Feeding plasticity: adaptation to resource availability, important in variable
habitat conditions (Bjorn and Winkelmann, 2013; Zah et al., 2001)
■ High overlap in δ15N signatures: possible lack of distinct trophic levels,
generalist feeding (Beaudouin et al., 2001)
Fry 1991
Future Work
■ Gut content analysis: gel electrophoresis (Giller, 1986)
■ Lab studies:
-Rearing study: turnover rate, effects of development, corixid specific
trophic fractionation factor (Ostrom et al. 1977; Tibbets et al. 2008; Jardine et al. 2008)
-food choice experiments (Klecka, 2014)
Conclusion
■ Corixid feeding patterns: variable within and between species
■ Mix of benthic/pelagic carbon source pathways, tending towards benthic
sources
■ Potentially high prevalence of omnivory across different species
■ Widespread presence of corixids in different aquatic habitats
possibly related to ability to utilize a variety of food resources
Thanks!
Stephen Srayko
University of Saskatchewan
[email protected]
Special thanks to:
Water Security Agency, Saskatoon
Alix Schmidt
Iona Tangri
Dale Parker
Myles Stocki